M.Phil. (Energy Studies) / Please refer to full text to view abstract

This study was carried out on the main coal-producing and the extensively block-faulted area of Mchenga Coal Mine, southeast of the 90 km2 intracratonic Livingstonia Coalfield in the north of Malawi. It was initiated against the background of indistinct information on coal geology, shortage of energy and potential environmental threats due to mine activities. The study aimed at integrating investigations of characterization of the lithostratigraphy, coal seam correlation, coal quality determination, examination of the mineralogy and geochemistry of coal and hosts rocks, assessment of water quality and providing information for mining and potential environmental and water quality impact assessment in the study area. The methodologies used in this study include literature review, field visits, mapping, sites selection and characterization, borehole logging, geochemical analyses, data processing and interpretation. The geochemical analyses include proximity analysis of coal quality, microscopy and X-ray Diffraction for mineralogy and petrology, X-ray Fluorescence (XRF) for rock geochemistry and Atomic Absorption Spectrometry for determination water geochemistry. The results have shown that a) The Coal Measures comprises of four to six coal seams in different localities, and the occurrence is flat and gently dipping southeast and are correlated. Thicknesses of the coal seams vary from 0.10m to 3.0m with some notable lateral and horizontal variations. Thick and workable seams occupy the lower portion of the Coal Measures and are exposed along the North Rumphi River bank; b) Coal quality belongs to sub-bituminous ‘A’ to ‘C’ on ASTM classification (1991), being characterised by low moisture content (0.8 to 1.3 wt percent) and sulphur content (0.49 to 0.85 wt percent), high ash content (9.0 to 17 wt percent) and volatile matter (24 to 32.9 wt percent), fixed carbon (53.6 to 62.6 wt percent), calorific value (7,015 to 7,670 kcal/kg); c) Mineral matters constitute approximately 9.55 to 38.34 wt percent of the coal samples, predominantly clays (interstratified illite/smectite and kaolinite) with varying proportions of quartz, mica and feldspars, as well as minor calcite and pyrite and their geochemistry, being characterised by enrichment of SiO2 from 5.37 to 20.56 wt percent, Al2O3 (2.63 to 11.21 wt percent) and K2O (0.32 to 3.65 wt percent) with trace concentrations of CaO (0.04 to 0.41 wt. percent), MgO (0.08 to 0.65 wt percent) and P2O5 (0.018 to 0.037 wt percent) and Na2O concentration notably below 0.01 wt percent; d) Calcite and pyrite constitute minor concentration in both sandstones and shales; e) Water quality in the area is characterised as two groups of acidic (pH 3.3-6.4) and near-neutral to slightly alkaline (pH 6.9-7.3) and low pH, high TDS, SO42- and EC are noted at the coal crusher plant which points out to high leaching of trace elements such as Pb and Fe. Na++K+ are dominant in upper sections of North Rumphi and Mhlepa Rivers. Ca2+ cations are dominant at crusher plant, underground mine and lower section of Mhlepa; f) Based on the geochemistry analysis, Na and trace elements such as Ti, V, Mn, Fe, Zn, Rb, Sr and Zr from coal and host rocks have the ability to contribute significantly to deterioration in the ground and surface water quality in the study area. It can be concluded that the coals of the Livingstonia Coalfield belong to Gondwana group deposited in sub-basin with multiple seams embedded in sandstone and shale host rocks.

The Bowen Basin is one of the most intensely explored sedimentary basins in Australia and hosts one of the world’s largest coking coal deposits. This study focuses on the Lenton deposit in the north-central part of the Bowen Basin and targets the Rangal Coal Measures, which are the youngest (245 Ma), most areally extensive and least structurally deformed coal measures in the study area. Six lithofacies were identified from detailed bed-by-bed logging of two cores and stratigraphically-upward comprise peatmire deposits of the Permian Blackwater Group overlain unconformably by braided fluvial strata of the Triassic Rewan Group. Coal-bearing strata of the Blackwater Group form a large-scale drying up sequence showing a change from permanent to seasonal waterlogged conditions related to the onset of regional uplift. Sedimentation was then terminated and a regional erosion surface formed by uplift related to the Hunter Bowen Orogeny. This, then, was overlain by braided fluvial strata of the Triassic Rewan Group.

