MALAVIYA NATIONAL INSTITUTE OF TECHNOLOGY JAIPUR

CHLOR ALKALI PLANT

PRESENTED BY:-

RAJENDRA SINGH SHEKHAWAT0607632

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IntroductionBrine HouseCell HouseLiquid Chlorine HouseChlorine BottlingHCL plantFusion House Stable Bleaching PowderSodium Hypochloride section

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Agri Businesses: Sugar, Urea, Agri Inputs, Shriram Bioseed, and Hariyali Kisaan Bazaar

Energy Intensive Businesses: Chemicals, PVC Resins, Cement

Value Added Businesses: Fenesta Building Systems, PVC Compounds, and Energy Services

The main business units of DSCL are:-

Products are caustic soda lye & flakes, liquid and gaseous chlorine, hydrochloric acid, stable bleaching powder, compressed hydrogen and sodium hypochlorite.

DSCL is the third largest manufacturer of Chlor-Alkali in the country with manufacturing facilities at Kota, Rajasthan (1, 08,500 TPA) and at Bharuch, Gujarat (62,500 TPA) both based on the membrane cell technology.

The company also has 12.5 million cubic meters bottling capacity for Hydrogen produced at the complex and a 9,900 TPA capacity for stable bleaching powder.

DSCL is both one of the lowest cost and most efficient manufacturers of Chlor-alkali in the country as DSCL believes in integrated manufacturing.

DSCL has a large consumption of chlorine within manufacturing facilities, they use it to produce other value added products.

The Chemicals business being highly energy intensive is vulnerable to the availability and cost of power with such costs constituting two-thirds of all direct costs. DSCL has in place a reliable and uninterrupted source of captive power with a coal-based facility at Kota.

Three different methods to produce chlorine and NaOH mercury cell diaphragm cell membrane cell

The membrane cell is the most modern and has economic and environmental advantages

INTRODUCTION

In brine house impurities of brine are removed. Calcium Magnesium and Sulphate ions are three

major impurities in brine Two major section of brine house are

primary purification secondary purification

Brine House

The primary brine purification section consists of:

Salt Conveyor Salt Saturator Reactor Brine Clarifier Clarified Brine Tank Anthracite Filter Filter Brine Tank

Primary purification includes salt saturation, chemical dosing, reaction and sedimentation

NaOH , Na2CO3 , BaCO3 are used for magnesium, calcium and sulphate ions respectively.

Reactions are MgCl2 + 2NaOH Mg(OH)2 + 2NaCl CaCl2 + Na2CO3 CaCO3 + 2NaCl CaSO4 + BaCO3 BaSO4 + 2CaCO3

Primary purification

Flocculant added is Magnafloc 611 pH of inlet to brine clarifier should be

9.5(controlled by NAOH fed to brine) Brine clarifier converts the amount of impurities

present in brine from ppm level to ppb level. Sludge circulation is done It is then sent to anthracite filter Anthracite filter reduces its turbidity from5 to 1.5

NTU Anthracite filter consists of a bed of powdered

anthracite which filters the brine and reduces its turbidity

Brine Clarification

Secondary purification section consists of two major section

Schumacker Filter Ion-exchange Column

Schumacker filter reduces the amount of magnesium(180 to 16 ppb) and turbidity(1.5 to .2 NTU)

In ion exchange column, resin ions are replaced by Ca+2 ,Mg+2

Schumacker is made of polypropylene leaves covered with polypropylene cloth.

This filter consists of candles present inside it which are u candles are coated with α-cellulose prepared in the pre-coat

tank, in the form of aqueous slurry Washing and pre-coating are carried out automatically

according to the time table(72 hours or P diff. 2 kg/cm2). The α-cellulose and suspended particles are blown down to Lagoon pit.

This filter reduces the amount of magnesium and iron present to a very lower level i.e. 180ppb to 16ppb and 30ppb to 11ppb respectively

The bulk density of α-cellulose is about 300 kg/m3 and it is composed of CaCO3, Mg(OH)2, BaSO4.

