Application of small diameter hydrocyclone in kaolin dressing

Hydrocyclones useful as kaolin, quartz, feldspar and other non-metallic ore grade or desliming, a small amount for the dehydration industry. When used as a grading device , it is mainly used to form a grinding-grading system with a grinding machine. The hydrocyclone configuration is shown in Figure 1. The upper part is a hollow cylinder and the lower part is an inverted cone that communicates with the cylinder. The two form the working cylinder of the hydrocyclone. The upper end of the cylindrical cylinder is tangentially provided with a feed pipe, and the top is provided with an overflow pipe and an overflow pipe. There is a grit chamber at the bottom of the conical cylinder. Currently used materials are mainly stainless steel, polyurethane, rubber and so on.

The slurry enters the cylindrical cylinder from the feeding pipe in a tangential direction with a pressure of 0.2 to 0.5 MPa and a high speed of 5 to 12 m/s , and then rotates around the axis at a high speed, generating a large centrifugal force. Particles with different particle sizes and densities in the pulp, due to the different centrifugal forces, their movement speed, acceleration and direction in the cyclone are also different. The coarse and heavy particles are subjected to large centrifugal force and are thrown to the wall. Rotate down to the bottom according to the spiral path, and discharge it as a grit from the grit chamber. The fine and light particles are subjected to a small centrifugal force and are brought to the center, and an inner spiral ore flow is formed in the center of the conical cylinder to be discharged as an overflow from the overflow pipe.

The advantages of the hydrocyclone are: 1 simple construction, no moving parts; 2 low equipment costs. Easy maintenance, small floor space, low capital construction cost; 3 unit volume processing capacity; 4 fine grain size, currently up to 2 μ m ; 5 high classification efficiency, up to 80% ; 6 pulp in cyclone The amount and time of detention is small, and it is easy to handle when shutting down.

Beijing Paleozoic Powder Technology Co., Ltd. is mainly engaged in the development, production and sales of ultra-fine powder crushing, super-segmentation and selected purification equipment. In recent years, it has continuously cooperated with research institutes or independently developed small-caliber cyclone equipment, which has been greatly applied in the non-metallic mining industry. At present, as the largest kaolin production enterprise in China, Yankuang Beihai Kaolin Co., Ltd. took the lead in adopting its φ 25 and φ 50 polyurethane hydrocyclones to expand the application of small-caliber cyclone in kaolin mineral processing .

Through the test of the National Non-Metallic Mineral Deep Processing Research Center, the production process of the φ 75 , φ 50 and φ 25 three-stage cyclone combined with the horizontal centrifuge to produce paper kaolin was determined after the pulping and sand removal ( Fig. 2) .

The cyclone products produced by Beijing Paleozoic Powder Technology Co., Ltd. use primary color polyurethane, without adding any pigment substances. The color of the polyurethane cyclone is a traditional understanding of dark red. The purpose of adding pigments is to make people see polyurethane as little as possible. Bubbles during polymerization. The primary color polyurethane is light yellow transparent, which can clearly see the movement state of the slurry in the swirling fluid, which is convenient for the operator to find out the quality of the cyclone operation. In addition, the isostatic pressure "human" type pipe system is adopted for easy operation and maintenance.

From the above data analysis, each section of the cyclone increases the content of - 2 μ m in the product by about 10% , and the content of Al ₂ O ₃ increases step by step. The purification effect of kaolin is obvious, while the relative change of K ₂ O / Na ₂ O content is not large. This is mainly due to the fact that as the weathered kaolin, the mica in the ore has a larger ratio of diameter to thickness, and the conventional re-election method is basically difficult to separate it from the kaolin. However, in the case of the φ 50 and φ 25 cyclone groups alone, the difference in the overflow of Al ₂ O _{3 is} relatively small, and the purification effect on kaolin is small. It is estimated that the direct use of the φ 25 cyclone group should basically achieve the same overflow index. It is generally believed that the narrower the particle size range, the correspondingly lower the sorting effect of the cyclone.

According to the design process of the design institute, combined with the actual characteristics of the cyclone of the Paleozoic, the φ 75 cyclone has a large taper and a large processing capacity, and the sorting effect should be much larger than that of the national non-metallic mineral deep processing research center equipment. Therefore, a preliminary exploration of the omission of the number of cyclone segments was made. At that time, due to the limited detection conditions, only the - 2 μ m content of the cyclone overflow was detected, and the test results were basically close.

