甲烷在成型前后活性炭上吸附的初步试验

Preliminary experiments of methane adsorption on unformed and formed activated carbons

通过对比试验,分析成型对活性炭储存甲烷特性的影响。首先,应用丙烯酸甲酯乳胶黏合剂对活性炭SAC-02成型,在温度区间268.15～338.15K、压力范围0～15MPa测试甲烷的吸附等温线;通过确定吸附量和等量吸附热,比较甲烷在成型前后活性炭上的吸附平衡。其次,测试储罐吸附床中心在室温、4个压力(6.5MPa、5.5MPa、4.5MPa和3.5MPa)下快速充放气过程的温度变化,分析成型对吸附过程热效应的影响。结果表明,成型活性炭的密度增大、比表面积减小、单位质量吸附剂上的甲烷吸附量减小;甲烷在成型前后活性炭上的等量吸附热均处于13～20.5kJ·mol-1;成型活性炭吸附床中心温度在充放气过程中的变化幅度和变化速率均增大。比较试验结果时发现,选用黏合剂成型须综合考虑其对吸附床热导率、传质阻力及吸附剂微观结构的影响。

Comparative experiments were carried out to analyze the impact of the formation of the activated carbon on the behavior of methane adsorption.Acrylate was selected as a binder and different ratios of activated carbon to binder were chosen to form the activated carbon SAC-02 prepared from coconut shell.Six adsorption isotherms of methane on formed and unformed activated carbons were respectively measured at equilibrium pressure-temperatures from 0 MPa to 15 MPa and 268.15 K to 338.15 K,adsorption isosteres were then plotted to determine the isosteric heat of adsorption.A storage vessel packed with formed and unformed activated carbons was employed to undertake quick charge and discharge tests at ambient temperature under four pressures(6.5 MPa,5.5 MPa,4.5 MPa and 3.5 MPa).The temperature at the central region of the storage vessel was recorded for evaluating the impact of the formation of the activated carbon on the behavior of methane in the dynamic storage process.Results show that formation of the activated carbon cut down the adsorption amount due to a smaller specific surface area of the formed activated carbon,however,the isosteric heats of adsorption on the formed and unformed activated carbons are all within the range of 13—20.5kJ·mol-1.Results also reveal that the formation of the adsorbent brings about a stronger fluctuation in the temperature in the initial state of quick charge and discharge processes.Conclusions are drawn that the heat conductivity of the binder and the transport resistance of the formed activated carbon should also be taken into account while forming the activated carbon.