Sulphuric Acid Production by Dcda Process

4519 Words Mar 7th, 2012 19 Pages
INTRODUCTION

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,
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These traditional contact plants can be further subdivided into the double absorption process, which is the type of process now most commonly used in new plants with intermediate absorption and the older, without intermediate absorption also referred to as the single absorption or single contact process.

Double Conversion Double Absorption (DCDA) Process
The main steps involved in DCDA process are as below: 1. Melting solid Sulphur with steam coils, followed by filtration or settling of impurities to obtain clean sulphur containing less than 10 mg/l of ash. 2. Burning the molten Sulphur with air to produce gas-containing SO2. 3. Cooling the hot gas in Waste Heat Boiler System to produce 4. superheated or saturated steam at conditions fixed, as per requirements. 5. Catalytic oxidation of SO2 to SO3 in three consecutive passes of converter containing V2O5 catalyst with intercooling of gas in between. 6. Absorption of SO3 (formed in IVth pass) in the final absorption tower.

The exothermic heat of reaction is utilized to produce steam in Waste Heat Boiler system and to reheat the gases going to IVth pass from the intermediate absorber.
The sulphur-burning DCDA process is considered to be the standard sulphuric acid production process based on approximately 10-12% SO2 in sulphur furnace. All reactions in the production of sulphuric acid from elemental sulphur are exothermic. The liberated
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