Pyrolysis of algal biomass and coal in a rotary kiln reactor: Pyrolysis behaviour, product distribution and kinetic analysis
- Authors: Nyoni, Bothwell
- Date: 2023-12
- Subjects: Algal biofuels , Biomass energy , Coal -- South Africa
- Language: English
- Type: Doctorate theses , text
- Identifier: http://hdl.handle.net/10948/62550 , vital:72823
- Description: There are two primary reasons why the global economy is gradually reducing its dependence on coal as an energy source. Firstly, coal reserves are finite, and while some argue that current reserves will last for generations, the reality is that coal is a non-renewable resource. Secondly, the emissions associated with coal usage have adverse effects on both the environment and human health. While European countries have adopted seemingly aggressive strategies to replace coal and other fossil fuels, South Africa and other developing nations face economic constraints that limit such actions. Fortunately, there are more conservative approaches that can be employed, one of which involves a gradual introduction of renewable energy sources into the energy grid. Wind, solar, and biomass currently stand as the major renewable energy sources under consideration. However, it's worth noting that the intermittent nature of wind and solar energy production poses a significant challenge. Biomass holds the potential to replace coal in retrofitted coal-fired plants. However, the unchecked utilisation of biomass can lead to deforestation and have adverse effects on the human and animal food supply chain, as many essential food items are derived from plants. The debate over using biomass as a fuel source, especially when some types of biomasses can serve as food for humans and animals, has been a subject of ongoing discussion. Furthermore, biomass exhibits a lower energy density when compared to coal. Combustion stands as the primary technology for converting coal into energy and is widely used in most coal-based power plants. Gasification, on the other hand, has been employed for years in South Africa as a coal-to-liquids technology to supplement transportation fuel requirements and reduce reliance on crude oil imports. Pyrolysis, too, has found application as a key method for obtaining high-energy coal char, serving both as an energy source and a reducing agent in blast furnaces for the steelmaking industry. Pyrolysis technologies are gaining popularity in biomass-to-liquids processes due to their simplicity. Currently, there is growing research interest in simultaneous pyrolysis of coal and biomass. The study presented in this thesis focuses on investigating the pyrolysis of Scenedesmus algae biomass and low-grade coal in a small-scale rotary kiln, with particular emphasis on the synthesised liquid products. Algae represent a unique type of biomass that can be cultivated in photo-bioreactors with minimal use of agricultural land. This suggests significant potential for large-scale cultivation of algae, and ongoing efforts are exploring strategies for the mass production of algal biomass.Firstly, pyrolysis studies were carried out via thermogravimetric analysis instruments. It was revealed that because of algae’s considerably higher volatile content and lower carbon content when compared to coal, the pyrolysis process of algal biomass occurred at a faster rate. The highest pyrolytic reactivity of algae was 0.41 mg/min occurring at approximately 290 ᵒC in comparison with coal’s 0.06 mg/min occurring in the approximate temperature range of 550 – 600 ᵒC. The magnitude of the reactivity of the blends depended on the coal/algae ratios used. Furthermore, kinetics analysis revealed that the overall pyrolytic decomposition of coal followed 2nd order kinetics with an activation energy of 81.8 kJ/mol. The decomposition of algae and coal-algae blends occurred in two stages; the first stage decomposition followed 2nd order kinetics with activation energies in the range 130.3 – 145.5 kJ/mol. The second stage decomposition of algae followed 1st order kinetics with an activation energy of 27.3 kJ/mol, whilst coal-algae blends followed 2nd order decomposition with an activation energy range of 69.4 – 74.2 kJ/mol. Secondly, pyrolysis studies were carried out in a rotary kiln reactor wherefrom the char products were collected, and pyrolytic gases condensed to obtain pyroligneous liquid. It was found that the composition of oils synthesised from the pyrolysis of coal was rich in paraffins (52.6 % at 550 ᵒC), however the yield of oil from the pyrolysis of coal was low (6.9 %). Oils from algae and coal-algae blends were dominated by alcohols, fatty acids, fatty acid esters and poly-cyclic aromatic