System for the production of chemi-mechanical pulp for papermaking

Abstract

This application provides a system for preparing chemimechanical pulp for papermaking, comprising a dewatering tank, a low-consistency refiner, a screening tank, and a pressure screen connected in series. The pressure screen feeds qualified pulp into a multi-disc thickener for dewatering and concentration. The coarse fiber residue from the screen is discharged into a pulp refiner, then into a pulp screen, and finally into a desander. The desander removes heavy impurities such as sand and gravel. The qualified pulp is fed back via two separate return lines: a first return line and a second return line. The first return line returns the pulp to the dewatering tank, and the second return line returns it to the screening tank. This preparation system provides an optimized pipeline return process, dividing the desandered pulp into two separate return lines: one line retains a small amount for return to the dewatering tank, while the other, a newly added line, directly returns the pulp to the screening tank, skipping the repeated grinding process in the low-consistency refiner. This simultaneously solves four major production problems: desander overload and wear, fiber loss, system operating condition fluctuations, and pulp backflow.

Description

Technical Field

[0001] This application relates to the technical field of papermaking chemimechanical pulp production process, specifically to a preparation system for papermaking chemimechanical pulp. Background Technology

[0002] Please see Figure 1 , Figure 1 This is a flow chart of a conventional mechanical pulp production line. The slurry treatment process of the conventional mechanical pulp production line is as follows: submersion elimination tank → low-consistency mill → screening tank → pressure screen; coarse slurry from the pressure screen enters the slurry mill → slurry screen; good slurry from the slurry screen is sent to the front end of the multi-disc thickener, and the slurry enters the No. 1 desander; part of the good slurry from the No. 1 desander is returned to the submersion elimination tank, and part is returned to the No. 1 desander itself; the heavy sand impurities in the desander system are discharged outside the No. 3 desander.

[0003] The defects of the above process are as follows: (1) The sand separator repeatedly circulates, resulting in high equipment load and reduced sand removal efficiency. The qualified slurry separated by the No. 1 desander is partially returned to its own feed end, where it is mixed again with the sandy coarse slag from the slurry sieve and then enters the desander for secondary centrifugal separation. A large amount of sand-free slurry is repeatedly passed through the desander, which greatly increases the operating load of the desander and the conveying pump. The sand concentration in the slurry continues to rise, interfering with the centrifugal classification effect. The fiber flow rate inside the No. 3 desander is disordered, and a large number of intact long fibers are discharged with the underflow sand and slag, resulting in a decrease in slurry yield.

[0004] (2) The sand separator cone is severely worn, resulting in high spare parts maintenance costs. Repeated slurry circulation causes sand and gravel inside the desander to continuously scour the cone and bushing, resulting in rapid equipment wear, short replacement cycles, the need to purchase a large number of wear-resistant spare parts every year, high downtime for maintenance, and reduced effective production time.

[0005] (3) Repeated grinding of long fibers results in poor pulp quality and high raw material loss. The desanded pulp returned to the desanding tank needs to be ground again by a low-consistency mill. The whole long fibers are excessively cut, and the average fiber length decreases. The fine fiber component increases, the fiber loss in the multi-disc thickener filtrate increases, the consumption of wood chip raw materials increases, and the tear strength and tensile strength of the paper decrease.

[0006] (4) The system operating conditions fluctuate greatly, and backflow of slurry and slag is prone to occur. All the sand-removed pulp is centrally returned to the desander tank, causing fluctuations in the flow rate and concentration of the pulp entering the low-consistency mill, which affects the screening effect of the pressure screen in the later stage. When the sand remover is shut down for maintenance, the high sand content pulp residue in the pipeline is prone to backflow into the turbid filtrate tank, which mixes into the finished pulp and generates a large number of fiber bundles, directly affecting the production of high-end paper. Summary of the Invention

[0007] This application provides a system for preparing chemimechanical pulp for papermaking. The system includes a dewatering tank, a low-consistency refiner, a screening tank, and a pressure screen connected in series. The pressure screen sends qualified pulp to a multi-disc thickener for dewatering and concentration. The coarse fiber residue from the screen is discharged into the pulp refiner. After passing through the pulp refiner, the pulp enters the pulp screen and then a desander. The desander discharges heavy impurities such as sand and gravel. The qualified pulp is provided with two separate return pipelines: a first return pipeline and a second return pipeline. The first return pipeline returns to the dewatering tank, and the second return pipeline returns to the screening tank.

