Kyanite minerals are a group of anhydrous aluminosilicate minerals, including kyanite, sillimanite and andalusite. They are all isomorphic variants, and the chemical formula is Al _ 2 SiO _ 5, Al _ 2O _ 3 62.92% and SiO _ 2 37.08%. The name of this mineral family is not uniform among countries. The former Soviet Union called kyanite mineral, Australia called sillimanite mineral and France called andalusite mineral. In the application field of nonmetallic minerals and refractories, especially in refractories, kyanite, andalusite and sillimanite are called the three major minerals for convenience in China.

These three kinds of stones belong to metamorphic minerals. Andalusite often occurs in shallow metamorphic strata and is formed by aluminum-rich argillaceous or argillaceous sedimentary metamorphism. Kyanite is produced by deep regional metamorphism of argillaceous sedimentary rocks, and the temperature and pressure are high when it is formed. Sillimanite generally occurs in moderately metamorphic strata. Because the geological functions of these three minerals are different, the mineral properties are also different. Table 3-4- 1 lists the characteristics of the three minerals.

Stone minerals can be irreversibly transformed into mullite and silica at high temperature, accompanied by volume expansion and other characteristics, and are important expansion agents in amorphous refractories. Adding Shi San (additive) into bauxite-based raw materials increases the mullite content, forms a good mullite network and improves the microstructure of the materials. Therefore, Shisan has become an important refractory raw material.

Table 3-4- 1 Properties of Kyanite Group Minerals

Two. Overview of Shisan mineral resources

1. World Shisan mineral resources

The mineral reserves of Shisan in the world (excluding China) are * * * 380 million tons, including kyanite108 million tons, andalusite175 million tons and sillimanite 97 million tons (see table 3-4-2, table 3-4-3 and table 3-4-4.

Table 3-4-2 Determination of Andalusite Resources in Countries and Regions of the World

Table 3-4-3 Identification of Sillimanite Resources in Countries and Regions of the World

Table 3-4-4 World Kyanite Resources

As can be seen from the three tables listed above, South Africa, the United States, France, India, Brazil, the former Soviet Union and other countries are the three major stone resource countries and three major stone producer countries in the world. Among them, South Africa is the most important andalusite producer and exporter in the world. South African andalusite deposits are concentrated in grotte Mariku, Sabazia and Lidanboji areas in transvaal province. Among them, Tempore Mine in Sabazia is the largest andalusite mine in the world, and the quality of andalusite is good. Andalusite concentrate contains 359.5% Al2O3 and Fe2O3+TiO2≤ 1.3%. It is divided into three size fractions: 0.5 ~ 4 mm, 0. 1 ~ 1 mm and < 0. 147 mm, with an annual output of 6.5438+10,000 ~ 6.5438+200,000 t. The South African andalusite concentrate is mainly exported to Italy, Germany and Britain.

The United States is the second largest producer of minerals in the world, and its main product is kyanite. The concentrate produced by Virginia Kyanite Mining Company contains Al2O31.8% and Fe2O3 < 0.6%. It is divided into four parts: < < 0.295mm, < < 0.147mm, < < 0.074mm and < 0.043mm. The annual output of kyanite concentrate is about 90,000 tons, and its main sales markets are Western Europe, Far East and South America.

France's andalusite production is second only to South Africa. The deposit is concentrated in Brittany mining area. KA-grade concentrate contains Al2O359.0% and KB-grade Al2O353%.

India is a major producer of Sanshi in Asia, mainly producing kyanite and sillimanite. Concentrate products were exported to many industrialized countries before 1977, and now almost stop exporting. Hand-selected kyanite concentrates contain 58.59%, 54.55% and 50.8% Al2O3, with average iron content less than 0.7% and alkali content less than 0.45%. The Al2O3 content of massive sillimanite is > 6 1%, and Fe2O3 is <1%.

The annual output of Brazilian kyanite concentrate is 6.5438+500,000 ~ 20,000 t.

Switzerland is an important kyanite producer in Europe, with an annual output of 654.38+500,000 tons of concentrate.

