Some minerals mined from the bowels of the earth are directly used in certain sectors of the national economy (stone, clay, limestone for construction purposes, mica for electrical insulation, etc.), but most of them are preliminarily enriched.

Enrichment of minerals called a set of operations of mechanical processing of a mineral in order to obtain products suitable for use in the national economy.

The process of enrichment of minerals is carried out at specially equipped, highly mechanized enterprises. These businesses are called processing plants if their main task is to separate minerals and crushing and screening plants, if enrichment is reduced mainly to crushing rocks and separating them by size and strength.

Minerals at processing plants undergo a series of sequential operations, as a result, useful components are separated from impurities. Mineral enrichment processes according to their purpose are divided into preparatory, basic and auxiliary .

To preparatory include the processes of crushing, grinding, screening and classification. Their task is to bring the mineral components into a state in which it is possible to conduct separation (decrease in size, separation by size, etc.);

To the main include the following processes:

gravity;

flotation;

magnetic;

electrical;

special;

combined.

The task of the main enrichment processes is to separate the useful mineral and waste rock.

to auxiliary include dehydration, dust collection, wastewater treatment, testing, control and automation, unloading, dry and water transport of material, mixing, distribution of material and reagents to machines, etc.

The task of these processes is to ensure the optimal flow of the main processes.

The set of sequential technological processing operations that minerals are subjected to at processing plants is called enrichment scheme. Depending on the nature of the information contained in the enrichment scheme, it is called technological, qualitative, quantitative, qualitative-quantitative, water-slurry and apparatus circuit diagram.

Everything that enters the enrichment or a separate enrichment operation is called source material, or nutrition.

The source material for the processing plant is ore. The percentage of a valuable component in the source material (ore) is usually denoted by (alpha). Products enrichment (or operation) refers to the materials obtained as a result of enrichment - concentrate, intermediate product (middle product) and tailings.

Concentrate the product of enrichment is called, in which the content of the valuable component is greater than in the original material. The percentage of the valuable component in the concentrate is denoted by (beta).

Tails called a beneficiation product that has a low content of a valuable component compared to the original ore. The percentage of a valuable component in the tails is usually denoted by (theta). Tailings are mainly waste rock and harmful impurities.

intermediate product(middle product) is a product in which the content of the valuable component is less than in the concentrate, and more than in the tails. The content of a valuable component in it is denoted by . Industrial products are usually sent for additional processing.

Concentrates and tailings can be both products of separate operations and final products of the enrichment process. The quality of the final or so-called commodity concentrates must comply with the state standard (GOST). Each GOST provides for the minimum content of a valuable component in concentrates and the permissible content of impurities.

To evaluate the enrichment results, the following main technological indicators and their symbols are used:

Output(gamma) - the amount of the product obtained, expressed as a percentage (or fractions of a unit) of the starting material.

The output of concentrate, middlings, tailings is determined from the following expressions:

where C is the amount of concentrate;

M - the amount of processed ore;

P - the amount of middlings.

Degree of extraction e(epsilon) - expressed as a percentage, the ratio of the amount of a valuable component in a given product (usually in a concentrate) to its amount in the source material (ore), taken as 100%. The degree of extraction into concentrate, middlings, tailings is determined from the formulas:

Degree of concentration(or enrichment factor) K - the ratio of the content of a valuable component in the concentrate to its content in the source material (ore):

Often the mass of products is unknown. But the content of a useful component in products is almost always known.

The yield of concentrate and tailings, its extraction are determined through the content by the following formulas:

According to such formulas, in the process of working at factories, it is possible to evaluate enrichment, having only data on the chemical analysis of ore () and enrichment products ( , ). In a similar way, equations and formulas can be obtained for the case when two concentrates and tails are obtained in the enrichment process, i.e., for two valuable components.

These equations are different expressions of the general rule that that the amount of material supplied for enrichment is equal to the sum of the products obtained

(lecture notes)

V.B.Kuskov

SAINT PETERSBURG

CONTROL 2

1. preparatory processes 8

1.1. GRANULOMETRIC COMPOSITION 8

1.2 CRUSHING 10

1.3. screening 14

1.4. GRINDING 17

1.5. HYDRAULIC CLASSIFICATION 20

2. MAIN PROCESSES OF ENRICHMENT 23

2.1. GRAVITATIONAL ENRICHMENT METHOD 23

2.3. MAGNETIC ENRICHMENT METHOD 35

2.4. ELECTRIC ENRICHMENT 39

2.5. special ENRICHMENT METHODS 43

2.6. COMBINED ENRICHMENT METHODS 48

3 AUXILIARY ENRICHMENT PROCESSES 49

3.1. DEHYDRATION OF ENHANCEMENT PRODUCTS 49

3.2. DUST EXTRACTION 53

3.3. WASTEWATER TREATMENT 54

3.3 TESTING, CONTROL AND AUTOMATION 55

4. BENEFITS 55

Doing

Minerals- natural mineral formations of the earth's crust, the chemical composition and physical properties of which allow them to be effectively used in the sphere of material production. Field mineral - an accumulation of mineral matter in the bowels or on the surface of the Earth, in terms of quantity, quality and conditions of occurrence suitable for industrial use. (With large areas of distribution, deposits form districts, provinces and basins). There are solid, liquid and gaseous minerals.

