摘要
采用不同溶剂对褐煤、焦煤、低级无烟煤(Ro,max2.62%)以及中级无烟煤(Ro,max3.74%)等四个煤级煤样进行分级超声萃取,然后对原煤和萃余物进行平衡水预湿的方法,进行了等温吸附实验,并结合孔隙结构测试和水分含量变化,分析了溶剂萃取后萃余物的吸附性能变化及其影响因素。研究发现:(1)平衡水条件下,原煤对甲烷的吸附能力要大于萃余物,萃取后,尽管煤的组成和孔隙结构发生了变化,但并不能改变不同煤级煤吸附甲烷的能力的对比关系;(2)原煤和各级萃余物都发生了到某一压力后,吸附量随着压力增加而下降的现象,褐煤及其萃余物甚至出现负值,这可能是由超临界状态下吸附相的体积忽视后带来的效应和煤基质在压力、水分作用发生膨胀以及随着压力增加,水分在吸附孔隙中占据吸附点位的增多,造成甲烷有效吸附点位的减少等综合作用的结果。研究认为,在讨论影响不同煤化作用的煤吸附能力的因素时,应该首先考虑到煤级对吸附能力的影响;对煤化程度相近的煤,其他因素如孔隙结构和水分的变化对吸附的影响才显现,但对不同煤级煤吸附性的主要影响因素也不尽相同。在煤层气吸附研究中,吸附量下降现象应该是一个共性,其机理的解释和寻求正确的吸附相体积校正,以及一定压力下,煤基质在水分作用下发生膨胀对吸附性的影响的规律描述,都是亟待解决的重要问题。
Using the fractional ultrasonic-extraction on four different-rank coals, including lignite, coking coal, low- and mid-metamorphism anthracites by different solvent, isotherm adsorption experiment was made after equilibrium-water accessioned into raw coals and their residues. The change of the adsorption capacity and its affecting factors were analyzed combined with the pore-structure and equilibrium-water content measurement. The results show that the CI-I4-adsorption capacity of raw coals is stronger than that of theirs residues under the condition of the equilibrium-water samples. Although the pore-structure and the water content have changed, the relationship of CH4-adsorption capacity between different raw coals and their corresponding residues has not changed. The adsorption capacity decreases with the increase of adsorption equilibrium pressure after the pressure reaches a certain value, and the adsorption volume of lignite and its residues can even be less then zero. This phenomenon is maybe caused by the ignorance of the adsorption-phase＇s volume under super-critical temperature state, the swelling effect of coal body under the action of pressure and water and the decrease of the efficient adsorption space for CH4 by the increase of water adsorption capacity in the pore with increasing pressure. It is concluded that when discussing the affecting factors of the adsorption capacity of different rank coals, the coal rank should be the primary factor, and the others, such as pore-structure and water content, are the secondary ones. And the main control- factor varies with different rank coals. The phenomenon of the decrease of adsorption capacity is common in the research of adsorption of coal-bed methane, and these problems, such as the explanation of the mechanism of the decrease of adsorption capacity, the establishment of the adsorption-phase volume correction formula and the discovery of the swelling effect of coal body on the adsorption capacity of coal need prompt solution.
出处
《地球化学》
CAS
CSCD
北大核心
2006年第5期567-574,共8页
Geochimica
基金
国家重点基础研究发展计划项目(2002CB211704
2002CB211703)
河南理工大学博士基金(648513)
关键词
煤
分级萃取
孔隙结构
平衡水含量
等温吸附
coal
fractional extraction
pore-structure
equilibrium-water content
isotherm adsorption
