Coal slurry concentration device and concentration method

Abstract

The invention discloses a coal slurry concentration device and a concentration method, and belongs to the technical field of coal slurry preparation, the concentration device comprises a mill grading system and a self-reflux system, the self-reflux system comprises a first self-reflux mechanism and a second self-reflux mechanism, the mill grading system comprises a rod milling mechanism, a coarse grinding mechanism, a fine grinding mechanism and an ultrafine grinding mechanism, and the rod milling mechanism comprises a first self-reflux mechanism and a second self-reflux mechanism. An outlet of the rod milling mechanism is connected with an inlet of the waste recovery system, an outlet of the waste recovery system is connected with an inlet of the rod milling mechanism through the first self-backflow mechanism, the waste recovery system is connected with the coarse grinding mechanism, the coarse grinding mechanism is connected with the fine grinding mechanism, and the fine grinding mechanism is connected with the superfine grinding mechanism. And the superfine grinding mechanism is connected with the rod grinding mechanism through a second self-backflow mechanism. According to the coal slurry concentration device and method, the rod mill, the fine mill and the superfine mill are matched to form a three-peak grain size distribution relation, so that the fluidity and the stability of the coal slurry are improved, and the concentration of the coal slurry is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of coal slurry preparation, and in particular to a coal slurry concentration device and a coal slurry concentration method. Background Art

[0002] The gasification section is the leader of coal chemical enterprises. As an important raw material in the gasification reaction process, the increase in coal slurry concentration can reduce the oxygen consumption and coal consumption in the gasification reaction, increase the effective gas (CO+H2) content, and thus achieve the purpose of increasing the production of synthetic ammonia, reducing raw material consumption and reducing the operating load of high-pressure coal slurry pumps. However, the increase in the concentration of water-coal slurry is an industry-wide technical problem. At present, most coal chemical enterprises use the traditional rod (ball) mill production process. The water-coal slurry produced has too many intermediate particles and is distributed in an olive shape. There is still a lot of room for improvement in the mass fraction of water-coal slurry, and there are disadvantages such as high viscosity and poor rheology, which cause the coal gasification specific coal consumption and specific oxygen consumption to be high, and the effective gas component to be low, which seriously affects the economic efficiency of water-coal slurry gasification. In particular, as the price of high-quality coal types continues to rise, the raw coal used for water-coal slurry gasification has to be selected from low-grade coal types that are difficult to slurry. In this context, it is particularly important to seek suitable pulping processes and equipment to increase the concentration of water-coal slurry in the gasification system. Summary of the invention

[0003] The purpose of the present invention is to provide a coal slurry concentration device and a method. Through the cooperation of a rod mill, a fine mill and an ultrafine mill, a three-peak particle size grading relationship is formed. After adding nano-scale ultrafine particles, the original particle size distribution is made more reasonable. The ultrafine particles not only serve as a medium to fill the gaps, but also coat the surface of coarse particles, increase the hydrophilicity of the surface of the coarse coal particles, play a role in lubrication and drag reduction, thereby improving the fluidity and stability of the coal slurry and further increasing the concentration of the coal slurry.

[0004] To achieve the above-mentioned purpose, the present invention provides a coal slurry concentration device, including a mill grading system and a self-reflux system, the self-reflux system including a first self-reflux mechanism and a second self-reflux mechanism, the mill grading system including a rod mill mechanism, a coarse grinding mechanism, a fine grinding mechanism and an ultrafine grinding mechanism, the outlet of the rod mill mechanism is connected to the inlet of a waste recovery system, the outlet of the waste recovery system is connected to the inlet of the rod mill mechanism through the first self-reflux mechanism, the waste recovery system is connected to the coarse grinding mechanism, the coarse grinding mechanism is connected to the fine grinding mechanism, the fine grinding mechanism is connected to the ultrafine grinding mechanism, and the ultrafine grinding mechanism is connected to the rod mill mechanism through the second self-reflux mechanism.

