Australian Coals Research Articles

Geological controls on coalbed methane reservoir capacity and gas content

The influence of coal composition and rank on coalbed methane reservoir capacity, gas content and gas saturation have been investigated for a series of Australian, Canadian and United States coals. Globally there is no or little correlation between coal rank and methane adsorption capacity (as commonly assumed), although in particular basins there are general trends with rank and composition. Micropore 1 Micropores are less than 2 nm in diameter, mesopores 2 to 50 nm in diameter and macropores greater than 50 nm in diameter following current IUPAC classification [International Union of Pure and Applied Chemistry (IUPAC), 1994. Pure Applied Chemistry, 66, 1739]. 1 capacity and surface area, determined from low-pressure carbon dioxide adsorption isotherms (0°C) decrease and then increase with rank, passing through a minimum in the high volatile bituminous coal rank. There is no consistent variation in modal micropore size or size distribution with rank. For suites of isorank coals there is a poor (Permian Bulli and Wongawilli seams, Australia) to good positive correlation (Gates Formation coal seams, Lower Cretaceous, Canada) between vitrinite content and methane adsorption capacity (dry ash free and as received bases). For each isorank coal suite there is a good correlation between micropore capacity and abundance of vitrinite and high-pressure methane adsorption capacity. Comparison of coals of similar composition, but from different isorank suites, indicates however that the coals with the highest methane adsorption capacity do not necessarily have the highest micropore capacity. Such results are counterintuitive: most pore volume available for methane adsorption is generally assumed to be microporosity. It is suspected that moisture prevents methane from accessing (some?) microporosity or competes with methane for adsorption space. Carbon dioxide micropore capacity (which is performed on a dry basis) may thus not reflect the microporosity available for gas adsorption in moisture equilibrated coals. Alternatively because of differing physical and chemical properties of carbon dioxide and methane, apparent microporosity available to carbon dioxide (due to greater energy of adsorption) may not be available to methane. Total desorbed gas from canister analyses of Sydney Basin Australian coals suggests that most coals are under-saturated. For a small data set the degree of saturation is negatively correlated with permeability ( r=−0.78) suggesting preferential gas leakage from the higher permeability coals which are vitrite rich. Some degree of under-saturation is probably the result of increased reservoir capacity as a consequence of uplift of the coal seams and thus lower temperatures following gas generation. Rates of desorption are correlated with total gas content ( r=0.79) but do not correlate with rank or any compositional parameter.

Analytical variation in Australian coals related to coal type and rank

Analyses of Australian coals, ranging in age from Permian to Miocene, are reviewed principally by using the van Krevelen diagram (atomic O/C vs. H/C), but also by plotting calorific value vs. volatile matter. Groups of coals of particular ages or from particular areas or seams within coalfields plot in well-defined parts of the diagrams. Each group, however, covers only part of the rank range from lignite to semi-anthracite. Accordingly, the New Zealand (NZ) Coal Band, based on medium to high H/C Late Cretaceous and Cenozoic coals, is used as a reference maturation path. The extremes of H/C in low-rank Australian coals are shown by the particularly high H/C Jurassic Queensland coals and the low H/C Triassic Queensland (Callide) coals. The majority of coals plot between these extremes. These include Cenozoic Victorian lignites (brown coals) which, except for high H/C pale and light lithotypes, are similar to New Zealand lignites. Vitrains from Australian Permian coals plot across the width of the NZ Coal Band, and the range of Permian coals extends into much lower H/C parts of the van Krevelen diagram. The spectrum of all coals is continuous throughout the extensive range of H/C. Comparison with data on maceral group compositions shows close relations between H/C ratios and the proportion of vitrinite, provided allowance is made for the counteracting effects of high H/C liptinite and low H/C inertinite. In most coals, vitrinite is the dominant maceral group, and the range of H/C ratios of vitrain samples from Permian coals shows that vitrinite composition also must be significant in influencing the elemental composition of the heterogenous coal.

