Non-metallic mineral processing technology foundation

Non-metallic minerals beneficiation and purification purposes

(1) Separating the useful minerals from the gangue minerals in the ore to enrich the useful minerals;

(2) removing harmful impurities from the ore;

(3) Recover associated minerals as much as possible, and comprehensively and economically and comprehensively utilize mineral resources.

At present, the commonly used methods for purifying non-metallic minerals are flotation method, re-election method, magnetic separation method, electric separation method, chemical beneficiation method, photoelectric sorting method, friction washing and mineral processing methods of ultrafine particles which have appeared in recent years.

Non-metallic ore sorting and purification features

(1) The purpose of non-metallic ore dressing is usually to obtain a product with certain physicochemical properties, rather than to obtain one or several useful elements in the mineral.

(2) The non-metallic ore beneficiation process should maintain the crystal structure of useful minerals as much as possible so as not to affect their industrial use and use value.

(3) The calculation of non-metallic ore dressing index is generally based on the content of useful minerals, and the oxide grade and the recovery rate of useful minerals are often expressed in the form of oxides, rather than the content of certain elements in the mineral.

(4) Non-metallic ore beneficiation purification not only enriches useful minerals, removes harmful impurities, but also grinds and classifies products of different specifications.

1. Picking and friction washing

Picking

Picking is a beneficiation method that utilizes the surface characteristics of the ore, optical properties, electrical properties, magnetic properties, radioactivity, and the physical properties of the ore to absorb and reflect radiation, and separates useful minerals from gangue minerals.

Sorting is mainly used for the sorting of bulk and granular materials, such as removing large waste rock or picking up large rich ore. The upper limit of the sorting granularity can reach 250-300 mm, and the lower limit is 10 mm. For individual precious minerals (such as diamond ), the lower limit can be 0.5-1 mm.

For the sorting of non-metallic minerals, the sorting has a special effect and can be used to pre-enrich or obtain the final product. For example, for the original diamond ore, the sorting can be used to separate the diamond and the waste rock in advance, and the rough selection and selection of the diamond are adopted. Picking can obtain diamond finished products. Similarly, for non-metallic minerals such as Dali right, limestone , gypsum , talc , kaolin , asbestos, etc., the final product with higher purity can be selected.

(1) Manual picking

The ore and waste rock are sorted by hand according to the appearance characteristics (color, gloss, shape, etc.) between the ore and the waste rock. There are two types: forehand selection (using useful minerals from materials) and backhand selection (removing waste stones from materials). A method mainly used for mechanical sorting or bad can not guarantee the quality of the ore, such as long fibers chosen asbestos, mica flake, from the coal-based culling kaolinite bulk waste rock (quartz, feldspar) and the like. Hand selection is the easiest way to pick, but it is labor intensive and inefficient.

Manual picking is generally performed on hand-selected fields, fixed grid screens, hand-selected belt conveyors, and hand-selected platforms. Common hand-selected equipments are hand-selected belts and hand-selected platforms. The hand-selected belt requires a flat belt with a width of no more than 1.2m, a speed of 0.2-0.4m/s, an inclination of no more than 15 degrees, a height of 0.7-0.8m from the ground, and a height of 2m from the ground. The hand selection station is generally based on an area of ​​3.2 m2 for 4 people.

(2) Mechanical picking

According to the appearance characteristics of the ore and the difference of the ore reflected by visible light, X-ray, γ-ray or the natural radiation ability of the ore, the ore separation method of ore and gangue is realized by means of the instrument. Such as radioactive sorting of gamma rays; ray absorption sorting (gamma absorption method, x-ray absorption method, neutron absorption method); luminescence sorting (gamma fluorescence method, x fluorescence method, ultraviolet fluorescence method, infrared method); photoelectric sorting (surface photometry) Picking); electromagnetic picking.

Which sorting method is adopted is more reasonable, mainly determined by the characteristics of the ore, the nature of the ore is different, and the sorting method is also different.

Friction washing

Friction washing is a process for treating ore that is glued or clayed with clay , including both shredding and separation.

Usually, the mineral is soaked in an aqueous medium, washed and mechanically agitated (if necessary, a dispersant is added), and the mineral particles adhered by the slime are dissociated and contaminated with clay by means of the friction between the minerals themselves. Phase separation is called friction washing.

