燃煤电站飞灰改性自吸附协同脱汞试验研究

Experimental study on mercury removal from a coal-fired power station using modified fly ash

为了实现高效低成本的汞污染控制,通过在超超临界1000 MW燃煤机组锅炉中加入飞灰改性剂,对飞灰进行实时改性,并在不同负荷下试验研究了飞灰改性对汞排放及迁移规律的影响。结果表明:加入飞灰改性剂促进了汞的氧化,对飞灰吸附脱汞的促进作用显著,而且飞灰颗粒越细,对汞的吸附能力越强;在900 MW负荷下,加入飞灰改性剂后,通过飞灰脱除的汞在总汞中的占比由原始的34.5%大幅提升至93.9%~97.9%,进入石膏和脱硫废水的汞占比小于1%,可有效防止石膏利用中的汞二次释放,飞灰改性剂加入量为40 mL/t时,烟气汞排放质量浓度降至0.14~0.20μg/m^(3),机组总脱汞率高达95.1%~98.1%,具有很好的脱汞效果;当机组负荷为500 MW时,飞灰改性剂的效果会有所降低,这可能与低负荷条件下,飞灰破碎减少、粒径增加、比表面积下降等因素有关。

In order to realize high-efficiency and low-cost mercury emission control,a fly ash modifier was added to a supercritical 1000 MW coal-fired boiler for fly ash real time modification.The influence of fly ash modification on mercury emission and migration were studied at different loads.The results showed that,the addition of the fly ash modifier promoted oxidation of mercury and significantly improved the mercury adsorption by fly ash.The finer the fly ash particle,the stronger the mercury adsorption capacity of the fly ash.At 900 MW,after adding the fly ash modifier,the ratio of the mercury removed by fly ash to the total mercury greatly increased from 34.5%to 93.9%~97.9%,and the ratio of the mercury entering gypsum and desulphurized waste water to the total mercury was less than 1%,so the secondary release of mercury during gypsum utilization can be prevented effectively.When the addition amount of the fly ash modifier was 40 mL/t,the mass concentration of the mercury emitted from flue gas decreased to 0.14~0.20μg/m^(3),and the overall mercury removal rate of the unit reached 95.1%~98.1%,indicating the mercury removal effect was good.At 500 MW,the effect of fly ash modifier showed to be reduced moderately,which might be related to the less fly ash cracking,larger particle size and smaller specific surface area under lower load conditions.