A technical and economic evaluation of a passive underground mine-water purification system (PUMPS): a geothermally powered geo-engineering system designed for in-situ bio-remediation of acid mine water
- Ntholi, Thakane Thato Prudence
- Authors: Ntholi, Thakane Thato Prudence
- Date: 2017
- Subjects: Water -- Purification -- South Africa Water -- Purification -- Biological treatment , Mine water -- South Africa -- Evaluation Acid mine drainage -- South Africa Environmental geochemistry -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/19586 , vital:28900
- Description: PUMPS mimics natural geothermal vents as a conceptual model designed for the remediation of acid mine water (AMW) in voids of abandoned gold mines of the Witwatersrand Basin in South Africa. In this system, a reaction chamber containing Desulfotomaculum kuznetsovii sulfate reducing bacteria will be set at the bottom of a 3-4 km deep mine that will be flooded. A geothermal system with at least one (1) doublet will be drilled from the bottom of the mine to the depth of 8km, where the temperatures are sufficient for geothermal energy harvesting. AMW, used as a geothermal fluid, will be pumped down the injection well and circulate through hot rock. The hot water is then used to generate electricity and then channelled into the reaction chamber to undergo bio-remediation. Following treatment, the water flows back into the mine voids where it will improve the quality of untreated AMW through dilution. Eventually, the mine will be flooded with clean water that can be stored underground and/or pumped up to surface for social and ecosystem services. Following an introduction and proof of concept for the PUMPS, the research builds further on the technical and economic evaluation of the PUMPS in order to assert its viability and sustainability. The technical viability includes testing the ability for Desulfotomaculum kuznetsovii to survive in high pressure condition; quantifying the amount of energy that can be drawn from the geothermal reservoir; determining the placement and scheme of the geothermal wells; and, finally, developing a robust economic model of the system. Experiments show that Desulfotomaculum Kuznetsovii can tolerate high pressure conditions in of at least 100bar at their ideal sulfate reducing temperature of 63°C. Geochemical modelling shows that AMW can be used effectively as a geothermal fluid for PUMPS. To achieve highest efficiency and minimal fluid loss, the geothermal wells should be placed along the SSE-NNW direction, based on the known stress field across the Witwatersrand Basin. With a flow rate of 30l/s the energy drawn from the geothermal reservoir is sufficient to drive PUMPS and the surplus energy is determined by the volume of AMW treated per day. All results indicate that the PUMPS is technically and economically viable. The economic model shows that the value and viability of the PUMPS is best reflected with a comprehensive inclusion of potential revenue (for example from chemical solution mining of deep seated gold) and financial/environmental incentives.
- Full Text:
- Date Issued: 2017
- Authors: Ntholi, Thakane Thato Prudence
- Date: 2017
- Subjects: Water -- Purification -- South Africa Water -- Purification -- Biological treatment , Mine water -- South Africa -- Evaluation Acid mine drainage -- South Africa Environmental geochemistry -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/19586 , vital:28900
- Description: PUMPS mimics natural geothermal vents as a conceptual model designed for the remediation of acid mine water (AMW) in voids of abandoned gold mines of the Witwatersrand Basin in South Africa. In this system, a reaction chamber containing Desulfotomaculum kuznetsovii sulfate reducing bacteria will be set at the bottom of a 3-4 km deep mine that will be flooded. A geothermal system with at least one (1) doublet will be drilled from the bottom of the mine to the depth of 8km, where the temperatures are sufficient for geothermal energy harvesting. AMW, used as a geothermal fluid, will be pumped down the injection well and circulate through hot rock. The hot water is then used to generate electricity and then channelled into the reaction chamber to undergo bio-remediation. Following treatment, the water flows back into the mine voids where it will improve the quality of untreated AMW through dilution. Eventually, the mine will be flooded with clean water that can be stored underground and/or pumped up to surface for social and ecosystem services. Following an introduction and proof of concept for the PUMPS, the research builds further on the technical and economic evaluation of the PUMPS in order to assert its viability and sustainability. The technical viability includes testing the ability for Desulfotomaculum kuznetsovii to survive in high pressure condition; quantifying the amount of energy that can be drawn from the geothermal reservoir; determining the placement and scheme of the geothermal wells; and, finally, developing a robust economic model of the system. Experiments show that Desulfotomaculum Kuznetsovii can tolerate high pressure conditions in of at least 100bar at their ideal sulfate reducing temperature of 63°C. Geochemical modelling shows that AMW can be used effectively as a geothermal fluid for PUMPS. To achieve highest efficiency and minimal fluid loss, the geothermal wells should be placed along the SSE-NNW direction, based on the known stress field across the Witwatersrand Basin. With a flow rate of 30l/s the energy drawn from the geothermal reservoir is sufficient to drive PUMPS and the surplus energy is determined by the volume of AMW treated per day. All results indicate that the PUMPS is technically and economically viable. The economic model shows that the value and viability of the PUMPS is best reflected with a comprehensive inclusion of potential revenue (for example from chemical solution mining of deep seated gold) and financial/environmental incentives.
