Paper_Collaborative utilization of fly ash and desulfurization wastewater

In order to reduce sulfur dioxide emission in flue gas to meet the national requirement less than 35 mg/m3, the wet desulfurization process is typically used in the coal-fired power plant, resulting in generation of flue-gas desulfurization gypsum and desulfurization wastewater. The wastewater can be re-used or discharged only after water-treatment to meet the relevant industry standard requirements of water quality. This treatment process increases the operation cost. Fly ash is also produced from the coal-fired power plant, mainly used in building materials as a supplementary cementitious material to cement. The objective of this study is to develop fly ash-based products by collaborative utilization of fly ash and desulfurization wastewater with the minimum amount of cement. Fly ash and desulfurization wastewater from a coal-fired power plant located in Ningxia, China, and ordinary Portland cement from the same area were used in this study. Fly ash-based samples were made by different fly ash to cement ratios at a given water to solid ratio to meet the lowest mechanical strength requirements of some industry standards using the minimum amount of cement. As expected, the results indicate that both mechanical strength and water-soluble salt content of the samples decrease with decreasing cement content. The use of the cement content as low as 9% and 12% can meet Class 10 of JC 238 and MU 10 of JC 239 , respectively. Three different desulfurization wastewater types including raw water, effluent water and high-salinity water versus de-ionized water on mechanical strength and water-soluble slat content were also compared. The results show that samples with raw desulfurization wastewater have the highest mechanical strength but those with effluent desulfurization wastewater have the lowest high-soluble salt content. As expected, samples using high-salinity water has lowest mechanical strengths but highest water-soluble salt contents.