Scrubbing (frictional washing) can be used as a preliminary preparation for other purification operations or as a separate purification of minerals.

2. Gravity dressing

Gravity ore dressing is referred to as re-election. It is based on the difference in density between minerals, in a certain medium flow (usually water, heavy liquid or heavy suspension), loosened by the force of fluid buoyancy, power or other mechanical forces, in gravity (or centrifugal force) and sticky Under the action of hysteresis, the mineral particles of different density (particle size) are stratified and transferred, so as to achieve the purification method of separation of useful minerals and gangue. With re-election, the greater the difference in density between the useful mineral and the gangue, the more favorable the sorting, and the smaller the sorting, the more difficult it is to sort. Judging the difficulty of ore re-election can be based on the following criteria:

E=(δ2—ρ)/(δ1—ρ)

In the formula, δ1, δ2, and ρ are the density of light minerals, heavy minerals, and medium, respectively. According to the value of E, the difficulty of re-election of ore can be divided into five grades. Re-purification is one of the effective methods for processing ore sorting of coarse, medium and fine particles (substantially bound to more than 25 mm, 25 to 2 mm, 2 to 0.1 mm).

E value > 2.5 (very easy);

=2.5 to 1.75 (easy);

=1.75 to 1.5 (medium);

=1.5 to 1.25 (difficult);

<1.25 (very difficult).

Re-election is usually carried out in a vertical gravity field, a sloped gravity field, and a centrifugal force field.

In the process of re-election and purification, the factors affecting the re-election index are: mineral density, ore size and shape, medium properties, equipment type and operating conditions.

3. Flotation

Flotation is a beneficiation method that separates minerals in a gas-liquid-solid three-phase interface system by utilizing the difference in mineral surface properties (hydrophobicity or hydrophilicity).

The wetting of the surface of mineral particles is caused by the dipole polarity of the water molecular structure and the crystal structure of the mineral. The wettability is the degree to which the mineral is wetted by water. Minerals that are easily wetted by water are called hydrophilic minerals, and minerals that are not easily wetted by water are called hydrophobic minerals. The wettability of the mineral determines whether the ore can adhere to the bubble when it collides with the bubble, that is, the wettability determines the natural floatability of the ore. Minerals with a strong surface wettability (hydrophilic minerals) have poor natural floatability; otherwise, natural floatability is good; the wettability of mineral surfaces—that is, the degree of hydrophilicity or hydrophobicity is usually measured by the contact angle.

The flotation separation of ore minerals is limited by the natural floatability of the mineral surface. It is usually necessary to use a certain flotation agent to make the minerals easily contact with the bubbles, that is, to improve the floatability of the minerals, and the flotation agent is solid. The adsorption of the liquid interface affects the floatability of the mineral, which is affected by the electrical properties of the mineral surface; therefore, the electrical properties of the mineral surface are inextricably linked to its floatability.

Table 2-1 Common Pharmacy in Flotation Process

(1) Foaming agent. Organic surface active substances distributed at the water-air interface, such as commonly used pine oil, cresol oil, alcohols, and the like.

(2) Collecting agent. Its role is to change the hydrophobicity of the mineral surface, allowing the floating mineral particles to adhere to the bubbles. According to their action properties, they are further classified into non-polar collectors (hydrocarbons), anionic collectors (such as fatty acids, etc.), and cationic collectors (such as fatty amines).

(3) Adjusting agent. Including activators and inhibitors, changing the properties of the surface of the ore particles, affecting the role of minerals and collectors, and adjusting agents are also used to alter the chemical or electrochemical properties of the aqueous medium, such as changing the pH of the slurry and the collector therein. status. The conditioning agent is typically an inorganic compound.

However, in practical applications, many organic flotation agents often have both foaming and trapping properties. One agent acts as a foaming agent in one process and in the form of a collector in another process. Appear, if classified by purpose, it will inevitably cause confusion. Therefore, when discussing or introducing the problem of flotation reagents, it is reasonable to use the basic classification of organic chemistry, or to classify functional groups of organic compounds, and to properly consider the use in flotation practice.

New flotation process - sorting technology for ultrafine particles

Micron-sized mineral particles (particle size less than 10 microns), due to small mass, large specific surface area, high surface energy, and strong surface electrical properties, the sorting effect is poor with conventional beneficiation process.

