Modeling and Optimizing of Mechanically Agitated Vessels by Central Composite Rotatable Design Method

A central composite rotatable design (CCRD) methodology was used to analyze the effect of some operating variables on gas-liquid two phase mixing time in an agitated tank driven by dual 6-blade Rushton turbines. The variables chosen were the impellers rotational speed (x1), gas flow rate (x2), probe location (x3) and tracer injection point (x4). The mathematical relationship of mixing time on the four significant independent variables can be approximated by a nonlinear polynomial model. Predicted values were found to be in good agreement with the experimental values (R-sq of 95.9 percent and R-Sq (Adj) of 95.7 percent for response Y). This study has shown that central composite design could efficiently be applied for the modeling of mixing time, and it is an economical way of obtaining the maximum amount of information with the fewest number of experiments.