Sulphuric Acid is an important chemical, which has large-scale industrial uses. Its major user is the phosphate fertilizer industry. Other important applications are in petroleum refining, steel pickling, rayon & staple fiber,alum, explosives, detergents, plastics and fibers etc. Sulphuric Acid Industry is very old and has been continuously adopting the technological developments. It started with Lead Chamber process followed by contact rocess with Single Conversion Single Absorption (SCSA) and now Double onversion Double Absorption Process (DCDA) process.
In India, there are about 140 Sulphuric Acid Plants (130 Sulphur based & 10 Smelter Gas based) with Annual Installed Capacity of about 12 Million MT.As in some places, there are more than one stream/unit with some common facilities these plants are situated in 131 locations. It may be observed that about 25% of the installed capacity is located in Paradeep (Orissa) only consisting of 2 plants (4 streams/units). The current annual production of Sulphuric Acid is about 5.5 Million MT,against the installed capacity of 12 Million MT/Annum from Sulphur based as well as Smelter Gas based plants. Some of the plants have been closed down due to various reasons. It is learnt that many captive plants have been closed down due to non-viability of the main plant, viz. Single Super Phosphate etc., while merchant plants have closed down due to poor demand. The demand of Sulphuric Acid is fully met by the current production, as the installed capacity is more than double the demand.
The contact process for the production of Sulphuric Acid is based on the catalytic oxidation of SO2 to SO3. Since the oxidation reaction of SO2 to SO3 is exothermic, the temperature of the gases after catalytic conversion rises. As the forward reaction progresses, the state of equilibrium is approached and the forward reaction comes to halt. In DCDA Plant, SO3 is removed from the gas stream after 2nd and 3rd bed, which shifts the