[0008] In some optional embodiments, the first return line and the second return line are respectively provided with a first return valve and a second return valve, which are used to control the flow rate of the first return line and the second return line, respectively.

[0009] In some alternative embodiments, the opening ratio of the first reflux valve and the second reflux valve is 0.4:0.6, thereby making the flow ratio of the first reflux line and the second reflux line 0.4:0.6.

[0010] In some optional embodiments, the opening degree of both the first reflux valve and the second reflux valve is not less than 50%.

[0011] In some optional embodiments, a level transmitter is provided in the screening tank, which controls the second reflux valve to close or reduce its opening when the level transmitter exceeds the level threshold.

[0012] In some optional embodiments, the liquid level threshold is 90%.

[0013] In some optional embodiments, the qualified good slurry return concentration of the desander is 1.0% to 2.2%.

[0014] In some alternative embodiments, the preparation system further includes a slurry concentration adjustment tank for connection to at least one of the desander and the multi-disc thickener, for adjusting the slurry concentration.

[0015] In some optional embodiments, an unground slurry tank is provided between the pressure screen and the slurry mill, the unground slurry tank being used to buffer the unground slurry.

[0016] In some alternative embodiments, the desander comprises a plurality of desanders connected in series, with the first desander located at the uppermost end connected to the first return pipeline, the second return pipeline, and the slurry screen.

[0017] The papermaking chemimechanical pulp preparation system provided in this application addresses the technical pain points of traditional chemimechanical pulp desanding and circulation processes, such as high equipment wear, high energy consumption, excessive fiber cutting, low pulp yield, fiber bundles in the finished pulp, and unstable system operation. It offers a pipeline diversion and recirculation optimization process, eliminating the desander's self-circulation loop for good pulp and dividing the desanded good pulp into two diversion recirculation paths: one path retains a small amount for recirculation to the recirculation tank, while the other path, through a newly added pipeline, directly recirculates to the screening pulp tank, skipping the repeated grinding process in the low-consistency mill. With the addition of level interlocking and valve opening ratio control, short-circuit staged recirculation is achieved, simultaneously solving four major production problems: desander overload wear, fiber loss, system operating condition fluctuations, and pulp backflow. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flow chart of a conventional mechanical pulp production line; Figure 2 This is a schematic diagram of an embodiment of the papermaking chemimechanical pulp preparation system of this application; Figure 3 This is a schematic diagram of another embodiment of the papermaking chemimechanical pulp preparation system of this application. Detailed Implementation

[0020] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the application. Similarly, the following embodiments are only some, not all, embodiments of the present application, and all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present application.

[0021] The terms "first," "second," and "third" used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movement of components in a specific posture (as shown in the figures). If the specific posture changes, the directional indication will also change accordingly. The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to these processes, methods, products, or devices.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] This application provides a system for preparing chemimechanical pulp for papermaking, applicable to the slurry treatment and sand removal / purification section modification of wood chip chemimechanical pulp, CTMP, and BCTMP pulping production lines. Please refer to... Figure 2 , Figure 2 This is a schematic diagram of an embodiment of the papermaking chemimechanical pulp preparation system of this application. The preparation system includes a de-mineralization tank 101, a low-consistency refiner 102, a screening tank 103, and a pressure screen 104 connected in series. The chemimechanical pulp is refined and bleached, then sent to the de-mineralization tank 101 for de-mineralization. After de-mineralization, the pulp is pumped to the low-consistency refiner 102 for primary refining. The refined pulp enters the screening tank 103 for buffering and homogenization. After stabilizing the concentration and flow rate, it is then sent to the pressure screen 104 for grading and screening.

