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Advanced biopower generation via gasification of biomass and municipal solid waste

Indrawan, Natarianto
The overall goal of this study was to develop and analyze efficient power generation systems through the downdraft gasification of biomass and municipal solid waste (MSW) for distributed power applications. This goal was accomplished with the following major objectives that were focus of dissertation chapters. The literature review of power generation and emissions from gasification-based technologies was presented in Chapter 1. Performance and emission analyses of experimental of a 10-kW internal combustion (IC) engine running on syngas generated from gasification of a low density biomass was presented in Chapter 2. Engine performance was satisfactory with maximum load of 5 kW, resulting in an electrical efficiency of 21.3%. The only modification made to the engine was addition of a single venturi pipe in the air-intake system for adjusting flows and mixing of air and syngas. Chapter 3 focused on performance and emission analyses of the gasification-energy system when biomass mixed with MSW in various ratios was used as the feedstock (co-gasification). The air-intake system was further modified using a two series venturi pipe. The gasification and engine performance was stable with maximum MSW weight ratio of 40 wt.%, producing the maximum engine output power of 5 kW with an electrical efficiency of 19.5%. An increase in MSW ratio resulted in an increase of hydrocarbon and SO2 engine emissions. An economic analysis of a 60-kW power plant based on the downdraft gasification system was presented in Chapter 4. The downdraft gasification power plant showed a payback period, an internal rate of return (IRR), a modified internal rate of return (MIRR), and a net present value (NPV) of 7.7 years, 10.9%, 7.7%, and $84,550, respectively. Using sensitivity analysis, feed-in-tariff resulted in the greatest impact on the project's NPV, followed by the electricity selling price, the output power and the tipping fee, while the labor and feedstock cost and the tax rate generated a negative impact on the NPV. In comparison with a commercially available 250-kW downdraft gasification power generation, the downdraft gasification power plant performed a shorter payback period and a higher IRR. However, these results may vary significantly based on local economic factors and assumptions made. Modeling of low-temperature plasma gasification technology using MSW was the main focus of Chapter 5. At temperatures of 2,500, 2000, and 1,500°C, the energy consumption of the plasma torch decreased from 3,816 kW at conventional condition (4000°C) to 3,157, 2,775, and 2,358 kW, respectively, with corresponding gasification efficiency of 48.7%, 48.9%, and 49.2%. Finally, Chapter 6 focused on a simulation based on experimental data was used to investigate performance of a hybrid power generation (solid oxide fuel cell and gas turbine) using syngas generated from gasification of biomass and municipal solid waste mixture. At 40 wt.% MSW ratio, the syngas produced resulting in a total stack power of 307 kW, and a gas turbine output of 40 kW with a system electrical efficiency of 49.5%.