Numerical investigation of hydrodynamics and cluster characteristics in a chemical looping combustion system

Abstract

Chemical looping combustion (CLC) technology is promising for high-efficient carbon dioxide capture with low energy penalty. Most existing CLC systems were constructed based on two fluidized bed reactors. In this work, a full-loop numerical model was established for a novel CLC system integrated with a circulating fluidized bed riser fuel reactor and a moving bed air reactor. For the fuel reactor, the radial and axial distributions of gas-solid concentration and velocities are fully investigated. It is found single-sided particle return affects radial distribution symmetry of gas-solid flows, but the influence gradually decreases with increasing reactor height. The cluster characteristics including time fraction, frequency, duration time and concentration are also investigated, and results demonstrate the particle clusters are more difficult to form and last long in the center of fuel reactor. For the air reactor, the operation performance of a tower-type reactor is compared with a common cylindrical reactor, and the cavity is not formed in the top of the tower-type reactor. For the whole system, effects of the particle diameter on pressure profiles, solid circulation stability and other flow dynamics are evaluated. Overall, the inner flow characteristics will provide fundamental guidance for the design, optimization and scale-up of the system.