2. China Shisan mineral resources

China Shisan is rich in mineral resources, and its distribution is shown in Table 3-4-5.

Table 3-4-5 Distribution of Shisan in China

① Existing concentrated products.

According to the classification of nonmetallic deposits by the former Ministry of Geology and Minerals, the mineral reserves of large, medium and small kyanite are as follows: large deposits should be above 2 million t; 500,000 ~ 2 million tons of medium-sized deposits; Small deposit below 500,000 t

According to the above classification, the large Shisan deposit discovered in China is as follows.

Kyanite: Yinshan in Nanyang City, Henan Province, Hanshan in Shuyang County, Jiangsu Province, Prague in Xinjiang, etc.

Andalusite: Baicheng in Xinjiang, Korla, Xiuyan-Fengcheng in Liaoning, Yangyanggou in Sangping Township, Xixia in Henan, etc.

Sillimanite: Jixi-Linkou in Heilongjiang, Xixia-Neixiang-Zhenping-Yexian in Henan, Putian in Fujian, Tuguiwula in Inner Mongolia, etc.

Nanyang, Henan Province, has a complete range of stone types, all of which are large-scale deposits with abundant reserves and high ore grade. It is called the "Golden Triangle" area of China Shisan mineral development.

Third, the technological characteristics of Shisan concentrate

The chemical composition of concentrate products directly affects its refractoriness, expansion rate and the performance of various products. In order to make refractory products have good performance at high temperature, there are strict requirements on the chemical composition of concentrate, especially the contents of aluminum, iron, titanium and alkali metals.

The current national industry standard YB4032-9 1 (Table 3-4-6) specifies the classification, codes and grades of kyanite, sillimanite and andalusite as follows:

Table 3-4-6 Physical and chemical indexes of kyanite, sillimanite and andalusite (YB4032-9 1)

Note: If the buyer has special requirements on quality, it shall be negotiated by the supplier and the buyer.

1) products are divided into kyanite, sillimanite and andalusite according to mineral structure;

2) kyanite concentrate is coded by the Chinese phonetic letters "LJ" of "blue" and "fine", and kyanite concentrate is divided into LJ-58 and LJ-55 according to Al2O3 content;

3) Sillimanite concentrates are coded by the Chinese phonetic alphabet GJ of "Si" and "Jing", and are divided into 58 and 54 brands according to the Al2O3 content;

4) Andalusite concentrate is coded by two Chinese phonetic letters "HJ" of "Red" and "Jing", and is divided into three grades according to Al2O3 content: 58, 55 and 52.

The product granularity is determined by both the supplier and the demander.

At present, domestic Shisan concentrate contains 55% ~ 56% Al2O3 and < 1.5% Fe2O3. A few factories can produce 57% ~ 59% Al2O3 with Fe2O3≤ 1%.

The physical and chemical properties of kyanite minerals at home and abroad are shown in Table 3-4-7 and Table 3-4-8 respectively.

Table 3-4-7 Physical and Chemical Properties of Kyanite Mineral Products in China

Table 3-4-8 Physical and Chemical Properties of Kyanite Group Mineral Products Abroad

During the heating process, kyanite minerals are irreversibly transformed into a mixture of mullite (3L2O32SiO2) and silica. This transformation is called mullite, and its expression is as follows:

3(al2o 3·SiO 2)→3al2o 3·2 SiO 2+SiO 2

Assuming that the purity of kyanite after heating is the theoretical value, according to the molecular weight of the substance before and after conversion, the theoretical conversion rate is 87.64%, namely:

Guide to the development and utilization of nonmetallic minerals in Henan Province

In fact, the Al2O3 content of kyanite concentrate in China is generally lower than the theoretical value, and the conversion rate of natural mullite also decreases. See Table 3-4-9 for the corresponding relationship between the concentrate of each grade and the conversion rate of mullite.

Table 3-4-9 Relationship between Kyanite Concentrate and Mullite Conversion Rate

The Al2O3 content of Shisan concentrate sold in the market is actually the TAl2O3 content, that is, the sum of Al2O3 in all aluminum-containing minerals in the concentrate. What is related to the conversion rate of mullite is the Al2O3 content of stone minerals in the concentrate, that is, SAl2O3.