Solid minerals (ores), in turn, are divided into combustible (peat, shale, coal) and non-combustible, which are: agronomic (apatite and phosphorite, etc.), non-metallic (quartz, barite, etc.) and metallic (ores ferrous and non-ferrous metals). The efficiency of using one or another mineral depends, first of all, on the content of a valuable component in it and the presence of harmful impurities. Direct metallurgical or chemical processing of a mineral is expedient (technically and economically profitable) only if the content of the useful component in it is not lower than a certain limit determined by the level of development of technology and technology (and the need for this raw material) at the present time. In most cases, the direct use of the mined rock mass or its processing (metallurgical, chemical, etc.) is not economically feasible, and sometimes technically impossible, because. minerals suitable for direct processing are rare in nature; in most cases, they are subjected to special processing - enrichment.

Mineral enrichment a set of processes of mechanical processing of mineral raw materials in order to extract useful (valuable) components and remove waste rock and harmful impurities. As a result of enrichment, concentrate (concentrates) and tailings are obtained from ore.

Concentrate- this is a product where most of the useful minerals (and a small amount of waste rock minerals) are released (concentrated). The quality of the concentrate is mainly characterized by the content of the valuable component ( it is always higher than in ore, the concentrate is richer in the valuable component (hence the name - enrichment), as well as in the content of useful and harmful impurities, humidity and granulometric characteristics.

Tails- a product into which most of the waste rock minerals, harmful impurities and an insignificant amount of a useful component will be released (the content of valuable components in tailings is lower than in concentrates and ore).

In addition to concentrate and tailings, it is possible to obtain intermediate products, i.e. products characterized by a lower content of useful components compared to concentrates and a higher content of useful components compared to tailings.

Useful(valuable) components are called chemical elements or natural compounds, for the production of which this mineral is mined and processed. As a rule, the valuable component in the ore is in the form of a mineral (there are few native elements in nature: copper, gold, silver, platinum, sulfur, graphite).

Useful impurities name chemical elements or natural compounds that are part of the mineral in small quantities and improve the quality of the finished product (or are released during further processing). For example, useful impurities in iron ores are alloying additives such as chromium, tungsten, vanadium, manganese, etc.

Harmful impurities name individual elements and natural chemical compounds contained in minerals in small quantities and having a negative impact on the quality of finished products. For example, harmful impurities in iron ores are sulfur, arsenic, phosphorus, in coking coals - sulfur, phosphorus, in thermal coals - sulfur, etc.

Enrichment of minerals allows you to increase economic efficiency of their further processing, also, in some cases, without the enrichment stage, further processing becomes generally impossible. For example, copper ores (containing, as a rule, very little copper) cannot be directly smelted into metallic copper, since copper passes into slag during smelting. In addition, enrichment of minerals allows you to:

 increase industrial stocks of raw materials through the use of deposits of poor minerals with a low content of valuable components;

 increase labor productivity at mining enterprises and reduce the cost of mined ore due to the mechanization of mining operations and continuous extraction of minerals instead of selective;

 integrated use of minerals, since preliminary enrichment allows extracting not only the main useful components, but also accompanying ones contained in small quantities;

 reduce the cost of transporting richer products to consumers, rather than the entire volume of extracted minerals;

 extract from mineral raw materials those harmful impurities that, during its further processing, can pollute the environment and thereby threaten human health and worsen the quality of the final product.

Enrichment methods can also be used in the processing of municipal solid waste (350-400 kg/year per person are generated).

Minerals at processing plants undergo a series of sequential operations, as a result of which useful components are separated from impurities. Processes of mineral processing according to their purpose are divided into preparatory, auxiliary and main ones.

To preparatory include the processes of crushing, grinding, screening and classification. Their task is to separate the useful mineral and the waste rock (“open” the intergrowths) and create the desired granulometric characteristic of the processed raw material.

Task major beneficiation processes - to separate useful mineral and waste rock. To separate minerals, differences in the physical properties of the separated minerals are used. These include:

In addition to the above, there are other enrichment methods. Also, sometimes agglomeration processes (increasing the size of materials) are referred to as enrichment processes.

To auxiliary include dewatering, dust collection, wastewater treatment, sampling, control and automation. The task of these processes is to ensure the optimal flow of the main processes, to bring the separation products to the required conditions.

The set of sequential technological processing operations that minerals are subjected to at processing plants is called enrichment scheme. Depending on the nature of the information contained in the enrichment scheme, it is called technological, qualitative, quantitative, qualitative-quantitative, water-slurry and apparatus circuit diagram.