[0024] The pressure screen 104 sends qualified pulp to the multi-disc thickener 105 for dewatering and thickening, and discharges the coarse residue fibers from the screen into the pulp refiner 106. The pressure screen 104 has two discharge paths: one is to screen out qualified pulp and send it to the multi-disc thickener 105 for dewatering and thickening. After thickening, the pulp is transported to the pulp storage tower 182 by the medium-consistency pump 181 and supplied to the downstream papermaking process.

[0025] After passing through the slurry mill 106, the slurry enters the slurry screen 107. The slurry undergoing secondary grinding in the mill 106 is then fed into the slurry screen 107 for grading. The slurry screen 107 has two outputs: one is fine slurry, which is directly returned to the feed end of the multi-disc thickener 105 and combined with the good slurry from the pressure screen 104 for thickening; the other output goes to the desander 108 for centrifugal sand removal and purification. The desander 108 discharges heavy impurities such as sand and gravel. The qualified slurry is fed through two separate return lines: a first return line 109 and a second return line 110. The first return line 109 returns the slurry to the anti-submersion tank 101, and the second return line 110 returns it to the screening tank 103, achieving a short-circuit separation.

[0026] Specifically, a first return valve 111 and a second return valve 112 are respectively provided on the first return line 109 and the second return line 110. The first return valve 111 and the second return valve 112 are used to control the flow rate of the first return line 109 and the second return line 110 respectively.

[0027] The concentration of the reflux slurry in the first reflux pipeline 109 and the second reflux pipeline 110 is uniformly controlled between 1.0% and 2.2%, matching the concentration of the slurry output from the low-consistency mill, thus avoiding fluctuations in the concentration of the screening slurry tank. The outlet concentration of the screening slurry tank 103 is stable at 4.0-4.2%.

[0028] Optionally, the preparation system in this embodiment further includes a slurry concentration regulating tank 114, which is connected to at least one of the desander 108 and the multi-disc thickener 105 to regulate the slurry concentration. The slurry concentration regulating tank 114 is also used to recover the filtrate from the multi-disc thickener 105. Specifically, the slurry concentration regulating tank 114 may include a turbid filtrate tank and a clear filtrate tank (not shown in the figure).

[0029] Optionally, in this embodiment, the flow rate of the first return line 109 is less than the flow rate of the second return line 110. In a specific embodiment, the opening ratio of the first return valve 111 and the second return valve 112 is 0.4:0.6, thereby making the flow rate ratio of the first return line 109 and the second return line 110 0.4:0.6. This stabilizes the two return flow rates and balances the load on the submersion elimination tank 101 with the feed rate of the entire screening system.

[0030] The opening degree of the first return valve 111 and the second return valve 112 is not less than 50%, which avoids valve blockage and also takes into account the maximum flow rate of the valve (the requirements of the pump in the whole system will be correspondingly increased if the flow rate of the valve is too large or the pipeline is too thick).

[0031] Alternatively, please continue reading Figure 2In this embodiment, a level transmitter 113 is installed in the screening slurry tank 103. When the level transmitter 113 exceeds the level threshold, it controls the second return valve 112 to close or reduce its opening to prevent slurry overflow. In an optional embodiment, the level threshold can be 90%. When the level is ≥90%, the second return valve 112 leading from the desander to the screening slurry tank is automatically closed or reduced, while the first return valve 111 is opened wider, so that all good slurry is temporarily returned to the submersion elimination tank 101 to prevent slurry overflow from the screening slurry tank 103. The level transmitter 113, the first return valve 111, and the second return valve 112 can be linked for control. The first return valve 111 and the second return valve 112 can be pneumatic valves or solenoid valves, etc., without specific limitations.

[0032] The core difference between the conventional technical solution and the process in the embodiments of this application is as follows: Traditional process: desanded good slurry → desander self-circulation + full return submersion elimination tank → low-consistency mill → screening tank (long circulation, repeated desanding + repeated milling double loss). In comparison, the process of this invention is: canceling self-circulation, desanded good slurry diverted → submersion elimination tank + screening tank; the slurry entering the screening tank directly enters the pressure screen, skipping the low-consistency mill, eliminating secondary grinding loss.

