Flue gas desulphurization using sodium sulfide on pilot scale

A novel technique of flue gas desulphurization(FGD)using industrial sodium sulfide as absorbent is described to remove SO2 in flue gas.The FGD byproduct in this novel technique is sodium thiosulfate(Na2S2O3·5H2O,Hypo) which can be used as chemical raw material. Optimal operating parameters about this technique have been determined. In order to enhance productive efficiency of sodium thiosulfate, EDTA disodium additive is added into absorption solution to prevent oxidation of sodium thiosulfate. Its optimal concentration is 0.02 wt. %. The pH value of absorption solution is set in the range of 5-6.5. Experimental results show that SO2removal efficiency averagely reach 98.72 %.The highest productive efficiency of sodium thiosulfate reaches 83.24 %. The sodium thiosulfate formed during FGD can be separated from saturated absorbent by filtration, concentration and crystallization. The filtrate after separating sodium thiosulfate will be reused as SO2 absorbent by replenishing some fresh sodium sulfide.