[0005] Preferably, the rod mill mechanism comprises a rod mill, the rod mill is connected to a drum screen, the drum screen is respectively connected to a mill discharge trough and a waste recovery system, the waste recovery system comprises a waste pulp trough, and the waste pulp trough is connected to a waste pulp pump.

[0006] Preferably, the coarse grinding mechanism includes a coarse pulp trough, which is connected to the mill discharge trough, a slurry pump is provided between the coarse pulp trough and the mill discharge trough, the outlet of the coarse pulp trough is connected to the coarse pulp pump, and the coarse pulp pump is respectively connected to the fine grinding mechanism and the ultrafine grinding mechanism.

[0007] Preferably, the fine grinding mechanism includes a fine grinder, which is connected to the coarse slurry pump through a coal slurry pipeline to the fine grinder, on which a fine grinding coal slurry flowmeter and a fine grinding regulating valve are provided, and the fine grinder is connected to an ultrafine slurry tank.

[0008] Preferably, the ultrafine grinding mechanism includes an ultrafine grinder, which is connected to the coarse slurry pump through a coal slurry pipeline to the ultrafine grinder, on which an ultrafine grinder coal slurry flowmeter and an ultrafine grinder regulating valve are provided, the ultrafine grinder is connected to an ultrafine slurry tank, and the ultrafine slurry tank is connected to a second self-reflux mechanism.

[0009] Preferably, the second self-reflux mechanism includes a second coal slurry recovery pipeline, an ultrafine slurry pump is provided between the second coal slurry recovery pipeline and the ultrafine slurry tank, the other end of the second coal slurry recovery pipeline is respectively connected to the rod-removing mill inlet pipeline and the rod-removing mill outlet pipeline, a mill inlet flowmeter and a mill inlet regulating valve are provided on the rod-removing mill inlet pipeline, and a mill outlet flowmeter and a mill outlet regulating valve are provided on the rod-removing mill outlet pipeline.

[0010] Preferably, the ultrafine pulp pipeline of the rod mill outlet pipeline passes through the drum screen and extends into the inner outlet of the rod mill.

[0011] Preferably, the waste slurry pump is connected to the first coal slurry recovery pipeline of the first self-reflux mechanism, and the other end of the first coal slurry recovery pipeline is connected to the inlet of the rod mill.

[0012] Preferably, the mill discharge trough is connected to a low-pressure coal slurry pump, and the outlet of the low-pressure coal slurry pump is respectively connected to the desizing coal slurry trough and the first coal slurry recovery pipeline.

[0013] A method for concentrating coal slurry, using the above-mentioned coal slurry concentrating device, comprises the following steps: Step 1: During the preparation of high-concentration coal slurry, the rod mill, fine mill and ultrafine mill are operated simultaneously. The waste slurry tank is used to recover the coal slurry that occasionally overflows. The dry basis ratio of the extracted coarse slurry to the dry basis ratio of the raw coal entering the rod mill is controlled at 0.1:1-0.15:1. The flow rate of the fine slurry from the ultrafine slurry tank back to the rod mill inlet is normally controlled at 1-2 cubic meters. As the steel rods of the rod mill gradually wear, it gradually increases to 3-4 cubic meters. All other fine slurries are returned to the rod mill outlet. Step 2: Set the ratio of coal slurry entering the coarse slurry tank to grinding water entering the coarse slurry tank, reasonably control the fine slurry concentration, control the water-slurry ratio of the coarse slurry at 0.5:1, add more grinding water when making fine slurry, the grinding water volume at the rod mill inlet should be less than when the fine mill is not turned on, and the final coal slurry concentration of the low-pressure coal slurry pumped into the large coal slurry tank is adjusted by the grinding water volume entering the rod mill; Step 3: According to the fine-grind coal slurry flow rate and the ultra-fine-grind coal slurry flow rate, use the fine-grind regulating valve and the ultra-fine-grind regulating valve to control the ratio of the coarse slurry entering the fine mill and the ultra-fine mill to 1:1-2:1, maintain the ultra-fine slurry flow rate unchanged, and adjust the fine slurry amount; Step 4: During the maintenance of the fine mill or ultrafine mill, a small amount of coal slurry from the outlet of the low-pressure coal slurry pump is sent back to the inlet of the rod mill for circulation. Through secondary grinding, the concentration of the coal slurry is kept from being reduced too much.

