STUDY ON FINE BUBBLE DISPERSION BY GAS INJECTION IN METAL REFINING PROCESSES

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1. In the case of gas injection from the L-shaped rotary lance, (1) the mixing time decreases with increasing the rotation speed. At large gas flow rates the mixing time decreases with increasing the bath depth. (2) Gas injected through the rotary lance allows the bubbles to be distributed over the liquid bath, where they rise without acting on each other. (3) The multi-hole lance produces smaller bubbles as compared with the single-hole lance. In the range of the large rotation speed, bubble coalescence rate increases with the rotation speed. (4) The gas absorption rate increases as compared with the gas injection through the stationary lance. This occurs due to increases in the bubble-liquid interfacial area and the bubble residence time. (5) When gas is injected through the multi-hole lance, the gas absorption rate is larger by three times as compared with the single-hole lance. The use of the multi-hole lance leads to the decrease of the absorption rate in the range of the large rotation speed.2. When gas is injected through slot nozzles, (1) small bubbles are formed along the slot at discrete locations and dispersed over the liquid bath. (2) The number of bubble sources for non-wetted slot nozzle is less than observed for gas injection from wetted slot nozzle. (3) The bubble size measured experimentally is in good agreement with that calculated from Davidson and Schuler model. (4) A peaked slot nozzle produces smaller bubbles as compared with a flat slot nozzle. (5) The line of bubble formation sites along the slot generates a wide bubble plume, which may offer high efficiency for metal refining process. The present work proves that gas injection through the L-shaped rotary lances and the slot nozzles can improve the refining characteristics of the metallurgical processes.