Abstract:

In order to realize zero discharge of desulfurization wastewater, evaporation and crystallization technology of desulfurization wastewater with high temperature flue gas has gradually developed. The decomposition of crystalline salts in desulfurization wastewater evaporation process is probably the key problem that may influence the further application of evaporation technology. This paper briefly introduced the characteristics of desulphurization wastewater in thermal power plants and the stability of salt during evaporation and crystallization. The thermal decomposition mechanism of hydrated magnesium chloride was introduced emphatically. The comprehensive analysis shows that magnesium chloride and ammoniate will be decomposed to produce hydrogen chloride gas and ammonia respectively, which will increase the content of chlorine ion in the desulphurization wastewater and ammonia concentration at chimney outlet. Finally, the quality reduction of fly ash in the evaporation process with by-pass high-temperature flue gas was also discussed.

Key words: desulfurization wastewater, zero discharge, evaporation and crystallization with high temperature flue gas, chloride decomposition, evaporation concentration with low temperature flue gas