Master of Science / Department of Biological and Agricultural Engineering / Wenqiao Yuan / Gasification is an efficient way to produce energy from biomass, which has significant positive impacts on the environment, domestic economy, national energy security, and the society in general. In this study, a lab-scale updraft biomass gasifier was designed, built, and instrumented for stable gasification using low-bulk density biomass. Related accessories, such as a biomass feeder, inlet air temperature controller, air injection nozzle, and tar cracking system, were also developed to enhance gasifier performance. The effect of operation parameters on gasifier performance was studied. Two operational parameters, including air flow rate and feed-air temperature, were studied on three sources of biomass: prairie hay, sorghum biomass, and wood chips. Results showed that higher air flow rate increased tar contents in syngas for all three types. It was also found that different biomasses gave significantly different tar contents, in the order of wood chips>sorghum biomass>prairie hay. Feed-air temperature did not have a significant effect on tar content in syngas except for prairie hay, where higher feed air temperature reduced tar. A statistical model was implemented to study differences on syngas composition. Results showed that different biomasses produced syngas with different high heating value, e.g., wood chips > prairie hay > sorghum biomass. CO composition also showed differences by feed air temperature and biomass, e.g. prairie hay>wood chips>sorghum biomass, but H[subscript]2 did not show significant differences by either biomass type or operating conditions. Moreover, because of the downstream problems caused by tars in syngas such as tar condensation in pipelines, blockage and machinery collapse, an in-situ tar cracking system was developed to remove tars in syngas. The tar cracking device was built in the middle of the gasifier’s combustion using gasification heat to drive the reactions. The in-situ system was found to be very effective in tar removal and syngas enhancement. The highest tar removal of 95% was achieved at 0.3s residence time and 10% nickel loading. This condition also gave the highest syngas HHV increment of 36% (7.33 MJ/m[superscript]3). The effect of gas residence time and Ni loading on tar removal and syngas composition was also studied. Gas residence of 0.2-0.3s and Ni loading of 10% were found appropriate in this study.

Gasification of biomass for electricity power generation has been a proven technology in a number of countries in the world. MSW consists of biomass, glass, plastics, metallic scrap and street debris. Biomass constitutes the highest proportion of MSW and being an energy resource, implies that it can contribute tremendously to the energy needs of any country since every country is endowed with this resource which is generated in enormous tonnes per day. The challenge would then be the choice of the technology to harness this abundant energy resource subject to financial and environmental constraints.    In Uganda, MSW gasification for power generation has never been implemented in spite of the 500-600 tonnes of MSW collected per day, the biomass component of the MSW comprising 88%. MSW is instead collected in skips, transported by trucks to a landfill were it is deposited and left to decompose releasing methane (CH4) and carbon dioxide (CO2) gases which are highly potent greenhouse gases. In this regard, the many tonnes per day of MSW collected in Kampala city (area of the study) portray significant potential of generating producer gas using the technology of gasification to run engines for power generation and this study evaluated possible gasifier-engine system applications for power generation. Experiments were carried out  at the Faculty of Technology, Makerere University to determine biomass characteristics (e.g. moisture content, ash content) and gasification parameters(e.g. lower heating value)  of MSW required for gasifier-engine applications. After establishing the lower heating value of the producer gas from MSW, a theoretical design of a gasifier-engine system was investigated for possible applications with the biomass component of MSW and an economic analysis was done to assess the feasibility of the project.

Gasification of biomass for electricity power generation has been a proven technology in a number of countries in the world. MSW consists of biomass, glass, plastics, metallic scrap and street debris. Biomass constitutes the highest proportion of MSW and being an energy resource, implies that it can contribute tremendously to the energy needs of any country since every country is endowed with this resource which is generated in enormous tonnes per day. The challenge would then be the choice of the technology to harness this abundant energy resource subject to financial and environmental constraints.    In Uganda, MSW gasification for power generation has never been implemented in spite of the 500-600 tonnes of MSW collected per day, the biomass component of the MSW comprising 88%. MSW is instead collected in skips, transported by trucks to a landfill were it is deposited and left to decompose releasing methane (CH4) and carbon dioxide (CO2) gases which are highly potent greenhouse gases. In this regard, the many tonnes per day of MSW collected in Kampala city (area of the study) portray significant potential of generating producer gas using the technology of gasification to run engines for power generation and this study evaluated possible gasifier-engine system applications for power generation. Experiments were carried out  at the Faculty of Technology, Makerere University to determine biomass characteristics (e.g. moisture content, ash content) and gasification parameters(e.g. lower heating value)  of MSW required for gasifier-engine applications. After establishing the lower heating value of the producer gas from MSW, a theoretical design of a gasifier-engine system was investigated for possible applications with the biomass component of MSW and an economic analysis was done to assess the feasibility of the project.