THERMAL PROCESSTHERMAL PROCESS

1. Electric Furnace Process1. Electric Furnace Process

a. Direct conversion at plant sitea. Direct conversion at plant site

b. Oxidation and Hydration of Elemental b. Oxidation and Hydration of Elemental PhosphorousPhosphorous

2. Blast Furnace Process 2. Blast Furnace Process

`̀CombustionCombustion

ChamberChamber

Phosphate Rock

Air

H2O

Co for Fuel orSynthesis gas

Water SprayCondenser

Fines Recycle

ElectroStatic Precipitator

Fines To Fines To Waste` Waste`

Coke BreezeCoke Breeze Sand

250-300v250-300v3 Phase 3 Phase AC PowerAC Power

P4,CO,Dust

Air cooledAir cooled

Crushed SlagCrushed Slag

P2O5

Route

Bone dry air via silica Bone dry air via silica gelgel

Com

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Com

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CO

Flu

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Flu

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Con

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Con

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Phosphoric AnhydrideP2O5

AmbientAmbientAir(Not Dried)Air(Not Dried)

SintenerSintenerScreenScreen

H2O

H2O

SlagSlag

1400 C1400 C

Electric Electric furnacesfurnaces

CO

SludSludgege

HH22SS

Puri

fica

tion

P

roce

ss

PowderedPowdered SiOSiO22

HH22SOSO44

Purified 85%Purified 85% HH33POPO44

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Yellow Yellow PhosphorousPhosphorous storagestorage

ELECTRIC FURNACE METHOD

PHOSPHOROUSPHOSPHOROUS

INTRODUCTION:INTRODUCTION:

Phosphorous in elemental form Phosphorous in elemental form and its many products is derived and its many products is derived from commercial deposits of from commercial deposits of phosphate rock in the mineral phosphate rock in the mineral form Fluorapatite [Caform Fluorapatite [Ca1010(PO(PO44))66FF22].].

PHYSICAL PROPERTIES

YELLOW PHOSPHOROUS

• Mol wt. = 123.9

• Melting Point = 44.1˙C

• Boiling Point = 280˙C

• Density (gm\cc): Solid = 1.82 Liquid = 1.74

RED PHOSPHOROUS

• Mol wt. = 123.9

• Melting Point = 593˙C

• Density (gm\cc): Solid =

2.36

RAW MATERIALSRAW MATERIALS

Phosphate RockPhosphate Rock Conc. HConc. H22SOSO44

WaterWater

CHEMICAL REACTIONSCHEMICAL REACTIONS

2 Ca2 Ca33(PO(PO44)2 + 6 SiO)2 + 6 SiO22 + 10 C -> P + 10 C -> P44 + 10 CO + 6 CaSiO+ 10 CO + 6 CaSiO33

PP44 + 10 CO + 10 O + 10 CO + 10 O22 -> 2 P -> 2 P22OO55 + 10 + 10 COCO22

PP22OO55 + 2 CH + 2 CH22O -> 2 HO -> 2 H33POPO44 + (x-3) + (x-3) HH22OO

`̀

Phosphate Rock

Air

Co for Fuel orSynthesis gas

Water SprayCondenser

Fines Recycle

ElectroStatic Precipitator

Fines To Fines To Waste` Waste`

Coke BreezeCoke Breeze Sand

250-300v250-300v3 Phase 3 Phase AC PowerAC Power

P4,CO,Dust

Air cooledAir cooled

Crushed SlagCrushed Slag

P2O5

Route

Bone dry air via silica Bone dry air via silica gelgel

Com

bu

sti

on

Com

bu

sti

on

c

ham

ber

ch

am

ber

CO

Flu

id B

ed

Flu

id B

ed

Con

den

ser

Con

den

ser

Phosphoric AnhydrideP2O5

SintenerSintenerScreenScreen

H2O

H2O

SlagSlag

1400 C1400 C

Electric Electric furnacesfurnaces

Yellow Yellow PhosphorousPhosphorous storagestorage

PRODUCTION OF P,P2O5

VARIOUS STEPS INVOLVEDVARIOUS STEPS INVOLVED

GroundingGroundingScreeningScreeningElectric FurnaceElectric FurnaceChemical ReactionsChemical ReactionsMolten slagMolten slag

GROUNDINGGROUNDING

Phosphate rock is ground, mixed with Phosphate rock is ground, mixed with a portion of the coke requirement, a portion of the coke requirement, then sintered into nodules to obtain then sintered into nodules to obtain better electrical resistivity better electrical resistivity characteristics and to avoid fines in characteristics and to avoid fines in the released P4the released P4 and CO papersand CO papers. .

