Bubble Behaviour and Absorption Rate in Gas Injection through Rotary Lances.

Abstract

Bubble behaviour and absorption rate of gas injected into a liquid bath through rotary L-shaped lances were studied by cold models. A high-speed video recording system was used to measure the bubble diameter and the rising velocity. The absorption rate of injected CO2 gas in aqueous NaOH solution was measured by using a pH meter. It is found that the lance rotation leads to a decrease in the bubble diameter and the rising velocity as compared with the stationary lance. The bubbles produced by a multi-hole lance are smaller than those produced by a single-hole lance. The reduction in the bubble rising velocity is connected with the decrease in the bubble diameter, distribution of bubbles over the liquid bath and distortion of the bubble rising path due to the lance rotation. The gas absorption rate for the rotary lances is larger than that for the stationary lance. The effect of the rotation speed on volumetric mass transfer coefficient is larger at lower gas flow rate. The multi-hole lance can increase the volumetric mass transfer coefficient by about three times larger than the single-hole lance.The results are discussed in terms of the bubble coalescence, mass transfer coefficient and total interfacial area between bubbles and liquid