Influence of Flotation Cell on Gold Recovery
Once the most favorable operating conditions have been determined, the metallurgist must analyze and select the flotation cell with the required characteristics to produce acceptable gold recovery. The performance of the flotation cell is influenced by its design, and the main variables of the design are impeller rotational speed, air flow rate and impeller diameter. Basically, the most favorable chemical conditions are determined in the testing program. It has been noted that with any gold ore, operating conditions and flotation cell, the final concentrate and gold recovery are based on the impeller speed and air flow rate.
Essentially, in order to maintain the concentrate grade at an acceptable high level, it is necessary that the impeller speed and air flow rate to lie within certain limits and similarly with gold recovery. Nevertheless, the ranges of impeller speed and air flow rate for gold grade on the one hand and recovery on the other are rarely the same. Selecting the single impeller speed and single air flow rate, operational settings is an optimization problem. It has been established that impeller speed and air flow rate are considered as fixed and the flotation cell is operated as standardized by the manufacturer with no much attempt at variation to seek better settings. Besides, determining the relation between design parameters and gold operation objectives, it is important to consider economic factors such as mining, milling, transport and smelting cost, penalties, gold ore value. Optimization is basically a procedure of compromise between gold grade and gold recovery, each weighed by economical aspects.
It has been noted in several gold flotation plants that the optimum values of impeller speed and air flow rate should make a profitable gold operation. In order to do to this, it is important to take the highest possible values and the variation of both parameters must be in similar proportion. Obviously, the basic requirements are governed by the chemistry of the process, kinetics and mechanical design, depending upon choice and amount of flotation reagent, throughput and residence time.