Enrichment, like any other technological process, is characterized by indicators. The main technological indicators of enrichment are as follows:

 Q mass of the product (productivity); P – mass (capacity) of the calculated component in the product . They are usually expressed in tons per hour, tons per day, etc.;

 the content of the calculated component in the product - ,  is the ratio of the mass of the calculated component in the product to the mass of the product; the content of various components in a mineral and in the resulting products is usually calculated as a percentage (sometimes the content in the source material is denoted by , in concentrate - , in tailings - ). The content of useful components in the extracted raw material (ore) can range from fractions of a percent (copper, nickel, cobalt, etc.) to several percent (lead, zinc, etc.) and several tens of percent (iron, manganese, fossil coal and some other non-metallic minerals);

 product yield –  i,  k,  xv  is the ratio of the mass of the product to the mass of the original ore; the yield of any enrichment product is expressed as a percentage, less often in fractions of a unit;

 extraction of a valuable component – ​​ u,  k,  xv  is the ratio of the mass of the calculated component in the product to the mass of the same component in the original ore; extraction is expressed as a percentage, less often in fractions of a unit.

Output i-th product is calculated by the formula:

 i = (Q i /Q ref)100,%

Also, for the case of separation into two products - concentrate and tailings, their yield can be determined through the content using the following formulas:

 k = 100,%;  xv =
100,%;

The sum of concentrate and tailings yields is:

 k +  xv = 100%.

It's obvious that

Q con + Q xv = Q ref.;

R con + R xv = R ref.

 1 +  2 +…+  n = 100%.

Similarly for Q and R.

(In mineral processing, as a rule, only two products are obtained - concentrate and tailings, but not always, sometimes there can be more products).

.

In practice, the contents are usually determined by chemical analysis.

Extracting a useful component in i– th product:

i = 100.%, or  i = %.

The sum of concentrate and tailings extractions is equal to:

 to +  xv = 100%.

This formula is valid for any number of products:

 1 +  2 +…  n = 100%.

To find the content in the product of mixing, you can use the so-called balance equation (for the case of separation into two products):

 to  con +  xv  con =  ref  ref.

The equation is also valid for any number of products:

 1  1 +  2  2 +…+ n  n =  ref  ref.

It should be noted that  ref = 100%.

Example. The ore is separated into two products (Fig. 1.1) - concentrate and tailings. Ore productivity Q ref = 200 t/h, for concentrate - Q con = 50 t/h. Performance by design component R ref = 45 t/h, by component in concentrate R con = 40 t/h.

Q xv = Q ref - Q con \u003d 200 - 50 \u003d 150 t / h;

 con = ( Q con / Q ref)100 = (50/200)100 = 25%;

 xv \u003d  ref -  k \u003d 100 - 25 \u003d 75%,

or  xv = ( Q xv / Q ref)100 =(150/200) . 100=75%;

it's obvious that Q xv = ( xv  Q ref)/100 = (75200)/100 = 150 t/h;

=
=
= 22,5 %;

=
=
= 80 %;

R xv = R ref - R con \u003d 45 - 40 \u003d 5,

then
=
=
=3,33 %.

Or using the balance equation we have:

 to  con +  xv  con =  ref  ref,

 xv =
=
= 3,33 %.

The task of the main enrichment processes is to separate the useful mineral and waste rock. They are based on differences in the physical and physicochemical properties of the separated minerals.

Most often in the practice of enrichment, gravity, flotation and magnetic enrichment methods are used.

2.1. Gravitational enrichment method

Gravitational enrichment method called such, in which the separation of mineral particles, differing in density, size and shape, is due to the difference in the nature and speed of their movement in fluid media under the action of gravity and resistance forces. The gravity method occupies a leading position among other enrichment methods. The gravitational method is represented by a number of processes. They can be proper gravitational (separation in the field of gravity - usually for relatively large particles) and centrifugal (separation in a centrifugal field - for small particles). If separation occurs in air, then the processes are called pneumatic; in other cases - hydraulic. The most widespread in enrichment are actually gravitational processes carried out in water.

According to the type of apparatus used, gravity processes can be divided into jigging, enrichment in heavy media, concentration on tables, enrichment in locks, in chutes, screw separators, enrichment in centrifugal concentrators, counterflow separators, etc. Also, gravitational processes usually include washing.

Gravity processes are used in the enrichment of coal and shale, gold and platinum ores, tin ores, oxidized iron and manganese ores, chromium, wolframite and ores of rare metals, building materials and some other types of raw materials.

The main advantages of the gravitational method are economy and environmental friendliness. Also, the advantages include high productivity, characteristic of most processes. The main drawback is the difficulty of effectively enriching small classes.

Gravity processes are used both independently and in combination with other enrichment methods.