Sorting technology for ultrafine particles:

Shear flocculation flotation; carrier flotation; emulsification flotation; oil agglomeration separation; polymer flocculation separation.

4. Magnetic separation and electrification

Magnetic separation is a purification method in which different minerals are separated by using magnetic differences between minerals in an inhomogeneous magnetic field. Used for the selection of ferrous metal ores and the selection of colored and rare metal ores. Magnetic non-metallic minerals, i.e. is removed from the non-metallic mineral material such as iron-containing magnetic impurities, non-metallic mineral to achieve the purpose of purification.

Electro-election is a beneficiation method that utilizes the electrical differences of various minerals to achieve mineral separation in a high-voltage electric field. It is widely used in the sorting of colored, ferrous and non-metallic minerals.

Mineral magnetic separation process

Magnetic separation is performed in a magnetic separation device . After the selected ore is fed into the sorting zone of the magnetic separation equipment; the mineral particles are subjected to the combined action of magnetic force and mechanical force (including gravity, centrifugal force, water flow force, etc.), and the magnetic particles with different magnetic properties are subjected to different magnetic forces. The magnetic particles with strong magnetic properties are magnetized under the action of non-uniform magnetic field, resulting in strong magnetic force f magnetic, f magnetic is greater than f machine; magnetic weak or non-magnetic mineral receives little magnetic force (f'magnetic), f' Magnetic is less than f machine. Since the combined force of magnetic force and mechanical force acting on each mineral particle is different, magnetic separation of magnetic strong minerals and weak magnetic minerals (non-magnetic minerals) is realized, and the necessary conditions for separation are as follows:

Fmagnetic>f machine>f'magnetic

f magnetic - the magnetic force acting on the ferromagnetic mineral;

f machine - the combined force of all mechanical forces in the opposite direction of the magnetic force;

F'magnetic - the magnetic force acting on the weak magnetic mineral particles;

High gradient magnetic separation and superconducting magnetic separation

High gradient magnetic separation

The high gradient magnetic separator is also a wet strong magnetic separator, which obtains a large magnetic field force in two ways, namely, the magnetic field strength H and the magnetic field gradient. The gradient is determined by the use of a special magnetically permeable medium, steel wool, which greatly increases its magnetic field force.

Superconducting magnetic separation

The superconducting magnetic separator changes its magnetic material from ferromagnetic to superconductor. The structure can be divided into three systems: superconducting magnetic system, refrigeration system and sorting system.

The horizontal string reciprocating high gradient superconducting magnetic separator is composed of a solenoid type superconducting magnetic system, a sorting tank, a ferromagnetic screen, a hydraulic reciprocating device and a machine base.

Horizontal string tank reciprocating high gradient superconducting magnetic separator sorting process: during operation, the superconducting magnet is excited, and a sorting tank is located in the magnetic field cavity to give the pulp, capture the magnetic particles, and wash the magnetic medium. Another sorting tank is located in the corresponding magnetic screen cavity to wait for work. When the reciprocating canister withdraws from the magnetic field by the reciprocating transmission device, it reaches the corresponding magnetic screen cavity and punches out the magnetic particles on the medium. Another sorting tank, which was originally parked in the magnetic chamber, enters the human magnetic field and repeats the process of repeating the previous sorting tank. This method allows the superconducting magnet to work like a permanent magnet without consuming energy, minimizing the energy consumption of the refrigeration system.

Electrical selection is performed in the electric field of the electric sorter. After the mineral particles are fed into the electric field, due to the difference in electrical conductivity, the ore particles in the electric field carry some kind of electric charge or a different amount of electric charge in some way. Thereby subject to different electric field forces to achieve separation. In addition to the electric field force in the electric field, the mineral particles are also combined by centrifugal force and gravity. The electric field force of the ore particles is expressed as Coulomb force f1, non-uniform electric field force f2, interface attractive force f3 (the residual charge of the charged ore particles and the induced charge between the corresponding positions on the cylinder surface). The gravity is mg and the centrifugal force is f.

5. Non-metallic ore processing examples

5.1. Beneficiation and purification of siliceous raw materials

In addition to the main mineral quartz, siliceous raw materials are usually accompanied by impurity minerals such as feldspar, mica, clay and iron.

The purpose of ore dressing and purification is to improve the purity of the product and reduce the impurity content by using appropriate beneficiation methods and processes according to the different requirements of the product on the particle size and impurity content.

