Preface. Quartz sand is a quartz particle made of quartz stone by crushing, which is a non-metallic mineral, a hard, wear-resistant, chemically stable silicate mineral, and its main mineral component is silicon dioxide (SiO2). The color of quartz sand is milky white, or colorless translucent, with a hardness of 7 on the Mohs scale. Quartz sand is an important industrial mineral raw material, with unique physical and chemical properties, making it occupy a pivotal position in aviation, aerospace, electronics, machinery and today's rapidly developing IT industry, widely used in glass, casting, ceramics and fireproof materials, smelting ferrosilicon, metallurgical flux, metallurgy, construction, chemical, plastics, rubber, abrasives, filter materials and other industries. This paper intends to briefly introduce the industrial chain with quartz sand as raw material.
1. Definition and classification of quartz sand
Quartz is a hard, wear-resistant, chemically stable silicate mineral, quartz sand is a quartz ore made of quartz ore through crushing, screening, pickling, washing, calcination and other processes. In China, quartz sand is generally subdivided by the different contents of silica and ferric oxide, which are mainly divided into ordinary quartz sand, refined quartz sand and high-purity quartz sand.
Ordinary quartz sand: silica content 90 99%, ferric oxide content 006～0.02%, mainly used in the manufacture of ordinary glass, casting and refractory materials.
Refined quartz sand: silica content 99 995%, ferric oxide content 0005%, mainly used in optics, instrument glass, etc.;
High purity quartz sand: silica content 99 999%, ferric oxide content 0001%, mainly used in photovoltaic crucibles, insulating materials for electronic components, large integrated circuit packaging, opaque quartz glass, advanced optical glass, potassium silicate, etc.
The common specifications of quartz sand are divided into 05～1mm、1～2mm、2～4mm、4～8mm、8～16mm、16～32mm；According to the number of sieve meshes, there are: 10 20 mesh, 20 40 mesh, 40 80 mesh, 100 120 mesh.
2. Overview of China's quartz sand industry chain
The quartz industry chain can be subdivided into quartz raw materials, quartz sand, quartz materials, quartz products and other links. The upstream raw materials include vein stone, quartz stone, quartz sandstone, quartz placer, argillaceous quartz placer, feldspar quartz placer, and other siliceous raw materials, with strong resource attributes. The quartz sand prepared by purification is convenient for deep processing and easy to distinguish quality, and is the main circulation link of quartz products, with bulk commodity attributes.
China's quartz sand market is clearly differentiated, and the market for ordinary quartz sand and refined quartz sand is basically mature, and the production and marketing are relatively stable. Because the downstream involves many fields such as casting, building materials, and chemical industry, and the raw materials and process barriers are low, the production and sales volume is huge and stable. High-purity quartz sand is an important strategic resource, strict requirements for ore quality and purification process, at present, China only realizes the stable supply of quartz sand below 4n grade, high-end products rely on imports, production and marketing and ** fluctuations are obvious.
3. Overview of the distribution of quartz minerals in China
China is rich in quartz ore resources, including quartzite (53%), quartz sandstone (14%), natural quartz sand (32%), vein quartz (1%), etc.
Quartzite deposits in China are mostly distributed in Qinghai, Anhui, Liaoning, Shaanxi and other places, and the more representative quartzite deposits in the country are Xiaopingdingshan Deposit in Benxi City, Liaoning Province, and Laoqingshan Deposit in Fengyang County, Anhui Province; Quartz sandstone deposits are mostly distributed in Sichuan, Hunan, Jiangsu, Zhejiang, Yunnan and Shandong, and the more representative quartz sandstone mines in China are the Qitai quartz sandstone deposit in Kunming, Yunnan Province, and the Sunzu quartz sandstone deposit in Yinan County, Shandong Province; Natural quartz sand is mainly distributed in the southern part of Fujian, Guangdong, Guangxi, the northwest of Hainan and the northern part of Shandong, as well as the middle reaches of the Yellow River and Poyang Lake. Vein quartz minerals account for 63% in East China, 15% in Northeast China, and relatively few in other regions.
There are few sources of high-quality low-iron quartz sand that are easy to mine in China, mainly distributed in Guangdong, Guangxi, Anhui, Hainan and other places.
4. The main use of quartz sand
1) Glass industry.
