Hydrodynamic studies of an advanced fluidized-bed bioreactor for direct interaction with coal

Abstract

Fine coal particles fluidized by the upflow of a liquid medium containing a dissolved biocatalyst undergo size reduction as the reaction progresses. Three aspects of the design of such a reactor were examined: 1. (1)the use of force balances to describe pressure drop for the segregated bed; 2. (2) measurement of liquid-phase dispersion coefficients; and 3. (3) fluorescent tagging of particles to track size distribution. Hydrodynamic data were obtained for a liquid-solid fluidized bed of coal particles in the size range 30–150 μm. Illinois No. 6 coal was ball-milled, sieved into four fractions, and suspended in a 0.1% aqueous solution of Tween 80. A sample with a bimodal particle size distribution centred on 49 and 63 μm was placed in a glass column and fluidization and pressure-drop data were compared with a new model developed to describe particle segregation. Measured liquid-phase dispersion coefficients varied from 0.034 to 0.283 cm 2 s −1 as the flow varied from 0.005 to 0.0159 cm s −1. A technique was also developed for coating coal particles with a fluorescent paint which may allow direct measurement of the change in the fraction of marked particles of known size along the axis of a fluidized bed.