compounds. For example, the most abundant compounds in algae oil produced at 550 ᵒC were fatty acid esters (28.8 %), alcohols (17.6 %), fatty acids (10.8 %) and unsaturated aliphatics (10.7 %); the oil yield obtained from pyrolysis of algae was 40 %. The yields and composition of oils obtained from coal-algae blends were linked to individual contributions from coal and algae, especially at 550 ᵒC; however, the contributions were not proportional due to synergistic effects. This kind of study will contribute to the already existing but limited literature on coal-algae pyrolysis. Furthermore, this study demonstrates the potential of using low-grade coals (an abundant resource in Southern Africa) in conjunction with algal biomass (a renewable resource), in large-scale synthesis of liquid fuels and valuable chemicals via a simple pyrolysis process. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-12
- Authors: Nyoni, Bothwell
- Date: 2023-12
- Subjects: Algal biofuels , Biomass energy , Coal -- South Africa
- Language: English
- Type: Doctorate theses , text
- Identifier: http://hdl.handle.net/10948/62550 , vital:72823
- Description: There are two primary reasons why the global economy is gradually reducing its dependence on coal as an energy source. Firstly, coal reserves are finite, and while some argue that current reserves will last for generations, the reality is that coal is a non-renewable resource. Secondly, the emissions associated with coal usage have adverse effects on both the environment and human health. While European countries have adopted seemingly aggressive strategies to replace coal and other fossil fuels, South Africa and other developing nations face economic constraints that limit such actions. Fortunately, there are more conservative approaches that can be employed, one of which involves a gradual introduction of renewable energy sources into the energy grid. Wind, solar, and biomass currently stand as the major renewable energy sources under consideration. However, it's worth noting that the intermittent nature of wind and solar energy production poses a significant challenge. Biomass holds the potential to replace coal in retrofitted coal-fired plants. However, the unchecked utilisation of biomass can lead to deforestation and have adverse effects on the human and animal food supply chain, as many essential food items are derived from plants. The debate over using biomass as a fuel source, especially when some types of biomasses can serve as food for humans and animals, has been a subject of ongoing discussion. Furthermore, biomass exhibits a lower energy density when compared to coal. Combustion stands as the primary technology for converting coal into energy and is widely used in most coal-based power plants. Gasification, on the other hand, has been employed for years in South Africa as a coal-to-liquids technology to supplement transportation fuel requirements and reduce reliance on crude oil imports. Pyrolysis, too, has found application as a key method for obtaining high-energy coal char, serving both as an energy source and a reducing agent in blast furnaces for the steelmaking industry. Pyrolysis technologies are gaining popularity in biomass-to-liquids processes due to their simplicity. Currently, there is growing research interest in simultaneous pyrolysis of coal and biomass. The study presented in this thesis focuses on investigating the pyrolysis of Scenedesmus algae biomass and low-grade coal in a small-scale rotary kiln, with particular emphasis on the synthesised liquid products. Algae represent a unique type of biomass that can be cultivated in photo-bioreactors with minimal use of agricultural land. This suggests significant potential for large-scale cultivation of algae, and ongoing efforts are exploring strategies for the mass production of algal biomass.Firstly, pyrolysis studies were carried out via thermogravimetric analysis instruments. It was revealed that because of algae’s considerably higher volatile content and lower carbon content when compared to coal, the pyrolysis process of algal biomass occurred at a faster rate. The highest pyrolytic reactivity of algae was 0.41 mg/min occurring at approximately 290 ᵒC in comparison with coal’s 0.06 mg/min occurring in the approximate temperature range of 550 – 600 ᵒC. The magnitude of the reactivity of the blends depended on the coal/algae ratios used. Furthermore, kinetics analysis revealed that the overall pyrolytic decomposition of coal followed 2nd order kinetics with an activation energy of 81.8 kJ/mol. The decomposition of algae and coal-algae blends occurred in two stages; the first stage decomposition followed 2nd order