I. Current status of non-metallic mineral powder industry in China

Non-payment on the general concept is a mineral powder product, it should be said a long time ago, for example, siliceous limestone to produce raw materials in civil engineering with quicklime and hydrated lime fired glass products used in sand and gravel. However, non-metallic mineral fine powders and functional non-metallic mineral materials have been developed with the modern scientific and technological revolution, industrial development, social progress, the improvement of human quality of life and the general awareness of environmental awareness. China's large-scale production and industrial applications in this field began in the late 1970s or early 1980s. After nearly 20 years of development, especially since the 1990s, China's non-metallic mineral processing industry has formed a considerable scale. In terms of ordinary or bulk products, it can not only basically meet the needs of the domestic market, but also a large number of exports, occupying a more important position in the international non-metallic mineral products market.

According to the incomplete statistics of China Non-Metallic Mining Industry Association and related professional associations, in 2002, China's glass quartz powder and quartz sand, heavy calcium carbonate, kaolin , talc , graphite , fluorite , gypsum , wollastonite , mica , The total output of non-metallic mineral powders such as bentonite , diatomaceous earth , asbestos and smectite powder has reached more than 35 million tons (see Table 1). In addition, in 2002, China produced 22 billion m2 of building ceramics and 60 million pieces of sanitary ceramics. Based on this, it is estimated that the annual consumption of non-metallic mineral powders such as china clay, feldspar and quartz is more than 10 million tons. According to the statistics of China Lime Association, China's lime production reached 13.2 million tons in 2002, mainly used in steel mills, sintering plants, light calcium carbonate, calcium carbide, soda ash production in the chemical industry, building materials, construction, high-grade roads and wastewater. Treatment and flue gas desulfurization, etc. Based on the above incomplete statistical analysis, the total output of non-metallic mineral powders in China reached more than 180 million tons in 2002, and the processing capacity has reached more than 200 million tons. The processing capacity and output of ultrafine powders have exceeded 1.2 million tons.

It should be noted that China's non-metallic mineral powder industry, although large in scale, plays an indispensable role in the country's economic construction. However, its scientific and technological content and product grade are still not high, and there are still some non-metals in China. Mineral powders, especially non-metallic mineral deep-processing products related to the development of modern high-tech and new materials, rely on imports, such as graphite, bentonite, mica, kyanite , kaolin, etc., imports of these mineral deep-processed products in 2002 They increased by 67.55%, 33.45%, 44.92%, 114.8% and 14.92% respectively compared with the previous year. In 2002, the import volume of high-quality kaolin in China reached 10,000, with an average price of 218.91 US dollars per t. In particular, China is currently the world's graphite production.

And the country with the largest export volume, such a high import growth rate indicates that China's graphite deep processing or products can not meet the needs of the domestic market. In addition, high-grade quartz glass raw materials and spherical silicon micropowders for large-scale integrated circuit packaging are basically dependent on imports.

In addition, due to the large number of non-metallic minerals, the layout of the powder processing industry is scattered, and the number of enterprises is large, but the degree of intensification is low.

Second, China's non-metallic mineral powder processing technology status

Powder processing techniques such as pulverization, classification, purification, modification, solid-liquid separation, calcination, granulation, packaging, etc. are widely used in the processing of non-metallic minerals. The variety of minerals, wide application fields and complex technical requirements are one of the main characteristics of non-metallic mineral processing. Due to this feature, the processing technology of non-metallic minerals is also very different. Some non-metallic minerals can be directly pulverized into commodities. For example, some calcites must be purified. For example, some applications in graphite only require simple pulverization of non-metallic minerals, such as limestone powder for feed, bentonite for casting, and ordinary Non-metallic mineral fillers require deeper processing in some applications, such as colloidal graphite for high-tech industrial applications, high-purity quartz, kaolin for paper industry, heavy calcium carbonate pigments, organic bentonite for coatings, and nanocomposites. Used montmorillonite, a graphite intercalation compound for new conductive materials. The following is a brief review of several major powder processing steps.