The glass industry is a large user of quartz raw materials, and modern float glass generally requires the SiO2 content in the quartz raw materials to be above 96, the Al2O3 content to be below 2, and the Fe2O3 to be 001％～0.1 with a granularity of 0It is about 4mm, and the particle size is 05mm or more and 0Particles below 1mm should not exceed 5. High-grade glass, such as special glass, high-quality flat glass and precision optical glass, etc., has stricter requirements for the chemical composition of quartz raw materials, the content of SiO2 should be above 99, and the content of Fe2O3 should be less than 005％～0.1. The content of Al2O3 and TiO2 is required to be 05～2.0 and 005 below.
2) Mechanical casting industry.
In the mechanical casting industry, quartz raw materials are widely used as molding sand, casting mold core and casting mold, etc., the amount of quartz sand in the foundry industry is relatively large, the general production of 1 ton of castings requires 1 ton of molding sand and clay, and the quartz sand used in the mechanical casting industry accounts for about 33% of the world's total output. With the improvement of the precision degree of casting, there are higher requirements for the purity of quartz raw materials, such as the content of SiO2 in the quartz sand required by the more advanced resin sand process in casting is higher than 97%, and the particle size should be between 40 and 320 mesh.
3) Ceramic industry.
Quartz is also the main form of vitreous in ceramic glazes, which gives ceramic glazes a series of good physical and chemical properties (such as strength, gloss, wear resistance, hardness and chemical attack resistance, etc.), and increasing the SiO2 content in the glaze can also improve the melting temperature and viscosity of the glaze.
Fused silica ceramics are sintered bodies made of fused silica or quartz glass as raw materials, crushed raw materials, then graded by raw materials, ball milled pulping, grouting or injection molding, and finally made by firing process. Fused silica ceramics have many excellent properties such as small thermal expansion coefficient, good thermal shock stability, good electrical insulation performance, acid and alkali erosion resistance, etc., and have been rapidly promoted and applied in countries around the world since their inception.
4) Refractory industry.
The main use of quartz raw materials in the refractory industry is to produce siliceous refractory bricks, including silica bricks, lightweight silica bricks and fused silica products. In order to ensure that the refractory degree of siliceous refractory is higher than 1650 1700, the load softening temperature is higher than 1650, and has the characteristics of good thermal stability, good chemical stability, small thermal expansion coefficient and high mechanical properties, the content of SiO2 in quartz raw materials is generally required to be more than 93%, and the coarse particles should be limited to less than 2mm for quartz raw materials with poor crystallization state.
5) Chemical industry.
The application of quartz sand in the chemical industry is generally common in products such as water glass, silica gel and bubble alkali. As a detergent and carton adhesive, the liquid soaking alkali requires a content of SiO2 to be higher than 98%, and the content of Fe2O3 is less than 02%, the granularity requirement is 02 2mm, while as a petroleum refining catalyst solid bubble alkali is more stringent, the content of SiO2 is higher than 99%, and the content of Fe2O3 is less than 003%。
6) Water purification materials.
Quartz sand is a water purification material widely used in various water supply treatment, sewage treatment and environmental treatment. In recent years, researchers have put forward the idea of modifying ordinary quartz sand filter media, by attaching substances with different functions on the surface of quartz sand to improve the properties of the surface of the filter material, and make a modified filter material with excellent adsorption performance and certain mechanical strength. In view of China's current economic level, this technology will have a broad application prospect in water supply treatment.
7) Photovoltaic ultra-clear glass.
As a new material, ultra-clear glass has broad application prospects in the solar photovoltaic industry, high-end cars, high-end buildings, high-end horticultural buildings and high-end furniture with its high light transmittance and crystal clear characteristics. During the "14th Five-Year Plan" period, according to the national strategic plan of "carbon peak and carbon neutrality", the photovoltaic industry will attract explosive development, and the demand for low-iron quartz sand used in photovoltaic ultra-clear glass, its basic material, is expected to grow rapidly at a rate of more than 30% per year.
8) Artificial quartz stone slabs.
Artificial quartz stone is a composite material made by curing and molding by 93% 95% quartz and about 7% unsaturated polyester resin binder, pigment, curing initiator and other auxiliary reagents, which is hard in texture, dense in structure, rich in color, wear-resistant, pressure-resistant, high-temperature resistant, corrosion-resistant, anti-penetration, widely used in the market, and is the fastest growing variety in artificial stone.
