Studying On Desalination And Reusing Technology Of Desulfurization Wasyte Solution

Wet oxidation technology in flue gas desulfurization section has these advantages:the desulphurization rate is high; H2S in the gas could be converted into the elemental sulfur at ambient temperatures and pressures and the desulfurization waste solution could be recycled. However, lots of oxidation by-products, such as sulfate, thiocyanate and thiosulfate are riched in the desulfurization waste solution, which would cause the desulfurized efficiency decreasing rapidly. The salt concentration in the desulfurization waste solution will far exceed the emissions standards, which becomes a big problem for factory production and environmental protection. Therefore, to explore a new desulphurization waste liquid treatment method with economic and effective is important for environment protection.NaHCO3-Na2CO3 buffer solution can be used as an absorbing solution for treating the flue gas. How to reduce the concentration of the sulfur compounds in the absorption solution is the main purpose in this paper. Three technical schemes were proposed like electrochemical oxidation method, photochemical method and chemical precipitation and the results are as follows:Firstly, the sodium thiosulfate in the desulfurization waste solution can be oxidized into sulfate in anode surface by using electrochemical oxidation method. A three electrodes system with a titanium ruthenium as the working electrode, a saturated calomel electrode as the reference electrode and a titanium platinum as the counter electrode was adopted in this technology. The removal rate of sodium thiosulfate could reach 21% for 1 hour electrochemical oxidation, with cell voltage of 0.9 V.Secondly, the concentration of sodium thiocyanate could be reduced by 52.5% with photochemical method by using TiO2 as catalyst. However, the concentration of thiocyanate would increase when placed in the darkness. The reason maybe that the photochemical reaction product [(SCN)2] is unstable and reaction mechanism needed to be studied. Thirdly, the sodium thiocyanate in the waste solution can be turned into copper thiocyanate when adding moderate copper sulfate. For example, when adding less than 0.5 times stoichiometric ratio of the copper sulfate, the concentration of sodium thiocyanate in the transferred solution could be reduced by 35.5%. In the transferred solution, sodium thiocyanate and copper ion could not be detected and sodium sulfate was saturation which could be crystallized under low temperture. After filtration, the solution can be reused for the next cycle by adding certain amount of sodium carbonate.