Trace Elements and Coal Preparation

The products and refuse streams from a number of Australian coal preparation plants were analysed for a comprehensive range of trace elements. Results are obtained for 61 elements from 9 plants. The distribution of the trace elements relative to the mass distribution is determined for each stream. This provided data on the potential partitioning of the elements during coal cleaning. As expected the levels of some elements were reduced by the coal preparation process as a result of their association with liberated mineral matter. The consistency of the level of removal was found to be high for some metals including titanium, vanadium and copper while others were highly variable typified by chromium, manganese, zinc and arsenic. Eighty-seven samples of product thermal coals were analysed for the same 61 trace elements. The distributions of the trace elements in these coals were investigated and it was found that, for many of them, the frequency distribution could be described by a Gamma distribution. Since the mineral matter in these coals would be expected to predominantly arise from secondary mineralisation, this distribution suggests that the presence of trace elements is as a result of a probablistic process.

Occurrence and distribution of organic sulphur in macerals of Australian coals using electron microprobe techniques

The organic sulphur content of the individual macerals in Permian high volatile bituminous coals from the Gunnedah Basin of New South Wales, has been studied using an electron microprobe technique. Liptinite (chiefly sporinite) in the coal has the highest organic sulphur content and inertinite (mainly semifusinite) the lowest; the vitrinite macerals have intermediate sulphur contents. These variations are responsible for the relatively low overall organic sulphur in inertinite-rich coals, typical of Australian Permian deposits. Neither marine influence on coal formation nor increases in coal rank appear to be associated with significant changes in organic sulphur of the individual macerals concerned.

98/03360 Evaluation and control of employee exposure to diesel particulate at several Australian coal mines: Pratt, S. L. et al. Appl. Occup. Environ. Hyg., 1997, 12, (12), 1032–1037

98/03360 Evaluation and control of employee exposure to diesel particulate at several Australian coal mines: Pratt, S. L. et al. Appl. Occup. Environ. Hyg., 1997, 12, (12), 1032–1037

98/02425 Evaluation and control of employee exposure to diesel particulate at several Australian coal mines : Pratt, S. L. et al. Appl. Occup. Environ. Hyg., 1997, 12, (12), 1032–1037

98/02425 Evaluation and control of employee exposure to diesel particulate at several Australian coal mines : Pratt, S. L. et al. Appl. Occup. Environ. Hyg., 1997, 12, (12), 1032–1037

Trading practices in the coal market: Application of the theory of bilateral monopoly to the Australia–Japan coal trade

One of the better-known anomalies of the international coal trade is the wide disparity in delivered coal prices into major markets. This disparity is particularly noticeable in Japan, the largest market. In Australia, the largest supplier to Japan (and the world), the dominant theory explaining the significantly lower delivered price for Australian coal relative to other major supplying nations has been the `bilateral monopoly' theory. This postulates that an increased surplus available from the trade due to savings in freight costs because of proximity is shared between Japanese buyers and Australian sellers. This article examines the application of the theory made by Bowen and Gooday (1993)which shows a roughly equal distribution of the surplus from the trade in the period 1980–1990. This examination shows that major assumptions with respect to exogenously determined upper and lower prices within which bargaining between the parties occurs cannot be sustained. Small adjustments to the bargaining range produce results which show an unequal distribution of the surplus which consistently favours buyers over the period. The latter part of the article examines a series of trading practices and differences in the composition of capital which may explain the long-term differences in bargaining power between the parties.

Evaluation and Control of Employee Exposure to Diesel Particulate at Several Australian Coal Mines