SCREENINGSCREENING

Screening is necessary to maintain Screening is necessary to maintain size control with the fines recycled to size control with the fines recycled to the sintering operation. Coke breeze the sintering operation. Coke breeze and sand are mixed in controlled and sand are mixed in controlled quantities based on phoshpate rock quantities based on phoshpate rock analysis.analysis.

ELECTRIC FURNACEELECTRIC FURNACE

The electric furnace is 250-300V AC –The electric furnace is 250-300V AC –three phase design with power fed to three phase design with power fed to one 100-150 cm diameter carbon one 100-150 cm diameter carbon electrode on each phase. The feed electrode on each phase. The feed charge drops gradually in to the charge drops gradually in to the fused section of the furnace at 1400-fused section of the furnace at 1400-1450˙C where the reduction to 1450˙C where the reduction to elemental phosphorous takes place.elemental phosphorous takes place.

CHEMICAL REACTIONS

The furnace is kept under slight vacuum by fans in the down-stream end of the plant, so the furnace gases moves past an electrostatic precipitator to remove dust and then to a water cooled condenser. Liquid yellow phosphorous is collected under water for further processing. CO (2.5-3 tons\tons P) is used as fuel or for synthesis gas after clean up. The mixture is fed to top of electric furnace.

MOLTEN SLAGMOLTEN SLAG

The Molten slag (8 tons\ton of P) from the The Molten slag (8 tons\ton of P) from the bottom of the furnace is tapped periodically, bottom of the furnace is tapped periodically, cooled and crushed for road bed gravel, soil cooled and crushed for road bed gravel, soil liming and glass manufacture. Where Ferro liming and glass manufacture. Where Ferro phosphorous by-product is a substantial part of phosphorous by-product is a substantial part of the slag, either due to high iron content rock or the slag, either due to high iron content rock or from scrap iron slugs added intentionally, the from scrap iron slugs added intentionally, the slag must be processed to separate this slag must be processed to separate this valuable material. It is sold as an alloy steel valuable material. It is sold as an alloy steel additive and for weighing agents in oil additive and for weighing agents in oil drilling(muds).drilling(muds).

MAJOR ENGINEERING PROBLEMSMAJOR ENGINEERING PROBLEMS

►Electric furnace design:Electric furnace design: High voltage with large reaction zone High voltage with large reaction zone

desirable to reduce the electrodes and desirable to reduce the electrodes and transformer system for the same input. This transformer system for the same input. This saves money on power equipment and saves money on power equipment and electrode purchases.electrode purchases.

►Safety in handling P:Safety in handling P: Most of the yellow P is converted in to Most of the yellow P is converted in to

H3PO4. It is bulk shipped by tankage via H3PO4. It is bulk shipped by tankage via boat, rail and truck. Water is kept over the boat, rail and truck. Water is kept over the top surface to avoid direct contact with air top surface to avoid direct contact with air since yellow phosphorous oxidizes vigorously.since yellow phosphorous oxidizes vigorously.

APPLICATIONS

Phosphorus being an essential plant nutrient, finds its major use as a constituent of fertilizers for agriculture and farm production in the form of concentrated phosphoric acids, which can consist of 70% to 75% P2O5. Global demand for fertilizers led to large increase in phosphate (PO43-) production in the second half of the 20th century.

Phosphorus is widely used to make organophosphorus compounds, through the intermediates phosphorus chlorides and the two phosphorus sulfides: phosphorus pentasulfide, and phosphorus sesquisulfide.[1] Organophosphorus compounds have many applications, including in plasticizers, flame retardants, pesticides, extraction agents, and water treatment.

APPLICATIONS

Phosphates are utilized in the making of special glasses that are used for sodium lamps.

Bone-ash, calcium phosphate, is used in the production of fine china. Sodium tripolyphosphate made from phosphoric acid is used in laundry

detergents in some countries, but banned for this use in others. Phosphoric acid made from elemental phosphorus is used in food applications

such as some soda beverages. The acid is also a starting point to make food grade phosphates.[1] These include mono-calcium phosphate which is employed in baking powder and sodium tripolyphosphate and other sodium phosphates[1]. Among other uses these are used to improve the characteristics of processed meat and cheese. Others are used in toothpaste.[1] Trisodium phosphate is used in cleaning agents to soften water and for preventing pipe/boiler tube corrosion.

White phosphorus is used in military applications as incendiary bombs, for smoke-screening as smoke pots and smoke bombs, and in tracer ammunition.

Red phosphorus is essential for manufacturing matchbook strikers, flares,[1] safety matches, pharmaceutical grade and street methamphetamine, and is used in cap gun caps.

