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The permeability of wood-chip beds: The effect of compressibility

Authors

  • M. Alaqqad,

    Corresponding author
    1. Department of Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, BC, Canada V6T 1Z3
    • Department of Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, BC, Canada V6T 1Z3.
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  • C. P. J. Bennington,

    1. Department of Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, BC, Canada V6T 1Z3
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    • Deceased.

  • D. M. Martinez

    1. Department of Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, BC, Canada V6T 1Z3
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Abstract

In this work, we present a methodology to characterise the permeability of a compressible bed of wood chips under mechanical load. We show that under the limiting condition of when the mechanical compression is large in comparison to hydraulic pressure the equations of motion can be linearised and solved to produce an expression approximating the variation in porosity along the length of the bed. We show how this may be used, in conjunction with multiple linear regression to estimate permeability of the bed. In the experimental portion of the work we measure the permeability of a bed of hemlock wood chips at three different kappa numbers κ, and compacted to three different mechanical loads, i.e. compaction pressures pc. The usefulness of these estimates was then tested by predicting the pressure drop versus flow relationship for conditions outside the range of the linearised solution; the equations of motion were solved numerically with knowledge of the measured permeability. Good agreement was obtained. After accounting for compressibility effects, we find that our correlation has lower flow resistances than the literature correlations. © 2011 Canadian Society for Chemical Engineering

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