Integrating multi-scale mass transfer model with discrete-DAEM to simulate the coal pyrolysis in a novel conical-type downer pyrolyzer--颗粒学报PARTICUOLOGY

a Shanxi Province Key Laboratory of Chemical Process Intensification, North University of China, Taiyuan, 030051, China
b Shanxi Research Institute for Clean Energy, Tsinghua University, Taiyuan, 030032, China
c College of Chemical Engineering and Technology, Taiyuan University of Technology, Taiyuan, 030024, China
d Shanxi Sanqiang New Energy Technology Co., Ltd, Taiyuan, 030051, China
e State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, 030001, China

10.1016/j.partic.2025.06.010

Volume 104, September 2025, Pages 128-138

Received 18 February 2025, Revised 27 May 2025, Accepted 23 June 2025, Available online 27 June 2025, Version of Record 3 July 2025.

E-mail: wlian@nuc.edu.cn

Highlights

• Coal pyrolysis in a novel conical-type downer pyrolyzer is firstly simulated.

• Discrete-DAEM kinetics is adopted to compromise the precision and efficiency.

• A multi-scale mass transfer model is introduced to better reflect the actual process.

• Integrated multi-scale mass transfer model with discrete-DAEM simulates coal pyrolysis.

• Potential advantages of conical-type downer pyrolyzer are verified by simulation.

Abstract

The performance of a novel conical-type downer pyrolyzer is carefully evaluated via numerical simulation. The study explicitly accounts for mass transfer effects by using a multi-scale mass transfer model. To achieve simultaneous high precision and computational efficiency, an enhanced strategy for calculating the multi-scale mass transfer coefficient in heterogeneous phase reaction systems is proposed by treating mass transfer and reaction as independent processes. This strategy is coupled with a discrete distributed activation energy model formulated in the Arrhenius framework. A comprehensive analysis is performed to investigate the axial distributions of key parameters, including the average concentration of solid reactants (X_s), the volatile concentration on particle surfaces (X_sf), and the volatile concentration in the bulk gas phase (X_f) under varying pyrolysis temperatures, carrier gas velocities, and solid mass fluxes. The findings reveal that X_s and X_f exhibit intuitive, monotonic trends, while X_sf demonstrates a more complex behavior, increasing due to ongoing reactions yet decreasing with mass transfer proceeding. The simulation results verify the advantages of the conical-type downer pyrolyzer, which can achieve significantly higher volatile concentrations than conventional designs.

Graphical abstract

Keywords

Conical-type downer; Computational fluid dynamics (CFD); Coal pyrolysis; Discrete distributed activation energy model (Discrete-DAEM); Multi-scale mass transfer model

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