Life cycle assessment of a coal-fired old thermal power plant
- Authors: Mbohwa, Charles
- Date: 2013
- Subjects: Greenhouse gas reduction , Life cycle assessment , Thermal power plants - Environmental aspects , Environmental impact assessments
- Type: Article
- Identifier: uj:4870 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12546
- Description: This paper discusses a life cycle analysis of a thermal power plant to quantify environmental impacts of thermal power production at an old power plant. Coal is used in electricity generation worldwide and many power plants in developing countries are very old. Knowing the life cycle environmental impacts of such power plants is very important since they produce a lot of greenhouse gases. This paper develops life cycle inventories for an old power plant in Africa and identifies ways to minimize coal consumption for the same capacity of power output. A life cycle assessment (LCA) was done for the power plant. The emitted carbon dioxide, sulphur dioxide, nitrous oxides and solid waste have adverse effects on flora, fauna, water bodies and humans. A number of environmental metrics were obtained for the thermal power plant and these form the basis for future comparative and extended studies.
- Full Text:
- Authors: Mbohwa, Charles
- Date: 2013
- Subjects: Greenhouse gas reduction , Life cycle assessment , Thermal power plants - Environmental aspects , Environmental impact assessments
- Type: Article
- Identifier: uj:4870 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12546
- Description: This paper discusses a life cycle analysis of a thermal power plant to quantify environmental impacts of thermal power production at an old power plant. Coal is used in electricity generation worldwide and many power plants in developing countries are very old. Knowing the life cycle environmental impacts of such power plants is very important since they produce a lot of greenhouse gases. This paper develops life cycle inventories for an old power plant in Africa and identifies ways to minimize coal consumption for the same capacity of power output. A life cycle assessment (LCA) was done for the power plant. The emitted carbon dioxide, sulphur dioxide, nitrous oxides and solid waste have adverse effects on flora, fauna, water bodies and humans. A number of environmental metrics were obtained for the thermal power plant and these form the basis for future comparative and extended studies.
- Full Text:
Microstructural development during mechanical forming of steel sheets
- Akinlabi, Stephen A., Akinlabi, Esther Titilayo
- Authors: Akinlabi, Stephen A. , Akinlabi, Esther Titilayo
- Date: 2013
- Subjects: Microhardness , Metal forming , Steel - Deformation
- Type: Article
- Identifier: uj:4852 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12519
- Description: Metal forming is used synonymously with deformation, a process during which an object gets changed due to the applied force. These changes can either be reversible or irreversible depending on the type of material; size and geometry of the object and the magnitude of the applied force to the object. This paper reports the microstructural development after mechanical forming of steel sheet material by varying the applied loads. The microstructural evaluations showed that the applied loads employed caused an increase in the magnitude of the grain sizes in each loaded specimen. Furthermore, the increase in the grain size of the microstructure was observed to be directly proportional to the loads applied. In addition, the microhardness values of the cross sections investigated were found to increase with the applied loads. Hence, the grain size growth and the hardness were linearly dependent on the applied loads, and this implies that there is a correlation between the applied loads and the resulting microstructure of the material and the hardness of the material.
- Full Text:
- Authors: Akinlabi, Stephen A. , Akinlabi, Esther Titilayo
- Date: 2013
- Subjects: Microhardness , Metal forming , Steel - Deformation
- Type: Article
- Identifier: uj:4852 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12519
- Description: Metal forming is used synonymously with deformation, a process during which an object gets changed due to the applied force. These changes can either be reversible or irreversible depending on the type of material; size and geometry of the object and the magnitude of the applied force to the object. This paper reports the microstructural development after mechanical forming of steel sheet material by varying the applied loads. The microstructural evaluations showed that the applied loads employed caused an increase in the magnitude of the grain sizes in each loaded specimen. Furthermore, the increase in the grain size of the microstructure was observed to be directly proportional to the loads applied. In addition, the microhardness values of the cross sections investigated were found to increase with the applied loads. Hence, the grain size growth and the hardness were linearly dependent on the applied loads, and this implies that there is a correlation between the applied loads and the resulting microstructure of the material and the hardness of the material.
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Investigating performance management in postal systems
- Mokoena, Thabiso John, Mbohwa, Charles
- Authors: Mokoena, Thabiso John , Mbohwa, Charles
- Date: 2013
- Subjects: Performance management , Postal service - Performance
- Type: Article
- Identifier: uj:4886 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12600
- Description: This paper investigates and discusses the practices of performance management in postal organizations. The postal industry has in the past decade been faced with negative business performance where mail volumes have declined, customers lost to competition and revenue gradually declining. Including other factors, performance management has been identified as a significant question as to whether do challenges exist in the manner in which employees, resources and activities are connected to the overall achievement of goals and objectives set by postal systems and whether does performance management have an impact to the loss of business, customers and revenue. This study reveals that factors such leadership, organizational strategy, process and resource management should be regarded highly important and have a positive strong relationship towards effective performance management in postal systems.