During the heating process, the initial temperature, complete mullite temperature, conversion rate and linear expansion rate of Shisan concentrate are not only closely related to the content of Shisan minerals in the concentrate, that is, the purity, but also related to the composition and content of impurities and the particle size of the concentrate. When the chemical composition is determined, it mainly depends on the particle size of concentrate. A large number of experiments show that the expansion rate is positively correlated with the particle size. Taking kyanite concentrate as an example, Table 3-4- 10 lists the relationship between particle size and conversion temperature; Table 3-4- 1 1 lists the relationship between particle size and expansion rate, and Figure 3-4- 1 graphically shows Table 3-4-1.

Table 3-4- 10 Example of Decomposition Temperature of Kyanite Group Concentrate

The linear expansion rate of kyanite concentrates with different particle sizes is%

Note: sample φ 10×25mm cylinder.

Figure 3-4- 1 kyanite concentrate linear expansion rate

People use stone minerals mainly because they are irreversibly transformed into mullite and silica when heated, accompanied by volume expansion, and are used as special refractory raw materials. Therefore, there are strict requirements on the purity, particle size, impurity composition and content of Shisan concentrate.

Four. Mineral processing of Shisan mineral

Kyanite mineral is a refractory silicate mineral, and almost all mineral processing methods are used, such as manual selection, selective grinding, flotation, gravity separation and magnetic separation.

There are two main flotation processes for Shisan ore: acid flotation and alkaline flotation. Both flotation process schemes are related to the electrical properties of mineral surface and flotation reagent system. The flotation of Shisan ore mainly solves the separation of Shisan mineral from gangue minerals such as quartz, feldspar and mica. When kyanite is floated in acidic medium, the optimum pH value of pulp is 3.5 ~ 4.5 (adjusted by sulfuric acid or hydrofluoric acid), and the collector is sodium petroleum sulfonate or sodium alkylbenzene sulfonate. Acidic process has the advantages of good selectivity, less cleaning operation, clear flotation end point and wide range of flotation temperature, but it is easy to cause equipment corrosion and environmental pollution due to large acid consumption. When flotation is carried out in neutral and alkaline media, the optimum pH value of pulp is between 8 ~ 10 (adjusted by sodium carbonate and sodium hydroxide), and the collectors are fatty acids and their soaps, such as oleic acid and oxidized paraffin soap. Inhibitors include sodium silicate, lactic acid or formic acid, carboxymethyl cellulose (CMC), sodium pyrophosphate, etc. When fatty acids are used as collectors, the slurry temperature is required to be around 30℃.

Magnetic separation is often used in kyanite dressing. One is used as raw material for recovering or removing magnetic minerals. Second, it is used for concentrate reprocessing to remove harmful impurities in concentrate. Table 3-4- 12 lists the specific magnetization coefficients of Shisan minerals and gangue minerals.

Table 3-4- 12 Equal Specific Magnetization Coefficients of Stone and Three Minerals

1. Mineral processing of kyanite ore

Take Nanyang Kaiyuan kyanite concentrator as an example. The ore used in this factory is Yinshan kyanite, and the ore types are kyanite quartzite, flaky sericite kyanite quartzite, flaky brown iron sericite kyanite quartzite, massive kyanite and massive kyanite topaz. The content of kyanite mineral in the ore is about 15% ~ 20%, 60% ~ 70%, sericite 3% ~ 10%. TiO2 mainly comes from rutile minerals, accounting for about 1% in the ore. The particle size of rutile embedded cloth is fine, accounting for 80% below 0.05mm, and 10 ~ 20 micron accounts for about 50%. Kyanite contains some fine rutile, which increases the difficulty of titanium dioxide reduction in concentrate. K2O+Na2O, which has great influence on refractories, comes from mica minerals, which have good washability. Kyanite widely exists in kaolinite, sericite and pyrophyllite, so it is necessary to improve the grinding fineness. Topaz and kyanite in ore are difficult to separate, which increases the difficulty of mineral processing. Nanyang Kaiyuan kyanite adopts alkaline flotation, and its principle flow is shown in Figure 3-4-2.

