Leaching characteristics of alkaline coal combustion by-products: A case study from a coal-fired power plant, Hebei Province, China

摘要

In recent years, coal combustion by-products have attracted much attention because of their large production volume, adverse environmental effects of potentially toxic elements, and as potential sources of critical metals. In order to better evaluate the leaching characteristics of alkaline coal combustion by-products, the Leaching Environment Assessment Framework (LEAF) proposed by the United States Environmental Protection Agency was adopted in this study. Depending upon the properties of the samples, the test methods used in this paper mainly included Methods 1313, 1314, and 1316. The liquid-solid partitioning curves of samples were drawn according to the results of chemical analysis. Samples were collected from the coal-fired Sunzhuang Power Plant, Hebei Province, China. The leaching characteristics of coal combustion by-products are discussed from three aspects: pH values, liquid-solid ratios, and accumulated liquid-solid ratios. According to the trend of the liquid-solid partitioning curves, the modes of occurrence and causes of mobility of trace elements in the coal combustion by-products are discussed. To assess the potential environmental risk of hazardous elements leached from coal combustion by-products, the maximum leaching values of hazardous elements were compared to the upper limit value of the Type III Chinese groundwater quality standard, suggesting that in the eluates of Method 1313, arsenic, selenium, beryllium, thallium, nickel, and lead contents in the eluates of fly ash and bottom ash exceed the recommended upper limit. However, in the eluates of Methods 1314 and 1316, selenium, molybdenum, barium, and nickel exceed the recommended upper limit.