Flotation costs

Although there have been major advances in the operational aspects of flotation, selectivity, recovery, and grade have changed a little. Nevertheless, the flotation cost of obtaining these results has come down. For example, it is remarkable that most of reagents used today were or are development of reagents employed forty or fifty years ago. Most the time, in an emergency, cost cutting receives priority, in well run concentrators costs have to be kept at minimum and effort is focused at raising revenue and the most optimal method of raising throughput. More tons translate soon in more product and lower costs. It possible, even recovery can be skipped for better throughput because a considerable increase in recovery usually needed to make up the difference.

There are some factors involved in the costs of a flotation plant. Some of them are metallurgical performance, power consumption, maintenance, ore variability, reagents and auxiliary equipment. Comparative performance analysis is usually determined by direct testing of competing machines on the ore to be processed with decision based on some specific parameters. In fact less tangible factors such as ease of operation and previous experience of operator and supervisors with the equipment could enter into it. There have been several attempts to establish a rational basis for these differences, for example the mixer performance is often correlated in terms of power intensity.

The problems of flotation performance and its cost is complex. The difficulty in studying flotation cells is that they combine more individual requirements and treat more complicated systems than those practiced by other equipment. A major part of the operating cost of a flotation process is power consumption. The analysis is not easy, some researches treated to correlate flotation time and energy, and they found that there is not a relationship. This is not surprising due to the variables that affect energy consumption include no only characteristics of the machine, else auxiliary operations such as pumping and regrinding which are strictly influenced by the type of ore being treated.

Maintenance and downtime costs are vital elements in the selection of flotation equipment. Modern machines use rubber covered metal parts wherever abrasion is severe. For acid processes, acid resistant material is used. Drip proof motors are also specified so that water can not easily get into them. For any particular installation, estimated maintenance costs or the actual costs of plant scale tests could be compared.

The ore variability is related to variation of ore quality and variation of the tonnage sent to flotation. Sometimes, the valuable mineral in the ore varies sufficiently that the operative parameters are altered drastically without good results. Changes in grade usually results from variations at the mine and from segregation in stockpiles. Variation in tonnage is caused by changes in the capacity of grinding due to the hardness of the ore. To maintain concentrate grades and recoveries in the face of variation in mineral content or feed, or even worse, both at the same time, can require change flotation time and reagent dosage. However, is important to remember that the reagent dosage is not directly proportional to tonnage or mineral content, and this is the reason because some flotation operations have bad results when employ automatic devices or complex algorithms to add reagents to the flotation circuit. Reagents are added considering technical criterium and not mathematical formulas.