[0033] The papermaking chemimechanical pulp preparation system provided in this application addresses the technical pain points of traditional chemimechanical pulp desanding and circulation processes, such as high equipment wear, high energy consumption, excessive fiber cutting, low pulp yield, fiber bundles in the finished pulp, and unstable system operation. It offers a pipeline diversion and recirculation optimization process, eliminating the desander's self-circulation loop for good pulp and dividing the desanded good pulp into two diversion recirculation paths: one path retains a small amount for recirculation to the recirculation tank, while the other path, through a newly added pipeline, directly recirculates to the screening pulp tank, skipping the repeated grinding process in the low-consistency mill. With the addition of level interlocking and valve opening ratio control, short-circuit staged recirculation is achieved, simultaneously solving four major production problems: desander overload wear, fiber loss, system operating condition fluctuations, and pulp backflow.

[0034] Please see Figure 3 , Figure 3 This is a schematic diagram of another embodiment of the papermaking chemimechanical pulp preparation system of this application. The preparation system includes a de-mineralization tank 101, a low-consistency refiner 102, a screening tank 103, and a pressure screen 104 connected in series. The chemimechanical pulp is refined and bleached, then sent to the de-mineralization tank 101 to complete the de-mineralization process. After de-mineralization, the pulp is pumped to the low-consistency refiner 102 for primary refining. The refined pulp enters the screening tank 103 for buffering and homogenization. After stabilizing the concentration and flow rate, it is then sent to the pressure screen 104 for grading and screening.

[0035] In this embodiment, pressure screen 104 sends qualified pulp to multi-disc thickener 105 for dewatering and concentration. After concentration, the pulp is transported to storage tower 182 by medium-consistency pump 181 and supplied to the downstream papermaking process. Unlike the previous embodiment, in this embodiment, pressure screen 104 first sends the pulp (i.e., the coarse pulp fibers screened out) to unground pulp tank 115. The function of unground pulp tank 115 is to buffer and stabilize the flow of unground pulp, preventing the pulp discharged directly from pressure screen 104 into pulp refiner 106 and causing impact to pulp refiner 106.

[0036] After passing through the slurry mill 106, the slurry enters the slurry screen 107. The slurry undergoing secondary grinding in the mill 106 is then fed into the slurry screen 107 for grading. The slurry screen 107 has two outputs: one is fine slurry, which is directly returned to the feed end of the multi-disc thickener 105 and combined with the good slurry from the pressure screen 104 for thickening; the other output goes to the desander 108 for centrifugal sand removal and purification. The desander 108 discharges heavy impurities such as sand and gravel. The qualified slurry is fed through two separate return lines: a first return line 109 and a second return line 110. The first return line 109 returns the slurry to the anti-submersion tank 101, and the second return line 110 returns it to the screening tank 103, achieving a short-circuit separation.

[0037] Unlike the previous embodiments, the sand separator 108 in this embodiment includes multiple separators connected in series (for example, after passing through sand separator #1, sand separator #2, and sand separator #3 in sequence, heavy impurities and sand are discharged, completing the thorough separation of sand and gravel). The first sand separator located at the uppermost end is connected to the first return pipeline 109, the second return pipeline 110, and the slurry screen 107. Setting multiple sand separators in series can achieve more thorough sand removal.

[0038] Similarly, in this embodiment, the first return line 109 and the second return line 110 are respectively provided with a first return valve 111 and a second return valve 112, which are used to control the flow rate of the first return line 109 and the second return line 110 respectively.

[0039] The concentration of the reflux slurry in the first reflux pipeline 109 and the second reflux pipeline 110 is uniformly controlled between 1.0% and 2.2%, matching the concentration of the slurry output from the low-consistency mill, thus avoiding fluctuations in the concentration of the screening slurry tank. The outlet concentration of the screening slurry tank 103 is stable at 4.0-4.2%.

[0040] Optionally, the preparation system in this embodiment further includes a slurry concentration regulating tank 114, which is connected to at least one of the desander 108 and the multi-disc thickener 105 to regulate the slurry concentration. The slurry concentration regulating tank 114 is also used to recover the filtrate from the multi-disc thickener 105. Specifically, the slurry concentration regulating tank 114 may include a turbid filtrate tank and a clear filtrate tank (not shown in the figure).

