A case analysis and treatment measures of high moisture content in wet desulphurization gypsum

Abstract

China’s thermal power plant wet FGD (flue gas desulphurization) produces more than 80 million tons of gypsum each year. The factors affecting the quality of wet desulphurization gypsum are limestone quality, flue gas dust, gypsum slurry pH, slurry quality, gypsum water content, desulphurization system design features, and operating conditions, etc. There are many reasons for high gypsum moisture content, and the analysis and solution are particularly complex. Through a case analysis of a power plant with high moisture content of desulphurization gypsum, the main reasons are that the unit has been operating under low load conditions for a long time with low sulphur coal, limestone supply slurry is high, slurry pH is high, and the volume of gypsum crystals generated is small, resulting in gypsum dehydration difficulty and high moisture content. The measures were to add the crystal seeds into the slurry and to lower the operation pH. The slurry quality is improved, and the gypsum dehydration returns to normal. The design margin of the desulphurization system is large, even in a long-term low sulphur and low load operation. There are no similar cases, and this situation generally does not attract attention. It is worth further analysis and reference.