On the effects of petrographic composition on coalbed methane sorption

The effect of petrographic composition on the methane sorption capacity has been determined for a suite of coals and organic-rich shales. Subbituminous and bituminous coals were separated into bright and dull lithotypes by hand-picking. The methane sorption capacities range between 0.5 and 23.9 cm³/g at a pressure of 6 MPa. The low volatile bituminous Canmore coal and the anthracite sample have the highest capacities with the “natural coke” having the lowest. For low-rank coals there is no significant difference between bright and dull samples except for one coal with the dull sample having a greater sorption capacity than its bright equivalent. For higher-rank coals, the bright samples have a greater methane capacity than the dull samples and the difference between sample pairs increases with rank. The boghead coal samples have the highest sorption capacities in the liptinite-rich coals suite and are higher than subbituminous to medium volatile bituminous samples. Pore size distribution indicates that methane is held as solution gas in liptinite-rich coals and by physical sorption in micropores in liptinite-poor coals. These contrasting processes illustrate that liptinite-rich samples need to be independently assessed. The positive relationship between reactive inertinite content and methane sorption capacity occurs within the subbituminous to medium volatile bituminous coals because the reactive inertinite is structurally similar to vitrinite and have a higher microporosity than non-reactive inertinite. Reactivity of inertinite should be assessed in CBM studies of dull coals to provide a better understanding of petrographic composition effects on methane capacity.     

Comparison of source rock geochemistry of selected rocks from the Schei Point group and Ringnes formation, Sverdrup basin, arctic Canada

Organic-rich from the Schei Point group (middle to late Triassic in age) and the Ringnes formation (late Jurassic) from the Sverdrup basin of the Canadian arctic archipelago have been geochemically evaluated for source rock characterization. Most samples from the Schei Point group are organic-rich (> 2% TOC and are considered as immature to mature oil-prone source rocks [kerogen types I, I–II (IIA) and II (IIA)]. These kerogen types contain abundant AOM1, AOM2 and alginite (Tasmanales, Nostocopsis, Leiosphaeridia, acritarch and dinoflagellate) with variable amounts of vitrinite, inertinite and exinite. Samples from the Ringnes formation contain dominant vitrinite and inertinite with partially oxidized AOM2, alginite and exinite forming mostly immature to mature condensate- and gas-prone source rocks [kerogen type II–III (IIB), III and a few II (IIA)]. Schei Point samples contain higher bitumen extract, saturate hydrocarbons and saturate/ aromatic ratio than the Ringnes samples. Triterpane and sterane (dominant C₃₀) distribution patterns and stable carbon isotope of bitumen and kerogen suggest that the analyzed samples from the Schei Point group are at the onset of oil generation and contain a mixture of sapropelic (algal) and minor terrestrial humic organic matter. Sterane carbon number distributions in the Ringnes formation also suggest a mixed algal and terrestrial organic matter type. There are some variations in hopane carbon number distributions, but these are apparently a function of thermal maturity rather than significant genetic differences among samples. Pyrolysis-gas chromatography/mass spectrometry of the two samples with similar maturity shows that the Schei Point sample generates three times more pyrolyzate than the Ringnes sample. Both samples have a dominant aliphatic character, although the Ringnes sample contains phenol and an aromaticity that is higher than that of the Schei Point sample.     

Statistical analysis of vitrinite reflectance data—a new approach

The reflectance of vitrinite (collotelinite) particles is a widely used parameter as a geothermometer for the estimation of the thermal maturity of organic matter enclosed in rocks. However, several problems have occurred during the last decades, which can be traced back to basically three causes: human mistakes, technical problems, and problems associated with the structural and compositional inhomogeneity of organic matter. Whilst in most cases the first two types of uncertainties can be handled by standardization, the third can cause significant problems during interpretation due to its generally inestimable character. The suppression of vitrinite reflectance and statistical problems originated from small sample size, and outliers belong to this latter type.International standards, such as the ASTM and the ISO, define the vitrinite reflectance parameter as a statistical average of measured data, disregarding the fact that the average is an unresisting and unrobust statistical parameter. In other words, the average is very sensitive to outliers and distribution.The aim of this research was to find and test a better, more resistant, and robust statistical parameter used by traditional parametric and nonparametric statistics, which can be applied in practice instead of the average. Three categories of statistical problems were studied on coal and disperse organic matter (DOM) samples: the distribution of measured values, the effect of data number, and the effect of outliers on statistical parameters. The statistical experiments carried out on numerous original and generated sample sets show that the median (med) and the most frequent value (Mn), a special weighted average, are better parameters to estimate the thermal maturity of organic matter especially above 1% reflectance value.     

