The control of mercury in the air emissions from coal-fired power plants is an on-going challenge. The native unburned carbons in fly ash can capture varying amounts of Hg depending upon the temperature and composition of the flue gas at the air pollution control device, with Hg capture increasing with a decrease in temperature; the amount of carbon in the fly ash, with Hg capture increasing with an increase in carbon; and the form of the carbon and the consequent surface area of the carbon, with Hg capture increasing with an increase in surface area. The latter is influenced by the rank of the feed coal, with carbons derived from the combustion of low-rank coals having a greater surface area than carbons from bituminous- and anthracite-rank coals. The chemistry of the feed coal and the resulting composition of the flue gas enhances Hg capture by fly ash carbons. This is particularly evident in the correlation of feed coal Cl content to Hg oxidation to HgCl2, enhancing Hg capture. Acid gases, including HCl and H2SO4 and the combination of HCl and NO2, in the flue gas can enhance the oxidation of Hg. In this presentation, we discuss the transport of Hg through the boiler and pollution control systems, the mechanisms of Hg oxidation, and the parameters controlling Hg capture by coal-derived fly ash carbons.

中文翻译：

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燃煤电厂中原生飞灰碳捕获汞

控制燃煤电厂空气排放中的汞是一项持续的挑战。根据空气污染控制装置中烟气的温度和成分，飞灰中未燃烧的原生碳可以捕获不同数量的汞，其中汞捕获量随温度降低而增加；飞灰中的碳量，随着碳的增加，汞的捕获量增加；以及碳的形式和随之而来的碳表面积，Hg 捕获量随着表面积的增加而增加。后者受进料煤的等级影响，来自低级煤燃烧的碳比来自烟煤和无烟煤级的碳具有更大的表面积。进料煤的化学性质和由此产生的烟道气组成增强了飞灰碳对汞的捕获。这在进料煤 Cl 含量与 Hg 氧化为 HgCl2 的相关性中尤为明显，从而增强了 Hg 捕获。烟气中的酸性气体，包括 HCl 和 H2SO4 以及 HCl 和 NO2 的组合，可以增强 Hg 的氧化。在本演讲中，我们讨论了汞通过锅炉和污染控制系统的传输、汞氧化的机制以及控制煤粉飞灰碳捕获汞的参数。