The beneficiation and purification of quartz sand is carried out according to the contents of impurities A1203, Fe203, Ti, Cr, etc., and the particle size requirements.

Commonly used purification methods and processes include: grinding, sieving, scrubbing, heavy, magnetic, floating and electric selection, acid treatment, and the like.

It is generally believed that harmful substances are iron impurities and aluminum impurities, so the progress and development of the purification method and process of siliceous raw materials are mainly reflected in the effective removal of iron and aluminum.

(1) Removal of iron

Iron is mainly present in five forms in siliceous materials:

In the form of fine particles, it is present in clay or kaolinized feldspar;

Attached to the surface of the quartz particles in the form of an iron oxide film;

Iron mineral or iron-containing mineral;

Occurred in the interior of the quartz particles in a diffused state;

It exists in the solid crystal state inside the quartz crystal.

1 screening, grading

In order for the product to reach the corresponding particle size index, the siliceous material must be sieved and classified.

Screening and grading can also act to remove mud to reduce iron impurities.

2 scrubbing, re-election

Scrubbing is a beneficiation method for removing thin film iron, bonding and muddy impurity minerals on the surface of quartz sand by means of mechanical force and grinding and stripping force between sand grains.

There are mainly methods such as rod scrubbing, mechanical scrubbing and ultrasonic scrubbing.

The re-election method mainly uses the characteristics of impurity minerals and quartz to have a large difference in density, and the re-election includes three types: water-eluting mud, hydraulic classification and shaker beneficiation. The commonly used equipment is mainly a spiral concentrator. , chutes and shakers.

3 magnetic separation

The purpose of magnetic separation is mainly to remove iron and magnetic impurity minerals in the siliceous material, and there are two methods of wet and dry magnetic separation.

4 acid treatment

The acid treatment is a chemical treatment method in which quartz is insoluble in acid (except HF), and other impurity minerals can be dissolved by the acid solution, thereby realizing further purification of quartz. Acids commonly used in acid treatment include sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, etc.; reducing agents include sulfurous acid and salts thereof.

5 microbial leaching

Mineral microbial processing technology is a new mineral processing technology that has recently been developed. Microorganisms have achieved good results when the thin film iron on the quartz surface is immersed.

(2) Removal of aluminum

The aluminum impurities in the siliceous material are mainly derived from feldspar and clay minerals.

The alumina component in the clay mineral can be removed by a scrubbing, fractional degreasing process;

For aluminas present in feldspar and other minerals, flotation and electro-election are mainly used to achieve the purpose of removing alumina.

1 flotation

For the impurity particles in the quartz particles which are impregnated or lenticular, and minerals such as feldspar, mica, hornblende, pyrophyllite and kaolin are generally removed by flotation, and the iron mixed in the coarse grinding can also be removed by flotation. Impurity impurities.

Commonly used flotation methods are:

Sulfuric acid is used as a pH adjuster and a sulfuric acid flotation method using DWBE and SHN as a mixed collector;

a hydrofluoric acid method in which hydrofluoric acid is an activator and an amine cation collector;

YS or SHN is an anionic flotation method of a collector.

Due to environmental reasons, in recent years, non-fluorine and acid-free processes have been vigorously developed at home and abroad.

2 electrostatic dressing

A beneficiation process that utilizes different electrical properties between different materials to achieve separation of minerals and impurities in an electric field is called electro-election. Minerals are classified into three categories based on the conductivity: conductor minerals, semiconducting minerals, and non-conducting minerals.

Factors affecting electrification can be divided into two categories: electrical selection equipment parameters and material properties.

3 RF dielectric dressing

The radio frequency dielectric beneficiation technology is a beneficiation method that utilizes the different forces of the material in the radio frequency electric field to achieve the sorting effect. It was developed from the laboratory's dielectric separation technology.

5.2. Feldspar processing technology

Different beneficiation methods are used depending on the type and nature of the feldspar deposit. Generally, it is crushed and ground after hand selection, and then magnetic separation is used to remove iron minerals.

In recent years, with the reduction of feldspar mines, the decline of quality, the continuous improvement of product quality requirements, and the development of comprehensive mine recycling, the introduction of more complex sorting, such as re-election, electrification, flotation, high-gradient magnetic separation Work to remove associated minerals such as quartz, mica, and iron-containing titanium .