陕北侏罗纪煤田榆神矿区中鸡勘查区煤层厚度混合分布特征及其意义

煤层厚度统计分布及空间变化规律研究对煤矿勘探和生产建设具有重要作用.以陕北侏罗纪煤田榆神矿区中鸡勘查区详查工作中获取的83个钻孔数据为例,对三大主要可采煤层2-2煤、3-1煤、4-3煤的煤厚数据进行了探索性数据分析,认为3个层煤的煤厚数据均具有混合分布特征,进而采用MML-EM算法对煤层厚度数据进行了高斯有限混合总体筛分.由总体筛分结果可见2-2煤、3-1煤的煤厚数据近似服从由2个子分布组成的混合正态分布,4-3煤厚数据近似服从由3个子分布组成的混合正态分布.讨论了煤层底板高程与煤厚的相关关系,认为煤厚变化主要受底板高程变化影响.筛分所获取的低值与高值2个子正态分布可能分别对应于2种不同的沉积环境,即低值总体指示泥沙及砾石等沉积物的沉积速度大于植物遗体的沉积环境,高值总体则反之.     

On the identification and origin of pseudovitrinite

Representative subsamples of Pocahontas No. 3 coal obtained at a fresh mining cut in a coal mine in West Virginia, U.S.A., were oxidized in air at 50°C or stored at ambient temperature in argon. Periodically, subsamples were removed from their locations and analyzed both petrographically and through Gieseler plastometry.With increasing oxidation, as indicated by plastometer results, the percentage of vitrinite decreased while the percentage of oxyvitrinite increased. Also, the percentage of slitted pseudovitrinite initially increased, but, subsequently decreased. The same trends occurred for both the 50°C and ambient samples, although at a lower rate for the ambient samples. This has been interpreted as indicating that slitted pseudovitrinite is an oxidation product of vitrinite that is intermediate, in terms of degree of oxidation, between vitrinite and oxyvitrinite.Vitrinite and slitted pseudovitrinite reflectances were found to be approximately the same, however, a shallow trend of decreasing reflectance with degree of oxidation may be indicated. No explanation is submitted for an observed decrease (with oxidation) in percentage of micrinite; however, an explanation of the origin of slitted structures in vitrinite material as it relates to cell structure and geological conditions is offered.     

Application of SAXS and SANS in evaluation of porosity, pore size distribution and surface area of coal

This paper discusses the applicability of small angle X-ray scattering (SAXS) and small angle neutron scattering (SANS) techniques for determining the porosity, pore size distribution and internal specific surface area in coals. The method is noninvasive, fast, inexpensive and does not require complex sample preparation. It uses coal grains of about 0.8 mm size mounted in standard pellets as used for petrographic studies.Assuming spherical pore geometry, the scattering data are converted into the pore size distribution in the size range 1 nm (10 Å) to 20 μm (200,000 Å) in diameter, accounting for both open and closed pores. FTIR as well as SAXS and SANS data for seven samples of oriented whole coals and corresponding pellets with vitrinite reflectance (R_o) values in the range 0.55% to 5.15% are presented and analyzed. Our results demonstrate that pellets adequately represent the average microstructure of coal samples.The scattering data have been used to calculate the maximum surface area available for methane adsorption. Total porosity as percentage of sample volume is calculated and compared with worldwide trends. By demonstrating the applicability of SAXS and SANS techniques to determine the porosity, pore size distribution and surface area in coals, we provide a new and efficient tool, which can be used for any type of coal sample, from a thin slice to a representative sample of a thick seam.     