[0041] Optionally, in this embodiment, the flow rate of the first return line 109 is less than the flow rate of the second return line 110. In a specific embodiment, the opening ratio of the first return valve 111 and the second return valve 112 is 0.4:0.6, thereby making the flow rate ratio of the first return line 109 and the second return line 110 0.4:0.6. This stabilizes the two return flow rates and balances the load on the submersion elimination tank 101 with the feed rate of the entire screening system.

[0042] The opening degree of the first return valve 111 and the second return valve 112 is not less than 50%, which avoids valve blockage and also takes into account the maximum flow rate of the valve (the requirements of the pump in the whole system will be correspondingly increased if the flow rate of the valve is too large or the pipeline is too thick).

[0043] Alternatively, please continue reading Figure 3 In this embodiment, a level transmitter 113 can also be installed in the screening slurry tank 103. When the level transmitter 113 exceeds the level threshold, it controls the second return valve 112 to close or reduce its opening to prevent slurry overflow. In an optional embodiment, the level threshold can be 90%. When the level is ≥90%, the second return valve 112 leading from the desander to the screening slurry tank is automatically closed or reduced, while the first return valve 111 is opened wider, so that all good slurry is temporarily returned to the submersion tank 101 to prevent slurry overflow from the screening slurry tank 103. The level transmitter 113, the first return valve 111, and the second return valve 112 can be linked for control. The first return valve 111 and the second return valve 112 can be pneumatic valves or solenoid valves, etc., without specific limitations.

[0044] Taking the 540,000-ton-per-year BCTMP chemimechanical pulp production line of this factory as an example, the operating conditions before the transformation were as follows: the traditional double recirculation process was adopted, with self-circulation of desanded and good pulp + full recirculation of the submersion elimination tank; the power consumption of pulping per ton was 739 kWh, the pulp yield was 84.8%, the average length of pulp fibers was 0.74 mm, one set of desander cones was replaced every month, the pressure screen was cleaned once a week on average, and the fiber bundle of the finished pulp was >0.1%.

[0045] The modification and construction work in this embodiment is as follows: The self-circulating pipeline from the No. 1 desander to its own feed pump was dismantled; a DN300 return pipeline (with the same diameter as the pipe to the descaling tank) was laid to connect the No. 1 desander's good pulp outlet to the screening pulp tank; electric regulating valves were installed on each of the two return pipelines; a liquid level interlock control system was added to the screening pulp tank, setting the valve opening ratio to 0.4:0.6 with all valve openings not less than 50%; the screening pulp tank liquid level was automatically cut off to the screening pulp tank return flow at 90%. Stable operation control parameters included: return pulp concentration of 1.6%, and screening pulp tank pump outlet concentration stable at 4.0-4.2% optimal screening conditions. Actual measured data after the modification: pulping power consumption per ton of pulp decreased to 721 kWh, pulp yield increased to 85.1%, and the average fiber length of the pulp was 0.76 mm; the desander cone replacement cycle was extended to 3 months, the pressure screen rotor cleaning cycle was extended to 30 days, and the finished pulp fiber bundle content met the high-end paper production standards.

[0046] Compared to before the renovation, the beneficial effects of the renovation are as follows: 1. Reduce equipment wear and tear, significantly reducing spare parts maintenance costs. The elimination of the self-circulation of good slurry in the desander avoids repeated flushing of the desander cone and bushing with sandless good slurry, increasing the service life of the wear-resistant parts of the desander by 50%; the total amount of slurry fed into the low-concentration mill is reduced, the wear rate of the grinding discs decreases by 20%, and the frequency of spare parts procurement and downtime maintenance is significantly reduced.

[0047] 2. Reduce energy consumption across the entire production line. ① By skipping the secondary grinding in the low-concentration mill, the power consumption for grinding ton of pulp is reduced by approximately 18 kWh; ② Eliminating ineffective self-circulation of the desander reduces the load on the slurry conveying pump and lowers auxiliary power energy consumption; ③ The system operates stably, the frequency of pressure screen blockage and cleaning is reduced, and the consumption of auxiliary cleaning water and power is reduced simultaneously.

