In addition to SO2, coal combustion will also produce a small amount of SO3. SO3 concentration in flue gas is 10-40ppm. As the flue gas contains water (4% - 12%), SO3 generated immediately forms sulfuric acid mist. When the temperature is low, the sulfuric acid mist condenses into sulfuric acid, adheres to the inner wall of desulfurization and denitration equipment, or dissolves in washing solution. This is the main reason for the serious corrosion of wet absorber and related equipment. The treatment method is to use corrosion-resistant materials to make the absorption tower, such as stainless steel, epoxy glass fiber reinforced plastic, rigid polyvinyl chloride, ceramics, etc. Regardless of the desulfurization process, its environmental benefits are significant, but the economic benefits are uncertain.
Many desulfurization methods can obtain high desulfurization efficiency, but the uneven desulfurization capacity is not the only standard to judge the advantages and disadvantages of desulfurization methods. In addition to the desulfurization capacity, it also depends on the general technical and economic conditions of the method.
Generally speaking, the following aspects should be considered: first, the desulfurization capacity needs to meet the requirements of environmental protection; Select advanced technology and reliable operation technology; Select technologies with low investment and low operation cost; Consider waste treatment and secondary pollution: absorbent needs a stable source, high quality and low price, which is a very important factor.
Relatively speaking, China's limestone resources are relatively rich, high purity and widely distributed, but the supply of high-purity gypsum is very difficult. The treatment of by-products requires a site and a shopping mall as inducement; The sulfur content of the coal used also has an impact on the desulfurization process. The important factor for selection is to select the appropriate desulfurization method according to the sulfur content of coal.