Statistical model for gas holdup in flotation column in presence of minerals

Abstract

Gas holdup has been widely considered as potential parameter for the performance prediction of flotation column. However, knowledge about gas holdup in presence of solids is still scarce. This paper presents the relationship of gas holdup with various input parameters in the collection zone of a laboratory flotation column. A 24 factorial design was successfully applied to predict the collection zone gas holdup of flotation column using coal and sphalerite at various experimental conditions in comparison with dimensional analysis. Gas velocity, slurry velocity, feed slurry concentration and mineral types were considered as input parameters. Experiments were conducted in a continuously operating Perspex column (0·1 m diameter and 1·66 m height). In this study, gas holdup was measured by phase separation method. Experimental results showed that gas holdup was affected by both air and feed flow rates. It was observed that addition of solid decreased the gas holdup because of higher slurry viscosity. Rate of decrease in gas holdup increased with solid concentration. Furthermore, hydrophilic particles showed reduction in gas holdup. A few tests were conducted under predetermined flotation conditions in order to prove the validation of the empirical and statistical model and to compare their performance. The predicted and experimental values of the desired output variables were compared and a good correlation coefficient (0·93) was also obtained. The sensitivity analysis was also performed to determine the most significant input parameter. The results showed that gas flow rate followed by solid concentration were the most significant parameters. Limitations of the present models were discussed and comments as well as recommendations were given. The developed statistical model was also found to be useful in predicting the gas holdup at any given experimental condition.