| Summary: | Using biomass for utility heat and electricity generation can supplement use of fossil fuels, whose emissions of carbon dioxide likely risk causing serious climate change and ocean acidification. Biomass as energy source is a limited resource and when used as fuel in thermal power plants this currently results in higher production costs than using fossil fuels such as natural gas and coal. It is, therefore, important to find highly efficient and reliable biomass conversion technologies. Reliability is important to minimize investment risk. Co-firing biomass with coal is well known as a potential low cost and high efficient way of introducing biomass in the stationary energy system. Yet, several regions around Europe and elsewhere are strongly dependent on natural gas for electricity generation, typically applying combined cycle gas turbine (CCGT) plants. Although CO2 emissions from natural gas is considerably lower than from coal fired plants, it is less known how to introduce biomass as fuel in natural gas fired plants than in coal. Therefore, the present thesis evaluates options for integration of thermal conversion of biomass with existing CCGT plants. The focus on existing gas fired plants is motivated by a) gas fired plants are becoming increasingly dominant in some regions and there should be sought integration options that are not only based on co-firing with coal, and b) if the existing power plant infrastructure can be used to introduce biomass this could facilitate a near term introduction of biomass, contributing to near term CO2 mitigation targets, as opposed to building biomass-only dedicated plants.The biomass-based options for CCGT integration investigated in this work are hybrid combined cycles (HCC) and biomass gasification. A HCC is a combined cycle firing various fuels; in the present case natural gas in gas turbines (GTs) as topping cycle, and biomass in a fluidized bed boiler as bottoming (steam) cycle. HCC options include fully-fired (hot windbox) schemes with uncooled flue gases from GTs ...
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