零价汞在MnO_x/α-Al_2O_3-氯气体系中的催化氧化

Catalytic oxidation of elemental mercury in flue gas over MnO_x/α-Al_2O_3 with chlorine

为强化烟气中零价汞向二价汞的转化,利用模拟含汞烟气研究了以MnOx/α-Al2O3作为催化剂、利用氯气作为氧化剂催化氧化零价汞的方法.着重考察了氯气浓度、温度、空速和SO2对催化氧化零价汞性能的影响,并与HCl作为氧化剂的结果进行了对比.同时,对催化剂进行表征,探讨了催化剂表面吸附态汞的形态.研究结果表明,Cl2较HCl更易活化且活性温度区间更广,在100～300℃范围内,Cl2体积分数为2.0×10-6时的催化氧化效率即可达80%以上;在1.6×104～6.4×104h-1空速范围内,零价汞氧化率保持在90%以上,空速继续提高到1.92×105h-1时,零价汞氧化率呈现线性下降趋势;烟气中的SO2与Cl2反应会消耗Cl2,Cl2体积分数低时对催化氧化反应抑制作用显著,但Cl2体积分数增至5.0×10-6时对催化氧化反应的抑制效果较弱,仅为10%左右.

In order to enhance the oxidation of elemental mercury to oxidized mercury, which is readily captured by flue gas desulfurization （FGD）, MnOx/α-Al2O3 was employed as the catalyst to convert Hg^0 to Hg^2＋ in the presence of chlorine gas. The main factors that affect the catalytic performance were investigated, such as the concentration of Cl2 , temperature, space velocity and SO2. The results revealed that Cl2 was more reactive than HCl over a wider temperature range, and more than 80% of Hg^0 oxidation efficiency was achieved with a 2.0 ×10^-6 volume fraction of Cl2 between 100 - 300 ℃. The oxidation efficiency remained over 90% while the space velocity increased from 1.6 ×10^4 h^-1 to 6.4×10^4 h^-1. The Hg^0 oxidation efficiency was inhibited by SO2 when the volume fraction of Cl2 was less than 2.0 ×10^-6, but the inhibitory effect was only 10% when Cl2 was above 5.0 ×10^-6