Dependence of coal liquefaction behaviour on coal characteristics. 6. Product distributions from coals treated in a continuous-flow reactor

Further experimentation with coals in a continuous-flow reactor system at 440 and 455°C confirms the significance of the previous classification of a set of coals by cluster analysis. The greatest yields of distillable products tend to be given by coals of high sulphur content in the middle of the range of the high-volatile bituminous rank classes. Yet the lowest yields of preasphaltene (toluene-insoluble material) tend to be given by coals of high rank and medium sulphur content. The group of low sulphur, low-rank coals (mostly Rocky Mountain province), in a solvent different from that used for the other groups, showed poor conversion and poor distillate yield at the higher temperature. It is concluded that this coal/solvent combination is particularly prone to retrogressive reactions, including coking.     

Dependence of coal liquefaction behaviour on coal characteristics. 7. Structural differences between coals of different rank and the asphaltenes derived from them

Aslphaltenes are difficult to characterize by any procedure that involves chromatography. In an attempt to obtain useful information on unfractionated asphaltenes and their structural relations to their parent coals, asphaltenes from a set of eight coals of hvA rank and different coalification history have been studied by ¹ H n.m.r. In addition, structural features in the coals and their asphaltenes were compared by g.c.-m.s. analysis of the products of oxidation by pertrif luoroacetic acid. Protons α to a benzene ring are the most abundant in the asphaltenes, and their relative concentration changes little with the rank of the parent coal. Protons in the β-position are abundant, however, and may be associated with aliphatic junctions linking two or more aromatic ring systems. Whereas malonic and ethane-trioic acids are the major aliphatic di-and tri-acids from oxidation of the coals, succinic and propane-or butane-tricarboxylic acids are the corresponding products that dominate the distributions from the asphaltenes. These and other differences help to define the structural changes caused by liquefaction. In addition, the results indicate the nature of structural changes with increasing rank, which are manifest in the oxidation products from the asphaltenes as well as from the coals.     

Short contact-time liquefaction of subbituminous coal: Directions for improving coal conversion

This study was undertaken to find ways to solubilize subbituminous coal in high yield at short contact times. Short contact-time hydroliquefaction runs were carried out in a continuous unit using Belle Ayr subbituminous coal with a solvent rich in hydrogen-donor molecules derived from the Lummus ITSL process, and also with solvents lower in donor concentration derived from the SRC processes. Catalysis by pyrite, molybdenum and supported cobalt-molybdenum was also studied. It was found that pyrite and other hydrogenation catalysts enhanced solubilization and also increased production of distillate oil. Solvent quality seemed to have no effect on the solubilization of Belle Ayr coal. The availability of H₂S also appeared to have no effect. Provided that pyrite was present, reaction could be carried out at severities high enough to give insoluble organic matter yields equivalent to those obtained with bituminous coals (5–10 wt% daf coal). At equivalent levels of solubilization, however, hydrocarbon gas and distillate yields were invariably higher for the subbituminous coal. Implications for two-stage processing of Belle Ayr coal are discussed.     

煤质特性与煤直接液化关系分析

简要讨论了原料煤特性对煤直接液化的影响,在煤的组成和物理性质等与煤液化关系之间建立良好的对应关系并总结了适合直接液化用煤种的一些特性。     

胜利褐煤液化初期反应动力学研究

为研究胜利褐煤在初始阶段的煤液化反应动力学,在可快速升降温的微型高压釜中对胜利褐煤进行了加氢液化反应,得到了反应初期煤液化参数,并对胜利褐煤加氢液化反应初期的动力学行为进行分析。结果表明,虽然反应器升温速度较快,但到达反应温度时,仍有一定量的煤发生了转化,在反应温度440℃、反应时间为0时转化率达到28.12%;在较低温度下,胜利褐煤只发生了部分热解反应,反应后期几乎不再转化,在380℃、反应10 min后转化率已达28%,后续基本不变;随着反应温度的升高,反应转化率、油水产率、气产率等指标增大,反应前10 min增速较快,10~25 min时反应速率减缓,主要是沥青烯组分作为中间产物不断向油转化,速率较低。     

Dependence of coal liquefaction behaviour on coal characteristics. 1. Vitrinite-rich samples

