John C. Crelling

Determining the petroleum-generating potential of coal using organic geochemistry and organic petrology

Abstract The Ardjuna Basin of northwest Java is typical of many Tertiary basins in that it contains high-wax crude oil. Pyrolysis–gas chromatography revealed that potential precursors of long chain (waxy) paraffins are present in coals of the Talang Akar formation, and are most abundant in those that are rich in “matrix liptinite”. Conversely, it was not possible to estimate waxy oil-generating potential using Rock Eval because pyrolysates from Talang Akar coal are mainly comprised of naphthenic and aromatic compounds, these being derived from resinite and “fluorescing vitrinite”. Because of a controlling influence by the abundance of these macerals, changes in Hydrogen Index could not be used to assess maturity. Resinite and related macerals might play an especially important role in petroleum expulsion, as evidenced by their high genetic potential and, hence, inherent capability of saturating the source rock pore system. It is speculated that their maturation products, while not constituting “typical” crude oil, might pervade the coal fabric, deactivate adsorptive sites and hence facilitate the expulsion of waxy oil that is generated from matrix liptinite.

Reactivity of coal macerals and lithotypes

Abstract Variations in the rank of coal used for power generation can cause problems with the efficiency of combustion. This paper describes an examination of the effects of variations in the maceral composition of coals, in association with rank, upon reactivity in combustion. Using a simple reactivity test, the reactivity ranges for two rank series of single seam coals were determined along with the reactivity ranges obtained from studying lithotypes of various maceral concentrations of a single coal. Reactivity tests on pure maceral concentrates show significant reactivity differences between macerals so that coal type (maceral/lithotype content) must be considered as important a parameter as rank. Changes in maceral concentration alone could account for 45% of the rank reactivity variation without changing rank.

Combustion characteristics of selected whole coals and macerals

Abstract The overall objective of this project was to determine the combustion properties of separated single coal maceral fractions from a rank series of coals and then to try to predict the combustion behaviour of various whole coals on the basis of their maceral compositions and rank. The combustion properties studied were based on the burning profile in a TGA apparatus. The results of this study indicate that most of the reactivity and combustion profile parameters varied significantly with coal rank and that all of the rank trends observed were best defined in the data from the single maceral samples which were more reproducible, more linear, and less variable. The variations in the combustion profiles and reactivities in different macerals from the same sample are of the same order of magnitude as the variations due to rank. It also appears that there are some maceral interactions during combustion and gasification that significantly affect these processes.

Structural studies of wear debris from carbon–carbon composite aircraft brakes

Abstract Microstructural studies using X-ray diffraction, SEM, and optical microscopy were made of wear debris from carbon–carbon composite aircraft brakes produced under different simulated braking operations. Under simulated cold taxiing conditions, particulate wear debris comprising a disordered carbon phase containing fibre fragments is formed. The disordered phase is produced mainly by shear deformation of the graphitic CVI matrix in the parent carbon–carbon composite. Under simulated landing conditions the wear debris is partly transformed by shear processes into a friction film with a similar disordered microstructure to the wear debris formed during taxiing. The friction film is formed as a result of the higher power density and interfacial temperatures during landing. The very high power densities and interface temperatures that apply during rejected take-off result in shear-stress assisted graphitisation of the friction film, but with a fine mosaic texture that is quite different from the texture of the CVI matrix in the parent composite.

A flash pyrolysis and petrographic study of cutinite from the Indiana paper coal

Abstract Samples obtained from the high-volatile bituminous Indiana cuticle-rich and paper coals (Indiana U.S.A.) were investigated by white light and blue light microscopy and by Curie point pyrolysis-mass spectrometry in combination with multivariate data analysis, Curie point pyrolysis-gas chromatography and Curie point pyrolysis-gas chromatographymass spectrometry. Samples obtained from several sites and of different degrees of weathering were analyzed. The macerai cutinite from the same samples was studied as well. The cutinite was concentrated by a standard palynological chemical oxidation technique as well as by density gradient centrifugation. The major constituent of the Indiana paper coal samples appeared to be a recently discovered non-saponifiable polymethylenic biopolymer, present in both recent and fossil plant cuticles. The maceral cutinite is almost exclusively made up of this highly resistant biopolymer. It is shown that upon severe natural weathering this biopolymer, because of its resistance against organic alteration and diagenesis, is relatively enriched and manifests itself in humic coals as the maceral cutinite.

