不同烟气组分对粉状活性焦吸附汞的影响机理

Effect mechanisms of different flue gas on adsorption of mercury by powder activated coke

在模拟燃煤热烟气为热源和介质条件下,以准东褐煤为原料,通过一维沉降炉进行炭化活化(一步法)制备粉状活性焦,考察了活性焦对Hg^0的吸附能力,探索了SO_2、H_2O、O_2、CO_2、H_2O+O_2、SO_2+O_2及H_2O+SO_2+O_2气氛对活性焦吸附Hg^0的影响机理。结果表明:一步法获得的活性焦对Hg^0具有较高的吸附性能。N_2气氛作对比,H_2O、H_2O+O_2、CO_2和SO_2气氛下抑制活性焦对Hg^0的吸附;O_2、SO_2+O_2和H_2O+SO_2+O_2促进活性焦对Hg^0的吸附。通过Hg 4f的XPS分析证明了不同气氛组成对活性焦吸附Hg^0的抑制和促进机理。H_2O覆盖在活性焦活性位上和堵塞孔隙而抑制活性焦对Hg^0的吸附;SO_2与Hg^0在活性焦上发生竞争吸附而抑制对Hg^0的吸附;CO_2吸附在活性焦微孔上而抑制对Hg^0的吸附;O_2气氛下主要形成了HgO, SO_2+O_2气氛下Hg^0被氧化成HgSO_3,进一步氧化成HgSO_4; H_2O+SO_2+O_2气氛下,Hg^0被氧化成HgO和HgSO_4。

Under the condition of simulating coal-fired hot flue gas as heat source and medium,quasi-east lignite was used as raw material to carry out carbonization activation(one-step method)to prepare powdery activated coke by one-dimensional settling furnace,and the adsorption capacity of activated coke to Hg0 was investigated.Further,the effects of SO2,H2O,O2,CO2,H2O+O2,SO2+O2 and H2O+SO2+O2 on Hg0 removal efficiency were examined in flue gas.The results indicate that the coke has high adsorption performance for Hg0 removal.The N2 atmosphere was used as comparison,the O2,SO2+O2 and H2O+SO2+O2 are beneficial for Hg0 removal,while the H2O,CO2,SO2 and H2O+O2 have inhibiting effect on Hg0 removal.Furthermore,the spectra of Hg 4f were determined by XPS,in order to explore the mechanism of inhibition and promotion of Hg0 adsorption by activated coke under different flue gas.H2O can inhibit the adsorption of active coke on Hg0 via covering the active coke sites and blocking the pores,SO2 can inhibit the adsorption through the competitive adsorption of SO2 and HgO on the active coke,and CO2 that adsorbed on the active coke micropore also can inhibit the adsorption of active coke on Hg0.In the atmosphere of O2 and SO2+O2,the Hg0 is oxidized into HgO and HgSO3,separately.And the HgSO3 further oxidized into HgSO4 by O2.Besides,in the atmosphere of H2O+SO2+O2,Hg0 is oxidized into HgO and HgSO4.