电厂煤燃烧后元素硒的分布及对环境的贡献

对电厂煤、除尘器飞灰、渣及不同粒径的烟道飞灰中痕量元素硒进行研究.化学分析表明,硒在渣和除尘器飞灰中亏损而在细飞灰中富集,尤其在>19.0μm的飞灰中明显富集,富集系数达到5.15,造成这种现象的原因一是挥发性元素的挥发-凝结作用,二是燃烧产物在燃烧气流中停留的时间,三与飞灰颗粒形态有关,>19.0μm的飞灰中多孔颗粒可能是造成其富集的原因.逐级化学提取实验表明,煤中硒主要具有机相关性(69.7%),这也是硒挥发性高的一个主要原因;物质平衡计算显示煤中16.5%的硒随气流直接排放入大气,细飞灰中的硒只占1.1%,且大部分在>19.0μm的飞灰中,影响范围小,渣中硒对周围环境的影响更小,飞灰中的硒具有一定的迁移性,也许可以用来改善缺硒土壤.

Distributions and Environmental Impacts of Selenium in Wastes of Coal from a Power Plant

Samples of coals, fly ashes, slags and tiny fly ashes with different sizes, collected from a large power plant, were studied. It shows that Se tends not to be enriched in coarse fly ash and slag, but to be enriched in fine fly ashes especially in fine fly ash with size > 19.0 microm. This kind of distribution is shaped by: 1) volatility and organic-occurrence of Se in coal; 2) residence time in flue gases; 3) morphology of particles [holes on the surface of particles ( > 19.0 microm) may adsorb more Se]. Sequence leaching test shows that Se is mainly organic-bonded (69.7%) in coal. Mass balance calculation of burned coal indicates that 16.5% of Se in coal may be disposed into air directly. The environmental impacts of Se in fine fly ashes can be ignored because of its small proportion and distributional character (mainly in particles with sizes > 19.0 microm). Se in slag may cause little environmental impacts. Se in coarse fly ash is partially mobile and may be used to benefit the soil which is lack of Se.