Abstract Employee exposures to diesel particulate (DP) were measured under normal and abnormal mining operations at BHP Steel Collieries Tower Colliery and other underground coal mines in New South Wales coal fields. DP was measured using submicron samplers developed by the U.S. Bureau of Mines, and the results were verified using quantitative scanning electron microscopy. Personal monitoring (n = 480 full-shift samples) conducted at nine underground coal mines has indicated that the exposure of the work force ranges from less than 0.1 to 2.2 mg/m3 of DP, depending on job type and mining operation. Operations such as longwall moves and stonedusting, which generate elevated levels of dust, cause severe interference to submicron DP measurements. Based on previous knowledge that engine tune and condition affect the balance between gaseous and particulate emissions, five technologies for controlling DP were investigated in a combination of studies conducted in an above-ground simulated tunnel and in a special controlled section of underground mine roadway. Potential improvements were validated by application in standard coal mining operations at Tower Colliery. Tests conducted under controlled conditions indicate that, depending on fuel quality, levels of DP in return airways can be reduced by up to 50 percent, and in actual mining situations a reduction of 20 percent can be achieved in exposure of the work force by the use of low sulfur fuels. In addition, subjective responses from the work force indicate that exhaust emissions from low sulfur fuels provide lower irritation and a more pleasant aroma. The use of water-filled scrubber tanks reduces the level of DP emissions by 25 percent. In addition, it was found that the cleanliness of these tanks in general does not affect their scrubbing properties. Chemical decoking of engines resulted in a reduction of 20 percent in DP in return airways. However, the longterm benefits and cost effectiveness of this treatment in mining operations have yet to be established. A nonflammable, disposable dry exhaust filter constructed from synthetic organic fibers with an operational lifetime in excess of 20 hours was found to reduce DP exhaust emissions by 80 percent. Investigations have indicated that the use of increased ventilation to control DP levels does not follow a simple dilution factor, and in some instances compliance with current regulatory requirements may not produce the required reduced exposure levels. The results from single-component control strategies provide considerable reduction in exposure to DP. However, the most efficient and cost-effective control methodology is the use of a combination of individual systems modeled to operations conducted at each mine.

Investment practices in Australian coal: The practice and profit of quasi-integration in the Australia-Japan coal trade

The Australian coal industry has frequently been described as a perpetual case of ‘profitless prosperity’. Industry literature on the subject usually sources this problem to government charges on the industry and to labour costs. However, these alleged problems do not appear to have diminished the enthusiasm for new investment in the industry. This study argues that a more complete explanation must look at who is investing in the Australian coal industry, what the rationale for those investments is, how they are financed and what their specific profitability is. The particular examination made here is of the quasi-integration investment practices of Japanese trading, steel and power companies—easily the largest group of buyers in the international coal trade. The close co-operation between Japanese government and business in this strategic raw materials industry is documented, as are the methods of subsidised investment. An examination of the financial performance of these companies' Australian coal investments shows that the profitability of their investments is significantly below that of most other investors in Australian mining over a recent 5-year period. Taken together, there is significant support for the conclusion that a process of co-ordinated quasi-integration has taken place and that the principal aim of such investments has not been to make profits from coal-mining. These results should make other prospective investors reconsider the benefits of quasi-integration, and should also be a public policy issue for Australian governments seeking to encourage the development of ‘profitable prosperity’ in the Australian coal industry.

Reaction of methane with coal

The reactivities of Australian coals and one American coal with methane or methane-hydrogen mixtures, in the range 350–400°C and a range of pressures (6.0–8.3 MPa, cold) have been examined. The effects of aluminophosphates (AlPO) or zeolite catalysts, with and without exchanged metals, on reactivity have also been examined. Yields of dichloromethane extractable material are increased by using a methane rather than a nitrogen atmosphere and different catalysts assist dissolution to various extents. It appears that surface exchanged catalysts are effective, but incorporating metals during AlPO lattice formation is detrimental. Aluminium phosphate catalysts are unstable to water produced during coal conversion, but are still able to increase extraction yields. For the American coal, under methane-hydrogen and a copper exchanged zeolite, 51.5% conversion was obtained, with a product selectivity close to that obtained under hydrogen alone, and with only 2% hydrogen consumption. The conversion under methane-hydrogen was close to that obtained under hydrogen alone, while a linear dependence of conversion on proportion of methane would predict a 43% conversion under methane-hydrogen. This illustrates a synergistic effect of the methane-hydrogen atmosphere for coal liquefaction using this catalyst system.

