Chemical looping water splitting for hydrogen production, decarbonised steel production and energy storage/generation in-situ with CO2 capture

In the research described in this thesis, a novel hydrogen production process via integrated chemical looping water splitting technology (ICLWS) was developed. In addition, a state-of-the-art process for production of decarbonised iron through a four-stage chemical looping water splitting technology (CLWSFe) was proposed. Both processes were simulated using the Aspen Plus simulator. Heat integration analysis was applied to the two processes, utilising pinch-point analysis in order to minimise utility usage and optimise their thermodynamic performance. Furthermore, sensitivity analysis was performed for the ICLWS process to detect the optimum operating conditions. Both processes were thermodynamically and economically assessed to determine their viability by comparing them with benchmark processes, i.e. the steam methane reforming process (SMR) that was developed earlier in this work and other competitive chemical looping processes described in the literature. The thermodynamic results showed that the ICLWS and the CLWSFe processes exhibited improved effective efficiency by 12.3% and 20.8% compared with the SMR process. Regarding the efficiency of hydrogen production, the ICLWS process exhibited 11.7% higher efficiency than the SMR process; however, the efficiency of hydrogen production by the CLWSFe process was 1.6% lower than that of the SMR process. For the economic assessment, CAPEX, OPEX and the hydrogen production cost were evaluated for both processes. Results indicated that the hydrogen production cost through the ICLWS process with MgAl2O4 as support material was 17.5% lower than that through the SMR process, and was 26.3% lower through use of the CLWSFe process than through use of the SMR when iron as a saleable product was considered. In addition, a one-dimensional steady-state model was developed to obtain the conversion and temperature profiles for all the reactors involved in the ICLWS and CLWSFe processes. Consequently, the size of each reactor was determined. Furthermore, a system of integrated pumped heat-energy storage (IPHES) was developed by integrating pumped-energy storage with the ICLWS process. Then, an open-cycle gas turbine was merged with this system to form another novel energy-storage system called OIPHES. The transient behaviour of the temperature of the solid inside the storage tanks and the daily energy generation for a selected days in the year in both systems were investigated. Based on that, both systems were assessed thermodynamically and economically. Also, an economic sensitivity analysis was performed for the OIPHES process and a feasibility equation was derived showing the conditions required to enhance the feasibility of the OIPHES system. As a case study, the influence of the hydrogen fuel feed rate on the system’s daily profits was studied. Therefore, the optimum hydrogen fuel feed rate to maximise the daily profits of the OIPHES system was selected.Open Acces