煤岩显微组份和全煤热解色谱分析

随着石油勘探的深入和发展，煤和含煤沉积的生油问题，已经越来越引起人们的重视。为此，笔者选择了准噶尔盆地侏罗系富氢组份含量高的煤样和富镜质组的煤岩样品，采用快速热解法，对其显微组份和全煤的热解生烃潜势进行了研究。结果表明:（１）Ｒ_０值为０.３７～０.３９％的未成熟煤岩样品中，壳质组和镜质组在３５０～４５０℃温度区间有最大热解峰面积Ｓ_２。（２）富氢组份含量高的样品中，热解产物以正构烷烃＋正构烯烃为主，其次为芳烃化合物。（３）镜质组或富镜质组的煤岩样品中，Ａ１６００/Ｍｇ值较高时，热解产物在Ｃ_６-Ｃ_１５范围内，某些芳烃化合物成为主峰。（４）惰性组生烃能力最差，在较高温度下，形成含量很低的正构烷烃和烯烃，或在气态烃范畴产生少量烃类，或基本不产生热解产物。（５）随着加热时间的延长或原煤样品演化程度的升高，烯烃含量减少或消失，可能是干酪根转化过程中的残余氢为烯烃的氢化作用提供了氢源，使烯烃转化为烷烃的缘故。     

基于Bootstrap方法的岩土体参数联合分布模型识别

小样本容量岩土体参数最优联合概率分布模型的识别是一个富有挑战性的问题。基于Bootstrap提出了小样本容量岩土体参数最优边缘分布函数和最优Copula函数识别方法。简要介绍了岩土体参数联合概率分布函数构造的Copula方法,采用AIC准则识别最优的边缘分布函数和Copula函数。将识别结果表示为不同备选边缘分布函数和Copula函数为最优边缘分布和最优Copula的权重系数集合,以基桩荷载-位移双曲线参数试验数据为例证明了所提方法的有效性。结果表明：基于小样本容量岩土体参数试验数据估计的样本均值、标准差和相关系数具有较大的离散性,这种离散性进一步导致了统计量AIC值存在较大变异性。提出的基于Bootstrap的最优边缘分布函数和最优Copula函数识别方法不仅可以有效地考虑统计量AIC值的变异性,而且能够综合地反映不同备选边缘分布函数和Copula函数为最优边缘分布和最优Copula函数的概率,为小样本容量岩土体参数最优边缘分布函数和最优Copula函数的识别提供了一条有效的途径。     

The Late Triassic Callide Coal Measures, Queensland, Australia: Coal petrology and depositional environment

The Late Triassic (Carnian-Rhaetian) Callide Coal Measures are preserved in a partly fault-bounded basin remnant in east-central Queensland, Australia. The sequence comprises up to 150 m of interbedded clastic sedimentary rocks and at least four major coal seams, including one coal body up to 23 m thick. The sequence was deposited initially in high-gradient alluvial fan systems which gave way through time to sandy, low-sinuosity rivers. The restricted, intermontane and entirely alluvial nature of sediment accumulation is here considered to have influence the petrographic characteristics of Callide coals, and their external geometry.The main coal seam from the Callide Measures shows variation in the predominance of some macerals, indicating successions of environmental changes. The application of transmission electron microscopy (TEM) to the study of the Callide coal has enabled a better understanding of the nature and origin of some of the less understood macerals such as micrinite and vitrinite B. Two forms of vitrinite have been observed, each with a distinct reflectance range. The wood-sourced vitrinite A displays an average reflectance of 0.56%, implying a higher rank than the 0.49% Ro total vitrinite reflectance recorded in previous publications. Vitrinite B and A together represent the most commonly occurring macerals in the Callide coal samples of the present study. The lower-reflecting vitrinite B which forms bands, often several hundred μm in thickness, in TEM shows sub-micron electron transparent laminae of lipid-rich material alternating with a more conventional vitrinite material. The vitrinite B is interpreted to represent accumulations of leaves.The Callide coal has entered the oil window, and oil has been generated from some exinite, cutinite, and resinite, as evident from change in fluorescence and the presence of exsudatinite in cell cavities and cleats. Vitrinite B is seen under the microscope to also be generating oil. Micrinite, the origin of which has been much debated, occurs in selected horizons only, as lenticular bodies suggesting cell filling or filling of spaces between laminations in vitrinite B. TEM shows micrinite to consist predominantly of sub-micron pyrite and possibly other mineral particles adsorbed on humic acids.     

