Effect of NO on the performance of Cu-Mn spinel sorbent in the removal of Hg0 from flue gas
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摘要: 采用实验与量子化学计算相结合的方法研究了烟气中NO对铜-锰尖晶石脱汞性能的影响机理。结果表明，NO在高于250 ℃时抑制铜-锰尖晶石对Hg0的脱除，主要归因于NO与Hg0之间的竞争吸附作用；而在温度低于250 ℃时，NO对铜-锰尖晶石的Hg0脱除性能影响较小。吸附剂表面上吸附的汞主要以Cu-Hg合金和Hg(NO3)2的形式存在。铜-锰尖晶石表面上部分NO被氧化成NO2并与吸附态汞反应形成Hg(NO3)2。吸附剂表面上Cu和Mn原子为NO与Hg0的吸附活性位点，NO的吸附能大于Hg0的吸附能；因此，NO与Hg0之间存在竞争吸附。由于Cu、Mn、N原子之间的强烈轨道杂化作用，NO与铜-锰尖晶石吸附剂表面之间具有较强的相互作用。Abstract: The effect of NO on the performance of Cu-Mn spinel sorbent in the removal of Hg0 from flue gas was investigated by using experimental and density functional theory (DFT) calculation methods. The results indicate that NO shows slightly inhibitory effect on the Hg0 removal on the CuMn2O4 sorbent at high temperature (>250 ℃), probably due to the competitive adsorption between NO and Hg0 on the sorbent surface. At low temperature (< 250 ℃), NO has little influence on the Hg0 removal. The mercury species adsorbed on the CuMn2O4 sorbent exist mainly in the forms of Cu-Hg amalgam and Hg(NO3)2. NO can be oxidized into NO2 over the CuMn2O4 sorbent and NO2 then react with adsorbed mercury to form Hg(NO3)2. Cu and Mn atoms are identified as the active sites for the adsorption of NO and Hg0. There is a strong interaction between NO and CuMn2O4 surface, which is closely associated with the orbital hybridization of Cu, Mn, and N atoms.
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Key words:
- Hg0 adsorption /
- Cu-Mn spinel /
- NO /
- adsorption mechanism /
- quantum chemistry calculation
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图 1 NO对CuMn2O4吸附剂脱汞性能的影响
Figure 1 Effect of NO on the performance of CuMn2O4 sorbent in the removal of Hg0 from the simulated flue gas consisting of 4% O2, 12% CO2, 3×10-4 NO and N2 as balance gas
图 2 NO体积分数对CuMn2O4吸附剂脱汞性能的影响
Figure 2 Effect of NO concentration on the Hg0 removal over the CuMn2O4 sorbent from the simulated flue gas with the composition of 4% O2, 12% CO2, 0-8×10-4 NO and N2 as balance gas
图 3 吸附剂在4% O2、12% CO2、0和3×10-4 NO、N2作为平衡气体条件下脱汞实验后的程序升温脱附曲线
Figure 3 Temperature programmed desorption profiles of mercury from the spent CuMn2O4 sorbent after the Hg0 removal test from the flue gas with the composition of 4% O2, 12% CO2, 3×10-4 NO, N2 balance gas
图 4 NO在CuMn2O4表面上的吸附能和稳定优化结构
Figure 4 Adsorption energies and optimized structures of NO on the CuMn2O4 surface
图 5 NO在CuMn2O4表面上稳定吸附结构的原子投影态密度
Figure 5 Density of states (DOS) of NO adsorption on the CuMn2O4 surface
(a): DOS of Cu atom during NO adsorption on Cu site; (b): DOS of Mn atom during NO adsorption on Mn site; (c): DOS of N atom during NO adsorption on Cu site; (d): DOS of N atom during NO adsorption on Mn site
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