[0014] Therefore, the present invention adopts the above-mentioned coal slurry concentration device and concentration method, which has the following beneficial effects: (1) The coal slurry concentration device and concentration method of the present invention form a three-peak particle size distribution relationship through the cooperation of a rod mill, a fine mill and an ultrafine mill. After adding nano-scale ultrafine particles, the original particle size distribution is made more reasonable. The ultrafine particles not only fill the gaps as a medium, but also coat the surface of the coarse particles, thereby increasing the hydrophilicity of the surface of the coarse coal particles, playing a role in lubrication and drag reduction, thereby improving the fluidity and stability of the coal slurry and further increasing the concentration of the coal slurry; (2) The device and method for concentrating coal slurry of the present invention add a proper amount of ultrafine slurry to the inlet of the rod mill to increase the fluidity of the coal slurry in the rod mill, improve the viscosity of the coal slurry caused by the reduction of water added to the rod mill, assist in grinding, ensure the normal operation load and grinding effect of the rod mill, and thus achieve the effect of concentrating the coal slurry after water reduction; (3) The device and method for concentrating coal slurry of the present invention are as follows: the rod mill is equipped with a coal slurry recovery pipeline. On the one hand, the outlet of the low-pressure coal slurry pump can allow a small amount of coal slurry to return to the rod mill through the coal slurry recovery pipeline. On the other hand, the coal slurry in the waste slurry tank can also be recycled to the inlet of the rod mill. No manpower is required to collect the waste slurry. After the secondary grinding of the rod mill, this part of the refluxed or recycled coal slurry effectively increases the proportion of 200 mesh and 325 mesh in the coal slurry, which is beneficial to increase the concentration of the coal slurry.

[0015] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a flow chart of a coal slurry concentration device and a coal slurry concentration method embodiment.

[0017] Reference numerals 1. Mill inlet flowmeter; 2. Mill inlet regulating valve; 3. Mill outlet flowmeter; 4. Mill discharge trough; 5. Waste slurry trough; 6. Waste slurry pump; 7. Low-pressure coal slurry pump; 8. Mixing slurry pump; 9. Coarse slurry pump; 10. Fine grinding coal slurry flowmeter; 11. Fine grinding regulating valve; 12. Ultrafine grinding regulating valve; 13. Ultrafine grinding coal slurry flowmeter; 14. Ultrafine slurry pump; 15. First coal slurry recovery pipeline; 16. Drum screen; 17. Rod mill; 18. Mill outlet regulating valve; 19. Fine mill; 20. Ultrafine mill; 21. Ultrafine slurry trough; 22. Coarse slurry trough. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0019] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] Embodiment 1 like Figure 1 As shown, the present invention provides a coal slurry concentration device, including a mill grading system and a self-reflux system, the self-reflux system including a first self-reflux mechanism and a second self-reflux mechanism, the mill grading system including a rod mill mechanism, a coarse grinding mechanism, a fine grinding mechanism and an ultrafine grinding mechanism, the outlet of the rod mill mechanism is connected to the inlet of a waste recovery system, the outlet of the waste recovery system is connected to the inlet of the rod mill mechanism through the first self-reflux mechanism, the waste recovery system is connected to the coarse grinding mechanism, the coarse grinding mechanism is connected to the fine grinding mechanism, the fine grinding mechanism is connected to the ultrafine grinding mechanism, and the ultrafine grinding mechanism is connected to the rod mill mechanism through the second self-reflux mechanism.

[0021] The rod mill mechanism is used for preliminary grinding and screening of raw coal, the coarse grinding mechanism is used for storing coal slurry, the fine grinding mechanism is used for fine grinding of coal slurry delivered by the coarse grinding mechanism, and the ultrafine grinding mechanism is used for ultrafine grinding of coal slurry. The waste recovery system is used for collecting waste coal slurry screened by the drum screen 16, and returning part of the coal slurry to the rod mill 17 for grinding through the first self-return mechanism to improve the utilization rate of the coal slurry. The first self-return mechanism and the second self-return mechanism are used to realize the reflux reprocessing of coal slurry.

