Oxygen Carrier Development and Integrated Process Demonstration for Chemical Looping Gasification Systems

The dependence on fossil fuels to meet the ever rising energy demand cannot be avoided in the near future. Amongst the fossil fuels, only coal utilization can provide energy security to the United States of America due to its indigenous abundance. The utilization of this energy source results in the maximum carbon dioxide emission, which is the main source of anthropogenic greenhouse gas emission. The increasing awareness about greenhouse gas emissions and the ever increasing demand calls for advanced technologies that can handle coal in an efficient and eco-friendly manner.;Chapter 1 describes the various strategies that can be adapted to handle coal and highlights the superior performance of the unique moving bed design based chemical looping systems developed at The Ohio State University that utilize oxygen carriers to transfer oxygen from air to the fuel. The chapter then describes the syngas chemical looping (SCL) process and the coal direct chemical looping (CDCL) process in detail, with special emphasis on the operating conditions of the various reactors in the process and the utilization of the redox property of the metal oxides to achieve in-situ carbon dioxide separation.;Chapter 2 elaborates on the properties that are important for the oxygen carrier. The various metal oxides that can serve as oxygen carriers are compared and the reason behind selection of Iron oxide as the active metal oxide is discussed. The role of the support/inert material in the oxygen carrier is highlighted. The first generation oxygen carrier is synthesized and various parametric testing is performed on this oxygen carrier to study its performance.;Chapter 3 begins with the design of the first ever integrated syngas chemical looping sub-pilot 25kWth unit. The construction and results obtained from operating the unit is discussed in detail. The ability of the system to convert ∼100% of the fuel and generate H2 is showcased. The testing of the unit serves as a proof-of-concept for the SCL process and paves way for the development of the CDCL process. The unit also reveals the areas that the oxygen carrier can be further improved. It also indicates the problems associated with mechanical valves and suggests the need to move towards non-mechanical valve systems.;Chapter 4 analyzes the oxygen carrier performance from the sub-pilot unit in great detail. The influence of volume expansion on the oxygen carrier strength is elucidated. The need to improve the oxygen carrier is realized and the pathway to proceed with the oxygen carrier development is discussed. The testing pattern used to evaluate the improved oxygen carriers is provided and the second generation oxygen carrier is synthesized. The influence of clay supports on the oxygen carrier strength is studied.;Chapter 5 focuses on the targeted development of the oxygen carriers for specific improvements. The influence of dopants on the oxidation rate is studied. The slower kinetics of fuels like methane and coal, compared to syngas is observed. Two different strategies to improve the oxygen carriers to convert the more difficult fuels are adopted. The influence of the pollutants on the performance of the oxygen carrier is discussed. The cost involved with the large quantity of oxygen carriers required for commercial installations drives the need to test cheaper oxygen carrier materials.;Finally, Chapter 6 summarizes the achievements made in the OSU based chemical looping systems and highlights the path for future development. Other research areas where the experience gained can be utilized is also highlighted. Overall, the SCL process has been developed from a concept to a sub-pilot demonstration. Additionally two generations of oxygen carriers have been developed. Expedited progress towards commercialization is being targeted to address the pressing need for clean energy from coal.