| Description |
Chemical-looping combustion (CLC) is one of the candidate technologies that is currently being explored to reduce the energy penalty associated with capturing CO2 from coal-fired power plants. In CLC, the fuel is burnt in the presence of oxygen supplied by an oxygen carrier circulating between two reactors, instead of atmospheric air. This dissertation investigates the requisite process modeling aspects for CLC for solid carbonaceous fuels, in particular focusing on chemical-looping with oxygen uncoupling (CLOU). In CLOU, gaseous phase oxygen is released by the decomposition of a metal oxide (e.g. CuO) in which the solid fuel burns to form CO2 . This contrasts with CLC, where the solid fuel has to be gasified initially to form syngas which subsequently reacts with the circulating oxygen carrier to form CO2. As a first step, the significance of the Law of Additive Reaction Times in identifying the controlling regime (internal/external mass transfer or chemical reaction) for CLC systems was explored. Two reported experimental studies for copper oxidation reaction in air reactor were reanalyzed. The methodology developed was applied to analyze the CuO decomposition and Cu2O oxidation reaction for CLOU. A rate analysis of the reported bench-scale batch fluidized-bed CLOU experimental data was performed to determine the kinetics of the CuO decomposition, Cu2O oxidation, and petcoke oxidation reactions. The obtained kinetics were subsequently utilized in the development of a fluidized-bed model to evaluate the oxygen and carbon dioxide concentration trends, and the results were validated against independently obtained experimental data reported in literature. The kinetics obtained from the rate analysis of the CLOU reactions were employed in the development of a process model using ASPEN PLUS. Material and energy balance scenarios were developed for solid fuel combustion using a copper-based oxygen carrier for CLOU, and compared with CLC employing an iron-based oxygen carrier. The conceptual design principles will be employed in future investigations on a process development unit based on the CLOU process currently under construction at the University of Utah. |
