Computational Fluid Dynamics–Discrete Element Model Simulation of Flow Characteristics and Solids’ Residence Time Distribution in a Moving Bed Air Reactor for Chemical Looping Combustion

Abstract

In our previous experimental study, a novel multistage moving bed air reactor was proposed for chemical looping combustion; some operating mechanisms including the gas flow carrying capacity and gas leakage performance were investigated. In this paper, a quasi-2D computational fluid dynamics–discrete element model cold flow model is developed for the experimental air reactor. Effects of the operating parameters, geometric parameters, and internals on solids’ flow characteristics and residence time distributions are studied by using the tracer particles. Results show that with increase in the loop seal gas velocity, the solids’ mass flux increases and the average solids’ residence time decreases. The reactor angle has more influence in solids’ movements in the near-wall region, while the wedge angle has more effect on the solids’ movements in the lower part of the reactor. With decrease of the reactor angle, increase of the wedge angle, or increase of the down-comer diameter, the solids’ flow gets closer to ideal plug flow in the reactor. The internals can accelerate the particles in the near-wall region; internals in triangular arrays are better than those in square arrays to slow down the central particles.

Semiempirical Model of the Drag Force Acting on an Obstacle in Downward Dense Particle Flows as per the Flow-Around Behavior

“…Dense downward particle flow is a common particle flow state and is widely applied in various particle transport equipment or chemical reactors (circulating fluidized bed, silos, moving bed heat exchanger, chemical looping combustion reactor, etc.). In a downward particle flow channel, it is common to arrange internals to adjust the flow state or to serve as heat exchange tubes .…”

Impact of the Reactor Structure on Biomass Pyrolysis in Fluidized-Bed Reactors: A Coarse-Grained CFD-DEM Study

“…Zhao et al 29 coupled CFD-DEM with the immersed boundary method and evaluated the heat transfer behavior in a bubbling fluidized bed with an immersed tube. Additionally, using CFD-DEM, Shao et al 30 researched the influence of the structural parameters of a moving bed air reactor on the flow characteristics, in which the reactor angle and downcomer diameter were studied. Hu et al 31 also adopted CFD-DEM to analyze the effect of secondary gas injection height on the fluidized-bed combustion process.…”

Comparative Study on Ni/γ-Al2O3 Prepared via Ultrasonic Irradiation and Impregnation Approaches as an Oxygen Carrier in Chemical Looping Combustion

“…7 Chemical looping technology utilizes a solid material mainly to transport the oxygen from the air to the fuel reactor. 8 It has been proposed in various ways including chemical looping combustion (CLC), chemical looping reforming (CLR), chemical looping gasification (CLG), and chemical looping hydrogen generation (CLHG). 9 CLC is considered a promising technology where the combustion process occurs in a nitrogen-free atmosphere, and it does not require the utilization of a CO 2 capture device, which ultimately reduces the operational cost.…”

“…It releases a CO 2 -enriched flue gas that simplifies the capture and separation of CO 2 . Chemical looping technology utilizes a solid material mainly to transport the oxygen from the air to the fuel reactor . It has been proposed in various ways including chemical looping combustion (CLC), chemical looping reforming (CLR), chemical looping gasification (CLG), and chemical looping hydrogen generation (CLHG) .…”