Coal gasification characteristics in an internally circulating fluidized bed with draught tube

Australian coal was gasified at atmospheric pressure in an internally circulating fluidized bed (0.3 m i.d. × 2.7 m high) with a draught tube (0.1 m i.d. × 0.9 m high) and a gas separator over the draught tube. The effects of reaction temperature (780–900°C), oxygen/coal mass ratio (0.30–0.53), coal feed rate (5.3–12.1 kg h −1) and steam/coal mass ratio (0.30–0.81) on composition of product gas, carbon conversion, cold gas efficiency and gas yield and calorific value were determined. Low-CV gas in the draught tube region and medium-CV gas in the annulus region can be obtained. In the annulus region, the composition of the product gas (vol.%) is H 2 31.8–46.2, CO 18.8–25.6, CO 2 13.2–20.4 and CH 4 5.3–10.4, with a CV of 8.6–13.2 MJ m −3. In the draught tube region, the composition is H 2 8.3–19.7, CO 6.7–13.1, CO 2 18.9–35.3 and CH 4 1.9–4.4, with a CV of 3.3–5.9 MJ m −3.

97/03742 State of the fire, ignition and explosion of gases during active and passive fire extinguishing

Determining the feasibility of injecting CO2 into coal seams for enhanced coalbed methane (ECBM) recovery as well as providing long-term carbon sequestration is an active area of research. It is now well known that coal swells in the presence of water and gases, which in turn may affect its in-seam permeability. If the swelling of the coal matrix by each component can be quantified, it may be possible to make better predictions about the suitability of particular seams for ECBM and carbon sequestration. Despite numerous studies where coal swelling has been measured in gases or water, there is relatively little information relating to how swelling of coals by gases is affected by water.In this paper we report on the gas-induced swelling behaviour of four moist Australian coals. Blocks of coal, nominally 30 × 9 × 9 mm, were cut parallel and perpendicular to the bedding plane from larger lumps. Samples were moisture-equilibrated at 97% relative humidity before being exposed to CO2 or CH4 at pressures up to 16 MPa and a temperature of 55 °C. Swelling of each sample was measured directly using digital cameras to monitor the change in length of the block as a function of pressure.Results show that swelling was greater in CO2 than CH4, with lower rank coals swelling more than high rank material. The presence of moisture significantly reduced the amount of additional swelling by the gas compared to dry coals; however, the degree to which the swelling of the coals was affected by moisture depended on the rank of the coal. It was also found that, proportionally, CH4-induced swelling was more affected by the presence of moisture than CO2-induced swelling. Although moist coals swelled less in CO2 or CH4 than dry coals, if the swelling due to moisture is included, the total swelling is more than that induced by the corresponding gas in the dry coal.

97/02603 Solubilization of an Australian brown coal oxidized with hydrogen peroxide in conventionally used solvents at room temperature

97/02603 Solubilization of an Australian brown coal oxidized with hydrogen peroxide in conventionally used solvents at room temperature

97/03380 Surface characterization of mineral matter in an Australian bituminous coal (Whybrow seam, NSW) using X-ray photoelectron spectroscopy and laser ionization mass analysis

97/03380 Surface characterization of mineral matter in an Australian bituminous coal (Whybrow seam, NSW) using X-ray photoelectron spectroscopy and laser ionization mass analysis

Proton magnetic resonance thermal analysis in coal research: A users overview

Abstract An overview of the principles, capabilities, and applications of proton magnetic resonance thermal analysis (PMRTA) is given. Its range of possible applications is described and results from some recent studies are discussed. PMRTA enables the dynamic state of materials with significant hydrogen contents to be investigated during pyrolysis. This is a thermal analysis technique which uses pulsed proton NMR ‘broad line’ spectroscopy as the means of determining the behaviour of the sample under investigation. Samples are subjected to a controlled temperature programme either ramped at a fixed rate (up to 20°C min −1 ) from 40°C up to 600°C, or held at a fixed temperature within this range. 1 H NMR measurements are made at intervals throughout the temperature programme. These in-situ measurements allow the progress of thermal transformations to be determined. The solid echo signals obtained for a rigid lattice are representative of the entire hydrogen population of the sample and the peak echo is a measure of the total hydrogen content. Deviations from this situation during pyrolysis require corrections to be made. The hydrogen content can therefore be monitored semi-quantitatively in the residual sample throughout the temperature programme. Molecular properties affect the transverse relaxation signal so that the proportion and extent of hydrogen mobility can be determined. Thermoplastic events, material loss and interactions between materials can be detected and properties predicted using validated correlations with data from established methods of analysis. It may be applied to materials which contain a significant amount of H 2 and minimal moisture or magnetic material. The instrument was originally developed at CSIRO, Australia, for use in the investigation of coals and related materials. Correlations of PMRTA parameters with a range of coal properties were established with a suite of Australian coals. At CRE the correlations of PMRTA parameters with coal properties have been developed further with a suite of UK and international coals. Recent studies have included investigation of a range of coal behaviours including the non-additive swelling of some coal blends (an important property for coals fired on grate stokers), coal spitting (of importance for coals burned in top feed stokers and domestic coals), effects of microwaving on coal properties (a technique being investigated with a view to reducing coal sulphur contents), coal spontaneous heating (a coal behaviour which it is not currently possible to predict because of the large number of factors involved), coking properties (coal plasticity and fluidity are crucial properties for successful coke production and PMRTA is a useful tool for investigating these properties) and behaviours of coal maceral concentrates. These are described and potential future applications for the technique, suggested.