This set of experiments provides an early basis for current production line testing. In the trial production and debugging process, the relevant opinions were exchanged with the Suzhou Non-Metallic Mining Industry Design and Research Institute, and preliminary approval was obtained. However, the test data was not complete and was not implemented.

Since then, in the normal production process, the process analysis test has been gradually reduced, but the feasibility of the vision can be foreseen from a series of inconsistent test data. In mid-May 2006, because the resources have been depleted, reducing the degree of weathering. The content of kaolin in the middle-grain grade is gradually reduced, and the quality of the underflow product has been greatly reduced. This is an inevitable trend. Therefore, YTC-3/YTC-5 products have become a great difficulty in theory . In response to this reality, the idea of ​​omitting the cyclone group once again is proposed. Under the condition that the overflow product index is not changed, the yield of the overflow product is improved, and the diversity of the underflow product is reduced, and the economic benefit is improved. The specific test data is summarized in Table 2 .

It is very clear from the data in Table 2 that the final 25Y chemical composition index, omitting the cyclone group and not omitting the cyclone group, the difference is not large, the omitted Al ₂ O ₃ content is slightly lower, Fe ₂ O ₃ content is slightly higher. The main physical properties - 2 μ m content, whiteness and whiteness of firing are within acceptable tolerances. The impact on the production of ceramic products should be negligible.

According to the production data, the yield of the small-diameter cyclone produced by Beijing Gushengdai Fine Powder Technology Co., Ltd. and the recovery rate of - 2 μm are relatively high, which is one of the ideal product purification and classification equipment, but Some problems have also been exposed during the actual use, and should be continuously improved and improved during use.

( 1 ) The grit nozzle and the swirling fluid are fixed by stainless steel Nuts. To a certain extent, the fixing method corresponds to the "human" type stainless steel bracket, which is beautiful and corrosion-resistant, and the grit nozzle is easily replaced. However, when the grit nozzle is replaced, the stainless steel thread on the nut can easily cut or cut the thread on the swirling fluid, causing the swirling fluid to be unreusable. It has been improved and now uses a plastic nut for good fastening and does not damage the thread of the fluid.

( 2 ) Polyurethane products have good corrosion resistance and wear resistance, but they have a certain service life and are easy to age. Especially at present, many small-scale production enterprises in China use open-air sorting, and weathering and aging resistance is a very important issue. Beijing Gushengdai Fine Powder Technology Co., Ltd. is actively developing and adding anti-aging agents together with the Institute to extend the aging time and carry out relevant tests to improve the service life of cyclone products.

( 3 ) Careful analysis of the actual production data from the original design process, φ 50 , φ 25 in the grading purification process, the effect of φ 50 is not very obvious, the process can be omitted, to achieve basically the same result, and the product The yield will be improved to some extent. This situation is not a problem with the cyclone itself, but rather a process design. We generally think that the particle size of the φ 50 cyclone control is d90=10 μ m , and the φ 25 cyclone can reach d90=5 μ m . Due to the relatively incomplete degree of weathering of the North Sea kaolin resources, the fine grain size is caused. Too little, it is difficult to directly control the d90=5 μ m using the φ 25 cyclone , so the increase of one-stage cyclone classification is used. Therefore, objectively speaking, in the process of process design, for the cyclone grading process matching, the φ 25 cyclone can be directly used after the φ 75 cyclone is used.

With the rapid development of the non-metallic mineral industry in recent years, the application of cyclones has become more and more extensive, especially the small-diameter cyclone is more and more used in the super-segmentation level. Beijing Gushengdai Fine Powder Technology Co., Ltd. The developed silicon carbide φ 10 cyclone has made outstanding contributions in this respect. At present, China Kaolin Co., Ltd. adopts its complete replacement for horizontal screw centrifuges and other equipment, and the production cost is greatly reduced under the condition of constant product quality. .

As we all know, the parameters affecting the grading effect of the cyclone are very numerous, structural, process operation and feedstock properties, and often interrelated, mutually restrictive, not easy to adjust and control, so this requires many domestic spins The flow generator manufacturer can strengthen the technical exchange, improve the design of the structure of the cyclone, and continuously introduce new products. At the same time, the application enterprises that are cyclones should also report the relevant experience and data. Together, we will continue to develop the production and application of cyclones, making them play a greater role in industrial applications and production.