Mineral Processing

Main objective of mineral processing in mining industry is to extract and to recover metals from its mineral occurrence in ore. Metals recovered are valuable and economically in mining projects. For example, gold mining operations take and send ore to processing plant to get gold as metal from rock. Mining processing is downstream industry in integrated mining industry system. It consist to several processes from liberation processing to metallurgical extraction or refining. This industry is commonly separated from mining operation process in the field. In projects, company could mine from certain rich resources country and send ores out of mining area as raw materials to be processed. These are known as raw materials exported products in several mining countries like Chile, Peru or Indonesia. Mineral processing is also main process in mining industry which could not be neglected its contribution for countries’ income. Nowadays, mineral processing concepts are used to recycling industries to extract metals from scraped products or also known as urban mining. 

Mining MES

Technology in mineral processing is developing more and more. The challenges given to recover as many as possible metals from any kinds of ore grade in economically project are encouraging technology to be researched and to be applied later. The technology itself could be divided based on processes from comminution (crushing-grinding), screening-classification (separation-extraction and concentration), to concentrate and metallurgical treatment (including refining). Each process has different technology development. Comminution process is to liberate or to unlock mineral from ores before separation. Rod mill, Ball mill and SAG mill as examples are combining in comminutioning process based on particle size and hardness after crushing. Rod mills are suitable for preparation of feed to gravity concentrators, certain flotation processes, magnetic cobbing and ball mills. Actual diameters in use for rods range from 25 to 150mm.  The  smaller the  rods the  larger  is  the  total  surface  area  and  hence  the greater  is  the  grinding  efficiency. Rod  mills  are  normally  run  at  between  50  and 65%  of  the  critical  speed. The  feed  pulp  density  is  usually between  65  and  85%  solids  by  weight,  finer  feeds requiring  lower  pulp  densities. Ball mills. It is final stage of comminution using steel balls as grinding medium, known as ball mills. This is capable for fine grinding finishing because of greater surface area per unit weight than rod mill. The balls could be stone (pebbles, like South African gold mines) or metal which grinds materials by friction and impact with the tumbling balls. Balls has ratio length to diameter about 1 – 1.5 only. 

Based on explanation below, there are several point different among them. Crushing is usually undertaken in dry process and several processes in reduction sizes. Grinding could be done in dry and wet process to provide slurry feed for concentration process. For classification process is to separate mixture of minerals products. Classification is a method of separating mixtures of minerals into 2 or more products on the basis of velocity with which the grain fall through a fluid medium in which is influenced by size, specific gravity and shape of particles.  (Heiskanen, 1993). This is usually applied to minerals which are too fine to be separated by screening. In classification principles, there are two things important influenced namely free settling and hindered settling. Free settling refers to total volume of sinking of particles in volume of fluid. Newton’s law and Stoke’s law are related directly to free settling understanding about velocity factors in different particles size. Hindered settling refers to effects of reducing size effects and increasing density effect on classification. This ratio is always greater than free settling ratio.  These two settlings influence classifier types designed and built to get the most effective one.

The separation could be in many technologies like gravity separation, dense medium separation (DMS), flotation, magnetic separation, electrostatic separation, shape separation and leaching-extraction. Separation is chosen or classified to several factors related physical-chemical characteristics of feed. In metallurgical treatment, processes are classified into pyrometallurgy and hydrometallurgy chosen based on mineral types, like oxide mineral or sulphide mineral. For examples are flotation and solvent extraction-electron winning (SX-EW) in copper processing. Refining is a process to refine and to produce metals as 99.99% quality. All processes in mineral processing are subject to get as many as possible recovered metals economically.

Simplified schematic of an SX plant using Mixer-Settlers (source: postmixing.com)