Coal liquefaction direct

Except for Germany s experience with technologies that directly transferred coal into fuel oil during World War II, there has been little experience with, or economic analysis of, commercial direct coal liquefaction (direct coal to liquid [DCTL]) until the new DCTL plants currently being built in China. 

Direct-Liquefaction Processes Figure 27-8 presents a simph-fied process flow diagram of a typical direct coal liquefaction plant. Specific processes are described in the following paragraphs. 

Background Indirect coal liquefaction differs fundamentally from direct coal hquefaction in that the coal is first converted to a synthesis gas (a mixture of H9 and CO) which is then converted over a catalyst to the final product. Figure 27-9 presents a simplified process flow diagram for a typical indirect coal hquefaction process. The synthesis gas is produced in a gasifier (see a description of coal gasifiers earlier in this section), where the coal is partially combusted at high temperature and moderate pressure with a mixture of oxygen and steam. In addition to H9 and CO, the raw synthesis gas contains other constituents (such as CO9, H9S, NH3, N9, and CHJ, as well as particulates. 

TABLE 27-16 Estimated Costs of Direct Coal Liquefaction Plant... 

Costs based on plant processing 26,105 Mg/d (28,776 US ton/d) of Ilbnois No. 6 coal. Source Direct Coal Liquefaction Baseline Design and Systems Analysis, prepared by Bechtel and Amoco under DOE contract no. DE-AC22-90PC89857, March 1993. 

A large program of work on coal liquefaction at the U.S. Bureau of Mines station at Bruceton, Pa., under the direction of H. H. Storch, was stimulated by the pre-war and wartime developments in Germany (49,50,51,52,53). The very extensive studies showed that, with some modification of processing conditions, most U.S. coals could be converted to liquid fuels in acceptable yields... 

A question then arises as to whether the CSD recovery is being limited by the preasphaltene content produced from direct products of coal liquefaction or whether by low liquefaction severity a more thermally sensitive product is produced resulting in retrogressive reactions of liquefaction products to "post-asphaltenes." There is some indication that "virgin" preasphaltenes, primary products of coal dissolution, are more easily recovered via CSD as shown in Table VII however, "postasphaltenes" made from thermal regressive reactions are not. 

The dialin donor solvents were also used directly in coal liquefaction studies. Inasmuch as details of coal structure are unknown, the present theory can only be tested in a qualitative way, as follows. First, if the liquefaction of coal occurs under kinetic control with hydrogen-transfer from the donor solvent involved in the rate-determining step, then we should expect the dialin donors to be more effective than the control solvent T.et-ralin (and also Dfecalin). This is suggested by the theory because the dialins possess higher energy HOMOs than Tetralin and... 

Fundamental studies of coal liquefaction have shown that the structure of solvent molecules can determine the nature of liquid yields that result at any particular set of reaction conditions. One approach to understanding coal liquefaction chemistry is to use well-defined solvents or to study reactions of solvents with pure compounds which may represent bond-types that are likely present in coal [1,2]. It is postulated that one of the major routes in coal liquefaction is initiation by thermal activation to form free radicals which abstract hydrogen from any readily available source. The solvent may, therefore, function as a direct source of hydrogen (donor), indirect source of hydrogen (hydrogen-transfer agent), or may directly react with the coal (adduction). The actual role of solvent thus becomes a significant parameter. 

Stephens, H. P., and Chapman, R. N., The Kinetics of Catalytic Hydrogenation of Pyrene Implications for Direct Coal Liquefaction Processing. In Am. Chem. Soc. Div. Fuel Chem, 1983. Prepr. Pap. 28 pp. 161-168. 

The development of three-phase reactor technologies in the 1970 s saw renewed interest in the synthetic fuel area due to the energy crisis of 1973. Several processes were developed for direct coal liquefaction using both slurry bubble column reactors (Exxon Donor Solvent process and Solvent Refined Coal process) and three-phase fluidized bed reactors (H-Coal process). These processes were again shelved in the early 1980 s due to the low price of petroleum crudes. 

Shah, Y. T., Reaction Engineering in Direct Coal Liquefaction. Addison-Weslcy publishing Company, London, 1981. 

Coal liquefaction, 6 765-766, 832-869 coprossing, 6 856-858 direct, 6 833-858 indirect, 6 858-867 use of steam in, 23 239-240 Coal mining, 6 744-745 Coal-oil coprocessing, 6 833, 856-857 Coal petrography, 6 706-709 Coal petrology, 6 706 Coals, ash properties of, 72 324t Coal slurry pipelines, 6 748 Coal tar... 

DCL DDGS DEFC DICI DISI DME DMFC DOE DP DPF Direct coal liquefaction Distillers dried grains with solubles Direct ethanol fuel cell Direct-injection compression ignition Direct-injection spark ignition Dimethylether Direct methanol fuel cell Department of Energy (USA) Dynamic programming Diesel particulate filter... 

Much of the research pursued by the authors of this paper and by their associates has involved studies of the catalytic hydrogenation of coals in the absence of solvent. The technique has been used to elucidate the mechanisms of catalytic coal liquefaction and to provide simultaneously some insight into the structure of coals. Peter Given was directly instrumental in providing the incentive for this research which has extended since 1983. Previous findings were disseminated through several publications (4-8. In this paper, some of the earlier data have been collated with more recent results (9) to provide an account of the relevance of these studies to the two-component concept. 

Since the earliest days of coal liquefaction processing and research, the need for correlations of coal properties with coal reactivity under direct hydroliquefaction conditions has been recognized by coal scientists. This article traces the history of reactivity correlations from the earliest work of Bergius through the classic work at the Bruceton Bureau of Mines during the 1940 s to the most recent advances in this subject. Particular emphasis in this review is placed on an examination of the contributions of Professor Peter Given and his co-workers. Reactivity methodologies and techniques for correlation are presented and critically evaluated for utility and applicability as predictive tools. 

Derbyshire, FJ., Catalytic Coal Liquefaction by Temperature-Staged Reaction, presented at Direct Liquefaction Contractor s Review Meeting, Pittsburgh, PA (Oct. 20-22, 1986). 

Much of the recent research in direct coal liquefaction seeks to develop methods for dissolving coal at low reaction severity (defined as temperatures below 350 and pressures of 1000-1500psig). Most of these efforts have been prompted by several incentives that exist for converting coal at milder reaction conditions than those utilized in conventional processes, including ... 

Derbyshire. F.J. Catalysis in Coal Liquefaction New Directions for Research lEA Coal Research London, June 1988. 

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