Spread-Sheet Based Modeling of Coal Flotation Circuits - Case Study:The Zarand Coal Washing Plant

One of the problems of flotation circuit of the Zarand coal washing plants like other processing plants is the wide variations in feed characteristics. By modeling flotation circuit, the effect of feed variation on the metallurgical parameters (yield and ash content) could be predicted and necessary measures then can be taken to achieve the desired targets. To perform this task, the first order kinetics model with distributed rate constants based on particles size classes was used. The characteristics of feed species and pulp residence time distribution in each flotation bank were among the main variables involved in the modeling. A tracer method using salt was utilized to determine the pulp residence time distribution. The average residence times for rougher, scavenger, and cleaner stages were found to be 6.6, 9.6 and 12.6 min, respectively. Based on flotation tests, the feed was grouped into five species namely, fast-floating non-ash, slow floating non-ash, fast floating ash, slow floating ash, and non-floating ash and non-ash. Modeling was performed considering the contribution of each species and corresponding rate constants. The verification of the modeling results indicated that estimated metallurgical parameters were in good agreement with the plant data. It was found that with a 95% confidence the absolute difference between the calculated and plants values were 1.37-5.7% for yield and -0.9-0.4 % for the concentrate ash content.