摘要:

Bromination of anthracite has been performed by exposure of anthracite to bromine vapor. Bromine absorption was evident by weight uptake. On further bromination, anthracite disintegrated into a fine powder. Differential scanning calorimetry has been used to characterize the thermal behavior of anthracite before and after bromination. The measurement was made by using the Perkin‐Elmer Model DSC‐2. Combustion of anthracite was achieved by heating the sample in the presence of a flow of oxygen at 40 psi. The exothermic peak which is associated with combustion was observed to commence at 868°K in pristine anthracite and at 890°K in brominated anthracite. The height of the peak is independent of bromine concentration, but the width of the peak decreases significantly with increasing bromine concentration.

ISSN:0094-243X    

DOI:10.1063/1.32933

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

In a coal‐burning MHD (Magnetohydrodynamic) power plant, the use of a regenerative air heater is one option for producing the required high plasma temperatures. However, thermal, mechanical and chemical stresses which the MHD environment places on materials are enormous and candidate materials must be carefully tested. We report on the results of such testing for a variety of materials studied in heater test facilities at both FluiDyne Engineering Corporation and at Montana State University. We describe the experimental program and test facilities for MHD heater development, the rationale for the choice of materials, and their performance (success or failure) under various envirnoments (slagging and nonslagging). Future materials needs are discussed in light of the observed effects.

ISSN:0094-243X    

DOI:10.1063/1.32935

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Coal gasification is most efficiently performed in a fluidized bed, but the inability to mathematically describe the process has hampered scaling up the gasifiers. New techniques to measure the velocity distribution of the fluidized particles may provide data to critically evaluate models for scaling. This velocity profile can be obtained with a laser Doppler velocimeter (LVD) that is fast, simple, accurate and nonperturbing to the flow. The technique has been demonstrated with a multiple‐beam LDV developed in this lab on a two inch diameter by eight foot high fast fluidized bed. In this instrument, a large number of beams intersect to form sharp, intense spots well separated by dark area, rather than the sinusoidally varying intensity pattern of the conventional two beam LDV. This modification provides a less ambiguous description of velocities. From first principles the correlation function of particles moving through the measuring volume is calculated and experimentally verified with particles traveling at a uniform speed. This technique is then used to map out the velocity profile in the fluidized bed as a function of height in the bed, proximity to the wall, and pressure drop over the bed. (This work performed with support from theEnergyResearchCenterof West Virginia University).

ISSN:0094-243X    

DOI:10.1063/1.32936

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A North Dakota lignite and a New Mexico sub‐bituminous coal have been hydrogenated at up to 900°C and 2500 psi hydrogen pressure. Yields of gaseous hydrocarbons and aromatic liquids have been studied as a function of temperature, pressure, residence time, feed rates and H2/coal ratio. Coal feed rates in excess of 10 lb/hr have been achieved in the 1 in. I. D.×8 ft reactor and methane concentration as high as 55% have been observed. A four‐step reaction model was developed for the production and decomposition of the hydrocarbon products. A single object function formulated from the weighted errors for the four dependent process, variables, CH4, C2H6, BTX, and oil yields, was minimized using a program containing three independent iterative techniques. The results of the nonlinear regression analysis for lignite show that a first‐order chemical reaction model with respect to C conversion satisfactorily describes the dilute phase hydrogenation. The activation energy for the initial products formation was estimated to be 42,700 cal/gmole and the power of hydrogen partial pressure was found to be +0.14. The overall correlation coefficient was 0.83. The mechanism, the rate expressions, and the design curves developed can be used for scale‐up and reactor design.

ISSN:0094-243X    

DOI:10.1063/1.32938

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The importance of zinc chloride as a catalyst in conversion of coal to liquid and gaseous fuels is well known and study of the aspects of its reaction with coal are warranted. Recent studies have reported the likelihood that certain transition metal halides, both anhydrous and hydrated, will separate the graphite‐like planes of condensed aromatic carbon rings in the coal to produce intercalation compounds. The work described in this paper uses X‐ray powder diffraction to investigate the question of whether the efficiency of zinc chloride as a coal liquefaction and gasification catalyst could possibly involve the formation of intercalation compounds as an intermediate step thus providing a method for reagents to penetrate the solid coal. Evidence is presented that such compounds may, indeed, be formed. Furthermore, addition of zinc metal reduces the weight of zinc chloride (or zinc oxide) needed to form the apparent intercalation compounds with coal. Experiments with magnesium compounds indicate that the results with zinc compounds and coal cannot be extended to the analogous magnesium species.

