Influence of thermal treatment condition on release behavior of selenium in coals
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摘要: 利用固定床热解反应装置，研究了平朔、兖州、神华、黑代沟、义马、霍林河和曲靖七种煤中硒在氮气气氛下，200℃～1000℃的热稳定性，考察了加热速率、终温停留时间、气氛（氮气、空气与氢气）对黑代沟和霍林河煤中硒释放规律的影响。结果表明，热解条件下煤中硒主要在700℃以下释放，700℃时的释放率为34%～63%。烟煤中硒的释放峰温在500℃左右，而褐煤中硒的释放峰温在400℃左右。500℃以上，加热速率对煤中硒的释放有一定的影响，较低的加热速率可获得较高释放率；终温1000℃时，停留时间从0延长至15min可明显提高硒的释放率，继续延长停留时间，硒的释放率没有进一步提高。与氮气气氛相比，空气气氛明显促进硒的释放，氢气气氛次之。在热解实验条件下，七种煤中的硒均没有在半焦中富集。Abstract: Release behaviors of selenium (Se) during pyrolysis of seven Chinese coals were studied at 200℃～1000℃ in a quartz tube fixed-bed reactor. Effects of heating rate, residence time and atmosphere on the release of Se in HDG and HLH coals were investigated. The results show that the release of Se mainly occurs below 700℃. The release ratio of Se is about 34%~63% at 700℃. The release of Se is peaked at 500℃ for bituminous coal and 400℃ for lignite, respectively. There is no significant effect of heating rate on the release ratio of Se when temperature is lower than 500℃. However, the lower heating rate leads to the higher release ratio of Se above 500℃. At 1000℃, the release ratio of Se increased with residence time within the first 15min, while there is no significant change with the further increase of the time. In comparison with N2 atmosphere, both air and H2 promote the release of Se, especially the air atmosphere. Under the experimental conditions, no Se enrichment in pyrolysis char is observed.
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