Biological marker compounds as indicators of the depositions! history of the Maoming oil shale

The Eocene Maoming oil shale from Guangdong Province occurs as a laterally uniform stratigraphic section, typically 20–25 m thick, from which the aliphatic hydrocarbon constituents of six representative samples were investigated using GC and C-GC-MS. The sediments evaluated included the basal lignite, a vitrinite lens from the overlying claystone, and four intervals from the massive oil shale bed. As expected, the lignite and vitrinite differ markedly from the oil shales. The lignite is dominated by bacterial hopanoids and components of higher plant origin, including C₂₉ steroids and triterpenoids such as oleanenes. Visually, the oil shale samples show corroded and degraded phytoclasts, spores, wispy particles of fluorescent organic material attributable to dinoflagellates and, especially in the uppermost sample, colonial algal bodies. The distributions of biological markers in the oil shales show many features in common, notably a dominance of dinoflagellate-derived 4-methylsteroids, and a significant proportion of higher-plant derived n-alkanes with marked odd-over-even carbon number predominance. Overall, they exhibit several features that resemble characteristics of the Messel shale. The hydrocarbons of the lowest shale horizon suggest that there may have been a gradual transition between deposition of the original peat and the subsequent oil shales. The aliphatic hydrocarbons of the uppermost shale are dominated by a number of C₃₁ and C₃₃ botryococcane homologues and other unusual branched alkanes possibly derived from green algae. All of the samples are immature. Overall, molecular and microscopic examination of the stratigraphic succession of the Maoming oil shale suggests a shallow, lacustrine environment within which peats were deposited. This lake subsequently deepened to support abundant algal populations, especially dinoflagellates, culminating in a dominance of botryococcoid algae.     

豫北煤田焦作、鹤壁、安阳矿区二1煤层优势断裂构造地球化学特征

对豫北煤田焦作、鹤壁和安阳矿区二１煤层的对比样（构造煤和原生结构煤）进行了显微镜和扫描电镜下观察、镜质组反射率测试、Ｘ射线衍射分析和化学分析等。研究结果表明,构造煤因发生了断裂构造地球化学作用,其化学成分、元素成分和煤分子结构与原生结构煤明显不同：构造煤的挥发分含量（％）比原生结构煤一般要小０．５５～３．４８,平均要小１．５９;构造煤和原生结构煤相比,碳含量（％）平均增加了３．１,氢含量（％）平均     

Development of the first coal seam gas exploration program in Indonesia: Reservoir properties of the Muaraenim Formation, south Sumatra

The Late Miocene Muaraenim Formation in southern Sumatra contains thick coal sequences, mostly of low rank ranging from lignite to sub-bituminous, and it is believed that these thick low rank coals are the most prospective for the production of coal seam gas (CSG), otherwise known as coalbed methane (CBM), in Indonesia.As part of a major CSG exploration project, gas exploration drilling operations are being undertaken in Rambutan Gasfields in the Muaraenim Formation to characterize the CSG potential of the coals. The first stage of the project, which is described here, was designed to examine the gas reservoir properties with a focus on coal gas storage capacity and compositional properties. Some five CSG exploration boreholes were drilled in the Rambutan Gasfield, south of Palembang. The exploration boreholes were drilled to depths of ~ 1000 m into the Muaraenim Formation. Five major coal seams were intersected by these holes between the depths of 450 and 1000 m. The petrography of coal samples collected from these seams showed that they are vitrinite rich, with vitrinite contents of more than 75% (on a mineral and moisture free basis). Gas contents of up to 5.8 m³/t were measured for the coal samples. The gas desorbed from coal samples contain mainly methane (CH₄) ranging from 80 to 93% and carbon dioxide (CO₂) ranging from 6 to 19%. The composition of the gas released into the production borehole/well is, however, much richer in CH₄ with about 94 to 98% CH₄ and less than 5% CO₂.The initial results of drilling and reservoir characterization studies indicate suitable gas recovery parameters for three of the five coal seams with a total thickness of more than 30 m.     

A study of the kinetic parameters of individual macerals from Upper Permian coals in South China via open-system pyrolysis