97/01596 Thermogravimetric analytical procedure for characterizing New Zealand and eastern Australian coals

97/01596 Thermogravimetric analytical procedure for characterizing New Zealand and eastern Australian coals

97/00051 Structural analysis of Australian and Indonesian brown coals

97/00051 Structural analysis of Australian and Indonesian brown coals

Application of the mono/multilayer and adsorption potential theories to coal methane adsorption isotherms at elevated temperature and pressure

Accurate estimates of gas-in-place and prediction of gas production from coal reservoirs require reasonable estimates of gas contents. Equations based on pore volume filling/potential theory provide a better fit than the Langmuir equation to both high-pressure (up to 10 MPa), high-temperature (> 1.5Tc) methane isotherm data, and low-pressure (< 0.127 MPa) carbon dioxide isotherm data for 13 Australian coals. The assumption of an energetically homogeneous surface as proposed by Langmuir theory is not true for coal. Application of potential theory to the methane-coal system results in temperature-invariant methane characteristic curves, obtained with the assumption of liquid molar volume of the adsorbate and extrapolated vapour pressures. Temperature-invariant characteristic curves are obtained for carbon dioxide, although further testing is required. The application of isotherms equations based upon pore volume filling/potential theory, in particular the Dubinin-Astakhov equation, have general validity in their application to high-pressure supercritical methane-coal systems as well as providing a better fit to isotherm data.

Comparative petrological analysis between the Permian coals of India and Western Australia: paleoenvironments and thermal history

Abstract Permian sequences preserved in Western Australian basins (Collie, Perth and Canning) and the Gondwana basins of India (Damodar, Son-Mahanadi, Pench-Kanhan and Godavari Valley) have similar stratigraphic succession, faunal and floral assemblages, coal types and rank, and structure. As for coal types, petrographic analyses of Indian coals indicate that vitrinite, liptinite, inertinite and mineral matter content ranges from 37 to 56%, 8 to 14%, 24 to 35% and 12 to 18%, respectively. Western Australian coals show contents of vitrinite, liptinite, inertinite and mineral matter ranging from 31 to 67%, 6 to 10%, 20 to 57% and 6 to 7%, respectively. As for rank of coal, in India, high rank coals (Rvmax = 0.70–1.67%) occur in the Damodar Valley Basin. In this basin vertical rank gradients are higher, and uplift and removal of cover has occurred to a greater extent than in the other Gondwana basins of India. Some coals from Pench-Kanhan Valley Basin (Rvmax = 0.72–1.02%) and Son Valley Basin (Rvmax = 0.70–1.10%) have high reflectance values. Coals from other Gondwana basins occur at shallow depths and are of sub-bituminous rank (Rvmax = 1%) compared to other coals in the basin. Thus, the type and rank of the Permian coals indicate a similar depositional and thermal histories for the basin studied in India and Western Australia. This is consistent with the view that India and Western Australia were in close proximity before the break up of Gondwanaland.

96/04598 A chemical characterization of maceral fractions from an Australian coking coal

96/04598 A chemical characterization of maceral fractions from an Australian coking coal