How to avoid the failure of the ultra-fine grinding machine?

Grinding equipment such as ultra-fine pulverizers will inevitably have various failures in use, and during the construction process, once the ultra-fine pulverizer is accidentally damaged during the grinding operation, the entire process will be caused. The process delays production. How can we avoid the failure of the superfine mill?

1.   Reduce the wear of wear-resistant parts of the ultra-fine pulverizer, and the feed should not be too large during the running-in period of the ultra-fine pulverizer, so as not to affect the normal state of the parts. The solution is to carry out reasonable feeding in strict accordance with the use standards.

2.  After the installation of the ultra-fine mill, there will be an empty machine for commissioning, and you can check whether the various parts are installed in place. If there is a deviation of geometric shape and matching size between the parts, it will be affected by alternating loads such as impact and vibration, as well as heat, deformation and other factors during use, which will affect the production efficiency of the ultrafine mill. Therefore, check the bolts of the ultra-fine mill at a fixed time to avoid loosening.

3.  The operator of the industrial pulverizing production line must have a clear understanding of the operation and principle of the equipment, and have an understanding of the performance, structure and parts of the ultrafine mill, and troubleshoot in time to reduce downtime. In addition, the lubrication of the ultra-fine pulverizer also has certain operational requirements. To match the operation of the assembly gap, the lubricant should form a uniform oil film on the friction surface to prevent wear.

Three points should be kept in mind during the use of the superfine mill: reduce wear, avoid looseness, and operate skillfully. Paying attention to these three points will avoid many unnecessary failures.

by ALPA Powder

How to reduce the energy consumption of jet mill

The advantage of the jet mill is that the material after grinding does not produce pollution. After grinding, the compressed high-speed airflow speed decreases and the volume increases. It belongs to the heat absorption process and has a cooling effect on the material. It is especially suitable for ultrafine grinding. Jet mill is to use high-speed airflow to accelerate the particle production speed, collide with each other or collide with the target to crush the material to achieve the grinding effect.

Generally speaking, there are three main ways to accelerate the grinding of solid particles by high-speed airflow:

(1) Airflow particle acceleration nozzle: After the airflow and the particles are fully mixed, the particles can obtain a high speed (almost the same as the airflow speed), but the material wears seriously on the inner wall of the nozzle and is rarely used in practical applications.

(2) The injector accelerates the particles: the high-speed (supersonic) airflow and the particles are mixed and accelerated in the mixing tube, and the particles get a higher speed, but the material wears the mixing tube seriously.

(3) Free airflow accelerates particles: The particles enter the high-speed air stream in the form of free fall. At this time, only the high-speed airflow passes through the nozzle, and the wear is small. However, since the falling speed (lateral) of the particles is very low, it is difficult to enter the center of the air stream (high-speed airflow) to obtain a high-speed airflow.

From this perspective, the efficiency of jet mill mainly depends on the relative collision speed and collision angle of particles in the fluidized bed. Therefore, only by changing the geometry and structural design of the nozzle and grinding cavity can the efficiency of jet mill be improved. To reduce the energy consumption of jet mills and improve production efficiency, we can start with improving the nozzle structure, determining the nozzle spacing, improving the shape of the grinding cavity, and determining the material level of the grinding cavity.

Several uniformly distributed auxiliary nozzles are arranged around the main nozzle to accelerate the material particles around the main nozzle to enter the central area of ​​the main stream to obtain a larger collision velocity. A feed nozzle is arranged in the center of the main nozzle, and the fluidized particles in the fluidized bed are directly sucked into the center of the main nozzle to obtain a high collision velocity.

by ALPA Powder

What is the significance of jet mill in pharmaceutical ultrafine grinding

In the pharmaceutical industry, there are many raw materials with different particle sizes. When these raw materials are processed in the next step, the different particle sizes and uneven density of the powder result in poor fluidity and easy layering. Ultra-fine grinding is the operation process of making a large solid material into an appropriate degree of fine powder. Under the combined action of various forces, the solid material generates stress. Under this stress, the material undergoes elastic deformation. When the stress exceeds a certain limit, the material will undergo plastic deformation. The crushing within the range of elastic deformation is called elastic crushing, and the crushing after plastic deformation is called primary crushing. Generally, polar crystal drugs are easily crushed, and most of them are crushed elastically. On the contrary, non-polar crystal drugs are mostly grinding, which is difficult to grind.

