天然气吸附存储(ANG)复合吸附剂研制

Development of composite adsorbents for adsorbed natural gas storage

以抑制ANG存储过程中的热效应为目的,展开制备具有较高导热率的复合吸附剂的研究。根据容积法原理,在263.15~313.15K、0~9MPa,选择比表面积为1916m^2/g的活性炭,测试甲烷在膨胀石墨/活性炭混合比率分别为0%、20%和33%的吸附剂试样上的吸附平衡数据,并通过Toth方程和DA方程对吸附数据的模型分析,确定甲烷在吸附剂试样上的等量吸附热。结果表明,随膨胀石墨添加比例增大,复合吸附剂的比表面积与孔容积减小,导热系数显著增大,甲烷在复合吸附剂上的吸附容量和等量吸附热减小;由等量吸附线标绘和引入DA方程计算确定的甲烷在吸附剂上的等量吸附热均处于15~18kJ/mol范围,但DA方程计算结果能体现等量吸附热随温度变化的特点。由活性炭、膨胀石墨复合制备ANG吸附剂需兼顾甲烷在其上的吸附容量、传热与传质性能。

Enhancements of heat conducfivities of composite adsorbents were conducted to weaken the thermal effects resulting from the dynamic process on an adsorbed natural gas （ANG storage system. A kind of activated carbon, which has a specific surface area about 1916m2/g, was used to synthesize the composite by mixing with the expanded graphite. Two mass ratios （20% and 33% of expanded graphite to activated carbon for the composites were selected. Heat conductivity of the composites was measured by C- Therm TCI. Isotherms of methane adsorption were volumetrically measured at temperature and pressure ranges about 263.15-313.15K and 0-9MPa, respectively. Analysis of the adsorption equilibrium was carried out by using Toth equation and DA equation in terms of prediction accuracy as well as the isosteric heat of adsorption. It shows that increasing the ratio of the expanded graphite enlarged the heat conductivity of the composite but brought about the decrease of the specific surface area and the porous volumes of composite adsorbents, which resulted in the decrease of the storage capacity and the isosteric heat of methane adsorption. The isosteric heats of methane adsorption determined by adsorption isosteres and calculated by DA equation on the tested samples are about 15-18kJ/mol, but those from DA equation have the characteristic of temperature dependent. Conclusions are drawn that optimization among the storage capacity, the heat conductivity and the transfer performance of the adsorbate of the composite should be carried out while developing storage medium for ANG.