A unique Upper Permian coal, Leping coal, is widely distributed in South China. The coal samples studied in the paper were collected from two mines in the Shuicheng coalfield of Guizhou Province, southwest China. The geochemical works including coal petrography, maceral content, Rock–Eval pyrolysis, and kinetic modelling of hydrocarbon-generating have been carried out on whole coal and individual macerals. The higher contents of volatile matter, elemental hydrogen, and tar yield, and the high hydrocarbon generation potential of the Leping coals are attributed to their high content of “barkinite”, a special liptinite maceral.The hydrocarbon generation potential of “barkinite” (S₂=287 mg/g, hydrogen index (HI)=491 mg/g TOC) is greater than that of vitrinite (S₂=180 mg/g, HI=249 mg/g TOC), and much higher than that of fusinite (S₂=24 mg/g, HI=35 mg/g TOC). At the same experimental conditions, “barkinite” has a higher threshold and a narrower “oil window” than those of vitrinite and fusinite, and consequently, can generate more hydrocarbons in higher coalification temperature and shorter geological duration. Data from the activation energy distributions indicate that “barkinite” has a more homogenous chemical structure than that of vitrinite and fusinite. The above-mentioned characteristics are extremely important for exploring hydrocarbon derived from the Leping coals in South China.     

Application of reflectance micro-Fourier transform infrared analysis to the study of coal macerals: an example from the late jurassic to early cretaceous coals of the Mist Mountain Formation, British Columbia, Canada

The applicability of the reflectance micro-Fourier Transform infra-red spectroscopy (FTIR) technique for analyzing the distribution of functional groups in coal macerals is discussed. High quality of spectra, comparable to those obtained using other FTIR techniques (KBr pellet and transmission micro-FTIR), indicate this technique can be applied to characterizing functional groups under most conditions. The ease of sample preparation, the potential to analyze large intact samples, and ability to characterize organic matter in areas as small as 20 μm are the main advantages of reflectance micro-FTIR. The quantitative aspects of reflectance micro-FTIR require further study.The exaples from the coal seams of the Mist Mountain Formation, British Columbia show that at high volatile bituminous rank, reflectance micro-FTIR provides valuable information on the character of aliphatic chains of vitrinite and liptinite macerals. Because the character of aliphatic chains influences bond disassociation energies, such information is useful from a hydrocarbon generation viewpoint. In medium volatile bituminous coal liptinite macerals are usually not detectable but this technique can be used to study the degree of oxidation and reactivity of vitrinite and semifusinite.     

煤的镜质组平均反射率绝对标准差(R_(o,sd))作为配煤参数的应用

由于煤的镜质组平均反射率不能精确反映镜质组中反射率的分布状况,因此在配煤炼焦研究中,利用镜质组平均反射率作配煤参数往往会有一定的偏差。通过对北京焦化厂原料煤的深入研究和实验,笔者提出一个新的煤岩配煤参数,即煤的镜质组平均反射率绝对标准差（Ro,sd）。该参数是一个将镜质组反射率分布图量化的参数,既可反映煤的变质程度,又能反映原料煤的镜质组反射率分布特征。经验证,利用该参数作为配煤参数能取得更佳炼焦效果。     

Diagenesis of vascular plant organic matter components during burial in lake sediments

Diagenetic changes are difficult to distinguish from variations in sources of organic matter to sediments. Organic geochemical comparisons of samples of wood, bark, and needles from a white spruce (Picea glauca) living today and one buried for 10,000 years in lake sediments have been used to identify the effects of diagenesis on vascular plant matter. Important biogeochemical changes are evident in the aged spruce components, even though the cellular structures of the samples are well preserved. Concentrations of total fatty acids dramatically diminish; unsaturated and shorter chainlength components are preferentially lost from the molecular distributions. Concentrations of total alcohols are similar in the modern and 10,000-year-old wood and bark but markedly lowered in the aged needles. Hydrocarbon concentrations and distributions show little diagenetic change in the 10,000-year-old plant materials. Cellulose components in the wood decrease relative to lignin components, although both types of materials remain in high concentration in comparison to other organic components. Aromatization of abietic acid proceeds more rapidly in buried spruce wood than in bark; retene is the dominant polyaromatic hydrocarbon in the aged wood. In contrast to the variety of changes evident in molecular compositions, neither ¹³C values nor C/N ratios differ significantly in the bulk organic matter of modern and aged spruce components.     

