HYDRODYNAMIC STUDIES OF AN ADVANCED FLUIDIZED-BED BIOREACTOR FOR DIRECT INTERACTION WITH COAL

Fine coal particles fluidized by the upflow of a liquid medium contain ing a dissolved biocatalyst undergo size reduction as the reaction pro gresses. Three aspects of the design of such a reactor were examined: (1) the use of force balances to describe pressure drop for the segreg ated bed; (2) measurement of liquid-phase dispersion coefficients; and (3) fluorescent tagging of particles to track size distribution. Hydr odynamic data were obtained for a liquid-solid fluidized bed of coal p articles in the size range 30-150 mum. Illinois No. 6 coal was ball-mi lled, sieved into four fractions, and suspended in a 0.1% aqueous solu tion of Tween 80. A sample with a bimodal particle size distribution c entred on 49 and 63 mum was placed in a glass column and fluidization and pressure-drop data were compared with a new model developed to des cribe particle segregation. Measured liquid-phase dispersion coefficie nts varied from 0.034 to 0.283 cm2 s-1 as the flow varied from 0.005 t o 0.01 59 cm s-1. A technique was also developed for coating coal part icles with a fluorescent paint which may allow direct measurement of t he change in the fraction of marked particles of known size along the axis of a fluidized bed.