The most common method of gravity enrichment is jigging. jigging is the process of separating mineral particles by density in an aqueous or air medium, pulsating relative to the mixture being separated in the vertical direction.

This method can enrich materials with a particle size of 0.1 to 400 mm. Jigging is used in the enrichment of coal, shale, oxidized iron, manganese, chromite, cassiterite, wolframite and other ores, as well as gold-bearing rocks.

During the jigging process (Fig. 2.1), the material placed on the sieve of the jigging machine is periodically loosened and compacted. In this case, the grains of the enriched material, under the influence of forces acting in a pulsating flow, are redistributed in such a way that particles of maximum density are concentrated in the lower part of the bed, and the minimum density is concentrated in the upper part (the size and shape of the particles also affect the delamination process).

When enriching fine material, an artificial bed of material is placed on the sieve (for example, when coal is enriched, a bed of pegmatite is used), the density of which is greater than the density of a light mineral, but less than the density of a heavy one. the size of the bed is 5-6 times larger than the size of the maximum piece of the original ore and several times larger than the holes in the sieve of the jigging machine. More dense particles pass through the bed and sieve and are unloaded through a special nozzle at the bottom of the jigging machine chamber.

When enriching large material, the bed is not specially laid on the sieve, it is formed by itself from the enriched material and is called natural (the enriched material is larger than the openings of the sieve). Dense particles pass through the bed, move over the sieve and are unloaded through a special unloading slot in the sieve and, further, by the elevator from the machine chamber.

And, finally, when enriching a widely classified material (there are both small and large particles), small dense particles are unloaded through a sieve, large dense particles through an unloading gap (Fig. 2.1).

Currently, about 100 designs of jigging machines are known. Machines can be classified as follows: according to the type of separation medium - hydraulic and pneumatic; according to the method of creating pulsations - piston with a movable sieve, diaphragm, pistonless or air-pulsation (Fig. 2.2). Also, machines can be for the enrichment of small classes, large classes, widely classified material. The most common is hydraulic jigging. And among machines, pistonless ones are most often used.

Piston jigging machines can be used for jigging material with a particle size of 30 + 0 mm. Water vibrations are created by the movement of the piston, the stroke of which is regulated by an eccentric mechanism. Piston jigging machines are not currently produced and have in fact been completely replaced by other types of machines.

Diaphragm jigging machines are used for jigging iron, manganese ores and ores of rare and noble metals with a particle size. Diaphragm jigging machines are used for enrichment of ores with a particle size of 30 to 0.5 (0.1) mm. They are manufactured with various diaphragm arrangements.

Horizontal aperture diaphragm machines usually have two or three chambers. The water oscillations in the chambers are created by the up and down movements of the conical bottoms provided by one or more (depending on the type of machine) eccentric drive mechanisms. The stroke of the conical bottom is controlled by turning the eccentric sleeve relative to the shaft and tightening the nuts, and the frequency of its swings is controlled by changing the pulley on the motor shaft. The body of the machine at each chamber is connected to the conical bottom by rubber cuffs (diaphragms).

Diaphragm jigging machines with a vertical diaphragm have two or four chambers with pyramidal bottoms separated by a vertical partition, in the wall of which a metal diaphragm flexibly connected to it is mounted, making reciprocating movements.

Jigging machines with a movable sieve are used in domestic practice for the enrichment of manganese ores with a particle size of 3 to 40 mm. Machines are not mass-produced. The drive crank mechanism of the sieve is located above the machine body. The sieve makes arcuate movements, in which the material is loosened and moves along the sieve. The machines have two-, three- and four-section sieves with an area of ​​2.9-4 m 2 . Heavy products are unloaded through the side or central slot. In foreign practice, jigging machines with a movable sieve are used, which make it possible to enrich material with a particle size of up to 400 mm. For example, the Humboldt-Vedag machine makes it possible to enrich material with a particle size of -400 + 30 mm. A distinctive feature of this machine is that one end of the sieve is fixed on the axis and therefore does not move in the vertical direction. The separation products are unloaded by means of an elevator wheel. The car differs in high profitability in work.

Air pulsating (pistonless) jigging machines (Fig. 3.3) differ from others by using compressed air to create water vibrations in the jigging compartment. The machines have an air and jigging compartment and are equipped with a universal drive that provides symmetric and asymmetric jigging cycles and the ability to control the air supply to the chambers. The main advantage of pistonless machines is the ability to control the jigging cycle and achieve high separation accuracy with increased bed height. These machines are used mainly for the enrichment of coal, less often ferrous metal ores. Machines can have side air chambers (Fig. 2.3), under-screen air chambers, branch pipe under-screen air chambers.

With the lateral arrangement of air chambers, the uniformity of water pulsations in the jigging compartment is maintained with a chamber width of no more than 2 m. To ensure a uniform distribution of the pulsating flow velocity field over the area of ​​the jigging sieve, modern designs of jigging machines use hydraulic fairings at the end of the partition between the air and jigging compartments.

