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What kind of equipment is EPS used in the coal preparation plant?



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Gequan coal preparation plant is a mine type coal preparation plant with a design capacity of 0.90Mt/a. The main coal preparation processes are + 50mm raw coal pre discharge, 50 ~ 1mm pressurized three product dense medium, 1 ~ 0.25mm CSS coarse slime separation, -0.25mm direct flotation, two-stage concentration and two-stage recovery of tailing slime. In the coarse slime separation, the coarse slime is separated by CSS Coarse Slime Separator. The CSS overflow is combined with the clean coal magnetic tail of the dense medium system. After dewatering and desliming through the sieve bend, it enters the Slime Centrifuge for secondary dewatering and then enters the clean coal product.

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In the process of coarse slime separation, the desliming effect of sieve bend directly affects the ash content of coarse clean coal products. According to the process requirements of Gequan coal preparation plant, the ash content of coarse clean coal should be controlled within 10.5%. After testing, the ash content of coarse clean coal product is generally about 12% after dewatering and desliming by sieve bend and centrifuge. The screening efficiency of sieve bend is low, resulting in high ash fine mud pollution of coarse clean coal products. Only by reducing CSS overflow ash content or dense medium clean coal "back ash" can the quality of clean coal be stabilized. Therefore, if a screening equipment with higher screening efficiency can replace the sieve bend, the ash content and moisture content of coarse clean coal can be further reduced, or the clean coal recovery rate can be increased again under the condition of ensuring the ash content of clean coal is qualified, so as to improve the economic benefits.

Equipment Development

In recent years, with the increase of fine coal content and the deterioration of coal quality, the following phenomena have appeared in domestic coal preparation process:

(1) For coarse slime separation, even if the special separation equipment such as coarse slime interference bed separator is used, it is easy to cause the phenomenon of clean coal exceeding the standard. The main performance is that the coarse clean coal still contains more high ash fine mud after dewatering by centrifuge, which seriously affects the final ash content of clean coal;

(2) In many coal preparation plants, the ash content of flotation tailings is low, especially in the 0.075-0.125mm size fraction, which is about 18% - 32%, and some of them have a high concentrate rate of 60%. It is necessary to use fine-grained classification screen to recover the low ash coarse particles and separate them again to avoid the loss of clean coal;

(3) At present, the most refined process in coal preparation field is "four particle separation", but there is still a problem of 0.1 mm high-efficiency classification in this process;

(4) In some places, the content of high ash fine mud is very large, and there is sliming phenomenon. It is necessary to carry out classification before flotation to realize the so-called "desliming flotation" to minimize the impact of high ash fine mud on the whole slime water system, which also reflects the demand for fine-grained accurate screening.

To sum up, these phenomena and problems, after referring to the principle, structure and performance of various fine-grained classification equipment at home and abroad, the new EPS high-efficiency fine-grained classification screen has basically completed the research and development, which is first used to desliming the overflow of CSS Coarse Slime Separator and clean coal magnetic tail.

The equipment is a new type of patented equipment specially for fine-grained wet screening of minerals. It has the technologies of controllable long-distance screening, continuous pulp recycling by material overturning, compound force field effect, high-efficiency cleaning of screen seam, and convenient screen removal. It has the characteristics of high open hole rate, large processing capacity, high screening efficiency and non blocking screening, which solves the problems of traditional fine particle classification and operation A series of problems. The main technical parameters are shown in Table 1.

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Application Effect

Sieve bend+Centrifuge Process Coarse and Fine Coal Ash

It can be seen from table 2 that under the combined process of arc screen and centrifuge, the content of coarse and fine coal ash reaches 12.03%, the content of-0.125mm particle size is 10.03%, and the ash content is 46.11%. It indicates that a large amount of high ash fine mud is not separated out and enters the coarse clean coal products, resulting in high ash content of coarse and fine coal.

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Ash Content of EPS Screen and Coarse Clean Coal Products

It can be seen from table 3 and table 4 that after the application of EPS-1500 high-efficiency fine-grained screen, the separation and classification effect of CSS Coarse Slime Separator and EPS combined process on coarse slime has been greatly improved: the content of coarse and fine coal ash is reduced from 12.03% to 10.25%, only 2 percentage points; the content of - 0.125mm particle size is reduced from 10.03% to 3.91%, and this part of high ash fine mud is removed into coarse clean coal became the key to fully meet the requirements of clean coal product index.

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Screening Efficiency of EPS

According to the national standard GB/475-2008 (manual sampling method for commercial coal samples), the feed, the products on and under the screen of EPS-1500 high-efficiency fine-grained classification screen were sampled. All samples were screened according to GB/477-2008 (coal screening test method). According to the national standard GB/T15716-2005 (evaluation method for process performance of coal screening equipment), the screening effect of screening equipment was evaluated.

According to the test results, when the distribution particle size is 0.125mm, 20.40% of the feed is smaller than 0.125mm, 60.70% of the products under the sieve are smaller than 0.125mm, and 4.84% of the products on the screen are smaller than 0.125mm

E=60.70×(20.40-4.84)/20.40×(60.70-4.84)=82.89%。

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According to the process requirements of Gequan coal preparation plant, when the coarse and fine coal ash content is reduced to 10.5%, the clean coal recovery rate can be increased by 0.26%. According to the annual washing amount of 650000 tons and the price of coke clean coal of 1300 yuan/ t, the annual efficiency can be 65 × 0.26% × 1300 = 2.197 million Yuan.

Conclusion

Aiming at the difficult technical problem of fine-grained slime classification in coal preparation process, a new technology of precise classification of coarse slime with EPS high-efficiency fine-grained screen was creatively studied; the industrial application of EPS high-efficiency fine-grained screen in Gequan mine coal washing plant is completed, and the 0.125mm fine-grained grading screen is effectively realized, the limit rate was less than 5%, the comprehensive screening efficiency reached more than 80%, and good economic benefits were obtained.

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