不定型煤基活性焦制备及预处理影响研究

Preparation and Pretreatment of Amorphous Coal-Based Activated Coke

我国煤炭燃烧排放大量的SO2和NOx等导致了严重的空气污染,需要寻找一种清洁高效的烟气联合脱硫脱硝技术.煤基活性焦因其脱除效率高,再生能力强等诸多优点备受关注,但目前的研究主要集中在柱状和粉末状活性焦上.为研究大粒径煤基活性焦的制备参数和预处理对活性焦理化特性的影响,对原煤颗粒进行高温空气预氧化处理,并通过炭化-水蒸气活化两步法制备活性焦.结果表明:低温长时间活化可使炭化料内部孔隙充分刻蚀,显著提高比表面积和孔容,以水蒸气作为活化剂有利于微孔和介孔协同发展,适合制备大粒径分级孔结构活性焦.700℃活化3 h制得的府谷煤活性焦比表面积为429.54 m^(2)/g,介孔占比27.80%;850℃活化3 h制得的大同煤活性焦比表面积为892.20 m^(2)/g,介孔占比21.46%.高温空气预氧化能够改变原煤内部结构,对府谷煤颗粒在200℃下预氧化15 h后,氧化煤内部成分和结构基本稳定,脂肪结构被消耗的同时生成了大量含氧官能团.预氧化处理对炭化过程的影响较为显著,氧化煤在炭化过程中热塑性特征显著降低,减少了焦油对孔隙的堵塞,此外,含氧官能团的交联作用也促进了煤中大分子的缩聚和孔隙的形成,从此促进初步孔隙的发展.虽然预氧化使得活性焦的比表面积和孔容都有所增大,但活化剂和样品之间的成孔路径未产生改变.

SO2 and NOx emitted from coal combustion lead to serious environmental pollution.It is necessary to find a clean and efficient combined desulfurization and denitrification technology.Coal-based activated coke has attracted much attention due to its advantages such as high removal efficiency and strong regeneration ability.However,the current studies mainly focus on columnar and powdered active coke.To study the effect of preparation parameters and pretreatment on the physicochemical properties of large particle size coal-based activated coke,raw coal particles were preoxidized by high temperature air.Then,activated coke was prepared by carbonization and steam activation.The results show that the pore structure of carbonized char can be fully developed by long time activation at relatively low temperature.The pore volume and specific surface area are significantly increased.Using water vapor as the activator is beneficial to the synergistic development of micropores and mesopores,which is suitable for the preparation of large particle size activated coke with hierarchical pore.The specific surface area and mesoporous ratio of Fugu activated coke prepared at 700℃for 3 h are 429.54 m^(2)/g and 27.80%,respectively.The values of Datong activated coke prepared at 850℃for 3 h are 892.20 m^(2)/g and 21.46%,respectively.The internal structure of raw coal is changed by high temperature air preoxidation.After 15 h preoxidation at 200℃,the internal chemical composition and structure of the oxidized coal are basically stable.A large number of oxygen-containing functional groups are formed during the consumption of the aliphatic structure.The influence of preoxidation on carbonization is rather obvious.The thermoplastic characteristic of oxidized coal during carbonization is significantly weakened,which reduces the pore blockage by tar.In addition,the condensation of macromolecules and the formation of pores are promoted by the cross-linking of oxygen-containing functional groups,which is beneficial to the pore development.Although the specific surface area and pore volume of the activated coke are both increased by preoxidation,the reaction path between the activator and the sample remains unchanged.