[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.