Jet mill can greatly reduce the particle size of solid materials and increase the surface area, which is of great significance to pharmaceutical engineering:

(1) It is helpful to increase the contact surface of solid and liquid dispersion medium, accelerate the dissolution rate of the drug, and improve the utilization rate of the drug;

(2) After the raw and auxiliary materials are micronized, the large particles are broken into fine powder, which facilitates the uniform mixing of several different solid materials, improves the uniformity of the dispersion of the main drug in the particles, and improves the dispersion of the colorant or other auxiliary materials;

(3) The improvement of drug fluidity is helpful to improve the quality of preparations, and it is also convenient to be processed into various dosage forms, which is convenient for dispensing and taking. The grinding process is a physical process, and objects exhibit different hardness and performance due to different cohesion. During grinding, the cohesion between molecules must be partially destroyed by external forces to increase the surface area of ​​the drug, that is, the process of converting mechanical energy into surface energy. The external force used in the grinding process should be determined according to the hardness and performance of the drug.

Jet mill is a mature ultrafine grinding equipment, which is different from other ultrafine grinding equipment. The grinding principle is to use high-speed airflow to bring the animal material particles to move, so that the materials collide, collide, and rub against each other. Under the shearing action of the airflow, the material is ground into fine particles. Jet mills are widely used in ultrafine grinding of powdered medicines. The grinding process is continuous, with large capacity and high degree of automation; and the processed products have narrow particle size distribution, high purity, and particles with good activity and dispersibility.

by ALPA Powder

Application of Jet Mill in the Production of Titanium Dioxide

Titanium dioxide used as a pigment has excellent optical properties and stable chemical properties. Titanium dioxide has very high requirements on particle size, particle size distribution, and purity. Generally, the particle size of titanium dioxide is based on the wavelength range of visible light, which is between 0.15m and 0.35m. And as a white basic pigment, it is very sensitive to the increase of impurities, especially iron impurities, and the increase in crushing is required to be less than 5 ppm. In addition, titanium dioxide is required to have good dispersibility in different coating systems. Therefore, the general mechanical crushing equipment is difficult to meet the requirements, so the final grinding (finished product grinding) of titanium dioxide is currently selected by jet mills at home and abroad.

According to the grinding requirements of titanium dioxide: narrow particle size distribution, less increase in inclusions, good dispersibility, etc., and material characteristics of titanium dioxide: high viscosity, poor fluidity, fine particle size and easy to adhere to the wall, etc. At present, domestic and foreign titanium dioxide manufacturers choose to have self-distribution The flat-type (also known as horizontal disc type) jet mill with high-level function is used as the final grinding equipment for titanium dioxide; and superheated steam is used as the grinding working medium. Because steam is easily available and cheap, the pressure of the steam working medium is much higher than that of compressed air and is also easy to increase, so the flow energy of steam is greater than that of compressed air. At the same time, the cleanliness of the superheated steam is higher than that of the compressed air, the viscosity is low, and there is no static electricity, and while grinding, it can eliminate the static electricity generated by the collision and friction of the material, and reduce the secondary cohesion of the powdered material. In addition, grinding under high temperature conditions can improve the application dispersibility of titanium dioxide and increase the fluidity of titanium dioxide. The use of superheated steam has low energy consumption, which is only 30% to 65% of compressed air. In addition, using a flat jet mill, organic additives can be added to organically modify the surface of the titanium dioxide while pulverizing, so as to increase the dispersibility of the titanium dioxide in different application systems.

