John H. Levy

Methane capacities of Bowen Basin coals related to coal properties

Abstract To help in assessing coalbed methane resources, methane adsorption capacities of Permian coals from the Bowen Basin of Queensland were investigated and related to other coal properties. Maximum methane capacities of moisture-equilibrated coals, normalized to a pressure of 5 MPa and 30°C, showed a continuously increasing (and reasonably linear) trend with increasing rank over the range 80–92 wt% total carbon. Such a linear trend was not observed for methane adsorption calculated on a dry basis. Methane adsorption capacity decreased with increasing temperature by ∼0.12 mL g−1K−1. Methane capacity also decreased as moisture content increased, by ∼4.2 mL g−1 coal for each 1 wt% increase in moisture. Coal surface area (CO2, Dubinin-Radushkevich) showed reasonable correspondence with methane capacity, although not precise enough to provide a reliable estimate of capacity. Comparison of Langmuir adsorption isotherms for nitrogen and carbon dioxide on Bowen Basin coals with the corresponding methane isotherms showed that, with a knowledge of the methane isotherm alone, nitrogen and carbon dioxide isotherms could be reliably constructed. Volumetric and gravimetric methane isotherms measured on the same coal were identical, confirming the accuracy of the procedures and calculations used.

The reaction of pyrite with water vapour

Abstract A thermogravimetric investigation of the reaction of pyrite with water vapour has been completed. The reaction occurs in two stages to produce magnetite via pyrrhotite, the effect of water vapour pressure being particularly pronounced in the second stage. The influence of particle size has also been studied, and X-ray diffraction, optical microscopy and scanning electron microscopy investigations were used to complement the thermogravimetric findings.

Siderite decomposition in retorting atmospheres

Abstract This work extends the characterization of siderites found in Tertiary Australian oil shales by investigating their decomposition in atmospheres resembling retorting conditions. The decomposition of mineral siderite samples and selected oil shale samples with high siderite contents, representing the four types of siderites most commonly found, were studied by thermogravimetry in controlled carbon dioxide-nitrogen-water vapour atmospheres. The decomposition temperature of each of the siderite types increased with increasing partial pressure of carbon dioxide, and decreased with increasing partial pressure of water vapour. Both effects were non-linear: larger temperature changes were observed at lower partial pressures. This study makes it possible to predict the amount of siderite decomposition under typical retorting conditions and the consequences for both the retorting and combustion stages during oil shale processing.

Kinetics of dehydroxylation, in nitrogen and water vapour, of kaolinite and smectite from Australian Tertiary oil shales☆

Abstract Dehydroxylation of kaolinite and smectite is significant in oil shale processing. The possibility of shifting these endothermic reactions from the retort to the combustor by increasing the water vapour pressure was confirmed and the kinetics of dehydroxylation was determined by thermogravimetry. For kaolinite, non-isothermal and isothermal dehydroxylation in dry N 2 was second-order, with activation energies of 163 and 208 kJ mol −1 and pre-exponential factors of 2.0 × 10 12 and 3.0 × 10 13 s −1 respectively. Increasing water vapour pressure markedly increased the dehydroxylation temperature. Isothermal data were fitted to a first-order model at water vapour pressures 5 kPa, but Arrhenius plots showed large changes in the kinetic parameters. Non-isothermal results increasingly deviated from second-order with increasing water vapour pressure, but this was successfully accounted for by the Altorfer model. For Rundle smectite, non-isothermal kinetic data for dehydroxylation in dry N 2 were best fitted by the Ginstling-Brounshtein diffusion model, with an activation energy of 83 kJ mol −1 and a pre-exponential factor of 1.0 × 10 7 min −1 .

Mineral reactions in the processing of Australian Tertiary oil shales

Abstract Mineralogical, mineral characterization and thermogravimetric studies were made of raw and processed shale samples from the most prospective sections of the Rundle, Stuart, Condor, Duaringa, Nagoorin South, Nagoorin, Yaamba and Lowmead oil shale deposits. The effects of processing on minerals were determined in sufficient detail to establish the relevance of the various minerals and their reactions in oil shale processing. Minerals identified as the most significant in processing were smectite, kaolinite, siderite-type minerals and pyrite. Smectite and siderite-type minerals are characteristic of the oil shales of eastern Queensland. Smectites were found to be comparable in the various deposits and to be members of the montmorillonite/nontronite series with unusually low thermal stability. Four types of siderite (siderite, manganoan siderite, magnesian siderite and high magnesian siderite) were found, with progressively increasing decomposition temperatures in the retort. The most important mineral reactions occurring in the preheater, retort and combustor have been identified. Endothermic dehydroxylation and decomposition reactions of smectite, kaolinite, siderite minerals and pyrite influence heat requirements and gaseous products from retorting and combustion. The results indicate the possibility of transferring some of these reactions from the retort to the combustor by control of partial pressures of vapour phases in the retort. A sound basis has been established for future studies of the effects of specific minerals on oil coking reactivity and oil yields in retorting.