(1) Concentration and purification

Due to the characteristics and application characteristics of non-metallic mineral mineralization, most non-metallic minerals in the industry, such as limestone, calcite, marble, dolomite, gypsum, barite , talc, pyrophyllite , chlorite, bentonite, Yili , wollastonite, kaolin coal-based hard rock, quartzite glass material only simple sorting and classification of pulverization and classification, and modifying the activation processing. At present, non-metallic minerals in the industry for beneficiation and purification mainly include asbestos, graphite, soft kaolin, diatomaceous earth, high-purity quartz, mica, garnet , kyanite, sillimanite, frog stone, magnesite , and long , rutile, wrong sand and fluorite, apatite, potassium and so on.

Asbestos mainly adopts air-selection and sieving. The graded graphite has good natural floatability. It mainly uses flotation. For high-purity graphite with fixed carbon content of 95 or higher, it adopts chemical beneficiation, strong acid, alkali treatment and high temperature forging soft kaolin. Hydrodynamic cyclone and centrifugal graded sand removal, strong magnetic or high gradient magnetic separator and chemical bleaching reduction and oxidative bleaching, iron removal and whitening diatomite are mainly used by scrubbing and dispersing, grading and removing crystalline silica, and selectively separating and separating clay. Pure quartz mainly uses acid leaching and pure water to wash mica. It is mainly based on manual or mechanical picking and friction dressing, as well as air separation and re-election. The garnet is mainly used in the shaker to separate the sillimanite and kyanite. the primary flotation feldspar mainly based on magnetic separation, separation with silica, vermiculite primary flotation using primary difference in density after expansion thereof gangue minerals simple winnowing magnesite ore is selected from water and mainly Hot-selection, that is, after temperature-controlled calcination, the separation of rutile and smear is mainly carried out by electrification, magnetic separation and re-election of comprehensive force field beneficiation process. Fluorite is mainly used for flotation of flotation phosphate rock.

(two) crushing classification

At present, the pulverization of non-metallic mineral powders is roughly classified according to the particle size of the product: crushing (product size 35-1 mm), grinding or milling (product size 1000-10 μm) and ultrafine pulverization or ultrafine grinding (product Particle size 10-0.1 μm) 3 levels. Each level can also be subdivided into several different working segments. For example, crushing can be divided into coarse crushing and fine crushing grinding. It can be divided into coarse grinding (20-200) mesh and fine grinding (≥325) mesh. The main equipment used in each of the different comminution and grading levels is listed in Table 2.

In recent years, China's non-metallic mineral powder processing equipment has developed rapidly. There are more than 70 manufacturers of ultra-fine pulverization and fine grading equipment , which can produce airflow mills, mechanical impact mills, agitating ball mills , vibrating ball mills, and rotating cylinders. Ball mill, continuous planetary ball mill, tower mill, rotary mill, graded self-grinding mill , high-pressure jet mill and other ultra-fine pulverization and various dry and wet fine grading equipment.

(3) Surface modification

Non-metallic mineral fillers and pigments used in non-metallic mineral fillers, paint coatings, coating materials, etc., used in polymer materials such as plastics, rubber, adhesives, or polymer-based composite materials, and adsorption-catalyzed non-metallic mineral materials. Surface treatment or surface modification to improve its application properties. Surface modification methods mainly include surface chemical coating, precipitation reaction coating, intercalation modification, etc. Surface modifiers include organic and inorganic materials. The modification process includes dry and wet modification equipment. There are continuous powder surface modification machines, batch heating mixers, vortex mills, stirred reaction tanks and reactors. Table 3 shows the commonly used modifiers and modification equipment for the surface modification of non-metallic mineral powders.

(4) Others

Processing of non-metallic mineral powders also includes dewatering filtration and drying, calcination, granulation and packaging.

At present, the filtration equipment used in the industry mainly includes filter presses, centrifuges, vacuum filters and other drying equipment, mainly spray dryers, cylinder dryers, flash dryers, multi-function dryers, fluidized bed dryers, tunnels. Dryer, etc. Drying technology and equipment for drying and deagglomerating of powder agglomeration problems in ultra-fine powder drying process, such as multi-functional strong dryer, flash dryer, etc., have also been in ultra-fine heavy calcium carbonate, ultra-fine kaolin It has been successfully applied in the processing of ultra-fine brucite, etc. The filter-filter dewatering equipment and the horizontal spiral centrifugal dewatering equipment have been widely used in the processing of clay minerals such as ultra-fine kaolin, bentonite and attapulgite, domestic spray and extrusion. Other granulation equipment and particle shaping equipment have also been applied in industry. In addition, in recent years, packaging equipment for non-metallic mineral ultrafine powders has developed rapidly. China has been able to manufacture vacuum packaging machines for automatic metering and gas-solid separation, continuous packaging and other automated continuous packaging equipment.