Phosphorus sesquisulfide is used in heads of strike-anywhere matches.[1] In trace amounts, phosphorus is used as a dopant for N-type semiconductors. 32P and 33P are used as radioactive tracers in biochemical laboratories (see

Isotopes

MANUFACTURE OF H3PO4

Direct conversion at plant site

`̀CombustionCombustion

ChamberChamber

Phosphate Rock

Air

H2O

Fines Recycle

ElectroStatic Precipitator

Fines To Fines To Waste` Waste`

Coke BreezeCoke Breeze Sand

250-300v250-300v3 Phase 3 Phase AC PowerAC Power

P4,CO,Dust

Air cooledAir cooled

Crushed SlagCrushed Slag

P2O5

Route

AmbientAmbientAir(Not Dried)Air(Not Dried)

SintenerSintenerScreenScreen

SlagSlag

1400 C1400 C

Electric Electric furnacesfurnaces

CO

SludSludgege

HH22SS

Puri

fica

tion

P

roce

ss

PowderedPowdered SiOSiO22

HH22SOSO44

Purified 85%Purified 85% HH33POPO44

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PRODUCTION OF H3PO4

STRUCTURE OF HSTRUCTURE OF H33POPO44

Molecular formula H3PO4

Molar mass 98.0 g/mol

Appearancewhite solid orcolorless, viscous liquid (>42°C)

Density 1.685 g/ml (liquid)

Melting point 42.35 °C, 316 K, 108 °F

Boiling point158 °C, 431 K, 316 °F (decomp.)

Acidity (pKa) 2.12, 7.21, 12.67

Viscosity85% aqueous solution 

PHYSICAL PROPERTIES

RAW MATERIALSRAW MATERIALS

Crushed Phosphate rockCrushed Phosphate rock CokeCoke SandSand HH22SOSO44

HH22OO

CHEMICAL REACTIONSCHEMICAL REACTIONS

2 Ca2 Ca33(PO(PO44)2 + 6 SiO)2 + 6 SiO22 + 10 C + 10 C —>—> PP44 + 10 CO + 6 CaSiO + 10 CO + 6 CaSiO33

PP44 + 10 CO + 10 O + 10 CO + 10 O22 —>—> 2 P 2 P22OO55 + + 10 CO10 CO22

PP22OO55 + 2 CH + 2 CH22O O —> —> 2 H2 H33POPO44 + (x-3) + (x-3) HH22OO

PROCESS DESCRIPTIONPROCESS DESCRIPTION

The first part of the electric furnace process is The first part of the electric furnace process is identical with that described under identical with that described under phosphorous until the vapors leave the phosphorous until the vapors leave the furnace. The oxidation of these gases is furnace. The oxidation of these gases is accomplished by an air combustion section accomplished by an air combustion section downstream section from the furnace exit. downstream section from the furnace exit. The P2O5 thus formed is removed by The P2O5 thus formed is removed by spraying the hot gases with water. Some mist spraying the hot gases with water. Some mist is formed which is next removed by a is formed which is next removed by a scrubbing system.scrubbing system.

The crude 85% acid is given an H2SO4 The crude 85% acid is given an H2SO4 treatment to remove CaSo4,a powdered silica treatment to remove CaSo4,a powdered silica addition to remove HF and H2S to remove addition to remove HF and H2S to remove AsS3.The sludge is then removed.AsS3.The sludge is then removed.

MAJOR ENGINEERING PROBLEMSMAJOR ENGINEERING PROBLEMS

► Complete removal of acid mist:Complete removal of acid mist:

By purely fluid mechanics designs, a system By purely fluid mechanics designs, a system which includes Pease-Anthony scrubber, which includes Pease-Anthony scrubber, screens and final water spray has been screens and final water spray has been successfully adopted.successfully adopted.

► Materials of construction:Materials of construction:

High temperature acid brick is used in the High temperature acid brick is used in the furnace and combustion chamber areas. The furnace and combustion chamber areas. The electrostatic precipitator is graphite to resist electrostatic precipitator is graphite to resist the action of the free HF steel present.the action of the free HF steel present.

APPLICATIONS

Phosphoric acid is used as the electrolyte in phosphoric-acid fuel cells. It is also used as an external standard for phosphorus-31 nuclear magnetic resonance (NMR).

Phosphoric acid is used as a cleaner by construction trades to remove mineral deposits, cementitious smears, and hard water stains. It is also used as an ingredient in some household cleaners aimed at similar cleaning tasks.

