Gypsum wet desulfurization process

Limestone-gypsum wet desulfurization process

System process diagram

working principle
This process uses limestone as desulfurization absorbent, which is crushed and ground into powder and mixed with water to make absorption slurry (when lime is used as absorbent, lime powder is digested and treated with water and stirred to make absorption slurry). In the absorption tower, the SO2 in the flue gas reacts with the CaCO3 (calcium carbonate) in the slurry and the blown oxidizing air to form dihydrate gypsum, and the sulfur dioxide is removed. The gypsum slurry discharged from the absorption tower is dehydrated by the dehydration device and recovered. The flue gas after desulfurization is dewatered by the mist eliminator, heated by the heat exchanger, and then enters the chimney and is discharged to the atmosphere.
The flue gas enters from the lower side of the absorption tower and is in countercurrent contact with the absorption slurry. In the tower, CaCO3 reacts with SO2 and H2O to generate CaSO3 1/2H2O and CO2↑; for the CaSO3 1/2H2O and O2 and H2O undergo oxidation reaction to obtain dihydrate gypsum, a by-product of desulfurization.
Chemical reaction equation:
2CaCO3+H2O+2SO2 → 2CaSO3 1/2H2O+2CO2
2CaSO3·1/2H2O+O2+3H2O → 2CaSO4·2H2O
The limestone (lime)-gypsum wet desulfurization process system mainly includes: flue gas system, absorption oxidation system, slurry preparation system, gypsum dehydration system, and discharge system.
The process is pure dry desulfurization technology, the temperature drop of the whole system is less than 10℃, the exhaust gas temperature after desulfurization is greater than 130℃, and the exhaust flue gas has no white smoke. And the system does not consume water and produce no waste water.
Technical Features
a. The lime (limestone)-gypsum desulfurization process is a wet desulfurization process. The process flow is simple, the technology is advanced and reliable, and it is a desulfurization process widely used in flue gas desulfurization at home and abroad.
b. This process has a wide range of flue gas treatment, and can effectively treat flue gas from 200MW to 600MW units.
c. The absorption oxidation tank is separated from the bottom tank.
d. The lower part of the absorption tower is equipped with an angle steel sieve plate device, which makes the flue gas entering the absorption tower evenly distributed, strengthens the turbulent flow between the flue gas and the washing liquid, and improves the desulfurization efficiency.
e. According to the flue gas flow, the spray device can be designed as atomization spray or liquid column spray. The atomizing spray nozzles, liquid column nozzles and water curtain nozzles arranged in the absorption tower of this process flow are all structures that are not easy to block.
f. Desulfurization liquid preparation The acidifying agent (oxalic acid or formic acid) is added to the stirring tank, which strengthens the solubility of lime (limestone) in the aqueous solution and improves the utilization rate of the desulfurizing agent.
g. Economic and technical indicators of this process. When limestone is used as desulfurizer, the liquid-gas ratio is 10-12L/m³, and when lime is used as desulfurizer, the liquid-gas ratio is 1-1.5L/m³. The desulfurization system has low energy consumption.
h. The desulfurization liquid dosing device in the tower bottom tank is evenly distributed with suspension nozzles at multiple points, and the large diameter absorption tower bottom tank will not produce precipitation.