Metallurgical Equipment

The metallurgical equipment to be used in a mineral processing plant is chosen considering the process selected and its availability to industrial level. Usually the equipment is required for the following unitary operations: crushing, grinding, classification, concentration (gravimetry, flotation, magnetic), thickening and filtering. The type of units to be considered in the treatment of any type of ore is influenced by three aspects: characteristics and value of the ore, products to be obtained and its commercialization, and size of the plant.

The best metallurgical criterion in any process has been to recover the valuable minerals as soon as can be possible. In other words, once particles are liberated, they must be recovered. There are values that can be lost by using a fine grinding and this origin a high cost due to an unnecessary over grinding. This problem must be considered at the moment of selecting grinding equipment and a flotation machine.

The flowsheet chosen for each ore must be based on the type of separation method more effective to achieve a good recovery. In order to do this will be necessary to consider the characteristics of the final product, economical aspects influenced by the metallic content, size of the mill, and location.

Some ores only can need crushing and screening steps with equipment no sophisticated due to the natural characteristics of the ore such as hardness. There are ores treated only by classification in hydrocyclones or settling tanks and the final product is obtained without complication. If the valuable particles are liberated easily and exists an important difference in specific gravity, then grinding is no very problematic and can be employed for example a gravimetric equipment (e.g. jigs, shaking tables, centrifugal concentrators) to concentrate gold. The separation efficiency trends to be more complicated with fine particles. However, gravimetry separation is not efficient if the minerals have the same specific gravity. If that happen, the initial product requires more cleaning steps in order to achieve a product with good metallurgical characteristics.

Froth flotation has been the most employed method of concentration since the first years of the last century. The equipment necessary is the called flotation cell which has adopted some changes on its design with the only idea of achieving good concentrates. There are many brands and the industrial practical is the best parameter to consider when is necessary to select a particular type of cell.

Some specialist consider that hydrometallurgical processes are the most economical to extract specific metals. Maybe the best examples are precious metals, oxide copper ores, and uranium ores. Without considering any specific treatment, usually hydrometallurgical processes usually don’t require a previous step of concentration and the equipment has a design very simple. The equipment used usually comprises leaching tanks, clarifiers, and filter systems. As was mentioned before, practical experience is the best tool at the moment of selecting the equipment which usually must be designed to resist the corrosive attack of the leaching agent.

In general, the final flowsheet and the equipment to be selected depend mainly of economical aspects. A process with the best metallurgical performance is not necessarily the best option if not match the size of the operation. Probably, the location of the plant must be according to the market conditions. Sometimes, a small deposit requires a simple process to be economical.