With the rapid development of the titanium dioxide industry, the requirements for equipment are getting higher and higher. Under the premise of meeting the process conditions and quality requirements, the large-scale and systematization of equipment is particularly important. Airflow grinding is also continuously improved with the development of titanium dioxide. The production capacity of the gas powder machine has also increased from 1.2t/h to 1.5 t/h at the beginning to the current 2.5 t/h to 3.5 t/h. The production capacity of the gas powder system has also increased from a single line of 10,000 t/a to the current single line 2 Ten thousand t/a, the collection method has also been changed from the relatively backward wet collection to the advanced dry collection, which greatly improves the one-time yield and reduces waste. With energy saving and emission reduction, the higher the requirements for cost reduction, the more reasonable the configuration of the gas-powder system, and the full utilization of the waste heat of the exhaust gas. In the past, the gas and powder collection method was mainly wet collection, that is, the materials from the gas and powder machine first enter the cyclone for vapor-solid separation, and the separated materials are discharged by the star unloader at the bottom of the cyclone for cooling and packaging. The separated material enters the spray tower with the air flow for spray cooling and collection. The material collected by the spray tower is in the form of slurry, which must be settled, filtered and dried before returning to the gas powder machine. The one-time yield of this process is very low, up to 90%, the energy consumption is large, the exhaust heat cannot be used, and it has been basically eliminated. The current gas and powder collection method is mainly dry collection, that is, the material from the gas and powder machine first enters the high-temperature bag filter for vapor-solid separation. The current surface-coated high-temperature resistant filter material has a separation rate of more than 99.5%. The discharged materials are discharged through the star discharger at the lower part of the high-temperature bag filter for cooling and packaging. The separated high-temperature tail gas is discharged from the clean air chamber at the upper part of the high-temperature bag filter and enters the tail gas waste heat recovery device for waste heat utilization.

Factors affecting jet milling equipment

(1) Jet mill: As the most important equipment for jet milling, the quality of the air powder machine directly determines the quality of the product. The gas powder machine is required to have reasonable design, excellent production, high impact kinetic energy, good classification effect, wear resistance and high temperature resistance. Therefore, it is very important to choose a gas powder machine.

(2) Steam quality: The grinding working fluid of jet milling is superheated steam. If the steam quality does not meet the crushing requirements, it will seriously affect the quality of gas and powder. Generally, the requirements of the gas powder engine for steam are: the pressure is 1.6 to 2.0 MPa, and the temperature is between 290°C and 310°C. If the temperature and pressure are lower than the requirements, it will cause low impact kinetic energy, decreased grinding force, insufficient heat in the system, and materials easily damp, which will affect the grinding effect, block the system and make it unable to operate normally; if the temperature and pressure are too high, it will The equipment in the system causes damage.

(3) Process control: Airflow grinding requires stable and continuous operation. The fluctuation of steam and the fluctuation of feed volume should be controlled within a certain range, and must be adjusted slowly during adjustment, and it is strictly forbidden to increase or decrease. In addition, once the gas-powder system is normal, it should maintain continuous operation and avoid frequent startup and shutdown. Furthermore, the operating procedures should be strictly followed when starting and stopping.

(4) System monitoring: In order to ensure the normal operation of the system, necessary monitoring equipment must be installed in a reasonable position of the system to make timely adjustments according to changes in the situation.

by ALPA Powder

Characteristics and applications of advanced ceramic materials- silicon carbide fiber

Advanced ceramics have excellent properties such as high temperature resistance, high strength and rigidity, relatively light weight, and corrosion resistance, but they also have an inherent Achilles heel: brittleness. The use of high-strength, high-modulus continuous ceramic fiber and matrix composite is an effective method to improve the toughness and reliability of ceramics.

At present, jet mill equipment has been used in the preparation of many advanced ceramic materials. However, fiber-reinforced ceramic matrix composites mainly refer to composites made of carbon fiber, graphite fiber, silicon carbide fiber, silicon nitride fiber, zirconia fiber, etc. to enhance magnesium oxide, silicon oxide, silicon nitride, aluminum oxide, zirconia, etc. The material has the characteristics of high high temperature compressive strength, high elastic modulus, strong oxidation resistance, and good impact resistance.

