Gas back-mixing studies in membrane assisted bubbling fluidized beds

S.A.R.K. Deshmukh, M. van Sint Annaland, J.A.M. Kuipers

Research output: Contribution to journalArticleAcademicpeer-review

24 Citations (Scopus)

Abstract

Fluidized beds employing fine powders are finding increased application in the chemical and petrochemical industry because of their excellent mass and heat transfer characteristics. However, in fluidized bed chemical reactors axial gas back mixing can strongly decrease the conversion and selectivity. By insertion of membranes in fluidized beds large improvements in conversion and selectivity can be achieved, firstly by optimizing axial concentration profiles via distributive feeding of one of the reactants or selective withdrawal of one of the products, and secondly, by decreasing the effective axial dispersion via compartmentalization of the fluidized bed. Moreover, insertion of membrane bundles in a suitable configuration impedes bubble growth, thereby reducing reactant by-pass via rapidly rising large bubbles. In this work the influence of the presence and configuration of membrane bundles and the effect of gas addition via the membranes on the effective axial dispersion was studied experimentally. Steady state concentration profiles were measured where a CO2-tracer was injected at different locations through a probe (point injection) or via the membranes (line injection) into a square fluidized bed View the MathML source containing glass particles (75–View the MathML source, 2550 kg/m3) fluidized with nitrogen distributed via a porous plate. Different bed configurations, viz. without internals, with vertical or horizontal membrane bundles were investigated and the effects of overall fluidization velocity and gas flow ratio of gas fed through the membrane bundles and the porous plate distributor were studied. Experimental results revealed that the insertion of vertical and horizontal membrane bundles decreases the effective axial dispersion considerably compared to a bed without internals. The point injection experiments indicated the importance of a non-uniform lateral emulsion phase velocity profile. The line injection experiments clearly pointed out the importance of bubble-to-emulsion phase mass transfer limitations. Gas addition through the membrane bundles decreases the effective axial gas dispersion enormously by almost annihilating the solids down flow along the walls and by decreasing the average bubble size and bubble fraction.
Original languageUndefined
Pages (from-to)4095-4111
JournalChemical engineering science
Volume62
Issue number15
DOIs
Publication statusPublished - 2007

Keywords

  • METIS-245334
  • IR-68770

Cite this

Deshmukh, S. A. R. K., van Sint Annaland, M., & Kuipers, J. A. M. (2007). Gas back-mixing studies in membrane assisted bubbling fluidized beds. Chemical engineering science, 62(15), 4095-4111. https://doi.org/10.1016/j.ces.2007.04.034
Deshmukh, S.A.R.K. ; van Sint Annaland, M. ; Kuipers, J.A.M. / Gas back-mixing studies in membrane assisted bubbling fluidized beds. In: Chemical engineering science. 2007 ; Vol. 62, No. 15. pp. 4095-4111.
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Deshmukh, SARK, van Sint Annaland, M & Kuipers, JAM 2007, 'Gas back-mixing studies in membrane assisted bubbling fluidized beds' Chemical engineering science, vol. 62, no. 15, pp. 4095-4111. https://doi.org/10.1016/j.ces.2007.04.034

Gas back-mixing studies in membrane assisted bubbling fluidized beds. / Deshmukh, S.A.R.K.; van Sint Annaland, M.; Kuipers, J.A.M.

In: Chemical engineering science, Vol. 62, No. 15, 2007, p. 4095-4111.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Gas back-mixing studies in membrane assisted bubbling fluidized beds

AU - Deshmukh, S.A.R.K.

AU - van Sint Annaland, M.

AU - Kuipers, J.A.M.

PY - 2007

Y1 - 2007

N2 - Fluidized beds employing fine powders are finding increased application in the chemical and petrochemical industry because of their excellent mass and heat transfer characteristics. However, in fluidized bed chemical reactors axial gas back mixing can strongly decrease the conversion and selectivity. By insertion of membranes in fluidized beds large improvements in conversion and selectivity can be achieved, firstly by optimizing axial concentration profiles via distributive feeding of one of the reactants or selective withdrawal of one of the products, and secondly, by decreasing the effective axial dispersion via compartmentalization of the fluidized bed. Moreover, insertion of membrane bundles in a suitable configuration impedes bubble growth, thereby reducing reactant by-pass via rapidly rising large bubbles. In this work the influence of the presence and configuration of membrane bundles and the effect of gas addition via the membranes on the effective axial dispersion was studied experimentally. Steady state concentration profiles were measured where a CO2-tracer was injected at different locations through a probe (point injection) or via the membranes (line injection) into a square fluidized bed View the MathML source containing glass particles (75–View the MathML source, 2550 kg/m3) fluidized with nitrogen distributed via a porous plate. Different bed configurations, viz. without internals, with vertical or horizontal membrane bundles were investigated and the effects of overall fluidization velocity and gas flow ratio of gas fed through the membrane bundles and the porous plate distributor were studied. Experimental results revealed that the insertion of vertical and horizontal membrane bundles decreases the effective axial dispersion considerably compared to a bed without internals. The point injection experiments indicated the importance of a non-uniform lateral emulsion phase velocity profile. The line injection experiments clearly pointed out the importance of bubble-to-emulsion phase mass transfer limitations. Gas addition through the membrane bundles decreases the effective axial gas dispersion enormously by almost annihilating the solids down flow along the walls and by decreasing the average bubble size and bubble fraction.

AB - Fluidized beds employing fine powders are finding increased application in the chemical and petrochemical industry because of their excellent mass and heat transfer characteristics. However, in fluidized bed chemical reactors axial gas back mixing can strongly decrease the conversion and selectivity. By insertion of membranes in fluidized beds large improvements in conversion and selectivity can be achieved, firstly by optimizing axial concentration profiles via distributive feeding of one of the reactants or selective withdrawal of one of the products, and secondly, by decreasing the effective axial dispersion via compartmentalization of the fluidized bed. Moreover, insertion of membrane bundles in a suitable configuration impedes bubble growth, thereby reducing reactant by-pass via rapidly rising large bubbles. In this work the influence of the presence and configuration of membrane bundles and the effect of gas addition via the membranes on the effective axial dispersion was studied experimentally. Steady state concentration profiles were measured where a CO2-tracer was injected at different locations through a probe (point injection) or via the membranes (line injection) into a square fluidized bed View the MathML source containing glass particles (75–View the MathML source, 2550 kg/m3) fluidized with nitrogen distributed via a porous plate. Different bed configurations, viz. without internals, with vertical or horizontal membrane bundles were investigated and the effects of overall fluidization velocity and gas flow ratio of gas fed through the membrane bundles and the porous plate distributor were studied. Experimental results revealed that the insertion of vertical and horizontal membrane bundles decreases the effective axial dispersion considerably compared to a bed without internals. The point injection experiments indicated the importance of a non-uniform lateral emulsion phase velocity profile. The line injection experiments clearly pointed out the importance of bubble-to-emulsion phase mass transfer limitations. Gas addition through the membrane bundles decreases the effective axial gas dispersion enormously by almost annihilating the solids down flow along the walls and by decreasing the average bubble size and bubble fraction.

KW - METIS-245334

KW - IR-68770

U2 - 10.1016/j.ces.2007.04.034

DO - 10.1016/j.ces.2007.04.034

M3 - Article

VL - 62

SP - 4095

EP - 4111

JO - Chemical engineering science

JF - Chemical engineering science

SN - 0009-2509

IS - 15

ER -