This thesis presents the results of research into the potential of underground mining methods applicable to inclined thick seams (thickness greater than 3.5m, and seam dip of 15 - 35 degree) in the Quangninh coalfield, Vietnam. The primary objectives of this research are to investigate the most suitable underground methods applicable to inclined thick seams in the Quangninh coalfield and to improve understanding of the operational and geotechnical issues associated with the application of chosen methods in thick seams with steeply dipping conditions. From a risk and operational assessment, the Longwall Top Coal Caving (LTCC) method is considered most appropriate for inclined thick seams under the current mining conditions in Vietnam. The LTCC method offers great potential for the efficient extraction of thick seams by caving coal from the upper section during the mining of the lower section. This significantly reduces the development cost per tonne. Compared to High reach Single Pass Longwalling, the LTCC method offers a low extraction height, resulting in smaller and less expensive equipment and better face conditions. Results from this study identified that for extracting an inclined thick seam, the face retreating along the strike has better operational advantages and better cavability than the face retreating updip or downdip of the seam. The operational issues of the LTCC method when extracting inclined seams are: the stability of the support, transport in the mine, and the difficulties in roof control at the transition between face ends and the gateroads. In terms of geotechnical issues, better cavability of the top coal is anticipated for flat coal seams compared to inclined seams. In addition, the chain pillar for flat coal seams is subjected to a higher vertical stress distribution than that of inclined ones. An improved cavability assessment method for the categorisation of the cavability of the top coal with four categories, ranging from 1 (excellent cavability) to 4 (very poor cavability), was suggested to assist the feasibility and design stages of the LTCC application. The cavability assessment method was conducted by numerical analysis combined with back analysis from the database obtained from past LTCC practices.

Coal continues to be burned by direct combustion in packed or moving bed in small size domestic furnaces, medium size industrial furnaces, as well as small power stations. Recent stringent restrictions on exhaust emissions call for a better understanding of the process of combustion of coal in beds. The present study is a prelude to developing methods of analysis to obtain this improved understanding. A one-dimensional steady-state computational model for combustion of a bed of solid fuel particles with a counterflowing oxidant gas has been developed. Air, with or without preheating, is supplied at the bottom of the bed. Spherical solid fuel particles (composed of carbon and ash) are supplied at the top of the bed. Upon sufficient heating in their downward descent, the carbon in particles reacts with oxygen of the flowing gas. The governing equations of conservation of mass, energy, and species are integrated numerically to obtain the solid supply rate whose carbon content can be completely consumed by a given gas supply rate. The distributions of solid and gas temperatures, of concentrations of various gas species, of carbon content in solid, and of velocity and density of gas mixture are also calculated along the bed length. The dependence of these distributions on the solid and gas supply rates, the air supply temperature, the size of solid fuel particle, and the initial carbon content in solid is also investigated. The calculated distributions are compared with the available measurements from literature to find reasonable agreement. More gas supply is needed for complete combustion at higher solid supply rate. At a given gas supply rate, more solid fuel particles can be consumed at higher gas supply temperature, for larger particle size, and for lower initial carbon content in solid. The temperature of the bed becomes higher for higher solid supply rate, higher gas supply temperature, larger solid particle diameter, or lower initial carbon content in solid. These reasonable results lead one to encourage extension of the model presented here to more complex problems involving combustion of coals in beds including the effects of drying and pyrolysis. / Graduation date: 1994

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xiii, 82 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 65-66).

Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains iii, 240 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 221-232).

Thesis (M.S.)--Ohio University, August, 2009. / Title from PDF t.p. Includes bibliographical references.

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Coal balls are carbonate concretions formed in peat during the Pennsylvanian and early Permian. Microprobe and microscope analysis reveal that polycrystals of high-Mg calcite (HMC), which are also high in Sr, are the earliest calcium carbonate to form in the Williamson No. 3 coal balls from the Kalo formation in Iowa. This HMC has early diagenetic rims of ferroan and non-ferroan low-Mg calcite (LMC) suggesting diagenesis in meteoric water. The combination of HMC followed by LMC suggests the earliest coal ball carbonate formed in a hydrologically dynamic environment, where saltwater influx into the mire was followed by a return to meteoric pore water. Subsequent generations of carbonate are ferroan and non-ferroan LMC and appear to result from diagenesis of the original HMC fabric with LMC rims. HMC polycrystals from coal balls are among the first abiotic HMC to be reported from the mid-Pennsylvanian; coal balls may be a good source of Pennsylvanian HMC. Coal balls that formed in porous peat (i.e. wood and surficial leaf mats) commonly have abundant radiating arrays of HMC polycrystals. Coal balls that formed in matrix-rich, low porosity peats consist primarily of permineralizing anhedral calcite, which is ferroan LMC. The link between the HMC and porous permeable peat is supported by the distribution of HMC and ferroan LMC in plant cells. Wood cells, which have porous walls, are filled with HMC; fiber cells, which have impermeable walls, are filled with ferroan LMC. This study demonstrates a link between pore volume, porosity, plant cell type, and carbonate fabric.

Bibliography: leaves 322-335. / xxxvii, 343 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Highlights the need for extensive testing of large particle coal devolatilization models with both volatile matter evolution and particle temperature data in order to ensure that the predictions generated by the model can be thoroughly trusted. By undertaking an in-depth investigation into the particle temperature measurements and associated model predictions, shows that accurate model predictions can be obtained for the evolution of volatile matter, and of individual volatile species. The model is also capable of predicting the behaviour of wet coal particles by assuming that drying is heat transfer controlled and that the enthalpy of drying observed by Chen is applicable. Ultimately, this model forms a sound basis for the on-going development of a model encompassing all of the reactions required to model the behaviour of a typical coal particle in a fluidished bed combustor or gasifier. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1999