No description available.

Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009.

One of the major issues facing the coal industry today is the decline in economically recoverable reserves, especially in the Witbank 1 Mpumalanga region of South Africa. This necessitates a critical review of alternate coal sources. One such source was identified as previously discarded and currently arising coal fines. It is well known that great value lies within these fines, but that the high moisture content associated with fine coal leads to thermal inefficiencies, handling problems and increased transport cost. This study will investigate thermal drying as a feasible solution to effectively remove this moisture. During thermal drying coal is fed into a high temperature environment; this can influence the physical and mechanical properties of the coal. The effects include swelling, caking, cracking, loss of water, loss of volatiles, and many more. These effects are investigated by means of thennogravimetric analysis, scanning electron microscopy with a heating stage, proximate analysis and mercury intrusion. Coal samples with an average particle size of 500 um were selected for this study. It was found that: The rate of moisture loss up to temperatures between 150 and 200°C is at a maximum where after the rate declines up to temperatures between 350 and 450°C when primary devolatilisation initiates. No visual changes in the coal are observed up to temperatures between 350 and 450°C. A limited amount of volatiles evolve at a constant rate up to 250°C; this is not significant enough to decrease the calorific value of the coal. Porosity changes in the coal are observed from temperatures as low as 250°C. Thermal drying was found to be a feasible alternative to currently employed drying methods with 150°C selected as the optimal drying temperature. A thermal drying plant is proposed with recommendations for future work needed to realise such a plant. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2010

Silicosis and coal worker's pneumoconiosis are serious occupational respiratory diseases associated with the coal mining industry and the inhalation of respirable dusts that contain crystalline silica. Silica exposure is an occupational health priority even when exposure has ceased or is below the occupational exposure limit (0.1 mg/m3). The objective of this study was to determine the individual contributions of the underground coal mining tasks to the total amount of respirable dust and respirable silica dust concentrations found in this environment. The tasks that were identified were continuous miner (CM) cutting, construction, the transfer point, tipping and roof bolting. Respirable dust sampling was conducted at the intake and return of each task, as well as at the intake and return of the section and the intake airway to the section. The five occupations that perform these tasks were also sampled to determine the personal exposure levels. Respirable dust concentrations and small concentrations of respirable silica dust were found in the intake airway and intake of the section, indicating that the air that enters the section is already contaminated. The respirable dust-generating hierarchy of the individual tasks was: transfer point>CM right cutting> CM left cutting> CM face cutting> construction> roof bolting > tipping. For respirable silica dust the hierarchy was: CM left cutting> construction> transfer point> CM right cutting. CM face cutting, tipping and roof bolting generated concentrations of below quantifiable levels. The personal exposures also differed and the eM and stamler operators had the highest exposure to respirable dust (3.417 ± 0.862 mg/m3) and respirable silica dust (0.179 ± 0.388 mg/m3) concentrations, respectively. Recommendations have been included for lowering the respirable dust and silica dust concentrations that are generated and that the workers are exposed to underground. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2010.

Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009.

One of the major issues facing the coal industry today is the decline in economically recoverable reserves, especially in the Witbank 1 Mpumalanga region of South Africa. This necessitates a critical review of alternate coal sources. One such source was identified as previously discarded and currently arising coal fines. It is well known that great value lies within these fines, but that the high moisture content associated with fine coal leads to thermal inefficiencies, handling problems and increased transport cost. This study will investigate thermal drying as a feasible solution to effectively remove this moisture. During thermal drying coal is fed into a high temperature environment; this can influence the physical and mechanical properties of the coal. The effects include swelling, caking, cracking, loss of water, loss of volatiles, and many more. These effects are investigated by means of thennogravimetric analysis, scanning electron microscopy with a heating stage, proximate analysis and mercury intrusion. Coal samples with an average particle size of 500 um were selected for this study. It was found that: The rate of moisture loss up to temperatures between 150 and 200°C is at a maximum where after the rate declines up to temperatures between 350 and 450°C when primary devolatilisation initiates. No visual changes in the coal are observed up to temperatures between 350 and 450°C. A limited amount of volatiles evolve at a constant rate up to 250°C; this is not significant enough to decrease the calorific value of the coal. Porosity changes in the coal are observed from temperatures as low as 250°C. Thermal drying was found to be a feasible alternative to currently employed drying methods with 150°C selected as the optimal drying temperature. A thermal drying plant is proposed with recommendations for future work needed to realise such a plant. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2010

