Illite clay is characterized by illite minerals. Illite, also known as muscovite, is colloidal dispersed muscovite. Illite is a kind of silicate mica clay mineral rich in potassium, named after it was first discovered on Erie Island in the United States. Its chemical formula is:
k 1-x(H2O)x { Al2[als i3 o 10](OH)2-x(H2O)x }
Illite is usually scaly, white, non-expansive, plastic, with a particle size of less than 4μm and clay-like. Besides illite, illite clay usually contains quartz, muscovite, sericite, chlorite, pyrite, limonite, kaolinite and rutile.
Illite is the intermediate product of mica weathering into clay minerals. Common in weathered clay, such as mica schist and gneiss. It is also common in the soil formed by weathering of intermediate-acid igneous rocks.
China's illite clay mines are mainly produced in Ouhai, Hua Kai, Chun 'an, Zhejiang, Tianshui, Gansu, Xihe and Pingdingshan, Henan. Among them, a detailed geological exploration was carried out in the Duchuantou illite deposit in Ouhai County, Zhejiang Province. The illite mine in the suburb of Pingdingshan, Henan Province has proved a C-level reserve of 20 million tons. The roof of the deposit is Quaternary eluvial caprock with a thickness of 1 ~ 10m, and the thickness of the ore body is 20 ~ 30m.
Second, the main uses and industrial requirements of illite clay ore
1. Main uses
Illite has good adsorption, fineness, brittleness and whiteness, and is suitable for ceramics, plastics, paper making, fertilizer and other industries.
Ceramic industry: used to make glazed tiles, mosaics, hollow bricks and so on.
Plastic industry: as a filler, it has enhanced performance;
Paper industry: used as filler and coating.
In addition, it can also be used as fertilizer raw material, and can be made into potassium-calcium fertilizer, potassium-nitrogen fertilizer, potassium-nitrogen compound fertilizer and so on after treatment.
2. Industrial requirements
The general requirements for illite clay in industry are: low hardness and high whiteness; The higher the content (wB/%) of Al2O3, K2O and H2O in chemical composition, the better, Fe2O3+TiO2 < 0.8%, Al2O3 > 26%, K2O > 4% and SiO2 < 54%; Whiteness > 84%.
See table 3- 12- 1 for export quality standards.
Table 3- 12- 1 China building materials and equipment import and export company illite clay export quality standard
Geological work requirements can refer to the requirements of kaolin mine.
Thirdly, the whitening treatment of illite clay.
Illite clay has similar properties to kaolin and talc, and is mainly used in plastic, paper, rubber, cosmetics, coatings and other industrial fields. The whiteness of illite clay is a key index affecting its industrial utilization. There are few illite clay minerals with high whiteness and high quality produced in nature, and most illite clay minerals can only be used as low-grade raw materials because of their high impurities and low whiteness. The main impurity minerals that affect the whiteness of illite clay minerals are titanium minerals (anatase and rutile) and iron minerals (limonite and pyrite, etc.). ), chlorite, dark time, feldspar, etc. And inorganic and organic carbon. Therefore, the treatment process to improve the whiteness of illite clay includes purification process. The main methods to improve the whiteness of illite clay are as follows:
1. Baking method
Illite clay minerals often contain aphanitic inorganic carbon or organic carbon, which can be volatilized after roasting. Lv Xianjun et al. conducted a roasting whitening test on illite ore in eastern Zhejiang. The particle size of the ore is -2mm, and after roasting at 900℃ for 0.5h, the whiteness reaches 96.2%. After 90% of the raw ore was ground from -2mm to -200 mesh, the whiteness after roasting decreased from 96.2% to 87.5%. The reason is that Fe2+ is transformed into Fe3+ at high temperature, and anatase is transformed into rutile, and this transformation is more and more obvious with the fineness of raw ore.
Acid leaching before roasting can obviously reduce the iron content, and the effect of improving whiteness is better than direct roasting.
2. Mineral processing and purification
Illite clay ore generally adopts grinding and classification purification process, and magnetic separation is added when necessary. Graded gravity separation and purification is mainly to separate gangue minerals with coarse particle size and high hardness, if timely.
