Limestone Powder Grinding Process
Limestone is the main raw material for producing cement, concrete coarse and fine aggregates, lime, calcium carbonate, etc. Its crushing and grinding generally adopt dry process, and the corresponding process is selected according to different application fields:
For limestone used in metallurgy and road construction, the ore is generally crushed and screened.
For fine powder products used as feed additives and ordinary fillers, the ore is generally crushed by granular crusher, hammer crusher, impact crusher, etc. and then directly ground by Raymond mill, vertical mill, roller mill, impact mill, etc.
For ultrafine limestone powder and high-grade fillers used for flue gas desulfurization, ultrafine crushing and fine classification are generally required, and the process equipment is basically the same as the ultrafine crushing of calcite.
At present, most of the limestone powder used in the building materials industry is limestone or stone chips generated in the production of aggregates, etc., which are ground to meet the specified fineness requirements.
1. Limestone grinding process
There are two main processes for limestone grinding:
Open-circuit process: the process in which the material passes through the mill once and is used as the finished product for the next stage of operation;
Closed-circuit process: the process in which the material is sorted at one or several levels after leaving the mill, and the fine particles are used as the finished product, and the coarse particles are returned to the mill for re-grinding.
The open-circuit process is relatively simple, with the advantages of less equipment, less investment, and easy operation. However, because all materials need to meet the fineness requirements before leaving the mill, over-grinding is prone to occur, and the finely ground materials are prone to form a buffer layer, which hinders the further grinding of coarse materials, greatly reduces the grinding efficiency, and increases power consumption.
Therefore, most limestone powder manufacturers currently choose the closed-circuit process, which can reduce over-grinding, improve mill efficiency, and reduce energy consumption. In addition, the limestone powder produced by the closed-circuit process has uniform particle size and is easy to adjust, which can meet different fineness requirements.
2. Example of closed-circuit production of limestone powder Raymond mill
Process description:
Limestone falls from the hopper at the bottom of the silo to the belt conveyor, and then is sent to the mill for grinding.
Because the grinding roller rolls tightly on the grinding ring under the action of centrifugal force, the material is scooped up by the shovel and sent to the middle of the grinding roller and the grinding ring, and the material is crushed into powder under the action of the grinding pressure.
The powdered material is blown out by the fan and classified by the classifier above the mill.
The classifier is composed of radial radial blade wheels and transmission devices. The blade wheels are driven by the transmission device to rotate at a certain speed, blocking the coarse particles in the air flow and returning them for re-grinding. The fine powder is sent to the cyclone separator with the air flow through the wind screen, so the classifier plays a screening role. The powder particle size can be freely adjusted by adjusting the air volume or changing the blade wheel speed.
The cyclone separator separates qualified products from the air, and the finished products are transported to the finished product warehouse through the bucket elevator through the pipeline, and the air flow returns to the blower through the return air duct for recycling.
The material contains a certain amount of moisture, and a certain amount of water vapor will be generated during grinding. In addition, the entire pipeline is not sealed absolutely tightly, so a certain amount of external gas is sucked into the system, which increases the system's circulating air volume. To ensure that the grinder works under negative pressure, the excess air enters the bag dust collector for purification and then is discharged into the atmosphere.
How to extend the life of vertical mill equipment
In cement production, vertical mill is a key equipment, and the operating status of its roller bearing is crucial to production safety and efficiency.
How to make the vertical mill roller last longer
1. Choose the right lubricant and replace it regularly
The choice of lubricant is crucial. You should choose high-quality lubricants suitable for high temperature and high pressure environments. At the same time, the lubricant needs to be replaced regularly to ensure its stability and cleanliness during use and avoid bearing damage caused by oil quality problems.
2. Strengthen daily maintenance, early detection and early treatment
Operators should regularly check the operating status of the lubrication system, especially in high temperature environments, and pay attention to changes in oil temperature. If the oil temperature is abnormal, the machine should be stopped immediately for inspection and continue to operate after troubleshooting. The wear of the bearings should also be checked regularly, and the problematic parts should be replaced in time to avoid further damage.
3. Regularly check and replace oil seals
Although the oil seal is small, it has a huge effect. The wear of the oil seal should be checked regularly, and the failed oil seal should be replaced in time to ensure that the lubricant does not leak and prevent external impurities from entering the bearing. This simple measure can greatly extend the service life of the bearing.
