高岭土高温吸附重金属和碱金属的研究进展

A review on heavy and alkali metals adsorption by kaolin at high temperature

高岭土在高温下对碱金属和重金属具有吸附能力,可以解决煤、生物质和垃圾等在燃烧、气化等过程中产生的结渣、积灰、腐蚀以及重金属和超细颗粒物排放等问题。国内外学者已对此进行了长期研究,但仍存在相关的难度和问题,因此本文从高岭土高温结构特征、研究方法、高温吸附机理、高温吸附技术应用效果以及高岭土改性等5个方面介绍了相关重要成果,并结合前人研究成果和作者自身的研究经验,提出了本领域研究的展望。指出缺乏简便而准确的金属蒸气定量发生装置和在线检测装置严重阻碍了高岭土高温吸附的试验研究,亟待开发出对应的新方法或新设备;高岭土高温吸附的同时其结构因为高温也在发生畸变,掌握其中的关联是理解高温吸附行为的关键之一;烟气组分对吸附的影响研究仍不充分,因此目前无法形成复杂烟气组分下的高岭土高温吸附行为规律和数学描述;技术应用过程中,高岭土添加量较大(通常大于3%),可能对燃烧或气化工艺产生不良影响,抑制了其工业应用;高岭土改性是提升吸附效率、降低高岭土用量的有效方法,改性工艺仍有待深入研究,但因为吸附后高岭土难以分离回收和循环再生,改性成本必须低。

Kaolin has an ability to adsorb alkali and heavy metals at high temperatures, and can solve the problems such as slagging, ash accumulation, corrosion, and the emissions of heavy metals and ultrafine particles during the combustion or gasification of coal, biomass and garbage. The previous researchers have conducted long-term researches on this field, but there are still many related difficulties and problems. Therefore, this paper reviewed the previous research results and put forward the prospect. The important results were introduced from five aspects of kaolin high temperature structure characteristics,research methods, high temperature adsorption mechanisms, high temperature adsorption technology application and kaolin modification. Combining the research results of predecessors and the author’s own research experience, the prospect of research in this field was put forward. The lack of simple and accurate metal vapor quantification device and on-line detection device seriously hinders the experimental research on high-temperature adsorption of kaolin. It is urgent to develop a corresponding new method or new equipment. The high-temperature adsorption and the structure distortion due to high temperature happen at the same time. Therefore, the correlation is one of the keys to understanding the behavior of high temperature adsorption, which were mentioned rarely in the previous researches. The effect of flue gas components on adsorption is not well studied. Thus, the high temperature adsorption behavior and mathematical description of kaolin under complex atmospheres are not formed yet. In the application process, the addition proportion of kaolin is large(usually more than 3%), which may adversely affect the combustion or gasification process and inhibit its industrial application. It is a good way to improve the adsorption efficiency and reduce the usage amount of kaolin by kaolin modification,which still need to be further studied. However, since it is difficult to separate kaolin from fly ash and to regenerate or recycle, the modification cost must be low.