Compressed air enters the air compartment periodically through various types of pulsators (rotary, valve, etc.), installed one for each chamber; also periodically the air is released from the air compartment into the atmosphere. When air is admitted, the water level in the air compartment decreases, and in the jigging compartment, of course, it rises (because these are “communicating vessels”); when air is released, the reverse occurs. Due to this, oscillatory movements are made in the jigging compartment.

Enrichment mineral in heavy environments based on the separation of the mineral mixture by density. The process occurs in accordance with the law of Archimedes in media with a density intermediate between the density of a specific light and specific heavy mineral. Specifically light minerals float, and specific heavy ones sink to the bottom of the apparatus. Enrichment in heavy media is widely used as the main process for coals of difficult and medium categories of washability, as well as shale, chromite, manganese, sulfide ores of non-ferrous metals, etc. The separation efficiency in heavy media is higher than the efficiency of enrichment in jigging machines (this is the most efficient gravity process ).

Heavy liquids and heavy suspensions are used as heavy media. There is one fundamental difference between them. A heavy liquid is homogeneous (single-phase), a heavy suspension is inhomogeneous (consists of water and particles suspended in it - a weighting agent). Therefore, enrichment in a heavy liquid is, in principle, acceptable for particles of any size.

A heavy suspension can be considered a pseudo-fluid with a certain density only for sufficiently large (compared to the size of the weighting agent particles) particles. In addition, due to the general movement of the particles of the weighting agent in a certain direction under the influence of the force field in which the enrichment is carried out (gravitational or centrifugal), in order to obtain a suspension of uniform density in the apparatus, it is necessary to mix it. The latter inevitably affects the particles subjected to enrichment. Therefore, the lower limit of particle size, enriched in a heavy suspension, is limited and is: in gravity processes - for ores 2-4 mm, for coals - 4-6 mm; in centrifugal processes for ores - 0.25-0.5 mm, for coals 0.5-1 mm.

As an industrial heavy medium, heavy suspensions are used, i.e. a suspension of fine specific heavy particles (weighting agent) in a medium, which is usually water. (Heavy fluids are not used in industry due to their high cost and toxicity) Hydraulic slurries are simply called slurries. The most commonly used weighting agents are magnetite, ferrosilicon and galena. The particle size of the weighting agent is usually0.15mm. The density of the suspension is determined by the expression:

 c \u003d C ( y - 1) + 1, g / cm 3,

where: C is the concentration of the weighting agent, d.u.,  y is the density of the weighting agent, g / cm 3. Thus, by changing the concentration of the weighting agent, it is possible to prepare a suspension of the required density.

Enrichment in heavy suspensions of medium and large-sized material is carried out in gravity separators (in separators with static separation conditions). Enrichment of fine-grained material is carried out in centrifugal separators (separators with dynamic separation conditions) - hydrocyclones. Other types of heavy media separators (aerosuspension, vibration) are rarely used.

Heavy-medium gravity separators can be divided into three main types - wheel, cone and drum. Wheel separators (Fig. 2.4) are used to enrich material with a particle size of 400-6 mm, in domestic practice mainly for coal and shale. The most commonly used SKV is a wheel separator with a vertical elevator wheel.

In conical suspension separators (Fig. 2.5), the heavy fraction is usually unloaded by an internal or external airlift. These separators are used for beneficiation of ore material with a size of –80(100)+6(2) mm

Cone separators with an external air lift (Fig. 2.5) consist of an upper cylindrical and a lower conical part. The lower conical part ends with a transitional elbow connecting the cone with an air lift that lifts the settled particles. Compressed air is supplied to the air lift pipe through nozzles at a pressure of about 3-4 10 5 Pa. The diameter of the airlift pipe is taken equal to at least three sizes of the largest piece of ore. The floating product, together with the suspension, is drained into the chute, and the heavy product is fed by an airlift into the unloading chamber.

The drum separator (Fig. 2.6) is used for enrichment of ore material with a particle size of 150 + 3 (5) mm, with a high density of the enriched material.

Heavy-medium enrichment hydrocyclones are structurally similar to classifiers. The enriched material is fed tangentially through the feed pipe along with the heavy slurry. Under the action of centrifugal force (many times greater than the force of gravity), the material is stratified: dense particles move closer to the walls of the apparatus and are transported by an “external vortex” to the unloading (sand) nozzle, light particles move closer to the axis of the apparatus and are transported by an “internal vortex” to drain nozzle.

Technological schemes of enrichment in heavy suspensions are practically the same for most operating plants. The process consists of the following operations: preparation of heavy suspension, preparation of ore for separation, separation of ore in suspension into fractions of different density, drainage of the working suspension and washing of separation products, regeneration of the weighting agent.