In addition to bearing problems, the wear resistance of the grinding roller and grinding disc liner is also an important factor affecting the life of the vertical mill. Different materials and manufacturing processes determine the wear resistance of the grinding roller and grinding disc.
1. Traditional casting: low cost, high risk
Traditional casting processes mainly use high manganese steel and high chromium cast iron as materials. The advantages of these materials are low cost, simple process, and suitable for large-scale production.
However, they also have obvious disadvantages. Although high manganese steel has good toughness, its wear resistance is relatively low. The wear resistance of high chromium cast iron has been improved, but its brittleness problem is still prominent, and it is easy to crack during use, which makes it impossible to repair and can only be used once.
2. Micro casting (surface cladding): cost-effective choice
Micro casting, also known as surface cladding technology, is currently the most widely used anti-wear solution. This process is to improve the wear resistance of grinding rollers and grinding discs by cladding a wear-resistant layer on an ordinary cast steel substrate.
3. Ceramic alloy composite casting: the future wear-resistant star
Ceramic alloy composite casting is an emerging wear-resistant technology that embeds ceramic particles into the surface of the cast iron matrix, significantly improving the wear resistance of the grinding roller and grinding disc. This material has extremely high wear resistance and toughness, and is particularly suitable for use under harsh working conditions.
However, the process of ceramic alloy composite casting is complex, the manufacturing cost is high, and there is also the problem of irreparability. It is more suitable for special working conditions with extremely high requirements for wear resistance, rather than ordinary cement production environments.
4. How to choose the most suitable solution?
When selecting the materials for grinding rollers and grinding disc liners, hardness, toughness, cost and repairability should be considered comprehensively according to specific working conditions.
Traditional casting is suitable for those occasions with high cost control requirements and relatively simple working conditions;
Micro casting is suitable for most cement plants. It can provide better wear resistance while reducing maintenance costs;
Ceramic alloy composite casting is suitable for some special working conditions. Although the cost is high, its extremely high wear resistance is worth paying attention to.
Application of Ultrafine Grinding Technology in Food Industry
Ultrafine grinding technology has emerged in recent years with the continuous development of modern chemical industry, electronics, biology, materials and mineral development and other high-tech technologies. It is a high-tech cutting-edge technology for food processing at home and abroad.
In the field of food processing, powders with a particle size below 25μm are usually called ultrafine powders, and the method of preparing ultrafine powders is called ultrafine grinding technology.
The ultrafine grinding technologies commonly used in food mainly include airflow type, high-frequency vibration type, rotating ball (rod) mill type, roller type, etc. Among them, airflow ultrafine grinding technology is more advanced, using the gas through the pressure nozzle to generate violent impact, collision and friction forces to achieve material grinding.
Classification of ultrafine grinding technology in the food industry
Although food ultrafine powder has been around for a short time, it has been used in condiments, beverages, canned foods, frozen foods, baked foods, health foods, etc., and the effect is better.
Application of ultrafine grinding technology in food processing
Soft drink processing
At present, soft drinks developed using airflow micro-grinding technology include powdered tea, bean solid beverages, and calcium-rich beverages prepared with ultrafine bone powder.
Tea culture has a long history in China. Traditional tea drinking is to brew tea with boiling water. The human body does not absorb a large amount of nutrients from tea. Most of the protein, carbohydrates and some minerals and vitamins are retained in the tea residue. If tea is made into tea powder (particle size <5μm) at room temperature and dry state, the absorption rate of its nutrients by the human body can be improved.
Adding tea powder to other foods can also develop new tea products. Plant protein beverages are milky products made from protein-rich plant seeds and fruit cores through soaking, grinding, homogenization and other operations.
Fruit and vegetable processing
Vegetables are ground into micro-paste powder at low temperature, which not only preserves the nutrients, but also makes the fiber taste better due to the micro-refining.
Grain and oil processing
Adding ultrafinely ground wheat bran powder, soybean powder, etc. to flour can make high-fiber or high-protein flour. Rice, wheat and other grains are processed into ultrafine powder. Due to the small particle size, the surface starch is activated, and the food filled or mixed with it has the excellent properties of easy maturation, good flavor and taste.
Soybeans are processed into soy milk powder after ultrafine grinding, which can remove the fishy smell. Beans such as mung beans and red beans can also be made into high-quality bean paste, soy milk and other products after ultrafine grinding.
Aquatic product processing
Spirulina, pearls, turtles, sharks and other cartilage ultrafine powders have unique advantages. For example, the traditional processing of pearl powder is to ball mill for more than ten hours to make the particle size reach several hundred meshes.