kinetics with activation energies in the range 130.3 – 145.5 kJ/mol. The second stage decomposition of algae followed 1st order kinetics with an activation energy of 27.3 kJ/mol, whilst coal-algae blends followed 2nd order decomposition with an activation energy range of 69.4 – 74.2 kJ/mol. Secondly, pyrolysis studies were carried out in a rotary kiln reactor wherefrom the char products were collected, and pyrolytic gases condensed to obtain pyroligneous liquid. It was found that the composition of oils synthesised from the pyrolysis of coal was rich in paraffins (52.6 % at 550 ᵒC), however the yield of oil from the pyrolysis of coal was low (6.9 %). Oils from algae and coal-algae blends were dominated by alcohols, fatty acids, fatty acid esters and poly-cyclic aromatic compounds. For example, the most abundant compounds in algae oil produced at 550 ᵒC were fatty acid esters (28.8 %), alcohols (17.6 %), fatty acids (10.8 %) and unsaturated aliphatics (10.7 %); the oil yield obtained from pyrolysis of algae was 40 %. The yields and composition of oils obtained from coal-algae blends were linked to individual contributions from coal and algae, especially at 550 ᵒC; however, the contributions were not proportional due to synergistic effects. This kind of study will contribute to the already existing but limited literature on coal-algae pyrolysis. Furthermore, this study demonstrates the potential of using low-grade coals (an abundant resource in Southern Africa) in conjunction with algal biomass (a renewable resource), in large-scale synthesis of liquid fuels and valuable chemicals via a simple pyrolysis process. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-12
Conceptual framework of African immigrant entrepreneurship in South Africa
- Authors: Ngota, Bernard Lama
- Date: 2024-04
- Subjects: Immigrant business enterprises -- South Africa , Entrepreneurship -- South Africa , Foreign workers -- South Africa
- Language: English
- Type: Doctorate theses , text
- Identifier: http://hdl.handle.net/10948/65298 , vital:74090
- Description: Most previous research on immigrant entrepreneurship has focused on investigating and describing immigrant entrepreneurship challenges, characteristics, and drivers of success. Immigrant entrepreneurship research that focuses on Africa, includes the challenges African immigrant entrepreneurs face, and their innate ability to start new ventures in their host countries compared to their native-born counterparts. However, literature on the conceptual framework explaining African immigrant entrepreneurship in South Africa is still nascent. This study assisted to develop a framework that will explain African immigrant entrepreneurship in South Africa. The purpose of this study was to develop a conceptual framework of African immigrant entrepreneurship in South Africa. The aim was achieved through a qualitative research approach that provided insights into African immigrant entrepreneurs and their perceptions thereof; the home country context, the entrepreneur, the resources, business opportunities, the immigrant entrepreneurial ecosystem, new business creation and operations, and the contributions to economic development to the South African economy were explored. Data was collected from a total of twenty-two participants using semi-structured interviews. The interviews were self-administered on a face-to-face contact by the researcher. Participants included African immigrant entrepreneurs; owner/managers and their employees comprised of twelve African immigrant entrepreneurs and ten employees. Data was collected using an interview guide and analysed by means of content and thematic analyses. A conceptual framework of African immigrant entrepreneurship in South Africa was created from the literature, and the collected data was then fitted to match the components of the model. The findings reveal how the different components of home country context, entrepreneur, resources, business opportunity, immigrant entrepreneurial ecosystem, new business creation and operations, were all interlinked to contribute to the economic development of South Africa. Furthermore, the findings revealed that African immigrant social ethnic groups provides support to their members such as “njangi”, loans, emotional support, protection, information, and helping them adjust to their new surroundings. These supports might promote African immigrant entrepreneurship and the creation of a new business in a host country like South Africa. Other findings complement how other employees benefit from African immigrant entrepreneurship in , Thesis (DPhil) -- Faculty of Business and Economic Sciences, School of Management Sciences, 