BUBBLE BEHAVIOR AND ABSORPTION RATE IN GAS INJECTION THROUGH ROTARY LANCES

Bubble behaviour and absorption rate of gas injected into a liquid bat h through rotary L-shaped lances were studied by cold models. A high-s peed video recording system was used to measure the bubble diameter an d the rising velocity. The absorption rate of injected CO2 gas in aque ous NaOH solution was measured by using a pH meter. It is found that t he lance rotation leads to a decrease in the bubble diameter and the r ising velocity as compared with the stationary lance. The bubbles prod uced 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 l ance 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 ra te. The multi-hole lance can increase the volumetric mass transfer coe fficient by about three times larger than the single-hole lance. The r esults are discussed in terms of the bubble coalescence, mass transfer coefficient and total interfacial area between bubbles and liquid.