vel tech high tech dr.rangarajan dr.sakunthala engineering

Vel Tech High Tech Dr.Rangarajan Dr.Sakunthala Engineering College Department of Chemical Engineering

CH6605- Fertilizer Technology

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UNIT- I NITROGENOUS FERTILISERS

PART – A

1. What is a Fertilizer? What is the need for fertilizers? (May/June 2009)

A fertilizer may be defined as an extraneous material provided for the cultivable land in

order to supplement the nutrition the crops and trees etc. can draw from the land. It can be defined as

the quantity of additional nutrients required by a particular crop to increase its growth to the optimal

level in a given soil. Fertilizer is generally write "any material, organic or inorganic, natural or

synthetic, which supplies one or more of the chemical elements required for the plant growth".

2. Define Fertilizer Grade.

All fertilizer labels have three bold numbers. The first number is the amount of nitrogen (N), the

second number is the amount of phosphate (P2O5) and the third number is the amount of potash (K2O).

These three numbers represent the primary nutrients (nitrogen (N) - phosphorus (P) - potassium (K)).

This label, known as the fertilizer grade, is a national standard. A bag of 10-10-10 fertilizer contains 10

percent nitrogen, 10 percent phosphate and 10 percent potash.

3. What is Straight Fertilizer?

Straight fertilizer is a fertilizer that contribute single nutrient to the crops. Straight fertilizers

are those which supply only one primary plant nutrient, namely nitrogen or phosphorus or

potassium. eg. Urea, ammonium sulphate, potassium chloride and potassium sulphate.

4. State the function of nitrogen in nitrogenous fertilizer. (Nov/Dec 2011)

Nitrogen supplied as nitrate ion or ammonium salt is one of the important constituent for

synthesis of amino acids which are then converted into proteins and enzymes. Proteins thus formed

make part of the protoplasm, while enzymes act as catalysts for various reactions taking place in the

plants. Nitrogen is also a special constituent of the chlorophyll, without which photosynthesis is not

possible. Nitrogen makes up 16-18% of the plant protein and constitutes 1-4% of the dry weight of

plants and is required in large amounts of any of the plant nutrients.

Sources of nitrogen

Atmosphere

Organic nitrogen compounds formed in the soil by recurring natural processes

Fertilizers

5. What is the need for fertilizers?

It can be defined as the quantity of additional nutrients required by a particular crop to increase

its growth to the optimal level in a given soil. Fertilizing the land is essential due to following reason

Provide nutrient essential for growth and better yield.

Maintain the pH of the soil in the vicinity of 7-8 to facilitate optimum growth

Provide food supplement to the plants

6. What are nitrogenous fertilizers produced from the ammonia? (Apr/May 2015)

Ammonium sulphate, ammonium nitrate, urea, calcium ammonium nitrate and ammonium

chloride

7. What are the Chief requisites of a fertilizer? State them (April/May 2011) (May/June 2013)

• Must be soluble in water

• Should be cheap

• Should maintain the pH of the soil in

the vicinity of 7 to 8.

• The element present in the

compound must be easily

available to the plant

• Should not be toxic to plant

• Should be stable for long

time



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8. How are fertilizers classified? (April/May 2011)

Based on their chemical composition

Based on the source

Based on their nutrient content

Based on the physical state

Organic products Mineral fertilizers Synthetic soil conditioners

a) Natural organic fertilizers Animal matter: Farm yard manures: Guano Plant matter:

Micronutrient fertilizers: Straight fertilizers: Compound fertilizer: (complex or multi-nutrient fertilizers)

Solid fertilizer: Liquid fertilizers:

b) Natural inorganic fertilizers Rock Phosphates: Chile Saltpetre: Potassium Salts:

c) Artificial fertilizers Phosphorus fertilizer Nitrogenous fertilizer Potassium fertilizer

9. Define Fertilizer ratio

Commercial fertilizer has specific ratio of nutrients, or fertilizer ratio or plant food ratio.

It is the ratio of the number of fertilizer units in a given mass of fertilizer expressed in the order N,

P and K. Thus, it is the ratio of two or more nutrient percentages to one another. For instance, a

fertilizer with 5-10-15 grade has 1-2-3 ratio, whereas a fertilizer with 10-20-20 grade has 1-2-2

ratio. Fertilizer ratio is also defined as the relative proportion of primary nutrients in a fertilizer

grade divided by the highest common denominator for the grade. For example, the grade 16-12-20

has a ratio of 4-3-5 of N, P and K, respectively.

10. Write the benefits of a fertilizer.

The fertilizer benefits to the human environment are as follows

a) Farming efficiency improvement

b) Improvement of soil quality with adequate fertilization

c) Crop quality improvement d) Water conservation

11. Classification of Elements Essential for Plant Growth

• Major elements - (Available from air or water) Carbon, Hydrogen, Oxygen

(Macronutrients)

- Primary nutrients Nitrogen Phosphorus, Potassium

- Secondary nutrients Calcium Magnesium, Sulfur

• Minor elements (Micronutrients)

Boron, Chlorine, Copper, Iron, Manganese, Molybdenum, Zinc



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12. Differentiate between primary nutrients and secondary nutrients. (April/May 2008)

Primary nutrients

Nitrogen, phosphorus and potassium are consumed in large amounts by the plants for their

growth and so these are called primary nutrients.

Secondary nutrient

Calcium, magnesium and sulfur which occur to a limited extent in all soils, are called

secondary nutrients.

13. Distinguish between direct and indirect fertilizers. (April/May2010), (Nov/Dec 2011)

Direct Fertilizers

A material that can serve the purpose of providing nutrition to plants, trees and crops by

easily getting assimilated by the land, can be termed as direct fertilizer. For Sample super

phosphates, nitrates and ammonium compounds.

Indirect Fertilizers

These fertilizers are used to improve the mechanical, chemical and biological properties of

the soil. Fertilizers used to change the reaction of the soil solution, to improve the physical

properties of the soil, and to activate its useful microflora. For example dolomite, limestones are

used to reduce the soil acidities and gypsum used to improve the properties of the soil with a high

salt content.

14. State the important characteristics of nitrogenous fertilizers. (May/June 2013)

They are readily soluble in water and easily decomposed by micro organisms in the soil. In

the soil, they are quickly changed into ammonical and then nitrate form and becomes available to

the plants. Main amide fertilizers used in our country Urea -46%, Calcium cynamid -21%N. 15. What is organic Manure?

Organic waste matter- food waste, deceased animal parts, animal excreta etc. can be

composed together with mud and slime to form a good natural fertilizer material for crops.

Such material is called organic manure. Before the invention of chemical Fertilizers farmers in our

country were dependent on organic manure only.

16. What are the Advantages of Organic Fertilizer?

• Improve the structure of

the soil

• Retain soil moisture

• Release nitrogen slowly

and consistently.

• Mobilize existing soil

nutrients.

• Do not burn the plants like

some chemical fertilizers

• Less subject to leaching

17. How are urea prills made?

Solid urea is the largest nitrogen fertilizer product which is produced in two forms of

granules and prills. It is concluded that the urea prilling process is the finishing process

which produces the weaker and the more uniform size and strength of the particles than the

fluidized-bed granulation process.

18. Why is urea prilled? (April 2016)

A prill is a small aggregate or globule of a material, most often a dry sphere, formed from a

melted liquid. Prilled is a term used in mining and manufacturing to refer to a product that has

been pelletized. The pellets are a neater, simpler form for handling, with reduced dust.

The material to be prilled must be in a solid state at room temperature and a low-viscosity

liquid when melted. Prills are formed by allowing drops of the melted prill substance to congeal or

freeze in mid-air after being dripped from the top of a tall prilling tower.

Certain agrochemicals such as urea are often supplied in prilled form. Fertilizers (ammonium

nitrate, urea, NPK fertilizer) and some detergent powders are commonly manufactured as prills.

https://en.wikipedia.org/wiki/Mining

https://en.wikipedia.org/wiki/Manufacturing

https://en.wikipedia.org/wiki/Pelletizing

https://en.wikipedia.org/wiki/Prilling_tower

https://en.wikipedia.org/wiki/Agrochemicals

https://en.wikipedia.org/wiki/Urea

https://en.wikipedia.org/wiki/Ammonium_nitrate



https://en.wikipedia.org/wiki/Fertilizer

https://en.wikipedia.org/wiki/Detergent_powder



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20. What is biuret and what is its fertilizer value? (April 2016)

Biuret is a chemical compound with the chemical formula C2H5N3O2. It is also known

as carbamylurea. It is the result of condensation of two molecules of urea and is an impurity in

urea-based fertilizers. The parent compound can be prepared by heating urea above the melting

point at which temperature ammonia is expelled:

2 NH2CONH2 → NH2CONHCONH2 + NH3

UREA BIURET

21. How does urea act as a fertilizer? (April/May 2008)

Urea is an inexpensive form of nitrogen fertilizer with an NPK (nitrogen-phosphorus-

potassium) ratio of 46-0-0.Urea will provide the most nitrogen at the lowest cost. It is easy to store

and does not pose as a fire risk for long-term storage. Urea may be mixed with other fertilizers or

may be applied on its own. For plants that love acidic soils, urea is one of the top fertilizers for

acidifying soils. For gardeners who grow crops like corn, strawberries, blueberries and other heavy

nitrogen feeders, urea will supply immediate and powerful applications of nitrogen.

22. Illustrate the chemical reaction involved in the production of ammonium sulphate.

(Nov/Dec 2017)

Method of production

a)As by-product from caprolactam

b) Recovery from cock oven

c) Direct neutralization

2NH3 + H2SO4 (NH4)2 SO4

d) Gypsum process

23. Write the method of production for ammonium chloride with chemical reaction.

(Nov/Dec 2017)

Ammonium chloride (NH4Cl) is white crystalline salt highly soluble in water. Solutions of

ammonium chloride are mildly acidic. Ammonium chloride is used as fertilizer. Ammonium

chloride is used as a fertilizer for rice and some other crops in a limited way since; it may increase the

residual chloride content of some soils.

Ammonium chloride is manufactured by two processes

1. Direct reaction

NH3+ HCl NH4Cl

2. Duel salt process

NH3 + H2O + CO2 NH4HCO3

NH4HCO3 + NaCl NaHCO3 + NH4Cl

24. Though liquid Ammonia itself is a fertilizer yet it is not commonly used in a tropical

country like India. Why?

In a tropical country like India the temperatures are high and the soil will not retain the

Ammonia long enough for the plants to absorb the nitrogen from Ammonia. Also transportation of

anhydrous ammonia to the usage points by pipe lines will also involve complications.

https://en.wikipedia.org/wiki/Chemical_compound

https://en.wikipedia.org/wiki/Chemical_formula



https://en.wikipedia.org/wiki/Melting_point




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25. Mention the characteristics of ammonium sulphate nitrate. (May/June 2013)

Ammonium Sulphate Nitrate has a form of 2 - 5 mm large whitish till light yellow color

granules; the fertilizer has excellent physico-mechanical properties and properties for storage. The

granulation of this fertilizer ensures a quick and exact dosing. Because ASN contains high

ammonium nitrogen content it furthermore guarantees long-term and sustainable nitrogen supply,

and prevents the nitrogen from being washed out of the soil. In addition, ASN supports the

availability of secondary nutrients like manganese, iron, and boron in the soil.

PART B 1. Explain in detail about the urea manufacturing process with a neat flow sheet and

illustrate the major engineering problems involved.(Nov/Dec 2017)(Nov/Dec 2016)

Urea (NH2CONH2) or carbamide is an organic compound has two —NH2 groups joined by a

carbonyl (C=O) functional group. Urea serves an important role in the metabolism of nitrogen

containing compounds by animals and is the main nitrogen containing substance in the urine of

mammals.

Urea has the highest nitrogen content ava*ilable in a solid fertilizer (46%). It is easy to produce

as prills or granules and easily transported in bulk or bags with no explosive hazard. It dissolves

readily in water.

Raw materials NH3 and CO2

Reaction

CO2 + 2NH3 NH2COONH4 H = - 37,021 Kcal

NH2COONH4 NH2CONH2 + H2O ΔH = + 6.3 kcals

PROPERTIES

Molecular formula :

CH4N2O

Solubility :

Solubility in water,

ethanol, glycerol

Molecular weight :

60.06gm/mole

Bulk density :

673-721kg/m3

Appearance :

White granules

Melting point :

132-1350C

Odour : Odourless

Moisture :

1% by wt. (Max.)

Density : 1.32gm/ml

Angle of repose : 300

USES

• Fertilizer

• Protein food supplements for ruminant

• In melamine production

• It is an intermediate in the manufacture of

ammonium sulfamate & sulfamic acid

• Ingredient in the manufacture of resins,

plastics, adhesive, coatings

• Textiles anti-shrink agents and ion exchange

resins

Major Engineering problems

• Carbamate decomposition

and recycle

• Heat dissipation in the autoclave

(exothermic heat of reaction)

• Production of granular urea (Prilling)

(Biuret formation)

• Corrosion (carbamate highly corrosive).

Urea is always made in an ammonia plant because it produces CO2 as by product, which

can be used directly without further treatment. Two reactions are involved in the manufacture of

urea. First ammonium carbonate is formed under pressure by highly exothermic reaction between

carbon dioxide and ammonia followed by the endothermic decomposition reaction. The synthesis

is further complicated by the formation of a dimer called biuret (NH2CONHCONH2.H2O) which

must be kept low because it adversely affects the growth of some plants.



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Liquid ammonia, gaseous carbon dioxide and recycle materials charged in the heat

exchanger-reactor at the pressure of 14MPs at 170 - 1900C to form carbamate (highly corrosive).

The carbamate decomposition reaction is both slow and endothermic. The reactor must be heated

to force the reaction to proceed. CO2 is introduced at process pressure followed by stripper. All the

unreacted gases and undecomposed carbamate to be removed from the product, the urea must be

heated at lower pressure (400kPa). Evaporation and prilling or granulating produces the final

product. Overall, over 99% of both CO2 and NH3 are converted to urea, making environmental

problems to minimum.

2. Write in detail about the production of ammonium nitrate and nitro lime Nitro Chalk) with

neat flow sheet (Nov/Dec2017)(Nov/Dec 2016) (April 2016)(April/May 2015)(April/May 2011)

Ammonium Nitrate is in the first place a nitrogenous fertilizer representing more than 10%

of the total nitrogen consumption worldwide. It is more readily available to crops than urea. In the

second place, due to its powerful oxidizing properties is used with proper additives as commercial

explosive. It is applied as a straight material or in combination with calcium carbonate, limestone,

or dolomite. The combination is called calcium ammonium nitrate (CAN) or ammonium

nitrate-limestone (ANL) or various trade names and in compound fertilizers including nitro

phosphates.



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Properties

• Formula: (NH4)(NO3)

• Appearance:

white/grey crystalline

solid

• Nitrogen content of 35%

• Melting points depend on the

content of the water ( Approx

210oC

• Main Hazards: Explosive

and Oxidizer

• Density 1.725 kg /m3.

Reaction NH3 + HNO3 NH4NO3 H = – 20.6 K. Cal

The ammonia vapour is reacted with aqueous nitric acid in a stainless steel reaction vessel

with agitation. The heat of reaction causes water to boil off and the final salt solution is 75% and at

1400C. It is pumped to a vacuum evaporator to further concentrate to 95% solids. The hot liquid is

sprayed from the top of a prilling tower (60–75 m high) counter current to conditioned air flow.

The solidified spherical pellets or prills are about 1.5 mm in dia. And are screened and dried before

coating with clay. Fines and oversized material are redissolved and sent to the neutralizing reactor for

recycle. [Later development is usage of a centrifugal oil-quenching process for prill production]

The above flowsheeet depicts the process for the production of Ammonium nitrate as well as

nitrolime or nitrochalk[calcium ammonium nitrate]

https://www.google.co.in/search?q=ammonium+nitrate+formula&stick=H4sIAAAAAAAAAOPgE-LQz9U3yKs0MNZSz0620k_OSM3NLC4pqoSwkhNz4pPzcwvyS_NSrNLyi3JLcxIB4JZCATUAAAA&sa=X&ved=0ahUKEwii-Kb4ndLaAhXLMo8KHXKnB28Q6BMIkgIoADAe



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Product Handling

• Stored in bulk although in most climates this requires air-conditioned facilities

• Storage facilities have adequate ventilation with a high efficiency sprinkler system.

• Plastic-film bags or bags with plastic liners are suitable

• Important to prevent contamination with organic materials (Grease or other hydrocarbons,

chlorates, nitrates, and metal salts (Zn, Cu))which when ignited may support fire

Advantages

• It is quite hygroscopic;

• There is some risk of fire or even explosions unless suitable precautions are taken;

• It is less effective for flooded rice than urea or ammoniacal nitrozen fertilizers;

• It is more prone to leaching immediately after application than ammoniacal products.

3. How is ammonium sulphate manufactured?(May/June 2013)How is obtained from

Gypsum(May/June 2012)

Ammonium sulfate containing 21% nitrogen is another important nitrogenous fertilizer.

It is a quick-acting fertilizer. It occurs naturally as the mineral mascagnite and offers many

advantages as a fertilizer, such as low hygroscopicity, good physical properties, excellent chemical

stability, good agronomic effectiveness and long shelf life. Ammonium sulfate is an acid forming

fertilizer, and hence used in neutral or alkaline soils.

2NH4OH + H2SO4 (NH4)2SO4 + 2H2O

PROPERTIES

• Molecular formula

(NH4)2SO4

• Molecular weight

132.14gm/mole

• Solubility : Solubility in

water and insoluble in

alcohol, ether, acetone

• Appearance : Fine white

hygroscopic granules or

crystals

• % of nitrogen : 20-21%

• Angle of repose : 320

• Bulk density :

720-1040kg/m3

• Melting point : >2800C

• Specific gravity : 1.769

• Moisture: 1% wt. (Max.)

