SusChEM: Co-firing Biomass and Coal under Pressurized Oxy-fired Combustion Conditions

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1604630 Eddings, Eric G.The use of biomass as a co-firing fuel with coal is a viable option for reducing net CO2 production from coal-fired power generation. Oxy-combustion is also considered a potential near-term option for enhancing carbon capture and storage (CCS), by producing a high concentration CO2 stream that can be more readily recovered due to combustion of fuels using oxygen and recycled flue gas (primarily CO2). Circulating fluidized-bed (CFB) boilers are well-suited for utilizing low- and high-quality coals, and can adapt to a wide range of biomass feedstocks. Pulverized-coal (PC) boilers represent the most widespread type of coal-fired combustion system used for power generation, and have been the subject of many biomass co-firing demonstrations. In addition, the use of oxy-combustion at high pressures allows for improved thermodynamic efficiencies for power generation with CCS, as well as increased partial pressure of CO2 to facilitate CCS. Thus, the integration of these various technologies provides a great opportunity to address the pressing need of greenhouse gas control. The University of Utah, Zhejiang University and the University of Wyoming have considerable research experience, in both pulverized-coal (PC) and circulating fluidized-bed (CFB) systems, to investigate fundamental aspects related to the integration of oxy-fired combustion with co-firing of biomass and coal under high-pressure operation. The project will utilize bench-scale high-pressure reactors to perform research under both CFB and PC-fired combustion conditions. The project focuses on fundamental investigations of 2 key research areas that must be addressed before widespread adoption of biomass/coal co-firing in high-pressure, oxy-fuel PC and CFB combustors can be realized. These areas are: 1) fundamental characteristics of biomass/coal co-pyrolysis and co-combustion under pressurized oxy-fuel conditions, and 2) mineral matter transformations during pressurized oxy-fuel co-firing of coal and biomass. The work represents the nexus of 3 different technologies: coal/biomass co-firing, oxy-fuel combustion and high-pressure combustion. While there have been some studies published on each of these technologies, or combinations of two of them, there is no fundamental information in the literature on the combination of all 3 technologies. This project will address this scientific void through a detailed investigation of these combined technologies for both PC-fired and CFB combustion scenarios. The research will lay a foundation for the expansion of biomass utilization in power generation, particularly under high-efficiency conditions, which would make a significant contribution to reductions in the world's greenhouse gas emissions. Since China is currently a world leader in the implementation of CFB technology for electric power generation, and is also one of the world leaders in the number of new PC-fired power generation systems being constructed each year, their participation will provide a potential pathway for commercial adoption of the proposed technologies