In addition, the flame-flow rotary kiln used for coal-based kaolin satin burning has been successfully developed and applied in new plants in the past three years. Now, in addition to fuel and gas flame-type rotary kiln, China can also manufacture The electric heating rotary kiln with independent intellectual property rights basically solves the problem of localization of key equipment for coal-based calcined kaolin.

However, there are still some shortcomings in China's current non-metallic mineral processing technology. The main problems are small production lines (less large equipment), low automatic control and regulation levels, unstable product quality, high energy consumption and wear per unit of product, and environmental pollution. Although there are many equipment manufacturers, most of them are small in scale, and the process supporting technology is poor. There are no large-scale enterprises that can participate in international competition, such as equipment manufacturing, process design and engineering construction. In addition, some aspects, such as lime, modernization The proportion of calcining kiln is very small, most of which are earth kiln with high energy consumption and unstable quality (under-burning or over-burning). Since the production of lime in China has reached an annual output of hundreds of millions of tons, the waste of energy and The pollution of the environment is great, but few people pay attention and actively solve it.

In addition, the product standards can not meet the needs of related industries, especially the development of high-tech industries. This is one of the main reasons for China's current low-cost export of certain non-metallic mineral products on the one hand, and high-priced imports of similar non-metallic mineral processing products. .

Third, the development trend of non-metallic mineral powder processing technology

The wide application of non-metallic mineral powders in modern high-tech new materials is premised on their unique functions. Therefore, functionalization is the development direction of non-metallic mineral powders and the goal pursued by powder processing technology.

The main factors affecting the functionality of non-metallic mineral powders are structure, purity or chemical composition, particle size and shape, physicochemical properties of the surface or interface.

For non-metallic minerals, purity refers in many cases to its mineral composition, while non-chemical composition is the structure of minerals that determine minerals. There are many non-metallic minerals with similar chemical composition, but the mineral composition and structure are far apart, so their function or application performance is very different. For example, quartz and diatomite, although the chemical composition is silica, the former It is a crystalline structure of silicon oxytetrahedrons, which are amorphous structures with complex structures, and therefore their application properties or functions are very different. The influence of mineral composition, chemical composition and structure on the function of non-metallic mineral materials is also related to the purity of minerals. In many cases, in order to fully illuminate the function of non-metallic mineral materials, mineral raw materials must be beneficiated and purified, especially when there are many impurities in the mineral raw materials, and such impurities have an adverse effect on a major function of the non-metallic mineral materials. . Therefore, the beneficiation and purification technology is very necessary for the function of non-metallic mineral powder. In the 21st century, both the emerging high-tech and new materials industries, environmental protection industries and traditional industries will place higher demands on the purity of non-metallic mineral powder materials. With the improvement of the purity requirements of non-metallic mineral powder materials, the difficulty of selecting purification technology will also increase. In addition, the depletion of resources, the improvement of comprehensive utilization of resources and the increasing environmental protection requirements will also increase the selection and purification technology. Difficulty. Therefore, fine-grain beneficiation and purification technology, comprehensive utilization technology or no tailings processing technology will become the main development trend of future non-metallic mineral purification technology, including non-metallic minerals including graphite, quartz, kaolin, mica, talc, Diatomaceous earth, wrong sand, wollastonite, barite, rutile, bentonite, fluorite, sillimanite, andalusite , kyanite, tourmaline, etc.