Silicosis and coal worker's pneumoconiosis are serious occupational respiratory diseases associated with the coal mining industry and the inhalation of respirable dusts that contain crystalline silica. Silica exposure is an occupational health priority even when exposure has ceased or is below the occupational exposure limit (0.1 mg/m3). The objective of this study was to determine the individual contributions of the underground coal mining tasks to the total amount of respirable dust and respirable silica dust concentrations found in this environment. The tasks that were identified were continuous miner (CM) cutting, construction, the transfer point, tipping and roof bolting. Respirable dust sampling was conducted at the intake and return of each task, as well as at the intake and return of the section and the intake airway to the section. The five occupations that perform these tasks were also sampled to determine the personal exposure levels. Respirable dust concentrations and small concentrations of respirable silica dust were found in the intake airway and intake of the section, indicating that the air that enters the section is already contaminated. The respirable dust-generating hierarchy of the individual tasks was: transfer point>CM right cutting> CM left cutting> CM face cutting> construction> roof bolting > tipping. For respirable silica dust the hierarchy was: CM left cutting> construction> transfer point> CM right cutting. CM face cutting, tipping and roof bolting generated concentrations of below quantifiable levels. The personal exposures also differed and the eM and stamler operators had the highest exposure to respirable dust (3.417 ± 0.862 mg/m3) and respirable silica dust (0.179 ± 0.388 mg/m3) concentrations, respectively. Recommendations have been included for lowering the respirable dust and silica dust concentrations that are generated and that the workers are exposed to underground. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2010.

The primary purpose of this study is concerned with providing improved understanding of both accounting and management systems through the use of case study based research. To provide this improved understanding, this research study is based upon several key assumptions which are also key conclusions. Firstly, that management and accounting systems and practices exist in organisation contexts. Secondly, that these systems and practices obtain their meaning, in part, from the organisation contexts in which they are situated. Thirdly, that accounting knowledge and management theory, to-date, has failed to provide adequate descriptions and prescriptions for the organisations. Fourthly, that the key problem in accounting knowledge and management theory which has prevented adequate understanding is to do with the ontological issues which underlies such knowledge. The contents of this study can be seen to be divided into three parts. The first outlines the nature of management accounting knowledge paying particular attention to the ontological and epistemological assumptions. Through analysis of these assumptions, the importance of understanding the complexity of social reality is introduced. A model of a 'temporal-spatial' reality is introduced and described. The conclusion from this part is that the main problem in understanding accounting practices is linked with the ontological issues and that a more complex subjective reality needs to be explored. Part two provides the description of the case-study utilised to understand accounting practices in an organisational context. Part three provides an analysis of the use of the management and accounting systems by providing an understanding of the social-reality of the dominant decision-makers within the case-study. The conclusion forthcoming from this study is four-fold and stated in paragraph one. However, these have major considerations to the development of accounting knowledge and require major shifts in the dominant methodology of accounting thought. ix.

No description available.

Albertan coal has been used to produce extracts as precursor for production of anode coke. Coal extractability was studied using digestion with Tetralin in a 500 ml reactor. Different operating conditions were tried and optimum conditions were chosen for runs with coal-derived solvents. Extracts from runs with coal-derived solvents and their hydrotreated versions were distilled and heat treated to produce pitches as coke precursors. Coking experiments were performed using a molten salt bath furnace. Coal, solvents, pitches and cokes were characterized to study the effects of process chemistry on coke anisotropy. Coke anisotropy was studied using image analysis of polarized light optical micrographs and x-ray diffraction. Aromaticity of the pitch was found to be the key parameter controlling coke anisotropy. Solvent was found to be the most important factor contributing to pitch aromaticity. Heat treated products of high aromaticity yield the highest coke conversion and anisotropy. / Chemical Engineering