[0022] The rod mill mechanism includes a rod mill 17, which can receive raw coal, grinding water and coal slurry additives in a specific proportion, and make them into coal slurry through an internal grinding mechanism. It is a key equipment for the initial processing of coal slurry. The rod mill 17 is connected to a drum screen 16, which is used to screen the coal slurry output by the rod mill 17, so that the coal slurry that meets the particle size standard enters the mill discharge trough 4, while the coarse particle coal slurry that does not pass and the overflowed coal slurry are directed to the waste slurry trough 5. The drum screen 16 is connected to the mill discharge trough 4 and the waste recovery system respectively. The mill discharge trough 4 is used to gather the coal slurry screened by the drum screen 16, and then divide it into two paths, one is sent to the low-pressure coal slurry pump 7, and then transported to the large coal slurry tank; the other is led to the slurry mixing pump 8 to prepare for the subsequent process.

[0023] The mill discharge trough 4 is connected to the low-pressure coal slurry pump 7, and the outlet of the low-pressure coal slurry pump 7 is respectively connected to the large coal slurry tank and the first coal slurry recovery pipeline 15. The low-pressure coal slurry pump 7 is used to pressurize the coal slurry of the mill discharge trough 4 and transport it to the large coal slurry tank to complete the initial transfer of the coal slurry. It is the power equipment for the coal slurry to enter the next storage link. At the same time, its outlet is connected to the coal slurry recovery pipeline, and part of the coal slurry can be returned to the inlet of the rod mill 17 as needed.

[0024] The waste material recovery system includes a waste slurry tank 5, which is connected to a waste slurry pump 6, which is connected to a first coal slurry recovery pipeline 15 of a first self-return mechanism, and the other end of the first coal slurry recovery pipeline 15 is connected to the inlet of a rod mill 17. The waste slurry tank 5 is used to collect the coal slurry overflowing from the drum screen 16 and the coarse-grained coal slurry that has not passed the screening, as a temporary storage space. The waste slurry pump 6 is used to transport the coal slurry in the waste slurry tank 5 to the inlet of the rod mill 17 through the first coal slurry recovery pipeline 15 to realize the recycling of the waste slurry.

[0025] The coarse grinding mechanism includes a coarse slurry tank 22, which is used to receive the coal slurry sent by the slurry pump 8, and dilute the coal slurry to a specific concentration by adding grinding water to meet the feeding requirements of the subsequent fine mill 19 and the ultrafine mill 20. The coarse slurry tank 22 is connected to the mill discharge trough 4, and a slurry pump 8 is provided between the coarse slurry tank 22 and the mill discharge trough 4. The slurry pump 8 is used to transport the other coal slurry separated from the mill discharge trough 4 to the coarse slurry tank 22, providing transportation power for the preparation of the coarse slurry. The outlet of the coarse slurry tank 22 is connected to a coarse slurry pump 9, which is respectively connected to the fine grinding mechanism and the ultrafine grinding mechanism. The coarse slurry pump 9 is used to transport the coal slurry with adjusted concentration in the coarse slurry tank 22 to the fine mill 19 and the ultrafine mill 20, respectively, to provide a stable material supply for further fine grinding.

[0026] The fine grinding mechanism includes a fine grinding machine 19, which is used to further grind the coal slurry sent from the coarse slurry pump 9, refine the coal slurry particles, and improve the quality of the coal slurry. The fine grinding machine 19 is connected to the coarse slurry pump 9 through a coal slurry pipeline to the fine grinding machine 19. The coal slurry pipeline to the fine grinding machine 19 is provided with a fine grinding coal slurry flowmeter 10 and a fine grinding regulating valve 11. The fine grinding coal slurry flowmeter 10 is used to monitor the flow of coal slurry entering the fine grinding machine 19 in real time, and provide accurate data for the operator to accurately control the grinding process. The fine grinding regulating valve 11 accurately controls the flow of coal slurry entering the fine grinding machine 19 by adjusting the opening according to production needs, ensuring that the grinding process in the fine grinding machine 19 is stable and efficient. The fine grinding machine 19 is connected to the ultrafine slurry tank 21, which is used to collect and mix the ultrafine slurry at the outlets of the fine grinding machine 19 and the ultrafine grinding machine 20, so as to prepare for the subsequent delivery of high-quality fine slurry to the rod mill 17.

