SHROFF S.R. ROTARY INSTITIUTE OF CHEMICAL TECHNOLOGY Chemical Process Industries-I Prepared by: 1.Pratik Lakkad ( ) 2.Meet Rojivadiya ( ) 3.Yagnesh Savaliya ( )

Properties:

Salt1.55 tons Limestone1.2 tons Coke0.09 ton High pressure steam1.35 tons Low pressure steam1.60 tons Ammonia losses1.5 kg Cooling water40-60 tons Electric power210 KWH

Process description

Development of suitable calcining equipment Ammonia recovery Waste disposal Economics balance on tower design Major Engineering Problems

Salt1.26 tons ton High pressure steam1.35 tons Low pressure steam0.10 ton Cooling water50-80 tons Electric power450 KWH Co-product

Process description

Major Engineering Problems In addition to calcining and economic tower balance on tower design as mentioned in Solvay process Salt purification Corrosion Refrigeration

These two chemicals are being discussed together as they are produced as co- products in the electrolysis of brine. This process accounts for 80% of caustic soda and > 95% of chlorine production. Chlorine: Chlorine is an essential component in many industrial and commercial applications. Chlorine is a greenish-yellow gas with a pungent and irritating odour. It is a very active element that is found in nature only in combination with other elements. Chlorine in its elemental form is a very powerful oxidant, and chlorine containing compounds are used to keep swimming pools clean and sanitary, protect food and crops, design pharmaceuticals, and make plastics. Liquid chlorine vaporizes quickly under normal atmospheric conditions. Ordinary table salt, sodium chloride, is the chief source of chlorine.

Caustic Soda: Caustic soda is an essential ingredient in an array of industrial applications. In addition, consumers use caustic soda when using cleaners, such as oven and drain cleaners Caustic soda is highly corrosive and reactive. Caustic soda can be irritating to the skin, eyes and gastrointestinal tract. Occupational and consumer exposure is dependent upon the conditions under which caustic soda is used. Although caustic is only slightly toxic to aquatic organisms, a large discharge can change the pH of the aquatic system which may be toxic to aquatic organisms.

Molecular Weight70.9 g/mole Melting Point Boiling Point Liquefaction Point Toxic gas0.35 – 2.0 ppm is max conc. Grades99.0% Critical Temperature Critical Pressure93.5 atms

Properties of Caustic Soda [ NaOH] Molecular Weight40.00 g/mole AppearanceWhite, waxy, opaque crystals OdourOdourless Density2.13 g/cc Melting Point Boiling Point Solubility in water High solubility and high exothermic heat of solution Acidity13 Refractive index1.3576

Classification of Processes

Salt1.3 tons Soda ash26kg Sulphuric acid (98%)5.6kg Sodium Hydroxide5-6 kg Steam11 tons Electricity2900 Kwh

Mercury cellDiaphragm cell

Process description A combination of the diaphragm and mercury cell processes is described here. Brine solution flows through pipelines to a storage reservoir and then through a brine treatment system. Caustic soda, soda ash, and /or barium carbonate removes calcium, magnesium and iron salts which would clog up diaphragms. This purified saturated brine (25-28% NaCl) is heated and electrolysed in a diaphragm cell. The cell, operating at 45-45% decomposition efficiency, discharges a 10-12% solution of caustic soda with about an equal concentration of NaCl. Multiple effect evaporation concentrates the cell liquor to 50% NaOH solution. The precipitated salt is separated, centrifuged, washed, and then slurried with treated brine. Salt separator overflow is 50% caustic soda product containing 2% NaCl and % NaClO on dry basis.

Major engineering problems Choice of cell design Corrosion This commercial caustic grade can be evaporated to produce saturated 73% NaOH liquor or fused to flake, granular or stick caustic. Purified grade can be produced by a combination treatment of CaCO 3 to remove colloidal Fe and liquid NH 3 counter current extraction to take out chlorine and chlorate impurities.

Consumption of Caustic Soda