A new process is being developed to produce graphite from prime coking coal. Coal is dissolved in dimethylformamide (DMF), on addition of sodium hydroxide. The minerals and undissolved coal are separated by centrifugation and filtration to give a solution (referred to as Refcoal solution or RCS). Over 90 wt % of the organic part of a flotation product, from the Tshikondeni mine, can be dissolved at temperatures ranging from room temperature to 135°C. The purified coal (referred to as Refcoal) and DMF need to be separated. the Refcoal to be coked and the DMF to be purified and recycled. This process should be as efficient as possible, whilst both products should be low in water content to minimise drying costs. The addition of water to the Refcoal solution causes precipitation to take place, forming a gel (referred to as Refcoal gel) liquid system. This mixture can be either centrifuged or filtered to give a denser gel, containing water, DMF and coal solids, and supernatant or filtrate, containing water and DMF. Different techniques and processes can be used to improve the separation of the DMF from the Refcoal by achieving a denser Refcoal gel: • Longer centrifugation times improve the density and therefore the separation, but this technique has its limits. • The use of low-temperature water improves the separation. • The use of syneresis could improve separation at a lower cost: heated standing tanks are used to expel the supernatant and therefore increase the density of the gel, thereby decreasing the required number of washing stages. • The addition of toluene at the beginning of a wash improved the removal of DMF by 20%, using centrifugation as separation method. • Pressure filtration gave a 20% improvement on centrifugation, with no additives. • The addition of toluene to the pressure filtration process gave another improvement of 15%, and after three stages the percentage of solids in the gel was 28%, the highest so far achieved. This method also resulted in the highest removal of DMF in the first stage (73% of the original DMF in the RCS was removed). Counter-current washing shows the greatest potential, using the least amount of water. The concentration of DMF in the wash solution, to gel the Refcoal solution, is a limitation of this process. If the concentration is too high, no gelling and therefore no separation can take place in the first stage. It is recommended that counter-current washing using pressure filtration should be investigated; however, this will be difficult on a laboratory scale due to the mass losses during transfers. / Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2009. / Chemical Engineering / unrestricted

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Coal is likely to remain an important energy source for the next several hundred years and hence advances in coal combustion technologies have major practical impact. Detonation combustion of coal initiated by a plasma cartridge driven detonation wave holds promise for improving both system and combustion efficiencies. Both fragmentation and chemical kinetic pathways are qualitatively different in comparison to conventional coal combustion. The present work is a theoretical investigation of fragmentation due to detonation wave. The theoretical simulation starts with simple model and progressively incorporates more realistic analysis such as combined convective and radiative boundary condition. It studies the passing of detonation wave on coal particles suspended in air. Concepts of solid mechanics are used in analysing fragmentation of coal particles. A numerical model is developed which includes stress developed due to both thermal and volatilization effects. Weibull statistical analysis is used to predict the fracture time and fracture location resulting from principal stress induced. It is observed that coal particles fragment within microseconds. Radiation does not have much effect on developed stress. Volatilization does not have much effect on fragmentation for the particle size considered in this work and stress due to thermal effect dominated the fragmentation. Coal size distribution statistics is considered to obtain real regime. Coal is used as mixture of different sized particles in real combustors. Hence it is important to analyse the effect of detonation wave on mixture of coal particles. Results presented in this work from simulation run suggest that plasma assisted detonation initiated technology can fragment coal particles faster. Average fracture time of mixture of coal particles is far less than detonation travel time for the detonation tube considered here. Simulation results suggest that almost 90% of coal particles fragment early. Average fracture time reduces as Mach number increases. Same phenomena can be observed for volatile matter generated at fracture and ow of volatile matter at fracture. Hence it can be concluded that plasma assisted detonation combustion leads to different volatilization and fragmentation pathways.

