Torrefaction of landfill food waste and characterization of the torrefied biomass
- Authors: Pahla, Godwell
- Date: 2016
- Subjects: Waste products as fuel , Renewable energy sources - Environmental aspects , Biomass energy , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243012 , uj:25081
- Description: M.Tech. (Chemical Engineering) , Abstract: Greenhouse gas emissions and municipal solid waste management have presented challenges globally. This study aims to help mitigate these challenges by producing renewable energy from landfill food waste. Food waste is carbon neutral since plants use carbon dioxide for growth, so its application in coal-fired boilers will reduce the amount of carbon dioxide emissions thereby mitigating greenhouse effects. The problem with food waste is that it has high moisture content and it is heterogeneous. This limits its heating value and increases energy requirements for grinding. This study investigated the possibility of upgrading the fuel properties of food waste to produce biochar with similar properties to bituminous coal. The food waste was treated by torrefaction. The main aim was to optimize torrefaction conditions and analyze thermal evolution of the sample during torrefaction. The food waste samples were collected from Marie Louis landfill site in Soweto. The samples were dried and milled for particle size reduction. The samples were further analyzed by proximate and ultimate analyses to determine its fuel properties and elemental composition before torrefaction. A tube furnace was used for the torrefaction process. Temperature was varied from 200 – 300 oC at a constant residence time of 40 min and 10 oC/min heating rate. Calorific value, mass yield, energy yield and energy density were computed and used to determine the appropriate torrefaction temperature. Residence time was then varied from 20 – 60 min at a constant torrefaction temperature of 275 oC and 10 oC/min heating rate. Heating rate was then varied keeping residence time at 20min and torrefaction temperature at 275 oC. Torrefaction temperature had a more pronounced effect than residence time and heating rate. The calorific value was upgraded from 19.76 MJ/kg for dried raw food waste to 26.15 MJ/kg for torrefied food waste at the optimum conditions which were 275 oC, 20 min and 10 oC/min. The higher heating value was comparable to that of bituminous coal currently being used for power generation in South Africa. Elemental analysis of biochar showed an increase in carbon content with temperature due to loss of oxygen containing volatiles. It was also observed that biochar obtained at the optimum conditions could easily be pelletized since it assumed the shape of the crucible...
- Full Text:
- Authors: Pahla, Godwell
- Date: 2016
- Subjects: Waste products as fuel , Renewable energy sources - Environmental aspects , Biomass energy , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243012 , uj:25081
- Description: M.Tech. (Chemical Engineering) , Abstract: Greenhouse gas emissions and municipal solid waste management have presented challenges globally. This study aims to help mitigate these challenges by producing renewable energy from landfill food waste. Food waste is carbon neutral since plants use carbon dioxide for growth, so its application in coal-fired boilers will reduce the amount of carbon dioxide emissions thereby mitigating greenhouse effects. The problem with food waste is that it has high moisture content and it is heterogeneous. This limits its heating value and increases energy requirements for grinding. This study investigated the possibility of upgrading the fuel properties of food waste to produce biochar with similar properties to bituminous coal. The food waste was treated by torrefaction. The main aim was to optimize torrefaction conditions and analyze thermal evolution of the sample during torrefaction. The food waste samples were collected from Marie Louis landfill site in Soweto. The samples were dried and milled for particle size reduction. The samples were further analyzed by proximate and ultimate analyses to determine its fuel properties and elemental composition before torrefaction. A tube furnace was used for the torrefaction process. Temperature was varied from 200 – 300 oC at a constant residence time of 40 min and 10 oC/min heating rate. Calorific value, mass yield, energy yield and energy density were computed and used to determine the appropriate torrefaction temperature. Residence time was then varied from 20 – 60 min at a constant torrefaction temperature of 275 oC and 10 oC/min heating rate. Heating rate was then varied keeping residence time at 20min and torrefaction temperature at 275 oC. Torrefaction temperature had a more pronounced effect than residence time and heating rate. The calorific value was upgraded from 19.76 MJ/kg for dried raw food waste to 26.15 MJ/kg for torrefied food waste at the optimum conditions which were 275 oC, 20 min and 10 oC/min. The higher heating value was comparable to that of bituminous coal currently being used for power generation in South Africa. Elemental analysis of biochar showed an increase in carbon content with temperature due to loss of oxygen containing volatiles. It was also observed that biochar obtained at the optimum conditions could easily be pelletized since it assumed the shape of the crucible...
