Prediction of In-Situ Gasification Chemical Looping Combustion Effects of Operating Conditions

Chemical Looping Combustion (CLC) has been considered as one of the most promising technologies to implement CO2 capture with low energy penalty. A comprehensive three-dimensional numerical model integrating gas-solid flow and reactions, based on the authors' previous work (Energy Fuels 2013, 27, 2173-2184), is applied to simulate the in-situ Gasification Chemical Looping Combustion (iG-CLC) process in a circulating fluidized bed (CFB) riser fuel reactor. Extending from the previous work, the present study further validates the model and investigates the effects of several important operating conditions, i.e., solids flux, steam flow and operating pressure, on the gas-solid flow behaviors, CO2 concentration and fuel conversion, comprehensively. The simulated fuel reactor has a height of 5 m and an internal diameter of 60 mm. The simulated oxygen carrier is a Norwegian ilmenite and the simulated fuel is a Colombian bituminous coal. The results of this simulation work have shown that an increase in the solids flux can promote CO2 concentration, but may also have a negative effect on carbon conversion. A decrease in the steam flow leads to positive effects on not only the CO2 concentration but also the carbon conversion. However, the reduction of steam flow is limited by the CFB operation process. An increase in the operating pressure can improve both the CO2 concentration and carbon conversion and therefore, the CFB riser fuel reactor of a practical iG-CLC system is recommended to be designed and operated under a certain pressurized conditions.