CFD simulation of pressure fluctuation characteristics in the gas-solid fluidized bed: Comparisons with experiments

Abstract

A simple hydrodynamic model based on two-fluid theory, taking into account the effect of discrete particles on both the gas-and solid-phase momentum equations, was used to numerically investigate the pressure fl uctuation characteristics in a gas-solid fl uidized bed with the aid of CFX 4.4, a commercial CFD software package, by adding user-defi ned Fortran subroutines. Numerical simulations together with typical experimental measurements show that pressure fluctuations originate above the distributor when a gas pulse is injected into the fl uidized bed. The pressure above the bubble gradually increases due to the presence of a rising bubble. When the bubble passes through the bed surface, the pressure near the bed surface gradually decreases to a lower value. Moreover, the pressure signals in the bubbling fluidized beds show obviously periodic characteristics. The major frequency of pressure fluctuations at the same vertical position is affected slightly by the operating gas velocity, and the amplitude of pressure fl uctuations is related to both the operating gas velocity and the vertical height. In this study, the infl uence of the operating gas velocity on the pressure wave propagation velocity can be ignored, and only two peak frequencies in the power spectrum of the pressure fl uctuations are observed which are associated with the bubble formation above the distributor and its eruption at the bed surface.pressure fl uctuations, pressure wave velocity, pressure fl uctuation frequency CFD simulation of pressure fl uctuation characteristics in the gas-solid fl uidized bed: Comparisons with experiments

Non-uniform fluidization in auto-oscillating mode

“…Сalculation of the hydraulic resistance in a fluidized bed caused by overcoming the friction forces between solid particles and the friction due to motion of gas was carried out according to the proposed author [14,[16][17][18][19][20][21][22] by the expression:…”

“…Hydraulic resistance of a fluidized bed was determined by the expression proposed by authors [14,[16][17][18][19][20][21][22]:…”

“…where Н і -value of a fluidized bed height at a certain time τ і , m. Unlike to [14,[16][17][18][19][20][21][22], hydrostatic pressure is determined by taking into account the physical model:…”

Simulation on hydrodynamics of non-spherical particulate system using a drag coefficient correlation based on artificial neural network

“…In the petroleum industry, multiphase flow (Li et al, 2019;Shi et al 2019;Yang et al 2019), heat transfer (Yin et al 2018), and mass transfer (Zhu et al 2018) are widely existed. As a typical multiphase flow system, fluidized bed reactor plays a significant role in the development of the petroleum industry (Zhang 2009;Pei et al 2009), such as fluid catalytic cracking (Wang et al 2011), coking (Wang et al 2016), combustion of petroleum coke (Zhang et al 2012), pyrolysis process (Gao et al 2013), etc. There are various complex processes in a fluidized bed reactor, involving complicated multiphase flow, heat transfer, and chemical reactions.…”

CFD investigation of slugging behavior in a gas-solids fluidized bed

“…Lettieri et al [1,17] Based on the inviscid two-fluid model of Gidaspow [21], Brandani and Zhang [22] proposed a hydrodynamic model by introducing additional terms into both gas-and solid-phases momentum balance equations. Series of simulations were implemented to explore the fluidization characteristics, such as homogeneous fluidization of Geldart group A particles, bubbling and collapsing behavior for Geldart group B particles, and the pressure fluctuation characteristics in the gas-solid fluidized bed [23][24][25]. The gas viscosity item was ignored in the gas phase momentum equation when an additional term was taken into account and the relatively low operational gas velocity was used in the homogeneous or bubbling fluidization regime.…”