The liquefaction behaviour of a number of vitrinite-rich coals has been determined in batch autoclaves at temperatures of 385–425 °C and pressures of about 8.6 MPa (85 atm) of hydrogen. In one set of experiments, impregnated ammonium molybdate was used as catalyst, with no added liquid as vehicle. In a second set, a proprietary catalyst was used and anthracene oil served as vehicle. Lignites, sub-bituminous, medium-volatile and low-volatile bituminous coals gave relatively poor conversions. However, a lignite sample that had been subjected to ion-exchange treatments gave high conversion, and the viscosity and structural parameters of the products varied with the nature of the treatment. In general the highest conversions were observed for coals in the high-volatile bituminous range, but within this broad range and for the comparatively small set of samples studied neither these data nor the structural characteristics of the products show any very evident correlation with rank parameters or with the geological history of the sample. Two geologically young bituminous coals from the Pacific Coal Province gave excellent conversions; both had very high mineral-matter contents, a fact that may be very relevant.     

Effects of coal cleaning on the short contact time liquefaction of Illinois No. 6 coal

This study was carried out to determine the effect of coal cleaning by oil agglomeration and sink-float methods on yields from short contact time liquefaction of Illinois No. 6 coal. The runs were made in a continuous unit using SRC-II distillates as process solvent. Measured yields included hydrogen (consumption), hydrocarbon gas, distillate oil, SRC (the pyridine-soluble portion of the residue) and insoluble organic matter, the pyridine-insoluble organic residue. The solubility of product SRC in hexane, toluene and pyridine was also determined. The principal finding was that coal cleaning by density methods reduced the yield of IOM obtained in subsequent liquefaction and this is attributed to the removal of inert components from the feed coal. In addition, cleaning which significantly reduced pyrite content of the feed coal also reduced the yield of distillate oil and tended to give a less soluble SRC during liquefaction. Deep cleaning by gravity methods gave the lowest IOM, but reduced pyrite content to the point where distillate oil was consumed rather than produced. Oil agglomeration reduced total ash to 50% of that in the run-of-mine coal, but left the pyrite level in the coal high. The relevance of these results to two-stage liquefaction is discussed.     

Interrelationship of chemical characterization and rheological behaviour of coal liquefaction bottoms

In the development of the Exxon Donor Solvent (EDS) process, bituminous and subbituminous coals have been processed in a one ton-per-day coal liquefaction pilot plant using the feed coal slurried with solvent and with or without bottoms recycle. The liquefaction bottoms from both once-through and bottoms recycle operation exhibit non-Newtonian viscometric behaviour. The recycled bottoms, however, are more viscosity/shear dependent, less viscosity/temperature dependent and more thermally stable than the once-through bottoms. Chemical characterization of these bottoms reveals that alkyl and phenoxy groups are important functional groups responsible for the viscometric behaviour of bottoms. The increase of bottoms viscosity is postulated to involve the elimination/condensation of methylene units are phenolic functional groups to form the crosslinkages of large aromatic clusters.     

Filtration in coal liquefaction: 1. Influence of coal type

Commercial solvent extraction systems for coal must be able to process coals with various properties. In this study the influence of coal type upon the extraction yield of coal and the filtration of extraction products has been investigated. All the coals used gave high extraction yields in hydrogenated solvent but resultant products exhibited considerable differences in rates of filtration. This variation in filtration rates is dependent upon particle size, concentration and composition of the residual solids. No simple relation was found to relate coal type with filtration rate.     

Experimental study of the ignition behaviour of an adiabatic SRC-II coal liquefaction reactor

Experimental data are presented which describe the thermal behaviour of a bench-scale adiabatic coal liquefaction reactor operating in an open loop. The reactor employed external feedback control for maintaining adiabaticity. Conditions for both ignition and quench have been found for coal liquefaction at SRC-II operating conditions where repeated ignition/quench behaviour was demonstrated. No stable steady states were found between 450 °C and 475 °C for SRC-II operation. Ignition occurred at a feed temperature of ≈415 °C. The low steady states occurred at conditions of essentially no heat generation; at a very low extent of reaction. Some unexpected evidence of a preheater effect on reactor ignition was observed; however, the effect of preheater temperature profiles on reactor performance was not systematically studied.     

