| 不同含水性无烟煤CO2吸附行为及其对地质封存的启示 |
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| 引用本文： | 张金超,桑树勋,韩思杰,张凤碧,徐昂,刘琦珊.不同含水性无烟煤CO2吸附行为及其对地质封存的启示[J].煤田地质与勘探,2022,50(9):96-103. |
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| 作者姓名： | 张金超 桑树勋 韩思杰 张凤碧 徐昂 刘琦珊 |
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| 作者单位： | 1.中国矿业大学 资源与地球科学学院，江苏 徐州 221116 |
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| 基金项目： | 国家自然科学基金碳中和专项项目(42141012)；国家自然科学基金青年项目(42102207)；江苏省煤基温室气体减排与资源化利用重点实验室重大自主研究课题(2020ZDZZ01C) |
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| 摘 要： | 深部煤层CO2地质封存是助力“碳达峰碳中和”战略的重要途径，煤层含水性对以CO2吸附封存为主的深部煤层CO2地质封存能力影响显著。以无烟煤为例，开展了45℃下干燥、平衡水、饱和水煤样高压CO2等温吸附实验，校正了饱和水煤样过剩吸附曲线，利用改进的D-R吸附模型拟合得到三者吸附能力与吸附热，对比了不同含水条件下CO2绝对吸附曲线，阐释了饱和水增强无烟煤吸附能力的微观作用机理。结果表明:(1)干燥、平衡水、饱和水煤样CO2吸附能力分别为56.72、45.19和48.36 cm3/g，吸附热分别为29.42、26.23和27.24 kJ/mol。(2) CO2密度小于0.16 g/cm3(6.48 MPa)时，无烟煤CO2绝对吸附量大小顺序为干燥煤样、饱和水煤样和平衡水煤样，而CO2进入超临界状态后，顺序变为饱和水煤样、干燥煤样和平衡水煤样。(3)水分子优先占据高能吸附位是平衡水煤样吸附能力减弱的主要原因，而煤?水体系与CO2相互作用强于CO2与H2O竞争吸附下的煤?CO2相互作用是饱和水煤样在CO2超临界阶段吸附能力高于干燥煤样的根本原因。(4)吸附封存是煤层CO2地质封存的主要形式，深部煤储层条件下，煤层饱和水对超临界CO2增储作用更为明显，高压注水是提高深部煤层CO2地质封存潜力，改善煤储层渗透性的有效手段。
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| 关 键 词： | 饱和水 无烟煤 吸附能力 CO2地质封存 沁水盆地 |
| 收稿时间： | 2021-12-12 |
CO2 adsorption of anthracite with different moisture contents and its implications for geological storage |
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| Abstract: | CO2 geological storage in deep coal seams is regarded as an important pathway to achieve “2030 carbon peak and 2060 carbon neutrality goals”. The moisture content in coal seams plays a significant role in the CO2 storage capacity mainly based on CO2 adsorption. In this study, the anthracite from the Qinshui Basin was collected to conduct high-pressure CO2 adsorption isothermal experiments under dry, moisture-equilibrated and moisture-saturated conditions at 45℃. The CO2 excess adsorption curve was corrected by the reduction of CO2 dissolution. The adsorption capacity and adsorption heat were calculated using the modified D-R adsorption model. On the bases of the comparison of three CO2 absolute adsorption curves at different moisture conditions, the microscopic mechanism of moisture saturation enhancing the adsorption capacity was explained. The results show that (1) the CO2 adsorption capacity of dry, moisture-equilibrated and moisture-saturated coal samples are 56.72 cm3/g, 45.19 cm3/g and 48.36 cm3/g, and their adsorption heat are 29.42 kJ/mol, 26.23 kJ/mol and 27.24 kJ/mol, respectively. (2) With the CO2 density less than 0.16 g/cm3 (6.48 MPa), the absolute adsorption capacity of anthracite in descending order is dry coal, moisture-saturated coal, and moisture-equilibrated coal, but when the CO2 is in a supercritical state, the order changes to dry coal, moisture-equilibrated coal, and moisture-saturated coal. (3) The preferential occupation of high-energy adsorption sites by water molecules is the main reason for the reduction of the CO2 adsorption capacity of moisture-equilibrated coal samples. The interaction between the coal-H2O system and CO2 is stronger than that between coal and CO2 under the competitive adsorption of CO2 and H2O, resulting in the higher adsorption capacity of moisture-saturated coal samples being higher than that of dry coal samples in the supercritical stage of CO2. (4) Adsorption storage is the main form of CO2 geological storage in coal. In deep coal reservoirs, moisture saturation plays a more obvious role in increasing the adsorption capacity of supercritical CO2. High-pressure water injection into deep coal seams is an effective way to improve CO2 storage capacity and the permeability of coal seams. |
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