Silicon carbide fiber is a kind of ceramic fiber with high tensile strength, creep resistance, high temperature resistance, oxidation resistance and good compatibility with ceramic matrix. It is used in high-tech fields such as aerospace, aviation, weapons, shipbuilding and nuclear industry. It has broad application prospects.

The ultra-fine powder sintering method is mainly based on silicon carbide powder as raw material, adding a certain amount of binder and sintering aids (B, Al₂O₃, etc.), through physical mixing, dry spinning or melt spinning to make fibers The raw silk is subjected to high-temperature heat treatment to obtain silicon carbide fibers. The silicon carbide fiber prepared by this method has better high temperature resistance and creep resistance, but the fiber diameter is larger and the strength is lower, which is not conducive to industrial application.

Silicon carbide fiber has the advantages of good creep resistance, oxidation resistance, chemical corrosion resistance and compatibility with ceramic matrix. It can be used as a high-temperature structural material of fiber-reinforced ceramic matrix composites and can be widely used in aerospace and other fields.

In addition, the metal matrix composite material reinforced by silicon carbide fiber has better performance in terms of specific strength, specific stiffness, thermal expansion coefficient, thermal conductivity and wear resistance. It is used in aerospace, military weapons and equipment, sports equipment, automobiles, etc. The civil industry has a wide range of application prospects.

by ALPA Powder

Application of Dolomite Powder

Dolomite is a carbonate mineral, including iron dolomite and manganese dolomite. Its crystal structure is like calcite, often in the form of rhombohedrons; bubbles will slowly appear when exposed to cold dilute hydrochloric acid; some dolomites emit orange-red light under cathode ray irradiation. Dolomite is the main mineral component of dolomite and dolomitic limestone.

Dolomite can be used in building materials, ceramics, glass and refractory materials, chemical industry, agriculture, environmental protection, energy saving and other fields. It is mainly used as a flux for alkaline refractories and blast furnace ironmaking; production of calcium magnesium phosphate fertilizer and preparation of magnesium sulfate; and ingredients for the production of glass and ceramics. It is also used as a flux in the glaze. Some ancient kilns in the north, such as Ding Kiln, often add dolomite to the glaze, and dolomite is also added to some glazes in Jingdezhen, which requires a dolomite mill. support.

Dolomite powder is pure white, insoluble in water, with a relative density of 2.5, stable chemical properties, and a slippery feel. As a plastic filler, dolomite powder can improve the hardness, fire resistance, acid and alkali resistance, electrical insulation and dimensional stability of the product. It is widely used in plastics, rubber, cables, paints, coatings, ceramics, EVA, and other industries.

1.   Used in rubber, it can increase the volume of the rubber, improve the processability of the rubber, play a role of semi-reinforcement or reinforcement, and can adjust the hardness of the rubber.

2.  In plastics, it can increase the volume of the plastic, reduce the cost of the product, improve the dimensional stability of the plastic and the hardness and rigidity of the plastic, improve the heat resistance of the plastic, and improve the astigmatism of the plastic.

3.  Used for exterior wall insulation mortar, putty powder, ball factory lawn self-leveling mortar, epoxy floor, exterior wall latex paint, real stone paint, FRP sand pipe, plastic, rubber, paint, coating, etc.

It can be seen that the application market of dolomite has broad prospects.

Dolomite powder processing is generally divided into dolomite coarse powder processing (0-3mm), fine powder processing (20 mesh-400 mesh), and dolomite ultrafine powder deep processing (400 mesh-1250 mesh) and micro powder processing (1250 mesh) -3250 mesh) four types, select the appropriate equipment according to different processing techniques.

by ALPA Powder

Selection of Ultrafine Grinding Equipment for Traditional Chinese Medicine

Ultra-micro grinding generally refers to the process of pulverizing material particles above 3mm to below 10~25μm. After ultra-fine grinding, traditional Chinese medicine has the following advantages: improve the bioavailability of the medicine, improve the dissolution of the medicine, improve the performance of the medicine, reduce the dosage of the medicine, save resources, improve the preparation technology, not easy to produce pollution during processing, high grinding precision, powder Good body shape.

