Low Concentrations Of Sulfur Dioxide Flue Gas Treatment And Study Of A New Method For Elemental Sulfur Recovery,

Low-concentration SO2 flue gas is usually treated by Limestone-Gypsum desulfurization technology. However, this method has some disadvantages, such as requiring large investment, suffering serious encrustation, recontamination of wastes from the desulfurization process. The new method of removing low-concentration sulfur dioxide from flue gas and recovering element sulfur by auto-redox process was proposed in our research team. Through developing technique for quickly and dynamically preparing low-concentration gas and establishing bubbling absorber for flue gas desulphurization (FDG), the low-concentration SO2 flue gas absorption process, auto-redox element sulfur production process and absorbent regeneration process were investigated. And the mechanism in the process was analyzed; process parameters were determined. The following results were gained:(1)The newly developed patented technique for quickly and dynamically preparing low-concentration gas was able to prepare low-concentration gas directly by highly purified raw gas. The minimum concentration of prepared gas reached blow 0.01%. The patented technique was suitable for low-concentration gas long-time supplying.(2)0.01%-3% low concentration SO2 can be disposed and converted to element sulfur by the designed FDG process.(3)The Na2S solution absorbing process exhibited a three-stage pattern. In a two-stage bubbling system, when SO2 concentration of the flue gas was 0.01%-3%,the SO2 absorption ratio was above 97.36%. The SO2 absorption ratio was affected most by the temperature of absorption solution. The higher the temperature, the lower the absorption ratio was.(4)The condition for obtaining the maximum sulfur conversion was: 0.25-0.7L/min of flue gas velocity,200℃of reaction temperature. The concentrations of SO2 and absorbent had no obvious influence on sulfur conversion. The formation of sulfur was promoted by the secondary reaction.(5)The process of using carbon as reductive agent to reduce Na2SO4 and regenerate Na2S was proved to be feasible based on thermodynamic analysis. The optimum condition of which was:950℃of calcination temperature,4:1 of Na2SO4:C,9 min of constant temperature time. Under this condition, the conversion of Na2SO4 reached 99.0%. NH4C1 could act as catalyst in the calcinations process, which reduced the required calcinations temperature from 950℃to 800℃and retained 99.0% of Na2SO4 conversion.