Measurement of gas hold-up profiles in bubble column by gamma ray tomography: effect of liquid phase properties

Abstract

Radial variation of the gas hold-up was investigated in 0.385 m ID bubble column using gamma ray tomography. Radial profiles were measured at three axial locations (H/D = 0.259, 3 and 5). Two types of liquid phase were selected, one was coalescence inhibiting (aqueous solution of butanol) and the other coalescence promoting (aqueous solution of carboxyl methyl cellulose). Respectively, these systems offered higher and lower values of fractional gas hold-up as compared to the air-water system under otherwise identical conditions. Superficial gas velocity was varied from 0.06 to 0.3 ms⁻¹. Perforated plates were used as spargers. Three perforated sparger plates of same free area (FA = 0.42%) was used and hole diameters (d₀) were 1mm, 3 mm and 25 mm. The hold-up profiles were found to depend strongly on the sparger design for an air-alcohol solution up to the axial location of height to diameter ratio (H/D) of 3. Whereas for air-water and CMC solutions, the dependence on H/D ratio was progressively less. Further, the height of dispersion was found to influence the hold-up profiles near the sparger. All the results have been correlated on the basis of the drift flux model.