With the rapid development and wide application of municipal solid waste incineration (MSWI) technology, recycling of MSWI fly ash becomes more and more important. However, the high content of chlorine in fly ash significantly inhibits its recycling as construction materials. Wet-washing has been adopted to remove the chloride salts from MSWI fly ash, but the removal efficiency is highly influenced by the intrinsic property of the ash samples. This research collected two ash samples from Chongqing and Tianjin incineration plants and analyzed their physic-chemical characteristics by performing particle size distribution, chemical and mineralogical composition, and leaching toxicity analysis. Based on this analysis, the ash samples were further treated by wet-washing and wet-carbonated-washing. The results revealed that the chlorine in Chongqing fly ash exists as both soluble (e.g. NaCl and KCl) and hardly soluble salts (including CaClOH, Friedel's salts and Ca6(CO3)2(OH)7Cl). Wet-washing of the Chongqing fly ash gives a Cl removal ratio of only 88% due to existence of some hardly soluble salts. Wet-carbonated-washing of the Chongqing fly ash significantly improved the Cl removal ratio, reaching a maximum value of 94%. It is assumed that injection of CO2 in the washing process decreased the solution pH, which consequently promoted the decomposition and solubilization of these hardly soluble chlorine-containing salts. Different from the Chongqing fly ash, a high Cl removal ratio (96%) was obtained for the Tianjin fly ash when treated by the wet-washing method. This may be ascribed to the relatively lower content of the hardly soluble chlorine-containing salts in the Tianjin fly ash. However, when treated by the wet-carbonated-washing method, the Cl removal ratio decreased by approximately 2%. This may be caused by the capture or capsulation effect of some newly formed precipitates (e.g. calcite). Based on these results, we conclude that the intrinsic property of the ash samples especially the chemical forms of the chlorine-containing salts and their fractions in the MSWI fly ash pose a significant influence on chloride removal. Therefore, MSWI fly ash dechlorination should be a property-oriented process in industrial-scale applications in order to make it cost-effective.
|寄稿の翻訳タイトル||Effect of intrinsic property of MSWI fly ash on dechlorination: Illustrated by two ash samples from Chongqing and Tianjin|
|ジャーナル||Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae|
|出版ステータス||出版済み - 12月 26 2021|
!!!All Science Journal Classification (ASJC) codes