[0027] The ultrafine grinding mechanism includes an ultrafine grinding machine 20, which is used to deeply grind the coal slurry from the coarse slurry pump 9, so that the coal slurry particles reach a near-nanometer level, greatly improving the fineness of the coal slurry to meet specific production needs. The ultrafine grinding machine 20 is connected to the coarse slurry pump 9 through a coal slurry pipeline to the ultrafine grinding machine 20, and the coal slurry pipeline to the ultrafine grinding machine 20 is provided with an ultrafine grinding coal slurry flowmeter 13 and an ultrafine grinding regulating valve 12. The ultrafine grinding coal slurry flowmeter 13 is used to monitor the flow of coal slurry entering the ultrafine grinding machine 20 in real time, provide data support for operators, and help maintain the stable operation of the ultrafine grinding machine 20. The ultrafine grinding regulating valve 12 is used to adjust the flow of coal slurry entering the ultrafine grinding machine 20 according to production requirements, and ensure that the ultrafine grinding machine 20 performs deep grinding according to the set parameters. The ultrafine mill 20 is connected to the ultrafine pulp tank 21, and the ultrafine pulp tank 21 is connected to the second self-reflux mechanism. The ultrafine pulp tank 21 is used to collect and mix the ultrafine pulp from the outlets of the fine mill 19 and the ultrafine mill 20 to prepare for the subsequent delivery of high-quality fine pulp to the rod mill 17.

[0028] The second self-return mechanism includes a second coal slurry recovery pipeline. An ultrafine slurry pump 14 is provided between the second coal slurry recovery pipeline and the ultrafine slurry tank 21. The ultrafine slurry pump 14 is used to pump the mixed fine slurry in the ultrafine slurry tank 21 into the inlet chute of the rod mill 17 and the outlet drum screen 16, respectively, so that the fine slurry and the coal slurry are fully mixed, and the fluidity and concentration of the coal slurry are optimized. The other end of the second coal slurry recovery pipeline is connected to the inlet pipeline of the rod mill 17 and the outlet pipeline of the rod mill 17, respectively. The inlet pipeline of the rod mill 17 is provided with a mill inlet flowmeter 1 and a mill inlet regulating valve 2. The mill inlet flowmeter 1 is used to accurately measure the flow of fine slurry entering the inlet of the rod mill 17, and provide real-time data for the operator to reasonably adjust the feed amount. The mill inlet regulating valve 2 is used to control the flow of fine slurry entering the inlet of the rod mill 17 by adjusting the opening according to the production process requirements, so as to ensure the stability of the grinding process in the rod mill 17. The ultrafine pulp pipeline of the rod mill 17 outlet pipeline passes through the drum screen 16 and extends into the internal outlet of the rod mill 17. The outlet pipeline of the rod mill 17 is provided with a mill outlet flow meter 3 and a mill outlet regulating valve 18. The mill outlet flow meter 3 is used to monitor the fine pulp flow entering the outlet of the rod mill 17 in real time, and provide data for the operator to timely discover and solve possible abnormal flow problems. The mill outlet regulating valve 18 is used to adjust the fine pulp flow entering the outlet of the rod mill 17 according to production needs, to ensure that the fine pulp at the outlet of the rod mill 17 is well mixed with the coal slurry.

[0029] In order to prevent the coal slurry from settling, coal slurry agitators are respectively provided in the coarse slurry tank 22, the ultrafine slurry tank 21 and the waste slurry tank 5, and the water-coal slurry is kept in a suspended state under the action of the agitators.

