煤基活性炭定向制备:原理·方法·应用

依托丰富的煤炭资源,我国成为世界上最大的煤基活性炭生产国。简要回顾了我国煤基活性炭工业的起源和发展历程,介绍了煤基活性炭的制备方法、生产工艺及应用现状,分析影响活性炭合理应用的因素,着重讨论了活性炭定向制备的概念、原理、方法及应用,提出了我国活性炭工业发展面临的重要问题和亟待研究的课题。结果表明:活性炭具有发达的孔隙结构,依据其对气、液相中微量成分选择性吸附的能力,在国防、医药、食品、化工行业得到广泛应用,近年来在能源、环境领域发现极大的应用前景;物理活化法是煤基活性炭制备的基本方法,原煤破碎活性炭、柱状活性炭及压块活性炭工艺是目前煤基活性炭的主要工业生产工艺,尤其是压块活性炭工艺,由于产能大、产品质量高且稳定并适于配煤、添加剂调孔,已成为新建、扩建活性炭企业的首选;孔结构、表面化学、形状、机械强度、流体力学性能等是影响活性炭应用的主要因素,"活性炭定向制备"即以用途对活性炭组成、结构和性能的要求为导向,制备具有适宜组成、孔结构、应用性能的活性炭产品,按照煤基活性炭定向制备涉及的指标及相互关系、影响因素、调控方法及难度,以孔结构调节为中心开发煤基活性炭定向制备技术成为主要策略;孔结构调控是在保证活性炭孔隙充分发育的前提下根据应用需求调节活性炭不同尺寸孔在总孔容中的比例,筛选原料煤、配煤、添加剂、优化工艺参数等措施,可以在不同程度上控制炭化过程,使炭化向生成各向同性、非石墨化、反应活性高、初生孔隙发达炭化物的方向发展,为活化阶段活化剂-炭基质间反应速度的调变打下基础,易于孔结构调控;煤基活性炭定向制备技术已应用于低灰高比表面积活性炭、磁性活性炭及兼有双电层电容和法拉第电容的高容量电极炭的研制,此外,在单种活性炭难以满足应用途径对活性炭提出的综合性能指标要求的情况下,配炭或是一种有效的解决途径。活性炭孔结构的精准量化调控、中孔活性炭的制备、配炭等研究尚待进一步深入;活性炭应用研究,利用西部高碱煤中内源性碱(土)金属调控煤基活性炭孔结构,开发洁净活性炭生产工艺,是煤基活性炭定向制备面临的新课题。

Directional preparation of coal-based activated carbon:principles,approaches and applications

China is rich in abundant coal resources and has become the largest coal-based activated carbon producer in the world.A con?cise history of origin and development of coal-based activated carbon industry in China,as well as a brief introduction to the preparation method,technology and application of coal-based activated carbon were conducted in this paper.Then the concept,principles,approa?ches and applications of directional preparation of activated carbon(DPAC)were presented in detail.Besides,several important issues faced by the activated carbon industry in the near future were figured out and some urgent topics to be investigated were proposed.The re?sults show that activated carbon has developed pore structure with unique ability in selective adsorption of trace components in gas and liq?uid phase,and has been widely used in national defense,medicine,food and chemical industry,and in recent years,it has found great application prospects in energy and environment fields.Steam activation is the dominating method for the production of coal-based activa?ted carbon.At present,crushed coal-based activated carbon,extruded activated carbon and especially the briquetted activated carbon are the primary products of coal-based activated carbon industry.The briquetted activated carbon production technology has become the priori?ty process for the newly-built or expanded activated carbon plant,because it is characterized as large production capacity,high and stable product quality,especially suitable for pore adjustment by coal blending and additives.It is well known that pore texture,surface chemis?try,shape and forms,mechanical strength and fluid characteristics are the influencing factors when activated carbon are utilized.DPAC,i.e.activated carbon with suitable composition,pore texture and kinds of specifications is turned out strictly in accordance with the re?quirements of application.When all factors relating to DPAC,including specifications of activated carbon and their interactions,influen?cing factors,adjusting methods and complexity were all taken into account,a strategy for development of DPAC could be made out,in which the regulation of pore texture is both the obstacle and the core.Pore texture regulation is to adjust the proportion of pores with dif?ferent sizes in the total pore volume of activated carbon according to the application requirements on the premise of ensuring the full de?velopment of pores in activated carbon.When the measures,such as selecting feedstock coal,coal blending,additives and process pa?rameters optimization were adopted alone or simultaneously,the carbonization process of coal can be controlled to some extent and pro?ceeds in the direction of producing isotropic,non-graphitizable char with high reactivity and developed preliminary pores,which will lay a foundation for the adjusting steam-carbon matrix reaction rate and porosity development in the activation process,consequently results in the pore texture regulation.Thus,low ash and high specific surface area activated carbon,magnetic activated carbon and activated carbon for electrode with double electric layer capacitance and Faraday capacitance,can be directionally prepared with the application of principles of DPAC.In the case that a single kind of activated carbon is impossible to meet a set of requirements demanded by an appli?cation,carbon blending may be an efficient alternative.With the aim to further improvement of preparation technology of coal based acti?vated carbon,focuses should be paid on the precise and quantitative control of the pore texture of activated carbon on industrial scale,the preparation of mesoporous activated carbon and carbon blending.Meanwhile,study of the activated carbon application,exploitation of inner alkali and alkaline earth metals in western coal in controlling over the pore texture of activated carbon,as well as establishment of cleaner manufacturing process of activated carbon are the important issues in development of coal based activated carbon industry in our country.