The double absorption process is the most commonly used process in new plants. Within a given overall process concept, many variations in detailed design are possible.
Atmospheric air is dried with 95 – 96 wt.-% sulfuric acid and used for the combustion process. The SO2 gas is cooled in a waste-heat boiler and converted into SO3, in either a 4-layer or 5-layer converter. Between the first and second bed, the hot gas is cooled in a steam superheater.
After the second layer, the gas is cooled in a second superheater or economizer and then admitted to layer three. After the third layer, the converted gas is cooled in a gas/gas heat exchanger and an economizer en route to the intermediate absorber. Subsequent to the absorption of SO3, the residual SO2 gas is preheated again to conversion striking temperature before entering the fourth layer.
A major advantage of the double absorption process is the ability to feed gases with higher SO2concentration than would be possible with the single catalysis process by reaching low SO2-emissions. By the sulfuric acid production, based on sulfur combustion a considerable amount – up to 1.4 t/mt sulfuric acid – of HP-steam can be produced.
Outotec has build or designed single absorption plants for:
- Capacity of more than 8,000 mtpd
- Feed-gas concentration up to 20 vol.-% SO2
- Conversion efficiency of 99,9 %
For further information, please contact
acid(at)outotec.com