Functional food processing
Ultrafine powder can improve the bioavailability of functional substances and reduce the amount of base materials in food. The sustained release of microparticles in the human body can prolong the efficacy. In the process of developing solid honey, ultrafine grinding of ingredients with a colloid mill can increase the fineness of the product.
Processing of spices and condiments
Ultrafine grinding technology, as a new food processing method, can make spices and seasoning products (mainly fermented solid products of beans) processed by traditional processes more high-quality.
The huge porosity of spices and seasonings after micronization creates a collective cavity that can absorb and contain aroma, and the flavor lasts for a long time, and the aroma and taste are more intense.
At the same time, ultrafine grinding technology can make traditional seasonings finely broken into excellent ultrafine particles with uniform particle size and good dispersion performance, and the fluidity, dissolution rate and absorption rate are greatly increased, and the taste effect is also significantly improved.
For products with high sensory requirements, the particle size of spices after ultrafine grinding is extremely fine, up to 300-500 mesh, and the naked eye cannot observe the existence of particles at all, eliminating the generation of black spots in the product and improving the appearance quality of the product. At the same time, the corresponding equipment of ultrafine grinding technology has physical and chemical functions such as coating, emulsification, solid emulsification, and modification, creating a realistic prospect for the development of seasoning products.
What are the applications of titanium dioxide in different coatings?
In recent years, with the rapid development of the coatings industry, people have higher and higher requirements for the performance of titanium dioxide. Not only do they require titanium dioxide to have very good dispersibility, but they also require titanium dioxide to have very good hiding properties. At the same time, they also have very high requirements for the impurity content of titanium dioxide. Under such high requirements, the widely used titanium dioxide has continuously improved its production technology, improved its performance, and expanded its application direction.
Among them, pigment-grade titanium dioxide has a high refractive index and strong tinting power, and has very outstanding advantages in both hiding power and dispersibility. For this reason, pigment-grade titanium dioxide has been widely used in coatings and papermaking. The proportion of pigment-grade titanium dioxide in coatings is the largest, among which rutile titanium dioxide is widely used in industry.
As decorative coatings
The pigment performance of pigment-grade titanium dioxide is very good, and modern people mostly choose white or light colors to decorate houses in house decoration. Therefore, pigment-grade titanium dioxide has been widely welcomed by people in house decoration. Not only that, pigment-grade titanium dioxide is also widely used in external coatings for ships, cars, etc.
As architectural coatings
Pigment-grade titanium dioxide plays a very important role in the production process of coatings, and titanium dioxide is mainly used in architectural coatings.
Make pure white coatings
Most white coatings on the market use a large amount of pigment-grade titanium dioxide in the manufacturing process.
Make colorful pattern coatings
Many pattern coatings on the market now cannot do without pigment-grade titanium dioxide in terms of color ratio or pattern, so pigment-grade titanium dioxide plays a very important role in the production of colorful pattern coatings. Pigment-grade titanium dioxide has also been widely used in automotive exterior paint because pigment-grade titanium dioxide has very good color and high brightness.
Make special functional coatings
Many high-temperature resistant coatings use pigment-grade titanium dioxide in the production process, and high-temperature resistant coatings are a type of special functional coatings, so pigment-grade titanium dioxide is an indispensable raw material in the production of special functional coatings.
Making conductive materials
Titanium dioxide can also be used to make conductive materials. Since the surface of pigment-grade titanium dioxide particles can form a coating, titanium dioxide can also be used in the production of antistatic materials.
Making core-coated titanium dioxide
Pigment-grade titanium dioxide can also be used to make core-coated titanium dioxide, which is also often used in the production of coatings.
Making slurry titanium dioxide
There is also a slurry titanium dioxide in the classification of titanium dioxide. It does not require very complicated processes or very high production costs during the production process. Therefore, slurry titanium dioxide is very popular in people's production and life. Pigment-grade titanium dioxide is indispensable in the production process of slurry titanium dioxide, so pigment-grade titanium dioxide plays a very important role in the process of making slurry titanium dioxide.
UV shielding effect
Nano-grade titanium dioxide is widely used in the production of anti-UV coatings. In many places in people's lives, it is necessary to avoid ultraviolet radiation. Therefore, it is very necessary to use nano-grade titanium dioxide with the function of UV shielding to make anti-UV coatings.