USES

• fertilizers (combination with other materials, such as urea, to make dry fertilizers)

• Good source of nitrogen for cotton, rice, wheat, barley, maize, sorghum, sugar cane and

fiber crops.

• Food additive, dough conditioner and food for yeast.

• Medical application development of vaccines. The DTaP vaccine, for example, which

protects children from diphtheria, tetanus and whooping cough, uses ammonium sulfate in

the purification process

• Used in rice and jute cultivation



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MANUFACTURE Gypsum process

Raw materials Ammonia , CO2 and Gypsum

Ammonia is manufactured by Haber process and CO2 is manufactured by heating

limestone. Ammonia is absorbed in water and carbonated at the pressure of about 2.1kg/cm2 in

towers packed with aluminum rings. Natural gypsum or anhydrite, when used, is ground so that

about 90% of the material passes through 120 mesh sieve. When the byproduct gypsum of

phosphoric acid plant is used, the impurities are removed by repulping the filter cake prior to

washing and dewatering on a drum or disc filter.

Now proper proportion of finely ground gypsum or anhydrite is fed into the aqueous

solution of ammonium carbonate in large tanks, whereby calcium carbonate is precipitated

gradually as a result of double decomposition.

Reactions of ammonium carbonate and gypsum solutions are carried out in a series of

wooden vessels or mild steel vessels having steam coils and agitators to give a total retention time

of 4 to 6 hours. CO2 and NH3 are passed until all the gypsum is converted into CaCO3. The slurry

produced is filtered and the calcium carbonate cake washed and dewatered. The solution is

evaporated and the crystals are centrifuged and dried in a rotary drier at 1200C. CaCO3 obtained as

by product is used as a raw material for the manufacture of cement.



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4.(i) “Ammonia is the basis for nitrogen fertilizer” justify this statement

(ii) What is the possible raw material for the manufacture of ammonia?

(iii) Mention the use of ammonia (April 2016)

“Ammonia is the basis for nitrogen fertilizer”

Ammonia or hydrogen nitride is one of nitrogen compounds. It is a colorless gas with a

pungent characteristic odor, which has the chemical formula - NH3. Freezing or pressurized

ammonia enters the liquid form. Ammonia is widely used in industry, and it is a key component in

the production of nitrogen fertilizers. Nitrogen is required to plants for proper growth and

development. Use of fertilizers increases the nitrogen content in the soil, enlarging the yields.

Anhydrous ammonia is used independently as a fertilizer. It is produced by liquefying a

gaseous ammonia under a high pressure. It is a liquid with a nitrogen content of 82.3%, which

makes it the most concentrated and cost-effective nitrogen fertilizer. Many types of nitrogen

fertilizers are produced from ammonia. The most important of them is urea, ammonium nitrate and

ammonium sulphate. Carbamide (urea) is produced from ammonia and carbon dioxide. It is

supplied in the form of granules and micro granules and contains 46% of nitrogen, which makes it

the most concentrated nitrogen fertilizer. Ammonium nitrate (NH4NO3) is the most common used



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universal nitrogen fertilizer containing 35% of nitrogen. It is applied as a basic fertilizer and for

feeding of plants. Ammonium sulphate contains 21% of nitrogen and up to 24% sulfur, therefore is

also the source of the sulfur nutrition. It is well absorbed, not washed from the soil and used for all

types of crops.

Possible raw material for the manufacture of ammonia

(i) Haber and Bosch Process

Raw materials: H2 from synthesis gas, N2 from synthesis gas/air liquefaction process (T = 400°C;

P = 200 atm; Iron catalyst with KOH promoter)

(ii) Modern method/ Killogg ammonia process

Raw materials: Natural gas and air

Use of ammonia

Ammonia is major raw material for fertilizer industries

• It is used during the manufacture of Nitro compounds, Fertilizers e.g. urea, ammonium

sulfate, ammonium phosphate etc.

• It is also used in manufacture of Nitric acid, Hydroxylamine, Hydrazine, Amines and

amides, and in many other organic compounds

• It is also used in heat treating, paper pulping, as explosives and refrigerants

5. How will you obtain the following? (May/June 2012)

(i) Calcium Ammonium Nitrate

(ii) Ammonium Chloride

(i) Calcium Ammonium Nitrate

Calcium ammonium nitrate (CAN) is a nitrogenous fertilizer produced by treating

ammonium nitrate solution with powdered limestone. The most common grade of CAN contains

about 21% nitrogen, corresponding to 60% ammonium nitrate.

Ammonium nitrate is first prepared by the reaction of ammonia and nitric acid. Ammonium

nitrate so obtained contains some un-reacted nitric acid which is neutralized by adding calcium

carbonate (obtained as a by-product, in the manufacturing of ammonium sulfate) on cooling grains

of calcium ammonium nitrate separates out. The granules of calcium ammonium nitrate are finally

coated with thin layer of soap stone powder, which; acts as a protective coating and prevents the

absorption of moisture during storage and transportation CO2 is obtained as a byproduct.

Raw materials

• Ammonia

• Nitric acid

• Lime stone or dolomite



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Handling and storage

CAN is better to store in air conditioned silos below 30°C. CAN is normally bagged in

polyethylene-lined jute or HDPE bags

(ii) Ammonium Chloride

Ammonium chloride (NH4Cl) is white crystalline salt highly soluble in water. Solutions

of ammonium chloride are mildly acidic. Ammonium chloride is used as fertilizer. As a fertilizer,

ammonium chloride has an advantage in that it contains 26% nitrogen, which is higher than that

found in ammonium sulfate (20.5%).


1. Direct reaction

NH3+ HCl NH4Cl




Direct reaction

Gaseous ammonia is bubbled into 30 %hydrochloric acid solution in a reactor. The reaction

is controlled by addition of water. The resulting solutions are then reacted with ammonia.

The slurry from the saturator is centrifuged and the crystals are washed with water and dried with

warm air in a manner to that used in ammonium sulfate.

Duel salt process

The most widely used process for producing ammonium chloride is the salting out process

for soda ash manufacture or modified Solvay's process. In the process, 30% solution of ammonia is

treated with carbon dioxide in a carbonating tower to form ammonium carbonate. The ammonium

bicarbonate as it is formed reacts with sodium chloride to give sodium bicarbonate and ammonium

chloride. The bicarbonate is separated by filtration, washed and calcined to produce sodium

carbonate.



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6. Explain the Methods of production of ammonium chloride

Ammonium chloride (NH4Cl) is white crystalline salt highly soluble in water. Solutions of

ammonium chloride are mildly acidic. Ammonium chloride is used as fertilizer. As a fertilizer,

ammonium chloride has an advantage in that it contains 26% nitrogen, which is higher than that

found in ammonium sulfate (20.5%).

Properties

• Molecular weight : 53.491gm/mole

• Appearance : White solid,

hygroscopic

• Density : 1.527gm/ml

• Odour : Odourless

• Melting point : 3380C(decomposes)

• Solubility : Solubility in water,

alcohol

Manufacture


1. Direct reaction

NH3+ HCl NH4Cl




Direct reaction

Gaseous ammonia is bubbled into 30 %hydrochloric acid solution in a reactor. The reaction

is controlled by addition of water. The resulting solutions are then reacted with ammonia.

The slurry from the saturator is centrifuged and the crystals are washed with water and dried with

warm air in a manner to that used in ammonium sulfate.

Duel salt process

The most widely used process for producing ammonium chloride is the salting out process

for soda ash manufacture or modified Solvay's process. In the process, 30% solution of ammonia is

treated with carbon dioxide in a carbonating tower to form ammonium carbonate. The ammonium

bicarbonate as it is formed reacts with sodium chloride to give sodium bicarbonate and ammonium

chloride. The bicarbonate is separated by filtration, washed and calcined to produce sodium

carbonate.


Crystalline ammonium chloride is free flowing and non-abrasive and does not have any

problem in handling and storage. As it is susceptible to caking at high humidity and has slightly

acidic reaction, ammonium chloride has to be bagged in HDPE or jute bags lined with

polyethylene film.

Advantages

• Its low cost, as it is often directly available as a by-product from important industries such

as the Solvay soda industry and potassium sulfate industry

• The fact that it combats certain plant diseases and prevents others

Disadvantages

• Incompatibility of Cl- ions with the physiology of many plants

• The corrosive action which it exhibits owing to the high degree of hydrolysis that it

undergoes

• Difficult to store as it has tendency to cake.



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USES

• Used as fertilizer.

• Used to produce low temperatures in cooling baths. Ammonium chloride solutions with

ammonia are used as buffer solution.

• It is an ingredient in fireworks, safety matches and contact explosives.

• Used in a ~5% aqueous solution to work on oil wells with clay swelling problems.

• It is also used as electrolyte in zinc carbon batteries.

• Uses in hair shampoo, in the glue that bonds plywood, and in cleaning products. In hair

shampoo, it is used as a thickening agent in ammonium based surfactant systems, such as

ammonium lauryl sulfate.

• Used in the textile and leather industry in dyeing, tanning, textile printing and to luster

cotton

• It is used as food additive.



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7. Explain the Methods of production of calcium ammonium nitrate

Calcium ammonium nitrate (CAN) is a nitrogenous fertilizer produced by treating

ammonium nitrate solution with powdered limestone. The most common grade of CAN contains

about 21% nitrogen, corresponding to 60% ammonium nitrate.

Ammonium nitrate is first prepared by the reaction of ammonia and nitric acid. Ammonium

nitrate so obtained contains some un-reacted nitric acid which is neutralized by adding calcium

carbonate (obtained as a by-product, in the manufacturing of ammonium sulfate) on cooling grains

of calcium ammonium nitrate separates out. The granules of calcium ammonium nitrate are finally

coated with thin layer of soap stone powder, which; acts as a protective coating and prevents the

absorption of moisture during storage and transportation CO2 is obtained as a byproduct.

Raw materials

Ammonia

Nitric acid

Lime stone or dolomite

Properties

Molecular formula:

5Ca(NO3)2.NH4NO3.10H2O

Molecular weight : 1080.71gm/mole

Appearance : White granular

Odour : Odourless

Melting point :1690C (approximately)

Density : 1.725gm/ml (200C)

Solubility : Solubility in water

Uses

• CAN is a valuable source of nitrogen. As a fertilizer it can be applied for all types of soil

and all plants.

• It is a nitrogen fertilizer supplying nutritive elements (N as NH4+ and NO3-, Mg and Ca as

carbonates). It is suitable for blending with other granulated fertilizers

• Commonly used on fruit, process and vegetable crops

Manufacture

CAN is produced by mixing quickly concentrated ammonium nitrate solution with ground

or powdered calcitic or dolomitic limestone. Both prilling and granulation technologies are used to

produce CAN.

Prilling process

Ammonium nitrate solution is premixed with ground limestone just before prilling. Prill towers of

30 to 50m height are employed. 1 to 3 % China clay, kieselghur or calcined fuller's earth is used to

condition the prilled CAN. The mean particle size of CAN formed is 2 to 2.5 mm.



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Granulation process

The various methods used for granulation are

• Pug mill process

• Drum process

• Cold spherodizer process

• Fluid bed process

Calcium ammonium nitrate is produced by granulating concentrated ammonium nitrate

solution with pulverized limestone or dolomite in a granulator. Ammonium nitrate solution is

prepared by reacting preheated ammonia with nitric acid in a neutralizer. Ammonia is preheated to

850C by vapours from the neutralizer which also preheats nitric acid to about 650C. Ammonium

nitrate liquor of 82-83% concentration which is produced in the neutralizer is concentrated to 92-

94% in a vacuum concentrator heated with steam and stored in a tank.

Concentrated ammonium nitrate is pumped and sprayed into the granulator which is fed

with weighed quantity of limestone powder and recycle fines from the screens. The hot granules

are dried in a rotary drier by hot air.

Dried hot granules are screened and fines and oversize recycled. Granules of proper size

are cooled in a rotary cooler by air and coated with soapstone dust in a coating drum. The final

product is sent to storage.



17 | P a g e



18 | P a g e

UNIT: II PHOSPHATIC FERTILIZERS

PART-A

1. Write the chemical reaction involved in the production of sulphuric acid. (Nov/Dec 2017)

In the first step, sulfur is burned to produce sulfur dioxideThis is then oxidized to sulfur

trioxide using oxygen in the presence of a vanadium (V) oxide catalyst. This reaction is

reversible and the formation of the sulfur trioxide is exothermic.(in presence of V2O5)The sulfur

trioxide is absorbed into 97–98% H2SO4 to form oleum (H2S2O7), also known as fuming sulfuric

acid. The oleum is then diluted with water to form concentrated sulfuric acid.

S (s) + O2 (g) → SO2 (g).

2 SO2 (g) + O2 (g) ⇌ 2 SO3 (g)

H2SO4 (l) + SO3 (g)→ H2S2O7 (l)

H2S2O7 (l) + H2O (l) → 2 H2SO4 (l)

SO3 (g) + H2O (l) → H2SO4 (l) (Highly exothermic nature reaction forms a corrosive aerosol

that is very difficult to separate, instead of a liquid.

2.How do you store phosphoric acid?

Phosphoric acid is most commonly stored in rubber-lined steel tanks, although stainless

steel, polyester and polyethylene-lined concrete are also used. The types of rubber linings used

include neoprene, butyl and natural rubber. Heating and insulation are not required in storage or

during shipment since the impurities in wet-process acid promote supercooling and reduce the

tendency for crystallisation.

3. Write the raw materials used for phosphatic fertilizers.(Nov/Dec 2016)(April/May 2018)

Bones used to be the principal natural source of phosphorus but today phosphatic ores

(Phosphate rock of Igneous or Sedimentary) mined in various parts of the world.

4.Give the chemical composition of a) Galena. b) Pyrites. (May/June 2013) (April 2016)

a) Galena is a lead sulfide mineral with a chemical composition of PbS. It has a distinct silver

color and a bright metallic luster.

Galena - Lead-86.60 % Pb, Sulfur-13.40 % S

b) The mineral pyrite, or iron pyrite, also known as fool's gold, is an iron sulfide with the

chemical formula FeS2. This mineral's metallic luster and pale brass-yellow hue give it a

superficial resemblance to gold; hence the well-known nickname of fool's gold. Pyrite is the most

common of the sulfide minerals. Pyrites - Iron: 46.55 % Fe; Sulfur: 53.45 % S

5. What is phosphate rock? (April/May2010), (May/June 2009), (May/June 2012), (May/June

2013) (April 2014) (April 2016)

Phosphate rock (PR) is a general term that describes naturally occurring mineral

assemblages containing a high concentration of phosphate minerals. The phosphate content of

phosphorite is at least 15 to 20%, which is a large enrichment over the typical sedimentary rock

content of less than 0.2% Phosphate ores are of two major geological origins:-

– Igneous as found in Kola, South Africa, Brazil, etc.

– Sedimentary as found in Morocco, Algeria, Jordan U.S.A., etc

The phosphate minerals in both types of ore are of the apatite group, of which the most commonly

encountered variants are:-

– Fluorapatite Ca10(PO4)6(F,OH)2

– Francolite Ca10(PO4)6–x(CO3)x(F,OH)2+x . Fluorapatite predominates in igneous

phosphate rocks and francolite predominates in sedimentary phosphate rocks

https://en.wikipedia.org/wiki/Vanadium(V)_oxide

https://en.wikipedia.org/wiki/Catalyst

https://en.wikipedia.org/wiki/Oleum

https://en.wikipedia.org/wiki/Exothermic_reaction

https://en.wikipedia.org/wiki/Chemical_reaction

https://en.wikipedia.org/wiki/Sulfide_mineral



19 | P a g e

6. What are the uses of phosphoric acid? (April/May 2015)

• Used as an external standard for NMR and HPLC

• Used in many teeth whiteners to eliminate plaque

• As a cleaner by construction trades to remove mineral deposits, cementitioussmears,

and hard water stains.

• As a pH adjuster in cosmetics and skin-care products.

• As a dispersing agent in detergents and leather treatment.

• Also, used as an electrolyte in copper electro polishing for burr removal and circuit

board planarization.

7. What are the characteristics of single super phosphate?(April/May 2015)

SSP [Ca(H2SO4)2] can be granulated or in a form of powder, white to grey(sometimes dark

gray to black). It is a quickly acting phosphorous fertilizer(90% soluble in water). It contains,

depending on producer,18, 5-20% phosphorous(P2O5). It can also contan other elements requires

by plants like e.g.sulphur or calcium. It is a multi nutrient fertilizer containing phosphorus (14.5

%), Sulphur (11%) and Calcium (21 %).

8. Give the composition of a) Chile saltpotre b)Rock phosphate(April/May2011)(May/June

2013) (Nov/Dec 2011)

Chile saltpetre or Peru saltpeter is sodium nitrate (NaNO3), a deliquescent crystalline

sodium salt that is found chiefly in northern Chile (large deposits of this salt can be found

in Chile). It is a readily available source of the nitrate anion (NO3−), which is useful in several

reactions carried out on industrial scales for the production of fertilizers, food preservatives and

solid rocket propellant. The mineral form is also known as nitratine, nitratite or soda niter.

