屯留矿煤分子孔隙重构及其表征与分析

为定性和定量研究煤的分子孔隙分布情况,选取屯留矿区煤样为研究对象,通过元素分析、固体^(13)C核磁共振和X射线光电子能谱等实验测试并分析了屯留矿煤样的化学结构,构建了煤分子模型。利用分子模拟技术,重构了煤样的分子孔隙。采用最大球算法原理,对分子孔隙模型进行孔隙识别,基于提取的孔隙网络模型对孔隙结构参数进行简化计算,实现了对煤分子孔隙结构的三维可视化表征和定量分析。利用CO_(2)吸附法测试了煤样的孔径分布、比表面积和孔容等孔隙结构参数,与模型对应的孔隙分布特征进行了对比。结果表明,屯留煤样孔径小于1 nm的分子孔隙孔径分布曲线呈现双峰特征,第1峰范围内孔隙的孔径小于0.7 nm,属于极微孔,第2峰范围内孔隙的孔径大于0.7 nm,属于超微孔;孔径在0.40~0.65和0.70~0.89 nm的孔隙数量较多,比表面积和孔容较大;孔隙平均配位数为2.32,大多数孔隙由2个及以上的喉道连通,说明孔隙连通性较好;孔喉半径比主要在1.00~2.00,极少在4.50~7.50,说明煤样孔径小于1 nm的分子孔隙空间发育比较均匀,但在孔隙空间的局部区域存在较大尺寸变化;模型的孔隙分布特征与CO_(2)吸附法测试结果相比,孔径分布曲线趋势相似,数值相近,说明利用煤分子重构煤的分子孔隙并进行孔隙结构的表征与分析是可行的。

大孔隙高分子聚合物混合料路用性能研究

针对普通OGFC沥青混合料环保性差、服役寿命短的问题,尝试采用高分子聚合物胶粘剂代替沥青来制备大孔隙高分子聚合物混合料,并对两种混合料路用性能进行了对比,结果表明:大孔隙高分子聚合物混合料高低温性能优异;抗滑性能略低于OGFC沥青混合料;对于大孔隙高分子聚合物混合料水稳定性,以浸水残留稳定度评价时,水稳定性较差,而以浸水飞散损失作为水稳定性评价指标不符合实际情况。

Solubilization of small molecules from coal and the resulting effects on the pore structure distribution

The solubilization of small molecules from coal by solvent extraction and the resulting effects on the pore distribution of a low rank coal were studied. Samples were extracted, in succession, with petroleum ether and with CS2. Extract and residue fractions collected during the solubilization process were analyzed by FTIR and by surface area and porosimetry. The results show that an obvious inflection point exists that allows separating the dissolution sequence into stages. Small molecules are first extracted from the free state, then molecules trapped in micropores are extracted and, finally, molecules trapped in the coal-matrix network are extracted. This is indicated from the extraction yield curves. Chain-like carbonyl compounds, -OH (or -NH) containing compounds that are hydrogen bonded and phenolics dominate the petroleum ether extracts. Chain-like carbonyl components and ether compounds (aliphatic ethers and aromatic ethers) dominate the CS2 extracts. A solvent dissolution mechanism and the effect of small molecule extraction on the pore structure are put forward. Diffusion, dissolution, pore opening, pore shrinking or even collapsing caused by swelling, creating of new micropores, pore opening and, finally, colloidallization of some micropores occurs. In the later stages of the extraction the internal structure of the coal is colloidallized due to swelling and the pore number or volume is greatly reduced.

Modification of pore size in activated carbon by benzene deposition and its effects on CH4/N2 separation

Anthracite coal was used as raw material to prepare activated carbons as the carbon support in the carbonization-activation process. Modification of the pore size of the activated carbon by chemical vapor deposition of carbon from benzene was examined. These samples were characterized by adsorption of N2 at 77 K and CH4 and N2 at 303 K. The microporosity of these samples was evaluated by the Dubinin-Astakhov Equation. The pore size distribution was obtained by the DFT method applied to the N2 adsorption data at 77 K. The separation selectivity was obtained by the Langmuir Equation. The surface morphology was characterized by an environmental scanning electron microscope. It was observed that all samples of carbon molecular sieves studied were microporous carbonaceous materials. CMS-2 prepared in the present study has a better N2/CH4 separation performance; it can satisfy the requirements of the pressure swing adsorption for concentrating CH4 from the N2/CH4 mixture gas.

Formation of Polyethersulfone Film with Regular Microporous Structure by Water Vapor Induced Phase Separation

Polyethersulfone(PES)film with regular microporous structure was formed using dichloromethane as the solvent via water vapor induced phase separation(VIPS).The effects of solution concentration,atmospheric humidity and temperature,as well as molecular weight of PES on the surface morphology of the polymer film were investigated.The surface morphology characterized by SEM showed that the pore size reduced as the solution concentration increased.There was an optimum range of relative humidity for the formation of regular pore structure, which was from 60%to 90%at concentration of 20 g·L-1 and 20°C.With the atmospheric temperature varied from 20 to 30°C,the pore became larger and the space between pores increased.The pore size in the PES film with low molecular weight was smaller than that with high molecular weight.

Lattice Boltzmann simulation of fluid flow through coal reservoir's fractal pore structure

The influences of fractal pore structure in coal reservoir on coalbed methane(CBM) migration were analyzed in detail by coupling theoretical models and numerical methods.Different types of fractals were generated based on the construction thought of the standard Menger Sponge to model the 3D nonlinear coal pore structures.Then a correlation model between the permeability of fractal porous medium and its pore-size-distribution characteristics was derived using the parallel and serial modes and verified by Lattice Boltzmann Method(LBM).Based on the coupled method,porosity(ф),fractal dimension of pore structure(Db),pore size range(rmin,rmax) and other parameters were systematically analyzed for their influences on the permeability(ф) of fractal porous medium.The results indicate that:① the channels connected by pores with the maximum size(rmax) dominate the permeability,approximating in the quadratic law;② the greater the ratio of r max and r min is,the higher is;③ the relationship between D b and follows a negative power law model,and breaks into two segments at the position where Db ≌2.5.Based on the results above,a predicting model of fractal porous medium permeability was proposed,formulated as k=cfrnmax,where C and n(approximately equal to 2) are constants and f is an expression only containing parameters of fractal pore structure.In addition,the equivalence of the new proposed model for porous medium and the Kozeny-Carman model k=Crn was verified at Db =2.0.