ISSN:0094-243X    

DOI:10.1063/1.32940

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Scientists in the Soviet Union have demonstrated that high pressure shock‐wave loading can cause significant improvement in the performance of catalysts. This increased catalytic activity is apparently the result of the shock‐induced defects, especially vacancies, which act to facilitate atomic migration. We have carried out shock activation experiments on a coal‐derived pyrite which has been previously used as a catalyst in coal liquefaction studies. The pyrite powder was packed to a density of about 2.0 Mg/m3in a copper capsule and explosively loaded to a pressure of about 15 GPa in the copper. The starting and shock‐activated samples were analyzed by x‐ray diffraction and magnetization measurements. The diffraction patterns of the shock‐activated samples were dominated by broadened pyrite lines indicative of a significant increase in crystal defects. The diffraction patterns also showed the presence of pyrrhotite (Fe1−xS) in quantities of a few percent. An iron carbide found in the shocked material was apparently formed from carbon originating from either the calcite or organic impurities in the starting material. Magnetic properties of the sample were found to be substantially changed by the shock loading. The study has demonstrated that shock loading can significantly alter the crystalline order of pyrite and produce measurable quantities of pyrrhotite. The effects of shock‐activated pyrite on the liquefaction of coal are being assessed by means by tubing reactor experiments.

ISSN:0094-243X    

DOI:10.1063/1.32898

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

New procedures have been developed for preparation of improved methanation catalysts. Supported metal catalysts have been prepared, starting with controlled solidification (undirectional or gas atomization) of eutectic or proeutectic alloys of transition metals (rhodium and nickel) and aluminium, followed by chemical dissolution in caustic of the aluminum component and acid precipitation of the aluminum as alumina to provide a high surface area oxide matrix for the dispersed catalytically active rhodium (0.36 w/o) or nickel (6.1 w/o). Unsupported skeletal nickel catalysts have been produced by gas atomization and rotary atomization techniques from proeutectic nickel (28.6 w/o Ni) aluminum alloy powders by caustic activation. Characterization of the supported and unsupported catalysts by x‐ray diffraction, electron microscopy, BET nitrogen adsorption and hydrogen chemisorption demonstrated that the activated metals, rhodium and nickel, were in a highly dispersed state and, in the case of the alumina supported catalysts, present on a high surface area stabilized substrate. The superior surface physical properties, pore structure, total surface areas and available metal surface areas, and the superior initial catalytic activity of these experimental catalysts compared with more conventional rhodium and nickel supported and RaneyRcatalysts establish the merits of controlled solidification procedures as a new path for synthesis of methanation catalysts.

ISSN:0094-243X    

DOI:10.1063/1.32899

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The ultimate goal of this research program is to discover characteristic molecular reaction pathways, and their kinetic behavior, in high temperature condensed‐phase systems containing aromatic substances. Such information can then be applied to the thermal chemistry of coal system. We shall present recent progress in which experimental determinations of product evolution rates in well‐defined ’’model’’ systems are analyzed using quantitative models consistent with available thermochemical and kinetic data. Two types of systems will be discussed, namely, bond breaking in tetralin and liquid‐phase pyrolysis of pure 1,2‐diphenylethane. Implications of these results for interpreting coal reactions will also be discussed.

ISSN:0094-243X    

DOI:10.1063/1.32901

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A model for coal liquefaction has been developed which is based on the concept of the thermal bond cleavage step being rate limiting. The model provides rate laws which describe the preasphaltene, asphaltene, oil and gas time/yield curves for the coal liquefaction process. The quantitative agreement between the derived rate laws and the kinetic data obtained from fifteen publications will be presented. A general liquefaction reaction scheme was developed and used to relate the proposed model to the experimentally observed products. For the diverse coal liquefaction systems studied, the rate constants obtained from analysis of the benzeme solubles plus gas/time data vary from &angupr;1 to 46×103min−1for data covering the later stages of conversion at temperatures between 350° to 450°C. The rate constant ranges for preasphaltene, asphaltene, oil and gas formations were found to be 1.0 to 56.0 min−1, 0.03 to 0.1 min−1, 0.003 to 0.1 min−1and 0.007 to 0.2 min−1respectively over the 350° to 450° range. The rate constant ranges for preasphaltene and asphaltene disappearance were found to be 0.03 to 0.09 min−1and 0.005 to 0.06 min−1respectively. Based on the quality of the kinetic fit to the reported coal liquefaction systems, which cover a diverse range of reaction conditions, coal types and donor solvent compositions, it is proposed that the thermal bond cleavage/hydrogen capping model provides a good, quantitative description of the rate limiting processes occurring during coal liquefaction.

ISSN:0094-243X    

DOI:10.1063/1.32902

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Valves used for drawdown of the solids produced in the coal liquefaction process must be designed to operate at high temperatures and must prevent the buildup of solids within the valve internals to insure operability. Consideration must also be given to materials used for seating surfaces in terms of being able to withstand abrasion. Research into the design and materials for this application results in a new ball valve design with a special inlet port liner and O‐ring seal. A prototype valve was built and put in service in a small scale, experimental coal liquefaction plant. For comparative purposes a standard design valve was also used, with both valves being subjected to over 1000 open/close cycles, after which both valves were removed, tested, and disassembled for inspection. The results of this experimental program will be presented, including process parameters, service conditions, and material evaluation. Particular emphasis will be placed on wear of seating surfaces and the effects of process material on the physical properties of seal and packing materials.

ISSN:0094-243X    

DOI:10.1063/1.32904

出版商:AIP    

年代:1981

数据来源: AIP