HNO3 + NaOH → NaNO3 + H2O

Rock phosphate:

Total Phosphate - 32.0 - 35.0%

Calcium Oxide - 48.0 - 52.0%

Moisture - 1.5% Max

Silica - 2.5 - 5.0%

Fluoride - 4.0% Max

Sulfate - 0.7 - 1.9%

Iron -1.0% Max

Aluminium - 2.0% Max

Soluble Chloride - 0.05% Max

Potassium Oxide - 0.3% Max

Magnesium Oxide - 0.5% Max

9. What is triple super phosphate?(April/May 2008)

Triple superphosphate (TSP- concentrated superphosphate) was one of the first high-analysis

phosphorus (P) fertilizers is more concentrated fertilizer(concentrated superphosphate than

ordinary superphosphate, containing from 44 to 51% of available P2O5 or nearly three times the

amount in the regular superphosphate. it is known as calcium dihydrogen phosphate and as

monocalcium phosphate, [Ca(H2PO4)2 .H2O].

CaF2 + 3Ca3(PO4)2 + 14H3PO4 10Ca(H2PO4)2 + 2HF

10. What are pyrites? Mention its composition. (April/May2010)

The mineral pyrite, or iron pyrite, also known as fool's gold, is an iron sulfide with the

chemical formula FeS2. Pyrite is the most common of the sulfide minerals. The name pyrite is

derived from the Greek (pyritēs), "of fire" or "in fire",in turn from, "fire" A shiny yellow mineral

consisting of iron disulphide and typically occurring as intersecting cubic crystals.

Iron: 46.55 % Fe; Sulfur: 53.45 % S.

https://www.britannica.com/science/nitrate

https://www.britannica.com/science/salt

https://www.britannica.com/place/Chile

https://en.wikipedia.org/wiki/Chile


https://en.wikipedia.org/wiki/Greek_language



20 | P a g e

11. What are thermal phosphate?(May/June 2012)(Nov/Dec 2011)

Thermal treatment of PR includes three types of processes: calcination, sintering and fusion.

Calcination is a process that breaks down carbonates and drives off CO2. No entry of oxygen is

required for this process. Sintering is agglomeration of small particles to form larger ones without

reaching the melting point. Fusion is heating minerals, ores, concentrates and other inorganic

matter above the melting point. The best-known thermal phosphates are

• Rhenania phosphates and

• Fused Magnesium Phosphates (FMP).

12. Mention the product and byproduct obtained from phosphate rock (April 2014)

Process Main product and derivative By-Product

Acidulation

Superphosphate, Triple Superphosphate,

mono and Di ammonium phosphate,

Mono potassium phosphate

Fluorine compound, vanadium

and uranium

Electric furnace

reduction

Phosphorous, Phosphoric acid, Triple

Superphosphate,

Fluorine compound, Carbon

monoxide and ferro

phosphorous

Calcium metaphosphate Calcium metaphosphate Fluorine compound

Calcination or

Defluorination Defluorinated phosphate Fluorine compound

13. What is copper Pyrite? (April/may 2011)

Copper Pyrite or chalcopyrite is a copper iron sulfide (made up of copper and iron)

mineral that crystallizes in the tetragonal system. It has the chemical formula CuFeS2. It has

a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is

diagnostic as green tinged black. These ores are found in Chile, Peru, Mexico, Europe, South

Africa, several USA sites and many others around the world.

On exposure to air, chalcopyrite oxidises to a variety of oxides, hydroxides and sulfates.

Associated copper minerals include the sulfides bornite (Cu5FeS4), chalcocite (Cu2S),

covellite (CuS), digenite (Cu9S5); carbonates such as malachite and azurite, and rarely oxides

such as cuprite (Cu2O).

14. Whate is meant by phosphate fixation? (May/June 2012) (April 2014)

Phosphate fixation is a process by which ionic forms of phosphorus are made unavailable to

plants by precipitation with Fe, Al and Mn (case in acidic soils) or by Ca compounds (in alkaline

soils). At intermediate pH, phosphates tend to bound with clay minerals. Phosphate fixation is

defined as the decrease in solubility undergone by phosphates added to soils does not necessarily

imply that the availability of the fixed phosphate is low.

15. What is bone-meal? Give it composition. (Nov/Dec 2011)

Bone meal is a mixture of finely and coarsely ground animal bones and slaughter-house

waste products. It is used as an organic fertilizer for plants and as a nutritional supplement for

animals. As a slow-release fertilizer, bone meal is primarily used as a source of phosphorus. Finely

ground bone meal may provide a quicker release of nutrients than the coarser ground version of

bone meal.

The nutrients typically present in bonemeal include the minerals calcium, phosphorus,

iron, magnesium and zinc , as well as traces of other elements.

https://en.wikipedia.org/wiki/Copper

https://en.wikipedia.org/wiki/Iron



https://en.wikipedia.org/wiki/Tetragonal


https://en.wikipedia.org/wiki/Brass

https://en.wikipedia.org/wiki/Mohs_hardness_scale

https://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness

https://en.wikipedia.org/wiki/Bornite

https://en.wikipedia.org/wiki/Chalcocite

https://en.wikipedia.org/wiki/Covellite

https://en.wikipedia.org/wiki/Digenite

https://en.wikipedia.org/wiki/Malachite

https://en.wikipedia.org/wiki/Azurite

https://en.wikipedia.org/wiki/Cuprite



21 | P a g e

16. Why we need thermal treated phiosphate?

Phosphate rocks contain 1-4% fluorine which forms stable fluorapatite. In order to produce

soluble phosphates by thermal processes, fluorine in the phosphate rock must be substantially

removed or converted to other forms so that fluorapatite is decomposed. Thermal phosphates may

be divided into fused or calcined phosphates. Both are insoluble in water and soluble in weak acids

17. Give the composition of commercial superphosphate (May/June 2009)

Superphosphate [Ca(H2PO4)2], is a compound produced by treating rock phosphate with

sulfuric acid or phosphoric acid, or a mixture of the two. It is the principal carrier of phosphate,

the form of phosphorus usable by plants, and is one of the world's most important fertilizers.

Ordinary superphosphatecontains about 20% available phosphate; double super phosphate

(also called treble superphosphate) contains 40%–50% available phosphate. Ordinary super

phosphate is a gray powder that is virtually noncaking and of average drill ability;

in fertilizer it provides 14–19 percent P2O5 that is available to plants.

18. What does Rock phosphate contain mainly?

Rock Phosphate mainly contains Calcium Phosphate [Ca3(PO4)2]and Calcium fluoride[CaF2] in

minor quantities.(fluoropatite)

19. What are the uses of TSP?

• TSP can be used in wastewater treatment to reduce lead levels

• As a low cost source of phosphorus, TSP is the main substitute for single superphosphate in

cropping blends.

• It is used mainly in blends with DAP and MAP

• Source of phosphorus in situations where no nitrogen is required e.g. good fallow after

clover dominant pasture.

• In horticultural blends where the phosphorus content needs boosting

20. Write the method of production of phosphoric acid?

The modern manufacturing methods of phosphoric acid are following:

• Using phosphate rock and blast furnace

• Using phosphate rock and electric furnace

• Oxidation and hydration of phosphorous

• Wet process or from sulfuric acid and phosphate rock

21. What are the various methods available for the production of sulphuric acid? (April/May

2018)

Sulfuric acid (H2SO4) is a highly corrosive strong mineral acid. It is a colorless to slightly

yellow viscous liquid which is soluble in water at all concentrations. Sulfuric acid was called "oil

of vitriol" by Medieval.

The Industrial manufacture of sulfuric acid is done mainly by two processes

• The Lead Chamber process

• The Contact process

22. Write the role of phosphorous in the plant growth.

It is required in much lesser amounts than nitrogen. Most soils contain phosphate in the

form of complex calcium phosphate, aluminium and iron complexes and organic compounds.

Such sources are insoluble and so the plants can make very little use of them.Phosphates are

involved in the respiratory and photosynthetic processes which provide energy in some of the

plants metabolic processes without which the plant could not live. The need of phosphorus is

also necessary for the health of the plant as it is constituent of nucleic acids, phytins and



22 | P a g e

phospholipids. It is also found in seeds and fruits. The phosphorus has also been found to

contribute to the formation of the reproductive parts in the early life of the plant.

22. Write the properties of triple super phosphate.

• Molecular formula : Triple

superphosphate


• Appearance : White or gray granules

• Solubility : water soluble


• pH : 2.5-3.0 (aqueous solution)

• P2O5 (water soluble) : 42.5% minimum

• Free phosphoric acid : 3% by wt. (Max.)


• Bulk density : 800-881kg/m3

• Moisture : 12.0% by wt. (Max.)

PART B

1. Discuss briefly the production of phosphoric acid by electric furnace method with neat flow

sheet and also write the major engineering problems involved. (April/May 2018)(Nov/Dec 2017)

Phosphoric acid (H3PO4), also known as orthophosphoric acid or phosphoric (V) acid, is a

mineral (inorganic) acid. Orthophosphoric acid molecules can combine with themselves to form a

variety of compounds which are also referred to as phosphoric acids.

MANUFACTURE

The modern manufacturing methods of phosphoric acid are following:

1. Using phosphate rock and blast furnace

2. Using phosphate rock and electric furnace

3. Oxidation and hydration of phosphorous

4. Wet process or from sulfuric acid and phosphate rock

ELECTRIC FURNACE METHOD

Raw materials

• Phosphate rock

• Sand (silica)

• Coke breeze

• Caron electrode

• Air

PROPERTIES

• Molecular formula : H3PO4


• Appearance : White solid or colourless

viscous liquid above 420C

• Boiling point : 1580C (decompose)

• Viscosity : 147cP (100%)

• Melting point : 42.350C (anhydrous)

29.320C (hemihydrate)

• Density : 1.885gm/mL (liquid)

1.685gm/mL (85% solution)

2.030gm/mL (crystal at 250C)

• Solubility : Soluble in water



23 | P a g e

The phosphate rock is reduced to elemental phosphorous by the action of coke and heat in the

presence of sand in electric arc furnace subsequent oxidation of phosphorous gives phosphorous

pentoxide which on hydration gives the product phosphoric acid. Phosphate rock after proper grinding

and primary purification is taken into sintering oven where it is nodulized and granulized so that fast

oxidation of the separated phosphorous takes place. Temperature of 10950C is maintained in electric

furnace so that maximum amount of elemental phosphorous extracted out and oxidation takes place.

Since fluoride of phosphorous and calcium are the common impurity which reacts with sand giving

flourosilicates as the slag.

The gases from the furnace, phosphorous and carbon monoxide are removed by the suction process

and the oxidation product P2O5 is taken into hydration column which gives P2O5 to H3PO4 at about

850C. Purification of phosphoric acid is carried out by H2S to remove Arsenic, H2SO4 to remove calcium

salts and Silica to remove fluorides. All the byproducts are removed before concentrating the acid and

filtering it as final product. The advantage of the electric furnace process lies in its ability to use a low-

grade phosphate rock provided the major impurity is silica.

USES




24 | P a g e


• As a cleaner by construction trades to remove mineral deposits, cementitioussmears, and

hard water stains.



• Also, used as an electrolyte in copper electro polishing for burr removal and circuit board

planarization.

Major engineering Problems

• Selection of phosphate rock- plants have extra capacity for grinding, filtration and slurry

handling systems to take care of variation in the rock composition. The plant is designed in

such a way that can be used for blend of rocks from different sources.

• Grinding of rock materials- Wet or dry grinding of Phosphate rocks is required depending

upon the raw materials. Most of the old plants use dry grinding, and a majority of the new

plants use wet grinding with a ball mill or ring roller mills having air classification. Also, it is

necessary to maintain the ratio of solids while grinding.

• Handling and storage of phosphate rock- Phosphate rock are stored in dry conditions and

protected against rain, wind and freezing weather.

• Filtration of gypsum- Filtration is carried out as efficiently and economically as possible. The

filtration rate is also affected by temperature, concentration, viscosity of the acid, the desired

recovery, the amount of vacuum, the design of the filter and insoluble impurities in the rock

like clay. The normal filtration rates reported in the production are 2 to 18 tons/m2/day.

• Purification- Phosphoric acid which is intended for use in fertilizers does not require any

purification but for chemical and food products it must be purified.

• Sludge disposal- The sludge usually contains gypsum, fluosilicates, iron and phosphate

compounds.

2. Explain in detail about the production of superphosphate and triple superphosphate

fertilizer with neat flow sheet. (April/May 2018,2011)(Nov/Dec 2017)(Nov/Dec 2016)(April

2016,14)

Superphosphate [Ca(H2PO4)2], is a compound produced by treating rock phosphate with sulfuric

acid or phosphoric acid,or a mixture of the two. It is the principal carrier of phosphate,

the form of phosphorus usable by plants, and is one of the world's most important fertilizers.

Ordinary superphosphatecontains about 20% available phosphate; double super phosphate

(also called treble superphosphate) contains 40%–50% available phosphate. Ordinary super

phosphate is a gray powder that is virtually noncaking and of average drill ability;

in fertilizer it provides 14–19 percent P2O5 that is available to plants.

Triple superphosphate (TSP- concentrated superphosphate) was one of the first high-analysis

phosphorus (P) fertilizers is more concentrated fertilizer(concentrated superphosphate than ordinary

superphosphate, containing from 44 to 51% of available P2O5 or nearly three times the amount in the

regular superphosphate. it is known as calcium dihydrogen phosphate and as monocalcium phosphate,

[Ca(H2PO4)2 .H2O].

CaF2 + 3Ca3(PO4)2 + 14H3PO4 10Ca(H2PO4)2 + 2HF



25 | P a g e

The acidulation of phosphate rock to produce superphosphate! Has been the most important

method of making phosphate available for fertilizer purposes for nearly a century. The acid at 60–

700C is mixed with ground rock in a continuous mixer and passed to a continuous belt where

reaction is completed in 15–20 minutes. The product is granulated, dried and bagged. Where a

complete fertilizer is desired, excess phosphoric acid is used and neutralized with Ammonia.

Potassium slats are also added. PROPERTIES:

• The formula of triple superphosphate fertilizer, shortly called as TSP, is Ca(H2PO4)2.H2O (43-

44% P2O5). When it dissolves in water, its phosphorus is negatively charged (-1). While a part of

phosphorus content in TSP can dissolve in water, the rest is in ammonium citrate. However both of

them are in plant absorbable forms.

• The formula of normal superphosphate fertilizer, briefly referred to as NSP, is

3Ca(H2PO4)2.H2O+7CaSO4 (18-19% P2O5). The letter (N) in NSP abbreviation refers to the

word “normal” rather than nitrogen (N) as in the other nitrogenous fertilizers. So there is no

nitrogen in NSP.

Agricultural use NSP and TSP fertilizers are preferred as starter fertilizer for low pH soils in

which where tea and hazelnut are cultivated and for areas where high-quality tobacco is grown.

When phosphorus playing important role in energy metabolism of plants is deficient, while yield

decreases, quality is corrupted.



26 | P a g e

3. Explain the manufacture of phosphoric acid by wet process (April 2014)(April/May 2011)

Phosphoric acid (H3PO4), also known as orthophosphoric acid or phosphoric (V) acid, is a mineral

(inorganic) acid. Orthophosphoric acid molecules can combine with themselves to form a variety of

compounds which are also referred to as phosphoric acids.

The wet process is according to the acids (sulfuric acid, nitric acid or hydrochloric acid) used to

decompose the phosphate rock. The process using sulfuric acid is the most common among all

particularly for producing fertilizer grade phosphoric acid.

RAW MATERIALS

• Phosphate rock

• Sulfuric acid

REACTION

Ca10F2(PO4)6 + 10H2SO4 + 20H2O 10CaSO4.2H2O + 2HF + 6H3PO4

PROPERTIES

• Molecular formula : H3PO4


• Appearance : White solid or colourless

viscous liquid above 420C

• Boiling point : 1580C (decompose)

• Viscosity : 147cP (100%)

• Melting point : 42.350C (anhydrous)

29.320C (hemihydrate)

• Density : 1.885gm/mL (liquid)

1.685gm/mL (85% solution) 2.030gm/mL

(crystal at 250C)

• Solubility : Soluble in water

MANUFACTURE

Sulfuric acid on reaction with phosphate rock along with precipitation of calcium sulfate results

into the formation of phosphoric acid. The process is simple and requires grinding of phosphate rock

reacting with dilute phosphoric acid so that melt is produced which in a reactor as mixed with

concentrated sulfuric acid for 4 to 8hrs in the temperature range of 75-800C. Lot of air is required to

control the temperature. Resulting gases includes HF and P2O5 which in the absorption tower is

separated and finally treated to give fluorosilicates and dilute phosphoric acid. The main product in the

liquid form which is phosphoric acid and calcium sulfate is filtered and washed. Thus, gypsum and

phosphoric acid are separated and after minor purification the phosphoric acid is concentrated into the

evaporator.

USES



• As a cleaner by construction trades to remove mineral deposits, cementitioussmears, and

hard water stains.



• Also, used as an electrolyte in copper electro polishing for burr removal and circuit board

planarization.



27 | P a g e



28 | P a g e

4. Discuss in detail the method of production of sulphuric acid.(April/May 2015)

Sulfuric acid (H2SO4) is a highly corrosive strong mineral acid. It is a colorless to slightly

yellow viscous liquid which is soluble in water at all concentrations. It is one of the most important

heavy industrial chemicals due to it has a number of large-scale uses particularly in the phosphate

fertilizer industry. About 60 % of the sulfuric acid produced is utilized in fertilizer manufacture.

MANUFACTURE

The Industrial manufacture of sulfuric acid is done mainly by two processes

1. The Lead Chamber process

2. The Contact process

The contact process for sulfuric acid

Almost all sulfuric acid is manufactured by the contact process.