Schumacker Filter

There are three ion-exchange columns present from which normally two remain in line in series.

The resin used is a cation exchange resin. Na+ ions in the resin replace the other metal ions present in the brine, specifically with the divalent cations

A small part of the ion exchange resin is broken and deformed to smaller particle during operation so backwashing with DM water

Calcium ions are very harmful to the membrane electrolysis process.

. These columns reduce the amount of Ca2+ ion present from about 1050ppb to 5ppb.

Ion-exchange columns

Reaction in ion exchange column:- 2 RCH2NHCH2PO3Na2 + Ca++ →

(RCH2NHCH2PO3)2CaNa2+2Na+

The reactions that take place during the regeneration are-By HCl(RCH2NHCH2PO3)2CaNa2 + 4 HCl →

RCH2NHCH2PO3H2 + CaCl2 + 2 NaCl

 By NaOHRCH2NHCH2PO3H2 + 2 NaOH →

RCH2NHCH2PO3Na2 + 2 H2O

the resin volume shrinks about 10-20 %, due to exposure to brine and adsorption of acid multivalent cations.

The other feature is that the relative volume of the resin in Na-Na form is about 1.2-1.4 times of that in H form. This means the resin swells during regeneration by caustic soda.

In treatment with HCl, excess amount of HCl solution is required to ensure regeneration reaction

The brine coming out of ion exchange columns is ultra pure.

Resin used in columns is styrene-divinyl-benzene-copolymer with amino-phosphoric acid group

The resin present has the following properties: Shape - Sphere Specific Gravity - 1.12 (Na form) Apparent Density - 700-800 g/l Operating Temperature - 50-65°C Operating pH range - 9-12 Relative easiness of replacement of ions Cu++ > Pb++ > Fe++ > Zn++ > Ca++ > Cd++ > Mg++ >

Ni++ > Sr++ > Ba++ > Na+

The specification of the ultra pure brine is as follows: NaCl - 305±5 g/l at 15°C pH - 10-11 Temperature - 60°C Ca++ + , Mg++ - < 0.020 mg/l Na2SO4 - < 7 g/l as SO4

Al - < 0.1 mg/l SiO2 - < 5 mg/l I - < 0.1 mg/l Sr - < 0.1 mg/l Fe - < 0.05 mg/l Ba - < 0.1 mg/l Ni - < 0.01 mg/l Suspended solid - < 1.0 mg/l Free Cl2 - none

It is the most important part of chlor alkali plant We use membrane cell technology in this plant A perfluorocarboxilate Membrane is used. There are five electrolysers and 150-cell units in

the cell house

Cell house

one electrolyser is made up of 74*2 bipolar cell frames .two anode terminal cell

frames and two cathode terminal cell frames. 150 sheets of ion exchange membrane. 150 sets of gasket One press unit to press mounted cell frames Inlet sub header for feeding anolyte and catholyte. Outlet sub header s for collecting electrolyzed products. 150*4 flexible hoses for connecting cells with sub

header. Two hydraulic blocks which control oil pressure to

hydraulic cylinders

Anolyte compartment is made up of Titanium to give resistance to chlorine.

Catholyte compartment is made up of Nickel to give resistance to caustic soda with high temperature and high concentration.

Anode is welded on Titanium ribs of anolyte compartment and cathode is welded on Nickel ribs of catholyte compartment.

Both have one inlet nozzle, one outlet nozzle and gas separation chamber on top of cell frame.

Anolyte part A part of Depleted brine is fed to purified

brine in order to supply free chlorine in feed brine which protects Titanium inlet sub header from HCl.

