Study On The Removal Of Sulfide And Cyanide In The Calcium Carbide Slag Slurry

Using calcium carbide slag as wet flue gas desulfurization (FGD) absorbent is an effective resource-oriented utilizaition method for calcium carbide slag. However, the reductive toxic components, such as sulphide and cyanide, would inhibit the oxidation of calcium sulfite and hamper the utilization of calcium carbide slag. In this dissertation, three processes for the removal of sulfide and cyanide in calcium carbide slag slurry were studied. The operating parameters of each process were investigated and the suitable process was suggested according to their economic evaluation and feasibility assessment. Furthermore, the feasibility assessment of removal process was verified by experimental-scale studiesFirstly, three processes, such as catalytic air oxidation process, H2O2 oxidation process and chlorinated lime oxidation process, were studied in this dissertation for the removal of sulfide and cyanide in calcium carbide slag slurry. Additionally, the influences of oxidant addition amount, catalyst addition amount, pH value and reaction temperature in these processes were also studied. Then the optimal operating parameters of these processes were determined. For the purpose of application in power-plant flue gas desulfurization process, the economics and feasibility evalution of these processes were performed. The results showed that chlorinated lime oxidation process was the suitable process for the removal of sulfide cyanide in calcium carbide slag slurry.Secondly, the removal of cyanide in the calcium carbide slag slurry by chlorinated lime oxidation process was studied in this dissertation. Furthermore, the influences of oxidant addition amount, pH value and reaction temperature on the removal efficiency were observed. It was found that the removal efficiency of cyanide could reach 95% when the mass ratio of chlorine and cyanide wasgreater than 2.73. The pH value and reaction temperature had little influence on the removal efficiency.Finally, experimental-scale studies on wet FGD process using calcium carbide slag as absorbents coupling with chlorinate lime oxidation pretreatment process were carried out. The results showed that the desulfurization efficiency could reach 90%. With the suitable addition amount of chlorinated lime, the sulfide and cyanide in the calcium carbide slag could remove efficiently before the desulfurization process.