高碱低阶煤热解及热解半焦研究进展

我国碱金属、碱土金属(AAEM)含量高的低阶煤储量丰富。高碱含量造成锅炉受热面结渣沾污及气化炉结块腐蚀等难题,低阶煤内水高、氧含量高、挥发分高、发热量低以及易氧化自燃等特性为其储、运、用带来极大的难题。热解可生产优质燃料和高附加值化工原料,也是燃烧、气化、直接液化等过程的起始阶段和/或伴随反应,煤在热解阶段发生的反应、经历的变化,对煤转化利用的效率和清洁程度起重要、甚至决定性作用。笔者对煤热解与热解半焦研究及进展进行综述性评价,着重探讨煤中AAEM对热解过程及半焦的影响。结果表明,热解研究装置模拟的工况与现代煤化工过程中煤热解所处环境相差甚远,半焦样的代表性不强使热解研究成果的指导意义不大;对煤中不同赋存形态AAEM的分离方法有待完善,还需筛选、尝试新的萃取试剂;基本掌握了煤热解过程中AAEM的变迁行为,但尚缺乏控制煤中AAEM危害的有效方法。高碱低阶煤的安全高效洁净转化利用技术仍待突破。

Research progress on pyrolysis and pyrolysis of char of low-rank coal with high alkali

Resources of low rank coal with high content of alkali and alkaline earth metals( AAEM) are rich in China. The serious problems,including slag-bonding,staining,erosion and agglomerating in boiler and gasifier,are caused due to high AAEM in coal. Meanwhile,low-rank coal is often characterized by particular features,such as high moisture content,high oxygen content,high volatile content,low caloric value and ease of spontaneous ignition,which bring great difficulties to its storage,transportation and utilization.Pyrolysis can produce high-quality fuel and high value-added chemical raw materials. Besides,pyrolysis can also be considered as the initial stage and/or paralleling part of coal combustion,gasification and liquefaction,and the reactions and behaviors in coal pyrolysis play an important and even decisive role in the thermal conversion of low rank coal. In the paper,a critical survey of investigation into coal pyrolysis and characterization of char derived from coal pyrolysis was presented,with emphasis on the influence of AAEM on coal pyrolysis. The results show that the apparatus and equipment used for pyrolysis study in labs and the set of experimental parameters are far from that in the process of modern coal chemical industry,and the representativeness of Semicoke sample is not strong enough to guide the research results of pyrolysis. The occurrence mode and separation method of AAEM in coal need to be improved and new extraction reagents need to be screened and tried. Although the behavior of AAEM in coal pyrolysis is basically grasped,there is not an effective method to reduce the harm of AAEM in coal thermal conversion process. Thus,safe,efficient and clean utilization of high AAEM low rank coal awaits researching and developing further.