Mercury porosimetry and its application to the analysis of coal pore structure

Mercury porosimetry, gas adsorption, helium and mercury densities and small angle X-ray scattering were the methods used for studying porosity characteristics of a number of Czechoslovak coals ranging from lignite to semi-anthracite. Total pore volumes were measured in the pore radii range 0.1 – 7500 nm and then divided into the following groups: micropores (smaller than 1.8 nm), mesopores (1.8 – 30 nm) and macropores (over 30 nm). Coal porosity values ranged from 1.3 up to 43%. With low and medium-rank coals (carbon content under 76%), porosity is mostly due to mesopores. Micropores and mesopores account for a substantial share of the porosity of bituminous coals (carbon content over 80.6%). The distribution of mesopores was determined for an identical pore radii interval on the basis of data obtained independently by means of mercury penetration, gas adsorption and small angle X-ray scattering. High-pressure mercury penetration is an effective method of obtaining the coal porosity spectrum within a broad interval of pore radii, provided that a correction is made for the coal compressibility when evaluating the measured data. The recommended value of the mercury—coal contact angle is 1352 for brown coal and 130° for bituminous coal.     

Hydrothermal dewatering of lower rank coals. 1. Effects of process conditions on the properties of dried product

The hydrothermal dewatering of a Loy Yang Low Ash Victorian brown coal has been studied under a wide range of process conditions. The intra-particle porosity (<1 μm pore radius) determined by mercury porosimetry of the resulting dried products, a proxy for the maximum solids concentration of coal-water slurries, is reported as a function of reaction time, processing temperature, autoclave size and configuration and slurry concentration. Of these variables only the process temperature had a significant influence on the product intra-particle porosity, which decreased with increasing temperature. Other product variables were affected by a wider range of process conditions; increase in temperature and residence time and decrease in slurry concentration led to marked increase in loss of organic material to waste water, and the elemental composition of the product changed significantly with e.g. residence time. Drying of coal samples of particle sizes >50 μm gave products of constant intra-particle porosity but smaller coal particles gave products with higher intra-particle porosities as a result of agglomeration. Milling of the coal reduced the porosity of the dried coal at constant particle size.     

黔西滇东上二叠统煤孔隙发育特征及煤级对孔隙的影响

在对黔西滇东地区34个上二叠统龙潭组煤样进行压汞测试分析及扫描电镜观察的基础上,从孔隙度、各孔径段孔隙分布、各孔径段孔隙对孔隙度的贡献以及煤级对孔隙发育的影响4个方面对煤孔隙特征进行系统分析。研究表明：研究区煤孔隙度具有北低南高、东低西高的特征;煤孔隙以小微孔为主,大孔和中孔发育程度相当;随着孔隙度的增加。各孔径段孔隙贡献率的增加速率存在差异,以大孔贡献率的增加最为明显;孔隙度随煤级的增加呈“M”型波状变化．趋势变化的3个拐点分别对应尺．值的0．8％．1．4％．2．6％。     

利用气煤和焦粉制备优质铸造焦的研究

针对中国主焦煤资源短缺而气煤储量相对丰富的资源特点，采用气煤为主焦化煤种，配用焦粉做瘦化剂，并添加一定量的沥青作粘结剂，通过系列配煤方案制备铸造型焦，获得可制备一级铸造焦的优化配煤方案为45：50：5。实验结果表明，随着气煤和沥青配入量减少，焦炭的M40提高，气孔率Ps降低，焦炭显微结构越趋向于致密化。在实验配比条件下，沥青添加量降低对于焦炭强度提高的影响较气煤显著；而气煤配比减少对于焦炭气孔率降低的影响较沥青显著。     