Vapour phase cracking and coking of three Australian shale oils: kinetics in the presence and absence of shale ash☆

Abstract The vapour phase thermal behaviour of shale oil samples derived from the Condor, Nagoorin carbonaceous and Stuart deposits was examined. Oils vaporized in argon were passed through packed beds of sand, or the spent shale ash corresponding to the particular oil, at temperatures between 500 and 600 °C, over a range of residence times. Results obtained over sand were attributable to thermal cracking. The oils behaved similarly; cracking was minimal at 500 °C at a 10 s residence time but increased as conditions became harsher. Small differences arose from the different oil compositions. Coke formation was small, compared to cracked gas production. When oil vapours were passed over spent shale ash, they again behaved similarly, but their behaviour was quite different from that over sand. Coking was prevalent at all temperatures studied and resulted in major oil losses, even at 500 °C.

Oxidative profiles of some australian oil shales by thermal analysis and infrared spectroscopy

Abstract Thermogravimetric and derivative thermogravimetric oxidative profiles were obtained for a number of Australian oil shales and kerogen concentrates heated in a dynamic air atmosphere. Evolved gas analysis curves and the associated first derivative curves were obtained for these materials by following the increase in optical absorption of the principal IR bands of gaseous species evolved during linear heating. Thermochemical changes in kerogens were also studied by means of solid-state IR transmission spectroscopy. Combustion of kerogen occurs in two stages, indicated by two sharply defined DTG peaks. The first stage involves complete or almost complete combustion of aliphatic components to give a char containing aromatic moieties. Evolved gas analysis and derivative evolved gas analysis curves for sulfur dioxide evolution, used in association with TG—DTG data, provide a means of characterising oil shale in terms of sulfur distribution.

Heat capacities and enthalpies for some Australian oil shales from non-isothermal modulated DSC

The application of thermal analysis to Australian oil shales has been quite common, however, the results have been somewhat limited by experimental technique and advances in thermal analysis instrumentation. In this paper we present a novel approach to the thermal characterisation of Australian oil shale. This approach involves separation of the unique components of oil shale, the kerogen (organic component) and the clay minerals (inorganic components), using chemical and physical techniques. The heat capacity and enthalpy changes for the kerogen and clay minerals were measured using non-isothermal modulated DSC from 25 to 500°C. Heat capacity data was obtained over a temperature range spanning several hundred degrees in a single experiment. Heat capacity was also estimated by incorporating TG data during regions where thermal reactions involving mass loss occurred. Enthalpy data for dehydration and pyrolysis of kerogen were also determined.

RELEVANCE OF CARBONATE MINERALS IN THE PROCESSING OF AUSTRALIAN TERTIARY OIL SHALES

Abstract The Tertiary oil shale deposits of eastern Queensland, Australia, comprise an important future source of alternative liquid fuels. Carbonate minerals are important in relation to selection of processing conditions and in limiting sulphur dioxide emissions. This paper characterizes such minerals from the Stuart, Rundle, Condor, Nagoorin, Nagoorin South, Duaringa, Yaamba and Lowmead deposits. Composite and stratigraphically selected samples were mineralogically analysed using chemical analyses, X-ray diffractometry, thermogravimetry and scanning electron microprobe analysis. Carbonate minerals significant in processing include calcite, magnesian calcite, siderite and magnesian, calcian and manganoan siderites which occur in different amounts in the various deposits. Dolomite and ferroan dolomite were sporadically observed. Calcite and magnesian calcite are decomposed in the combustor and reduce sulphur dioxide emissions by reaction to form CaSO 4 in the combusted solids. Siderite type minerals are fully or partially decomposed depending upon siderite type and process conditions in the retort. The iron oxides produced react with hydrogen sulphide in the retort gases. Calcium replacing iron in the siderite also reacts with sulphur dioxide to form CaSO 4 and hence limits sulphur dioxide emissions from the combustor.

The non-isothermal reaction kinetics of pyrite with water vapour

Abstract The reaction of pyrite with water vapour, at pressures ranging from 10 to 80 kPa, has been studied under non-isothermal conditions. Numerical methods were used to abstract kinetic parameters from the differential rate equations representing kinetic models of the thermogravimetric (TG) data. The first and major stage of mass loss proceeds by reaction of water with pyrite to form a porous layer of pyrrhotite around a contracting pyrite core. A topochemically controlled, contracting volume reaction model gives an excellent fit to the TG data and is confirmed by microscopic studies. The second stage consists of oxidation of the pyrrhotite to magnetite and is best described by a reaction model based on three-dimensional diffusion control.