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Analysis of influencing factors on dewatering effect of horizontal centrifuge in Coal Preparation Plant



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Horizontal centrifuge is mainly used in Coal Preparation Plant slime and clean coal dewatering in the coal industry. Because of its small volume, no auxiliary equipment, simple processing system, large material handling capacity and many other advantages, horizontal centrifuge has been well applied in western mining area of China, but its disadvantages are also obvious, such as complex structure, high energy consumption, dewatering effect is easily affected by many factors, among which the dewatering effect is limited Whether it can be applied or not is the main factor. Therefore, it is necessary to analyze the influencing factors of horizontal centrifuge dewatering effect, and now HSG1400 horizontal centrifuge is taken as an example to study.

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Working Principle of Centrifuge

HSG1400 horizontal centrifuge is composed of feeding trough, screen base, screen surface, casing, transmission device, support device, oil circuit system, vibration exciter, motor, oil pump, cooling filter and other units. After the centrifuge is started, the screen basket rotates and vibrates under the action of the motor. After vibration, the screen surface material enters the small end of the centrifuge screen basket through the feeding trough. As the screen basket rotates and vibrates, the material is in the screen basket. The inner side slides from the small end to the large end. During this process, the moisture in the material is thrown out from the screen gap of the screen basket under the centrifugal action. The dehydrated material falls from the large end of the screen basket into the chute and enters the product through the belt In the warehouse, the centrifugal liquid thrown from the screen of the screen basket enters the sump tank through the liquid discharge port. Meanwhile, the rotation and vibration of the screen basket can realize dehydration and it can also promote the loosening of materials through vibration, which is conducive to prevent the occurrence of blockage of screen gap in the screen basket, and thus improve the dewatering effect of centrifuge.

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Analysis of Dehydration Factors

Feed Moisture

The dehydration effect of the horizontal centrifuge is closely related to the feed concentration. Taking the HSG1400 horizontal centrifuge as the research object, the dehydration effect test is carried out by adding a high-pressure water valve in the centrifuge feed tank and adjusting the feed concentration through the high-pressure water volume. The results show that with the increase of the feed concentration, the moisture of the obtained product shows a decreasing trend. When the feed concentration is lower than 20%, the product moisture content is higher, which will seriously affect the product quality. Meanwhile, the low concentration materials are also easy to speed up the screening. The abrasion of the basket is not conducive to improving the efficiency of the centrifuge; when it exceeds 20%, the product moisture and the feed concentration decrease in inverse proportion to a linear relationship. However, the higher the feed concentration, the better, because when the feed concentration is high, it is easy to cause blockage of the centrifuge trough, which is not conducive to improving the efficiency of centrifuge dewatering. Therefore, when using horizontal centrifuges for material dehydration, it is necessary to reasonably control the feed concentration to ensure the best moisture content of the product, which is not only conducive to improving the product quality, but also can extend its service life and improve the use efficiency.

Width of Screen Basket Sewing

Screen basket is the key component of horizontal centrifuge, which is mainly composed of upper and lower flanges, reinforcing ribs, conical screen cylinder and other parts. The screen cylinder is generally welded by fan-shaped screen plate. The screen basket will be seriously impacted by the feeding material when it works, so it is easy to replace if it is not used properly. The size of the screen gap directly affects the dewatering effect. For example, if the screen gap is too small or the screen basket is replaced, the dehydration effect is more general. With the use of the screen basket, the screen gap is gradually increased due to wear and other factors, and the dehydration effect has an increasing trend. The main reason is that the small screen gap is easy to block the coal slime, resulting in the relative decrease in the width of the screen gap, which affects the moisture content of the feed through, resulting in the increase of product moisture. A coal preparation plant in Pingshuo used an HSG1400 horizontal centrifuge to study the relationship between the width of the screen gap and the dehydration effect. The test results show that when the width of the screen basket is increased from 0.25mm to 0.35mm, the product moisture will increase from 16%. Reduce to 12%, the dehydration effect is obvious. However, if the screen gap is too large, it will affect the recovery of coarse slime. Therefore, the effect of coal slime recovery and dehydration should be taken into consideration to determine the screen gap of the screen basket.

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Feeding Size

The particle size composition of the material affects the water permeability of the material layer. For example, when there are more materials with small particle size, it is easy to fill the coarse material particles to form a material layer with better compactness and poor water permeability. When the material passes, the allowable material size It is much smaller than the screen gap of the screen basket; when the coarse material has more particles, the gap formed by the coarse material is larger. When the material passes, the difficulty of water passing through the screen basket will be greatly reduced, which is beneficial to reduce the product moisture, just like fine river sand Water barrier is easy to form, and coarse river sand has better water permeability. Both theoretical research and practice have shown that appropriately reducing the incoming small-grained materials is beneficial to reduce product moisture and improve product quality.

Feeding Speed

In order to study the relationship between feeding speed and dehydration, the field test was carried out. Under the condition that the feed concentration was set to 30%, the blanking height was set as 8m, 6m, 4m and 2m, which was equivalent to changing the feeding speed by changing the feeding potential energy. That is, the higher the blanking height is, the faster the feeding speed is. Thus, the moisture content of the measured product can be obtained under different feeding speeds. The test results show that when the blanking height is 8m, the product moisture is 27%; when the blanking height is 6m, the product moisture is 21%; when the blanking height is 4m, the product moisture is 15%; when the blanking height is 2m, the product moisture is 2%. It can be seen that although the blanking height and moisture are not inversely proportional, but in a certain range, with the increase of blanking height, that is, with the increase of feeding speed, the moisture content of the product is increasing. In view of this, in order to improve the dewatering effect of horizontal centrifuge, it is necessary to determine the feeding speed reasonably, that is, to control the feeding speed by changing the height of blanking.

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Measures to Improve Dewatering Effect

(1)Reasonably control the incoming water content, clean the screen surface of the sorting materials regularly, and ensure that the incoming concentration is reasonable. According to the research results of the relationship between the dewatering effect of the centrifuge and the concentration of the materials, the optimal range of the incoming concentration should be guaranteed to be 40%-65%. Meanwhile, add high-pressure water pipes as needed to adjust the feed concentration in real time, and at the same time solve the problem of trough blockage caused by high-concentration materials.

(2)It can be seen from the analysis of feed particle size and centrifuge dewatering effect that too much fine material is not conducive to improving centrifuge dewatering. Therefore, the content of fine material should be strictly controlled. At the same time, in order to prevent the formation of low permeability material layer of fine materials from affecting the dewatering effect, the screen gap flushing should be carried out irregularly according to the needs to ensure the optimal dewatering effect.

(3)In order to improve the dewatering effect of centrifuge, it is necessary to reduce the blanking height and then the feeding speed, or feed the chute to the slope buffer tank, so as to reduce the feeding speed.

(4)According to the needs, the screen basket with the width of the screen gap that meets the dewatering effect should be selected reasonably, and the blocking of the screen gap should be strictly prevented from affecting the dehydration.

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Conclusion

Horizontal centrifuge is a common dewatering equipment for slime and clean coal in coal preparation plant, and dewatering effect is the key factor affecting its application. Therefore, when using horizontal centrifuge, it is necessary to understand the main influencing factors of dewatering effect on the basis of mastering its working principle. Only in this way can we take targeted measures to solve the dewatering problem of centrifuge and improve product quality.

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