Classification of Chinese medicine

• Plant Chinese Medicine

Starch-based drugs, such as myrtle, mung bean, etc.; fibrous drugs, such as angelica, licorice, etc.; oleaginous volatile drugs, such as frankincense, schisandra, nootropics, etc.

• Animal Chinese Medicine

Such as shark cartilage, silkworm pupae, pearls, etc.;

• Mineral Chinese Medicine

Such as talc and so on.

Application of Chinese Medicine Ultrafine Grinding

Ultrafine grinding of traditional Chinese medicine is widely used, such as wolfberry, Shouwu, American ginseng, licorice, pollen, Ganoderma lucidum, hawthorn nucleus, animal bones, minerals and hundreds of traditional Chinese medicine products can be ultrafine grinding.

Principles of equipment selection

Ultra-fine grinding is not as fine as possible, but to control the powder according to customer or process requirements.

The selection of crushing equipment should be based on factors such as the characteristics of the material to be ground, the output of the material to be ground, the fineness requirements of the material to be ground, the value of the Chinese medicine product of the material to be ground, and the cost of grinding.

Chinese medicine ultrafine grinding equipment

• Mechanical impact mill

An impeller driven by a motor to rotate at a high speed is equipped with a movable blade (or hammer) to grind traditional Chinese medicine. It is suitable for grinding medium-soft and hard Chinese medicines, brittle Chinese medicines such as mineral medicines, and Chinese medicines with a lot of starch, such as rice and mung beans.

Mechanical impact grinding has high efficiency, large crushing ratio, simple structure and stable operation. However, the high-speed operation causes the temperature to rise, and the efficacy of the medicine may be lost, and the passage of the sticky wall may be blocked, and the resulting abrasion may cause the pollution of the medicine.

• Jet mill

The high-pressure airflow is used to make the particles of the ground material violently collide, impact, and friction with each other, and the direct shearing effect of the airflow on the material is used to achieve the grinding effect. Chinese medicine suitable for grinding: brittle Chinese medicine, heat sensitive materials.

The products of the jet mill can be pulverized very fine (particle size up to 1-10μm), narrow particle size distribution range, easy to clean, and low temperature. However, this method is not applicable to medicinal materials containing volatile components, and a certain degree of fineness is required before the powder is ground.

• Vibration mill

Using the medium rotation and medium impact generated by the vibration, the material to be ground is impacted in a positive direction and at the same time subjected to tangential shear, thereby realizing high-energy, high-speed grinding.

The vibration mill has high grinding efficiency, low loss, strong adaptability to the processing object, fully enclosed operation, no dust pollution, and low grinding temperature. However, it is prone to sticking to the wall, and the water content of the material is relatively high.

• Cryogenic Grinder

It is suitable for crushing high value-added Chinese medicinal materials and foods that are difficult to grind at room temperature, easily deteriorated and decomposed by heat, as well as ultra-low melting point, super heat sensitive and super viscous materials (especially animal Chinese medicinal materials with high fat and high protein) )

The low-temperature grinder is non-polluting and has a wide range of applications. However, the crushing cost is very high and is rarely used.

• Knife Grinder

Chinese medicine suitable for grinding fibers.

The knife mill increases the shearing effect, and the grinding efficiency is higher.

• Grinding unit

It is suitable for grinding medicines containing more fiber, lignin, colloidal fat, resin, sugar and other ingredients.

The crushing unit has fine particle size and large output.

Among the above-mentioned various ultra-fine grinding equipments, jet mills and vibration mills are widely used. Among the jet mills, the fluidized bed type jet ultrafine pulverizer is the most widely used. Vibration mill is a kind of ultrafine grinding equipment for traditional Chinese medicine with the most research and application. Vibration mills are mostly used for ultra-fine grinding of animal and plant drugs in Germany and Japan.

Unsolved issues

Pharmaceutical production has its own strict quality inspection standards. General grinding equipment is not directly applicable to the production of medicines. At present, most of the equipment developed and produced is improved from mineral grinding equipment. As for how to prevent cross-contamination during the crushing process, how to achieve cleaning , Disinfection and automation control, etc., are all under study.