- Full Text:
- Date Issued: 2017
Modelling and control of combustion in a high velocity air flame (HVAF) thermal spraying process
- Authors: Barth, Dominic
- Date: 2010
- Subjects: Metal spraying , Combustion
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9644 , http://hdl.handle.net/10948/1266 , Metal spraying , Combustion
- Description: Thermal spraying is a technology, which is used for coating of components and structures in order to achieve certain tribological characteristics, or for protection against corrosion, excessive temperature and wear. Within thermal spray, there are processes, which utilise combustion of liquid fuel to obtain high velocities flows providing, therefore, good adhesion of coating materials to substrates. These include High Velocity Oxygen Flame (HVOF) and High Velocity Air Flame (HVAF) process, of which the former one is widely used as it has been developed for at least two decades, while HVAF is less common. However, some studies indicate that HVAF has a number of advantages over HVOF, including the economic benefits. The thermal spray gun, based on the HVAF process, has been developed before, but the system was controlled manually. Therefore, there is a need to develop a fully automated controller of an HVAF thermal spray system. Process control of thermal spraying is highly complex as it involves simultaneous control of a number of processes, including; ignition process, combustion process, spraying material melting, as well as control and monitoring of auxiliary equipment. This paper presents the development of a control system for an HVAF thermal spray system, based on a Microchip PIC microcontroller. The designed control system was applied for controlling of thermal spraying of carbides powders, and provided a reliable ignition and stable combustion process, powder feeding and all other functions of control.
- Full Text:
- Date Issued: 2010
- Authors: Barth, Dominic
- Date: 2010
- Subjects: Metal spraying , Combustion
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9644 , http://hdl.handle.net/10948/1266 , Metal spraying , Combustion
- Description: Thermal spraying is a technology, which is used for coating of components and structures in order to achieve certain tribological characteristics, or for protection against corrosion, excessive temperature and wear. Within thermal spray, there are processes, which utilise combustion of liquid fuel to obtain high velocities flows providing, therefore, good adhesion of coating materials to substrates. These include High Velocity Oxygen Flame (HVOF) and High Velocity Air Flame (HVAF) process, of which the former one is widely used as it has been developed for at least two decades, while HVAF is less common. However, some studies indicate that HVAF has a number of advantages over HVOF, including the economic benefits. The thermal spray gun, based on the HVAF process, has been developed before, but the system was controlled manually. Therefore, there is a need to develop a fully automated controller of an HVAF thermal spray system. Process control of thermal spraying is highly complex as it involves simultaneous control of a number of processes, including; ignition process, combustion process, spraying material melting, as well as control and monitoring of auxiliary equipment. This paper presents the development of a control system for an HVAF thermal spray system, based on a Microchip PIC microcontroller. The designed control system was applied for controlling of thermal spraying of carbides powders, and provided a reliable ignition and stable combustion process, powder feeding and all other functions of control.
- Full Text:
- Date Issued: 2010
Increasing competitiveness through the enhancement of logistics processes in the South African automotive industry
- Authors: Njokweni, Thobela
- Date: 2005
- Subjects: Business logistics , Automobile industry and trade -- South Africa , Competition, International
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10939 , http://hdl.handle.net/10948/418 , Business logistics , Automobile industry and trade -- South Africa , Competition, International
- Description: Logistics has become one of the automotive industry's most crucial sub-sectors. Previously, logistics had to step aside to make way for production considerations. Today it is regarded as being every bit as crucial as production in the global village. Advancement of logistics in South Africa is crucial because original equipment manufacturers are producing to developed world standards but are having to cope with low developing world logistics standards. The logistics processes that need to be enhanced in order for the South African automotive industry to be more competitive were investigated. To examine the main problem, three sub-problems were identified. The first sub-problem that has been identified dealt with logistics processes that will enhance the competitive advantage of the South African automotive industry. The second sub-problems looked at key logistics opportunities and threats to the environment in which South African motor manufactures trade. They were investigated by assessing the nature of the South African motor manufacturing industry. Finally, the third sub-problem investigated conclusions that can be arrived at concerning the appropriateness and strategic value of the analysis.
- Full Text:
- Date Issued: 2005
- Authors: Njokweni, Thobela
- Date: 2005
- Subjects: Business logistics , Automobile industry and trade -- South Africa , Competition, International
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10939 , http://hdl.handle.net/10948/418 , Business logistics , Automobile industry and trade -- South Africa , Competition, International
- Description: Logistics has become one of the automotive industry's most crucial sub-sectors. Previously, logistics had to step aside to make way for production considerations. Today it is regarded as being every bit as crucial as production in the global village. Advancement of logistics in South Africa is crucial because original equipment manufacturers are producing to developed world standards but are having to cope with low developing world logistics standards. The logistics processes that need to be enhanced in order for the South African automotive industry to be more competitive were investigated. To examine the main problem, three sub-problems were identified. The first sub-problem that has been identified dealt with logistics processes that will enhance the competitive advantage of the South African automotive industry. The second sub-problems looked at key logistics opportunities and threats to the environment in which South African motor manufactures trade. They were investigated by assessing the nature of the South African motor manufacturing industry. Finally, the third sub-problem investigated conclusions that can be arrived at concerning the appropriateness and strategic value of the analysis.
- Full Text:
- Date Issued: 2005
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