Three-dimensional multiphase full-loop simulation of directional separation of binary particle mixtures in high-flux coal-direct chemical-looping combustion system--颗粒学报PARTICUOLOGY

Wang, X., Shao, Y., Jin, B., & Zhang, Y. (2020). Three-dimensional multiphase full-loop simulation of directional separation of binary particle mixtures in high-flux coal-direct chemical-looping combustion system. Particuology, 49, 179-190. https://doi.org/10.1016/j.partic.2019.04.004

Three-dimensional multiphase full-loop simulation of directional separation of binary particle mixtures in high-flux coal-direct chemical-looping combustion system

Xiaojia Wang ^*, Yali Shao, Baosheng Jin, Yong Zhang

Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education, School of Energy & Environment, Southeast University, Nanjing 210096, China

10.1016/j.partic.2019.04.004

Volume 49, April 2020, Pages 179-190

Received 17 July 2018, Revised 27 January 2019, Accepted 18 April 2019, Available online 2 July 2019, Version of Record 26 February 2020.

E-mail: xiaojiawang@seu.edu.cn

Highlights

• 3D Eulerian–Eulerian full-loop model for simulating circulation and separation was developed.

• High-flux directional separation mechanisms of binary particle mixtures during CDCLC were studied.

• Effects of operating variables on separation performance of the high-flux carbon stripper were investigated.

Abstract

Coal-direct chemical-looping combustion (CDCLC) is a promising coal combustion technique that provides CO₂ capture with a low energy penalty. In this study, we developed a three-dimensional Eulerian–Eulerian multiphase full-loop model for simulating the circulation and separation of binary particle mixtures in a novel high-flux CDCLC system. This model comprised a high-flux circulating fluidized bed as the fuel reactor (FR), a counter-flow moving bed as the air reactor (AR), a high-flux carbon stripper, two downcomers, and two J-valves. This model predicted the main features of complex gas–solid flow behaviors in the system. The simulation results showed that quasi-stable solid circulation in the whole system could be achieved, and the FR, AR, and J-valves operated in a dense suspension upflow regime, a near-plug-flow regime, and a bubbling fluidization regime, respectively. The multiphase flow model of binary particle mixtures was used to predict the mechanisms of directional separation of binary particle mixtures of an oxygen carrier (OC) and coal throughout the system. A decrease in the baffle aspect ratio of the inertial separator improved the coal selective separation efficiency but resulted in a slight decline in the OC selective separation; this is believed to be the result of weakening of particle collisions with the baffle. A higher FR gas velocity had a slightly negative effect on the OC selective separation efficiency, but improved the coal selective separation efficiency; this can be attributed to an increase in the particle-carrying capacity of the gas stream. A decrease in the coal particle size led to better entrainment of the coal particles by the gas stream and this increased the coal selective separation efficiency. In real CDCLC applications, the operating variables for separation of binary particle mixtures should be comprehensively assessed to determine their positive and negative effects on the carbon capture efficiency, OC regeneration efficiency, gas leakage restraint, energy consumption, and fuel conversion.

Graphical abstract

Keywords

Coal-direct chemical-looping combustion; Binary particle mixture; Carbon stripper' Separation; Full loop; Simulation

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