Abstract: Circulating fluidized bed combustion experiments of three typical coals (lignite, bituminite and anthracite) were performed in a bench-scale combustor. Mercury migration between flue gas and fly ash in three typical coals was studied. The mercury migration for different coals were similar under different conditions of furnace temperature, wind speed, and coal grain size. With decreasing temperature in the furnace dense-phase zone and increasing empty section wind speed, the conversion of fly cash particles mercury (Hg(p)) increased, and the conversion of flue gas gaseous elemental mercury Hg⁰(g) into Hg²⁺(g) and Hg(p) also increased. As coal feed increased, Flue gas gaseous mercury Hg^T(g) content and elemental mercury content decreased, however fly ash particles mercury Hg(p) levels increased, meanwhile the transformation of Hg⁰(g) was affected. An appropriate coal grain size could promote the conversion of Hg⁰(g) and the migration of flue gas Hg^T(g) to fly ash. Hg^T(g), Hg(p) and Hg⁰(g) contents of lignite, bituminite and anthracite had similar changing trend, but differed widely under different combustion conditions. Meanwhile, the percentages of flue gas elemental mercury Hg⁰(g) in total flue gas mercury Hg^T(g) were also different, and that of anthracite was much higher than those of lignite and bituminite under various combustion conditions.

Key words: circulating fluidized bed, coal combustion, mercury, migration, flue gas

摘要： 在小型热态循环流化床试验台上进行褐煤、烟煤、无烟煤燃烧试验，研究3种典型煤的烟气气态汞和飞灰颗粒汞迁移规律。试验结果表明：褐煤、烟煤、无烟煤在燃烧过程中，炉膛温度、空截面风速、给煤量以及煤颗粒大小变化时，汞元素在烟气和飞灰之间的迁移规律相似；降低炉膛密相区温度和增大炉膛空截面风速可促进烟气气态总汞Hg^T（g）迁移到飞灰颗粒汞Hg（p）中，同时也促进烟气气态零价汞Hg⁰（g）向烟气气态二价汞Hg²⁺（g）和Hg（p）转化；增加给煤量，烟气气态总汞Hg^T（g）和烟气气态零价汞Hg⁰（g）减少，飞灰颗粒汞Hg（p）含量增加，并且影响Hg⁰（g）的转化；选择合适的煤颗粒粒度可以促进Hg⁰（g）的转化以及Hg^T（g）向Hg（p）迁移。随燃烧工况的变化，3种煤Hg^T（g）、Hg（p）和Hg⁰（g）含量变化趋势相似，但含量相差较大，Hg⁰（g）占Hg^T（g）的比例y值也不同，其中无烟煤的y值高于烟煤和褐煤的y值。

关键词: 循环流化床, 煤燃烧, 汞, 迁移, 烟气