2023 , Most previous research on immigrant entrepreneurship has focused on investigating and describing immigrant entrepreneurship challenges, characteristics, and drivers of success. Immigrant entrepreneurship research that focuses on Africa, includes the challenges African immigrant entrepreneurs face, and their innate ability to start new ventures in their host countries compared to their native-born counterparts. However, literature on the conceptual framework explaining African immigrant entrepreneurship in South Africa is still nascent. This study assisted to develop a framework that will explain African immigrant entrepreneurship in South Africa. The purpose of this study was to develop a conceptual framework of African immigrant entrepreneurship in South Africa. The aim was achieved through a qualitative research approach that provided insights into African immigrant entrepreneurs and their perceptions thereof; the home country context, the entrepreneur, the resources, business opportunities, the immigrant entrepreneurial ecosystem, new business creation and operations, and the contributions to economic development to the South African economy were explored. Data was collected from a total of twenty-two participants using semi-structured interviews. The interviews were self-administered on a face-to-face contact by the researcher. Participants included African immigrant entrepreneurs; owner/managers and their employees comprised of twelve African immigrant entrepreneurs and ten employees. Data was collected using an interview guide and analysed by means of content and thematic analyses. A conceptual framework of African immigrant entrepreneurship in South Africa was created from the literature, and the collected data was then fitted to match the components of the model. The findings reveal how the different components of home country context, entrepreneur, resources, business opportunity, immigrant entrepreneurial ecosystem, new business creation and operations, were all interlinked to contribute to the economic development of South Africa. Furthermore, the findings revealed that African immigrant social ethnic groups provides support to their members such as “njangi”, loans, emotional support, protection, information, and helping them adjust to their new surroundings. These supports might promote African immigrant entrepreneurship and the creation of a new business in a host country like South Africa. Other findings complement how other employees benefit from African immigrant entrepreneurship in South Africa. This was evidence in the entrepreneurs’ responsibilities, improved employees’ skills development, improved employee economic status and improved employee-employer relationships. The proposed framework serves as a valuable resource for scholars and practitioners, especially those involved with the making of legislations in the country. The study recommends that broad-based integrated public policy interventions and strategies be developed and implemented to have a positive impact on the country's economic success in terms of job creation, skills transfer, poverty reduction, and economic growth to achieve the socio-economic well-being of the people.
- Full Text:
- Date Issued: 2024-04
- Authors: Ngota, Bernard Lama
- Date: 2024-04
- Subjects: Immigrant business enterprises -- South Africa , Entrepreneurship -- South Africa , Foreign workers -- South Africa
- Language: English
- Type: Doctorate theses , text
- Identifier: http://hdl.handle.net/10948/65298 , vital:74090
- Description: Most previous research on immigrant entrepreneurship has focused on investigating and describing immigrant entrepreneurship challenges, characteristics, and drivers of success. Immigrant entrepreneurship research that focuses on Africa, includes the challenges African immigrant entrepreneurs face, and their innate ability to start new ventures in their host countries compared to their native-born counterparts. However, literature on the conceptual framework explaining African immigrant entrepreneurship in South Africa is still nascent. This study assisted to develop a framework that will explain African immigrant entrepreneurship in South Africa. The purpose of this study was to develop a conceptual framework of African immigrant entrepreneurship in South Africa. The aim was achieved through a qualitative research approach that provided insights into African immigrant entrepreneurs and their perceptions thereof; the home country context, the entrepreneur, the resources, business opportunities, the immigrant entrepreneurial ecosystem, new business creation and operations, and the contributions to economic development to the South