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Dive into the research topics where Richard C. Neavel is active.

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Featured researches published by Richard C. Neavel.


Fuel | 1976

Liquefaction of coal in hydrogen-donor and non-donor vehicles

Richard C. Neavel

Abstract Coal, slurried with tetralin, and heated rapidly to 400 °C, was converted to benzene-soluble, liquid products through a reaction path which appears to involve thermal cleavage of chemical bonds in the coal (so-called depolymerization). Free radicals formed pyrolytically were stabilized in the early stages by autogenous hydrogen transfer, and in later stages by abstraction of hydrogen from the hydrogen-donating tetralin (which was converted to dihydronaphthalene and then to naphthalene). Vitrinite of the coal particles became almost completely soluble in pyridine after 5 min reaction, and dispersed in the vehicle (tetralin) within about 10 min. Reaction in non-donor vehicles (naphthalene, dodecane) resulted in dispersion, but ‘repolymerization’ formed a benzene-insoluble material. Hydrogen transfer from tetralin increased exponentially with increased conversion of the coal to benzene-soluble material. Negligible influence of particle size (below 2–3 mm) implies that mass transfer is not a rate-limiting factor. High-volatile c bituminous coal and coals of lower rank converted at about the same rate and to the same extent (given equivalent petrographic compositions); approximately two-thirds of the ultimately achievable conversion occurs within 20 min. Higher-rank coals converted at a lower rate. Oxidation of the coal was deleterious to ultimate conversion.


Fuel | 1982

Behaviour of calcium as a steam gasification catalyst

Robert J. Lang; Richard C. Neavel

Abstract The catalytic coal gasification process for synthetic natural gas, which is being developed by the Exxon Research and Engineering Company, uses a potassium salt to catalyse the steam gasification of coal while it simultaneously catalyses methanation reactions in the same vessel. The catalyst is recovered from the gasifier residue and recycled, but some is lost. These relatively small, but inevitable, losses from the recovery process provide an incentive to find a lower-cost catalyst. Exploratory catalyst screening studies have shown that calcium compounds provide good catalytic activity under certain conditions. Essentially, the calcium must be atomically dispersed throughout the char to obtain good activity. Potassium compounds tend to be mobile and distribute themselves during gasification even when applied to the coal in a dry, mechanical mixture. Calcium, in contrast, is poorly active unless it is very well dispersed by chemical reaction with the organic matter. For example, it is an active catalyst when it is transferred to acid sites in coal by ion exchange. Sufficient sites occur naturally in lower-rank coals, and some of these coals have undergone ion-exchange with calcium naturally. Such coals show high reactivities during gasification for this reason. Higher-rank coals have fewer ion-exchangeable acid sites, but these can be created by a mild air-oxidation. This paper describes the experimental techniques used, to develop low-cost, calcium catalysts for the steam gasification of coal and presents the results obtained in this work.


Fuel | 1981

DTGA combustion of coals in the Exxon coal library

Stewart E. Smith; Richard C. Neavel; Edwin J. Hippo; Robert N. Miller

Coal combustion experiments were carried out over the temperature range 25–900 °C using air at atmospheric pressure in a derivative thermogravimetric analysis system. Sixty-six coals high in vitrinite (> 80% mineral-matter-free basis) and low in inorganics (all but 12 samples < 10%) were examined as part of a coal characterization programme. The coals varied in rank from lignites (69% carbon on a dry, mineral-matter-free basis) to low-volatile bituminous (91% carbon). Combustion rates increased progressively with increasing temperature, passed through maxima and then declined. The rate data were fitted to an Arrhenius equation and plots showed four distinct regions of combustion. Apparent activation energies were calculated for each region and varied from ≈4 kJ mol−1 in the high-temperature, diffusion-controlled region to 290 kJ mol−1 in the chemical-reaction controlled, low-temperature region. The temperatures at which 50% of the sample had burned away (sol12-life) were rectilinearly related to oxygen and carbon contents (correlation coefficient squared values of 0.88 and 0.86, respectively).


Fuel | 1980

Carbonization and liquid-crystal (mesophase) development. 15. A common stage in mechanisms of coal liquefaction and of coal blends for coke making

Harry Marsh; Richard C. Neavel

Abstract This paper discusses the processes of coal liquefaction and co-carbonization of coal/pitch blends in terms of physical and chemical properties of the fluid phases found in both pyrolysis systems. Mechanisms of development of thermal plasticity in coals are outlined. In coal liqudfaction the importance is stressed of hydrogen-donor vehicles interacting with the products of thermal depolymerization of coal. The concept of variations in the facility of solvation and solvolysis of additives in co-carbonizations can explain the variations observed in degrees of interaction of a single coal with several additives. Possibly, the hydrogen-donor facility of an additive may be as important in assessments of modifying ability as an average molecular structure. The possibility exists of using an analysis of optical texture of cokes resulting from the fluid coal/solvent pyrolysis systems to characterize the effectiveness of solvents in coal liquefaction systems as distinct from coal blending co-carbonization studies.