The char structure characterization from the coal reflectogram

Coal is a heterogeneous substance and its heterogeneity is identified and characterized by variation in reflectance. The main objective of this paper is to characterize the heterogeneity of char and to correlate it with the coal reflectogram, which accounts for both rank and maceral composition effects. Chars from two density fractions in a set of coals were obtained in a Drop Tube Furnace (DTF) at 1400 °C in N₂ environment. The chars were examined under a Scanning Electron Microscope (SEM) and the morphology information was obtained from the image-processing technique. The average porosity of char changes systematically with the FMR of its parent coals (defined as the summation of each reflectance multiplied with its frequency). The char porosity increased with an increase in FMR up to a critical value around 98. With further increase in FMR, the corresponding char becomes dense. The char macro porosity distribution was found to be related to the coal reflectogram. In general, the char porosity distribution shows two peaks, which corresponds to the inertinite and vitrinite peaks in reflectogram. The intensity depends on the maceral content. The relationship between the char porosity and coal reflectance for this set of sample has been found, which is strongly dependent on the coal rank. However, these findings cannot be applied to coals with a strong maceral association (microlithotype).     

煤炭流化床燃烧与热天平燃烧动力学关系研究

通过对不同煤种在热天平中的单颗粒燃烧过程的分析发现:煤种、颗粒大小、氧气浓度对颗粒燃烧完全所需要的时间影响特别显著;而在一般流化床生产运行温度范围内,温度对颗粒燃烧完全所需要时间的影响有限;同一煤种不同颗粒煤焦孔隙率的影响很小.通过对单颗粒热天平燃烧实验,考查不同煤种及颗粒大小等各因素对颗粒燃烧过程的影响,可方便地指导流化床的设计以及生产运行过程中工艺的调整.     

焦炭气孔率对焦炭热性能的影响

通过研究40kg试验焦炉单种煤焦炭、配合煤焦炭及工业焦炉焦炭的气孔结构及焦炭热性能,得出气孔率对焦炭热性能的影响。焦炭气孔率对焦炭热性能有较大影响,随着气孔率的增加,CRI增加,CSR降低;工业焦炉焦炭气孔率与焦炭热强度之间关系密切,气孔率每增加1％,CRI增加0．48％,CSR降低1．46％。用气孔率预测焦炭热性能,对指导焦炭生产、控制焦炭热性能具有指导意义。     

Influence of the piece size of poorly clinkering coal on coke porosity

The influence of heat treatment (750 and 1000°C) of nonclinkering and poorly clinkering D, G, SS, and T coal on the pore structure and properties of coke is studied. The porosity of coke from coal pieces and crushed coal is significantly different.     

Maceral and rank influences on the morphology of coal char

Concentrates of vitrinite and inertinite macerals have been pyrolysed in a flame under conditions representative of the initial stages of pulverized coal combustion. Char was distinguished from soot by size analysis and the char yield correlated with the proximate analysis. The char morphology was studied by optical microscopy and quantitative measurements of porosity and pore size were made using image analysis. Vitrinite and inertinite produce chars of characteristic morphology. The softening behaviour of inertinite varies with coal rank and can be related to the optical reflectance. The porosity of vitrinite chars approaches that of inertinite chars at high rank.     

Modeling changes of fractal pore structures in coal pyrolysis

Coal pyrolysis processes are numerically investigated in mathematically produced coal pore models which simulate real coal pores in the parameters of the porosity and fractal dimension. The simulations include FG-DVC chemical reaction model, gas molecular diffusion in pores, energy conservation model and coal swelling model. Numerical results are verified by experimental results qualitatively, and they revealed that both the porosity and volatile contents of the parent coal can affect the fractal dimension of the final char pores after pyrolysis linearly. A formula to predict the fractal dimension of char pores from its parent coal properties is obtained by curve fitting in numerous results.     

用无形孔模型研究影响煤粉燃烧的因素

用一种新的孔隙结构模型──无形孔模型来研究影响煤粉燃烧的因素。对该模型进行数值计算，跟踪燃尽过程中温度、氧浓度、燃烧速率等随时间的变化，得到有关曲线。定量探讨整个煤粒内部的燃烧过程。研究挥发分析出和燃烧对煤粉燃烧过程的影响。研究孔隙率、比表面积、粒径等因素对煤粉着火、燃尽的影响。结果表明孔隙率对燃尽的影响较大，而比表面对着火的影响较大。     

Atomic force microscopy studies of Bowen Basin coal macerals

The porous structure of Bowen Basin coal macerals is very important in the storage and transport of coal seam gases. As part of a full characterization of this porosity, several coal macerals were examined by atomic force microscopy. Mesopores of ≥ 8 nm deriving from different types of porosity were imaged. The pores were either formed by contact points between spherical clusters of molecules or were defined channels that had been created by some physical process. The potential of this technique for characterizing the porous structure in greater depth was demonstrated.     

