Transfer dynamics and reaction control mechanisms over methanation catalyst particles in transport bed

CHENG Yonggang1,2 LIU Jiao1 HAN Zhennan3 SHI Lei3 XU Guangwen1,3

(1.Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China 100190)
(2.University of Chinese Academy of Sciences, Beijing, China 100049)
(3.Shenyang University of Chemical Technology, Shenyang, Liaoning Province, China 110142)

【Abstract】The numerical simulation based on COMSOL Multiphysics was conducted to understand the dynamics of heat transfer and mechanism of reaction control over methanation catalyst particles in the size of about 100 μm under conditions of a transport bed. The high heat transfer efficiency in a transport bed makes the catalyst particle into the bed quickly approach its steady state in about 0.1 s, a very short transient period. For the catalyst particle in a steady state, there are temperatures sharing little difference among the particle center, particle surface, and gas flow bulk. However, it is clear that the temperature is still gradually lower from the center to the surface of the particle, and on the particle surface, its temperature is higher than that in fluid. This clarifies that the exothermic heat of methanation reaction first heats the catalyst particle, and the temperature-raised particle then reaches a balance of heat transfer with its surrounding gas. The calculation of the radial profiles of the temperature, gas components, and reaction rate inside the catalyst particle clarifies that for methanation at higher fluid temperature and elevated pressure (2 MPa here), the mass transfer into particles is quicker, and the CO consumption rate becomes gradually lower from the center to the surface of the particle. On the contrary, for atmospheric methanation at lower gas velocity, the reaction rate is conversely lower at the particle center. It demonstrates that the methanation reaction is subject to kinetic control for the former but to mass transfer for the latter.

【Keywords】 transport bed; methanation; coal-to-SNG; numerical simulation; heat transfer; dynamic behavior; reaction mechanism;

【Funds】 National Key R&D Program of China (2018YFB0604503)

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(Translated by HAN R)

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This Article

ISSN:0438-1157

CN: 11-1946/TQ

Vol 70, No. 08, Pages 2876-2887

August 2019

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Article Outline

Abstract

  • Introduction
  • 1 Model of reaction with a single catalyst particle
  • 2 Results and discussion
  • 3 Conclusion
  • Symbol description
  • References