Raw Materials

• Sulfur dioxide or pyrite (FeS2)

• Air



29 | P a g e

Process Description:

Air - SO2 gas containing 7–10% SO2, 11–14% O2 is preheated by converter gas and sent to

I stage reactors of steel construction. The below reaction occurs at the Sulphur burning stage:

S (s) + O2 (g) SO2 H = – 70.9 Kcal

The first stage is high temperature (500–6000C) stage, contains 30% of total catalyst and

converts about 80% of SO2.Then the converter product is cooled by heat exchange at 3000C

[steam generation] and fed to the second stage where total yield is increased to 97% by operating at

400–4500C for favourable equilibrium. For the reaction:

SO2 (g) + ½ O2 (g) 𝐕𝟐𝐎𝟓 𝐂𝐚𝐭𝐚𝐥𝐲𝐬𝐭⇔ SO3 (g) H = – 23.0 Kcal

High yield product gases are cooled to 1500C by water and air in heat exchangers and absorbed

in Oleum fed at a rate not to allow the acid strength rise beyond 1%. Final scrubbing is done with a

lower strength (97%) acid. Oleum concentrations up to 40% can be made by tower absorption.

Higher strength Oleum up to 65% is prepared by distilling 20% Oleum.

Active catalytic agent: V2O5 (Most widely used) (Earlier Pt catalyst used but gets poisoned easily)

Promoters: Alkali / metallic compounds in trace amounts to enhance activity of catalyst.

Characteristics of Catalyst:

• Porous carrier to provide large surface area.

• Pore size controlled & Resistance to process gases at high temperature

Major Engineering Problems:

• Design of multistage Catalytic converter for exothermic reaction

• Optimization of space velocity in catalyst chambers

• Corrosion problems

• Adoption of process to various types of gas feeds

• As a result of the problems 1 and 2 above, thin catalyst beds prevail. (30–50 cm height). Yield

might drop due to longitudinal mixing if the convective gas velocity through the bed is too low.

• Removal of heat of absorption of SO3 in acid. Pumping costs and fixed costs.

5. What are thermal phosphates? How are they obtained? Mention their

characteristics.((April/may 2008)

Thermal treatment of Phosphate Rock includes three types of processes: calcination, sintering and

fusion. Calcination is a process that breaks down carbonates and drives off CO2. No entry of oxygen

is required for this process. Sintering is agglomeration of small particles to form larger ones without

reaching the melting point. Fusion is heating minerals, ores, concentrates and other inorganic matter

above the melting point. The best-known thermal phosphates are

• Rhenania phosphates and

• Fused Magnesium Phosphates (FMP).

(i) RHENANIA PHOSPHATES :

• The Rhenania process entails mixing soda ash (Na2CO3) with Phosphate Rock and silica

and subjecting it, in the presence of steam, to temperatures between 1,100 and 1,200o C.

• The resultant sodium-silicophosphates are then quenched with water and ground to a fine

powder.



30 | P a g e

Advantages:

• The Rhenania phosphates have high solubilities and are suitable for tropical soils.

• The Rhenania phosphates have been as effective or even more effective than superphosphates in

high P-sorbing soils of Brazil, in ultisols of Nigeria and high P-sorbing soils of Ethiopia and

Congo.

• Rhenania phosphates contain silicate components, which can compete with phosphate ions for

adsorptionsites.

• Additionally, these materials are alkaline in reaction and can be used as liming material in acid

soils.

Disadvantages

• Rhenania phosphates are their high costs of production, their reliance on the availability of soda

ash and large amounts of water for quenching.

(ii) FUSED MAGNESIUM PHOSPHATES (FMP) :

• Formed by mixing PR sources (usually of low citrate solubility) with Mg sources such as olivine

or serpentine.

• The mix is then fused in a furnace at about 1500-1600o C. Fused Magnesium Phosphates have

been successfully field tested in many countries including Brazil and Zambia

Disadvantages

• Large amounts of cheap electricity and large quantities of water for quenching are required.

• Both types of heat treatment result in a phosphate product that is relatively effective only in

tropical soils and both techniques can be applied at various scales.

(iii) CALCINED AL-PHOSPHATE:

In this process, Al-phosphates (crandallite, wavellite, millisite) are calcined at temperatures of

about 550o C. The calcined product contains 32% P2O5 and has a high solubility (citrate solubility

>12%).

Example of calcined Al-phosphates is Thies in Senegal. This product is marketed under the

trade name ‘Phospal,’ for animal feed use it is marketed under the trade name ‘Polyphos.’

Advantage

• Calcined Al-phosphates have shown positive results on neutral to alkaline soils.

• Since the solubilities of calcined Al-phosphates increase with increasing soil pH they have a

high potential for P-deficient high pH soils.



31 | P a g e

Part – A Unit - III POTASSIC FERTILIZERS

1. What is Sylvinite? ( Nov/Dec 2016)

Sylvinite is a sedimentary rock made of a mechanical mixture of the minerals sylvite (KCl, or

potassium chloride) and halite (NaCl, or sodium chloride). Sylvinite is the most important ore for

the production of potash in North America, Russia and the UK. Most Canadian operations mine

sylvinite with proportions of about 31% KCl and 66% NaCl with the balance being insoluble

clays, anhydrite and in some locations carnallite. Other deposits of sylvinite are in Belarus, Brazil,

France, Germany, Kazakhstan, Slovakia and Spain.

2. Write the physical and chemical properties of potassium chloride.(April/May 2018)

Physical properties:

• Kcl is an odorless

• White crystalline solid

• Density of 1.98 g/ml,

• Melting point of 770 °C

• Boiling point of 1420 °C.

Chemical properties:

• KCl is highly soluble in water (ionized into solvated K+ and Cl– ions) and polar solvents, and

insoluble in many organic solvents.

• Thus, aqueous solutions of KCl show electrical conductivity

• KCl is used to produce metallic potassium, with metallic sodium at 850 °C.

KCl + Na → NaCl + K

3. What is muriate of potash? (May/June 2012) (May/June 2013) (May/June 2014)(April

2016)

Potassium chloride (KCl) is a metal halide salt composed of potassium and chlorine. It is

odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that

cleaves easily in three directions. Potassium chloride crystals are face centered cubic. "Muriate of

potash" (MOP) is name which is occasionally association with its use as a fertilizer containing

60% plant food as K2O.

MOP, or potassium chloride, is the most commonly used potash fertilizer and can be used to

farm a variety of foods, particularly chloride-loving vegetables like sugar beets, celery, Swiss

chard and other plants that are resilient to chloride. Its chloride content can be beneficial for soils

that are low in chloride, making them more disease resistant.

4. How do you specify the composition of potassium scoenite?(April/May 2018)(Nov/Dec

2016)

• Double sulphate of potassium and magnesium

• Composed of 22.24 % potassium oxide and 90% magnesium oxide

• Widely used as potash fertilizer in Western countries

• Formulated using mixed salts that obtained by evaporation of sea bitterns.

• This chemical is ideal for crops that do not tolerate chlorine such as tobacco, potato,

sugarcane.

5. What is meant by phosphate fixation? (May/June 2012) (April 2014)






https://en.wikipedia.org/wiki/Sedimentary_rock

https://en.wikipedia.org/wiki/Sylvite

https://en.wikipedia.org/wiki/Halite

https://en.wikipedia.org/wiki/Sodium_chloride

https://en.wikipedia.org/wiki/Potash

https://en.wikipedia.org/wiki/North_America

https://en.wikipedia.org/wiki/Canadian

https://en.wikipedia.org/wiki/Anhydrite

https://en.wikipedia.org/wiki/Carnallite



32 | P a g e

6. How potassium nitrate obtained from potassium chloride?(Apr/May 2015)

The third most widely used potassium salt in agriculture is potassium nitrate.Nitric acid reacts with

potassium chloride at low temperature according to the equation;

KCL + HNO 3 KNO3 + HCL

Potassium chloride and a stoichiometric quantity of chilled 60% -70% nitric acid are fed into the

first reactor at 50 -100C. Recycled brine and solvent are added to the reactor. In the presence of the

solvent, the reaction goes almost to completion. During the process potassium nitrate crystallizes

from solution. Solid product is separated in a decanter and directed to a centrifuge and dryer. It can

be sold in the powder form or melted and prilled. The hydrochloride acid and the unreacted nitric

acid are dissolved in the liquid phase.

7. What is potassium schoenite? (Nov/Dec 2017)

Potassium Schoenite is a double Sulfate of potassium & Magnesium. It is composed of 22.24%

Potassium Oxide and 90% Magnesium Oxide. It is made by physical extraction method or by direct

removing impurities either from salt lake bittern or solid potassium –magnesium salt mine.

Potassium Schoenite is a unique source of plant nutrition since three essential nutrients are naturally

combined in to one mineral. It provides a readily available supply of Potassium, Magnesium and

Sulfur to growing plants in an ideal ratio. It has an advantage of having all nutrient contained within

a single particle, which helps provide a uniform distribution of nutrients when it is spread in the

field.

Chemical Formula: K2SO4 ∙ 2MgSO4

8. Write the importance of Sylvinite? (Nov/Dec 2017)

• Important source for the production of potash

• Sylvinite, within 30-60% of KCl, NaCl, 50-65% is a mineral comprising 9-14% MgCl 2, and

0.1 to 0.7% insoluble components. At least if used as a filler in many sectors.

• This material is sold as fertilizer ground apart after only 20-22% or 14-16% K2O special

fertilizers are prepared by the composition enriched.

9. Mention the properties of potassium sulphate. (May/June 2012)(April 2016)

• Chemical formula : K2SO4

• Appearance: Non-flammable white

crystalline salt

• Odor: Odorless

• Solubility: Slightly soluble in water and glycerol,

insoluble in acetone, alcohol, CS2

• Density: 2.66 g/cm3

• Melting point : 1,069°C (1,956 °F;

1,342 K)

• Boiling point : 1,689 °C (3,072 °F;

1,962 K)

10. What are the basic raw material for the production of potassium schoenite?

(April/May 2015)

• Potassium Chloride (KCl) • Magnesium Sulphate (MgSO4

11. Give the composition of Muriate of potash (April/May 2008)(May/June 2012)

Potassium chloride (potash) is the most common potassium source used in agriculture. Potash is

known as Muriate of Potash (MOP) with an analysis of 0-0-60. The chemical formula is KCl.

Its nutrient composition is approximately: Potassium (K): 61% K2O, Chloride (Cl): 46%.

https://en.wikipedia.org/wiki/Potash


https://en.wikipedia.org/wiki/Salt_(chemistry)

https://en.wikipedia.org/wiki/Odor

https://en.wikipedia.org/wiki/Solubility

https://en.wikipedia.org/wiki/Glycerol

https://en.wikipedia.org/wiki/Acetone

https://en.wikipedia.org/wiki/Alcohol

https://en.wikipedia.org/wiki/Carbon_disulfide

https://en.wikipedia.org/wiki/Density


https://en.wikipedia.org/wiki/Boiling_point



33 | P a g e

12. Mention the characteristics of potassium schoenite? (April/May2008)

Appearance: White crystalline powder.

Solubility :(2% Soln. at 250C) Soluble in

water. Sulfur (SO3) Content: 21-22%

pH : 6.575 SG: 2.81-2.85

Potash (K2O) Content: 22-23%

Magnesium (MgO) Content: 10-11%.

13. How potassium sulphate is produced? (April 2014)

Mannheim Process

The Mannheim process was originally developed from Sodium sulfate production by reacting

NaCl with sulfuric acid. Replacing NaCl with KCl produces potassium sulfate. The reaction is

two-stage:

• Exothermic reaction

KCl + H2SO4 KHSO4 + HCl

• Endothermic reaction

KHSO2 + KCl K2SO4 + HCl

14. Mention the important of using potassic fertilizer.(May/June 2013)

The potassium content of potassic fertilizers is usually expressed as potassium oxide (K2O)

Potash is a key irreplaceable plant nutrient. It comes to plants as K+ ion and accumulates mainly in

vacuole and cytoplasm without forming organic matter in cells.

Role of potash:

• Necessary for healthy growth of plants and cannot be replaced even by closely related

elements as sodium and lithium.

• Contributes to formation and movement of carbohydrates in plant.

• Deficiency of potassium quickly reduces the carbohydrate contents.

• The potassium content of plants ranges from about 0.5-2.5% of the dry weight.

15. Write the source of potassium sulphate.

16. Write the raw materials used for potassic fertilizer.



34 | P a g e

17. Give the classification of potassic fertilizer.

18. What are the uses of potassium chloride?

• As a fertilizer

• Used as thickeners, stabilizer, mineral salts, gelling agents and acidity regulator in food

• Used as a salt replacer in foods, for recovery of potassium in the human body.

• It's used in brewing, as a salt substitute (as salt free, sodium free, and low sodium

products), gelling agent, and in reduced sodium breads.

• Used in various pharmaceutical preparations to correct potassium deficiency.

• It used as a substitute for table salt in the diet of people with cardiovascular disorders, in

administration of the potassium ion, and as a constituent of Ringer's solution.

19. What are the properties of potassium Chloride?

• Molecular formula : KCl


• Appearance : white crystalline solid

• Odor : Odorless

• Boiling point : 14200C

• Melting point : 7700C


• Solubility : Soluble in glycerol and

water, slightly soluble in alcohol,

insoluble in ether

• Moisture: 0.5% by wt. (Max.)

20. Write storage and handling of potassium chloride

The crystalline potassium chloride is free flowing and does not normally pose any problem

in handling and storage. Potassium chloride is imported as bulk cargo and transported to NPK

fertilizer and mixing plants in open trucks or in bags.

It is stored in bulk in closed storage yards. Caking occurs in presence of impurities when

humidity is high and the mass tends to become like rock. Retrieval from such storage may pose

problems and sometimes explosives may have to be used.

21. What is Nitrate of Potash?

Potassium nitrate fertilizer (sometimes referred to as nitrate of potash or NOP) is typically

made by reacting potassium chloride (KCl) with a nitrate source. Depending on the objectives and

available resources, the nitrate may come from sodium nitrate, nitric acid, or ammonium nitrate.

The resulting KNO3 is identical regardless of the manufacturing process. Potassium nitrate is

commonly sold as a water-soluble, crystalline material primarily intended for dissolving and

application with water or in a prilled form for soil application

23. What are the methods available for the production of potassium chloride?

Potassium chloride is obtained by following methods

1. Leaching process

2. Flotation process



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24. Define handling storage and packing of Potassium Sulphate?

It is imported as bulk cargo and transported to NPK fertilizer mixing plants and dealers in

bulks or in bags.It is stored in bulk in closed storage yards. The crystalline potassium sulphate is

free flowing and does not normally pose any problem in handling and storage

24. Enlist the various potassic fertilizers.

S. No. Fertilizer % K2O

1 Potassium Chloride Or Muriate Of Potash (KCI) 48 to 62%

2 Potassium sulphate or Sulphate of potash (K2SO4) 48 to 52%

3 Potassium Magnesium sulphate (K2SO4. 2MgSO4) 22%

4 Potassium Schoenite (K2SO4.MgSO4.6H2O) 22 to 24%

PART-B

1. Explain in detail the production of potassium chloride from Sylvinite with neat flow sheet

(April/may 2018)(Nov/Dec 2017)(Nov/Dec 2016)(April 2016)(April/may 2008)

(April/may 2011)

Potassium chloride (KCl) is a metal halide salt composed of potassium and chlorine. It is odorless

and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in

three directions. Potassium chloride crystals are face centered cubic. "Muriate of potash" is name which

is occasionally association with its use as a fertilizer containing 60% plant food as K2O.

Raw Materials

• Sylvinite

• Steam

• Water

Manufacture

Potassium chloride is obtained by following methods

1. Leaching process


1. Leaching process

The solubility of potassium chloride and sodium chloride increases as the temperature increases.

Individually both are much more soluble in hot water than in cold water. But in solutions saturated with

both sodium and potassium chloride, the concentration of NaCl diminishes as temperature rises, while

the concentration of potassium chloride increases. These solubility characteristics are used to extract

potassium chloride from sylvinite. Crushed ore is mixed with sufficient quantity of recycle brine which

is already saturated with NaCl and heated almost to hilling to dissolve KCl. The KCl rich brine on

clarification and then cooling by vacuum evaporation produces KCl crystals which are centrifuged,

washed, dried and packed. The filtrate (brine) is recycled for leaching more ore.


Floatation process for extraction of potassium chloride is much cheaper than leaching process and

hence is used more extensively in the industry. In the process the ore is crushed to +10 mesh size then

washed to remove clay slimes. To render it inert to amines, washed crushed ore is treated first with

starch or mannogalactan gums and then with an amine acetate which selectively coats KCl particles.

Air is then bubbled through the slurry. The air bubbles attach themselves to the coated particles and

float them to the surface while the uncoated particles sink. The floated KCl is centrifuged, dried and

packed.



36 | P a g e

Properties

• Molecular formula : KCl


• Appearance : white crystalline solid

• Odor : Odorless

• Boiling point : 14200C



• Solubility : Soluble in glycerol and

water, slightly soluble in alcohol,

insoluble in ether

• Moisture: 0.5% by wt. (Max.)

Manufacture


The crystalline potassium chloride is free flowing and does not normally pose any problem in

handling and storage. Potassium chloride is imported as bulk cargo and transported to NPK fertilizer

and mixing plants in open trucks or in bags.

It is stored in bulk in closed storage yards. Caking occurs in presence of impurities when humidity

is high and the mass tends to become like rock. Retrieval from such storage may pose problems and

sometimes explosives may have to be used.



37 | P a g e

Uses

• As a fertilizer

• Used as thickeners, stabilizer, mineral salts, gelling agents and acidity regulator in food

• Used as a salt replacer in foods, for recovery of potassium in the human body.

• It's used in brewing, as a salt substitute (as salt free, sodium free, and low sodium

products), gelling agent, and in reduced sodium breads.

