低温等离子体强化燃煤烟气Hg^0氧化的气氛影响及特性分析

Influence of gas composition and characteristic analysis on oxidation of Hg^0 in coal-fired flue gas by non-thermal plasma

为了研究燃煤烟气成分对低温等离子体氧化元素汞的影响,以石英玻璃管为阻挡介质,内插不锈钢棒为高压放电极,利用交流高压放电产生低温等离子体强化模拟烟气中Hg^0氧化.研究输入能量和烟气成分对模拟烟气中Hg^0形态转化与协同脱硫脱硝的影响规律.结果表明,初始时Hg^0氧化率随输入能量增大而提高,原因是模拟烟气中O_2分解产生的O自由基数目增多,但输入能量过大会促使模拟烟气中N_2分解,生成NO并消耗O自由基,导致Hg^0氧化率下降.烟气中O_2和CO_2含量增大,分解产生的自由基O数量增多,有利于Hg^0氧化反应.低温等离子可将NO和SO_2分解成N2和S,同时产生能够促进Hg^0氧化的O自由基,因此低温等离子促进NO和SO_2氧化Hg^0的同时可实现脱硫脱硝的目的.

To study the effect of coal-fired flue gas composition on the oxidation of Hg^0 by using non-thermal plasma,the quartz glass tube and the stainless steel rode were used as the barrier medium and the high voltage discharge electrode,respectively,and the Hg^0 in simulated flue gas was oxidized by alternative current high voltage discharge non-thermal plasma. The effects of input energy and gas composition on the mercury speciation transformation and the simultaneous desulfurization and denitration in simulated flue gas were investigated. The results showthat the oxidation efficiency of Hg^0 increases with the increase of the input energy in the initial stage. The reason is that the contents of free radical O increases by O2 decomposition,but N_2 in simulated flue gas decomposes when the input energy is large enough,which consumes free radical O and produces NO,leading to the decrease of elemental mercury oxidation efficiency. The content of free radical O increases with the increase of the contents of O_2 and CO_2 in simulated flue gas,which can promote Hg^0 oxidation. NO and SO_2 can be decomposed into N_2 and S by non-thermal plasma,and free radical O which can oxidize Hg^0 is simultaneously produced. Therefore,non-thermal plasma can promote NO and SO_2 to react with Hg^0 and realize desulfurization and denitration.