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- Authors: Mokoena, Thabiso John , Mbohwa, Charles
- Date: 2013
- Subjects: Performance management , Postal service - Performance
- Type: Article
- Identifier: uj:4886 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12600
- Description: This paper investigates and discusses the practices of performance management in postal organizations. The postal industry has in the past decade been faced with negative business performance where mail volumes have declined, customers lost to competition and revenue gradually declining. Including other factors, performance management has been identified as a significant question as to whether do challenges exist in the manner in which employees, resources and activities are connected to the overall achievement of goals and objectives set by postal systems and whether does performance management have an impact to the loss of business, customers and revenue. This study reveals that factors such leadership, organizational strategy, process and resource management should be regarded highly important and have a positive strong relationship towards effective performance management in postal systems.
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Transportation demand analysis of coal from Hwange coal fields
- Mhlanga, Samson, Mbohwa, Charles, Pretorius, Jan H.C.
- Authors: Mhlanga, Samson , Mbohwa, Charles , Pretorius, Jan H.C.
- Date: 2013
- Subjects: Coal mining - Zimbabwe - Hwange , Coal transportation - Zimbabwe
- Type: Article
- Identifier: uj:4872 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12548
- Description: This paper seeks to provide a background to the coal and coke manufacturing industry in Zimbabwe after the economical melt down of 2007. It analyses the current situation in terms of coal and coke supply and to identify the factors that affect coal and coke transportation choices. Results of the survey of the coal and coke suppliers were tabulated and factors which affect transportation such as method of loading, payment plans, reliability and strategic alignment of the transporter were analysed. Model recommendations on a strategic supply chain management approach were given for the agricultural sector and for the manufacturing sector with the aim of reducing heavy loads on the road and minimizing emissions by trucks while still maintaining high productivity..
- Full Text:
- Authors: Mhlanga, Samson , Mbohwa, Charles , Pretorius, Jan H.C.
- Date: 2013
- Subjects: Coal mining - Zimbabwe - Hwange , Coal transportation - Zimbabwe
- Type: Article
- Identifier: uj:4872 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12548
- Description: This paper seeks to provide a background to the coal and coke manufacturing industry in Zimbabwe after the economical melt down of 2007. It analyses the current situation in terms of coal and coke supply and to identify the factors that affect coal and coke transportation choices. Results of the survey of the coal and coke suppliers were tabulated and factors which affect transportation such as method of loading, payment plans, reliability and strategic alignment of the transporter were analysed. Model recommendations on a strategic supply chain management approach were given for the agricultural sector and for the manufacturing sector with the aim of reducing heavy loads on the road and minimizing emissions by trucks while still maintaining high productivity..
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Technology selection of biogas digesters for OFMSW via multi-criteria decision analysis
- Kigozi, R., Aboyade, A. O., Muzenda, Edison
- Authors: Kigozi, R. , Aboyade, A. O. , Muzenda, Edison
- Date: 2014
- Subjects: Multi-criteria decision analysis , Municipal biowaste - South Africa , Biogas digesters
- Type: Article
- Identifier: uj:4788 , http://hdl.handle.net/10210/11971
- Description: Multi-criteria decision analysis (MCDA) techniques are becoming increasingly popular in decision making for technology selection because of their ability to capture the multi-dimensionality of technologies. Biogas typically refers to an odourless gas produced by anaerobic digestion of biomass using microorganisms. Its production can occur naturally in marshes and landfills or more commonly, in specifically designed plants called biogas digesters under controlled conditions. For techno-economic efficiency of a biodigester, several factors such as cost of plant are taken into consideration. This paper examines various available technologies for biogas digesters using defined selection criteria via MCDA and chooses the best alternatives at various scales of biogas production for a case study in South Africa with municipal biowaste as the target feedstock. 14 biogas plants were analysed in this study and the Puxin and Bio4gas digesters were the best alternatives for small and large scale biogas production respectively.
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- Authors: Kigozi, R. , Aboyade, A. O. , Muzenda, Edison
- Date: 2014
- Subjects: Multi-criteria decision analysis , Municipal biowaste - South Africa , Biogas digesters
- Type: Article
- Identifier: uj:4788 , http://hdl.handle.net/10210/11971
- Description: Multi-criteria decision analysis (MCDA) techniques are becoming increasingly popular in decision making for technology selection because of their ability to capture the multi-dimensionality of technologies. Biogas typically refers to an odourless gas produced by anaerobic digestion of biomass using microorganisms. Its production can occur naturally in marshes and landfills or more commonly, in specifically designed plants called biogas digesters under controlled conditions. For techno-economic efficiency of a biodigester, several factors such as cost of plant are taken into consideration. This paper examines various available technologies for biogas digesters using defined selection criteria via MCDA and chooses the best alternatives at various scales of biogas production for a case study in South Africa with municipal biowaste as the target feedstock. 14 biogas plants were analysed in this study and the Puxin and Bio4gas digesters were the best alternatives for small and large scale biogas production respectively.
- Full Text:
Reagent optimization across a UG2 plant
- Muzenda, Edison, Abdulkareem, Ambali S., Afolabi, Ayo S.
