Showing papers on "Carbochemistry published in 1988"
TL;DR: In this article, a model for the rapid devolatilization of individual coal particles is developed by analogy with a single-stage equilibrium flash distillation, and the model accurately correlates the yields of noncondensible gas and tar from bituminous coals over wide ranges of temperature and pressure.
Abstract: A model for the rapid devolatilization of individual coal particles is developed by analogy with a single-stage equilibrium flash distillation. In the theory, thermal depolymerization of the coal generates aromatic fragments that are widely distributed in size. Conditions for phase equilibrium determine the partitioning of these fragments into intermediates in the condensed phase, which ultimately form char and light gas, and into tar vapor, which escapes in a stream of light gases. Comparison with data shows that the model accurately correlates the yields of noncondensible gas and tar from bituminous coals over wide ranges of temperature and pressure. The predicted molecular weight distributions of tar are also in agreement with measured distributions, and the model yields a mechanistic basis for their observed insensitivity to temperature. The tendency to form lighter tar at higher pressures is also explained.
79 citations
TL;DR: In this paper, the rate of formation of acetylene, the most interesting product of coal pyrolysis in hydrogen plasma, is determined by heat transfer to coal and by the kinetics of pyrotechnics and homogeneous gas phase reactions.
57 citations
57 citations
TL;DR: In this article, the authors investigated the effect of stable carbon-oxygen complex formation on thermogravimetric analysis (TGA) profiles of coal char in oxygen and carbon dioxide and found that the observed differences between reactivity profiles obtained by TGA and those obtained by product gas analysis (e.g. non-dispersive infrared spectroscopy) can be attributed to significant amounts of stable complex being formed during the initial stages of reaction.
44 citations
40 citations
TL;DR: The influence of hydrogen and carrier or diluent gases on water vapor gasification was studied at total pressures between 0.15 and 2 MPa with chars prepared at 600°C from brown coal, sugar, and polyvinyl chloride and with a glassy carbon (HTT 1100°C) as mentioned in this paper.
39 citations
TL;DR: In this paper, coal of different ranks were preswollen using THF as swelling solvent, and the swelling ratio was higher for low rank coals than for high rank coal.
37 citations
TL;DR: In this article, five coal chars were prepared at 1273 K from coals of different rank using the shrinking spherical ashless particle model of gasification, activation energies and frequency factors were evaluated.
34 citations
33 citations
TL;DR: In this paper, isothermal pyrolysis studies were conducted on an Illinois No. 6 and a Wyodak coal at 375 °C, 400 °C and 425 °C using a fluidized sandbath reactor system.
28 citations
TL;DR: In this paper, a steady-state model has been developed to simulate the North Carolina State University pilot-scale fluidized bed coal gasification reactor, which involves instantaneous devolatilization of coal at the top of the gasifier (freeboard region) and char combustion and gasification in the fluidization bed.
TL;DR: In this paper, the sulfidation of reduced Fe by elemental sulfur, competing with reoxidation of the iron catalyst by water, was investigated in coal liquefaction, and it was shown that with the addition of sulfur, active and oxidation-proof pyrrhotite is formed, and the degree of reduction of the remaining iron oxide is maintained higher than that in the absence of elemental sulfur.
01 Jan 1988
TL;DR: In this article, a new approach for quantitative 13C NMR Spectroscopy of coal has been proposed for quantitatively estimating thermal properties of coal liquids using NMR spectra.
Abstract: I. Structure of Coal.- The Origin of Coals.- The Nature and Origins of Coal Macerals.- Macromolecular Structure of Coals: Status and Opportunities.- Solvent Swelling of Coals.- Solid State 13C NMR in Coal Research: Selected Techniques and Application.- A New Approach for Quantitative 13C NMR Spectroscopy of Coal.- Structural Analysis of Coal Derivatives.- Estimating Thermophysical Properties of Coal Liquids Using NMR Spectra.- The Infrared Spectra of Coals, 1980-1986.- to Coal Photochemistry.- Coal Characterization by Means of Curie-Point Pyrolysis Techniques.- Chromatographic Techniques in Coal Science.- The Oxygen Functional Groups in Bituminous Coal.- II. Reactivity of Coal.- Slow and Rapid Pyrolysis of Coal.- Coal Liquefaction Kinetics.- Catalysis of Coal Liquefaction.- Solubilization of Coal.- Supercritical Gas Extraction of Coal.- Coal Desulphurization. The Protodesulphurization of Naphthalene Thiols and Sulphides.- Kinetics of Coal Gasification.- Transport and Other Effects in Coal Gasification.- Fluidized Bed Combustion of Coal.- Prediction of the Behaviour of Atmospheric Fluidized Bed Coal Combustors.
TL;DR: In this article, the effect of coal pre-hydrogenation under relatively mild conditions (400 °C, 7 M Pa hydrogen pressure) using a dispersed sulphided molybdenum catalyst on fluidized bed pyrolysis at atmospheric pressure and fixed-bed hydropy-lysis was investigated for a UK bituminous coal (82% dmmfC).
