煤中氯的赋存与释放特性研究进展

氯是煤中重要的有害微量元素之一,在煤的热解,燃烧和气化过程中,煤中的氯经过复杂的化学变化转移到烟气中,形成多种含氯物质如HCl、Cl_2、无机盐等,这不仅造成环境的严重污染,危害人类的健康,同时氯元素的挥发会引起锅炉及尾部受热面的沾污结渣腐蚀问题,形成安全隐患。了解煤中氯的测定方法,赋存形态,释放规律及控制技术是高氯煤清洁利用的前提,本文对国内外这方面的研究工作进行了综述。介绍了煤中氯的来源及危害,并整理和比较了国内外煤中氯的测定方法的原理及其优缺点,统计了世界主要产煤国煤中氯含量分布范围、均值及典型煤样中氯含量的值;整理归纳了煤中氯的2种主要赋存形式:有机形态(包括无机离子、水合离子、无机盐和含氯复杂矿物)和无机形态(包括有机离子交换态、有机共价结合态、有机氯化物和有机离子配合物),并分类总结了3种煤中氯赋存形态的研究方法:相关性分析法,化学法萃取法,仪器直接分析法;阐述了煤燃烧、热解、气化过程中氯的释放特性及煤中氯形态、煤质、温度、升温速率、保温时间、压力、气氛等因素对氯释放规律的影响,对比了不同气氛下煤中氯的释放规律,并分析了在加热过程中煤焦和气态中氯形态及其分布的变化;分类总结了目前氯的主要控制技术,并比较了不同控制技术的特点及其适用工况;同时结合当前研究中存在的问题,提出了煤中氯的赋存、释放以及控制研究的若干工作建议,从而为高氯煤的高效清洁利用提供一定的理论基础。

Research advances on the occurrence and release characteristics of chlorine in coal

Chlorine is an important element of harmful trace elements in coal. During the pyrolysis,the combustion and gasification of coal,chlorine would be migrated to flue gas by complex chemical reactions,existed in the forms of various chlorine substances,such as HCl,Cl2 and inorganic salts. It would cause serious pollution to the environment,and endanger human health. At the same time,the volatilization of chlorine would cause slag corrosion problems on the boiler and heated exchange surface,causing safety hazards. It is the premise of clean utilization of high-chlorine coal to understand the determination methods,occurrence forms,release characteristics and control technologies of chlorine in coal. This paper reriewed the relevant research works in this field. Also,the sources and hazards of chlorine in coal,as well as the different methods for determining chlorine content were introduced. The distribution range and mean value of chlorine content around the world were counted,and the chlorine content of typical coals were listed. Then,two main occurrence forms of chlorine in coal are summarized,which are organic forms (including inorganic ions,hydrated ions,inorganic salts and complex minerals) and in-organic forms (including organic exchange ion,organic bond covalent state,organic chloride and organic ion complexes). Meanwhile,three research methods of chlorine occurrence were classified,including correlation analysis method,chemical extraction method and instrument direct analysis method. In addition,this paper described the release characteristics of chlorine during combustion,pyrolysis and gasification of coal. A series of factors which have influence on the release of chlorine were studied,such as chlorine forms,coal characteristics, temperature,heating rate,holding time,pressure and atmosphere. Besides,the changes of chlorine forms and its distribution in char and gaseous during heating were analyzed. At the same time,the main chlorine control technologies and their applicable working conditions were summarized and compared. Lastly,some suggestions were proposed for the investigation regarding the occurrence,release and control of chlorine in coal,which would provide a theoretical basis for the efficient and clean utilization of high-chlorine coal.