Lignin separation device and separation method for pulping black liquor

Abstract

The invention relates to the technical field of pulping and papermaking waste liquid treatment, in particular to a pulping black liquor lignin separation device and a separation method. Comprising a shell, a black liquor inlet is formed in the upper left portion of the shell, and a concentrated liquor outlet is formed in the lower right portion of the shell; the membrane tube is located in the shell and used for filtering the black liquor, one end of the membrane tube is closed, and the other end of the membrane tube is open; the spiral blade is arranged between the membrane tube and the shell in a surrounding mode, the first rotating shaft is fixedly arranged at one end of the spiral blade, and the second rotating shaft is arranged at the other end of the spiral blade. According to the dynamic rotational flow membrane filtering device, the spiral blade is arranged on the outer surface of the membrane and is driven by the external rotating shaft to rotate around the membrane tube, so that the concentration polarization phenomenon can be effectively reduced by the generated shearing force. When black liquor rotationally flows in a spiral channel formed by the spiral blades, large-particle pollutants are far away from the surface of the membrane under the centrifugal action, so that primary separation is realized, and the occurrence of membrane pollution is remarkably slowed down.

Description

Technical Field

[0001] The invention relates to the technical field of pulping and papermaking waste liquid treatment, and in particular to a pulping black liquor lignin separation device and a separation method. Background Art

[0002] The papermaking industry is an indispensable part of the global economy, and its rapid development is accompanied by a large amount of wastewater discharge. Among them, the waste liquid generated in the cooking stage of the pulping process, black liquor, accounts for about 90% of the total wastewater pollutants, becoming the main source of pollution in papermaking waste liquid. Black liquor is rich in a large amount of lignin and its derivatives. As an organic compound second only to cellulose in content, lignin is a renewable energy source with large reserves, wide distribution and carbon neutrality. It is also the only non-petroleum resource in nature that can provide renewable aromatic compounds. However, due to the natural resistance of lignin to chemical and biological transformation, the direct utilization efficiency is low. Therefore, how to efficiently and low-lossly separate lignin and realize its high-value utilization has become a research hotspot in the field of biomass refining at home and abroad.

[0003] The efficient separation and conversion of lignin is a prerequisite for the production and processing of high-value-added biomass-based materials, and is crucial to promoting the development of biomass refining technology. Membrane separation technology stands out among various separation methods due to its high efficiency and energy saving, no phase change, no pollution, and simple operation. However, membrane separation technology has encountered some challenges when applied to black liquor treatment. Due to the high viscosity and poor fluidity of black liquor, concentration polarization and membrane fouling are particularly prominent, which limits the application of membrane separation technology in the separation of lignin from black liquor and makes it difficult to meet the needs of continuous production.

[0004] In order to solve the above problems, researchers have proposed a variety of methods to mitigate membrane fouling, including membrane modification, material pretreatment, additional field enhancement, and increasing fluid flow instability. Specifically:

[0005] Membrane modification: It can only change the membrane flux in the initial stage of filtration. Once the membrane pores are blocked, the effect of membrane modification will disappear.

[0006] Material pretreatment: Although it can reduce membrane pollution, it will destroy the lignin structure and is not conducive to the development of subsequent products.

[0007] Additional field enhancement: requires that all components of the material have the same electrical properties and potentials of the same magnitude, and its application range is limited.

[0008] Increasing fluid flow instability: As a green and efficient method to mitigate membrane fouling, it reduces material deposition on the membrane surface by increasing the turbulence of the fluid.

[0009] Initially, membrane separation used dead-end filtration, that is, the direction of fluid flow was perpendicular to the membrane surface. This method would cause the retained lignin to gradually accumulate on the membrane surface to form a filter cake, which would eventually completely block the membrane pores. In order to improve this situation, cross-flow filtration was proposed, that is, to make the fluid flow direction parallel to the membrane surface, and to use the shear force generated by the fluid's own flow to reduce the accumulation of retained matter. However, cross-flow filtration has a limitation, that is, the shear force and filtration pressure affect each other. When a larger filtration pressure is required, the flow rate of the suspension must be reduced, resulting in a weakening of the shear force.

[0010] On this basis, the dynamic cross-flow filtration device introduces a rotating component, which generates a higher flow rate on the membrane surface through the movement of the rotating component to increase the shear force, solving the problem of the mutual influence of shear force and filtration pressure. However, the action range of the rotating blades is limited to the membrane surface, and it is impossible to discharge the intercepted material and its concentrate in time, and it is still difficult to meet the standards of continuous production. Summary of the invention

[0011] The present invention provides a pulping black liquor lignin separation device and a separation method, and its purpose is to provide a dynamic cyclone membrane filtration device, which utilizes the centrifugal force generated by the cyclone to increase the flow rate of the fluid on the membrane surface and improve the shear force, thereby slowing down the concentration polarization phenomenon in the membrane filtration process, better reducing membrane pollution, achieving a thin layer or even no filter cake phenomenon, and efficiently and losslessly separating black liquor lignin to avoid environmental pollution.

[0012] To achieve the above object, the technical solution of the present invention is:

[0013] A pulping black liquor lignin separation device comprises: a shell, wherein the upper left part of the shell is provided with a black liquor feed inlet, and the lower right part of the shell is provided with a concentrated liquid discharge outlet;

[0014] A membrane tube, located inside the shell, for filtering black liquor, wherein one end of the membrane tube is closed and the other end is open;

[0015] The spiral blade is disposed between the membrane tube and the housing, the first rotating shaft is fixedly disposed at one end of the spiral blade, and the second rotating shaft is disposed at the other end of the spiral blade, and generates shear force and centrifugal action through rotation to reduce membrane pollution and promote large particle pollutants to stay away from the membrane surface;

[0016] Bearing 1 is used to support rotating shaft 1, and bearing 2 is used to support rotating shaft 2 to ensure stable rotation;

[0017] End cover and bolts secure the right side of the housing and allow removal for replacement of internal parts.