Figure 3-4-2 Principle Process of Nanyang Kaiyuan Kyanite Mineral Processing

See table 3-4- 13 for kyanite concentrate grade of Kaiyuan kyanite mine in Nanyang City.

Table 3-4- 13 kyanite concentrate grade

Grace kyanite concentrator of American C-E company, East Ridge kyanite concentrator of kyanite mining company, kyanite concentrator of commercial ore company and kyanite concentrator of Lu Wei, Hebei, China all adopt the combined process of flotation-magnetic separation (or magnetic separation-flotation). See fig. 3-4-3 for the process flow of Dongling kyanite concentrator in the United States.

Figure 3-4-3 Process Flow of Kyanite Concentrator in Dongling, USA

See Figure 3-4-4 for the combined gravity separation-flotation process of kyanite in Idaho, USA.

Figure 3-4-4 kyanite beneficiation process flow chart in Idaho, USA

2. Sillimanite dressing

Qiliping, neixiang county is the main sillimanite producing area in Henan Province. Mineral processing is a combined process of magnetic separation and flotation (Figure 3-4-5). Firstly, a large number of gangue minerals, such as biotite, garnet and hematite, are removed by magnetic separation to improve the flotation grade and reduce the interference of impurity minerals on the flotation process. In the flotation operation, firstly, floatable minerals which have great influence on the quality of sillimanite concentrate are removed under natural pH conditions, and then sillimanite is flotation with decanoic acid collector under alkaline medium conditions. See table 3-4- 14 for concentrate indexes of neixiang county Tongtu sillimanite concentrator.

Figure 3-4-5 Neixiang Sillimanite Mineral Processing Flowchart

Table 3-4- 14 Concentrate of Tongtu Sillimanite Factory in neixiang county, Henan Province

See figure 3-4-6 for the principle flow of Jixi sillimanite dressing, and table 3-4- 15 for the concentrate index.

Figure 3-4-6 Main Process of Sillimanite Mineral Processing in Jixi

Table 3-4- 15 Sillimanite Concentrate in Jixi, Heilongjiang Province

3. Mineral processing of andalusite ore

Take the andalusite concentrator in Xixia, Henan as an example. The ore of this concentrator is the ore of Yangnaigou in Xixia. Yangnaigou andalusite ore is simple, mainly andalusite porphyritic biotite quartz schist. Andalusite, garnet and staurolite in the ore are porphyritic crystals, which form matrix with biotite. The ore is mainly porphyritic metamorphic structure, but andalusite porphyritic crystals are embedded firmly with the matrix, and the monomer is difficult to dissociate. There are black cross carbonaceous inclusions in andalusite, and the specific magnetization coefficient of this black cross is similar to that of andalusite. At the same time, the relative density of andalusite and gangue minerals is similar, andalusite is 3.1~ 3.2; Staurolite 3.74 ~ 3.83, carbon black cross 2.74 ~ 2.85. These problems increase the difficulty of mineral processing. However, the material composition of the ore is relatively simple, andalusite crystal is coarse and well crystallized, self-columnar, mostly kyanite. The technological process of ore washing-hand separation-gravity separation-high intensity magnetic separation is adopted. See figure 3-4-7 for the principle flow of Xixia andalusite beneficiation, and table 3-4- 16 for the concentrate index.

Figure 3-4-7 Main flowsheet of Xixia andalusite beneficiation

Table 3-4- 16 andalusite concentrate grade in Xixia, Henan Province

The origin of coarse-grained andalusite in China is Baicheng and Korla in southern Xinjiang, and its beneficiation is similar to Xixia Andalusite Concentrator. Gravity separation-magnetic separation process is generally adopted, and the main beneficiation methods are jigging, dense medium and shaking table.