9) Quartz crucible.
Quartz crucible belongs to the subdivision of quartz glass products, which has clean, homogeneous, high temperature resistance and other properties. At present, it is widely used in the production process of refining crystalline silicon in the field of solar energy and semiconductors, and is a consumable in the production process of crystalline silicon.
10) Optical fiber.
Optical fiber, referred to as optical fiber, is a cylindrical optical waveguide used for long-distance transmission of light energy or optical signals, and the mainstream of communication optical fiber is quartz optical fiber. As the "source" of optical fiber and cable production, domestic researchers use natural quartz sand as raw material and use plasma solid external deposition method (PSOD) to prepare large-size quartz casing for single-mode optical fiber preforms, which have the characteristics of one-time molding, low hydroxyl content, less impurity content, large size (compared with multi-mode casing) and good vitrification procedures, which can meet the needs of single-mode fiber preform preparation.
11) Fiberglass.
Glass fiber is an inorganic non-metallic material with excellent performance, with a wide range of advantages, such as good insulation, strong heat resistance, good corrosion resistance, and high mechanical strength. Glass fiber is made of quartz sand, pyrophyllite, kaolin, limestone and other ores as raw materials by high-temperature melting, drawing, drying, winding and other processes, its monofilament diameter is a few microns to more than 20 microns, equivalent to 1 20-1 5 of a hair, each bundle of fiber precursor is composed of hundreds or even thousands of monofilaments. Glass fiber is usually used as a reinforcing material, electrical insulating material and thermal insulation material in composite materials, circuit substrates and other fields of the national economy, and is a new material industry that the state focuses on encouraging the development of.
12) Quartz fiber.
Quartz fiber is a high-performance inorganic fiber, which is prepared from high-purity silica or natural quartz crystals. It retains some of the properties and characteristics of solid quartz, is a good high-temperature resistant material, and can be used as a reinforcement for advanced composite materials. Quartz fibers are of high purity (99.).9%), which makes it have some good characteristics, such as strong ablation resistance, good temperature resistance, low thermal conductivity, high chemical stability, and excellent dielectric properties.
13) Petroleum fracturing proppant.
Fracturing is an important technical means to stabilize and increase production in oil and gas fields, especially for the development of low permeability and ultra-deep oil and gas reservoirs. Among them, fracturing proppant is the core technology product for oil and gas fracturing exploitation. It is a key material used to support artificial fractures in oil and gas reservoir transformation, and is the key to improve the success rate and transformation effect of fracturing.
Proppant is a natural sand or artificial high-strength ceramic solid particle with a certain particle size and strength, a certain spherical degree and gradation. Since the successful application of hydraulic fracturing technology in the world's first oil and gas field, proppant has been developed for decades. At present, there are three main proppants used in industry: natural quartz sand, artificial ceramsite, and coated proppant.
14) Calcium silicate board.
Calcium silicate board is an inorganic building board with high strength and stable performance made of siliceous materials, calcareous materials and reinforced fibers as the main raw materials, through slurry molding, slab compaction and autoclaving curing. It has superior characteristics such as fire prevention (up to A1 standard), thermal insulation, anti-corrosion and moth-proof, waterproof and moisture-proof, sound insulation and sound absorption, light weight and high strength, green and harmless, and is more energy-saving and environmentally friendly, earthquake-resistant and impact-resistant than traditional plates, and can be widely used in the fields of interior and exterior wall insulation and decoration of housing buildings, ceilings and cabin partitions, billboards, etc., and the design and installation are plastic, time-saving and labor-saving.
Quartz sand is one of the most important raw materials in calcium silicate products, accounting for 40% of the quality of calcium silicate board raw materials, the purity of SiO2 in quartz sand has a great influence on the formation of tobmullite crystals in the process of hydration reaction, and quartz powder that does not participate in the chemical reaction is also used as aggregate in cement cement. In order to reduce the energy consumption of quartz sand wet grinding and use more industrial waste, quartz sand with SiO2 content higher than 90% is preferred in the production of calcium silicate board, and a certain amount of fly ash can be appropriately mixed to reduce production costs.
