Methods Of SO₂Removing From Simulated Smelting Gas With （NH₄）₂S And Sulfur Recycling

Flue gas desulfurization technology(FGD)was widely studied and used in the world. Wet desulphurization was widely studied and used, because of wet desulphurization reaction quickly, high efficiency, high utilization rate of desulfurizer; Wet FGD disadvantage is easy to produce secondary pollution, easy plug fouling, corrosion of equipment, higher operating costs. To overcome the shortcomings, wet desulfurization research boom continues unabated in the world.Sodium sulfide absorption purification typical smelting flue gas SO2gas is the main contents of this paper. Starting from the research of sodium sulfide methods, ultimately determine the use of (NH4)2S solution to absorb SO2gas through a series of experiments analysis. The effects of pH, ammonium sulfide solution concentration, gas flow rate, temperature conditions on the absorption process was investigated in experiment. The trace phosphorus sulfur analyzer is used to detect the changes of concentrations of SO2and H2S in the exhaust. Iodometric method is used to analyze the situation of different ion concentration in solution with pH change.The results show that the method of ammonium sulfide absorption purification of SO2with good effects and the exhaust can meet the national emission standards.When the pH is greater than7will produce large amounts of hydrogen sulfide gas in the absorption process.Therefore,the pH value of the solution needs to be controlled at7or less. The results show that under the condition that pH=3～7, flow velocity of300mL·min-1, normal temperature,(NH4)2S solution concentration of0.2-1.2mol·L-1, the absorption efficiency of SO2reached more than99.8%and did not produce H2S. After the completion of the reaction,(NH4)2S2O3and NH4HSO3are two main remaining in the solution, and the molar ratio steady at around1:2.There are two choices with ammonium sulfide method absorbing liquid processing. Firstly, recovery of sulfur and ammonium sulfate product through the REDOX reaction, the product have certain economic value and can be directly for sale.However, the high energy consumption and the high requirements of large equipment led to the economic benefits of the product only can offset part of the investment. Secondly, ammonium sulfate fertilizer containing a small amount of ammonium thiosulfate can be obtain through a series of chemical treatments.The way can bring considerable economic benefits for industrial use in virtue of low equipment requirement,low energy consumption and simple process. Sulfur and ammonium sulfate which were generated during reaction were characterized by X-ray diffraction (XRD) and X-ray Fluorescence (XRF). The results show that the purity of sulfur is99.14%and the percentage of nitrogen in ammonium sulfate is23.6%; Scheme2nitrogen content in ammonium sulfate product was25.3783%and there is a small amount of (NH4)2S2O3, after half a quantitative analysis of the two mass fraction were96%and3.87%respectively.Comparison of sodium sulfide method and ammonium sulfide method:(1) Both have good purification effect of SO2in the absorption stage and the same absorption principle.(2) The main difference of between sodium sulphide method and ammonium sulfide method are that the post-processing of absorption solution and end product. Compared to sodium sulfide, ammonium sulfide removal of SO2and recycling of ammonium sulfate are easier handling and use, low energy consumption, low equipment requirements, the process is simple, no pollution.etc.