Zhang Lingyan et al. conducted an experimental study on gravity separation, purification and whitening of Yingshi illite ore in Wenzhou, Zhejiang Province. The technological route of mineral processing and purification is: coarse grinding → superfine grinding → hydraulic classification → high gradient magnetic separation. Finally, illite concentrate with whiteness of 83.3% and -2μm particle content of 80.4% was obtained. During the research, it is found that iron and titanium minerals are mainly concentrated in the coarse-grained fraction, that is, the crushing and ultrafine crushing effects of illite ore have great influence on its subsequent operations. Semi-industrial test was carried out with CM-300 high-speed impact pulverizer. Spindle speed of pulverizer is 2400 r/min; The particle size of the classifier is-10μm and the rotating speed is 1300 rpm. The test results are shown in Table 3- 12-2 and Table 3- 12-3.
Table 3- 12-2 crushing test results of high-speed impact crusher (%)
Table 3- 12-3 Analysis Results of Fine Particles of High-speed Impact Crusher
As can be seen from the above two tables, the selective crushing effect is good. The fine and coarse products were observed under a microscope and analyzed by X-ray diffraction. The mineral rich in fine particles is flaky illite. Coarse-grained minerals are mainly timely, pyrite, rutile and anatase. The content of Fe2O3 in coarse particles is 7 times higher than that in fine particles, and the content of TiO2 is 5 times higher. After crushing, 50% ~ 70% of iron and titanium impurity minerals are removed.
The ultrafine grinding effect is good, the average particle size of the product is 1.7 1μ m, and the content of-10μ m reaches 98.8%, which provides a good technical index for further classification with hydrocyclone and high gradient magnetic separation.
For fine-grained illite clay ore embedded with iron and titanium minerals, the effect of iron removal by wet high gradient high intensity magnetic separator is not good. Panjiafen used magnetic agglomeration separation process to treat inferior illite clay ore, and achieved good results. The magnetic seed is natural magnetite powder, the field strength of wet high gradient magnetic separator is 1.4 ~ 1.5t, and the pH value of pulp is 5.5 ~ 6.6. The iron removal rate reaches 53%, and the whiteness can be improved to 79%.
Fourthly, the application of illite clay ore.
Preparation of 1. potassium nitrogen fertilizer
Tianjin Research and Design Institute of Chemical Industry of Ministry of Chemical Industry cooperated with other units to develop the process route of chemical processing and comprehensive utilization of illite. Products include activated silicon powder, aluminum sulfate, potassium nitrogen fertilizer, activated alumina and so on. And in 1995, 165438+ 10, a set of 5,000 t /a industrial plant was built, achieving sales income of14.95 million yuan /a and net profit of 2,442,500 yuan/a, with remarkable social and economic benefits.
See table 3- 12-4 for the chemical composition of illite powder.
Table 3- 12-4 Chemical Composition of Illite Ore
The process flow is shown in Figure 3- 12- 1.
Figure 3- 12- 1 illite chemical processing process flow chart
Product quality: nitrogen and potassium fertilizer, K2O > 1 1%, nitrogen content >14%; Potassium alum, food grade; Industrial grade aluminum sulfate; Active silicon powder, reaching the enterprise standard of active silicon powder formulated by 1997; Amorphous aluminum hydroxide, purity > 99.5%, specific surface area ≥ 200m2/g.
Because illite leaching is carried out in high temperature, high pressure and acidic environment, it is necessary to choose appropriate equipment materials to solve the corrosion problem.
Enriching potassium oxide, improving the quality of aluminum hydroxide and increasing the total nutrients of nitrogen and potassium fertilizers, especially the content of potassium oxide, are the keys to the comprehensive utilization of illite. The crystallization of potassium alum can be ensured by controlling the concentration, temperature and residual acid content of acid leaching solution.
2. Coatings for paper industry
The coating test with illite in Changchun Paper Mill showed that all the indexes met the industrial requirements, among which smoothness, glossiness and xylene adsorption exceeded the national standards, with excellent quality and good adsorption to red, blue and black inks. Requirements of raw materials for coating illite: purity > 98%, particle size < 2 microns > 95%.
