Development of a hydrodynamic model and the corresponding virtual software for dual-loop circulating fluidized beds
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RESEARCH ARTICLE
Development of a hydrodynamic model and the corresponding virtual software for dual-loop circulating fluidized beds Shanwei Hu1, Xinhua Liu (✉)1,2 1 State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China 2 Dalian National Laboratory for Clean Energy, Dalian 116023, China
© Higher Education Press 2020
Abstract Dual-loop circulating fluidized bed (CFB) reactors have been widely applied in industry because of their good heat and mass transfer characteristics and continuous handling ability. However, the design of such reactors is notoriously difficult owing to the poor understanding of the underlying mechanisms, meaning it has been heavily based on empiricism and stepwise experiments. Modeling the gas-solid CFB system requires a quantitative description of the multiscale heterogeneity in the sub-reactors and the strong coupling between them. This article proposed a general method for modeling multiloop CFB systems by utilizing the energy minimization multiscale (EMMS) principle. A full-loop modeling scheme was implemented by using the EMMS model and/or its extension models to compute the hydrodynamic parameters of the sub-reactors, to achieve the mass conservation and pressure balance in each circulation loop. Based on the modularization strategy, corresponding interactive simulation software was further developed to facilitate the flexible creation and fast modeling of a customized multi-loop CFB reactor. This research can be expected to provide quantitative references for the design and scale-up of gas-solid CFB reactors and lay a solid foundation for the realization of virtual process engineering. Keywords multi-loop circulating fluidized bed, mathematical modeling, energy minimization multiscale, virtual fluidization, mesoscale structure
Received February 14, 2020; accepted April 25, 2020 E-mail: [email protected]
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Introduction
Dual-loop circulating fluidized bed (CFB) reactors have been widely used in the chemical and process industries due to their excellent mass and heat transfer efficiencies as well as high product throughput [1,2]. Such reactors have complicated configurations, which generally consist of multiple sub-reactor components with varying geometries and sizes. Designing this type of reactor is quite challenging due to the lack of understanding of inherent flow complexities. First, it is difficult to maintain a homogeneous state in any component of a CFB system because of flow instabilities [3]. For instance, some complex structures including the choking phenomenon and regime transitions occur frequently in a riser. Second, the flow dynamics in any sub-reactor is subjected to the pressure balance and mass conservation in the whole system. Thus, any change in one sub-reactor may affect the flow behavior in the remaining zones to a certain extent. Hence, quantifying these hydrodynamic complexities and their interactions are key challenges during the design, scale-up, and optimization of multi-loop CFB reactors. S
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