African economy were explored. Data was collected from a total of twenty-two participants using semi-structured interviews. The interviews were self-administered on a face-to-face contact by the researcher. Participants included African immigrant entrepreneurs; owner/managers and their employees comprised of twelve African immigrant entrepreneurs and ten employees. Data was collected using an interview guide and analysed by means of content and thematic analyses. A conceptual framework of African immigrant entrepreneurship in South Africa was created from the literature, and the collected data was then fitted to match the components of the model. The findings reveal how the different components of home country context, entrepreneur, resources, business opportunity, immigrant entrepreneurial ecosystem, new business creation and operations, were all interlinked to contribute to the economic development of South Africa. Furthermore, the findings revealed that African immigrant social ethnic groups provides support to their members such as “njangi”, loans, emotional support, protection, information, and helping them adjust to their new surroundings. These supports might promote African immigrant entrepreneurship and the creation of a new business in a host country like South Africa. Other findings complement how other employees benefit from African immigrant entrepreneurship in , Thesis (DPhil) -- Faculty of Business and Economic Sciences, School of Management Sciences, 2023 , Most previous research on immigrant entrepreneurship has focused on investigating and describing immigrant entrepreneurship challenges, characteristics, and drivers of success. Immigrant entrepreneurship research that focuses on Africa, includes the challenges African immigrant entrepreneurs face, and their innate ability to start new ventures in their host countries compared to their native-born counterparts. However, literature on the conceptual framework explaining African immigrant entrepreneurship in South Africa is still nascent. This study assisted to develop a framework that will explain African immigrant entrepreneurship in South Africa. The purpose of this study was to develop a conceptual framework of African immigrant entrepreneurship in South Africa. The aim was achieved through a qualitative research approach that provided insights into African immigrant entrepreneurs and their perceptions thereof; the home country context, the entrepreneur, the resources, business opportunities, the immigrant entrepreneurial ecosystem, new business creation and operations, and the contributions to economic development to the South African economy were explored. Data was collected from a total of twenty-two participants using semi-structured interviews. The interviews were self-administered on a face-to-face contact by the researcher. Participants included African immigrant entrepreneurs; owner/managers and their employees comprised of twelve African immigrant entrepreneurs and ten employees. Data was collected using an interview guide and analysed by means of content and thematic analyses. A conceptual framework of African immigrant entrepreneurship in South Africa was created from the literature, and the collected data was then fitted to match the components of the model. The findings reveal how the different components of home country context, entrepreneur, resources, business opportunity, immigrant entrepreneurial ecosystem, new business creation and operations, were all interlinked to contribute to the economic development of South Africa. Furthermore, the findings revealed that African immigrant social ethnic groups provides support to their members such as “njangi”, loans, emotional support, protection, information, and helping them adjust to their new surroundings. These supports might promote African immigrant entrepreneurship and the creation of a new business in a host country like South Africa. Other findings complement how other employees benefit from African immigrant entrepreneurship in South Africa. This was evidence in the entrepreneurs’ responsibilities, improved employees’ skills development, improved employee economic status and improved employee-employer relationships. The proposed framework serves as a valuable resource for scholars and practitioners, especially those involved with the making of legislations in the country. The study recommends that broad-based integrated public policy interventions and strategies be developed and implemented to have a positive impact on the country's economic success in terms of job creation, skills transfer, poverty reduction, and economic growth to achieve the socio-economic well-being of the people.