• Used in various pharmaceutical preparations to correct potassium deficiency.

• It used as a substitute for table salt in the diet of people with cardiovascular disorders, in

administration of the potassium ion, and as a constituent of Ringer's solution.

2. What is potassium Schoenite? Mention its characteristics. How is it manufactured?

(April/may 2018) (April /May 2015)(April 2014,16)(Nov/Dec 2016,17)

Potassium Schoenite is a double Sulfate of potassium & Magnesium. It is composed of 22.24%

Potassium Oxide and 90% Magnesium Oxide. It is made by physical extraction method or by direct

removing impurities either from salt lake bittern or solid potassium –magnesium salt mine.

Potassium Schoenite is a unique source of plant nutrition since three essential nutrients are

naturally combined in to one mineral. It provides a readily available supply of Potassium, Magnesium

and Sulfur to growing plants in an ideal ratio. It has an advantage of having all nutrient contained

within a single particle, which helps provide a uniform distribution of nutrients when it is spread in

the field. This chemical is ideal for crops that do not tolerate chlorine such as tobacco, potato,

sugarcane.

Properties

• Chemical Formula: K2SO4 ∙ 2MgSO4

• Appearance: White crystalline powder.

• Solubility :(2% Soln. at 250C) Soluble in

water.

• pH : 6.575 SG: 2.81-2.85

• Potash (K2O) Content: 22-23%

• Magnesium (MgO) Content: 10-11%.

• Sulfur (SO3) Content: 21-22%

Advantages

• Potassium Schoenite is readily water soluble and immediately available to plants.

• It has a neutral pH, and does not contribute to soil acidity or alkalinity.

(Dolomite - increase soil pH and Elemental Sulfur or Ammonium Sulfate which will lower the

soil pH)

• It is effective on all soil types, irrespective of pH. Usually, it is useful for all crops for faster &

healthy growth

• Resists Leaching

• Essential Chloride free

• Provides Balance Of Nutrients

• Increases Profit Per Acre

• Environmental Friendly



38 | P a g e

Manufacture:

In U.S.A. it is manufactured by mere washing of langbeinite (K2SO4. Mg SO4) to remove

the impurities and is sold under the name sulphate of potassium and magnesium. It contains 18.5%

MgO and 22.6% K2O. Since, the langbeinite is soluble in water; the washing is done very easily.

In Germany, it is prepared by dissolving MgSO4 and adding KCl to it.

3. With a neat sketch explain the method of production of potassium sulphate.

Potassium sulfate is the second largest tonnage potassium compound and it is also used

primarily as a fertilizer. The sulfate or other nonchloride forms of potassium are preferred for

certain crops that do not tolerate the chloride ion well, eg., tobacco and some ffruits and

vegetable.

Potassium sulfate (K2SO4) also called sulfate of potash, arcanite, or archaically known as

potash of sulfur is a non-flammable white crystalline salt which is soluble in water. The

chemical is commonly used in fertilizers, providing both potassium and sulfur. Potassium

sulfate contains 48 to 54% potassium (as K2O) and supplies 17-20 % of sulfate.

Source of potassium sulphate

Properties

• Chemical formula : K2SO4

• Appearance: Non-flammable white

crystalline salt

• Odor: Odorless

• Solubility: Slightly soluble in water and

glycerol, insoluble in acetone, alcohol, CS2

• Density: 2.66 g/cm3

• Melting point : 1,069°C (1,956 °F; 1,342 K)

• Boiling point : 1,689 °C (3,072 °F; 1,962 K)

Manufacture

Potassium sulfate can be manufacture by two processes

1. Mannheim process

2. Recovery from natural complex salts

Mannheim process

Raw materials

• Potassium chloride

• Sulfuric acid


https://en.wikipedia.org/wiki/Salt_(chemistry)




https://en.wikipedia.org/wiki/Acetone

https://en.wikipedia.org/wiki/Alcohol

https://en.wikipedia.org/wiki/Carbon_disulfide






39 | P a g e

Potassium chloride reacts with sulfuric acid during the slow mixing of the ingredients in the gas

heated Mannheim furnace consisting of cast iron muffle with rotating plough which helps to agitate the

mixture. Hydrochloric acid produce during the reaction is cooled and absorbed into water to produce

33% hydrochloric acid as a byproduct. The precipitated potassium sulfate fertilizer is cooled, filtered

and the lumps are crushed and granulated.

From Langbeinite

The langbeinite ore is separated from sylvite and halite by selective washing, froth flotation, or

heavy media separation. The commercial langbeinite used in the process must pulverized in ball mills,

and fine powder is mixed with a solution of the muriate of potash. The muriate of potash is dissolved

and clarified in a separate unit. The reaction in the presence of water yield potassium sulfate in a

crystalline form and brine. Crystals arecentrifuged or filtered, dried in a rotary dryer, sized and finished.

The finished methods either produce coarse material or granulated product. The mixed salts are added to

the sulfate reactor the liquor is discard as a waste.



40 | P a g e

Uses

Potassium sulfate is used as fertilizer particularly in chloride sensitive crops like tobacco, grapes

and potato which require chloride free potassium fertilizers. These three crops, being major crops,

account for about 7% of the total potash consumption. For best results, potassium sulfate should contain

at least 50 % potash by weight.

• Used as a flash reducer in artillery propellant charges.

• It reduces muzzle flash, flareback and blast overpressure

• The crude salt is also used in the manufacture of glass.



41 | P a g e

4. With a neat sketch explain the method of production of potassium nitrate.

Potassium nitrate is a chemical compound with the chemical formula KNO3. It is an ionic

salt of potassium ions K+ and nitrate ionsNO3−, and is therefore an alkali metal nitrate. It occurs in

nature as a mineral, niter. It is a source of nitrogen, which derives its name from it. Potassium

nitrate is one of several nitrogen-containing compounds collectively referred to

as saltpeter or saltpetre. Major uses of potassium nitrate are in fertilizers, tree

stump removal, rocket propellants and fireworks. It is one of the major constituents

of gunpowder (black powder) and has been used since the Middle Ages as a food preservative.

Properties

• Chemical formula :KNO3

• Appearance : white solid

• Odor : odorless

• Density : 2.109 g/cm3 (16 °C)

• Melting point :334 °C

• Boiling point : decomposes at 400 °C

• Solubility : slightly soluble in ethanol

soluble in glycerol, ammonia

Production

Potassium nitrate can be made by combining ammonium nitrate and potassium hydroxide.

NH4NO3 + KOH → NH3 + KNO3 + H2O

An alternative way of producing potassium nitrate without a by-product of ammonia is to combine

ammonium nitrate and potassium chloride, easily obtained as a sodium-free salt substitute.

NH4NO3 + KCl → NH4Cl + KNO3

Potassium nitrate can also be produced by neutralizing nitric acid with potassium hydroxide.

This reaction is highly exothermic.

KOH + HNO3 → KNO3 + H2O

On industrial scale it is prepared by the double displacement reaction between sodium nitrate and

potassium chloride.

NaNO3 + KCl → NaCl + KNO3

Uses:

• Nitric acid production

• As an oxidizer in model rocket fuel called Rocket candy.

• Food preservation

• Fertilizer

• Used in some toothpastes for sensitive teeth.

• Electrolyte in a salt bridge


Potassium chloride and a stoichiometric quantity of chilled 60% -70% nitric acid are fed

into the first reactor at 50 -100C. Recycled brine and solvent are added to the reactor. In the

presence of the solvent, the reaction goes almost to completion. During the process potassium

nitrate crystallizes from solution. Solid product is separated in a decanter and directed to a

centrifuge and dryer. It can be sold in the powder form or melted and prilled. The hydrochloride

acid and the unreacted nitric acid are dissolved in the liquid phase. Obviously both nitric acid and

https://en.wikipedia.org/wiki/Chemical_compound


https://en.wikipedia.org/wiki/Potassium

https://en.wikipedia.org/wiki/Nitrogen

https://en.wikipedia.org/wiki/Oxygen

https://en.wikipedia.org/wiki/Ionic_salt

https://en.wikipedia.org/wiki/Ionic_salt

https://en.wikipedia.org/wiki/Potassium_ion

https://en.wikipedia.org/wiki/Nitrate_ion

https://en.wikipedia.org/wiki/Alkali_metal_nitrate

https://en.wikipedia.org/wiki/Niter



https://en.wikipedia.org/wiki/Tree_stump

https://en.wikipedia.org/wiki/Tree_stump

https://en.wikipedia.org/wiki/Rocket_propellant

https://en.wikipedia.org/wiki/Firework

https://en.wikipedia.org/wiki/Gunpowder

https://en.wikipedia.org/wiki/Middle_Ages

https://en.wikipedia.org/wiki/Food_preservation







https://en.wikipedia.org/wiki/Ethanol


https://en.wikipedia.org/wiki/Ammonia


https://en.wikipedia.org/wiki/Potassium_hydroxide

https://en.wikipedia.org/wiki/Potassium_chloride

https://en.wikipedia.org/wiki/Salt_substitute

https://en.wikipedia.org/wiki/Nitric_acid

https://en.wikipedia.org/wiki/Sodium_nitrate

https://en.wikipedia.org/wiki/Rocket_candy

https://en.wikipedia.org/wiki/Toothpaste

https://en.wikipedia.org/wiki/Dentine_hypersensitivity

https://en.wikipedia.org/wiki/Electrolyte

https://en.wikipedia.org/wiki/Salt_bridge



42 | P a g e

hydrochloric acid are soluble in the solvent, but distribution coefficients differ sufficiently for the

hydrochloric acid to be removed in a countercurrent liquid extraction system by water. The

extraction is carried out in the Mixer-settler extraction system vessels the remaining nitric acid and

solvent are recycled through a refrigeration unit to the first reactor. The water is stripped from the

solvent, which is also recycled. The low concentration hydrochloride acid is evaporated in a

multiple effect evaporated to a concentrated of 22%. This acid is used in another plant to produce

phosphoric acid by a hydrochloric acid attack.



43 | P a g e



44 | P a g e

UNIT-IV COMPLEX AND NPK FERTILISERS

Part-A

1. Write the chemical reaction involved in the production of Diammonium phosphate.

(April/May 2018)(Nov/Dec 2016)

Diammonium phosphate (DAP) (chemical formula (NH4)2HPO4,

IUPAC name diammonium hydrogen phosphate) is one of a series of water-

soluble ammonium phosphate salts that can be produced when ammonia reacts

with phosphoric acid. Solid diammonium phosphate shows a dissociation pressure of

ammonia as given by the following expression and equation:

(NH4)2HPO4(s) ⇌ NH3(g) + NH4H2PO4(s) log PmmHg = −3063 / T + 175 log T + 3.3

2. Define the term complex fertilizer.

Complex fertilizers (also known as compound fertilizers) are made from mixing two or

more of macro-nutrient type fertilizers. ... Compound fertilizer can be packaged and distributed

in liquid or granular form. A numbering system is used to define the percentages of the three

essential plant nutrients.

Examples: MAP, DAP, NPK and Nitro phosphate

3. What is Di-Ammonium Phosphate? (April/May 2018)

Di-ammonium Phosphate (DAP) is a complex N-P fertilizer. Pure DAP will have the NPK

composition as 12.7: 61.7: 0, but the commercially available grades have the range of 16-18:

46-48: 0.

4. Mention the importance of NPK fertilizer as the essential plant nutrition. (April/May

2018)

All plants need nitrogen, phosphorus and potassium to grow. Without enough of any one of

these nutrients, a plant will fail.

• Nitrogen (N) – nitrogen is largely responsible for the growth of leaves on the plant.

• Phosphorus (P) – Phosphorus is largely responsible for root growth and flower and fruit

development.

• Potassium (K) – Potassium is a nutrient that helps the overall functions

of the plant performs correctly.

5. Illustrate the various grades of NPK fertilizer produced in India.(Nov/Dec

2017)(Nov/Dec 2016)

Prior to 1960/61, India produced only straight nitrogenous fertilizers

[ammonium sulphate (AS), urea, calcium ammonium nitrate (CAN), ammonium chloride and

single superphosphate (SSP)]. Currently, India produces a large number of grades of NP / NPK

complex fertilizer. These include 16–20–20, 20–20–0, 28–28–0, 15–15–15, 17–17–17,

19–19–19, 10–26–26,12–32–16, 14–28–14, 14–35–14 and 19–19–19. In addition, India

produces various grades of simple and granulated mixtures.

6. What is meant by phosphate fixation? (May/June 2012) (April 2014)






https://en.wikipedia.org/wiki/IUPAC

https://en.wikipedia.org/wiki/Water

https://en.wikipedia.org/wiki/Soluble

https://en.wikipedia.org/wiki/Ammonium_phosphate

https://en.wikipedia.org/wiki/Salts


https://en.wikipedia.org/wiki/Phosphoric_acid



45 | P a g e

7. What do you understand by NPK fertilizers?(April 2016)(May/June 2012)

NPK fertilizers are fertilizers that contain the elements nitrogen (N), phosphorus (P) and

potassium (K), each element has been found to improve the health and appearance of plants.

For example,

• Nitrogen is good at making the leaves growth

• Phosphorous improves fruit and/or flower production as well as root growth

• Potassium is great for overall plant health

Oftentimes the soil the plants are growing in lacks some of these nutrients, so by adding

them in as a fertilizer, plants do better.

8. What is meant by NPK grade (15-15-15)?

• NPK fertilizers are fertilizers that contain the elements nitrogen (N), phosphorus (P) and

potassium (K).

• All fertilizer labels have three bold numbers. The first number is the amount of nitrogen (N), the

second number is the amount of phosphate (P2O5) and the third number is the amount of potash

(K2O). These three numbers represent the primary nutrients (nitrogen (N) - phosphorus (P) -

potassium (K)). This label, known as the fertilizer grade, is a national standard.

• A bag of 15-15-15 fertilizer contains 15 percent nitrogen, 15 percent phosphate and 15 percent

potash.

9. What is composition of Nitrogen and P2O5 in Mono Ammonium

Phosphate?(April/May 2015)

10. Mention the characteristics of various grades of NPK fertilizers. (April/ May 2011)

S.No NPK fertilizer Characteristics

1 Monoammonium phosphate

• Appearance : White Powder

• Total N Content : 10.0 %

• Total P2O5 Content : 49.0 %

• Melting point: 190oC

• Formula : (NH4)H2PO4

2 Diammonium phosphate

• Appearance : Free flowing light yellow

granular

• Total N Content : 16.0 – 18.0 %

• Total P2O5 Content : 46.0 – 48.0 %


• Formula : (NH4)2HPO4

3 Urea ammonium phosphate

• Soluble in water

• 17,5 % urea (NH2)

• 44% phosphorus (H3PO4)

• Formula: CO(NH2)2·H3PO4.



46 | P a g e

11. What is NPK fertilizer? Why it is called so?(May/June 2013)(May/June 2009)


potassium (K). NPK stands for "nitrogen, phosphorus, and potassium," the three nutrients that

compose complete fertilizers.

12. Show the action of urea as a fertilizer. (Nov/Dec 2011) (May/June 2009)

• Urea is an inexpensive form of nitrogen fertilizer with an NPK (nitrogen-

phosphorus-potassium) ratio of 46-0-0.

• urea will provide the most nitrogen at the lowest cost.

• It is easy to store and does not pose as a fire risk for long-term storage.

• Urea may be mixed with other fertilizers or may be applied on its own.

• For gardeners who grow crops like corn, strawberries, blueberries and other heavy

nitrogen feeders, urea will supply immediate and powerful applications of nitrogen.

13. What is granulated mixture? (April /May 2010)

Granulate mixture means a mixture of fertilizer made by intimately mixing two or more

fertilizers with or without inert material, and granulating them together, without involving any

chemical reaction. The limitations of physical mixtures can be eliminated through granulation.

The physical mixtures are granulated by injecting a small quantity of moisture or steam.

14. How ammonium sulphate act as a fertilizer?

It reacts with lime present in the soil to for ammonium hydroxide which is oxidized by air

with the help of nitrifying bacteria into nitrous acid. Later is then converted into nitrites.

The nitrous acid and nitrites also undergo oxidation by means of air in presence of nitrifying

bacteria and form nitric acid and nitrate.

15. Write the properties of ammonium phosphate.

• Molecular formula : NH4H2PO4


• Appearance : White crystal



• Density : 1.803gm/mL

• Solubility : Moderately soluble in

water

• pH : 4-4.5

• Highly soluble in water

16. Give the method of manufacturing of nitrophosphate.

The two commercially important nitrophosphate processes

• Odda process wherein calcium nitrate is precipitated and separated

• Mixed Acid “ process does not separate the calcium nitrate

17. Write the chemical reaction involved in the manufacturing of nitro phosphate.

18. Write method of handling of ammonium sulphate.

Handling and storage crystalline ammonium sulfate is free flowing and does not normally

pose any problem in handling and storage. However, it generally contains some powdered

material which causes caking, especially under high humidity. Due to its susceptibility to

caking and slight acidity, ammonium sulfate is normally bagged in polyethylene lined gunny

bags or high density polyethylene (HDPE) woven sacks.



47 | P a g e

Part-B

1. Discuss in detail about the ammonium phosphate production with neat flow sheet and

also illustrate the major engineering problems involved.(April/May 2018)

(Nov/Dec 2016, 17)

Ammonium phosphate ((NH4)3PO4) also known as ammonium orthophosphate is the salt of

ammonia and phosphoric acid. It consists of ammonium cations and phosphate anion. It is water

soluble and the aqueous solution on boiling losses ammonia.