UV absorption effect
Nano-grade titanium dioxide can not only shield ultraviolet rays, but also absorb ultraviolet rays to a certain extent. Therefore, many light-colored coatings use nano-grade titanium dioxide in the production process. In addition, this titanium dioxide can also improve the weather resistance of building exterior walls.
Effect pigments
Rutile nano-grade titanium dioxide is widely used in automotive exterior paint. It can not only effectively cover the poor gloss of the exterior surface of the car, but also present people with more exquisite light effects. In addition, the application of rutile nano-grade titanium dioxide on the automotive topcoat allows people to see different light effects from different angles, thereby meeting people's visual needs.
Whether calcite can produce high-end calcium carbonate depends on these indicators
Calcite is a natural calcium carbonate mineral and the main raw material for producing heavy calcium carbonate. The grade and impurity content of calcite ore are one of the important factors affecting the quality index of heavy calcium carbonate products, and are also the key to determining whether it is food and drug grade calcium carbonate or ordinary filler grade calcium carbonate.
1. CaO content
CaO is the only quality mark of the useful components of the ore. In the requirements of papermaking, coatings, plastics, rubber and food industries, it is expressed by the content of CaCO3 (which can be converted from CaO content).
2. Whiteness
Whiteness is the physical quality mark of the ore, which is related to the color and brightness of the finished product.
3. Hydrochloric acid insolubles
The components of hydrochloric acid insolubles (A.I.R) mainly include free silica (fSiO2), (aluminum) silicates and iron and manganese oxides, which are multi-mineral combination indicators.
4. Magnesium and alkali metal content
MgO is mainly used to evaluate the dolomite content in the ore. In the paper and plastic industries, when the dolomite content is less than 3% (equivalent to MgO≤0.65%), the impact is not significant. In the coating and rubber industries, this requirement can be relaxed to 6% (equivalent to MgO≤1.3%). MgO from talc and serpentine is generally considered to have little impact.
5. SiO2 content
SiO2, various ore tests show that it mainly comes from fSiO2, aluminosilicates and silicate minerals. Among them, silicate minerals are mainly wollastonite, which has a certain difference in hardness from calcite and affects the uniformity of product particle size. Water washing can remove some Si, Al and Fe in calcite and improve the whiteness of the ore.
6. Al2O3 content
Al2O3 mainly comes from aluminosilicate minerals and is one of the main components of hydrochloric acid insolubles. The allowable value should not be greater than the limit value of hydrochloric acid insolubles.
7. Fe2O3 content
Fe2O3 is a coloring component, and its content has an impact on the color of the product. According to the industry's experience, Fe2O3≤0.3% has no significant effect, and Fe2O3≤0.1% has almost no effect. Fe2+ exists in many minerals. If it changes in price during processing or use, its impact needs to be paid attention to.
8. MnO content
MnO in calcite ore mainly comes from manganese oxides, carbonate minerals and silicate minerals. MnO will affect whiteness. There are no requirements for manganese in the current industry standards. In previous indicators, the rubber industry application requires control of its content.
9. Harmful content
Heavy metals, barium, fluorine, arsenic, free alkali, (alkali metal + magnesium), sulfur and other indicators. These indicators need to be evaluated for use as food additives, toothpaste and food packaging paper production, or for rubber products and plastics and coating fillers that have an impact on health.
10. Content of dark foreign matter
The content of dark foreign matter and particle size have a certain impact on whiteness. Under the current conditions, it is recommended to conduct qualitative statistics on the content of dark foreign matter and particles to evaluate whether it is suitable for ultra-fine processing. When the content of dark foreign matter in heavy calcium carbonate for papermaking industry exceeds a certain content, it should be used as an evaluation indicator. Generally, it is required that no more than 5 dark foreign matter particles should be contained in each gram of sample.
11. Yellowness and transparency
The whiteness currently tested, also known as blue light whiteness, is actually the brightness of the material and cannot reflect the color difference of the material well. Therefore, heavy calcium carbonate for papermaking needs to evaluate yellowness and transparency. The papermaking industry hopes that the yellowness is low, the transparency is low, and the coverage is good. Calcite with high whiteness often has good transparency.
What are the advantages of precipitated barium sulfate in the application of coatings?