Process of mineral processing principles:

(1) High quality feldspar produced in pegmatite

Hand-selected crushing grinding (or water milling) grading products

(2) Feldspar in weathered granite

Washing, crushing, grinding, grading, flotation (except iron, mica; quartz, feldspar separation)

(3) feldspar in fine-grained rock (generally containing mica, iron, etc.)

Broken grinding, screening, magnetic separation

(4) feldspar sand mine

Water-eluting mud screening (or flotation separation of quartz, etc.)

Mineral processing example

1 Hubei Changshi Mine

The main minerals are: micro-plagioclase (39.9%), albite (19.6%), quartz (32.8%), mica (7.8%), containing a small amount of schist debris, garnet and continuum minerals.

Test recovery: feldspar, quartz and mica

The test flow is shown in Figure 1. Test indicators: K2O and Na2O content increased from 7.27% to 12.12%; Fe2O3 decreased from 0.42% to 0.15%.

2 Tangshan Ceramics Co., Ltd.

The feldspar mine produced from pegmatite is processed into feldspar powder for daily use ceramics. The original processing flow is:

Hand selection crushing water mill grading dewatering products

In order to improve the product grade, it mainly solves the iron removal and improves the production capacity, and entrusts Wuhan University of Technology to carry out technical transformation on the production process of feldspar. The experimental process is recommended as shown in Figure 2.

The Fe2O3 content of feldspar concentrate decreased from 0.27% to 0.10%, and the yield reached 86.11%.

5.3. Purification of bentonite

The purification methods of bentonite are generally classified into physical purification methods and chemical purification methods. The physical purification method is the method of beneficiation and purification, which is divided into hand selection, air selection (dry purification) and water selection (wet purification).

(1) Hand selection

Hand selection is mainly used for bentonite with high content of ore montmorillonite. In the mining field, the large waste rock in the ore is manually selected, and it can also be divided into sections and stratified mining according to the technical requirements of the application field, stacked separately and processed separately. The processing flow is as follows:

According to the ore content of bentonite, the soft bentonite does not need to be broken, and the hard bentonite must be crushed into pieces with a particle size (Φ) of about 2 cm by using a jaw crusher or a Raymond mill ; then the water is removed by natural or heat drying. (Water content ≤ 12% ~ 6%); hand selection or use of vibrating screen to remove large Φ ≥ 2cm; finally use Raymond mill to crush fine ore (about 200 mesh). According to the ore content of bentonite, the soft bentonite does not need to be broken, and the hard bentonite must be crushed into pieces with a particle size (Φ) of about 2 cm by using a jaw crusher or a Raymond mill ; then the water is removed by natural or heat drying. (Water content ≤ 12% ~ 6%); hand selection or use of vibrating screen to remove large Φ ≥ 2cm; finally use Raymond mill to crush fine ore (about 200 mesh).

(2) Dry purification

Air separation (dry purification) is a commonly used method for purifying bentonite. This method is suitable for ore with high montmorillonite content (more than 80% montmorillonite content), fine grain size, gangue mineral quartz and coarse feldspar. . The process is as follows: bentonite ore natural dry airflow dry crushing powder packaging wind selection grading

First, by natural drying, the water content of the ore is reduced from 40% to less than 25%; then the ore is broken to 3 to 4 cm; and further dried by a dryer to make the moisture content of the bentonite less than 6% to 12%. In order to prevent the performance change of bentonite caused by the montmorillonite structure change, the drying temperature should be lower than 250 ° C, and the time is not too long.

After grinding it to 100-325 mesh by Raymond mill, it is classified by a gas classifier, and at the same time, sand minerals such as feldspar and quartz are removed, and the final product is obtained.

(3) Wet purification

For low-grade bentonite with a montmorillonite content of only 30% to 80% in the ore, or a bentonite containing a small particle size of feldspar or quartz, it is necessary to obtain a higher purity bentonite or montmorillonite, which is often purified by wet method. . The process is as follows: bentonite original soil crushing pulping (plus dispersing agent) sedimentation separation suspension centrifugal separation (plus flocculation) filtration drying dispersing depolymerization packaging

The degree of purification of bentonite is directly related to the phase composition, structure and particle size of bentonite ore. Therefore, there are many factors affecting the wet purification. For example, different solid-liquid ratios, the number of revolutions of the centrifuge and the centrifugation time, the type and amount of the dispersant added (flocculant), and the temperature of the bentonite will affect the quality of the final product. . Therefore, it is necessary to select an appropriate purification method according to the mineral characteristics of the original soil.