煤的孔隙结构与反应性关系的研究进展

煤在气化、燃烧与活性炭制备等热化学转化过程中，均存在着孔隙结构与表面积的变化．煤的孔隙结构变化特征的研究是煤炭高效合理利用的基础．从煤的孔隙结构的表征、反应过程中孔隙结构变化以及孔隙结构模型三方面总结了煤的孔隙结构与反应性关系领域的研究现状，并对今后的研究重点进行了展望，即加强孔隙结构与反应性关系通用规律和催化剂对孔隙结构影响两方面的研究．     

型煤的甲烷吸附以及NMR实验研究

原煤吸附甲烷其吸附量不高,而且孔隙不均匀,但是型煤不但吸附量大大增加,而且孔隙均匀,孔隙度也可以随意控制(一定范围内)。利用三轴渗透仪等装置对型煤的吸附解吸进行了实验,通过改变轴压、围压、孔隙压观测其对甲烷吸附量的影响。然后利用RecCore系列全直径核磁共振仪进行回波串及其T_2谱的测量研究。     

沁水盆地重点区块煤储层吸附特征及影响因素

煤储层吸附特征参数是评价煤层气资源和开发潜力的重要参数,煤储层的吸附能力是影响煤层气含量的关键因素之一,也直接影响煤层气井的产能,因此研究煤储层的吸附特征、分析煤储层吸附能力的影响因素对于煤层气的开发具有重要意义。根据等温吸附试验结果,对沁水盆地某区块煤储层的吸附特征进行研究,并探讨煤储层吸附能力的影响因素。结果表明:该区块含气量高,具有较强的吸附能力。煤阶、孔隙率、灰分和煤体结构对煤储层吸附能力有较大影响;孔隙率越大、煤体结构越完整,煤储层吸附能力越强;灰分的增加会降低煤的吸附能力;随煤阶的增加,煤储层吸附能力先增加后减小。     

On the action of pyridine as a swelling agent of low-rank coals

The swelling by pyridine/benzene mixtures of low-rank coal briquette fragments is investigated, and the results are very close to those previously reported for pyridine/benzene mixtures acting on a run-of-mine coal from the same source. This is in spite of major differences in porosity between the two coals. The conclusion is that pore entry by the solvent plays no part in the swelling process.     

添加剂对铸造焦性能的影响

以山西柳林和沁源煤为主配料,选用５种炭质添加剂进行子多个配料方案的炼焦试验,通过焦炭光学组织的定量分析和气孔结构的研究,解释了不同添加剂配入量对铸型造焦性能的影响。     

Coal from Kazakhstan for the direct reduction of iron

The characteristics of lignite and long-flame coal from Kazakhstan are studied: its overall composition, the composition of its organic and mineral components, its petrographic composition, and its physicochemical properties (density, porosity, reactivity, structural strength, and thermal stability). The use of such coal for the direct reduction of iron is recommended.     

煤层气开采过程中裂缝系统与渗透率演化关系

煤中会自然形成裂隙,从人类认识到其存在,其历史到至今已经有一百多年了。开发煤层气的实践已经表明了：煤岩的裂缝与渗透率是制约我国煤层气资源开发的关健因素。裂缝性质对煤层气的产出有着很大的影响。煤层是属于裂缝性的储层,它的煤层的渗透率以及其的排液能力,被其裂缝的孔隙度、开度、及间距等所控制着。     

Mechanism of swelling and extraction and coal structure

An attempt is made to develop a comprehensive model of coal structure based on results of various experiments involving extraction and swelling of a coal by solvents. These are described in terms of electron-donor and electron-acceptor characteristics, of mass spectrometric analysis of coal extracts, of pulse ¹H n.m.r. measurements of mobilities of coal components, porosity measurements. The theory of coal swelling cannot be adapted from the theory of polymer swelling.