Abstract
Liquid holdup and wetting efficiency are essential parameters for design of trickle bed reactors. Both parameters play an important role in reactor performance including pressure drop, conversion, and heat transfer. Empirical formulas are usually employed to calculate liquid holdup and wetting efficiency. However, factors such as particle shape and the wetting ability of liquid on the particle surface are not described clearly in traditional formulas. In this paper, actual random packing was built by DEM and CFD simulations were performed to investigate the factors affecting liquid holdup and wetting efficiency in trickle bed reactors, including particle shape, surface tension, contact angle, liquid viscosity, liquid density, liquid, and gas superficial velocity. Detailed fluid flow and liquid-solid interaction were described by VOF model. Four different particle shapes were investigated. It showed the particle shape has great effect and the 4-hole cylinder packing gained both highest liquid holdup and wetting efficiency. The overall simulations gave a detailed description of phase interactions and fluid flow in the voids between catalyst particles and these results could give further guidance for the design and operation of trickle bed reactors.
Highlights
The gas-liquid-solid three-phase catalytic reaction is a common reaction type in chemical engineering
The phase interaction between gas, liquid, and solid in trickle bed reactors (TBRs) makes the hydrodynamic phenomena quite complicated, which is usually investigated by experimental method [2,3,4]
The computational fluid dynamics (CFD) simulation was employed with the volume of fluid (VOF) method to investigate the factors affecting liquid holdup and wetting efficiency in a trickle bed reactor
Summary
The gas-liquid-solid three-phase catalytic reaction is a common reaction type in chemical engineering. Du et al performed CFD simulations on regular particles arrangement within a rectangular domain to investigate the local wetting behavior in a TBR [6,16] Simulations performed by both groups modeled particles with regular configuration and fixed distance between each other, which is difficult to achieve in a real reactor where catalyst particles are packed randomly, and the particle’s shape can be complex such as a cylinder or hollow cylinder. Their grid resolution are not high enough to give clear descriptions of the liquid flow configuration on the discrete particle surfaces. The CFD simulation was employed with the volume of fluid (VOF) method to investigate the factors affecting liquid holdup and wetting efficiency in a trickle bed reactor. This research can give guidance in trickle bed reactor design and operation in the future
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