Analysis of the Hydrodynamic Effects of Gas Permeation in a Pilot-Scale Fluidized Bed Membrane Reactor

Chenxi Bai,Yao Xiao,Ruifeng Peng,John Grace,Yumin Chen

doi:10.3390/app9010067

Abstract

This study experimentally investigates the effects of gas extraction/addition, via multiple vertical membrane panels, on the hydrodynamics in different regions of a pilot-scale gas fluidized bed membrane reactor (FBMR), based on differential pressure signals measured at different vertical bed sections at high temperature. In a bed section where membrane panels were installed and activated, the extraction of gas caused the average bubble size to increase, but decreased the number of small- and medium-sized bubbles. This effect of gas extraction penetrated into bed sections above the active membrane panel, but attenuated with increasing distance away from the extraction location. The attenuation rate was much faster in FBMR with lower bed voidage, mainly due to the large decrease of the drag force exerted by gas extraction on fluidizing gas in a denser bed. With the same inlet gas velocity, gas addition favored the growth of bubbles, especially in the upper bed sections compared with operation without gas permeation. The increase of the effective fluidizing velocity was the major reason for the increase of the bubble size during gas addition. These findings preliminarily suggest that membrane units should not be installed in or below fast-reacting zones in a scale-up FBMR, and operation with a lower bed voidage is preferable to avoid the formation of large bubbles enhanced by gas extraction.

Highlights

Fluidized bed membrane reactors (FBMRs) have gained increasing interest as one of the promising technologies to facilitate process intensification, by combining the selective removal of reaction products or the addition of reactant via membranes with the advantages of fluidized bed reactors
The increase the average size caused by gas addition, especially in the bed section above the addition locations, was mainly bubble size caused by gas addition, especially in the bed section above the addition locations, was attributed to the increase of the superficial gas velocity the bed.inGas into the bedinto firstthe formed mainly attributed to the increase of the superficial gasinvelocity theinjected bed
This work presented experimental studies on the effects of gas extraction/addition on the hydrodynamics in a pilot-scale FBMR, with vertical porous membrane panels installed in an orderly way along the height of the reactor

Summary

Introduction

Fluidized bed membrane reactors (FBMRs) have gained increasing interest as one of the promising technologies to facilitate process intensification, by combining the selective removal of reaction products or the addition of reactant via membranes with the advantages of fluidized bed reactors. Dense metal membranes have been widely used for product in situ separation, especially, for ultra-pure hydrogen production by hydrocarbon reforming in fluidized bed reactors. Partil et al [4], Chen et al [5], Andrés et al [3], Roses et al [1] and Arratibel et al [6] experimentally investigated the subject of hydrogen production in a FBMR by steam or autothermal reforming of methane, with in situ removal of hydrogen via Pd-based dense membranes. H2 permselective membranes have been used in a fluidized bed reactor to promote the hydrogen yield in the water–gas shift reaction [2], steam reforming of higher hydrocarbons [7] and dehydrogenation reaction [8].

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