Precipitated barium sulfate is a reinforcing agent in the coating industry and is very popular among consumers. It can improve the water resistance, heat resistance, wear resistance and impact resistance of coatings. It is a cheap and effective white inorganic light stabilizer that can prevent paint surface aging and can also be used as a reinforcing agent in coatings. Because it has high filling properties and low oil absorption, it significantly reduces the cost of various oil-based coatings, water-based coatings, etc.
Precipitated barium sulfate can also be used to replace titanium dioxide. Compared with titanium dioxide, its hiding power is not reduced, and it increases the whiteness and brightness of the coating. Precipitated barium sulfate is an environmentally friendly material because of its strong chemical polyurethane, good stability, acid and alkali resistance, insoluble in water, ethanol, organic solvents, moderate hardness, high whiteness, high gloss, and absorption of harmful X-rays.
The coating produced by precipitated barium sulfate not only increases the solid content of the coating, but also reduces the amount of solvent used. Even at a higher concentration, it has extremely high gloss. In the production and manufacturing, it not only saves raw materials, but also greatly improves production efficiency and creates corporate profits.
It has the following advantages in coating applications:
1. High cost performance
Precipitated barium sulfate has an extremely high reflectivity in a wide spectrum, so it looks like a white powder and is color neutral. This can maintain the original brightness and hue of the pigment. Most pigments are prone to form agglomerates, which will weaken the coloring power of the pigment. Whether it is water-based color paste, solvent color paste or universal color paste, the use of precipitated barium sulfate will significantly and effectively reduce the flocculation problem in the preparation of various pigments, increase steric hindrance or charge repulsion to stabilize the pigment, and improve its cost-effectiveness. It can also effectively reduce the use of various pigments and play a role in replacing pigments, including titanium dioxide, color pigments and carbon black.
2. Can be used to adjust gloss
Precipitated barium sulfate has excellent dispersibility, so the paint with precipitated barium sulfate has extremely high gloss and rheological properties even at higher concentrations.
3. Can reduce solvent content
Precipitated barium sulfate has low oil absorption, which can effectively increase the solid content of the color paste and reduce the amount of solvent. It has almost no effect on viscosity and reduces VOC.
4. Can shorten the grinding time
The use of precipitated barium sulfate in the preparation of coatings can effectively reduce the flocculation problem in the preparation of various pigments, not only save raw materials, but also effectively shorten the grinding and dispersion time.
5. Very good weather resistance/chemical resistance
Precipitated barium sulfate has strong light reflection ability in the ultraviolet wavelength range, and can cooperate with TiO2 to have good sun resistance and weather resistance.
6. Improve mechanical properties
The coating with added precipitated barium sulfate has better interlayer adhesion and film hardness.
Carbon fiber surface treatment: enhancing composite material performance
Carbon fiber is transformed from organic fiber through a series of heat treatment processes. Its carbon content exceeds 90%. It is an inorganic high-performance fiber and a new material with excellent mechanical properties. Carbon fiber not only inherits the inherent properties of carbon materials, but also combines the flexibility and processability of textile fibers. It is regarded as a new generation of reinforcing fiber and is used in many high-tech fields.
As a reinforcement, although it has a series of excellent performance characteristics, it is also accompanied by some challenges that must be faced. Due to the graphite-like structure, its surface is chemically inert, and it is difficult to infiltrate the resin and react chemically. It is difficult for the surface to combine with the resin, which in turn affects the strength of the composite material. Therefore, it is necessary to treat the surface of the carbon fiber, remove impurities on the surface of the carbon fiber, etch grooves on the surface of the carbon fiber or form micropores to increase the surface area, change the surface properties of the carbon fiber, increase the polar functional groups and surface activation on the surface of the carbon fiber, and then it is easier to infiltrate and react chemically, so that the interface of the composite material is more tightly connected and the strength is increased.
There are many methods for carbon fiber surface treatment, mainly including gas phase oxidation, liquid phase oxidation, electrochemical oxidation, coupling agent coating treatment, plasma treatment, grafting modification technology, etc. Among them, gas phase oxidation is currently the most commonly used method, and electrochemical oxidation is currently the only technology that can be operated online continuously during carbon fiber preparation, and the overall performance of carbon fiber reinforced resin-based composites treated with electrochemical oxidation is improved.
(1) Gas phase oxidation method
Gas phase oxidation methods include air oxidation, ozone oxidation, etc.
Air oxidation method is a method of placing carbon fiber in air with a certain relative humidity for high temperature treatment to oxidize the surface of carbon fiber by high temperature. After oxidation, the non-carbon elements on the surface of carbon fiber increase, which is beneficial to improve the wettability of the fiber and the resin bonding.
