I, Brief 
China is a coal-consuming country with large coal consumption. After combustion, coal is produced with a large amount of SO₂ and SO₃. If it is not treated, it will cause great pollution to the environment. The flue gas generated after combustion of the coal-fired boiler is subjected to desulfurization treatment. 
Ⅱ, the current commonly used desulfurization process 
1, sodium alkali double alkali desulfurization technology 
2, limestone / lime - gypsum desulfurization technology 
III, sodium alkali double alkali desulfurization technology 
1, system composition 
sodium alkali double alkali desulfurization by absorption liquid preparation system , absorption tower, absorption liquid circulation system, absorption liquid regeneration system, electrical control and online monitoring system. 
2. The process 
flue gas enters the absorption tower through the booster fan, contacts the absorption liquid fed from the circulation pump, and is removed from the SO₂. The flue gas after being washed is defoamed by the demister in the tower and then enters the outer row of the soot. The absorption liquid from the absorption tower is returned to the circulation tank for recycling. When the pH value of the absorption liquid in the circulation tank is lowered to the set value, the drain pump is automatically started, and the absorption liquid that needs to be regenerated is pumped into the regeneration tank for regeneration (regeneration using lime slurry), and then enters the sedimentation tank for sedimentation, sedimentation tank The supernatant liquid is returned to the circulation tank, and the sediment of the sedimentation tank (calcium sulfate and calcium sulfite) enters the dehydration device, and the (wet) solid matter formed by the dehydration device, that is, the desulfurization slag, is periodically discharged; the water desorbed from the dehydration device returns to the sediment. 
During the operation, fresh absorption liquid should be added to the circulation tank regularly to supplement the amount of nano-alkali contained in the absorption liquid. 

4. Main features of the sodium-alkali double-alkali method 
l Mature technology, reliable operation and low investment. 
l The sodium absorption rate is high, the liquid-gas ratio is low, and the desulfurization efficiency is up to 95%.
l The nanobass in the absorption solution can be reused after base substitution, and the running cost is low. 
l The flue gas of the absorption tower is relatively humid and corrosive. The equipment, pipes and soot of the absorption tower and later are required to be treated with anti-corrosion treatment. 
V. Limestone/lime--Gypsum desulfurization technology1 
, system composition 
limestone/lime--Gypsum desulfurization system by absorption slurry preparation system, flue gas absorption and oxidation system, desulfurization by-product treatment system, desulfurization by-product treatment system, desulfurization wastewater treatment System, electrical control and online monitoring systems. 
2. Process Flow 
Flue gas enters the absorption tower through the booster fan (the bottom of the absorption tower is the slurry tank), contacts the slurry fed from the circulation pump and is removed from the SO2. The fresh slurry is continuously added to the slurry tank at the bottom of the absorption tower, the Ca SO3 is forcibly oxidized to Ca SO4, and the slurry is sent to the slurry cyclone through a circulation pump to separate the water in the slurry and sent to the wastewater treatment system; The underflow of the cyclone enters the dewatering unit. The water dewatered by the dehydration device is filtered and then returned to the absorption tower for reuse. 
Five, limestone / lime - gypsum desulfurization main features 
l mature technology, reliable operation, industrial applications. 
l Desulfurizer is cheap, rich in resources, and the desulfurization efficiency can reach 95%. 
l Desulfurization by-products are available. 
l There is wastewater generated during the desulfurization process, and the wastewater must be treated before being discharged. 
l The flue gas of the absorption tower is relatively humid, the flue gas is corrosive, and the equipment, pipelines, and soot after the absorption tower and the period need to be treated with anti-corrosion treatment.