MESMEG / Department of Mining and Environmental Geology / The Mushithe coal occurrence is situated approximately 16 km west of the Tshikondeni coal mine in the Tshipise-Pafuri sub-basin of the Soutpansberg coalfield in South Africa. The Soutpansberg Coalfield has received comparatively less attention compared to other more notable South African coalfields. There is as a consequence very limited information in the public domain applicable to the geology as well as quality of coal in this coalfield, as a result there is no known study focused exclusively on the Mushithe coal occurrence. The aim of the study was to conduct detailed geological mapping of the Mushithe Deposit so as to ascertain the geological environment and petrological characteristics of rocks within the area. Further work involved coal sampling and analysis in order to establish coal quality and its physical and chemical characteristics. Samples were collected using geological field mapping and channel sampling. Nine coal samples were collected from the coalbed and host rock, exposed along the Mbodi River, during geological field mapping using channel sampling. Furthermore, 92 rock samples were collected during geological field mapping of which 10 representative samples were selected for further analysis. X-ray fluorescence spectrometry was conducted on all selected samples. Proximate analysis and ultimate analyses, and calorimetry tests were undertaken on coal samples. Three samples were selected based on calorific value for maceral identification, mineral analyses and vitrinite reflectance using petrographic study. Detailed geological mapping of the area around the Mushithe coal occurrence showed the geological setting of coal in this area. The following lithologies were identified in the study area: sandstone, mudstone, ironstone, calcrete, shale, quartzite, quartz vein with a general strike direction to the north-east. The host rocks including coal were intruded by dolerite dykes and this resulted in the devolatilization of coal. The current study concluded that the Mushithe coal was formed in a wet swampy environment. This has been confirmed based on tissue preservation index (1.69) and gelification index (2.35). Coal rank ranged from bituminous Rank C- B according to United Nations Economic Commission for Europe Coal Classification (UNECE) and samples were characterised by high ash (27.90%), high moisture (10.47%) and low sulphur (0.24%). Furthermore, coal was graded below grade D based on classification for use by ESKOM which consider any calorific value below 24.5 MJ/kg to be in this category. The coal is vitrinite rich (77.75 vol%) and low in Inertinite (22.25 vol%) and devoid of Liptinite and pseudovitrinite, thus it is of good coking quality. Geochemical analysis revealed that the coal was enriched in TiO2 and Fe2O3 which was corroborated by the mineral matter which was mostly clay and pyrite. Comparatively, coal quality analysis revealed the calorific value of 14.26 MJ/kg and vitrinite reflectance between 0.94 %ROV to 1 %ROV which was less than that of the Tshikondeni Deposit but greater than that at Waterberg coalfield. The study recommends further detailed exploration of coal in the area, applying such techniques such as geophysical exploration and borehole drilling leading to resource evaluation. Further studies are recommended to provide a better interpretation of the depositional environment of coal at Mushithe as well as the effect of devolatilaziton by a dolerite dyke. / NRF

This thesis presents details of investigations into the potential for co-disposal of the two rejects from Clarence Colliery and Kable's Transport Sand Mine. Column experiments were undertaken to simulate field conditions. The experiment consisted of: 1/. creating the required co-disposal arrangement and structure in containers 2/. infiltrating water through each container and measuring the rates of infiltration and overflow 3/. measuring the chemical properties of the leachate water. Geotechnical tests of co-disposal pile stability were undertaken using a specially constructed shear box. Results of this study suggest the co-disposal of course coal washery reject from Clarence Colliery with clay tailings from Kable's Transport Sand Mine is a feasible option for managing the generation of acetic drainage. It is recommended that field trials comprise layers of coal reject and clay tailings in a 9:1 ratio. Layering the coal reject with clay tailings creates a semi-permeable barrier which acts to restrict water percolation through the reject as well as reacting with the leachate to increase the leachate pH and adsorb metals / Master of Engineering (Hons)

M. Tech. Mechanical Engineering. / Discusses the economiser design to absorb as much heat as possible within the flue gases. Fly ash particles, a product of combustion, entrained in the flue gas of the furnace part of the boiler in coal fired boilers, affect economiser thermal performance by causing erosive wear and scale on the outer surface of the economiser tubes along the flow path, which in turn increases the thermal resistance characterisation of coals in relation to combustion behaviour traditionally relies on staged quenching of the reaction and subsequent gravimetric analysis of the remaining sample. Three typical steam-raising coals are compared with regard to reactivity and broadly examined relative to their petro-graphic constituents and other standard laboratory tested samples. A significant correlation was found between the ignition temperature and the hydrogen or carbon ratio determined by the ultimate analysis, inter alia, the erosion rate and the heat transfer rate.

Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / The middle eocene to early oligocene Bowmans and Lochiel coal deposits of the northern St. Vincent Basin, South Australia have been studied to elucidate their depositional environments. These coals occur within predominantly fluvio-lacustrine transgressive system tract sequences that formed during the initial phase of basin infill. The aforementioned facies are unevenly distributed and their stratigraphic succession highlights evolutionary changes in local palaeoenvironments. Within individual seams the transition from subaquatic to topogenous forest swamps and ultimately ombrogenous conditions is most common. However, over the coal sequence as a whole, conditions evolved from exclusively terrestrial through mixed terrestrial and subaquatic to open water. Also detected were multiple rapid reversals of the water table, especially higher in the sequence, and cyclic patterns reflecting a brief basal subaquatic phase prior to the onset of sustained terrestrial conditions. These patterns suggest a fluctuating, although progressively rising, water table and a balance between accommodation and accumulation. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1280880 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007