Since traditional Chinese medicine has certain medicinal properties and at the same time, it has certain toxicity. When the medicinal properties are fully displayed after ultra-fine grinding, further research is needed for its toxicity.

by ALPA Powder

The particle size of the heavy calcium carbonate powder is more uniform by using the air classifier

It is well known in the industry that there are different processes for the processing of heavy calcium carbonate powder in dry and wet methods. Dry processing is more conducive to achieving industrial scale and a certain degree of product refinement. Therefore, many companies have chosen to use air classifiers to obtain more refined heavy calcium carbonate powder.

The heavy calcium carbonate powder with uneven thickness moves to the classification area at high speed from the inlet of the lower end of the air flow classifier with the updraft under the suction force of the fan. Under the action of the strong centrifugal force generated by the high-speed rotating classification turbine, the coarse and fine materials are separated. The fine particles that meet the particle size requirements enter the cyclone separator or dust collector through the gap of the grading wheel blades, and the coarse particles entrain the part of the fine particles after hitting the wall. The speed disappears. The washing action separates the coarse and fine particles, the fine particles rise to the classification zone for secondary classification, and the coarse particles fall to the discharge port.

The particle size of the heavy calcium carbonate powder processed by the air classifier is more concentrated, and the heavy calcium carbonate powder processed by the air classifier is more widely used:

1.   Heavy calcium powder for artificial marble industry: 325 mesh, whiteness requirement: 95%, calcium carbonate content: 98.5%, pure and no impurities. Calcium carbonate has been widely used in the production of artificial marble.

2.   Heavy calcium powder for floor tile industry: 400 mesh, whiteness requirement: 95%, calcium carbonate content: 98.5%, pure and no impurities. Calcium carbonate can be used in the floor tile industry to increase the whiteness and tensile strength of the product, improve the toughness of the product, and reduce the production cost.

3.   Heavy calcium powder for paper industry: 325 mesh, whiteness requirement: 95%, calcium carbonate content: 98%. The important role of calcium carbonate in the paper industry: it can ensure the strength and whiteness of the paper, and the cost is low.

4.   Heavy calcium powder for construction industry (dry mortar, concrete): 325 mesh, whiteness requirement: 95%, calcium carbonate content: 98%. Calcium carbonate plays an important role in concrete in the construction industry, not only can reduce production costs, but also increase the toughness and strength of the product.

5.   Heavy calcium powder for fire-proof ceiling industry: 600 mesh, whiteness requirement: 95%, calcium carbonate content: 98.5%. Calcium carbonate is used in the production process of fireproof ceilings, which can improve the whiteness and brightness of the product, and the fireproof performance will also increase.

by ALPA Powder

The processing and application of talc

The color change of talc is mainly caused by impurities. The more impurities, the darker the color. The pure ones are white, and the impurities are slightly yellow, pink, light green, light brown and other colors. The dense block has a shell-like fracture, the relative density is 2.58-2.83, and it is rich in slippery, with a glassy luster, the cleavage surface is pearly luster, and the cleavage sheet is flexible (flexibility refers to the flaky cleavage Minerals, its thin slices can be significantly bent without breaking under the action of boundary forces, but cannot be restored to their original properties after the external force is removed).

There are few natural pure talc mines, and the common associated minerals are chlorite, serpentine, magnesite, tremolite, and dolomite.

The theoretical chemical composition of talc is 4.75% H₂O, 31.68% MgO and 63.47% SiO₂.

Molecular structure of talc                                        The microstructure of talc

Physical and chemical properties of talc

• Physical properties

Adsorption: oil absorption is 49%~51%;

Thermal performance: Refractoriness is as high as 1490-1510 ℃;

Electrical insulation performance: When iron-containing minerals appear, the insulation performance is reduced;

Coverage: Ultra-fine talcum powder can form a fire-resistant and weather-resistant film;

Chemical stability: Generally speaking, it does not react with strong acids and bases;

Other properties: low hardness and strong slippery feeling; when the impurity minerals increase, the lubricating performance will decrease obviously; the talc is dense and low in hardness, and has good mechanical processing and carving performance.

