PERFORMANCE OF A HOLLOW-FIBER SPIRAL DISK FOR EFFECTIVE GAS DISPERSION TOWARD HIGH-MASS TRANSFER RATE

Gas-dispersive capability of a hollow-fiber membrane, manufactured spe cifically for the use in fine bubbles generation, is tested for attain ing high gas-liquid mass transfer rate under low-gas-throughput, shall ow-sparging (at depths < 0.7 m) conditions. The hollow fiber is wound In a plane spiral form, each of which can be piled in a cylindrical mo dule. A bubble column is used in the presence as well as absence of a draft tube, which the module can fit to and serve. as part of. To enha nce the effectiveness in the module's generating fine bubbles, electro lytes are added to the liquid phase, water. Over a superficial gas vel ocity range of 0.1-2 mm/s, the hollow-fiber module (in comparison to c onventional perforated-plate distributors) demonstrates, even with mod erate gas-supply pressures (<0.3. MPa), as high as 3-fold and 20-fold increases in the volumetric mass transfer coefficient in the absence a nd presence of the electrolytes, respectively. The former has been att ained with a negligible increase in the gas holdup; the latter has acc ompanied a large (similar to 20-fold) increase in the gas holdup. Whil e in the latter case the bubbles are very finely dispersed, the draft- tube mode of operation secures still reasonable liquid circulation wit h nonclustering, spherical bubbles uniformly dispersed in each of the core and annular regions of the bubble column.