3. Used as reinforcing filler in plastic industry.
Guo, Qian Dingfu and others have studied the development and utilization of illite clay ore in Pingdingshan suburb, which is mainly used as plastic reinforcing filler. The mineral composition (wt%) of the raw ore is illite 74, timely 17, feldspar 4, limonite (containing a small amount of goethite) 3, chlorite 1, siderite 1, and minor and trace minerals are rutile, biotite and titanium dioxide.
The technological process is as follows: illite ore → crushing → pulping → screening → hydrocyclone classification → precipitation and concentration → drying → air separation and crushing → product L (packaging and warehousing) → modification and activation → product 2 (packaging and warehousing).
Surface modification steps: firstly, illite powder (sample number 1) and stearic acid are mixed according to the ratio of 100: 1.8, put into a sealed stirrer, and stir at 80℃ for 10 minute, and then100:. The modified illite powder produced by this process is No.2 illite powder.
See Table 3- 1# illite powder and 2# illite powder for the comparison of clay, light calcium carbonate, superfine activated light calcium carbonate and white carbon black (filler is 50 points) in rubber.
Table 3- 12-5 Comparison of rubber properties of various fillers
As can be seen from Table 3- 12-4, the reinforcement effect of 2# illite powder is equivalent to that of superfine activated light calcium carbonate and silica.
Light calcium carbonate is replaced by 1# illite powder, and the performance of 300m HPVC thin-walled pipe (type11.8) for low-pressure irrigation is shown in Table 3- 12-6.
Table 3- 12-6 Performance Comparison of Illite Powder and Light Calcium Filled Products
1000kg rubber compound was prepared with 1# illite powder (instead of superfine activated light calcium carbonate) and 10 # illite powder (instead of semi-reinforced industrial carbon black), respectively. The extrusion performance of inner tube and calendering performance of inner cord fabric were good. See table 3- 12-7 and table 3 for the performance test results. The implementation standards are GB 7036-89 and GB 2977-89.
Table 3- 12-7 1 # Properties of Inner Tube Produced by Illite Powder
Table 3-12-8 tire performance produced by 2 # illite powder
Henan Pingdingshan Plastic Additives Factory has built a production line with an annual output of 5,000 tons for wet processing illite powder. This product is mainly used as plastic reinforcing filler to replace clay, light calcium carbonate, superfine active light calcium carbonate and carbon black. The produced PY series plastic reinforcing agent can replace N500, N600 and N700 series carbon black.
The rubber filler developed by the Institute of Physical Chemistry of Materials of Huaqiao University in Fujian can completely or partially replace white carbon black by using local illite resources, as shown in Table 3- 12-9.
Table 3- 12-9 Comparison of mechanical properties between modified illite micropowder for vulcanized rubber and silica
Note: Because 57 phr of white carbon black is the best filling amount in plastic ingredients, it is the basis of comparison.
Using superfine modified illite powder instead of white carbon black in rubber products greatly reduces the production cost of rubber products and has high economic benefits.
Main references
[1] Editorial Committee of Handbook of Nonmetallic Mining, Handbook of Nonmetallic Mining (Volume I), Metallurgical Industry Press, 1992.438+02.
Wang pu et al., Systematic Mineralogy (Zhong Juan), Geological Publishing House, 1984.8.
[3] Lv Xianjun et al., Experimental Study on Whitening of Illite Ore in East Zhejiang, Non-metallic Ore, 1997.2, pp. 33-35.
[4] Pan Jiafen et al., Preliminary study on the development and utilization of inferior illite in Anqiu, Shandong Province, nonmetallic minerals, 1997.5, p. 64.
[5] Pan Jiafen, Study on Iron Removal Technology of Inferior Illite by Magnetic Seed Method, Mineral Protection and Utilization, 1998.3. P. 16~ 17 .
Zhang Lingyan, et al., Experimental study on selective ultrafine grinding of timely illite, mineral protection and utilization, 1997.2, pp. 23 ~ 26.
[7] Guo et al., Preliminary study on the development and application of illite powder in plastic products, nonmetallic minerals, 1996.438+0, pp. 43-45.
[8] Ji Qinghai, application research of illite in Pingdingshan rubber, mineral protection and utilization, 1999.3, pp. 25-27.
Zhao Ji 'an, Present situation and prospect of illite research and development in China, inorganic salt industry, 1999.4, P. 17 ~ 19.