Fine andalusite is recovered by flotation. In the process of flotation, anionic collectors include oleic acid, hydroxamic acid and sodium petroleum sulfonate. Cationic collector is dodecylamine acetate, which is mostly carried out in acidic or weakly acidic pulp. High intensity magnetic separation process is used to separate iron minerals.

Cerro Mining Company in North Carolina, USA and some andalusite concentrator in South Africa all adopt the combined gravity and magnetic process. See fig. 3-4-8 for the process flow of Subaru andalusite concentrator in Tolan, South Africa.

Figure 3-4-8 Process Flow of Subaru Andalusite Concentrator in Tolan, South Africa

Application of verb (abbreviation of verb) stone three minerals

Stone minerals are irreversibly transformed into mullite and silica at high temperature, accompanied by volume expansion, so they become important refractory raw materials. See table 3-4- 17 for the development and application of Shisan minerals in China.

Table 3-4- 17 Development and Application of Shisan in China

sequential

China is rich in bauxite resources, but the impurity content of bauxite raw materials in China is high, and Fe2O3+TiO2+RO+R2O is about 7%. Among them, the content of TiO2 is about 3.5%, and the content of TiO2 in southwest high-titanium bauxite is relatively high. High impurity content, easy to melt at high temperature and form liquid phase at low temperature. The content of TiO2 is high, and the viscosity of the formed liquid phase is low. The high content of glass phase and corundum and low content of mullite in the material phase affect the high temperature performance and service temperature of the product, especially the low creep refractory products can not be produced.

Adding "three stones" (additives) into bauxite raw materials increases the content of mullite crystal phase, especially in the matrix part, which forms a good mullite network during the mullite process and improves the microstructure of the material. Therefore, the high-temperature performance, high-temperature strength and re-burning shrinkage of refractory products have been significantly improved, and a variety of alumina-based high-efficiency refractory materials and new products have been developed, such as low creep bricks, high load soft bricks and high thermal shock bricks. Especially all kinds of low creep bricks, such as sillimanite low creep bricks, andalusite low creep bricks and kyanite low creep bricks, have obviously improved the high temperature volume stability of bricks for hot blast stoves.

Unshaped refractory, also known as block refractory, is a new type of refractory without calcination. The unshaped refractory is a mixture of refractory aggregate, powder, binder or other additives. Coarse-grained andalusite is the aggregate of unshaped refractories, which determines the physical and mechanical properties and high-temperature service performance of unshaped refractories, and is also an important basis for determining the material properties and application scope. Andalusite and sillimanite concentrates are used as powders and are matrix materials. Kyanite is a good expansion agent for unshaped refractories, which can reduce the shrinkage of materials at high temperature and prevent the structure from peeling off, because the volume expansion related to mullite process is the largest. See table 3-4- 18 and table 3-4- 19 for the granularity requirements of refractory aggregate and powder.

Table 3-4- 18 Physical and Chemical Properties and Particle Size of Hard Clay Aggregates and Powder (YB22 14-78)

Table 3-4- 19 Physical and chemical properties and particle size of high alumina aggregate and powder (YB22 15-78)

For Shisan concentrator, it is necessary to produce qualified concentrate according to the requirements of application units, which not only has strict requirements on concentrate composition, but also has corresponding requirements on refractoriness and particle size of concentrate.

The second chapter discusses the problems existing in the mineral processing technology of Shisan Mine in Henan Province. Because some technical problems have not been solved in the process of mineral processing, the cost of mineral processing is high and the economic benefit of mineral processing plant is poor.

Main references

[1] Editorial Committee of Handbook of Nonmetallic Mining Industry, Handbook of Nonmetallic Mining Industry (Volumes I and II), Metallurgical Industry Press, 1992.

[2] Qian, Practical Handbook of Refractory Materials, Metallurgical Industry Press, 1992.

Lin Binyin, Kyanite, Andalusite and Sillimanite, Metallurgical Industry Press, 1998.

[4] Editorial Committee of China Metallurgical Encyclopedia Refractory Volume, China Metallurgical Encyclopedia Refractory, Metallurgical Industry Press, 1992.

Li et al., Applied Mineralogy, Science Press, 1995.