There are two major types of ammonium phosphate which are monoammonium phosphate

(MAP, NH4H2PO4) and diammonium phosphate (DAP, (NH4)2HPO4) and these can be

inter-converted by changing ammonia or phosphoric acid as needed. Mono-ammonium phosphate

is manufacture by reacting ammonia with phosphoric acid, centrifuging and drying in a rotary

dryer. While diammonium phosphate requires two-stage reactor system in order to prevent loss of

ammonia. The granulation process followed by neutralization is completed in rotary dryer, which

is heated by a furnace using fuel.

Two grades of ammonium phosphate are available

1. Monoammonium phosphate (MAP)

Anhydrous ammonia added to liquid phosphoric acid gives monoammonium phosphate

(MAP). It is a fertilizer or fertilizer intermediate with high P2O5 content of about 55% and

nitrogen content 11-12%.

2. Diammonium phosphate (DAP)

With more ammonia, technical grade diammonium phosphate (DAP) containing 16 to 18%

nitrogen and 20 to 21 % phosphorus (46% P2O5) is formed.

Properties

• Molecular formula : NH4H2PO4


• Appearance : White crystal



• Density : 1.803gm/mL

• Solubility : Moderately soluble in

water

• pH : 4-4.5

• Highly soluble in water

Raw Materials

• Ammonia

• Phosphoric acid


The two principal steps are

a) Neutralization

b) Granulation



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a) Neutralization

Phosphoric and ammonia are added to the first of three continuous mixed reactors, anhydrous

ammonia is added beneath the slurry level in the first neutralizer in an amount equivalent to 80%

neutralization. Further ammonia is added in the 2nd and 3rd tanks to obtain conversion to the

diammonium salt if a higher nitrogen containing fertilizer is needed. The exothermic reaction heats the

slurry nearly to the boiling point (130°C). Unreacted and excess NH3 vapor is collected from the top of

each tank and recharged below the liquid level for reducing NH3 losses (less than 3%). The hot slurry

containing about 16 to 20% water is pumped into the granulator, where more ammonia is added to

increase the molar ratio to approximately 2.0.

b) Granulation

Slurry from the third neutralized is mixed with KCl and absorbed in a bed of dry recycle

fertilizer moving through a rotating drum granulator. This provides a tumbling action to coal recycle

material with a slurry film. A rotary adiabatic drier reduces the moisture to less than 1%, with 10

minute contact time with air initially at 1500C. Dried product is separated into three fractions on a

double deck screen. A portion of the product from the deck of the lower screen is sent to bagging

operations. The balance, together with pulverized oversize and fines, is returned to the granulator. The

weight ratio of recycle to product is 6: 1-15: 1 depending on the grade produced.

Uses

• Used as a high effective non-chloride N, P compound fertilizer in agriculture. It contains totally

73% fertilizer elements (N+P2O5), and may be used as a basic raw material for N, P and K

compound fertilizer

• In flame-proofing, plant nutrient solutions

• Used in manufacturing of yeast, vinegar, yeast foods, and bread improvers

• Used in buffer solutions and in analytical chemistry

• Used as a fire prevention agent for fabric, timber and paper, as well as a fire prevention coating,

and dry powder for fire extinguisher.

• For food grade, it is mainly used as a fermentation agent, nourishment agent.



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2. Explain in detail about the production of nitrophosphate with a neat flow sheet and also

illustrate the major engineering problems involved.(April/May 2018)(Nov/Dec 2016,17)

Nitrophosphate” is the generally accepted term for any fertilizer that is produced by a process involving

treatment of phosphate rock with nitric acid.

Fundamentals of Nitrophosphates

The basic (and simplified) acidulation reaction can be represented by the following reaction

equations:

After separation of the insoluble material, phosphoric acid is neutralized with ammonia to

produce a fertilizer. If the calcium nitrate is left in the solution, it reverts to dicalcium phosphate

ammonium following the reaction:



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Calcium is non-nutrient in terms of N, P, and K and is therefore seen as a diluent. For these

reasons alone, it is desirable to remove calcium from the solution. But there is another, more important

reason.

Manufacture:

The two commercially important nitrophosphate processes

1. Odda process wherein calcium nitrate is precipitated and separated

2. “Mixed Acid “ process does not separate the calcium nitrate

Odda Process With Calcium Precipitation

Nitrate containing fertilizers can be produced from the nitrophosphoric acid produced, by

neutralising with ammonia and with the possible addition of nitric acid, ammonium sulphate or

sulphuric acid, potassium and magnesium salts and micronutrients. This production is carried out in

three sections; neutralisation, particle formation and conditioning.

Dissolving Section

Phosphate rock and nitric acid(60%) are mixed together in the dissolving reactors at 60°-70°C(Reactor

temperature) by cooling or heating Nitric acid. Inerts(diluents of nutrients in the final product and can

cause damage to equipment) are separated from the dissolving solution by gravity in lamella separators

Crystallization Section

Dissolving solution (NP solution) is fed intermittently to a number of batch-operated standard

crystallizers (-2° to -5°C). Cooling for crystallization is obtained by evaporating ammonia for the NP

solution neutralization and calcium nitrate (CN)- conversion sections.

Neutralization Section

In the neutralization section, the nitrogen and phosphorous elements in the NP solution are

converted to the form they will have in the product. Correct operation of this section is important

because the N:P2O5 ratio of the final product is controlled here. This control is achieved by mixing NP

acid obtained from the calcium nitrate tetrahydrate- filters with ammonium nitrate solution and with an

original dissolving solution. Neutralization by gaseous ammonia occurs in a pressurized reactor at 1.5-

2.5 bar and a temperature of 150°-180°C or in forced-circulation neutralizers. Because of the heat of

reaction, water and ammonia are evolved during neutralization; this decreases the water content of the

slurry which is then further concentrated in a series of circulating evaporators. The neutralization and

evaporation operations have their own scrubber system for offgases. The scrubbing liquor is composed

mainly of ammonium nitrate solution, which is later recycled to the neutralization section for nutrient

recovery.

Finishing Section

The final slurry after ammoniation and evaporation is formed into granules, with or without

addition of potash salts,



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3. How is ammonium sulphate manufactured?(May/June 2013)How is obtained from

Gypsum(May/June 2012)(April 2016)

Ammonium sulfate containing 21% nitrogen is another important nitrogenous fertilizer. It is

a quick-acting fertilizer. It occurs naturally as the mineral mascagnite and offers many advantages as a

fertilizer, such as low hygroscopicity, good physical properties, excellent chemical stability, good

agronomic effectiveness and long shelf life. Ammonium sulfate is an acid forming fertilizer, and hence

used in neutral or alkaline soils.

2NH4OH + H2SO4 (NH4)2SO4 + 2H2O

PROPERTIES

• Molecular formula

(NH4)2SO4

• Molecular weight

132.14gm/mole

• Solubility : Solubility in

water and insoluble in

alcohol, ether, acetone

• Appearance : Fine white

hygroscopic granules or

crystals

• % of nitrogen : 20-21%


• Bulk density : 720-

1040kg/m3

• Melting point : >2800C

• Specific gravity : 1.769

• Moisture: 1% wt. (Max.)

USES

• fertilizers (combination with other materials, such as urea, to make dry fertilizers)

• Good source of nitrogen for cotton, rice, wheat, barley, maize, sorghum, sugar cane and fiber

crops.

• Food additive, dough conditioner and food for yeast.

• Medical application development of vaccines. The DTaP vaccine, for example, which protects

children from diphtheria, tetanus and whooping cough, uses ammonium sulfate in the

purification process

• Used in rice and jute cultivation

MANUFACTURE Gypsum process

Raw materials Ammonia , CO2 and Gypsum

Ammonia is manufactured by Haber process and CO2 is manufactured by heating limestone.

Ammonia is absorbed in water and carbonated at the pressure of about 2.1kg/cm2 in towers packed

with aluminum rings. Natural gypsum or anhydrite, when used, is ground so that about 90% of the

material passes through 120 mesh sieve. When the byproduct gypsum of phosphoric acid plant is used,

the impurities are removed by repulping the filter cake prior to washing and dewatering on a drum or

disc filter.



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Now proper proportion of finely ground gypsum or anhydrite is fed into the aqueous solution of

ammonium carbonate in large tanks, whereby calcium carbonate is precipitated gradually as a result of

double decomposition.

Reactions of ammonium carbonate and gypsum solutions are carried out in a series of wooden

vessels or mild steel vessels having steam coils and agitators to give a total retention time of 4 to 6

hours. CO2 and NH3 are passed until all the gypsum is converted into CaCO3. The slurry produced is

filtered and the calcium carbonate cake washed and dewatered. The solution is evaporated and the

crystals are centrifuged and dried in a rotary drier at 1200C. CaCO3 obtained as by product is used as a

raw material for the manufacture of cement.


Handling and storage crystalline ammonium sulfate is free flowing and does not normally pose

any problem in handling and storage. However, it generally contains some powdered material

which causes caking, especially under high humidity. Due to its susceptibility to caking and slight

acidity, ammonium sulfate is normally bagged in polyethylene lined gunny bags or high density

polyethylene (HDPE) woven sacks.

Action of (NH4)2SO4 as fertilizer

It reacts with lime present in the soil to for ammonium hydroxide which is oxidized by air with

the help of nitrifying bacteria into nitrous acid. Later is then converted into nitrites. The nitrous acid

and nitrites also undergo oxidation by means of air in presence of nitrifying bacteria and form nitric

acid and nitrate.



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4. Explain the various grades of NPK fertilizers produced in our country.(April 2016)


potassium (K), each element has been found to improve the health and appearance of plants. NPK

stands for "nitrogen, phosphorus, and potassium," the three nutrients that compose complete

fertilizers.

For example,




Oftentimes the soil the plants are growing in lacks some of these nutrients, so by adding them in

as a fertilizer, plants do better.

Importance of NPK fertilizer

All plants need nitrogen, phosphorus and potassium to grow. Without enough of any one of

these nutrients, a plant will fail.

• Nitrogen (N) – nitrogen is largely responsible for the growth of leaves on the plant.

• Phosphorus (P) – Phosphorus is largely responsible for root growth and flower and fruit

development.

• Potassium (K) – Potassium is a nutrient that helps the overall functions of the plant performs

correctly.

NPK grade

• All fertilizer labels have three bold numbers. The first number is the amount of nitrogen (N), the

second number is the amount of phosphate (P2O5) and the third number is the amount of potash

(K2O). These three numbers represent the primary nutrients (nitrogen (N) - phosphorus (P) -

potassium (K)). This label, known as the fertilizer grade, is a national standard.

• Example: A bag of 15-15-15 fertilizer contains 15 percent nitrogen, 15 percent phosphate and

15 percent potash.

Various grades of NPK fertilizer

Prior to 1960/61, India produced only straight nitrogenous fertilizers [ammonium sulphate

(AS), urea, calcium ammonium nitrate (CAN), ammonium chloride and single superphosphate

(SSP)]. Currently, India produces a large number of grades of NP / NPK complex fertilizer. These

include 16–20–20, 20–20–0, 28–28–0, 15–15–15, 17–17–17, 19–19–19, 10–26–26, 12–32–16,

14–28–14, 14–35–14 and 19–19–19. In addition, India produces various grades of simple and

granulated mixtures.



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Year of

manufacture Fertilizer product Total number of units

1906 SSP 65

1933 AS 10

1959 Ammonium sulphate nitrate No longer manufactured

1959 Urea 29

1959 Ammonium chloride 1

1960 Ammonium phosphate 3

1961 CAN 3

1965 Nitro phosphate 3

1967 DAP 11

1968 TSP No longer manufactured

1968 Urea ammonium phosphate 2

1968 NPK complex fertilizers 6

The total indigenous capacity of N and P2O5 increased from 17 000 and 21 000 tonnes in

1950/51 to 12 276 million and 5 547 million tonnes in 2004/05.

Characteristics of NPK fertilizers.

S.No NPK fertilizer Characteristics

1 Monoammonium phosphate

• Appearance : White Powder

• Total N Content : 10.0 %

• Total P2O5 Content : 49.0 %


• Formula : (NH4)H2PO4

2 Diammonium phosphate

• Appearance : Free flowing light yellow

granular

• Total N Content : 16.0 – 18.0 %

• Total P2O5 Content : 46.0 – 48.0 %


• Formula : (NH4)2HPO4

3 Urea ammonium phosphate

• Soluble in water

• 17,5 % urea (NH2)

• 44% phosphorus (H3PO4)

• Formula: CO(NH2)2·H3PO4.



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5. Briefly explain the typical NPK fertilizer production process with a neat sketch (April/May

2015)


potassium (K), each element has been found to improve the health and appearance of plants. NPK

stands for "nitrogen, phosphorus, and potassium," the three nutrients that compose complete

fertilizers.

For example,




Oftentimes the soil the plants are growing in lacks some of these nutrients, so by adding them in

as a fertilizer, plants do better.

NPK complex fertilizers are solid fertilizers in the form of uniform granules commonly referred

to by a sequence of three numbers, the first of which represents the percent nitrogen expressed as

Nitrogen, the second, the percent Phosphorous expressed as available P2O5 and the third, the percent

potassium expressed as soluble K2O. These fertilizers are very convenient to use because they contain

all the three primary plant nutrients in the desired proportions. The various grades produced and

marketed in the country are 17-17-17, 10-26-26, 12-32-16 and 14-35-14.

Raw materials/ sources:

Required raw materials are Phosphoric acid, ammonia, potash and urea where necessary to

increase the nitrogen content. Fillers (sand, dolomite, etc.) and coating agents (clay, soapstone etc.) are

also required for certain grades.

Methods of manufacture:

Ammonia and phosphoric acid in the required proportions are metered to the pre neutralizer and

the resultant slurry is pumped to the granulator, which can be a blunger or a rotating drum. Here the

nitrogen content is increased by adding more ammonia and feeding in urea whenever necessary.

Filler(sand or dolomite) and potash are also added to make up the required product formulation. The

granulator discharge is then dried, screened, cooled and coated with a coating agent (clay or powdered

soapstone) to improve the storage properties.

A flow sheet for the process is shown below:



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FLOWSHEET FOR MANUFACTURE OF NPK COMPLEX FERTILIZERS

AMMONIA

PHOS

-

PHOR

IC

ACID

UREA

PRE NEUTRALIZATION

NEUTRALIZATION

AMMONIATION

GRANULATION

DRYING

SCREENING

COOLING

COATING

NPK

COMPLEX

POTASH



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6. Explain with flow sheet the method of production of monoammonium phosphate(April/May

2015)

Ammonium phosphate ((NH4)3PO4) also known as ammonium orthophosphate is the salt of

ammonia and phosphoric acid. It consists of ammonium cations and phosphate anion. It is water

soluble and the aqueous solution on boiling losses ammonia.

There are two major types of ammonium phosphate which are

• Monoammonium phosphate (MAP, NH4H2PO4)

• Diammonium phosphate (DAP, (NH4)2HPO4)

These can be inter-converted by changing ammonia or phosphoric acid as needed.

Monoammonium phosphate (MAP)

Mono-ammonium phosphate is manufacture by reacting ammonia with phosphoric acid,

centrifuging and drying in a rotary dryer.

Anhydrous ammonia added to liquid phosphoric acid gives mono ammonium phosphate (MAP).

It is a fertilizer or fertilizer intermediate with high P2O5 content of about 55% and nitrogen content

11-12%.

Chemical Reactions:

NH3 + H3PO4 NH4H2HPO4

NH3 + NH4H2PO4 (NH4)2HPO4

NH3 + H2SO4 NH4HSO4

NH3 + NH4HSO4 (NH4)2SO4



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7. Explain with flow sheet the method of production of monoammonium phosphate

Diammonium phosphate (DAP)

While diammonium phosphate requires two-stage reactor system in order to prevent loss of

ammonia. The granulation process followed by neutralization is completed in rotary dryer, which is

heated by a furnace using fuel. With more ammonia, technical grade di ammonium phosphate (DAP)

containing 16 to 18% nitrogen and 20 to 21 % phosphorus (46% P2O5) is formed.

Chemical reaction involved in the production of Diammonium phosphate.

Diammonium phosphate (DAP) (chemical formula (NH4)2HPO4, IUPAC name diammonium

hydrogen phosphate) is one of a series of water-soluble ammonium phosphate salts that can be

produced when ammonia reacts with phosphoric acid. Solid diammonium phosphate shows a

dissociation pressure of ammonia as given by the following expression and equation:

NH4)2HPO4(s) ⇌ NH3(g) + NH4H2PO4(s) log PmmHg = −3063 / T + 175 log T + 3.3

Manufacture of Diammonium phosphate (dap)

Phosphoric acid, being a tribasic acid could theoretically form three ammonium phosphates by

the successive substitution of the acid by ammonia

H3PO4 NH4H2PO4 (NH4)2HPO4 (NH4)3PO4

However, triammonium phosphate is unstable and easily loses ammonia. Both MAP and DAP are

manufactured as fertilizers.Pure

• DAP would have the composition in NPK nomenclature 21.19 : 53.76 : 0 Typically DAP made

from wet process of phosphoric acid has the range of compositions 16- 18: 46- 48: 0

• DAP may be made in the form of granules for direct distribution or blending and in the form of

powder for incorporation with other fertilizers in compound manufacture.

Process Description

DAP may be made by neutralizing phosphoric acid with ammonia to pH 5.6 in the molar ratio

2: 1, but on an industrial scale attention is given to the solubility of the product. The composition of the

mixture, which is most soluble in, water beyond the mono ammonium stage s a molar ratio of 1.4: 1.

Therefore, the practice is to remix the reactants in this ratio, ex: in a tank or in a pipe, where the slurry

is most fluid also and to pump it to the granulator where the slurry meets the fines from a subsequent

sieving process and more ammonia to bring the NH3: H3PO4 molar ratio to 2: 1.

