Mineral processing is the complex of the technological measures, directed on the increase of concentration of useful components in mined minerals. The mineral processing occupies intermediate position between a mining operations and subsequent processing of useful components. It is conditioned by technology of the further processing of minerals.
The necessity of mineral processing, as a rule, is related to small content of valuable component in the mined ore. For example, content of molybdenum in mined ore makes 0.06 %, while for the metallurgical processing content of molybdenum must be no less than 45%. Small concentration of valuable component lead to losses of metal in the process of metallurgical production, in addition, the enormous amount of heat-carrying agents is required. Thus, mineral processing is the operation caused by technology and economy of mineral treating.
All minerals that are exposed to processing can be divided into the following types:
1. Metallic ors containing a copper, lead, zinc, molybdenum, etc; 2. Non-metal - dolomite, sulfur ores, phosphorite, potassium salts etc, 3. Carbon containing minerals - graphite, coal, anthracite.
Concentration plants are classified on the following types depending on the type of initial mineral:
• Concentration plants for treatment ferrous metal ores and nonferrous metal ores– (in ÑIS it are ÃÎÊè, ÖÃÎÊè, ÃÌÊ)
• Coal preparation plants – (in ÑIS it are ÃÎÔ, ÖÎÔ, ÎÔ)
As a result of mineral processing the following products are got:
• A concentrate is a product containing the maximal amount of useful component;
• An intermediate product (middling) is occupying intermediate position in quality between a concentrate and wastes;
• Wastes are a product containing the minimal amount of useful component.
2 groups of indexes distinguish:
1. Characterizing the amount of the material;
2. Characterizing quality of the material and products of concentration.
Loading (Q, ò/h) it is shown in tons at hour amount of material entering operation. Output (y, %) it is shown in percents to initial material amount of product.
y = Qprod* 100/Qin, %
Quality of products of enrichment is estimated by next indexes. For coals this is:
Ash value (Àd, %), characterizes the amount of noncombustible remain after incineration of unit of mass of product. Humidity (Wr,%), characterizes content of moisture in unit of mass of product. Content sulfur is sulphureous (Sd,%), characterizes content of sulphur in coals or products of cleaning. Content of volatile matters (Vd,%) - characterizes content of hydrocarbons in a coal.
The following quality indexes is used for the coked coals:
Àdin = 25 - 40 %……initial coal; Àdc = 4 – 8 %…….. concentrate; Àdm = 35 – 45 %….. middlings; Àdw = 75 – 85 %….. wastes.
For ores the following indexes are used:
• Ñontent of metal in an initial ore…….. a, %;
• Ñontent of metal in a concentrate …… b, %;
• Ñontent of metal in wastes ……………Q, %;
Efficiency of process is estimated by an index, which is named extraction (E, %).
E = y*b/a, %
The process of separation includes the following operations:
1. Preparatory. To them behave: crushing, grinding, screening. Intended for preparation of material to separetion.
2. Basic. To them behave: gravitation processes, flotation processes, magnetic separetion , electric separetion , special methods of separetion . Intended for mineral separation on useful components and wastes.
3. Final. To them behave: dewatering, classification on commodity sorts.
sequence of operations of separetion is named a process flowsheet.
Distinctions (differences) of minerals in certain properties are fixed in basis of separationseparation. The more contrast these distinctions, the better efficiency of separation. To properties of minerals, fixed in basis of separation, belong:
• Density;
• Wettability by water;
• Magnetic receptivity;
• Conductivity;
• Group of the properties fixed in basis of the special methods of separetion.
A density is fixed in a basis of gravitation processes, to which behaves: separation in dens medium, jigging, separation on concentration tables, separation on sluices, in spiral separators, separation in dens medium hydrocyclones. Difference in wettability is fixed in basis of flotation process. Difference in magnetic properties is fixed in basis of magnetic separation. Difference in electric properties is fixed in basis of electric separation. Difference in a color, brilliance, hardness, coefficient of friction, radio-active radiation and etc it is fixed in basis of the special methods of separation.
The gravitation methods of separation are based on distinction in the density of the separated components. One of methods is separation in dens medium. The separation takes place in a liquid having a density intermediate in relation to the density of the divided minerals.
The particles of coal, having a density less density of division, under action of Archimedes forces walk up the surface of dividing environment. The particles of waste, having a density is higher than density of dividing environment, go downward. Thus, the unregulated mixture of coal and waste divides into two products: concentrate and wastes.
This method of separation is based on difference in wettability of the dividing components. In this connection all minerals are divided by two groups: hydrophilic are moistened by water; hydrophobic are unmoistened by water.
The separation is realized in a water environment, where except for a mineral particles, a gaseous phase is present as bubbles of air (ðiñ.1.3). Walking up the surface of flotation chamber, the bubbles of air come in contact with hydrophobic and hydrophilic particles of material. The hydrophobic particles of coal stick to the bubbles of air and go up on the surface of chamber. The hydrophilic particles of wastes are moistened by water, does not stick to the bubbles of air and remain into the volume of chamber.
Thus, take place the separation of material on two products (coal and wastes) as a result of different moistened of particles.
Ïðîöåññ ýëåêòðîñåïàðàöèè ïîëåçíûõ èñêîïàåìûõ îñíîâàí íà ðàçëè÷èè â ýëåêòðîïðîâîäíîñòè ðàçäåëÿåìûõ êîìïîíåíòîâ. The process of electric separation of minerals is founded on differences in conductivity of the dividing components.
Initial material size 0 – 3 mm handles on precipitation electrode executed as a drum from stainless steel. All type particles come in contact with precipitation electrode charged with high potential. All conductors, adjoining with a drum, get charge of the same name with charge of the drum and push off from it. Non-conductors longer hold out on a drum and have other trajectory. Semiconductors get unloaded in middle part of separator. Thus, the unregulated mixture of particles with a different conductivity divides into three high-quality different products: concentrate (conductors); middlings (semiconductors); wastes (non-conductors).
This method is based on distinction in the coefficients of friction of the dividing minerals. Separation is carried out on a sloping surface. Particles different by the coefficient of friction acquire on a ramp a different speed and, consequently, a different trajectory of motion. Thus, it separation are realized.