Fuel | 1986

Interrelationships between coal compositional parameters

Richard C. Neavel; Stewart E. Smith; Edwin J. Hippo; Robert N. Miller

Abstract Analytical data from a set of 66 coal samples, ranging in rank from lignitic to low-volatile bituminous, were used to define relationships between coal properties. Unusual care was taken in selecting, collecting, preparing and analysing this set of premium samples providing a high degree of confidence in the conclusions obtained. It was found that univariate relationships between properties, which might seem to convey useful information, are generally of limited operational value and can lead to erroneous conclusions. However, multivariate correlations can predict a number of properties. Specific energy, volatile matter yield, and density (by helium pycnometry) can be estimated from the elemental composition according to the following expressions: Btulb−1 = 145.9%C + 569.6%H − 53.89%O + 43.08%S − 6.3%Ash%VM = −0.408%C + 11.25%H + %O + 1.3%Sgml−1 = 0.01556%C − 0.04117%H + 0.02247%O + 0.02049%S + 0.0208%Ash The standard deviations of the residuals (estimated-experimental) for the above three correlations are 86 Btu lb−1, 1.5% VM and 0.013 g ml−1. The free-swelling index was found to correlate strongly with the oxygen content (for coals containing > 2 wt% oxygen, daf) and the petrographic composition according to the following expression: FSI = 5 + 4.68f(O) − 0.00395NPC2 + 0.0897NPC − 0.06LIP where f(O) = sin(0.2513Odaf + 0.9505)NPC = ashweight% + inertinite, volume% mineral-freeLIP = liptinite, volume%, mineral-free It is concluded that the elemental composition of coal can predict many physical properties and process responses. The petrographic composition must be considered when predicting plastic properties. Though petrographic composition influences other properties and process responses, microscopically obtained maceral percentages did not prove useful for quantitatively predicting properties or responses.


Coal Science#R##N#Volume 1 | 1982

Coal Plasticity Mechanism: Inferences from Liquefaction Studies

Richard C. Neavel

Publisher Summary Coal liquefaction experiments indicate that the formation of low molecular weight products from high molecular weight coal proceeds via the thermal rupture of relatively weak chemical bonds followed in the optimum case by stabilization of the resulting free radicals by hydrogen atoms that are abstracted from hydroaromatic structures. In particular, the hydroaromatic hydrogens on partially saturated, multiring, and organic molecules in the vehicle are readily abstracted in this process. If abstractable hydrogen is not readily available, some of the pyrolytically formed free radicals either recombine or attack adjacent molecules, forming stable, higher molecular weight materials called repolymerization. Thermally promoted plasticity of vitrinite in bituminous coals involves these same chemical reactions; however, while the slurrying vehicle is the major source of transferable hydrogen in liquefaction, the coal itself is the source of such hydrogen in inert-atmosphere pyrolysis. This chapter discusses three properties of coal, which are necessary and sufficient for plastic development: (1) lamellae-bridging structures, (2) an indigenous supply of hydroaromatic hydrogen, and (3) an intrinsic capability of micelles and lamellae to become mobile independently of quantitatively significant bond rupture.


Fuel | 1980

Alkylation: a beneficial pretreatment for coal liquefaction

Richard H. Schlosberg; Richard C. Neavel; Peter S. Maa; Martin L. Gorbaty

Abstract Several coals were alkylated employing isopropyl and methyl halides under Friedel-Crafts conditions. These alkylated coals, and corresponding untreated coals, were processed (liquefied) with tetralin in batch autoclaves (tubing bombs) at 700 K, 130 min residence time, and 10 MPa (1500 psi) hydrogen pressure. Conversion to cyclohexane-soluble liquids was found to be 10–21 percent higher (on an alkyl-group-free basis) for the alkylated coals than for untreated coals. These results are explained on the premise that alkylation beneficially disrupts the coal structure sufficiently to allow improved contacting between coal and tetralin.


Fuel | 1980

Technique to measure the temperature of agglomeration of coal ash

Joanne J. Stallmann; Richard C. Neavel

Abstract Examination of deposits from gasification pilot units indicates that agglomerates of fused ash appear to form at temperatures below the initial deformation temperature as defined by the ASTM ash fusion test. A simple method was developed to estimate the temperature at which coal ash will begin to fuse or agglomerate in process equipment. This test confirms that fusion of ash occurs at temperatures below those of the ASTM ash fusion test. The test also offers a method to compare the fusion properties of ashes for several coals.


Fuel | 1986

Estimation of coal washability using X-radiography

Ashok Kumar Moza; Richard C. Neavel

Abstract The ability to clean coal commercially depends upon the spatial distribution of the mineral matter within the organic coal matrix. The conventional method for defining the washability of a coal involves sink-float tests that are tedious, time-consuming and expensive. In this report, a procedure is described that employs X-radiography to assess the mineral distribution in exploration drill core samples. Mineral matter is more dense to X-ray penetration, and hence mineral particles are visible as areas of low transmission on an X-radiograph. The transmission characteristics of an X-radiograph can be digitized with high resolution, and thus the mineral distribution can be quantitatively defined. Appropriate computer manipulation of the digitized data can provide a measure of the mineral distribution and, hence, the washability characteristics of the coal. The theory, practice and experimental validation of the concept are described in this paper.


Fuel | 1979

Estimation of sulphur content in coal from titration of calorimeter bomb washings

Richard C. Neavel; John E. Keller

Abstract In routine coal quality analyses, calorific value and sulphur content are commonly determined. In this paper, we describe a procedure whereby the sulphur content of a coal sample can be estimated with reasonable accuracy from the titration of the calorimeter bomb washing. The procedure requires only an initial estimation of several correction factors and, for subsequent samples, their routine use, along with titration data, in a simple calculation. The estimated sulphur contents of 713 (93%) of 768 samples to which the procedure was applied, differed from values determined in the standard sulphur analysis by less than 1% sulphur. The estimated value can be used as a substitute for a separate, standard sulphur analysis, and is especially useful where coal from one source is routinely analysed. The technique also provides a direct calorimeter correction for heat of formation of sulphuric acid, obviating the necessity for an independent sulphur analysis as specified in standard procedures.

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