- Authors: Muzenda, Edison , Abdulkareem, Ambali S. , Afolabi, Ayo S.
- Date: 2013
- Subjects: Reagent optimization
- Type: Article
- Identifier: uj:4860 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12536
- Description: Reagent optimization is very important in the recovery of valuable metals from their ore via flotation. This is particularly important for large platinum operations where correct reagent regime and addition system can provide improvement opportunities in recovery and grade. Also reagent optimization can reduce reagent costs for the rougher, scavenger and cleaner flotation units. Reagents were optimized in the flotation of hot floats from the plant at laboratory scale. It was found that in order to save cost, the collector and depressant must be reduced in the roughers and cleaners respectively. This report presents results and some practical considerations that must be taken into account to optimise reagent usage.
- Full Text:
- Authors: Muzenda, Edison , Abdulkareem, Ambali S. , Afolabi, Ayo S.
- Date: 2013
- Subjects: Reagent optimization
- Type: Article
- Identifier: uj:4860 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12536
- Description: Reagent optimization is very important in the recovery of valuable metals from their ore via flotation. This is particularly important for large platinum operations where correct reagent regime and addition system can provide improvement opportunities in recovery and grade. Also reagent optimization can reduce reagent costs for the rougher, scavenger and cleaner flotation units. Reagents were optimized in the flotation of hot floats from the plant at laboratory scale. It was found that in order to save cost, the collector and depressant must be reduced in the roughers and cleaners respectively. This report presents results and some practical considerations that must be taken into account to optimise reagent usage.
- Full Text:
Energy management in the South African sugar industry
- Authors: Mbohwa, Charles
- Date: 2013
- Subjects: Sugar industry - South Africa , Energy management - South Africa
- Type: Article
- Identifier: uj:4887 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12601
- Description: The South African sugar industry produces sugar and electricity and raw materials for ethanol production among other by-products. The cogeneration of electricity in the sugar industry is linked to energy security and avoided greenhouse gas emissions. Electrical energy and thermal energy are the primary energy types used for sugar processing. This paper identifies energy management best practices necessary to increase the efficiency of the cogeneration processes. Adoption of energy conservation and efficiency measures is imperative for the sugar industry to generate electricity for own use and for export to the national grid. More energy efficient practices save money and reduce coal consumption. Equipment and technological improvements coupled with process design improvements necessary to improve factory energy efficiency are identified. The paper further discusses the bio-energy role and potential in the South African sugar industry with a view to inform decision making and advise government policies.
- Full Text:
- Authors: Mbohwa, Charles
- Date: 2013
- Subjects: Sugar industry - South Africa , Energy management - South Africa
- Type: Article
- Identifier: uj:4887 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12601
- Description: The South African sugar industry produces sugar and electricity and raw materials for ethanol production among other by-products. The cogeneration of electricity in the sugar industry is linked to energy security and avoided greenhouse gas emissions. Electrical energy and thermal energy are the primary energy types used for sugar processing. This paper identifies energy management best practices necessary to increase the efficiency of the cogeneration processes. Adoption of energy conservation and efficiency measures is imperative for the sugar industry to generate electricity for own use and for export to the national grid. More energy efficient practices save money and reduce coal consumption. Equipment and technological improvements coupled with process design improvements necessary to improve factory energy efficiency are identified. The paper further discusses the bio-energy role and potential in the South African sugar industry with a view to inform decision making and advise government policies.
- Full Text:
Home healthcare worker scheduling : a group genetic algorithm approach
- Mutingi, M., Mbohwa, Charles
- Authors: Mutingi, M. , Mbohwa, Charles
- Date: 2013
- Subjects: Healthcare staff scheduling , Healthcare service quality , Group genetic algorithm
- Type: Article
- Identifier: uj:4840 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12488
- Description: Home healthcare worker scheduling is a hard combinatorial problem concerned with the allocation of care tasks to healthcare givers at a minimal cost while considering healthcare service quality by striving to meet the time window restrictions specified by the patients. This paper proposes a group genetic algorithm (GGA) for addressing the scheduling problem. The approach utilizes the strengths of unique group genetic operators to effectively and efficiently address the group structure of the problem, providing good solutions within reasonable computation times. Computational results obtained show that the GGA approach is effective.
- Full Text:
- Authors: Mutingi, M. , Mbohwa, Charles
- Date: 2013
- Subjects: Healthcare staff scheduling , Healthcare service quality , Group genetic algorithm
- Type: Article
- Identifier: uj:4840 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12488
- Description: Home healthcare worker scheduling is a hard combinatorial problem concerned with the allocation of care tasks to healthcare givers at a minimal cost while considering healthcare service quality by striving to meet the time window restrictions specified by the patients. This paper proposes a group genetic algorithm (GGA) for addressing the scheduling problem. The approach utilizes the strengths of unique group genetic operators to effectively and efficiently address the group structure of the problem, providing good solutions within reasonable computation times. Computational results obtained show that the GGA approach is effective.
- Full Text:
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