Enrichment in flows flowing along inclined surfaces is carried out on concentration tables, locks, in chutes and screw separators. The movement of the pulp in these devices occurs along an inclined surface under the action of gravity at a small (compared with the width and length) flow thickness. Usually it exceeds the size of the maximum grain by 2-6 times.

Concentration(enrichment) on the tables- this is the process of separation by density in a thin layer of water flowing along a slightly inclined plane (deck), performing asymmetric reciprocating movements in a horizontal plane perpendicular to the direction of water movement. The concentration on the table is used for the enrichment of small classes - 3 + 0.01 mm for ores and -6 (12) + 0.5 mm for coals. This process is used in the enrichment of ores of tin, tungsten, rare, noble and ferrous metals, etc.; for the enrichment of small classes of coal, mainly for their desulfurization. The concentration table (Fig. 2.7) consists of a deck (plane) with narrow slats (corrugations); support device; drive mechanism. Deck tilt angle  = 410. For light particles, hydrodynamic and lifting turbulent forces are predominant, so light particles are washed away in a direction perpendicular to the deck. Particles of intermediate density fall between heavy and light particles.

Gateway(Fig. 2.8) is an inclined rectangular chute with parallel sides, on the bottom of which trapping coatings (hard stencils or soft mats) are laid, designed to hold settled particles of heavy minerals. Locks are used to enrich gold, platinum, cassiterite from placers and other materials, the enriched components of which vary significantly in density. Gateways are characterized by a high degree of concentration. The material is fed continuously to the sluice until the cells of the stencils are filled predominantly with particles of dense minerals. After that, the loading of the material is stopped and the sluice is rinsed.

jet chute(Figure 2.9) has a flat bottom and sides converging at a certain angle. The pulp is loaded onto the wide upper end of the chute. At the end of the trough, particles of higher density are located in the lower layers, and particles of lower density are located in the upper layers. At the end of the chute, the material is separated by special dividers into concentrate, middlings and tailings. Tapering troughs are used in the enrichment of alluvial ores. Apparatuses such as tapering chutes are divided into two groups: 1) apparatuses consisting of a set of individual chutes in various configurations; 2) conical separators, consisting of one or more cones, each of which is like a set of radially installed tapering chutes with a common bottom.

At screw separators a fixed inclined smooth chute is made in the form of a spiral with a vertical axis (Fig. 2.10), they are used to separate material with a particle size of 0.1 to 3 mm. When moving in a swirling flow, in addition to the usual gravitational and hydrodynamic forces acting on grains, centrifugal forces develop. Heavy minerals are concentrated at the inner side of the trough, while light minerals are concentrated at the outer. Then the separation products are unloaded from the separator using dividers located at the end of the chute.

In centrifugal concentrators the centrifugal force acting on the body is many times greater than the force of gravity and the material is separated by the centrifugal force (gravity has only a small effect). In those cases, if the centrifugal force and gravity are commensurate and separation occurs under the action of both forces, enrichment is usually called centrifugal-gravitational (screw separators).

The creation of a centrifugal field in centrifugal concentrators can in principle be carried out in two ways: tangential supply of a flow under pressure into a closed and stationary cylindrical vessel; by swirling a freely supplied flow in an open rotating vessel and, accordingly, centrifugal concentrators can be fundamentally divided into two types: pressure cyclone apparatus; non-pressure centrifuges.

According to the principle of operation, cyclone-type centrifugal concentrators have much in common with hydrocyclones, but they differ in a significantly larger taper angle (up to 140). Due to this, a “bed” of enriched material is formed in the apparatus, which plays the role of a heavy suspension in heavy-medium enrichment cyclones. And the division is the same. Compared to heavy-medium hydrocyclones, these are much more economical in operation, but they give worse technological performance.

The operation of concentrators of the second type resembles the operation of a conventional centrifuge. Centrifugal concentrators of this type are used to enrich coarse-grained sands, in the exploration of gold-bearing alluvial deposits, and in the extraction of fine free gold from various products. The apparatus is a hemispherical bowl lined with a corrugated rubber insert. The bowl is fixed on a special platform (platform), which receives rotation from an electric motor through a V-belt drive. The pulp of the enriched material is loaded into the apparatus, light particles together with water merge through the sides, heavy ones get stuck in the grooves. To unload the concentrate caught by the corrugated rubber surface, the bowl is stopped and a rinse is performed (there are also designs that allow continuous unloading). When working on coarse gold-bearing sands, the concentrator provides a very high degree of reduction - up to 1000 times or more with high (up to 96-98%) gold recovery.