15) Industrial fillers.
As an industrial filler, quartz sand is another important application field and has received widespread attention. It is mainly used in organic polymer materials, such as plastics and their plastic films, rubbers, coatings, paints and binders, etc., to improve their physical and chemical properties or improve the properties of a certain aspect, such as adding quartz sand to improve the compressive and tensile strength of plastics. Generally, the requirements for the quality of quartz sand are relatively high, the content of SiO2 is more than 99%, and the content of Fe2O3 is 005 below. Sometimes the requirements for the quality of quartz sand can meet the requirements of high-purity quartz.
5. Distribution and development status of high-purity quartz ore resources in China
High-purity quartz is a kind of mineral product purified by crystal, vein quartz, granite pegmatite and other ores as raw materials, which is widely used in strategic emerging industries such as information technology, high-end manufacturing, and new energy. Deposits that can be purified to produce high-purity quartz are called high-purity quartz raw material ores.
China's high-purity quartz raw material ore is dominated by vein quartz and crystal, with a total resource of 6.85 million tons, of which the crystal resource is only 0690,000 tons. China's high-purity quartz raw material deposits are mainly distributed in Qichun, Hubei Province (Lingqiu Mountain Quartz Mine (SiO2 content is 9935), Jiangsu Donghai (SiO2 content is 9919), Anhui Jingde (Banshu Township Longchuan vein quartz ore SiO2 content of 9901) and Taihu Lake and other areas, among which the crystal quality of Jiangsu Donghai is the most superior, but the retained resources are close to exhaustion. In addition, it is also distributed in Fengyang, Anhui, Xinyi, Jiangsu, and Altay, Xinjiang.
6. An important criterion for judging high-purity quartz raw materials
Using natural quartz minerals as raw materials is the main way to obtain high-purity quartz, which is an important non-metallic mineral material widely used in high-tech fields. China is rich in quartz resources, but high-purity quartz raw materials are scarce. High-purity quartz feedstock can only be formed under geological conditions that meet a range of specific chemical and physical parameters. At present, only a few quartz deposits are suitable for processing into high-purity quartz, and the treatment process is extremely complex.
At present, there is no unified standard definition of high-purity quartz in China. Foreign scholars mainly classify high-purity quartz according to the content of harmful elements in quartz. Some scholars in China only classify high-purity quartz based on the purity of SiO2. Some scholars classify high-purity quartz based on the purity of SiO2 and the upper limit of harmful impurity element content. In general, most scholars believe that it is one-sided to judge the quality of quartz based on chemical composition alone, and various factors should be considered comprehensively in evaluating quartz. As far as quartz minerals are concerned, in addition to the chemical composition, the selectivity of impurities determined by the occurrence state of impurity elements, quartz embedding characteristics, the number and size of inclusions, and lattice impurities in natural quartz is an important criterion for judging high-purity quartz raw materials.
7. High-purity quartz sand production process
At present, the mainstream high-purity quartz sand is a kind of stone made of natural crystal stone, silica and quartzite, which has been carefully selected and finely processed, which can be used to make various glasses, as water treatment filter materials, or as blanks and shaft materials for ceramics and refractory porcelain. The production process of high-purity quartz sand is beneficiation, crushing, screening, cleaning, grinding, impurity removal, drying and packaging.
1) Beneficiation. High-purity quartz sand is generally made of silica, quartzite or natural crystal stone, and the raw materials are manually crushed and sorted and sorted out and put into the silo.
2) Crushing. Generally, jaw crusher, impact crusher and sand making machine are used for crushing operations, and the quartzite is continuously and uniformly fed into the jaw crusher by the vibrating feeder for coarse crushing, and the quartzite after coarse crushing is sent to the sand making machine with a belt conveyor for fine crushing.
The jaw crusher is mainly used for the coarse crushing of quartzite, the impact crusher is used for the fine crushing link, and the sand making machine gives full play to the role of fine crushing and shaping in the production process of high-purity quartz sand, which is the most ideal high-purity quartz sand crushing equipment.
3) Sieving. The qualified sand and gravel are screened out with a circular vibrating screen, the quartz sand with a particle size of less than 1mm is sent to the sand washing machine to clean off the stone powder and dust, and the quartz sand above 6mm is re-fed into the crushing system, which is re-crushed by the impact crusher or sand making machine, and the screening cleaning system and the crushing system together form a tight and ingenious closed-circuit cycle.
