Mineral Processing Equipment

With metals almost perpetually in a state of oversupply and prices outside the control of producers, the only way to be alert is produce under optimal conditions which are directly influenced by the type of equipment used at the processing plant.

The use of large equipment and new technologies have profoundly influenced concentrator design and operating philosophy and also contributed to have lower concentrator costs or al least maintain a dynamic equilibrium. Crushing and grinding are by far the largest consumers of power in a concentrator. Phasing start-ups reduces peak demand and running crushers and mill at full power maximizes throughput and makes the most efficient use of installed horsepower.

Without any doubt, advances in process control have been responsible for the most significant recent increases in a concentrator productivity and the on stream analyzer is probably the most important tool ever to have influenced concentrator productivity. For example, computer base control systems that change reagent addition and air volumes in accordance with grades and tonnages are excellent at keeping reagent, and flotation control strategies based primarily on altering flow rate are very effective.

The classical comminution equipment is related to crushing machines such as jaw crushers, conical and gyratory. The selection depends of the ore characteristics and the grinding equipment to be used in the next stage. Recently, has been studied with special interest the applicability of microwave devices because rapid heating of ore minerals in a microwave transparent matrix generates thermal stress of sufficient magnitude to create micro-cracks, some of which occur at mineral grain boundaries. Inducement of micro-cracking before beneficiation is likely to improve liberation.

An element very important is the grinding circuit which is constituted by SAG mills, ball mills, rod mills and cyclones. There is not a unique way to design the circuit, but he objective is to assure the liberation of valuable minerals. The rod mill has been universally available for many years, and yet in many cases has been bypassed in service by other equipment. However, the rod mill can provide better product than the newer, more sophisticated machine. The efficient grinding of different particle sizes in the feed to a ball mill requires the provision of a variety of ball sizes, each ball size maximizing the breakage of a certain particle size.

The most used concentrator equipments are gravimetric devices and flotation cells, the first are employed normally in the treatment of auriferous ores and the most recently equipment is the centrifugal concentrator which can recover fine particles of precious metals. Other gravimetric equipments are cones, spirals, and shaking tables. Flotation cells have been the most used equipment since the first years of the last century in the recovery of polymetallic ores. The design has change in some aspect during the last decades. Thus, the introduction of pneumatic cells such as the column cells and Jameson cell has been the most interesting changes in the last times. Perhaps the column cells have been employed more when the ore is clayey, but the traditional cells keep the same idea and maybe the main change has been the trend to employ cells of big volume with the only idea of save space and reduce energy costs.

Other equipments used are thickeners and filters which are used in solid-liquid separations. The latter one probably has suffer many changes since the use of disc and drum filters.