Countercurrent water separation used in domestic practice for the processing of energy and diluted coals. Apparatus for enrichment by this method are screw and steeply inclined separators. Screw horizontal and vertical are used for enrichment of coal with a particle size of 6 - 25 mm and 13 - 100 mm, as well as for the enrichment of screenings and coarse-grained sludge. Steeply inclined separators are used for enrichment of diluted coals up to 150 mm in size. The advantage of countercurrent separators is the simplicity of the technological scheme. In all counterflow separators, the material is separated into two products: concentrate and waste. The counter transport flows of separation products formed during the separation move within the working area with a given hydraulic resistance to their relative movement, while the flow of light fractions is associated with the flow of the separation medium, and the flow of heavy fractions is counter. The working zones of the separators are closed channels, equipped with a system of the same type of elements, streamlined by the flow and causing the formation of a system of secondary flows and vortices organized in a certain way. As a rule, in such systems, the source material is separated at a density that is much higher than the density of the separating medium.

A necessary condition for the preparation of sands of alluvial deposits and ores of sedimentary origin for enrichment is their release from clay. The mineral particles in these ores and sands are not bound by mutual intergrowth, but are cemented into a dense mass by a soft and viscous clay substance.

The process of disintegration (loosening, dispersion) of clay material, cementing grains of sand or ore, with its simultaneous separation from ore particles with the help of water and the corresponding mechanisms is called flushing. Disintegration usually occurs in water. At the same time, clay swells in water, and this facilitates its destruction. As a result of washing, washed material (ore or sand) and sludge containing fine-grained clay particles dispersed in water are obtained. Washing is widely used in the enrichment of ferrous metal ores (iron, manganese), sands of alluvial deposits of rare and precious metals, construction raw materials, kaolin raw materials, phosphorites and other minerals. Washing can be of independent importance if it results in a marketable product. More often it is used as a preparatory operation to prepare the material for subsequent enrichment. For washing, they use: screens, butars, scrubbers, scrubber-butars, trough washes, vibro-washers and other devices.

Pneumatic processes beneficiation is based on the principle of separating minerals by size (pneumatic classification) and density (pneumatic concentration) in an ascending or pulsating air stream. It is used in the enrichment of coal, asbestos and other minerals with low density; in the classification of phosphorites, iron ores, minium and other minerals in the cycles of crushing and dry grinding, as well as in the dedusting of air flows in the shops of concentrating factories. The use of the pneumatic enrichment method is advisable in the harsh climatic conditions of the northern and eastern regions of Siberia or in areas where there is a lack of water, as well as for the processing of minerals containing easily soaked rock, which forms a large amount of sludge that violates the clarity of separation. The advantages of pneumatic processes are in their efficiency, simplicity and convenience of tailings disposal, the main disadvantage is in the relatively low separation efficiency, which is why these processes are used very rarely.

According to the type of environment in which enrichment is carried out, enrichment is distinguished:

dry enrichment (in air and aerosuspension),

wet (in water, heavy media),

in a gravitational field

in the field of centrifugal forces,

in a magnetic field

in an electric field.

Gravity beneficiation methods are based on the difference in density, size and speed of rock pieces in water or air. When separating in heavy media, the difference in the density of the separated components is of primary importance.

To enrich the smallest particles, a flotation method is used, based on the difference in the surface properties of the components (selective wettability with water, adhesion of mineral particles to air bubbles).

Mineral processing products

As a result of enrichment, the mineral is divided into several products: concentrate (one or more) and waste. In addition, intermediate products can be obtained during the enrichment process.

concentrates

Concentrates are products of enrichment, in which the main amount of a valuable component is concentrated. Concentrates, in comparison with enriched material, are characterized by a significantly higher content of useful components and a lower content of waste rock and harmful impurities.

Waste - products with a low content of valuable components, the further extraction of which is technically impossible or economically inexpedient. (This term is equivalent to the earlier term tailings, but not the term tailings, which, unlike waste, are present in almost every enrichment operation)

Intermediates

Intermediate products (middle products) are a mechanical mixture of intergrowths with open grains of useful components and waste rock. Intermediates are characterized by a lower content of useful components in comparison with concentrates and a higher content of useful components in comparison with waste.

Enrichment quality

The quality of minerals and enrichment products is determined by the content of a valuable component, impurities, related elements, as well as moisture content and fineness.

Mineral processing is ideal

Under the ideal enrichment of minerals (ideal separation) is understood the process of separation of the mineral mixture into components, in which there is no clogging of each product with particles foreign to it. The efficiency of ideal mineral processing is 100% by any criteria.

Partial mineral processing

Partial enrichment is the enrichment of a separate class of mineral size, or the separation of the most easily separated part of contaminating impurities from the final product in order to increase the concentration of a useful component in it. It is used, for example, to reduce the ash content of unclassified thermal coal by separating and enriching a large class with further mixing of the resulting concentrate and fine unenriched screenings.

Losses of minerals during enrichment

The loss of a mineral during enrichment is understood as the amount of a useful component suitable for enrichment, which is lost with enrichment waste due to process imperfections or violations of the technological regime.

Permissible norms for intercontamination of enrichment products for various technological processes, in particular, for coal enrichment, have been established. The allowable percentage of mineral losses is removed from the balance of enrichment products to cover discrepancies when taking into account the mass of moisture, the removal of minerals with flue gases from dryers, and mechanical losses.