The particle size and particle size distribution of mineral raw materials and particle shape have a great influence on the performance or function of non-metallic mineral materials. The function of many non-metallic mineral powders, such as reinforcement or reinforcement in polymer matrix composites. Properties, strength and toughness of ceramic materials, hiding rate as paper and paint pigments, coloring power, and electrical, magnetic, optical, absorbing and shielding of powders, catalysis, adsorption, rheology, antibacterial, decolorization, bonding It is related to its particle size, particle size distribution and particle shape. The function of most non-metallic minerals depends on particle size, distribution and grain shape. The ultrafine powder has excellent physical and chemical properties such as large specific surface area, high surface activity, fast chemical reaction speed, low sintering temperature, high strength of sintered body, good filling and reinforcing performance, and high hiding rate. Therefore, many fields of application require that the fine-grained micron or sub-micron portion of the non-metallic mineral raw material requires not only ultrafine particle size but also a narrow particle size distribution. For example, high-grade paper coating requires the fineness of heavy calcium carbonate to be -2μm ≥ 90%, and the particle size distribution requires a maximum particle size of 5 ≤ μm, -0.2μm ≤ 10 to 15%. For example, the degradation of plastic requires the fineness of heavy calcium carbonate. -6～7μm≥97%, the maximum particle size is required to be ≤8μm; the functional fiber filler requires the inorganic non-metallic filler to have a fineness of 97%≤2μm, the maximum particle size ≤3μm; the high polymer matrix composite uses magnesium hydroxide and hydroxide Aluminum flame retardant fillers require a median diameter d≤10μm, 97%≤5μm. In terms of grain shape, the mica powder used to prepare pearl mica has a diameter-thickness ratio of 80 or more. It is used as a silica fume for engineering plastics (such as auto parts). Stone filler, in addition to the particle size of less than 5μm, the aspect ratio is greater than 10. In the 21st century, the demand for ultra-fine, narrow-distributed powders of various non-metallic minerals will continue to increase. Therefore, ultra-fine pulverization, fine grading and particle size control technology as well as special granular (such as sheet, needle, spherical, etc.) powder processing technology will be one of the key development directions of non-metallic mineral processing technology.

Many of the functions of non-metallic mineral powders depend on surface or interfacial properties. Such as adsorption, catalysis, electrical, optical, rheological, dispersion and compatibility with other components in the material. The surface properties of minerals are related to the composition, chemical composition and structure of the minerals, as well as to processing techniques. Many application fields have special requirements on the surface or interface properties of non-metallic mineral powders, such as polymer-based composite materials, rubber, adhesives, multi-phase composite ceramic materials, paint coatings, biomedical materials, chemical fiber, etc. Metal mineral powder surface or interface with organic or inorganic binder polymer, ceramic billet, oil paint, water-based paint, chemical fiber, etc. and bio-matrix have good compatibility. Petrochemical industrial zeolite and kaolin catalyst or carrier It has a specific pore size distribution and a high specific surface area. It has a certain calcium ion adsorption capacity for molecular sieves. Activated clay bentonite for refining decolorization and diatomaceous earth for beer filtration have strong surface adsorption capacity for water treatment. The ability of diatomite to selectively adsorb organic, inorganic, and heavy metal ions. Although the development of powder surface modification technology is late, it can improve or improve the compatibility of non-metallic mineral powder with filler or composite base, improve modern high polymer inorganic composite materials, multi-phase composite ceramic materials, The development of high-grade or special paint coatings, functional fibers, adsorption and catalytic materials is of great significance. Therefore, powder surface and interface modification technology will become one of the most important development directions of non-metallic mineral powder processing technology.

Since the reform and opening up, although China's non-metal industry has made great progress and processing technology has made great progress, it still faces many challenges. Although China's non-metallic mineral deep processing industry has made great development, some so-called deep-processing products can't find the market. It is very difficult for enterprises to operate. We export a large number of non-metallic mineral products to foreign countries every year. Some minerals export to the world. First, domestic related companies still need to import deep-processed products. Some deep-processed products are even sold back after processing raw materials or primary processed products exported from China. In addition to China's corporate economic strength, marketing and technical development capabilities are not strong, one of the most important reasons is that China's non-metallic mining industry often pays more attention to the development of resources and neglects the development and upgrading of product functions. When some of our enterprises develop resources and projects, they often do not pay attention to carefully study the market, how to meet market requirements from product functions, and adapt to the needs of related industry development. How to mine and enhance the function and application performance of products through application research, how to Pay attention to protecting the ecological environment during the processing. The development of modern high-tech and new materials is premised on higher technological content, lower environmental load and more adaptable to the needs of social development. Non-metallic mineral powders and materials are no exception. Only non-metallic mineral powders or deep-processed products that have clear functions or outstanding functions and can meet the technical progress and industrial development requirements and environmental protection requirements of relevant application fields can win a stable market. Therefore, the future development trend of non-metallic mineral powder materials will be cross-distribution, fusion mineralogy, powder processing, materials science and related fields of different fields, collaborative research, continuous exploration and upgrading of non-metallic mineral powder products and applications Performance, promote technological advancement and industrial development in related application areas.

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