Two-stage liquefaction of a subbituminous coal

The two-stage conversion of a subbituminous coal has been investigated using an autoclave reactor system. The overall performance of the reaction is found to be determined by the effectiveness of the first-stage operation and by the method of sequencing of the stages. The initial thermal products can undergo condensation reactions which render them unresponsive to subsequent catalytic conversion and which increase the light gas yield. This can occur during the first stage reaction, if there is limited capacity for free-radical stabilization, and upon storage and/or thermal cycling between stages. The latter effects are circumvented by operating the two stages in immediate sequence. Condensation is also reduced by increasing the solvent quality and the solvent:coal ratio. The presence of a catalyst during thermal decomposition of coal can greatly improve conversion and product stability even at short reaction time and can reduce constraints on solvent quality. The more feasible approaches to improving first-stage operation appear to be in controlling the solvent composition and in employing hydrogenation catalysts.     

Dependence of coal liquefaction behaviour on coal characteristics. 2. Role of petrographic composition

The techniques used were the same as those used in Part 1 (p 34). Comparison of the liquefaction behaviour of two lithotypes from a Kentucky bituminous coal indicated that in this process pseudovitrinite is a reactive maceral. The hydrogenation of sets of maceral concentrates obtained from a New Mexico sub-bituminous and a Kentucky bituminous coal showed fair correlations between conversion and the total concentration of the presumed reactive macerals (vitrinite, pseudovitrinite and sporinite). Similar concentrates from a Montana lignite showed no such correlation; the one sample that showed a high conversion was a high-density fraction that had a high mineral-matter content and in which nearly all the pyrite in the coal had accumulated. Two samples that have boghead and cannel characteristics gave quite different results on hydrogenation. Both were highly aliphatic in structure and had unusually high hydrogen contents and volatile matter. One, which contained appreciable proportions of sporinite, alginite and resinite, gave essentially no conversion to oil. The other, predominantly vitrinitic but containing alginite as the second most abundant maceral, gave an excellent yield of an oil of low viscosity and aromaticity. It was concluded that although rank, petrographic composition and perhaps geological history are important factors determining liquefaction behaviour, there are other characteristics of coals that may at times override these basic parameters, and the composition of the inorganic matter may be the most significant of these other characteristics.     

神华煤液化反应初期动力学研究

为研究神华煤反应初期动力学行为,在容积180 m L搅拌高压釜中,使用循环溶剂为供氢溶剂,利用"863"催化剂进行煤直接液化反应。采用传统的集总反应动力学模型,将原料煤分为快反应组分,慢反应组分和惰性组分3部分,并计算各级反应动力学活化能。结果表明:快反应煤向油、气和沥青烯组分(PAA)转化的总反应活化能为279.74 k J/mol,慢反应煤向PAA转化的活化能为57.80k J/mol。在开始的4 min内,煤的转化率及PAA的产率由于煤的热解而迅速增加;在后续4~15 min时,转化率增加缓慢,PAA产率基本稳定,并开始降低,表现出了典型的中间产物的特性。当煤的转化率超过55%时,在氢自由基的生成上,溶解氢将发挥重大作用。     

煤直接液化研究评述

比较了中国与国际基础研究水平的差距,对主要的新老工艺进行了分类和比较,发现成功的液化工艺都符合煤分子结构的特点。高温快速液化是一种基于煤分子结构特殊性的直接液化方案,在理论上提供了实现最高液化效率和最低液化成本的可能性,联产芳香族化合物和燃料油,开辟了一个新的研究方向。     

Hydrogen incorporation during coal liquefaction

Coal hydrogenation reactions have been investigated using a deuterium tracer method which makes it possible to determine which structural positions in the coal react with hydrogen gas or donor solvent during liquefaction. ²H₂ and/or tetralin-d₁₂ were reacted with a Pittsburgh Seam coal at 13.8 to 22.1 MPa and 360 to 425 °C for 0.25 to 1.0 h. Hydrogenation and exchange indices were formulated to indicate the relative contribution of each type of reaction to the total H incorporation. In the coal-deuterium gas system, deuterium incorporation in the solvent-separated products increases in the order oil < asphaltene < preasphaltene < residue. However, in the coal-tetralin-d₁₂-deuterium gas system, deuterium incorporation is similar in each of these four fractions. In both systems, ²H incorporation varies with structural position, with the α-aliphatic positions exhibiting the greatest extent of incorporation. The α-tetralyl radical appears to be an important intermediate in hydrogen transfer to and exchange with the coal. The results indicate that in the donor system the abstraction of hydrogen from the solvent by coal-derived radicals is involved in the rate-determining step of the formation of the soluble products. Evidence indicates that considerable direct interaction of the gas-phase hydrogen with the coal also occurs in the donor solvent system.     

