Investigation of Gas Hold-Up and Bubble Behavior in A Split-Cylinder Airlift Reactor: Pseudo-Plastic Non-Newtonian Fluids

In this research, the effect of carboxy methyl cellulose (cmc) addition into pure wateras pseudo-plastic non-newtonian fluid and its concentration on bubble diameter andgas hold-up were investigated. for this purpose, four different concentrations of cmc(0.05, 0.1, 0.15 and 0.2 w/v%) as the non-newtonian fluid and five different superficialgas velocities (0.2, 0.4, 0.6, 0.8 and 1 cm/s) as the gas phase were examined in an airliftreactor. bubble size distribution in the airlift reactor was measured by photography andpicture analysis at various concentrations of cmc and various velocities of gas.increasing in gas velocity created a wider bubble size distribution and thereby anincrease in bubble diameter and gas hold-up in both riser and down-comer. however,the bubbles diameter in pure water was larger than those of the cmc solutions (in theriser and down-comer), but cmc concentration enhancement increased bubblesdiameter and gas hold-up in the down-comer. bubbles diameter expansion in the riserby cmc concentration enhancement took place from concentrations of 0.05 to 0.15(w/v)% and then it suddenly decreased. furthermore, gas hold-up decreased fromconcentrations of 0.05 to 0.15 (w/v)% and increased at concentration of 0.2 (w/v)%.the gas hold-up increases (more than that in the concentrations of 0.1 and 0.15%)when bubbles diameter decreases in concentration of 0.2%. the overall gas hold-uptrend was similar to the gas hold-up in the riser.