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Potential for producing sustainable energy from bio-waste through thermal decomposition
- Authors: Manala, Cecil Khosi
- Date: 2017
- Subjects: Waste products as fuel , Refuse and refuse disposal , Biomass energy , Decomposition (Chemistry)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280125 , uj:30095
- Description: M.Ing. (Mechanical Engineering) , Abstract: Energy in its different forms is an important asset to man‟s day-to-day activities from general house hold applications such as cooking and heating to large scale industrial applications such as power generation. However, the current reliance on fossil fuel based energy has become a central concern with respect to sustainable development. Fossil fuels are associated with greenhouse gas emissions and global warming which have been attributed to the dramatic weather and climate change patterns on the planet today posing significant threat to life e. There is, therefore, a need to find more sustainable sources of energy for the planet. Biomass based energy has been used by humanity as a primary source of energy long before the episode of fossil fuel usage. Harnessing of this form of energy has become of overwhelming interest largely due to global warming. It has also been realized that producing renewable energy locally can offer a viable alternative, and facilitate socio-economic development in communities as evidenced by several sustainable energy production projects around South Africa. Biomass contributes 14% of the World‟s primary energy supply. About 75% of its usage is in developing countries. In this work, the organic fraction of municipal solid waste (OFMSW) was quantified at a landfill site in Johannesburg. This was part of a wider project to produce biogas from municipal waste. The potential of that waste to produce syngas by thermal decompositions needs to be investigated as an alternative to anaerobic bio digestion. Furthermore, a bamboo species known as bambusa lacooa, which is currently being introduced for mine dumps rehabilitation in South Africa, was identified as a potential syngas production feedstock. If bamboo based mine dump rehabilitation succeeds, the economic value of the then widely available bamboo needs to be investigated. Production of syngas by pyrolysis becomes one such economic value chain. The aim of this work was therefore to investigate the optimum production of syngas from OFMSW and bamboo by pyrolysis. Specimens of these materials were prepared for thermal decomposition. Bamboo was categorised into wet and dry bamboo and dried in the sun for a period of 14 days. OFMSW made up of mixed food waste was collected from the waste dump landfill site and dried in the sun for a period of 24 hours. The candidate bio-waste materials were subjected to thermal decomposition in a specially designed pyrolysis reactor. Fumes produced during the thermal decomposition were collected at 100˚C temperature intervals from 0 ˚C to 700 ˚C. Dry bamboo produced the highest yield quality of syngas (24% - 23% quality) between 200 ˚C and 400 ˚C. Wet bamboo produced lower syngas yield quality than dry bamboo. The...
- Full Text:
- Authors: Manala, Cecil Khosi
- Date: 2017
- Subjects: Waste products as fuel , Refuse and refuse disposal , Biomass energy , Decomposition (Chemistry)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280125 , uj:30095
- Description: M.Ing. (Mechanical Engineering) , Abstract: Energy in its different forms is an important asset to man‟s day-to-day activities from general house hold applications such as cooking and heating to large scale industrial applications such as power generation. However, the current reliance on fossil fuel based energy has become a central concern with respect to sustainable development. Fossil fuels are associated with greenhouse gas emissions and global warming which have been attributed to the dramatic weather and climate change patterns on the planet today posing significant threat to life e. There is, therefore, a need to find more sustainable sources of energy for the planet. Biomass based energy has been used by humanity as a primary source of energy long before the episode of fossil fuel usage. Harnessing of this form of energy has become of overwhelming interest largely due to global warming. It has also been realized that producing renewable energy locally can offer a viable alternative, and facilitate socio-economic development in communities as evidenced by several sustainable energy production projects around South Africa. Biomass contributes 14% of the World‟s primary energy supply. About 75% of its usage is in developing countries. In this work, the organic fraction of municipal solid waste (OFMSW) was quantified at a landfill site in Johannesburg. This was part of a wider project to produce biogas from municipal waste. The potential of that waste to produce syngas by thermal decompositions needs to be investigated as an alternative to anaerobic bio digestion. Furthermore, a bamboo species known as bambusa lacooa, which is currently being introduced for mine dumps rehabilitation in South Africa, was identified as a potential syngas production feedstock. If bamboo based mine dump rehabilitation succeeds, the economic value of the then widely available bamboo needs to be investigated. Production of syngas by pyrolysis becomes one such economic value chain. The aim of this work was therefore to investigate the optimum production of syngas from OFMSW and bamboo by pyrolysis. Specimens of these materials were prepared for thermal decomposition. Bamboo was categorised into wet and dry bamboo and dried in the sun for a period of 14 days. OFMSW made up of mixed food waste was collected from the waste dump landfill site and dried in the sun for a period of 24 hours. The candidate bio-waste materials were subjected to thermal decomposition in a specially designed pyrolysis reactor. Fumes produced during the thermal decomposition were collected at 100˚C temperature intervals from 0 ˚C to 700 ˚C. Dry bamboo produced the highest yield quality of syngas (24% - 23% quality) between 200 ˚C and 400 ˚C. Wet bamboo produced lower syngas yield quality than dry bamboo. The...
- Full Text:
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