(2) Liquid phase oxidation method
Liquid phase oxidation method is to use concentrated nitric acid, concentrated sulfuric acid, hydrogen peroxide and other oxidants to contact carbon fiber for a long time to form carboxyl, hydroxyl and other groups on the fiber surface to enhance the bonding with the resin.
(3) Electrochemical oxidation method
Electrochemical oxidation is a method of treating the surface of carbon fiber by using the conductive properties of carbon fiber as the anode and graphite, copper plate or nickel plate as the cathode under the action of a DC electric field and using different acid, alkali and salt solutions as the electrolyte. The effect of surface electrochemical oxidation treatment is a composite process of layer-by-layer oxidation etching and functional group changes.
(4) Coupling agent coating treatment method
The coupling agent has a double functional group in its chemical structure, which enables it to react chemically with the fiber surface and the resin. Some of the functional groups can form chemical bonds with the fiber surface, while the other functional groups can react chemically with the resin. Through such chemical mediating action, the coupling agent can tightly connect the resin and the fiber surface, thereby enhancing the overall performance of the material. By using a coupling agent, not only can the strength and durability of the material be improved, but also its adhesion and resistance to chemical corrosion can be increased.
(5) Plasma treatment method
Plasma technology mainly uses discharge, high-frequency electromagnetic vibration, shock wave and high-energy radiation to generate plasma under inert gas or oxygen-containing gas conditions to treat the surface of the material.
(6) Grafting modification technology
By grafting the hexagonal nano-pyramids of silicon carbide, the interfacial adhesion between carbon fiber and resin can be significantly enhanced, which not only enhances the mechanical properties of carbon fiber composite materials, but also improves their friction performance. This technology has been applied to the manufacture of brake discs.
By selecting a suitable surface treatment method, the surface properties of carbon fiber can be improved, and its bonding with the matrix material can be enhanced, thereby improving the overall performance of the composite material.
Diamond Micro Powder Development Trend
Diamond, commonly known as "diamond drill", is a mineral composed of carbon. It is an allotrope of graphite with a chemical formula of C. It is also the original form of common diamond. Diamond is the hardest substance naturally existing in nature.
Classification of Diamond Micropowder
Diamond micropowder refers to diamond single crystals that are crushed, shaped, purified, and graded to form micron and submicron diamond powder. According to the source of raw materials, it can be divided into natural diamond micropowder and artificial diamond micropowder.
Classification of Diamond Micropowder
Single crystal diamond micropowder is produced by artificial diamond single crystal abrasives, which are crushed and shaped, and produced by special process methods of superhard materials.
The structure of polycrystalline diamond is composed of numerous tiny nano-scale particles bonded by unsaturated bonds, which is very similar to natural black diamond (natural polycrystalline diamond with black or dark gray as the main color).
The role of different types of diamond powder
Traditional diamond powder can be divided into two categories, polycrystalline diamond powder and single crystal diamond powder. With the development of nanotechnology, nano diamond powder has been used and paid more and more attention by people.
Polycrystalline diamond powder
Polycrystalline diamond powder is made from graphite using a unique directional blasting method. The shock wave of the directional blasting of high-explosive explosives accelerates the flying metal flakes and hits the graphite flakes, causing the graphite to be converted into polycrystalline diamond. Polycrystalline diamond powder is characterized by brittleness. Its particle shape is irregular quasi-circular block, and the surface is rough and uneven.
Function: Mainly used in chip optical crystal/ultra-fine processing, large silicon wafer ultra-fine polishing, surface modification and other fields. The spherical polycrystalline diamond powder has a gray-black appearance and a slightly metallic luster.
Single crystal diamond powder
Single crystal diamond powder is produced by static pressure method artificial diamond single crystal abrasive, which is crushed and shaped by special process methods of superhard materials. Its particles retain the single crystal characteristics of single crystal diamond, and its crystal shape is a regular and complete hexahedron, with high strength, toughness and good thermal stability, and strong impact resistance.
Function: Suitable for the manufacture of electroplating products, grinding wheels, grinding wheels, and for polishing, engraving, automotive glass, high-end furniture, ceramics, cemented carbide, magnetic materials, etc. of high-grade stone. It is an ideal raw material for grinding and polishing high-hardness materials such as cemented carbide, ceramics, gemstones, optical glass, etc.