[0048] 3. Protects intact fibers, improving pulp yield and paper quality. The good pulp diverted to the screening pulp tank no longer undergoes low-consistency milling, long fibers are prevented from being excessively cut, and the average fiber length of the pulp increases by 1% to 3%; the loss of fine fibers is reduced, and the overall pulp yield increases by 0.2% to 0.3%; after the modification, backflow of pulp residue during machine shutdown is eliminated, and the fiber bundle content of the pulp is reduced by 9.5%, which can meet the production indicators of high-end packaging paper and cultural paper.

[0049] 4. Stabilize the entire system's operating conditions The large-capacity buffer tank of the screening tank absorbs and diverts the slurry, ensuring that the slurry concentration and flow rate at the pressure screen are uniform and stable. The output of slurry from the main pressure screen is reduced by 10%, the load of secondary slurry treatment is reduced, and the fluctuation of the entire screening and sand removal system is greatly reduced.

[0050] 5. The modification is simple, highly versatile, and yields significant economic benefits. No new grinding, sand removal, or screening core equipment is required. Only a reflux pipeline, electric regulating valves, and level gauges need to be added. The system can be modified online with short-term shutdown without affecting continuous production. It is compatible with all CTMP / BCTMP chemimechanical pulp production lines. The modification investment is low and the payback period is short. A single 540,000-ton-per-year chemimechanical pulp (BCTMP) production line can save more than 3 million yuan in raw material, electricity, and spare parts costs annually.

[0051] The above description is only a part of the embodiments of this application and does not limit the scope of protection of this application. Any equivalent device or equivalent process transformation made based on the content of this application specification and drawings, or direct or indirect application in other related technical fields, are similarly included in the patent protection scope of this application.

Claims

1. A system for preparing chemimechanical pulp for papermaking, characterized in that, The preparation system includes a submersion elimination tank, a low-consistency refiner, a screening tank, and a pressure screen connected in series. The pressure screen sends qualified pulp to a multi-disc thickener for dewatering and concentration. The coarse slag fibers separated from the screen are discharged into the slurry refiner. After passing through the slurry refiner, the pulp enters the slurry screen and then enters the desander. The desander discharges heavy impurities such as sand and gravel. The qualified pulp is provided with two branch return pipelines, namely a first return pipeline and a second return pipeline. The first return pipeline returns to the submersion elimination tank, and the second return pipeline returns to the screening tank.

2. The preparation system according to claim 1, characterized in that, The first return line and the second return line are respectively equipped with a first return valve and a second return valve, which are used to control the flow rate of the first return line and the second return line, respectively.

3. The preparation system according to claim 2, characterized in that, The opening ratio of the first reflux valve and the second reflux valve is 0.4:0.6, thereby making the flow ratio of the first reflux line and the second reflux line 0.4:0.

6.

4. The preparation system according to claim 2, characterized in that, The opening degree of both the first reflux valve and the second reflux valve is not less than 50%.

5. The preparation system according to claim 3, characterized in that, A level transmitter is installed in the screening tank. When the level transmitter exceeds the level threshold, it controls the second reflux valve to close or reduce its opening.

6. The preparation system according to claim 5, characterized in that, The liquid level threshold is 90%.

7. The preparation system according to claim 1, characterized in that, The qualified slurry return concentration of the desander is 1.0%~2.2%.

8. The preparation system according to claim 7, characterized in that, The preparation system further includes a slurry concentration regulating tank, which is connected to at least one of the desander and the multi-disc thickener for adjusting the slurry concentration.

9. The preparation system according to claim 1, characterized in that, An unground slurry tank is also provided between the pressure screen and the slurry grinding mill, and the unground slurry tank is used to buffer the unground slurry.

10. The preparation system according to claim 1, characterized in that, The desanders include multiple desanders connected in series, with the first desander located at the uppermost end connected to the first return pipeline, the second return pipeline, and the slurry screen.

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