Characteristics of hydrocarbon generation from organic macerals in Jurassic coal measures, Xinjiang, China

The Jurassic coals of the Junggar and Turpan-Hami basins, Xinjiang, China, are characterized by abundant vitrinite. Microscopic analysis of Junggar coal samples indicates that they contain desmocollinite and hydrogen-rich vitrinite with a low reflectivity. The hydrocarbon-generating potential of various macerais follows the decreasing order of exinite > vitrinite > inertinite. However, desmocollinite is a principal maceral for hydrocarbon generation in this area because the content of vitrinite is higher than that of exinite. Data from simulating experiments and infrared spectra show that the hydrocarbon-generating process occurred primarily at the lower-mature stage in the Middle-Lower Jurassic coal measures. Generally, crude oil from the Qigu oilfield has a close similarity in hopanoid distribution to the vitrinite and exinite from the Jurassic strata with C₂₃-C₃₂ pentacyclic triterpanes and γ-lupane being present. The distribution of steranes is also similar. C₂₉-sitostane is dominant and Q₂₇ ergostane is subordinate. Only a trace amount of cholestane is present. All this suggests that the crude oil from the Qigu oilfield was derived from Jurassic coal measures.     

The detection of weathering in coal by petrographic,rheologic and chemical methods

This study examines petrographic, rheologic, proximate and ultimate analyses techniques, to investigate the effects of natural weathering on coal. The applicability of such tests to both the detection of weathering and to the prediction of the properties of a fresh coal, based upon analyses of a weathered sample, is discussed.Rheologic parameters and a petrographic staining technique showed the most sensitive response to weathering. The latter test is considered the most suitable of these for the detection of weathering, as it is independent of prior knowledge of the properties of the fresh coal and of the petrographic composition. A petrographic approach is also considered most suitable for estimation of fresh coal characteristics from weathered samples. Rank may be closely approximated and petrographic type determined microscopically, even on highly weathered samples, and these two parameters may be used to estimate properties such as volatile matter, calorific value and dilatation. Minor modification should be made to vitrinite reflectance measurements, according to the degree of weathering as revealed by selective staining.     

淮北矿区芦岭煤矿构造煤发育特征

淮北矿区芦岭煤矿主采煤层8煤为特厚煤层,厚度2．72-17．75m,平均厚度9．60m,煤层硬度系数厂为0．16-0．53,构造煤累计厚度约占全层厚度的65％-90％。剖面自上而下划分为碎裂煤、菱形包裹体煤、片状煤、鳞片煤和粉末状煤5种类型,构造类型煤相间分布。微观上网络状裂隙发育．密集的网络状裂隙交叉切割．显微组分破坏严重．煤层受构造作用影响越大,构造煤中的微孔所占比例也就越高。在平面上构造煤的发育可划分为东、中、西三部分,井田东部构造煤较发育,厚度占全层厚度的75％-80％;中部构造煤最发育,厚度占全层厚度的95％以上;井田西部构造煤所占比例相对较低,约占全层厚度的65％-70％。采区资料表明,在倾向上,随着煤层深度的增加,构造煤厚度占金层厚度比例呈上升趋势．-450--460m水平以下,构造煤层所占比例明显增高,约占95％以上。     

Partitioning of elements and macerals during preparation of Antaibao coal

Analyses of the macerals, ash, sulfur and 43 major and trace elements were performed on samples of feed coal, cleaned coal, middlings and slime collected from the Antaibao coal preparation plant, China, and also on samples from coal preparation experiments. This study is focused on the partitioning of elements and macerals during coal preparation and potential environment aspects of the elements.The conclusions are as follows: (1) in comparison with the feed coal, the cleaned coal has a higher vitrinite content and relatively lower inertinite and exinite contents, whereas the middlings and slime have lower vitrinite and exinite contents, and relatively higher inertinite contents. The vitrinite contents in the size-segregated cleaned coals were observed to show a slightly increasing tendency with increasing particle size, while the inertinite contents decreased. (2) Physical coal cleaning is not only effective for removal of ash and sulfur, but also in reducing the concentration of most elements. As, Cd, Co, Cs, Hg, Fe, K, Mg, Nb and Ni are observed to show a high degree of removal, while Br, Be, Cu, U, Mn, Zn and organic sulfur are enriched in the cleaned coal and show a lower degree of removal. The large-sized cleaned coal is cleaner than the smaller sized fractions. (3) The middlings, especially the slime, are enriched in S, Hg, Cr, V, Zn, etc., so that these fractions should not be directly used as fuel. In addition, the concentration of Pb and V in the process water exceeds the limit of relevant environmental water quality standard. Consequently, it is necessary to develop new processes to remove ash, sulfur and hazardous trace elements to the maximum extent. Further studies on deep processing of the middlings and slime and cleaning of the process water should also be performed.