Polymer environmental protection desulfurization agent desulfurization mechanism(2)

1 Sources of SO2 emissions from cement enterprises

SO2 emissions from cement enterprises are mainly sulfur brought in from raw materials, sulfur in raw materials in the form of organic sulfur, sulfide and sulfate, of which sulfide is mainly pyrite and albite (both FeS2), sulfate mainly includes gypsum (CaSO4-2H2O) and hard gypsum (CaSO4). Sulfur in the form of sulfide and organic sulfur will be oxidized to SO2 at 300~600 ℃, which mainly occurs in the second cyclone of the five-stage preheater or the third cyclone of the six-stage preheater; sulfur in the form of sulfate will be decomposed in the decomposition furnace and rotary kiln, and most of the generated SO2 will be absorbed by the calcium oxide in the decomposition furnace. 

Therefore, the emission level of SO2 in cement production depends mainly on the content of sulfide and organic sulfur in raw materials, and is largely independent of the content of sulfate. In the preheater of cement precalciner system, the absorption efficiency of CaO for SO2 is much higher than that of CaCO3 at temperatures below 600 ℃. 

In the first and second stage preheaters, the decomposition rate of CaCO3 is lower, and the flue gas contains less CaO, and the absorption efficiency of SO2 is very low, which leads to higher SO2 emission concentration. So how to make SO2 oxidized to SO3 in the preheater, and at the same time promote the raw material in the preheater to absorb SO3, and finally reduce the enrichment of SO2 in the first and second preheaters is the key of desulfurizer technology.

2 Status of desulfurization technology

The first choice for reducing SO2 emissions in cement enterprises is to minimize SO2 production in the production process, such as the use of low sulfur raw materials and coal, low sulfur raw materials and coal bring less sulfur into the production line system, which can reduce the production of SO2 at source. 

Secondly, the kiln and mill run as one, the cement production process, raw material mill and kiln run at the same time, the exhaust gas generated in the firing system into the raw material mill system, raw material (limestone) in the grinding process has been produced fresh surface, while raw material and exhaust gas in the mill has a certain residence time, and the exhaust gas on the raw material and a certain amount of heating, so that the vast majority of SO2 in the exhaust gas is adsorbed on the surface of the raw material. 

Further is the bag dust collector dust desulfurization, bag dust collector in the gas and material contact more closely, high relative humidity, can better adsorption of SO2. cement kiln system originally has a complete desulfurization system, only when the raw material and coal in the sulfur content is too high or raw mill stop grinding, only need to use additional desulfurization measures. The main desulfurization methods currently used are wet, semi-dry, dry and ammonia desulfurization, etc.