The selection of flotation cells must follow a detailed and rigorous process considering technical and economical aspects. Nowadays, large flotation cells are the appropriate option for a new gold flotation plant and at existing plants due to they offer an economic way of increasing capacity and reducing operating costs. Basically, large flotation cells have the benefit of lower capital costs per unit volume and installation costs are lower because fewer units need less space, fewer mechanism also make for lower maintenance costs and power requirements. It is well known that flotation cells are classified into open flow and cell to cell designs and as to whether the air is naturally aspirated or generated by an external blower. Other classification mentions pneumatic flotation cells using air for flotation and slurry suspension. Column cells belong to this category.
It has been noted that for rougher and scavenger flotation, open flow designs have been employed in many gold flotation plants with limited capacity. The open flow cells comprise a bank of a series of independent agitators in along through. Short circuiting of particles from cell to cell is eliminated as much as possible by careful installation of baffles and tank design. Some designs include cell-to-cell machines for cleaning and they are appropriate for small operations where there are economical and operating restrictions. They have been found to yield better recovery of coarse particles, higher percent solids in the froth and better performance than open flow cells. Essentially, cell-to-cell machines have the advantage of handling high circulating load. The main disadvantage is the low efficiency when the material presents high content of fine particles such clays. In this case the concentrate grade is the weak point of the flotation performance.
Modern flotation cells for rougher and scavenger flotation employ external air and some manufacturers offer self aerating designs, but the efficiency and mechanical problems are a serious issue. For this reason designers prefer tank flotation cells with external air, despite the cost of blowers are air ducting due to external air allow a good control of the air flow rate. Without any doubt, air is the cheapest flotation reagent and the ability to accurately control air flow to flotation cells must be done carefully. In some gold operations there is an air profile that must be followed. Obviously, Metallurgist and operator experiences are important in setting the air flow. When it is difficult to prove metallurgical superiority of any flotation cell, the true test can be done operating competing cells in parallel on the same process stream. It is difficult to have this type of information and the decision is based on the experience from other operations using the flotation cell model. The flotation circuit must be designed with simplicity and no with complicated configurations. If the design is simple, the control is easy and the metallurgical performance can be optimized. All these aspects have an impact on the economy of the project or operating and must be analyzed carefully.