Application of Box–Behnken design and response surface methodology for modeling and optimization of batch flotation of coal

ABSTRACT The focus of this research is to explore the relationship between the response functions (ash content and flotation perfect index [FPI]) and variables (collector dosage, frother dosage, and stirring speed). The Box–Behnken experimental design and response surface methodology were applied for modeling the influence of some variables on the performance of coal flotation. Flotation experiments were designed and executed by a laboratory flotation machine, considering collector dosage, frother dosage, and stirring speed as variables. Ash content and FPI were defined as process responses. The test results showed that both the models obtained for ash content and FPI were found to be statistically significant and the predicted values were in good agreement with the experimental values (R2 value of 0.8733 is for ash content and R2 value of 0.9939 is for FPI). The effects of variables on ash content and FPI were discussed and the verification experiments at optimum conditions proposed by the models were carried out to determine the validity of the predicted models. Results suggest that collector dosage plays an important role in effecting the ash content but FPI depends more on stirring speed. The maximum FPI at the desired level of ash content of 12.5% could be 39.75% when the values of collector dosage, frother dosage, and stirring speed are 1.02, 0.06 kg/t, and 1754 r/min, respectively. Based on the modeling results, exploratory experiment was conducted for further increasing the flotation performance using prestirring process. The results showed that the FPI has been increased by 1.66% using the prestirring process.