Nanodiamond powder
When the grain size is less than 100nm, it is called nanodiamond. It not only has the excellent properties of diamond, but also has the unique properties of nanomaterials such as small size effect, surface effect, quantum effect, etc. Therefore, it has the dual characteristics of nanomaterials and diamonds and has a wider range of uses.
Function:
(1) Application of fine grinding and polishing. Nanodiamond has the characteristics of both superhard materials and nanomaterials. It can be used in the polishing production of precision parts and for ultra-fine processing of quartz, optical glass, semiconductors, alloys and metal surfaces. The surface roughness value Ra can reach 2-8nm.
(2) Application in the medical field. Nanodiamond can be used as a biological carrier in medical research, and can also be used in wear-resistant coatings on the surfaces of artificial bones and artificial joints to extend the service life of artificial bones and joints.
(3) Application of high thermal conductivity packaging materials. The composite material prepared by adding nanodiamond to a metal high thermal conductivity matrix is expected to become a new type of electronic packaging material with both low thermal expansion coefficient and high thermal conductivity.
Diamond micro powder has a wide range of uses, such as cutting tools, diamond wires, grinding pastes/abrasive fluids, etc. Different application scenarios have different requirements for diamond micro powder, and specialized development is conducive to the development of diamond micro powder. Undoubtedly, diamond micro powder is an indispensable abrasive for the development of products towards high, precise and cutting-edge, and its application prospects are broad and its application fields are also expanding.
In addition to burning cement, what other high-end applications does limestone have?
Limestone is the main raw material for cement production. About 1.4 to 1.5 tons of limestone are consumed to produce 1 ton of cement clinker.
So, in addition to producing cement, what other high-end applications does limestone have?
1. Production of calcium oxide
Calcium oxide is obtained by high-temperature calcination of limestone, commonly known as quicklime, white powder. According to the product appearance, calcium oxide can be divided into block calcium oxide and powdered calcium oxide; according to the different calcium and magnesium content, calcium oxide can be divided into industrial-grade calcium oxide, food-grade calcium oxide, etc. Industrial-grade calcium oxide is divided into four categories: Class I products are for chemical synthesis; Class II products are for calcium carbide; Class III products are for plastics and rubber; Class IV products are for flue gas desulfurization and other uses.
Calcium oxide is an important auxiliary material and basic raw material for steel and plastics. It has huge market prospects in environmental protection fields such as industrial wastewater treatment, garbage incineration, and flue gas desulfurization. As a cost-effective alkaline oxide, calcium oxide is also widely used in highways, high-speed railways, construction, industry (non-ferrous metals, papermaking, sugar making, soda ash, food, medicine, building materials), agriculture and other fields, and is an important basic raw material.
2. Production of calcium hydroxide
Calcium hydroxide is formed by the digestion of calcium oxide and water. Its chemical formula is Ca(OH)2, commonly known as slaked lime and hydrated lime. Its aqueous solution is called clear lime water.
Calcium hydroxide has the general properties of an alkali and is a strong alkali. Since the solubility of calcium hydroxide is much smaller than that of sodium hydroxide and potassium hydroxide, the corrosiveness and alkalinity of its solution are relatively small, so it can be used as an acidity regulator in food to play a role in buffering, neutralization, and solidification. Food-grade calcium hydroxide has a relatively high activity, a relatively loose structure, high purity, good whiteness, low impurity content, and does not contain harmful elements such as Pb and As.
Calcium hydroxide is widely used as a raw material in the calcium preparation production industry, among which calcium gluconate is common. Calcium hydroxide can be used as an acidity regulator in milk powder (including sweetened milk powder) and cream milk powder and its prepared products, and infant formula. Calcium hydroxide can be used as a buffer, neutralizer, and solidifier in beer, cheese, and cocoa products. Due to its pH adjustment and coagulation effects, it can also be used for the synthesis of medicines and food additives, the synthesis of high-tech biomaterials HA, the synthesis of VC phosphates for feed additives, and the synthesis of calcium cyclohexane, calcium lactate, calcium citrate, sugar industry additives and water treatment and other high-end organic chemicals. It is helpful for the preparation of acidity regulators and calcium sources such as edible meat semi-finished products, konjac products, beverage products, and medical enemas.
3. Production of nano calcium carbonate
Nano calcium carbonate refers to functional inorganic fillers with a particle size of 1-100nm, which are widely used in rubber, plastics, papermaking, inks, coatings, sealants and adhesives, medicines, toothpastes, food and other fields.
