Process Description of Limestone based Wet Flue Gas Desulphurization System
The incoming flue gas from boiler after ESP / Bag Filter is brought into contact with aqueous slurry of limestone in a scrubber tower.
Sulphur dioxide in the gas reacts with the slurry to form calcium sulphite which is oxidized in oxidation tank to produce Gypsum.
Gypsum is continuously removed from the oxidation tank in the form of slurry.
This slurry is passed through hydro cyclones followed by a filtration plant to separate gypsum flakes (10 -15 % moisture) and filtrate is recycled back to the process.
Features
Low Cost Limestone is used as sorbent
Commercial grade Gypsum is obtained as by-product
Most proven technology worldwide
Reasonable Operating cost
By-product (gypsum) is sellable
No disposal cost
High SO2 removal efficiency
Negligible liquid effluent discharge from the plant.
No solid waste is generated
Applications
Coal fired power plants
Large process boilers
Carbon black plants
Process Description of Sodium based Wet Flue Gas Desulphurization System
Flue gas rich in SO2 is brought in contact with an aqueous solution of NaOH / Na2CO3 in a towe
Sulphur dioxide reacts with of NaOH / Na2CO3 form Sodium Sulfite which is continuously removed from the bottom tank
Combined particulate and SO2 control is also possible
Features
Fully Automatic plant
High Removal efficiencies and tolerant of wide fluctuations in inlet SO2
Clear solution scrubbing minimizes scaling and plugging problems
The by-product can generate substantial revenue
Applications
Medium size power plants and process boilers
Process Description of Ammonia based Wet Flue Gas Desulphurization System
Working principle of the ammonia flue gas desulphurization process is similar to the limestone process except that aqueous ammonia is used as the scrubbing agent
SO2 is removed from the flue gas by reaction with ammonia, and the product is ammonium sulphate.
Features
Ammonia is used as sorbent and Ammonium sulfate is obtained as by-product
The high value of by-product Ammonium Sulphate gives attractive pay-back.
No effluent discharge plant is required.
Produces semi dry ammonium sulfate which is a fertilizer
High SO2 removal capabilities
Applications
Medium size power plants and process boilers
Process Description of Seawater based Wet Flue Gas Desulphurization System
Two basic seawater FGD process concepts:
Most commonly used process using the natural alkalinity of the sea water to neutralize absorbed SO2
Addition of lime to seawater to neutralize absorbed SO2.
Features
Sea water is used as sorbent
No effluent discharge plant is required.
Applications
Plants in vicinity of sea with easily available sea water
