Effect of sparger design and height to diameter ratio on fractional gas hold-up in bubble columns

Abstract

The combined effect of sparger design and dispersion height on fractional gas hold-up (^-ε_G) was investigated in a 0.385 m i.d. bubble column. Perforated plates were used as -spargers. Free areas of sparger plates (F. A.) and hole diameters were varied in the range of 0.13% to 5.0% and 0.8 mm to 87 mm, respectively. The height to diameter ratio (HD/D) was varied in the range of 1-8. In all the cases, the superficial gas velocity was covered in the range of 30-300 mm s^-1. In order to investigate the combined effects of sparger design and the HD/D ratio together with the coalescing nature of the liquid phase, three liquid systems were considered, namely, water, an aqueous solution of an electrolyte and an aqueous solution of carboxymethyl cellulose (CMC). The comparative behaviour of these systems has been presented. The effects of sparger design, HD/D ratio and the gas- liquid system have also been analysed on the basis of drift flux model. A predictive procedure has been given for the drift flux constants by simulating the flow pattern in bubble columns using Computational Fluid Dynamics (CFD).