4) Cleaning. Put the sand and gravel that has passed the acceptance into the cleaning pool in accordance with the process standards and remove the contamination with clean water to wash away the impurities attached to the surface of the ore. Operators must wear clean, protective water boots when cleaning.
5) Grinding. Quartz sand grinding powder is used for mineral processing and impurity removal to produce high-purity quartz powder.
6) Removal of impurities. Re-election.
The use of a shaker with appropriate water flow re-separation can effectively reduce mica content.
Magnetic separation. Using the magnetic differences of various ores or materials, the strong magnetic substances of iron contained in quartz sand can also be removed by distinguishing under the action of magnetic force.
Flotation. According to the different physical and chemical properties of the surface of mineral particles, the main function of flotation is to remove mica, feldspar and iron-containing mineral impurities in quartz sand.
Acid leaching. A mixture of HCL and HF is used to soak for 6 days, mainly to remove acid-soluble metal oxides and some silicate minerals. Acid leaching is one of the important processes in the purification process of high-purity quartz sand, whether it is to prepare quartz glass for electric light source, or for the preparation of quartz raw materials for photovoltaic and semiconductor devices, the acid leaching process must be used.
7) Washing. After acid leaching, there is a residue of soluble impurities that adhere to the dissolved quartz sand, which needs to be removed by washing method. The minerals after acid leaching are washed to diffuse the impurities and residual liquid on the surface of the quartz to the liquid phase, and then the washing is completed.
8) Drying acceptance.
The quartz sand is dried and dehydrated, and the packaging is accepted.
8. Market challenges and opportunities for high-purity quartz sand
With the national "carbon neutrality", "14th Five-Year Plan" and "China's 2050 photovoltaic development outlook" and other policies, the photovoltaic industry is increasingly highlighting its national strategic position, at present, the photovoltaic industry belongs to the new energy industry that needs to be subsidized by the national finance, the country's macro control policies and measures on photovoltaic installed capacity, subsidy scale, and subsidy intensity will directly affect the production and operation of companies in the industry. With the improvement of relevant national financial assistance policies and the continuous promotion of other support policies in the industry, the photovoltaic and its accessories industry will develop in the direction of a more complete industrial chain and higher quality products, and this development is bound to drive the development of photovoltaic glass and high-purity quartz sand industry in the upstream of the photovoltaic industry chain.
At present, the high-purity quartz sand market is highly competitive. Enterprises compete fiercely in technological innovation, product quality and market share. As a high-purity quartz sand refining and production enterprise, it is facing both challenges and development opportunities, and needs to pay attention to the following issues:
Raw materials: The raw materials of high-purity quartz sand are relatively tight, and fluctuations may have a certain impact on the market. By optimizing the procurement strategy, we have established long-term cooperative relations with mineral suppliers to ensure the stability of raw materials.
Technological innovation: Continuously invest resources in technology research and development, and launch more competitive products to meet market demand.
Environmental protection requirements: With the improvement of environmental awareness, high-purity quartz sand production enterprises need to pay attention to environmental protection regulations and strengthen environmental protection measures.
Optimize the industrial chain: Enterprises can optimize the industrial chain, improve production efficiency, reduce production costs, and improve the competitiveness of enterprises by integrating upstream and downstream resources.
Expand the market: Enterprises can actively expand domestic and foreign markets, look for new market opportunities, expand sales channels, and increase market share.
Strengthen cooperation: Enterprises can strengthen cooperation with universities and scientific research institutions to jointly carry out technology research and development and improve the technical strength of enterprises.
Pay attention to policies: Enterprises need to pay close attention to relevant national policies, actively respond to the call of the country, participate in the formulation of industry standards, and promote the healthy development of the industry.
Talent training: Enterprises should pay attention to talent training, improve the technical level and comprehensive quality of employees, and provide talent guarantee for the development of enterprises.
Looking forward to the future, the market prospect of high-purity quartz sand is still broad. With the development of downstream industries and technological advancement, the market demand will continue to grow.
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The 2nd Anhui International Quartz Industry Conference and Exhibition 2024.