• Chemical nature

The chemical composition is relatively stable. Si is sometimes replaced by Al or Ti (Al can reach 5%, Ti can reach 0.1%), Mg is often replaced by Fe and a small amount of Mn, Ni, Al (FeO reaches 5%, Fe₂O₃ reaches 4.2% , NiO up to 1%), sometimes containing a small amount of K, Na, Ca, these elements may be located between the talc layers or mechanically mixed, the variant of iron-rich end members-iron talc, containing FeO up to 33.7%.

Classification of talc

Talc can be divided into block talc (talc content>70%), talc rock (talc content 30-70%), talc rock can be divided into talc-chlorite rock, talc-carbonate rock.

• Talc

• Talc rock

According to its mineral type, it can be divided into chlorite rock and carbonate rock.

Chlorite rock contains chlorite, sometimes serpentine and pyroxene, with darker color and greater hardness than talc. The carbonate symbiotic minerals include magnesite, dolomite, calcite, etc., which are generally lighter in color and much harder than talc.

Talc processing technology

• Beneficiation and purification

Beneficiation and purification include flotation (talc has good natural floatability), manual sorting (talc and gangue minerals have different slippery properties), electrostatic beneficiation (talc is negatively charged and has different electrical properties from impurity minerals), magnetic separation (using magnetic Selecting and removing iron-containing minerals), photoelectric sorting (the surface optical properties of talc and impurity minerals are different), crushing and screening (the crushing methods of talc and gangue minerals are different).

• Fine grinding and superfine grinding

Talc is finally applied in powder form, therefore, fine grinding and ultra-fine grinding are one of the necessary processing techniques for talc. Talc has a Mohs hardness of 1, which is naturally crushable and has good grindability. At present, the processing of ultrafine talc powder mainly adopts a dry process. Although wet pulverization has been studied, it is rarely used in industry.

Dry grinding equipment includes impact mill, jet mill, vortex mill, vibration mill, stirring mill, and tower mill.

The principle of jet pulverization process of talc is: talc block→coarse crushing→drying→medium crushing→fine grinding (Raymond mill)→superfine grinding (jet mill)→cyclone aggregate→package, the product fineness can reach 500~5000 Item.

The mechanical impact superfine crushing process of talc is: talc block→crushing (hammer crusher)→mechanical impact superfine crusher→turbine type fine classifier→cyclone aggregate→packaging.

• Surface modification

The modification of talc mainly adopts dry modification process, and the surface modifiers used mainly include paraffin, titanate, zirconium aluminate coupling agent, silane coupling agent, phosphate ester, and various surface modifiers.

• Calcined

The calcining is mainly for black talc, and the calcining temperature is generally 600~1200℃. In this temperature range, the higher the temperature, the higher the whiteness of talc after calcination, and the maximum whiteness of calcination can reach more than 90.

Resource distribution of talc

The prospective reserves of talc in the world are more than 2 billion tons, and the proven reserves are about 800 million tons, covering more than 40 countries. Countries with large proven reserves are: Finland, China, the United States, Russia, and France.

There are 250 known talc deposits in the world, of which 80 are currently being mined. Among these 80, 40 have an annual output of more than 5,000 tons, and the current world's annual output is about 6 million tons.

Application of talc

• Papermaking

Ultrafine talc can be used together with kaolin, calcium carbonate, and titanium dioxide pigments to control the matt, ink, gloss, brightness and opacity of paper.

• Plastic, rubber, cable

• Ceramics and refractory materials

It can be used as ingredients to effectively control the thermal expansion of the ceramic body, and as a glaze can provide a cheap source of magnesium oxide. It can be directly processed into plates and can be used as furnace lining and kiln lining.

• Coating

Talc can be well dispersed in both polar and non-polar matrix, and at the same time has chemical inertness and high oil absorption.