The liquid ratio is thereby decreased and the process of granulation made easier. The conc. of

H3PO4 used may vary with the manufacturer, but typically is 40% P2O5 when the temperature of the

slurry rises to about 115˚C. The product from the granulator falls into a drier and meets the co- current

flow of hot combustion gases. The dry granules are spread on to the screens and those falling within the

screen limits pass into a counter current flow of ambient air and then to the store. The oversize is

passed through a crusher ex: of the cage and chain type and back on the screens. The fines are returned

https://en.wikipedia.org/wiki/IUPAC

https://en.wikipedia.org/wiki/Water


https://en.wikipedia.org/wiki/Ammonium_phosphate

https://en.wikipedia.org/wiki/Salts


https://en.wikipedia.org/wiki/Phosphoric_acid



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to the granulator. The recycle ratio of fines to product is usually about 5: 1. The exhaust gases from all

equipment are passed to an absorption tower sprayed with the H3PO4 to be fed to the reactor.

The reactor may be a simple tank or a serried of tanks, as in the triple super phosphate plant. The

reactor may also be a closed vessel. Ex: a pipe in which the steam generated acts as a kind of lift to the

slurry and flashes off when it reaches the atmosphere in the granulator. The reaction approaches

adiabatic condition. Drying cost is much less.



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Unit – V COMPLEX AND NPK FERTILIZERS

Part- A

1. What are mixed fertilizers? (April 2014)(April/May 2018)

Mixed fertilizer typically refers to a fertilizer containing two or more of the elements

of nitrogen, phosphorus and potassium (NPK) which are essential for promoting plant growth and

high crop yields. Mixture of two or more straight fertilizer material is referred to as mixed fertilizer

or fertilizer mixture. Mixed fertilizers are physical mixtures of fertilizer materials containing two or

three major plant nutrients. Mixed fertilizers are made by thoroughly mixing the ingredients either

mechanically or manually. Depending upon the method of preparation two types of fertilizer

mixtures are available

• Open formula fertilizer mixtures

• Closed formula fertilizer mixtures

2. What is fluid fertilizer? (April/may 2018)

Fluid Fertilizer is liquid fertilizer. They are popular because of the ease of handling and use.

Movement is by pump, and they usually require less labor to handle. Some pesticides can be

injected into the fluid, saving trips across the field. Fertilizers custom blended to specifications are

available. The major types of fluid fertilizers are suspension fertilizers and solution fertilizers. Main

differences between fluid and dry fertilizers are fluid fertilizer dissolve in water and dry fertilizers

are not.

3. What is biofertilizer? (Nov/ Dec 2017,11)(April/May2011) (May/June 2012, 13)

(April 2016)

A biofertilizer is a substance which contains living microorganisms which, when applied to

seed, plant surfaces, or soil, colonizes the rhizosphere or the interior of the plant and promotes

growth by increasing the supply or availability of primary nutrients to the host plant.Bio-fertilizers

add nutrients through the naturalprocesses of nitrogen fixation, solubilizing phosphorus, and

stimulating plant growth through the synthesis of growth-promoting substances.

Some important groups of Bio-fertilizers

• Azolla-Anabena symbiosis

• Rhizobium

4. Write the trace elements required for the plant growth?(Nov/Dec 2016)

(April/May 2015)

A trace element is any chemical element that is present in minute amounts in an environment or

ecosystem. Some nutrients are required in large quantities by plants (Major or Macro nutrients)

and some in very small quantities (Micro or Trace elements).

Micronutrients (or) Trace elements:

Zinc, boron, copper, manganese, chlorine, iron and molybdenum are required in little

amount by the plants and so these are called micro nutrients.

5. What are granulated fertilizers?(April/May 2010)

Fertilizers in the form of small lumps or granules. Their advantages are friability,

freedom from caking, and improvedagrotechnical properties. Mixtures are made into granules

by moistening during the granulation process. The granular form is easier to apply, less dust

formation, free flowing and is preferred over the pulverized form. Ideal granular fertilizers have

homogeneous, spherical particles in the size range of 10-14mesh.



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6. What is the need of controlled release fertilizers? (Nov/Dec 2016)

• Reduce risk of environmental losses.

• Nutrient release is controlled

• Improved fertilizer use efficiency, reduced fertilizer pollution in wastewater

• Coated fertilizers are excellent alternatives to soluble fertilizers because of slow release of

nutrients amidst the season.

• Plants can take up most of the nutrients without waste by leaching.

• Eliminating the need for multiple fertilizer applications

• Prolonged nutrient release can provide more uniform plant nutrition, better growth, and

improved plant performance

• Best efficiency of nutrient use

7. What are coated fertilizers? (April 2016)

Coated fertilizers are a group of controlled release fertilizers. A variety of coatings have been

applied to fertilizer particles to control their solubility in soil. Controlling the rate of nutrient release

can offer multiple environmental, economic, and yield benefits. Coatings are most commonly

applied to granular or prilled nitrogen (N) fertilizer, but multi-nutrient fertilizers receive the

coatings as well.

Types

• Sulfur coated urea

• Polymer coated (or) Poly-coated urea

• Combination product

8. Mention the use of fluid fertilizer?(April/May 2015)

• The nutrients reach the plant roots immediately

• The solution is sufficiently diluted so that it does not inhibit growth

• It allows direct utilization of the cheapest N source

• Less labor to handle

• Fluid fertilizer dissolve in water and dry fertilizer are not

9. What are secondary nutrients? (April/May 2011)

Those nutrients, which are not so vital as the NPK and are not required at such large quantities,

are secondary nutrients. They are required only in small levels and they aid in proper utilization of

NPK nutrients and in proper plant growth. Calcium, magnesium and sulfur which occur to a limited extent in all soils, are called

secondary nutrients.

10. Define the term complex fertilizer? (April/May 2008)

Complex fertilizers (also known as compound fertilizers) are made from mixing two or more of

macro-nutrient type fertilizers. They may also be further blended with elements that provide some

of the less-common plant nutrients (known as secondary or trace nutrients, such as sulfur, calcium

and magnesium).

11. Give two advantages of bio fertilizers over chemical fertilizers.

Bio fertilizers are organisms that enrich the nutrient quality of soil. The main sources of bio

fertilizers are bacteria, fungi, and cynobacteria (blue-green algae).

Bio fertilizers are environment friendly and will help solve such problems as increased salinity

of the soil and chemical run-offs from the agricultural fields


https://en.wikipedia.org/wiki/Controlled_release_fertilizer



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12. Give the composition of mixed fertilizer?(April 2014)

The best mixed fertilizers are obtained when granulated components are mixed. The nutrient

ratio to be used in mixed fertilizers depends on crop requirements and soil characteristics. For

example, a 1 : 1 : 1 ratio of nitrogen, phosphorus, and potassium (that is, N, P2O5, and K2O) is the

basic fertilizer for grain crops, sugar beets, potatoes, and vegetables on soddy podzols, gray forests,

and chernozems, and a 1 : 1.5 : 1 ratio is applied at planting time for grains, vegetables, and

industrial crops.

13. What is controlled release fertilizer?(April 2014)

A controlled-release fertilizer (CRF) is a granulated fertilizer that releases nutrients gradually

into the soil (i.e., with a controlled release period).

The slowness of the release is determined by the low solubility of the chemical compounds in

the soil moisture.

Since conventional fertilizers are soluble in water, the nutrients can disperse quickly as the

fertilizer dissolves. Because controlled-release fertilizers are not water-soluble, their nutrients

disperse into the soil more slowly.

The fertilizer granules may have an insoluble substrate or a semi-permeable jacket that prevents

dissolution while allowing nutrients to flow outward.

14. What are nitrogen solutions? (May/June 2013)

Nitrogen solutions are water solutions of selected nitrogen chemicals that are blended, rather

than being the products of chemical reaction. Historically, they have been used almost totally as

fertilizers, although some water-based ammonium nitrate slurries are used in certain commercial

explosive and blasting agent markets.

However, as a result of environmental legislation, use of purified urea solutions has begun and

will be the fastest-growing market for nitrogen solutions.Urea–ammonium nitrate solutions,

containing 28–32% nitrogen, and account for the bulk of the solutions market.

A small but growing amount of ammonium nitrate and calcium ammonium nitrate solution is

also consumed. Fertilizer applications account for the vast majority of consumption. World

supply/demand for nitrogen solutions is forecast to grow at an average rate of 2.8% annually during

2011–2016.

Nitrogen solutions account for 5.8% of the world nitrogen fertilizer market, but account for

approximately 30% of the market in the United States and approximately 9% in Western Europe.

They are growing faster than dry nitrogen-containing fertilizers.

15. Which material will hold back stem growth and halt plants at the desired height?

Addition of Nitrogen will hold back stem growth and halt plants at the desired height.

16. What are nutrients?

Nutrients are such substances which when added to the medium in which plants are grown, are

able to improve the plant growth and quality. The elements which are required for the growth of

plants are known as plant nutrients.

17. How do you prevent caking of fertilizer?

Caking of the fertilizers can be prevented by the addition of conditioners to fertilizers, but

caking of fertilizer is effectively prevented by granulation and pelletization

https://en.wikipedia.org/wiki/Granulated

https://en.wikipedia.org/wiki/Nutrient

https://en.wikipedia.org/wiki/Soil

https://en.wikipedia.org/wiki/Controlled_release


https://en.wikipedia.org/wiki/Permeability_(earth_sciences)



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18. What are primary nutrients?

Primary nutrients are normally supplied through chemical fertilizers as their quantity required

for unhindered and proper growth plant is more. They are namely Nitrogen N, Phosphorus P, and

Potassium K.

19. What are micronutrients? (April/May 2010)

Micronutrients are also called minor elements or trace elements are as essential to plants growth

as the major elements. However they are required only in small quantities. Ex: Zinc, Boron,

Molybdenum, Chlorine, and Sodium

20. What are macronutrients?

Those nutrients, which are required in large quantities for the plant growth, are known as

macronutrients. Their application is vital for proper growth of plants. They are Carbon, Hydrogen

and Oxygen.

21. What are fluid fertilizers? Give its advantages. (April/May2010), (May/June 2009),

(April/May2011), (May/June 2012)

Fluid fertilizers offer ease of use. Movement is by pump, and they usually require less labor to

handle. Some pesticides can be injected in the fluid thus saving trips across thefield. Experienced,

well-equipped dealers can custom blend fertilizers to specifications. The major types of fluid

fertilizers are suspension fertilizers and solution fertilizers.

22. What are controlled release fertilizers? (May/June 2014)

These fertilizers are applied in such a way that the mixture in released in a controlled fashion.

Methods of applying CRF including top-dressing and incorporation in to the media, or dibbling.

The latter is a method in which the fertilizer material is placed in a hole in the container media,

allowing the fertilizer to remain at a more controlled release temperature. Various types:1.poly-s

2.urea formaldehyde 3.magnesium ammonium phosphate

23. Whar are the Benefits of using Biofertilizers?

As it is living thing, it can symbiotically associate with plant root. Involved microorganisms

could readily and safely convert complex organic material in simple compound, so that plant easily

taken up. Microorganism function is in long duration causing improvement of the soil fertility. It

maintains the natural habitat of the soil. It increases crop yield by 20-30%. Replace chemical

nitrogen and phosphorus by 25% in addition to stimulating of the plant growth. Finally it can

provide protection against drought and some soil borne diseases.

24. What are Organic fertilizers?

Organic Fertilizers are the most convenient forms of fertilizers. They are safe and easily

available. Things like manure, slurry, worm castings, peat moss, seaweed, sewage and guano are

good examples of organic fertilizers. Vegetation material called mulch, such as hay, peat moss,

leaves, grass, bark, wood chips, seed hulls, and corn husks all help to aerate the soil, insulate the

ground against temperature change, and add needed nutrients.

25. What are the Advantages of Organic Fertilizer?

➢ Improve the structure of the soil.

➢ Retain soil moisture.

➢ Release nitrogen slowly and consistently.

➢ Mobilize existing soil nutrients.

➢ Do not burn the plants like some chemical fertilizers

➢ Less subject to leaching



67 | P a g e

26. Difference between macro and Micro nutrient.

S.no Micro nutrient Macro nutrient

1 Required in minute quantities Required in large quantities

2 Example: Fe, Mn, Cu, Zn, Mo, B, Cl

and Ni

Example: C, H, O, N, P, K, Ca, S and Mg

3 Concentration present in plant cell

< 1mg/g dry weight

Concentration present in plant cell

>1 mg/g dry weight

4 Also called Trace element Also called Major element

5 All micro nutrients are minerals and

are absorbed through roots

Majority of macro nutrients are minerals

and they absorbed through roots some are

not (C,H and O)

6. They do not have any role in building

the body structure

Used for the building the body structure

Part- B

1. Describe in detail about the nutrients, secondary nutrients and micronutrients. (April/May

2018)(Nov/Dec 2016,17)

Nutrient:

• A nutrient is a substance used by an organism to survive, grow, and reproduce.

• A substance that provides nourishment essential for the maintenance of life and for growth

• A nutrient is any substance that is absorbed and either provides you with energy or enables

growth, repair or proper functioning of your body.

• Nutrients are such substances which when added to the medium in which plants are grown, are

able to improve the plant growth and quality. The elements which are required for the growth of

plants are known as plant nutrients.

Examples of nutrients and their functions:

• Starch and its breakdown product glucose provide you with energy.

• Proteins build muscles and form enzymes.

• Lipids form the cell membranes and certain hormones.

• Potassium and sodium enable the proper functioning of the nerves.

• Vitamin C is necessary for the wound healing.

PLANT NUTRIENTS

• Plants require following nutrient elements for their growth

• Sixteen chemical elements are known to be important to a plant's growth and survival.

The sixteen chemical elements are divided into two main groups: non-

mineral and mineral.

https://en.wikipedia.org/wiki/Chemical_substance

http://www.nutrientsreview.com/carbs/polysaccharides-starch.html

http://www.nutrientsreview.com/carbs/monosaccharides-glucose.html

http://www.nutrientsreview.com/proteins

http://www.nutrientsreview.com/lipids

http://www.nutrientsreview.com/minerals/potassium-kalium.html

http://www.nutrientsreview.com/vitamins/vitamin-c-ascorbic-acid.html

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Non-Mineral

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Non-Mineral

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Mineral



68 | P a g e

Non-Mineral Nutrients

• These nutrients are found in the air and water.

• In a process called photosynthesis, plants use energy from the sun to change carbon

dioxide (CO2 - carbon and oxygen) and water (H2O- hydrogen and oxygen) into

starches and sugars. These starches and sugars are the plant's food.

• Examples: Hydrogen (H), Oxygen (O), & Carbon (C).

Mineral Nutrients

• The 13 mineral nutrients, which come from the soil, are dissolved in water and

absorbed through a plant's roots. There are not always enough of these nutrients in the

soil for a plant to grow healthy. This is why many farmers and gardeners use fertilizers

to add the nutrients to the soil.

• The mineral nutrients are divided into two groups:

1. Macronutrients

2. Micronutrients

1. Macronutrients

Macronutrients can be broken into two more groups: primary and secondary nutrients.

The primary nutrients are nitrogen (N), phosphorus (P), and potassium (K). These

major nutrients usually are lacking from the soil first because plants use large amounts for their

growth and survival.

The secondary nutrients are calcium (Ca), magnesium (Mg), and sulfur (S). There are

usually enough of these nutrients in the soil so fertilization is not always needed. Also, large

amounts of Calcium and Magnesium are added when lime is applied to acidic soils. Sulfur is

usually found in sufficient amounts from the slow decomposition of soil organic matter, an

important reason for not throwing out grass clippings and leaves.

2. Micronutrients

Micronutrients are those elements essential for plant growth which are needed in only

very small (micro) quantities. These elements are sometimes called minor elements or trace

elements, but use of the term micronutrient is encouraged by the American Society of

Agronomy and the Soil Science Society of America.

The micronutrients are boron (B), copper (Cu), iron (Fe), chloride (Cl),

manganese (Mn), molybdenum (Mo) and zinc (Zn). Recycling organic matter such as grass

clippings and tree leaves is an excellent way of providing micronutrients (as well as

macronutrients) to growing plants.

Natural nutrients

Carbon, hydrogen and oxygen are derived from air and water and so these are called natural nutrients. Note:

Whether a macronutrient or micronutrient, or whether a primary or secondary nutrient, the

Law of the Minimum holds: the most growth-limiting nutrient will limit growth, no matter how

favorable the nutrient supply of other elements. For example, a deficiency of Fe or Mn (most common

in soils containing calcium carbonate) can severely limit plant growth in spite of adequate N, P, and K.

Law of the Minimum states that yield is proportional to the amount of the most limiting

nutrient, whichever nutrient it may be. From this, it may be inferred that if the deficient nutrient is

supplied, yields may be improved to the point that some other nutrient is needed in greater quantity

than the soil can provide, and the Law of the Minimum would apply in turn to that nutrient.

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Macronutrients

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Micronutrients

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Nitrogen

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Phosphorus

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Potassium

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Calcium

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Magnesium

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Sulfur

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#SoilpH

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Boron

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Copper

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Iron

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Chloride

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Manganese

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Molybdenum

http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm#Zinc

https://soils.wisc.edu/facstaff/barak/soilscience326/lawofmin.htm



69 | P a g e

FUNCTION OF NUTRIENT

• Nitrogen - Important constituent for synthesis of amino acids, special constituent of the

chlorophyll

• Phosphorus - Respiratory and photosynthetic processes

• Potassium - Healthy growth of plants, deficiency of potassium quickly reduces the

carbohydrate contents.

