Senior Constance, Granite Evan, Linak William, Seames Wayne
National Institute of Clean and Low-carbon Energy, Beijing, China.
U.S. Department of Energy, National Energy Technology Laboratory, Pittsburgh, Pennsylvania, USA.
Energy Fuels. 2020 Sep 23;34(12):15141-15168. doi: 10.1021/acs.energyfuels.0c02375.
Coal fueled the Industrial Revolution and the global expansion of electrification in the 20 century. In the 21st century, coal use has declined in North America and Europe, but continues to increase in Asia. Coal contains many of the elements of the Periodic Table, in percent-levels or in trace amounts (ppm, ppb). The impact of many of these elements on the environment via air and water discharges from coal-fired plants has been studied with decades of research on their chemical transformations within combustion systems and on their fates upon reintroduction into the environment. The transformations of the trace elements present in coal burned during combustion can be categorized as thermal volatilizations from the coal in the furnace; thermal decomposition of trace element compounds inside the coal; encapsulation inside ash structures through high-temperature vitrification; oxidation of the trace elements with the myriad species contained in flue gas through gas phase (homogeneous) reactions or catalytic (gas-solid) reactions; adsorption and/or reactions with active sites on entrained fly ash particulates contained in the flue gas; and absorption into solutions. These transformations can, in many cases, impact the fraction of these trace elements that are removed by various pollution control devices compared to the fraction released into the environment. The sampling and measurement of trace elements, in the inlet coal, outlet flue gas, aqueous scrubber solutions, and ash matrices, represents a significant challenge. This review focuses on the behavior of trace elements in industrial coal combustion systems with an emphasis on what has been learned over the past century uniquely related to the use of coal in boilers for electricity and heat production. Key accomplishments in measurement, modeling and control of trace element emissions in coal-fired systems are highlighted.
煤炭推动了工业革命以及20世纪电气化在全球的扩张。在21世纪，北美和欧洲的煤炭使用量有所下降，但在亚洲仍持续增长。煤炭含有元素周期表中的许多元素，含量为百分比水平或痕量（ppm、ppb）。通过对这些元素在燃烧系统内的化学转化以及重新引入环境后的归宿进行数十年研究，已考察了其中许多元素通过燃煤电厂的空气和水排放对环境的影响。燃烧过程中煤炭所含微量元素的转化可分为以下几类：炉内煤炭的热挥发；煤炭内部微量元素化合物的热分解；通过高温玻璃化被包裹在灰分结构中；微量元素与烟气中所含众多物质通过气相（均相）反应或催化（气固）反应发生氧化；与烟气中夹带的飞灰颗粒上的活性位点发生吸附和/或反应；以及被吸收到溶液中。在许多情况下，这些转化会影响与释放到环境中的部分相比，被各种污染控制装置去除的这些微量元素的比例。对入炉煤、出口烟气、湿法洗涤器溶液和灰分基质中的微量元素进行采样和测量是一项重大挑战。本综述重点关注工业煤炭燃烧系统中微量元素的行为，着重介绍过去一个世纪中与在用于发电和供热的锅炉中使用煤炭独特相关的知识。突出了燃煤系统中微量元素排放测量、建模和控制方面的主要成就。
