Fractal characteristics of pore structure in residual coal with different degrees of fragmentation and its influence on CO₂ adsorption behavior
不同破碎程度遗煤孔隙结构分形特征及其对CO₂吸附行为的影响研究

摘要

以准东矿区采空区遗煤为研究对象，通过筛分制备四种粒径等级（2-2.8mm、1.25-2mm、0.3-1.25mm、0.15-0.3mm）以模拟不同破碎程度，采用Nova2000全自动气体吸附仪在303K条件下开展CO₂吸脱附实验，并结合BET模型与Frenkel-Halsey-Hill（FHH）分形模型对孔隙结构进行定量表征。结果表明，不同粒径样品均获得完整等温线，且随粒径减小吸附量整体呈增强趋势。BET拟合计算得到比表面积随破碎程度增强而单调增大，Z10-7、Z16-10、Z60-16、Z100-60的比表面积分别为23.25、24.81、26.93、27.77m²/g。FHH分形分析在所选相对压力区间内线性拟合良好（R²=0.9848-0.9917），分形维数随粒径减小由2.3498增至2.4214，表明破碎作用促使孔隙表面粗糙度与结构复杂性提高。综合分析认为，破碎过程通过扩大有效吸附表面并增强孔隙结构复杂性，对CO₂的吸附与滞留产生协同促进作用。研究结果可为采空区CO₂注入惰化参数优化以及遗煤吸附滞留效应评估提供结构依据。

Abstract

Using residual coal from the goaf of the Zhundong mining area as the research object, four particle size grades (2-2.8 mm, 1.25-2 mm, 0.3-1.25 mm, and 0.15-0.3 mm) were prepared by sieving to simulate different degrees of fragmentation. CO₂ adsorption-desorption experiments were carried out at 303 K using a Nova2000 fully automated gas adsorption analyzer. The pore structure was quantitatively characterized by combining the BET model and the Frenkel–Halsey–Hill (FHH) fractal model. The results showed that complete isotherms were obtained for samples of different particle sizes, and the adsorption capacity generally increased with decreasing particle size. BET fitting calculations showed that the specific surface area monotonically increased with increasing crushing degree, with specific surface areas of Z10-7, Z16-10, Z60-16, and Z100-60 being 23.25, 24.81, 26.93, and 27.77 m²/g, respectively. FHH fractal analysis showed good linearity within the selected relative pressure range (R² = 0.9848–0.9917), and the fractal dimension increased from 2.3498 to 2.4214 with decreasing particle size, indicating that crushing promotes increased pore surface roughness and structural complexity. Comprehensive analysis suggests that the crushing process synergistically promotes CO₂ adsorption and retention by expanding the effective adsorption surface and enhancing pore structural complexity. The research results can provide a structural basis for optimizing CO₂ injection inerting parameters in goaf areas and evaluating the adsorption and retention effects of residual coal.