(4) Chemical purification

Since it is difficult to remove the fine-grained cristobalite, part of quartz and Fe2O3 by the physical method of purifying bentonite, it is necessary to adopt a chemical purification method to obtain a high-purity bentonite.

The chemical purification method is a method in which a chemical reagent is chemically reacted with an impurity mineral in bentonite to remove it, and the method is generally to remove cristobalite and quartz by a strong alkali, and the reaction principle is:

The purification experiment of bentonite from Liu house in Jilin Province showed that 20% NaOH solution was added to the original soil at an appropriate ratio (according to the content of cristobalite in bentonite) at a temperature of 80 ° C and a reaction time of 2.5 h. Cristobalite in bentonite can be removed. After purification, the montmorillonite content can reach more than 95%.

The use of sodium dithionite (commonly known as insurance powder) or hyposulfite to eliminate Fe2O3 to achieve bleaching of clay.

(5) Composite purification

In the actual purification process, physical and chemical methods are often used for composite purification. For example, the British patented bentonite purification technology is a composite purification. The main steps are as follows:

1 Processing the mined bentonite ore, with less surface pollution;

2 After the original ore is crushed, it is bleached with sodium dithionite or hyposulfite to eliminate iron oxide pollution;

3 treating the free iron oxide in the bentonite water-based solution with alkali at 60 ° C to dehydrate the treated bentonite suspension;

4 Rinse the dehydrated solid phase material and add water to reconstitute the suspension;

5 subject the newly configured suspension to shear, friction and impact in the homogenizer;

6 Dry the suspension.

5.4. Kaolin processing technology

Although the processing technology of kaolin in papermaking in China is different everywhere, the overall process is similar.

Main production process

(1) Water or pulp

(2) Spiral classifier sand removal

(3) Hydraulic cyclone sorting

(4) Horizontal snail centrifuge classification

(5) Magnetic separation

(6) Chemical bleaching

(7) Pressure filtration

(8) Drying

The main production equipment

Including pulverizer, spiral classifier, hydrocyclone, decanter centrifugal classifier, disc separator, high gradient magnetic separator, filter press, dryer.

Main product quality indicators

China's current quality indicators for kaolin products for papermaking are as follows:

Al ₂ O ₃ 37.5%, SiO ₂ 47%, Fe ₂ O ₃ 0.6%, loss on ignition 15%, <2 μm content 90%, 45 μm sieve residue 0.02%, whiteness > 87%, dispersion sediment 0.02%, abrasion The value is 3 mg, the viscosity concentration (500 mPa.s solid content) is 67%, the pH value is 4 to 7, and the water content is <2%.

5.5. Processing technology of heavy calcium carbonate

The raw materials for producing heavy calcium carbonate are mainly high-purity limestone, marble, calcite , chalk and the like. Limestone is the most common raw material for the production of heavy calcium carbonate, but it is required that the content of silicon and acid insolubles must be less than 1.0%. Generally, the content of calcium carbonate in the raw material is required to be 97% or more. In addition, whiteness is another important indicator to measure the quality of raw materials. Paper, paint, plastics and other applications generally require that the whiteness of heavy calcium carbonate raw materials reach more than 90%.

The processing of heavy calcium carbonate is mainly pulverization, ultrafine pulverization, classification and surface modification. The following mainly introduces the ultrafine pulverization and surface modification processes. There are two kinds of superfine pulverization processes for heavy calcium carbonate at home and abroad: dry method and wet method. The dry process is generally used to produce D97 ≥ 3 ~ 5μm products, and the wet process is generally used to produce D97 ≤ 3 ~ 5μm (D90 ≤ 2μm) products.

(1) Dry production process

The heavy calcium carbonate dry processing equipment mainly includes Raymond mill (or suspension roller mill), ball mill , agitating mill, vibrating mill, press roller mill, mechanical impact mill and jet mill.