煤液化残渣中硫的迁移和转化研究现状及展望

为了解煤液化残渣利用过程中,硫化物迁移和转化规律,介绍了煤液化残渣中硫的来源及分布,总结了煤液化残渣在加氢液化、气化制氢、热解、燃烧等过程中硫化物的迁移和转化过程及影响因素,并对煤液化残渣中硫的迁移和转化的研究前景进行展望。结果表明,无机硫逐渐向有机硫转化,H2S是转化过程中的重要介质;H_2S、CS_2、SO_2等气态硫化物是煤液化残渣利用过程中的主要气态副产物;部分硫化物转化为大分子有机硫进入二次产品,影响产品质量和使用效果。为了合理有效地利用煤液化残渣,需寻找残渣中无机硫转化为单质硫或大分子有机硫的新方法,循环利用气体硫化物,开发新型煤液化催化剂,减少单质硫助剂使用量。     

Dependence of coal liquefaction behaviour on coal characteristics. 4. Cluster analyses for characteristics of 104 coals

In an extension of earlier work, the conversion of 104 high volatile bituminous coals at 400 °C with tetralin has been determined in duplicate with the aid of a new reactor system. For the whole set of coals, volatile matter and vitrinite reflectance have the highest correlation coefficients with conversion (0.85 and ?0.84, respectively). However, tests showed that the sample set contained more than one population. Cluster analysis partitioned the set into three reasonably homogeneous populations. A factor representing sulphur content was the major contributor from a set of variables in separating the coals into groups, with smaller contributions from factors related to rank and petrographic composition. Each of the groups contained samples mostly from one geological province, but 11 coals of relatively high sulphur content from the Eastern province were clustered in a group that contained also 25 coals from the Interior province. The ranges of conversion are distinctly different for the three groups, and the three regression equations developed for correlating conversion each require a different set of coal properties. The possible general significance of the clustering of coals into groups as a novel basis for classification is discussed.     

Kinetics of thermal liquefaction of coal

A model is presented for the kinetic study of the thermal liquefaction of Belle Ayr subbituminous and Burning Star bituminous coals with anthracene oil, hydrogenated anthracene oil and hydrogenated phenanthrene. All experiments were performed in a continuous-feed, stirred tank reactor, at a temperature of 450 °C and a space time of approximately 5 to 55 min. A kinetic model which includes a reaction: coal + oil→more reactive coal, correlates the data reasonably well. This reaction explains the net consumption of anthracene oil during the initial stages of liquefaction. Such a reaction may account for a portion of the swelling of coal at low space times and the sizable increase of viscosity of reaction slurry during these initial stages of liquefaction. It is also observed that the yield of oil increases when solvents of increasing hydrogen donor capacity are used.     

煤直接液化技术进展

通过煤炭液化生产液体燃料油来满足我国日益增长的需求,是解决石油资源不足的有效手段之一。文中综述了国内外煤直接液化工艺及其催化剂的研究进展,并指出了当前煤直接液化技术发展的方向。     

Hydrogen/deuterium transfer in coal liquefaction

Reactions have been made with deuterium-labelled solvent (d₄- and d₁₂-tetralin) and both Powhatan bituminous (Pittsburgh Seam) coal and model compounds under coal liquefaction conditions to study hydrogen transfer mechanisms. Powhatan coal liquefies quickly. Hydrogen transfer from the solvent to the reaction products continues throughout the heating period (up to 60 min). Significant hydrogen/deuterium exchange occurs and this strongly affects the distribution of deuterium in the products and also affects the extent of conversion as measured by the amount of THF-insoluble material. Increased deuteration of the solvent leads to decreased conversion. This exchange is enhanced by heavy aromatic species and by the presence of mineral matter and unconverted coal solids.