汞具有挥发性且有剧毒，是煤中有害痕量重金属元素之一。在燃烧过程中，燃煤中的汞主要以Hg0的形式释放到烟气中。烟气中的Cl元素可将Hg0高效氧化成Hg2+，Hg2+可在下游的除尘和湿法脱硫设备中被捕集脱除。然而，我国燃煤大部分属于低氯煤，燃煤电厂烟气中Hg0比例较高，造成电厂现有烟气污染物控制单元对Hg0的协同脱除效率较低。针对我国燃煤氯含量较低，烟气中Hg0氧化效果差，Hg0含量高的问题，提出利用4种氯盐对堇青石进行浸渍改性，制备成MClx/Cord吸附剂，对该吸附剂进行较宽温度窗口的Hg0氧化试验，探究氯盐改性堇青石对Hg0的氧化性能。结果表明：在0～8% O2体积分数和150～350 ℃时，堇青石载体Hg0脱除效率最高仅8%；而用CaCl2、MgCl2、FeCl3和CuCl2改性后堇青石吸附剂的Hg0脱除效率分别达30%、95%、97%和98%。可见，氯盐改性极大提高了堇青石吸附剂氧化Hg0的性能。温度和O2体积分数对MgCl2/Cord、CaCl2/Cord和FeCl3/Cord吸附剂中的氯元素析出影响很大，造成Hg0脱除效率波动较大。CuCl2/Cord的Hg0脱除效率受温度和O2体积分数影响不大，Hg0脱除效率稳定在93%以上，表现出非常稳定的氧化Hg0性能，适合作为氧化烟气中Hg0的潜在吸附剂。氯盐浸渍改性可提高堇青石对Hg0的氧化性能，CuCl2浸渍改性堇青石具有最佳的Hg0氧化效果，且几乎不受温度和O2体积分数变化的影响。

Mercury is one of the harmful trace heavy metal elements in coal with strong volatility and toxicity. During coal combustion,mercury is mainly released into the flue gas in the form of Hg0. The element Cl in flue gas can efficiently oxidize Hg0 to Hg2+,and then Hg2+ can be removed in downstream dust removal and wet desulfurization facilities. However,most of the coal in China belongs to low-chlorine coal,resulting in a high proportion of Hg0 in flue gas,and the low mercury removal efficiency of existing flue gas pollutant control units in power plants. In order to solve the problems of low chlorine content,poor oxidation effect and high content of Hg0 in flue,it was proposed to impregnate cordierite with four kinds of chlorine salts to prepare MClx/Cord adsorbent. The Hg0 oxidation experiment of the adsorbent with a wide temperature window was carried out to explore the oxidation performance of cordierite modified by chlorine salts to Hg0. The results show that in the range of 0-8% O2 content and 150-350 ℃,the highest Hg0 removal efficiency of cordierite is only 8%,while that of cordierite sorbents modified with CaCl2,MgCl2,FeCl3 and CuCl2 reach 30,95,97 and 98%,respectively. It can be seen that the chlorine salts greatly improve the performance of cordierite sorbents for removal of Hg0. The temperature and oxygen content have great influence on the Hg0 removal performance of MgCl2/Cord,CaCl2/Cord and FeCl3/Cord. The temperature and O2 content have little influence on the Hg0 removal efficiency of CuCl2/Cord,which is always more than 93%. CuCl2/Cord shows a stable performance on mercury oxidation removal,so it is suitable to be used as a potential oxidation sorbent for oxidation and adsorption removal of Hg0 from flue gas. Chlorine salt impregnation modification can improve the oxidation performance of cordierite to Hg0. Cordierite modified by CuCl2 impregnation has the best Hg0 oxidation effect,and it is almost not affected by the change of temperature and O2 content.

0 引言

1 试验

   1.1 吸附剂的制备

   1.2 评价系统

2 结果与讨论

   2.1 表征分析

   2.2 氯盐改性堇青石脱汞性能试验

   2.3 MClx/Cord吸附剂氧化吸附Hg0性能对比

3 结论