Among them, Raymond mill is widely used for the production of 38-74μm (200-400 mesh) products, and is also used to produce D97=30～15μm (500 mesh～800 mesh) products after modification and configuration of fine classifiers;

The ball mill is the main equipment of the large-scale heavy calcium carbonate production line. It is equipped with various classifiers to produce D97 products of 5μm, 10μm, 16μm, 45μm and so on.

The vibration grinding configuration fine grading equipment is mainly used to produce D97 products of 5μm, 10μm, 16μm, but its single machine production capacity is not as good as ball mill;

The mechanical impact mill is simple in process but low in output, and is mainly used in small and medium-sized heavy calcium carbonate production plants;

Dry-type agitating mills are used in large-scale heavy calcium carbonate production plants in Europe, but they are rarely used in China; press-rolling mills have so far only been used by a few manufacturers.

(2) Wet production process

The wet production process is mainly used to produce ultra-fine heavy calcium carbonate of D97≤5μm (D90≤2μm) for papermaking and paint coating. The production equipment is mainly various types of wet mixing grinding, stripping machine, sanding machine and spiral mixing mill. Generally, one or two to three continuous ultrafine pulverization processes are used.

5.6. Dressing and purification of wollastonite

Wollastonite is a metamorphic mineral. The main minerals associated with it are calcite, diopside , garnet , tremolite , Fushan stone, quartz, chalcopyrite, and porphyrite. The method of dressing of wollastonite varies with the type of ore. Hand selection, photoelectric sorting, magnetic separation, flotation, electro-election and re-election are widely used in the beneficiation and purification of wollastonite.

5.7. Processing technology of powder quartz

The natural powder quartz is separated into silt, de-sludge and decontamination, super-segmentation, selective purification, dehydration drying and surface modification, etc., which can be used as a series of powder quartz products such as rubber, plastic filler and electrical material.

5.8. Processing technology of diatomite

Natural high purity diatomaceous earth mines are rare. Most diatomite ore is subject to beneficiation to meet the needs of the application. The purpose of diatomite beneficiation is to remove detrital minerals such as quartz and feldspar, iron oxide minerals, clay minerals and organic matter to enrich diatoms.

The selection of the ore dressing method depends on the type and nature of the impurity minerals and the purity requirements of the products.

For diatom original soils containing mainly quartz and feldspar crumb minerals with little clay content and high diatom content, a simple cyclone separation method can be used, that is, cyclone separator or air is used after drying and selective pulverization. Centrifugal sorting machine for sorting; it can also be sorted by wet gravity sedimentation or centrifugal sedimentation. The principle process is: diatom original soil→ scrubbing pulping→ gravity sedimentation or centrifugal sedimentation; if the original soil contains iron Minerals can be added to magnetic separation and iron removal after gravity or centrifugal sedimentation.

5.9. Graphite flotation process

Graphite flotation practice

(1) Nanshu Graphite Mine. Shandong Nanshu Graphite Mine is one of the important graphite producing areas in China, with an annual output of 20,000 tons of medium carbon graphite and 7,000 tons of high carbon graphite.

The ore grade (fixed carbon content) is about 4%, and the gangue minerals are feldspar, quartz, diopside, tremolite, mica, chlorite, pyrite, rutile, ilmenite, magnetite and the like. Graphite scales are distributed in quartz and feldspar mineral particles or joint fissures, and are closely symbiotic with fibrous minerals such as tremolite, actinolite, biotite, etc., graphite scales are generally 1.0-5mm, in the graphite ore body fracture zone There is a small amount of cryptocrystalline graphite.

According to years of production experience, the mine uses 4 times of re-grinding and 6 times of selection process. In order to improve the grinding effect, the re-grinding machine will be concentrated by cyclone, and the fourth re-grinding mill will be used. The grade of the mine is 89%.

The general development trend of non-metallic mineral dressing is:

Conventional mineral processing methods, processes and equipment suitable for non-metallic mineral processing characteristics will be gradually promoted, applied and developed;

In order to meet the stricter quality requirements of non-metallic mineral raw materials for new ceramics, engineering plastics, optical fiber and other new materials, non-metallic ore dressing will move toward high-purity and ultra-fine technology fields;

Further development and promotion of high-efficiency beneficiation equipment; application and development of various mineral processing methods in the treatment of non-metallic ore refractory ore; various new technologies (such as superconducting, ultrasonic, laser, etc.) in non-metallic ore dressing Application and application of modern detection technology.

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