TL;DR: In this paper, the effects of increasing coal concentration on the coprocessing performance of the CANMET process operating with an Alberta subbituminous coal and more of the Cold Lake vacuum bottoms (CLVB).
Abstract: Coprocessing represents an attractive combination of heavy oil upgrading and coal liquefaction technology. Compared with coal liquefaction, coprocessing eliminates or reduces the use of a recycle oil solvent. This results in a greater proportion of the reactor volume being occupied by upgradable feedstock rather than recycle solvent. The net result is higher effective reactor throughput and lower capital and operating costs. Compared with heavy oil upgrading, coprocessing offers the ability to increase operating margins by replacing expensive oil with lower cost coal. There are also other benefits related to the ability of the added coal to act as an adsorbent for coke formed during the reaction and for heavy metals present in most feedstocks. For some processes and under certain operating conditions there is also the possibility of synergistic effects which result in better process yields. In the final analysis the real challenge is to make coprocessing more economically attractive than heavy oil upgrading and this requires a better understanding of the effects that adding more coal to the feed can have no fundamental process behavior. This paper describes the effects of increasing coal concentration on the coprocessing performance of the CANMET process operating with an Alberta subbituminous coal andmore » Cold Lake vacuum bottoms (CLVB).« less
TL;DR: The mechanism for the formation of sulphate and sulphides in sulphur-promoted iron oxide catalysts for coal liquefaction has been discussed in this paper, where the catalysts used were FeS, FeS 2 and Fe 3 O 4 of analytical reagent grade, and iron (Fe 2 O 3 ) prepared by precipitation from ferric nitrate.
TL;DR: In this article, the effects of potassium carbonate and ferric oxide on the thermoplastic properties of weakly caking coal have been investigated using a high-pressure dilatometer.
TL;DR: In this article, the chloroform-soluble extracts from two coals, a low rank coal (lignite from Utrillas, Teruel) and a bituminous coal (Illinois No. 6 River King) were subjected to dry catalytic hydroliquefaction and the compositional changes were followed.
TL;DR: The phase behavior of pyrene-tetralin mixtures in the temperature range 620-700 K was investigated in this paper, where degradation products including naphthalene, 2 3 dihydro 1-methyl indene, and dihydropyrene were identified.
TL;DR: In this article, a number of products of the liquefaction of a set of 26 high-sulphur coals having already been reported, structural characteristics of the derived asphaltenes and their parent coals are now presented.
TL;DR: In this paper, Peptostreptococcus productus metabolized coal gas to mainly acetate and CO2 and used methanogens to convert these products to methane.
Abstract: Biological conversion of low-Btu coal synthesis gas to higher Btu methane was demonstrated using both pure co-cultures and/or adapted-mixed anaerobic bacteria.Peptostreptococcus productus metabolized coal gas to mainly acetate and CO2. The co-cultures containing methanogens converted these products to methane. In mixed culture studies, CH4 and small amounts of acetate were produced. Reactor studies using stirred-tank and immobilized cell reactors exhibited excellent potential to convert CO, CO2 and H2 to methane at higher gas flow rates. Gas retention times ranging from 0.7 to 2 hours and high agitation were required for 90 percent CO conversion in these systems. This paper also illustrates the potential of biological methanation and demonstrates the need for good mass transfer in converting gas phase substrates.
TL;DR: In this article, the microstructure of a North Dakota lignite, a Washington subbituminous and a New Mexico bituminous coal and their chars produced by devolatilization in nitrogen at 1000 to 1300°C was investigated using the CO 2 adsorption method conducted at 25°C.
TL;DR: In this article, the pyrolysis of 1-naphthol in nitrogen and hydrogen, with and without a donor solvent, has been studied, and the results show that in the absence of a source of donatable hydrogen, phenolic groups can condense at around 450 °C to form fused furan type structures.
TL;DR: The velocities of ultrasonic wave propagation in tetrahydrofuran solutions of coal extracts from various coals (within the range 649-856% carbon) have been measured in this paper.
TL;DR: The catalytic liquefaction of a subbituminous coal has been studied in the absence of solvent using an impregnated sulphided Mo catalyst in the range 300-400 °C as mentioned in this paper.
TL;DR: In this paper, the effect of hydrogen gas, tetralin and decane on pyrolysis of bituminous coal, before and after extraction with chloroform, has been studied by in situ e.g. in a flowing gas cell at atmospheric pressure.
TL;DR: In this paper, a modele de la reaction tenant compte de la formation de semi-coke durant la liquefaction, par recombinaison des fragments reactifs formes par chauffage du charbon is proposed.
Abstract: Sur la base d'experiences systematiques, on developpe un modele de la reaction tenant compte de la formation de semi-coke durant la liquefaction, par recombinaison des fragments reactifs formes par chauffage du charbon