Computational fluid dynamics in ICFB reactor: Effect of proportion of riser and downer on system hydrodynamics

• The CTFB regime was first illustrated inside the ICFB reactor. • The ratio of the ICFB reactor between the riser and the downer was examined. • Energy oscillations in ICFB system were dominated by turbulent granular temperature. • Uniformly solid volume fraction and good mixing were shown in the ICFB reactor. • Gas leakage understanding is crucial for maximizing the system efficiency. Internally Circulating Fluidized Bed (ICFB) reactors stand out as efficient technology in fluidized bed applications, featuring internal solid particle circulation that has garnered attention across various industries. This study employs computational fluid dynamics (CFD) simulation to investigate the impact of operating parameters on the hydrodynamics of an ICFB reactor using gamma-alumina (γ-Al 2 O 3 ) as a bed material. The gas-solid flow regime in the riser section is identified as a circulating turbulent fluidized bed (CTFB), contrasting with the downer section, which exhibits bubbling bed fluidization. Examining mechanisms governing solid circulation leads to the design of a pseudo-2D cold-flow ICFB unit with a reactor diameter ratio between riser and downer ranging from 2:1 to 1:2. It was found that, with a reactor diameter ratio of 1:2, solid volume fraction profiles in the axial and radial directions become denser and more uniform throughout the riser, while the downer section exhibits uniform distribution along both axial and radial directions. The dominant role of turbulent granular temperature in oscillations within the ICFB system is observed. This suggests the formation of gas bubbles and solid accumulation as the primary flow configurations, illustrating system mixing and defining hydrodynamics for both solid particles and gas phases. Consequently, this study advances our understanding of ICFB reactor dynamics and offers valuable insights for optimizing reactor design.