[0030] The present invention also provides a method for concentrating coal slurry, which uses the above-mentioned coal slurry concentrating device and comprises the following steps: Step 1: During the preparation of high-concentration coal slurry, the rod mill 17, the fine mill 19 and the ultrafine mill 20 are operated simultaneously. The waste slurry tank 5 is mainly used to recover the coal slurry that occasionally overflows. The dry basis ratio of the extracted coarse slurry to the dry basis ratio of the raw coal entering the rod mill 17 is generally controlled at 10-15% to maintain a high coal slurry concentration and good fluidity. The flow rate of the fine slurry from the ultrafine slurry tank 21 back to the inlet of the rod mill 17 is normally controlled at 1-2 cubic meters. As the steel rods of the rod mill 17 gradually wear out, it gradually increases to 3-4 cubic meters. All other fine slurries are returned to the outlet of the rod mill 17. Step 2, set the ratio of the coal slurry entering the coarse slurry tank 22 and the grinding water entering the coarse slurry tank 22, reasonably control the fine slurry concentration, control the water-slurry ratio of the coarse slurry at 0.5, add more grinding water when preparing the fine slurry, the grinding water volume at the inlet of the rod mill 17 should be less than when the fine mill 19 is not turned on, and the final coal slurry concentration sent by the low-pressure coal slurry pump 7 to the large coal slurry tank is adjusted by the grinding water volume entering the rod mill 17; Step 3: According to the fine-grind coal slurry flow rate and the ultra-fine-grind coal slurry flow rate, use the fine-grind regulating valve 11 and the ultra-fine-grind regulating valve 12 to control the ratio of the coarse slurry entering the fine mill 19 and the ultra-fine mill 20 to be 1:1-2:1, maintain the ultra-fine slurry flow rate unchanged, and adjust the fine slurry amount; Step 4: During the maintenance of the fine mill 19 or the ultrafine mill 20, a small amount of coal slurry at the outlet of the low-pressure coal slurry pump 7 is sent back to the inlet of the rod mill 17 for circulation. Through secondary grinding, the concentration of the coal slurry is kept from being reduced too much.

[0031] Therefore, the present invention adopts the above-mentioned coal slurry concentration device and concentration method, and forms a three-peak particle size grading relationship through the cooperation of a rod mill, a fine mill and an ultrafine mill. After adding nano-scale ultrafine particles, the original particle size distribution is made more reasonable. The ultrafine particles not only fill the gaps as a medium, but also coat the surface of the coarse particles, increasing the hydrophilicity of the surface of the coarse coal particles, playing a role of lubrication and drag reduction, thereby improving the fluidity and stability of the coal slurry and further increasing the concentration of the coal slurry.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A coal slurry concentration device, characterized in that: The invention comprises a mill grading system and a self-reflow system, wherein the self-reflow system comprises a first self-reflow mechanism and a second self-reflow mechanism, the mill grading system comprises a rod mill mechanism, a coarse grinding mechanism, a fine grinding mechanism and an ultrafine grinding mechanism, the outlet of the rod mill mechanism is connected to the inlet of the waste recovery system, the outlet of the waste recovery system is connected to the inlet of the rod mill mechanism through the first self-reflow mechanism, the waste recovery system is connected to the coarse grinding mechanism, the coarse grinding mechanism is connected to the fine grinding mechanism, the fine grinding mechanism is connected to the ultrafine grinding mechanism, and the ultrafine grinding mechanism is connected to the rod mill mechanism through the second self-reflow mechanism.

2. A coal slurry concentration device according to claim 1, characterized in that: The rod mill mechanism comprises a rod mill, the rod mill is connected to a drum screen, the drum screen is respectively connected to a mill discharge trough and a waste recovery system, the waste recovery system comprises a waste pulp trough, and the waste pulp trough is connected to a waste pulp pump.

3. A coal slurry concentration device according to claim 2, characterized in that: The coarse grinding mechanism comprises a coarse pulp trough, which is connected to the mill discharge trough. A pulp pump is arranged between the coarse pulp trough and the mill discharge trough. The outlet of the coarse pulp trough is connected to the coarse pulp pump, which is respectively connected to the fine grinding mechanism and the ultrafine grinding mechanism.

