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温度冲击作用对无烟煤甲烷吸附-解吸特性影响的试验研究

Experimental study on adsorption and desorption characteristics of anthracite by temperature shock

  • 摘要: 无烟煤具有甲烷吸附性强解吸率低的特点,为了提高无烟煤中煤层气的抽采效率,选用温度冲击作为改性方法。采用SN-GDCJ-150高低温冲击试验箱对无烟煤样进行了温度冲击改性试验,试验方案为4因素4水平组成的16组正交试验方案。所选取的4因素4水平为高温温度50、100、150、200 ℃;低温温度-10、-30、-50、-70 ℃;作用时间10、30、50、70 min;循环次数1、3、5、7次。将正交试验方案中各试验方案的高温温度和低温温度的温差与试验所用的高低温冲击试验箱的温度转化时间(10 s)相除,得出各试验方案所对应的升降温速率,以便进一步分析温度冲击改性试验中升降温速率(温差)、高低温作用时间、循环次数对无烟煤甲烷吸附-解吸特性的影响规律,并从表面特性和孔隙结构方面研究其机理。研究结果表明:温度冲击改性样与无烟煤原样相比,在不同水平的升降温速率、作用时间和循环次数作用下,无烟煤对甲烷的最大吸附量均减小,Langmuir压力均增大,最大解吸量和扩散系数均增大,且影响效果的顺序为:升降温速率>作用时间>循环次数。温度冲击改性样与无烟煤原样相比,在表面特性方面,煤-水接触角减小,表面能增大,极性含氧官能团(—OH)数量增多,甲基(—CH3)和亚甲基(—CH2)数量减小;在孔隙结构方面,孔隙发育明显,微孔数量减少,平均孔径和孔容增大,比表面积减小。

     

    Abstract: Anthracite has the characteristics of strong methane adsorption and low desorption rate. In order to improve the extraction efficiency of coalbed methane in anthracite, temperature shock was selected as the modification method. An orthogonal experimental scheme with 4 factors and 4 levels was set up, and the temperature difference between high temperature and low temperature was divided by the temperature conversion time (10 s) of the temperature shock test chamber to obtain the temperature rise and fall rate corresponding to each experimental scheme. The effects of temperature rise and fall rate, action time and cycle times on the adsorption-desorption characteristics of anthracite methane in temperature shock modification were further analyzed, and its mechanism was studied from the aspects of surface characteristics and pore structure.The results show that compared with the original anthracite, the maximum adsorption capacity of anthracite for methane decreases, the Langmuir pressure increases, the maximum desorption capacity and diffusion coefficient increase, and the order of influence effect is: temperature rise and fall rate > action time > cycle times. Compared with the original anthracite, the thermal shock modified sample has a decrease in the coal-water contact angle, an increase in the surface energy, the number of polar oxygen-containing functional groups (—OH) increased, and the number of methyls (—CH3) and methylene (—CH2) decreased; In terms of pore structure, the spores develop obviously, the number of micropores decreases, the average pore size and pore volume increase, and the specific surface area decreases.

     

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