• Magnesium - Formation of phospholipids and in the synthesis of nucleoproteins

• Calcium - Constituent in the cell walls of leaves in the form of calcium pectate.

• Sulfur - Deficiency of sulfur decreases the plant growth accompanied by extensive

yellowing of green

• Iron - Deficiency of iron causes leaves to turn white and growth to cease

• Zinc – Involved in enzyme systems in the plant

2. Explain briefly on Mixed fertilizer and Granulated fertilizer (Nov/Dec 2016)

➢ Mixed fertilizer (April 2016)

Mixed fertilizer typically refers to a fertilizer containing two or more of the elements of

nitrogen, phosphorus and potassium (NPK) which are essential for promoting plant growth and high

crop yields. They are obtained by thoroughly mixing the ingredients either manually or

mechanically.NPK mixture fertilizers are formulated and recommended by agricultural scientists to

enhance the output of crops by giving it specific and exclusive blend of plant nutrients. They are

slow releasing by nature and remain in the field for a long time. They are tailor made as per the soil

and are crop specific.

Mixed fertilizers are of two kinds:

1. Open formula mixed fertilizer: In this case, the manufacturing firms disclose the names and

quantities of the straight fertilizers that are constituents of the mixed fertilizer.

2. Close formula mixture: In this case, the manufacturing firms do not disclose the names and quantities

of the straight fertilizers that are constituents of the mixed fertilizer.

The following materials are required to make the mixed fertilizer:

(i) Straight fertilizers are the primary materials used for making the mixed fertilizer.

They supply the fertilizer element required in the proper amount to the soil.

(ii) Some low grade organic materials are added @ 100 pounds per ton to the mixed fertilizer

in order to prevent caking, and to maintain them in a good physical condition. These organic materials

(peat, paddy husk etc.) are called conditioners.

(iii) Some basic material like Dolomite is added to neutralize acidity if the fertilizer mixture

produces acids.

(iv) Some materials like finely ground ash, soil etc. are added to make up the difference

between the weight of the fertilizer necessary to supply the plant nutrients and the desired quantity of

fertilizer mixture.

Terms used in fertiliser mixtures

• Fertiliser grade

• Plant nutrient suppliers

• Conditioners

• Neutralizers

• Filler



70 | P a g e

Advantages of Mixed Fertilizers:

Mixed fertilizers have a number of advantages, a few of them being:

• Use of mixed fertilizers results in reduction of labor costs as applying a mixture consumes

lesser time as compared to applying the components separately.

• Micro nutrients which help in increasing soil organic matter content are applied in small

amounts to the soil. They can be incorporated in fertilizer mixtures. This facilitates uniform soil

application of plant nutrients.

• If a proper mixture suits a particular soil type and crop, the use of a fertilizer mixture leads to

balanced manuring. It results in higher crop yield.

• Being in granulated form, mixtures have a better physical condition and hence their application

is easier.

• Residual acidity of fertilizers can be controlled by using neutralizers in the mixture.

Disadvantages of a Mixed Fertilizer:

• The use of mixed fertilizer does not permit application of individual fertilizer elements, which

may be required by the crop at specific times.

• The illiterate farmer cannot effectively control the quantity of plant food present in the mixture.

He has to rely entirely on the grade advertised by the firms.

• The firms charge for mixing the fertilizers.

However, the following important principles must be taken into consideration while preparing mixed

fertilizers.

1. All fertilizers containing ammonia are not mixed directly with the basic fertilizers

(e.g. RP, limestone, basic slag, CaCN2) as reaction will take place resulting in the loss of gaseous NH3.

2. The water – soluble phosphates are not mixed with those materials which contain free lime

(e.g.) lime stone, CaCN2) as there will be reaction towards the reversing of water – soluble phosphate to

water – insoluble phosphates.

3. Hygroscopic fertilizers are not included as they will facilitate caking up. 4. The acidic

fertilizers are likely to produce so

➢ Granulated fertilizer: (April 2016)

Products supplying vital nutrients into the growing medium that are necessary for correct

growth of the plants and influence their physical, chemical and biological condition.

Granulation is an operation by which a material is turned into granules of a more or less

uniform size (lumps (or) spheres in shape). When granulated water soluble chemical fertilizers have a

better physical condition.

Advantages

• Friability

• Freedom from caking

• Improved agro technical properties

• Less Dusty

• Easier to drill into the soil

• Better utilized by plant life because they are washed-out by ground water at a much slower

rate

• Less degraded by contacted with soil components



71 | P a g e

For example, granular superphosphate decomposes (converts to an unusable state) more slowly

than the powdered form, since it has less contact with the soil. Therefore, the phosphorus of pelletized

superphosphate ismore thoroughly utilized by plants. Granular fertilizers, especially superphosphate

are the most effective for application inrows or in seed drill holes along with the seed

Prior 1920, fertilizer was generally finely divided, with some lumps formed due to high

moisture contents of the product. It became more and more difficult to produce fertilizers of

acceptable physical properties for ammonium nitrate, urea and ammonium phosphates. So, various

methods were developed to increase the particle size of such fertilizers, in order to reduce moisture

absorption by reducing surface area and to minimize caking by reducing the number of contact points

between the particles. In 1935, Nitrophoska first prepared a multi-nutrient fertilizer in granular form

containing a granulated mixture of ammonium nitrate, diammonium phosphate and potassium

chloride. After that the development of products range from semi-granular mixed fertilizers to

granular and to urea and ammonium nitrate prills have been carried out.

Ideal granular fertilizers have homogeneous, spherical particles in the size range of 10-14mesh.

Modern granular fertilizers are satisfactory products which also reduce fertilizer cost by the use of

high analysis, hygroscopic materials. Farmers now also demand granular fertilizer because of its

attractive appearance, freedom from dust and ease of handling.

Granulation by agglomeration and accretion is effected in pan, Screw conveyor and rotary drum

granulators and is followed by drying the granules in drum driers. When the feed is a melt, the

granules thus produced are then allowed to solidify in drum cooler (or) in a fluidized bed units.

3. What do you understand by controlled release fertilizer? Explain.(April 2016)

A controlled-release fertilizer (CRF) is a granulated fertilizer that releases nutrients gradually

into the soil (i.e., with a controlled release period). The slowness of the release is determined by the

low solubility of the chemical compounds in the soil moisture. Since conventional fertilizers

are soluble in water, the nutrients can disperse quickly as the fertilizer dissolves. Because

controlled-release fertilizers are not water-soluble, their nutrients disperse into the soil more slowly.

The fertilizer granules may have an insoluble substrate or a semi-permeable jacket that prevents

dissolution while allowing nutrients to flow outward.

The fertilizer is administered either by top dressing the soil (or) by mixing the fertilizer into the

soil before sowing. One of the advantages of controlled release fertilizer is reduce incidence of

fertilizer burn.

Controlled release fertilizer is also known as Controlled Availability fertilizer, Delayed release

fertilizer, slow metered release fertilizer (or) slow acting fertilizer

Need of controlled release fertilizers

• Reduce risk of environmental losses.

• Nutrient release is controlled

• Improved fertilizer use efficiency, reduced fertilizer pollution in wastewater

• Coated fertilizers are excellent alternatives to soluble fertilizers because of slow release of

nutrients amidst the season.

• Plants can take up most of the nutrients without waste by leaching.

• Eliminating the need for multiple fertilizer applications

• Prolonged nutrient release can provide more uniform plant nutrition, better growth, and

improved plant performance

• Best efficiency of nutrient use

https://en.wikipedia.org/wiki/Granulated

https://en.wikipedia.org/wiki/Nutrient

https://en.wikipedia.org/wiki/Soil

https://en.wikipedia.org/wiki/Controlled_release


https://en.wikipedia.org/wiki/Permeability_(earth_sciences)



72 | P a g e

Three general categories:

• Uncoated controlled release

• Coated controlled release

• Bio Inhibitors

(i) Uncoated controlled release

• Urea formaldehyde reaction products:

Decompose in soil by chemical process, biological process (or) a combination of both

• Isobutylidene diurea(IBDU)

Relies slowly on soil chemical process to breakdown

• Inorganic Salts:

Magnesium ammonium phosphate

(ii) Coated controlled release

• Sulfur coated urea:

Release Nitrogen through oxidation of “S” coating

Used for Turf ferlilization

• Polymer coated urea (or) Poly-Coated urea

Urea is coated with special polymer coating. Water moves in through coating to dissolve

urea. Nitrogen diffuses out through porous polymer membrane



73 | P a g e

(iii) Bio Inhibitors

Inhibits microbial processes that convert Nitrogen into plant available forms

• Urease Inhibitors

• Nitrification Inhibitors

Urease Inhibitors

Urea is the most widely used form of N fertilizer, and can be formulated as dry granules,

prills, or as a fluid alone or mixed with ammonium nitrate (UAN). Urea is also present in animal

manures. All these forms of urea have the disadvantage of undergoing considerable losses as

ammonia gas if not incorporated into soil soon after application. Once dissolved in water, urea is

converted to ammonium bicarbonate within a few days following application by the naturally

occurring enzyme, urease.

Urease is produced by many soil microorganisms and plants, and is present in nearly all soils.

When urea is hydrolyzed by urease, much of the resulting ammonium is held on soil cation exchange

sites. During the conversion, the pH temporarily rises and ammonia gas is produced.

The loss of ammonia, termed volatilization, can be from nil to over 50%.

Urease Inhibitors Kill (or) chemically inhibits the activity of soil enzyme urease. This causes

the urea to not breakdown as quickly, providing time for rainfall to move urea into the soil. It inhibit

for 2 Weeks (or) more depending on conditions.

Soil enzyme

Urea NH4 + NH3

Nitrification Inhibitors

Nitrification is a natural process in soils that converts ammonium to nitrite and then to nitrate.

The soil bacteria Nitrosomonas spp. extract energy from ammonium by converting it to nitrite. A

second group of bacteria, Nitrobacter spp. then convert nitrite to nitrate.

Nitrosomonas Nitrobacter

NH4 + NO2 - NO3 –

Ammonium Nitrite Nitrate

Some compounds added to nitrogen (N) fertilizers can reduce the rate at which ammonium is

converted to nitrate. Under appropriate conditions, this can help reduce N losses through

denitrification and leaching.

4. Write in detail about fluid fertilizers.(Nov/Dec 2017)

Fluid Fertilizer is liquid fertilizer. They are popular because of the ease of handling and use.

Movement is by pump, and they usually require less labor to handle. Some pesticides can be injected

into the fluid, saving trips across the field. Fertilizers custom blended to specifications are available.

The major types of fluid fertilizers are suspension fertilizers and solution fertilizers. Main differences

between fluid and dry fertilizers are fluid fertilizer dissolve in water and dry fertilizers are not.

About one-third of all the nitrogen used in the US is applied as the fluid anhydrous ammonia and

an additional 20% is applied in the form of urea- ammonium nitrate solution.

Example:

A solution of urea (NH2CONH2) and Ammonium Nitrate (NH4NO3) Containing 28 & 32% N is the

most popular N Fluid Fertilizer

(i) Solution fertilizers Solution fertilizers are dissolved completely in water. Common solution fertilizerz are

Urea, UAN. Because of the urea content to avoid volatilities, losses of nitrogen to atmosphere.

Some constraints must follow while managing UAN



74 | P a g e

Solution fertilizers are low in potash because no more than 11 percent potash will go into

solution, and 9 % is more practical to manufacture. Most fluid fertilizers containing greater than 9 %

potash are suspension fertilizers.

Liquid UAN fertilizer is relatively simple to produce. A heated solution containing dissolved Urea is

mixed with a heated solution of Ammonium Nitrate to make a clear liquid fertilizer. Half of the total

‘N’ comes from the urea solution and half from Ammonium Nitrate solution.

(ii) Suspension fertilizers In suspension fertilizers, the plant food content exceeds the solubility of the system, and the

excess is present in the form of finely divided, suspension particle. All most all suspension fertilizers,

a suspending agent is inclined to prevent settling of the solid.

The suspending agent that is most cost effective, and hence most widely used is Atapulgite, swelling-

type clay composed mainly microscopic, needed like crystal of hydrated magnesium aluminium

silicate. Because of the absence of solubility retrains, suspension fertilizers are much more flexible

than solution fertilizer in regards to type and quantities

5. Write in detail about Bio-fertilizers.(Nov/Dec 2017)

A biofertilizer (also bio-fertilizer) is a substance which contains living microorganisms which,

when applied to seed, plant surfaces, or soil, colonizes the rhizosphere or the interior of the plant and

promotes growth by increasing the supply or availability of primary nutrients to the host plant.

Bio-fertilizers add nutrients through the naturalprocesses of nitrogen fixation, solubilizing phosphorus,

and stimulating plant growth through the synthesis of growth-promoting substances.

Biofertilizers are organisms that enrich the nutrient quality of soil. The main sources of

biofertilizers are bacteria, fungi, and cynobacteria (blue-green algae). The most striking relationship

that these have with plants is symbiosis, in which the partners derive benefits from each other.

• Symbiotic: The organisms live within the plants and help in the absorption of the fertilizers

like in the nodules of leguminous plants like groundnut, soyabean, pulses etc.

Ex: Rhizobium sp

• Associative symbiotic: These organisms live partly within the roots and partly outside crops

like paddy, sugarcane, cotton, millets, vegetables, etc. are benefited by those organisms

Ex: Azospirillum

• Non-symbiotic: These organisms live in the soil independent of the plants and fix N2

Ex: Azetobacter

Some important groups of Bio-fertilizers

1. Azolla-Anabena symbiosis: Azolla is a small, eukaryotic, aquatic fern having global

distribution. Prokaryotic blue green algae Anabena azolla resides in its leaves as a symbiont. Azolla is

an alternative nitrogen source. This association has gained wide interest because of its potential use as

an alternative to chemical fertilizers.

2. Rhizobium: Symbiotic nitrogen fixation by Rhizobium with legumes contributes substantially

to total nitrogen fixation. Rhizobium inoculation is a well-known agronomic practice to ensure

adequate nitrogen

Benefits of bio-fertilizers are:

1. These are means of fixing the nutrient availability in the soil.

2. Since a bio-fertilizer is technically living, it can symbiotically associate with plant roots.

Involved microorganisms could readily and safely convert complex organic material into

simple compounds, so that they are easily taken up by the plants. Microorganism function is in

https://en.wikipedia.org/wiki/Symbiotic



75 | P a g e

long duration, causing improvement of the soil fertility. It maintains the natural habitat of the

soil. It increases crop yield by 20-30%, replaces chemical nitrogen and phosphorus by 30%,

and stimulates plant growth. It can also provide protection against drought and some soil-borne

diseases.

3. Bio-fertilizers are cost-effective relative to chemical fertilizers. They have lower manufacturing

costs, especially regarding nitrogen and phosphorus use

Types of biofertilizers

• For Nitrogen

o Rhizobium for legume crops.

o Azotobacter/Azospirillum for non legume crops.

o Acetobacter for sugarcane only.

o Blue –Green Algae (BGA) and Azolla for low land paddy.

• For Phosphorous

o Phosphatika for all crops to be applied with Rhizobium, Azotobacter, Azospirillum and

Acetobacter

• For enriched compost

o Cellulolytic fungal culture

o Phosphotika and Azotobacter culture

S. No. Groups Examples

N2 fixing Biofertilizers

1. Free-living Azotobacter, Beijerinkia, Clostridium, Klebsiella,

Anabaena, Nostoc,

2. Symbiotic Rhizobium, Frankia, Anabaena azollae

3. Associative Symbiotic Azospirillum

P Solubilizing Biofertilizers

1. Bacteria

Bacillus megaterium var. phosphaticum, Bacillus

subtilis

Bacillus circulans, Pseudomonas striata

2. Fungi Penicillium sp, Aspergillus awamori

P Mobilizing Biofertilizers

1. Arbuscular mycorrhiza Glomus sp.,Gigaspora sp.,Acaulospora sp.,

Scutellospora sp. & Sclerocystis sp.

2. Ectomycorrhiza Laccaria sp., Pisolithus sp., Boletus sp., Amanita sp.

3. Ericoid mycorrhizae Pezizella ericae

4. Orchid mycorrhiza Rhizoctonia solani

Biofertilizers for Micro nutrients

1. Silicate and Zinc solubilizers Bacillus sp.

Plant Growth Promoting Rhizobacteria

1. Pseudomonas Pseudomonas fluorescens


https://en.wikipedia.org/wiki/Phosphorus



76 | P a g e

Precautions one should take for using biofertilizers

• Biofertilizer packets need to be stored in cool and dry place away from direct sunlight and heat.

• Right combinations of biofertilizers have to be used.

• As Rhizobium is crop specific, one should use for the specified crop only.

• Other chemicals should not be mixed with the biofertilizers.

• While purchasing one should ensure that each packet is provided with necessary information

like name of the product, name of the crop for which intended, name and address of the

manufacturer, date of manufacture, date of expiry, batch number and instructions for use.

• The packet has to be used before its expiry, only for the specified crop and by the recommended

method of application.

• Biofertilizers are live product and require care in the storage

• Both nitrogenous and phosphatic biofertilizers are to be used to get the best results.

• It is important to use biofertilizers along with chemical fertilizers and organic manures.

• Biofertilizers are not replacement of fertilizers but can supplement plant nutrient requirements.

Advantages of bio-fertilizers

• Cost effective.

• Supplements to fertilizers.

• Eco-friendly (Friendly with nature).

• Reduces the costs towards fertilizers use, especially regarding nitrogen and phosphorus.

• Renewable source of nutrient

• Replace 25 to 30% chemical fertilizer

• Solubilize and mobilize nutrients

• Sustain soil health

vel tech high tech dr.rangarajan dr.sakunthala engineering

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