Study of the Methane Chemical Looping Combustion Process Using Supported Metal Carriers for Carbon Capture

Abstract

Global warming caused by greenhouse gases (GHGs) has in the recent years become a great concern internationally. Recent changes in weather patterns can be attributed as one of the possible results of global warming. The emission portion of carbon dioxide (CO2) is one of the highest among the GHGs. Accordingly, carbon capture technology is needed to decrease CO2 emission to the atmosphere. The Chemical Looping Combustion (CLC) process is an alternative and immature process to capture CO2. This process produces a concentrated stream of CO2 that does not require any further expensive separation unit. To commercialize this technology, this thesis presents a comprehensive study of the methane CLC process using supported mixed metals oxygen carriers. In the first part of the study, synthesis and reactivity evaluation of monometallic carriers were conducted, assessing and discussing the effect of various operating conditions on reactivity. Interaction between monometallic precursors (Ni & Co) and alumina support was observed, resulting in forming intermediate phases such as CoAl2O4 and NiAl2O4; the CoAl2O4 phase was successfully reduced but the NiAl2O4 did not reduce. By varying the temperature (800°C-950°C), the highest observable oxygen capacity for all 16 samples was found to be between 900°C and 950°C. In the second part of the study, optimum operating conditions obtained previously were applied to the supported bimetallic carriers, leading to novel findings. The redox reactions pathways were determined, with a main conclusion being that once the chemical stability between precursors and supports maximized, negligible interaction could be anticipated. The Ni-Co/ZrO2, Ni-Cu/ZrO2, and Ni-Fe/ZrO2 samples showed stable oxygen capacities compared to others and negligible interaction between precursors and supports. In the last part of the study, Aspen Plus computer software was used to examine the feasibility and sustainability of the process. It was found that the loading percentage of precursor (Ni-Cu/ZrO2) showed no significant effect on conversion in the fuel reactor, but conversion increased by 39% in the air reactor. Finally, the case study was compared with other competing processes. The overall efficiency of the case study was found to be higher than that of the competing processes, suggesting its potential for commercialization.