Catholyte circulation part

Chemical Reactions:-

At Anode: Cl- → ₂Cl⅟ 2 + e-

At Cathode: H2O + e- → ₂H⅟ 2 + OH-

Net reaction: NaCl + H2O → NaOH + ₂H⅟ 2 + ₂Cl⅟ 2

Selective permeation of Na+ Precipitate of metal hydroxide If there are metal cations such as Ca++, Mg++, Fe+++, Al+++, Ni++,

and Ba++ in the anolyte, they will precipitate in the membrane as hydroxides

Salt blister and Water blister To prevent salt blister formation, it is important not to make and area

non-conductive by gasket protection. Pressure difference across membrane 0.4m H2O of pressure difference is applied between catholyte and anolyte

compartments. Temperature of electrolyte Acidity of anolyte and performance of membrane If the carboxylic group is charged into –COOH type, it cannot work as an ion

exchange membrane

Product Caustic soda concentration Maximum 35%w/w as chemically

decarboxylation occurs if high temperature or conc.

Exit brine conc. is 210 gpl

DEPLETED BRINE TANK It is made up of Titanium. Cl2 gas is present in free form in

depleted brine. The concentration of this brine is at about 210g/l. This brine is sent to the de-chlorination tower to get it free from the chlorine present in it.

HYDROGEN GAS TREATMENT WASHING TOWER COOLING TOWER The efficiency of cooling tower is dependent on the difference of outlet

temperature of water and wet bulb temperature DE-CHLORINATION TOWER Depleted brine contains 700-800 mg/l of Cl2. This Cl2 exists in

three forms- Cl2, HClO and ClO- in the brine depending on its pH.

Chlorine scrubber Cooler Drying tower Compressor Separator Mist eliminator Freon compressor Liquefier Liquefaction Vapour absorption machine (VAM)

Liquid Chlorine house

The LiBr-water absorption system works on the following physical properties- The B.P. of water is a function of pressure at atm. pressure; water boils at 100°C. At

the lower pressure, it will boil at lower temperature. The B.P. of the water at 6 mm Hg absolute pressure is 4°C. The LiBr salt has strong chemical affinity to water; higher the concentration of LiBr, stronger is its affinity to water; at high temperature, its affinity decreases.

There is a large difference between the vapour pressure of LiBr and water. In this, the generator is flooded type and as solution gets heated (by waste heat or steam) water is driven out, resulting in the LiBr solution getting concentrated. The temperature in the generator is likely to be about 125°C to 160°C. Depending on the refrigeration load, the water vapours move and is condensed in the condenser. The temperature and pressure in condenser is about 45°C and 75 mm of Hg respectively.

The concentrated hot LiBr solution leaving the generator is cooled in heat exchangers by dilute, cold LiBr solution entering the generator. The cooled, concentrated LiBr solution is sprayed on the tubes containing the process water, which has tubes, filled. The water evaporates at 6mm Hg absolute pressure and 4°C temperature prevailing in the evaporator- absorber, the concentrated LiBr absorbs the evaporating water vapour and collects as dilute, cold LiBr solution, the heat of solution is removed by cooling water. The dilute solution pump through the heat exchangers pumps the dilute LiBr solution to the generation. The cycle continues in a same way.

Vapour absorption machine (VAM)

Chlorine ton container is a cylindrical vessel with overall length around 2080 mm having both ends convex inside. This special shape of dished ends provides built in safety against increase in pressure.

The design pressure is 19.9kg/cm2 and design temperature is 65°C.

It is fabricated for 100% radiography for all welded joints and the container is finally stress relieved

The steel for construction of chlorine containers should be good quality steel free from cracks, laminations or other defects injurious to the finished vessel

, owing to the use of inverted dished ends (pressure on the convex side) in the vent of increase in internal pressure, the dished ends reverse thus increasing the volume of the containers and decreasing the internal pressure.

Chlorine Bottling Section

Chlorine has characteristics pungent smell. This gas can be detected even at very low concentration of 3ppm in air.

Leakage points can be further physically identified with the help of swab dipped in aqueous ammonia. Chlorine reacts with ammonia and forms a white smoke. This enables us to pin point the leakage

DETECTION OF LEAKAGE

Production of HCl acid in a concentration range of 1 to 38% HCl from chlorine and hydrogen, using water or weak HCl acid as the absorbing liquid.

