| China is the world’s first coal producing country, and coal consumption is the first in the world. In the case of the emission of SO2 and Hg in coal combustion flue gas is increasingly grim situation, this paper use wheat straw pulping black liquor to remove SO2 and Hg in flue gas, combined with the existing WFGD method. Study on the simultaneous desulfurization and mercury removal performance of wheat straw pulping black liquor. Discussing the interaction between the desulfurization efficiency and the mercury removal efficiency. Analysis of the mechanism of desulfurization and mercury removal of the main components of black liquor. Study on the stability of mercury removal from black liquor, in other words, that is the re-release of Hg in black liquor. Analysis of the mechanism of desulfurization and mercury removal of the main components of black liquor further. The following conclusions are obtained from the experimental study:（1） Alkaline substance in black liquor such as Na OH, Na2CO3, Na2 S can effectively absorb the SO2 in coal fired flue gas. The hydrolysis of OH- can react with the Hg2+ reaction in coal fired flue gas to generate Hg（OH）2, and then it was decomposed into Hg O precipitation, and Na2 S can react with Hg2+ to generate stable Hg S precipitation, so this kind of material can effectively remove the Hg2+ in coal fired flue gas. Solution and Hg2+ reaction to generate a high stability of the sediment, and the material is not easy to break down and to be decomposed, so the mercury removal efficiency of this kind of material is almost not affected by the efficiency of desulfurization, and the stability of mercury removal is high.（2） Another substance in the black liquor, such as NaBr and NaCl, whose solution is neutral, the removal of SO2 from coal combustion flue gas by this kind of material depends on the dissolution of SO2 in solution.Br- and Cl- in solution can react with Hg SO3 and generate complexBr Hg SO3- and Cl Hg SO3-, and the rate at which the substance is reduced to Hg0 is much lower than the rate at which Hg SO3 is reduced. With the increase of the concentration of the solution,Br- and Cl- can continue to react with the solution, to generate a higher stability ofBr2 Hg SO32- and Cl2 Hg SO32- respectively, and such substances are not to be restored. Therefore, NaBr and NaCl can effectively in inhibit the reduction of Hg2+ and effectively remove the Hg2+. The stability of mercury removal ability of solution is normal, and the stability of the solution is proportional to the concentration of the solution, that is to say, the higher the concentration of the solution, the higher mercury removal stability of the solution.（3） There is also a substance, such as Na2SO4, whose solution is neutral, the removal of SO2 in flue gas also depends on the dissolution of SO2 in solution. Na SO4 can react with Hg2+ in flue gas to form Hg SO4 precipitation which is not soluble in water and slightly soluble in acid. Therefore, Na2SO4 has a certain effect on the removal of Hg2+ from flue gas. But because Hg SO4 is slightly soluble in acid, when the solution absorbs a certain amount of SO2, the solution is weakly acidic, so there is a small amount of Hg SO4 dissolved, forming Hg2+, and it can be reduced by SO32- in solution. Therefore, the desulfurization efficiency of Na2SO4 has a slight inhibitory effect on mercury removal efficiency, and the stability of mercury removal is generally. |