FOSSIL CHARCOAL IN CRETACEOUS-TERTIARY BOUNDARY STRATA : EVIDENCE FOR CATASTROPHIC FIRESTORM AND MEGAWAVE

Abstract Organic matter separated from calcareous sandstone from the upper portion of a deep-water tsunami deposit at Arroyo el Mimbral, Taumalipas, Mexico, which marks the biostratigraphically defined Cretaceous-Tertiary boundary, consists primarily of fossil charcoal, including semifusinite and pyrofusinite. Analytical pyrolysis-gas chromatography/mass spectrometry revealed the highly aromatic and polyaromatic character of the organic matter assemblage, typical of the products of partial combustion. The organic matter probably originated as terrestrial vegetation that was caught in a firestorm and subsequently transported far offshore in the backwash of a megawave. These data are consistent with the hypothesis of combustion of large masses of vegetation triggered by a giant extraterrestrial impact in the Gulf-Caribbean region (probably forming the Chicxulub crater in Yucatan) at the very end of the Cretaceous Period.

Nitrogen release from a rank series of coals during temperature programmed combustion

Abstract This investigation has involved the study of NOx release during the combustion of a wide range of coals of different rank and geographic origin. Temperature programmed combustion studies of coals using a thermogravimetric analyser-mass spectrometer (TGA-m.s.) show that the oxidative gasification profiles of the coals have two main regions, corresponding mainly to the gasification of volatiles and of the chars formed in situ during pyrolysis. Calculation of the fuel N conversion to various nitrogenous species, using the integrated area under each gas evolution profile, combined with the analytical data shows that coal N conversion to NO is rank dependent, with the fractional conversion of coal N increasing with rank especially for the low to medium rank bituminous coals where the increase is most noticeable. The NO-fuel N ratio for all the coals studied varies in the range of 11–42%. The conversion of fuel N to N2 does not show definite trend with rank. Significant amounts of HCN (10–15%) were also detected during gasification for some of the coals investigated. The studies show that coal-char N conversion to NO during combustion is related to reactivity with the more reactive coals having lower NO-N ratios.

Current uses of fluorescence microscopy in coal petrology

Fluorescence analysis of the liptinite maceral content of various U.S. coal seams has shown that these macerals are consistently under‐counted in conventional white‐light analysis. Fluorescence analysis revealed a greater variety of liptinite macerals as well as a large amount of fluorescing vitrinite in all of the coals studied. However, pseudovitrinite was not observed to fluoresce. Textures and structures not visible in normal viewing are also seen in fluorescence analysis. Quantitative spectral analysis of single coals has shown that most liptinite macerals can be both petrographically and statistically separated on the basis of fluorescence parameters, with the wavelength at maximum intensity and the red/green quotient being the most significant. In coals of the Illinois Basin, one or more forms of fluorinite, resinite, sporinite and cutinite can be distinguished.

Temperature-programmed combustion studies of coal and maceral group concentrates

Abstract Temperature-programmed combustion profiles of coals and their maceral group concentrates were obtained by thermogravimetric analysis in air at a heating rate of 15 K min −1 . The maceral group concentrates were prepared by density separation of demineralized, micronized coal samples. Particle size had a significant effect on combustion profiles, with increased complexity in terms of the number of peaks observed for micronized coal compared with larger size fractions. Analysis of the combustion profiles of macerals and reconstructed whole coals indicated that in some cases maceral interactions can occur, especially in the presence of liptinite. It was also found that the reactivity of a coal cannot be predicted from the reactivities of its maceral components.

Activated carbon produced from an Illinois Basin coal

Abstract Activated carbons were produced from an Illinois Basin bituminous coal (IBC-106) by a three-step process: oxidation of the coal in air at 150–250 °C for 2–40 hours, devolatilization of these oxidized coals in nitrogen at 500–730 °C for 1 hour and activation (gasification) of the chars in 45% steam, 4% oxygen in nitrogen at 730–880 °C for 3.5–96 hours. Products were characterized in terms of CO 2 single-point BET surface area, helium and bulk densities, pore volume and toluene adsorption capacity. Seven of the nine carbons produced had surface areas exceeding 1000 m 2 g −1 (dry). It was confirmed that the application of oxidation pretreatment eliminates the caking of IBC-106, preserves the coals microstructure, and leads to high carbon surface areas. In comparison with Darco coconut charcoal, a commercial activated carbon (Fisher Scientific) whose surface area was 547 m 2 g −1 (dry), the largest toluene adsorption capacity of activated carbons was 1.57 g g −1 , four times more than that of Darco. Production costing analysis on a laboratory scale suggested that, in a single production run, the most cost-effective final product is not the activated carbon with maximum surface area but the carbon produced at the lowest cost for each square meter of pore surface area.