As an HCl recovery measure, HCl gas from other plants can be fed into the synthesis unit and absorbed together with the synthesized gas.

Chlorine-containing residual gas or “sniff gas” from other processes can be recycled to produce HCl.

Weak HCL acid can be fed into the absorber and brought up to the required acid concentration.

HCL Plant

Complete combustion of Cl2 and H2 in synthesis burner to produce HCl takes place. The HCl gas, at a temperature of 2000 to 2500°C, flows from the combustion chamber into an integrated absorber.

The HCL gas is then absorbed by water or weak acid. The absorber is either co-current or counter-current depending on the type of synthesis unit.

The HCL acid is normally produced with less than 1ppm free chlorine. By adjusting the absorption water (weak acid) supply rate, the desired HCl concentration can be obtain.

The product acid flows by gravity into a tank at atmospheric pressure. The starting substances for the synthesis are hydrogen and chlorine.

Hydrogen and chlorine are fed into a burner at controlled rates. The burner consists of two concentric tubes with chlorine flowing through the inner tube and hydrogen through the outer annulus. Above the burner, the gases are ignited to produce HCl gas. A hydrogen flow of at least 5% stoichiometric excess is recommended to ensure that a complete synthesis takes place.

Bleaching powder is manufactured from high-grade hydrated lime and liquid chlorine.

High grade hydrated lime of min. 92% calcium hydroxide is chlorinated under controlled condition and vacuum using liquid chlorine in a special rotating jacketed cylinder called chlorination drum. The main reaction used to manufacture bleaching powder is carried out at temperature below 50°C. In a counter-current fashion by passing liquid chlorine through chlorination drums with inner lifting blades, which shower the hydrated lime solids in the path of the chlorine.

The bleaching powder is accompanied by strong heat generation. The absorption of 1kg chlorine liberates about 26kcal of heat. The liberated heat is partly removed by jacket cooling water, partly by the coincident evaporation of the formed water due to reaction and partly by the heat of evaporation of the liquid chlorine.

Stable Bleaching Powder

Slaked lime redler type elevator Screw conveyor and slaked lime rotary

feeders Slaked lime feed hoppers Chlorination Drum Product bunker Moleculator

It is horizontal cylindrical vacuum paddle drier drum of internal diameter of 2.2m, an internal length of 6m and a volume of about 20m3.

The cylindrical part of the drum is jacketed, where the jacket can be used for drying as well as cooling. For the introduction of liquid chlorine, 6 nozzles (50mm dia.) are provided and lengthwise on the bottom of the drum. Out of the six nozzles, only four are used for the injection of liquid chlorine and other two are used for temperature measurement of material inside the drum. A dome is provided at the center of the top of the admitting the calcium hydrate.

The paddle stirrer is drier by a motor via toothed gear it runs with a speed of 6 rpm. The finished dry bleaching powder is removed through a bottom opening, which is located in the center

Chlorination Drum

Concentrate the caustic soda solution from 47.5% to 96.5%

Hydrogen gas is also used as fuel to save fuel oil consumption

140°C to 380°C is the temperature of the 1st pot to 6th pot

after 6 pot,molten NaOH gets solidified as a film over the drum surface.

Fusion House

caustic is mainly used in the manufacture of pulp and paper, newsprint, viscose yarn, staple fiber, Aluminum, cotton, textiles, toilet and laundry soaps, detergents, dyestuffs, drugs and pharmaceuticals, vanaspati, petroleum refining. Caustic soda is produced in two forms - lye and solids (flakes or granules)

chglorine is used in the manufacture of products like vinyl’s, pharmaceuticals, water disinfectants, agrochemicals, additives in oil and detergents, refrigerants, photographic chemicals, adhesives, inks and coatings

Uses

Convert chlorine in waste gas to hypo

Sodium Hypochloride Section

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