Study on SO4 2- Removal with Ettringite Precipitation Approach in Wet Desulfurization of Firing-Power Plant

The deacidification treatment of desulphurization wastewater is one of the difficulties in clean discharge of power plants. Ettringite precipitation is a new method of acid removal in recent years, but its efficiency is affected by many factors, and the mechanism is still unclear. In this paper, we studied the effects of the molar ratio of calcium to sulfur ([Ca] / [S]), the molar ratio of aluminum to sulfur ([Al] / [S]) and pH on the deacidification of ettringite precipitation approach, and found the optimum conditions were as follows: pH=12, [Al] / [S] = 0.67, [Ca] / [S] = 2. Based on the optimal level, the effects of high contents of Mg2+, Cl−, Na+ and NO3+ in desulfurization wastewater on the removal of SO4 2− by ettringite precipitation were studied. It was found that Mg2+ could inhibit the formation of ettringite precipitation.