Mineral Processing Boundary

The boundary of mineral processing is the smallest and largest size of particles of ore, coal, effectively enriched in a processing machine.

Depth of enrichment

The depth of enrichment is the lower limit of the fineness of the material to be enriched.

When enriching coal, technological schemes are used with enrichment limits 13; 6; one; 0.5 and 0 mm. Accordingly, unenriched screenings with a size of 0-13 or 0-6 mm, or sludge with a size of 0-1 or 0-0.5 mm, are separated. An enrichment limit of 0 mm means that all size classes are subject to enrichment.

Preparatory processes for mineral processing

Introduction

Purpose of mineral processing

The extracted rock mass is a mixture of pieces of mineral complexes, intergrowths of minerals with different physical, physicochemical and chemical properties. To obtain final products (concentrates of metals, coke, building materials, chemical fertilizers, etc.), it must be subjected to a number of processing processes: mechanical, thermal, chemical.

The processing of minerals at the concentrator includes a number of operations, as a result of which the separation of useful components from impurities is achieved, those. bringing the mineral to a quality suitable for subsequent processing, for example, it is necessary to increase the content of: iron from 30-50% to 60-70%; manganese from 15-25% to 35-45%, copper from 0.5-1.5% to 45-60%, tungsten from 0.02-0.1% to 60-65%.

According to their purpose, the processes of processing minerals are divided into preparatory, main(enrichment) and support.

Preparatory processes are designed to open or open grains of useful components (minerals) that make up minerals, and dividing them into size classes, meeting the technological requirements of subsequent enrichment processes.

The preparatory processes include crushing, grinding, screening and classification.

Enrichment of minerals is a set of processes of mechanical processing of mineral raw materials, which makes it possible to separate useful minerals (concentrate) from waste rock.

Concentration engineers should solve the following tasks:

Integrated development of mineral resources;

Utilization of processed products;

Creation of new processes of non-waste technology for separating minerals into final marketable products for their use in industry;

Environmental protection.

Separation of mixtures of minerals is carried out on the basis of differences in physical, physico-chemical and chemical properties to obtain a number of products with a high content of valuable components (concentrates) , low (intermediate products) and insignificant (waste, tailings) .

The enrichment process is aimed not only at increasing the content of a valuable component in the concentrate, but also at removing harmful impurities:

sulfur in the corner phosphorus in manganese concentrate, arsenic in brown iron ore and sulfide polymetallic ores. These impurities, getting into cast iron and then into steel, worsen the mechanical. metal properties.

Brief information about minerals

minerals called ores, non-metallic and combustible fossil materials used in industrial production in natural or processed form.

To ores include minerals that contain valuable components in an amount sufficient to make their extraction economically viable.

Ores are classified into metallic and non-metallic.

metal ores- raw materials for the production of ferrous, non-ferrous, rare, precious and other metals - tungsten-molybdenum, lead-zinc, manganese, iron, cobalt, nickel, chromite, gold-containing;

non-metallic ores- asbestos, barite, apatite, phosphorite, graphite, talc, antimony, etc.

Nonmetallic minerals - raw materials for the production of building materials (sand, clay, gravel, building stone, Portland cement, building gypsum, limestone, etc.)

combustible minerals - solid fuel, oil and combustible gas.

Minerals consist of minerals that differ in their value, physical and chemical properties (hardness, density, magnetic permeability, wettability, electrical conductivity, radioactivity, etc.).

Minerals- called native (i.e. occurring in nature in its pure form) elements and natural chemical compounds.

Useful mineral (or component)- they call an element or its natural compound, in order to obtain which the extraction and processing of a mineral is carried out. For example: in iron ore, useful minerals are magnetite Fe 3 O 4, hematite Fe 2 O 3.

Useful impurities- called minerals (elements), the content of which in small quantities leads to an improvement in the quality of products obtained from useful minerals. For example, impurities vanadium, tungsten, manganese, chromium in iron ore positively affect the quality of the metal smelted from it.

Harmful impurities- called minerals (elements), the content of which in small quantities leads to a deterioration in the quality of products obtained from useful minerals. For example, impurities sulfur, phosphorus, arsenic adversely affect the steelmaking process.

Companion elements called the components contained in the mineral in small quantities, released during the enrichment process into individual products or the product of the main component. Further metallurgical or chemical processing of satellite elements allows them to be extracted into a separate product.

Minerals of waste rock- call components that do not have industrial value. In iron ore, these may include SiO 2 , Al 2 O 3 .

Depending on the structure, minerals are distinguished interspersed and solid, for example, in disseminated - individual small grains of a useful mineral are scattered among grains of waste rock; in solid - grains of a useful mineral are represented mainly by a continuous mass, and minerals of waste rock in the form of interlayers, inclusions.