• Textile

Used as filling and brightening agent and lubricant in textiles.

• Cosmetic

Various emollient powder, beauty powder, talcum powder, etc.

• Medicine, food

Medicine tablets, sugar coatings, prickly heat powder, Chinese medicine prescriptions, food additives, release agents, etc.

• Other

Carriers for pesticides and fertilizers, arts and crafts, release agents, waterproof ointments, etc.

by ALPA Powder

The processing technology and application of diatomite

Diatomite is deposited 10,000 to 20,000 years after death to form diatomaceous earth. Diatomaceous earth is a kind of biogenic siliceous sedimentary rock, which is mainly composed of the remains of ancient diatoms. It is soft, loose, delicate, porous and light, and has adsorption properties. Sex, permeability.

Diatomaceous earth has an amorphous structure with a large number of micropores, and the number of micropores per unit area is thousands of times higher than that of charcoal. Common microstructures include straight chain type, round screen type, feather pattern and crown plate type.

According to the different mineral content in the ore, diatomaceous earth is divided into diatomaceous earth, clay-containing diatomaceous earth, clay diatomaceous earth, and diatomaceous clay.

Diatomite deposits are divided into marine deposits and continental lacustrine deposits according to their formation conditions. Diatomite mineral products are divided into A type fine ore with a particle size less than 0.25mm and B type lump ore with a particle size greater than 0.25mm according to the particle size. Diatomite is divided into first grade, second grade, and third grade according to product quality.

Diatomite processing technology

Natural high-purity diatomaceous earth ore is rare, and most of them require ore dressing and purification before they can be used. The beneficiation method is determined by the type and nature of impurity minerals and the purity requirements of the product. The method of beneficiation includes physical method (wet method, dry method) and chemical method (acid leaching method, calcination method).

• Physical method

The wet beneficiation process is often used for low-quality ore. The process is raw earth ore → scrubbing pulp → dilution → sedimentation separation → negative pressure dehydration → hot air drying → fine classification → diatomaceous earth.

The dry beneficiation process is often used for high-quality ore. The process is raw earth ore→crushing→mixing→grinding→drying→grinding→drying→air separation and classification→diatomite.

• Chemical method

Physical beneficiation and purification can only improve the purity of diatomite, and it has little effect on increasing the specific surface area. Chemical methods can remove organic impurities and structured water, and improve the purity of diatomaceous earth.

The process flow of the acid leaching method is raw earth ore → roughing → stripping → acid leaching treatment (acid) → sedimentation and separation → filter press → washing → drying → diatomaceous earth.

The calcining process can purify diatomaceous earth alone, or it can be used in conjunction with other processes. The calcining method is divided into room temperature calcining and flux calcining. The calcining temperature is between 600°C and 800°C, and flux is added for flux calcining. The process flow of the calcination method is raw earth ore → roughing → calcination to remove impurities → jet pulverization → classification → diatomaceous earth.

Application of diatomite

• Water treatment industry

Porosity and adsorption are used as adsorbents to treat sewage in water treatment.

• Building Materials Industry

Production of thermal insulation materials and lightweight building materials.

• Rubber industry

Used as a reinforcing agent and filler. Improve the physical properties of rubber products and enhance durability.

• Coating industry

Used as a matting agent and filler. It can improve the dispersibility of the coating, and it is not easy to aggregate and precipitate. At the same time, diatom mud is also a new type of environmentally friendly green coating material.

• Paper industry

Used as a functional filler, based on the good physical and chemical properties of diatomaceous earth, it can be used to produce functional paper.

• Agriculture field

Diatomaceous earth itself is an insecticidal pesticide. It can also be used as a carrier and anti-caking agent for pesticides or fertilizers. The use of fertilizers can also improve fertilizer efficiency.

• Petrochemical industry

Used as the carrier of various catalysts, such as the carrier of nickel catalyst in hydrogenation process.

• Other industry

Diatomaceous earth is used as filter aid or porous ceramic filter element is widely used in the production and filtration of daily necessities such as medicine, wine and sugar.

by ALPA Powder