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 SO2 removal 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.
A novel method to prepare soil nutrient amendment by calcining a mixture of white mud and potassium feldspar and its environmental assessment were investigated.Under the optimal conditions of a blending mass ratio of 70-30 for white mud to potassium feldspar,a calcination temperature of 1 000℃,a calcination time of 1.5 h and spherulitic diameter of 2.0 cm,the calcined product,as a soil nutrient amendment,could be prepared with the following nutrient composition(mass fraction):K2O 4.16%,CaO 23.43%,MgO 5.04%,SiO2 22.92%,SO4 2-3.71%,and Cl -3.87%in 0.1 mol/L citric acid solution.The concentrations of heavy metals in the calcined product and the emission concentrations of harmful gases from a mixture of white mud and potassium feldspar during calcination process could qualify the National Standards without causing secondary environmental pollution.