- Full Text:
- Date Issued: 2024-04
Herpetofaunal diversity and affiliations of the Okavango River Basin, with specific focus on the Angolan headwaters
- Authors: Conradie, Werner
- Date: 2024-04
- Subjects: Water conservation -- Okavango River Delta , Watersheds -- Okavango River -- Angola , Biodiversity -- Angola
- Language: English
- Type: Doctorate theses , text
- Identifier: http://hdl.handle.net/10948/63667 , vital:73576
- Description: Although Africa is reputed to possess some of the richest herpetofaunal diversities in the world, a number of areas remain poorly documented and thus inadequately conserved. One such area in particular is the south-eastern part of Angola. Angola endured a long struggle for independence with a protracted civil war that lasted for nearly three decades, leaving the status of the country’s biodiversity in turmoil. Over the past two decades, Angola has become more accessible for biodiversity surveys, opening up new opportunities to document these previously poorly studied areas and help conserve its biodiversity. South-eastern Angola is the water source of the world-renowned Okavango Delta. However very little is known about the biodiversity, diversity status and conservation significance of the headwaters supplying the largest inland delta in the world. To address this bias in sampling and to investigate the conservation importance of the region, a series of rapid biodiversity surveys of the Angolan Okavango River Basin were conducted between 2012 and 2019. This study contributed over 2150 individual records of amphibians and reptiles, representing 88 reptile and 43 amphibian species. At least 15 species were added to the growing country checklist, with the south-eastern region of Angola now comprising 113 reptile species and 51 amphibian species. Because of this study, the area is now one of the most species-rich and well-studied areas in Angola. This study provided the first genetic data for 26 species, and sequences containing Angolan specimens for the first time were generated for 80 species, of which 23 species have originally been described from Angola. Maximum likelihood and Bayesian inference analyses, supported by species delimitation analyses, were utilised to validate specific species statuses. This allowed for the description of five new species of snake, one gecko and two frogs for Angola. The material further contributed to the description of a new genus of snakes. Numerous undescribed and potentially cryptic species were identified, long-lasting taxonomic issues were resolved, and various taxonomic adjustments were emphasised. Further contributions of the material include assisting in the revision of targeted Angolan amphibian and reptile groups as well as large-scale phylogenetic studies across Africa. , Thesis (PhD) -- Faculty of Science, School of Natural Resource Science & Management, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Conradie, Werner
- Date: 2024-04
- Subjects: Water conservation -- Okavango River Delta , Watersheds -- Okavango River -- Angola , Biodiversity -- Angola
- Language: English
- Type: Doctorate theses , text
- Identifier: http://hdl.handle.net/10948/63667 , vital:73576
- Description: Although Africa is reputed to possess some of the richest herpetofaunal diversities in the world, a number of areas remain poorly documented and thus inadequately conserved. One such area in particular is the south-eastern part of Angola. Angola endured a long struggle for independence with a protracted civil war that lasted for nearly three decades, leaving the status of the country’s biodiversity in turmoil. Over the past two decades, Angola has become more accessible for biodiversity surveys, opening up new opportunities to document these previously poorly studied areas and help conserve its biodiversity. South-eastern Angola is the water source of the world-renowned Okavango Delta. However very little is known about the biodiversity, diversity status and conservation significance of the headwaters supplying the largest inland delta in the world. To address this bias in sampling and to investigate the conservation importance of the region, a series of rapid biodiversity surveys of the Angolan Okavango River Basin were conducted between 2012 and 2019. This study contributed over 2150 individual records of amphibians and reptiles, representing 88 reptile and 43 amphibian species. At least 15 species were added to the growing country checklist, with the south-eastern region of Angola now comprising 113 reptile species and 51 amphibian species. Because of this study, the area is now one of the most species-rich and well-studied areas in Angola. This study provided the first genetic data for 26 species, and sequences containing Angolan specimens for the first time were generated for 80 species, of which 23 species have originally been described from Angola. Maximum likelihood and Bayesian inference analyses, supported by species delimitation analyses, were utilised to validate specific species statuses. This allowed for the description of five new species of snake, one gecko and two frogs for Angola. The material further contributed to the description of a new genus of snakes. Numerous undescribed and potentially cryptic species were identified, long-lasting taxonomic issues were resolved, and various taxonomic adjustments were emphasised. Further contributions of the material include assisting in the revision of targeted Angolan amphibian and reptile groups as well as large-scale phylogenetic studies across Africa. , Thesis (PhD) -- Faculty of Science, School of Natural Resource Science & Management, 2024
- Full Text:
- Date Issued: 2024-04
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