4. A coal slurry concentration device according to claim 3, characterized in that: The fine grinding mechanism includes a fine grinding machine, which is connected to the coarse pulp pump through a coal slurry pipeline to the fine grinding machine. The coal slurry pipeline to the fine grinding machine is provided with a fine grinding coal slurry flowmeter and a fine grinding regulating valve. The fine grinding machine is connected to the superfine pulp tank.

5. A coal slurry concentration device according to claim 3, characterized in that: The ultrafine grinding mechanism includes an ultrafine grinding machine, which is connected to the coarse slurry pump through a coal slurry pipeline to the ultrafine grinding machine. The coal slurry pipeline to the ultrafine grinding machine is provided with an ultrafine grinding coal slurry flowmeter and an ultrafine grinding regulating valve. The ultrafine grinding machine is connected to an ultrafine slurry tank, and the ultrafine slurry tank is connected to a second self-reflux mechanism.

6. A coal slurry concentration device according to claim 5, characterized in that: The second self-reflux mechanism includes a second coal slurry recovery pipeline, an ultrafine slurry pump is provided between the second coal slurry recovery pipeline and the ultrafine slurry tank, the other end of the second coal slurry recovery pipeline is respectively connected to the rod-removing mill inlet pipeline and the rod-removing mill outlet pipeline, a mill inlet flowmeter and a mill inlet regulating valve are provided on the rod-removing mill inlet pipeline, and a mill outlet flowmeter and a mill outlet regulating valve are provided on the rod-removing mill outlet pipeline.

7. A coal slurry concentration device according to claim 6, characterized in that: The ultrafine pulp pipeline to the rod mill outlet pipeline passes through the drum screen and extends into the inner outlet of the rod mill.

8. A coal slurry concentration device according to claim 3, characterized in that: The waste slurry pump is connected to the first coal slurry recovery pipeline of the first self-reflux mechanism, and the other end of the first coal slurry recovery pipeline is connected to the inlet of the rod mill.

9. A coal slurry concentration device according to claim 8, characterized in that: The mill discharge trough is connected to the low-pressure coal slurry pump, and the outlet of the low-pressure coal slurry pump is respectively connected to the large coal slurry tank and the first coal slurry recovery pipeline.

10. A method for concentrating coal slurry, characterized in that: A coal slurry concentration device according to any one of claims 1 to 9 is used, comprising the following steps: Step 1: During the preparation of high-concentration coal slurry, the rod mill, fine mill and ultrafine mill are operated simultaneously. The waste slurry tank is used to recover the coal slurry that occasionally overflows. The dry basis ratio of the extracted coarse slurry to the dry basis ratio of the raw coal entering the rod mill is controlled at 0.1:1-0.15:

1. The flow rate of the fine slurry from the ultrafine slurry tank back to the rod mill inlet is normally controlled at 1-2 cubic meters. As the steel rods of the rod mill gradually wear, it gradually increases to 3-4 cubic meters. All other fine slurries are returned to the rod mill outlet. Step 2: Set the ratio of coal slurry entering the coarse slurry tank to grinding water entering the coarse slurry tank, reasonably control the fine slurry concentration, control the water-slurry ratio of the coarse slurry at 0.5:1, add more grinding water when making fine slurry, the grinding water volume at the rod mill inlet should be less than when the fine mill is not turned on, and the final coal slurry concentration of the low-pressure coal slurry pumped into the large coal slurry tank is adjusted by the grinding water volume entering the rod mill; Step 3: According to the fine-grind coal slurry flow rate and the ultra-fine-grind coal slurry flow rate, use the fine-grind regulating valve and the ultra-fine-grind regulating valve to control the ratio of the coarse slurry entering the fine mill and the ultra-fine mill to 1:1-2:1, maintain the ultra-fine slurry flow rate unchanged, and adjust the fine slurry amount; Step 4: During the maintenance of the fine mill or ultrafine mill, a small amount of coal slurry from the outlet of the low-pressure coal slurry pump is sent back to the inlet of the rod mill for circulation. Through secondary grinding, the concentration of the coal slurry is kept from being reduced too much.

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