Hot phosphoric acid is used in microfabrication to etch silicon nitride (Si3N4). It is highly selective in etching Si3N4 instead of SiO2, silicon dioxide. [8]

APPLICATIONS

Phosphoric acid is used as a flux by hobbyists (such as model railroaders) as an aid to soldering.

Phosphoric acid is also used in hydroponics pH solutions to lower the pH of nutrient solutions. While other types of acids can be used, phosphorus is a nutrient used by plants, especially during flowering, making phosphoric acid particularly desirable. General Hydroponics pH Down liquid solution contains phosphoric acid in addition to citric acid and ammonium bisulfate with buffers to maintain a stable pH in the nutrient reservoir.

Phosphoric acid is used as a pH adjuster in cosmetics and skin-care products.[9]

Phosphoric acid is used as a chemical oxidizing agent for activated carbon production.[10]

Phosphoric acid is also used for High Pressure Liquid Chromotography.

MANUFACTURE OF H3PO4

OXIDATION AND HYDRATION OF ELEMENTAL PROCESS

RAW MATERIALSRAW MATERIALS

Elemental phosphorousElemental phosphorous Steam Steam AirAir

CHEMICAL REACTIONSCHEMICAL REACTIONS

2 P + 2 ½ H2 P + 2 ½ H220 —> P0 —> P22OO55

PP22OO55 + 3 H + 3 H22O —> 2 HO —> 2 H33POPO44

PROCESS DESCRIPTIONPROCESS DESCRIPTION

Phosphorous is melted at 50˙C and metered by Phosphorous is melted at 50˙C and metered by water displacement to a steam ejector and water displacement to a steam ejector and atomization section of the combustion nozzle. atomization section of the combustion nozzle. Compressed air is injected around steam Compressed air is injected around steam atomized phosphorous droplets and the atomized phosphorous droplets and the exothermic reaction rises the gas temperature to exothermic reaction rises the gas temperature to 2000˙C.the entire chamber is about 1.2m 2000˙C.the entire chamber is about 1.2m diameter and 3m long and is built of stainless diameter and 3m long and is built of stainless steel with water cooled walls.steel with water cooled walls.

The gaseous oxides, partially hydrated, are The gaseous oxides, partially hydrated, are treated for conversion of electric furnace gas to treated for conversion of electric furnace gas to 85%H85%H33POPO44..

MAJOR ENGINEERING PROBLEMSMAJOR ENGINEERING PROBLEMS

► The combustion chamber design and operation The combustion chamber design and operation for molten P4 feed required a great deal of for molten P4 feed required a great deal of development.development.

► Under improper operation, a glassy type of Under improper operation, a glassy type of metaphosphoric acid and its polymers can form metaphosphoric acid and its polymers can form and drop to the bottom of the chamber, and drop to the bottom of the chamber, necessitating frequent shut down and clean necessitating frequent shut down and clean out.out.

► By placing the combustion chamber near the By placing the combustion chamber near the bottom a great deal of the metaphosphoric acid bottom a great deal of the metaphosphoric acid can be vaporized and passed overheadcan be vaporized and passed overhead..

APPLICATIONSAPPLICATIONSMetal finishingMetal finishing Phophatizing compounds for Phophatizing compounds for

rustproofing,as the major ingredient in rustproofing,as the major ingredient in solutions used for the chemical & solutions used for the chemical & electrochemical polishing of electrochemical polishing of aluminium,stainless steel & copper alloys.aluminium,stainless steel & copper alloys.

Chemical Chemical manufacturemanufacture

Production of phosphate saltsProduction of phosphate salts

Equipment Equipment maintenancemaintenance

Descaling of boilers and heat exchanger Descaling of boilers and heat exchanger tubestubes

Ceramics & GlassCeramics & Glass Petroleum polymerization of propylene ; Petroleum polymerization of propylene ; alkylating catalyst.alkylating catalyst.

PlasticsPlastics As catalyst to speed up setting action of As catalyst to speed up setting action of some synthetic resins.some synthetic resins.

Drinking water Drinking water treatmenttreatment

Food grade acid used for corrosion controlFood grade acid used for corrosion control

A PRESENTATION BYA PRESENTATION BY

VIRUDHAGIRI.MVIRUDHAGIRI.M VINOTHRAJ.MVINOTHRAJ.M TAMILSELVAMTAMILSELVAM SORNALINGAM.MSORNALINGAM.M BABU KANNANBABU KANNAN DEEPAK KUMARDEEPAK KUMAR YUVANASHREE.EYUVANASHREE.E SURYAKALA.MSURYAKALA.M SINDHUJA.SSINDHUJA.S SINDU.SSINDU.S