The industrial production of nano calcium carbonate is mainly based on carbonization. Its raw materials are mainly limestone with a high calcium carbonate content. The powder material products are obtained by calcination, digestion, carbonization, modification, dispersion, and drying.
According to the gradient change of CaO content in limestone, high-quality limestone with a content greater than 54% can be used to produce high-value-added light calcium carbonate and nano calcium carbonate products, which are mainly used in high-end plastics, papermaking, coatings, medicine, electronics, food and other industries; intermediate-quality limestone with a content between 49% and 53% can be used to produce active calcium oxide and calcium hydroxide digested from it, which are mainly used in metallurgical solvents, chemicals and food deep processing industries; low-quality limestone with a content less than 48% can be used in the cement industry and the construction industry.
According to the different calcium oxide content of limestone resources, the limestone raw materials are distributed to various related industries in a tiered manner, so as to achieve a fully closed industrial chain with high-quality resources, full utilization, and maximum value and environmental effects.
Development of graphene-modified thermosetting resins
Graphene is a honeycomb two-dimensional planar material composed of a single layer of carbon atoms connected in an sp2 hybrid manner. It has many excellent properties, such as high carrier mobility, high light transmittance, high specific surface area, high Young's modulus, high fracture strength, etc. These properties make graphene an ideal filler for improving the performance of thermosetting resins. Thermosetting resin materials have attracted widespread attention from industry and academia due to their advantages such as high specific strength, large specific modulus, good thermal stability and corrosion resistance.
There are two main ways to modify the surface of graphene powder: covalent bond modification and non-covalent bond modification.
Covalent bond modification is a method that uses chemical reactions to achieve covalent bonding of modifiers on the graphene surface, or special treatment of graphene to form new functional groups or chemical bonds, thereby improving the compatibility and dispersibility of graphene powder in the resin matrix.
Non-covalent bond modification mainly combines the modified group with graphene through π-π bond stacking to achieve effective modification of graphene. The advantage of this method is that it improves the dispersibility of graphene without changing the chemical structure of graphene or introducing new covalent bonds.
For different types of thermosetting resin matrices, it is necessary to select a suitable modification method so that the graphene powder can be evenly dispersed in the resin without affecting the performance of the resin matrix.
As a new type of reinforcing filler, graphene can be evenly dispersed in the thermosetting resin matrix to significantly improve the mechanical properties, ablation resistance, electrical properties, corrosion resistance and wear resistance of the composite material, thereby expanding the application range of thermosetting resin-based composite materials.
Mechanical properties
Graphene can significantly improve the mechanical properties of thermosetting resin materials, making composite materials have important application value in the fields of machinery and automotive structural parts.
Anti-ablation performance
The addition of graphene oxide will improve the thermal conductivity of the composite material and accelerate the heat extraction, reducing the linear ablation rate of the composite material by 62.08%. The addition of graphene oxide is conducive to inducing the formation of a carbon layer in the matrix during the ablation process, enhancing the degree of graphitization of the matrix, and forming a heat insulation layer to prevent heat from expanding into the material, thereby reducing the linear ablation rate of the composite material and improving the ablation resistance of the resin composite material.
Electrical properties
Graphene is a carbon material with a two-dimensional honeycomb lattice structure composed of sp2 hybridized carbon atoms. The excellent structural π electrons provide a conjugated effect, which greatly improves the mobility of electrons. At the same time, under ideal conditions, the conduction band and valence band of graphene are in contact at the Dirac point, so that electrons can move between the valence band and the conduction band without energy hindrance, thereby promoting graphene to have excellent electrical properties.
Corrosion resistance
Thermosetting resin is a common matrix material in coating materials and has excellent corrosion resistance, but the cured resin material will produce micropores or microgaps, which weakens the protection ability of the substrate. The chemical stability and barrier properties of graphene itself can effectively prevent the penetration of corrosive agents and prevent further diffusion of corrosive agents in the surface when they reach the metal surface, minimizing the degree of corrosion damage to the protective substrate, making it the preferred filler for metal substrate coatings.
Application of graphene-modified thermosetting resin
At present, graphene-modified thermosetting resin is mainly used in heavy-duty anti-corrosion coatings, sprayed on large equipment (such as large ships, surface platforms, wind turbines, etc.) to prevent corrosion and extend service life; in the future, graphene-modified thermosetting resin will also be more widely used in aerospace, electronic components and other fields.