Calcined kaolin has high whiteness, soft quality, easy dispersion suspended in water, good plasticity, high adhesion, excellent electrical insulation performance; It has good acid resistance solubility, low cation exchange capacity, good fire resistance and other physical and chemical properties. Therefore, calcined kaolin has become a necessary mineral raw material for dozens of industries such as papermaking, rubber, chemical, coating, medicine and national defense. There are two main areas, one is the filler used in the paper making process, and the other is the pigment used in the surface coating process.

      In recent years, with the rapid development of modern science and technology, the application of calcined kaolin is more extensive. At present, the total output of calcined kaolin in the world is about 40 million tons, of which refined soil is about 23.5 million tons. Paper industry is the largest consumer of refined kaolin, accounting for about 60% of the total consumption of kaolin. According to Temanex Consulting In Canada, the total global production of paper and board in 2000 was about 319 million tons, and the total amount of calcined kaolin used in paper coating was about 13.6 million tons. For general culture paper, the amount of filler is 10-20% of the paper weight. For coated paper and paperboard (mainly including light coated paper, coated paper and coated paperboard), in addition to the need for filler, also need pigment, fill, pigment with calcined kaolin accounted for 20-35% of the weight of the paper. Calcined kaolin used in papermaking, can give paper good covering performance and good coating gloss performance, but also increase the whiteness of paper, opacity, smoothness and printing suitability, greatly improve the quality of paper.

Distribution of calcined kaolin

      At present, there are more than 700 kaolin deposits in China, and the proven reserves of 200 deposits are 3 billion tons, which are relatively scattered. Among them, 1.67 billion tons of coal measures kaolin is mainly distributed in the carboniferous Permian coal measures in northeast and northwest China, and exists in the form of gangue, roof and floor in coal seams or individual ore beds.

     "Kaleidoscope" of calcined Kaolin Mining Technology

     Small scale multi-purpose hand pick or pneumatic pick mining in calcined kaolin open-pit mining mine, narrow gauge railway is used for working face transportation, due to the low side of the mine car, it can be manually loaded, and the stripping is still carried out by drilling and blasting.

      Large mines are directly mined with excavators, and then loaded into dump trucks and sent to concentrator.

      Hard rock stripping with rock drilling blasting method, ammonium nitrate explosive blasting, and then loaded with excavator dump truck transported to the dump site. The stripping of topsoil, useful excavator backhoe digging and loading also useful bulldozer first set heap, and then with excavator loading.

      Sand can be used in the soft ore with high sand content and easy to disintegrate in water by water mining and water transportation

      In view of the local no freezing period, water resources and rich, are using water to collect water. Ore through the water gun mining, ore pulp through the ore ditch to the slurry pool. The slurry pool is arranged in the middle of the ore block, one ore block one.

      Slurry is transported to roughing plant through plastic pipe with diameter of 250mm by ballast slurry pump.

      Technical performance of water gun. Mining water is also used more in Britain

      The main advantages of calcined kaolin: simple mining process, simple equipment, high labor productivity, pulping process of concentrator in advance, integration of mining and selection. The stripping of the upper cover is dry stripping dry transport.

      Underground mining, according to the characteristics of soft and thick ore body, has been using layered caving method for many years, each layer from the plate to the floor, from the boundary of mining area or ore block boundary to the drawing patio layout of the way back mining, mining time of each layer is 3 to 4 months, so as to reduce the amount of roadway maintenance. After the delamination mining, consider the formation of the regenerated roof, to stop mining for 1 to 2 months before the next delamination.

       Mining without blasting method but with pneumatic pick and hand pick, foreign useful along the way automatic forward scraper mining machine for mining. There is pure nitrogen in marble of mine floor, and it will be ejected from the crack when driving in the courtyard. Therefore, diluting nitrogen should be considered in the calculation of air volume, preventive measures should be taken, air composition of working face should be determined quickly, automatic alarm device should be set, and mixed ventilation mode with good effect should be selected.

     As for the caving problem, there are some particularities compared with those mines which generally adopt the layering caving method.

     Generally, in mines with stratified caving method, surface pits are formed and rainwater and surface water are accumulated. The stoping working face is waterlogged, and pit and water are formed on the surface of the mine. However, the regeneration top caused by residual minerals after stoping can play a role of water expansion, and there is little water on the stoping working face. But sometimes ore drawing make regeneration top loose, uneven subsidence, will make the upper water was muddy out, this kind of accident occurs frequently. Therefore, comprehensive waterproof measures must be taken for the surface collapse pit, and caving and roof caving problems must be paid attention to.

Product requirements Requirements for raw materials

      In recent years, manufacturers are making calcined kaolin suitable for coating industry. The main functions of calcined kaolin in paint are filler and color substitute. Adding a certain amount of filler in the coating can improve the filling, grinding and mechanical strength of the coating kaolin in the paint industry is mainly to replace the white pigment, especially titanium dioxide.

      Different size and type of calcined kaolin used in different types of paint: coarse kaolin used in need dark glossy or matt paint, fine kaolin is used to produce high gloss paint, or used in the manufacture of emulsion paint, can make the coating has good opacity, anti-corrosion and subsidence prevention, improve the coating hardness, improve the quality of coating. The original production of kaolin is simply through air drying and flotation, but now it has been replaced by water washing, strict particle size control, calcination and surface treatment, thus improving the grade of products.

      In these reforms, calcination is the most important process, so the scale is very large. Calcined kaolin, besides has the general characteristics of kaolin have also has irregular shape, has excellent optical performance, high oil absorption rate and pigment volume concentration, not easy to aging, wear resistance and easy emulsification, in water or oil medium has the advantages of high covering power, widely used in paint coatings industry coatings add after calcined kaolin, can block ultraviolet light, Improve the coating weather resistance, delay powdering discoloration, enhance the comprehensive mechanical properties of the coating and pollution resistance, self-cleaning, acid, alkali, high temperature resistance, improve the coating heat resistance and anti-corrosion properties.

      Paint coating is the largest consumption area of calcined kaolin in China, accounting for about 65%~85% of the total consumption. In the interior and exterior wall coating, anti-corrosion coating, powder coating, heat-resistant coating, insulation coating, landmark coating, waterproof coating, anti-radiation coating and other special functional coatings, a large number of high-quality calcination of whiteness more than 90, particle size more than 1250 mesh.

      The supply of quality products cannot meet the market demand. This also shows that the market of calcined kaolin products still has great growth potential. The calcined kaolin used in coatings needs high whiteness, low viscosity and fine particle size, but the domestic products are rough and cannot meet the quality requirements. As for kaolin industry, it also faces the same problem as many domestic industries, that is, "big but not strong". Kaolin industry also needs to constantly upgrade itself to meet the increasing market demand, in order to withstand the tests from the market in many ways.