Application of temperature-pressure-adsorption equation in calculating the adsorption enthalpy of coal seam

doi:10.16085/j.issn.1000-6613.2019-0454

Abstract

Abstract: A series of isothermal adsorption experimental data of long flame coal, fat coal, lean coal and meager coal in Ordos Basin are used to verify a temperature-pressure-adsorption equation, and the functional relationship between adsorption equilibrium pressure and temperature was discussed. The enthalpy of the gas adsorption process is calculated by the Clausis-Clapperon equation. The concept and calculation method of unit isosteric adsorption enthalpy is presented. The adsorption process of the coal is an exothermic process because its negative enthalpy. The unit isosteric adsorption enthalpy decreases with the increase of adsorption capacity because of the energy inhomogeneity on the coal surface. Because of the exothermic adsorption process, so the adsorption occurs at a higher energy site first in order to release more energy. The higher rank coal has a larger unit isosteric adsorption enthalpy, and there must be a larger adsorption capacity. The adsorption capacity of high rank coal decreases rapidly with the increase of adsorption temperature, but the low rank coal decreases less.

Key words: Clausius-Clapeyron equation, temperature-pressure-adsorption equation, isosteric enthalpy of adsorption, unit isosteric enthalpy of adsorption, gas adsorption, coal rank

摘要： 用鄂尔多斯盆地的长焰煤、肥煤、瘦煤和贫煤4个煤样的系列等温吸附实验数据来验证一个温度-压力-吸附方程，并探讨等量吸附时吸附平衡压力与温度之间的函数关系。用克劳修斯-克拉佩龙方程求等量吸附焓。提出单位等量吸附焓的概念及计算方法。结果表明：煤样等量吸附焓为负值，证实吸附过程是个放热过程；对于同一煤样，单位等量吸附焓随吸附量的增加而下降是由于吸附介质表面的能量不均匀性所造成。正因为吸附过程是个放热过程，所以吸附先发生在能量较高的位置上，以便放出更多能量；在相等吸附温度和压力条件下，高阶煤有较大的单位等量吸附焓，必有较大的吸附量。同时高阶煤吸附量随着吸附温度的升高而快速衰减，而中低阶煤吸附量衰减却没有那么明显。

关键词: 克劳修斯-克拉佩龙方程, 温度-压力-吸附方程, 等量吸附焓, 单位等量吸附焓, 气体吸附, 煤级

CLC Number:

O647.3

LI Dong, ZHANG Xuemei, HAO Jingyuan, MA Qinghua. Application of temperature-pressure-adsorption equation in calculating the adsorption enthalpy of coal seam[J]. Chemical Industry and Engineering Progress, 2019, 38(s1): 104-109.

李东, 张学梅, 郝静远, 马青华. 温度-压力-吸附方程在计算煤岩等量吸附焓的应用[J]. 化工进展, 2019, 38(s1): 104-109.

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