[0018] Furthermore, the rotating shaft 1 is a sliding bearing on the housing and is provided with a dynamic sealing structure to prevent leakage of black liquid.

[0019] Furthermore, the pitch of the spiral blade is 15-20 mm.

[0020] Furthermore, a membrane tube sleeve is arranged on the left side of the membrane tube, and the membrane tube sleeve is connected to the rotating shaft one through the bearing three to ensure the rigidity of the membrane tube; the right side of the membrane tube is fixed by the end cover and sealed with the membrane tube sealing ring.

[0021] Furthermore, the membrane tube sleeve has an inner wall stepped structure, which is used to position the membrane tube and the bearing three.

[0022] Furthermore, a clear liquid discharge port is provided on the end cover for discharging the filtered clear liquid.

[0023] Furthermore, the device also includes at least one end cover sealing ring for enhancing the sealing between the shell and the end cover.

[0024] A method, the method is based on a black liquor lignin separation device, the method comprising the following steps:

[0025] Introducing pulping black liquor containing lignin from the black liquor feed port of the shell;

[0026] The black liquor is made to rotate and flow in the spiral channel formed by the spiral blades, and the large particles of pollutants are separated by centrifugal force;

[0027] The spiral blades are driven to rotate by the rotating shaft to generate shear force to reduce the concentration polarization and prevent membrane fouling.

[0028] The filtered clear liquid flows out from the clear liquid outlet of the membrane tube, and the concentrated liquid is discharged from the concentrated liquid outlet of the shell.

[0029] Furthermore, the method includes regularly disassembling the end cover, inspecting and / or replacing internal parts to maintain the good operating condition of the device.

[0030] Furthermore, the rotation speed of the spiral blade is 200-800 rpm.

[0031] The beneficial effects achieved by the present invention are:

[0032] The invention discloses a pulping black liquor lignin separation device and a separation method. The dynamic cyclone membrane filtration device is provided with spiral blades on the outer surface of the membrane, and uses an external rotating shaft to drive the spiral blades to rotate around the membrane tube, and the generated shear force can effectively reduce the concentration polarization phenomenon. When the black liquor rotates and flows in the spiral channel formed by the spiral blades, the centrifugal effect makes the large particle pollutants stay away from the membrane surface, achieving preliminary separation, thereby significantly slowing down the occurrence of membrane pollution.

[0033] The invention discloses a pulping black liquor lignin separation device and separation method. Due to the shear force and centrifugal effect generated by the spiral blades, the retained matter is difficult to accumulate on the membrane surface, thus avoiding the filter cake phenomenon commonly seen in traditional filtering methods. This not only improves the filtering efficiency, but also prolongs the service life of the membrane and reduces the maintenance cost.

[0034] The invention discloses a pulping black liquor lignin separation device and separation method. The rotating motion of the spiral blade not only generates shear force, but also can clean the outer surface of the membrane tube to prevent the concentrated liquid from being deposited in the filtering device. This design ensures the long-term stable operation of the device and reduces the time and frequency of shutdown maintenance.

[0035] The invention discloses a pulping black liquor lignin separation device and separation method. Compared with traditional dead-end filtration and cross-flow filtration, the dynamic cyclone membrane filtration device can work continuously without interrupting production. The driving force and centrifugal action of the spiral blades enable the concentrated liquid and large particle pollutants to be discharged in time, ensuring the continuity and high efficiency of production.

[0036] The invention discloses a pulping black liquor lignin separation device and separation method. The overall structure of the device is compact, and the outer shell and the end cover are connected by bolts, which is convenient for disassembly and replacement of internal parts. This design not only simplifies the maintenance process, but also reduces the maintenance cost and prolongs the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0038] Figure 1 It is a schematic diagram of the working principle of the patented device of the present invention;

[0039] Figure 2 It is a cross-sectional view of the overall structure of the patented device of the present invention;

[0040] Figure 3 It is a schematic diagram of the overall structure of the patented device of the present invention;

[0041] Figure 4 This is a structural diagram of the rotating shaft and spiral blades in the patented device of the present invention;

[0042] In the figure, 1. outer shell; 2. spiral blade; 3. end cover sealing ring; 4. membrane tube sealing ring; 5. end cover; 6. bolt; 7. membrane tube casing; 8. rotating shaft one; 9. bearing one; 10. rotating shaft two; 11. membrane tube; 12. bearing two; 13. feed inlet; 14. discharge outlet; 15. clear liquid discharge outlet; 16. dynamic sealing structure; 17. bearing three.

[0043] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0046] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if the meaning of "and / or" appearing in the full text is to include three parallel solutions, taking "A and / or B" as an example, it includes solution A, or solution B, or a solution that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0047] like Figure 1As shown, the schematic diagram of the principle of dynamic cyclone membrane filtration uses a tubular ceramic membrane, and a shell 1 is set on the outer surface of the membrane. The upper left interface of the shell 1 is a black liquor feed port 13, and the lower right interface of the shell 1 is a concentrated liquid discharge port 14. The filtered clear liquid flows out through the tubular ceramic membrane. A spiral blade 2 is installed between the shell 1 and the membrane tube 11. The external rotating shaft 8 drives the spiral blade 2 to rotate around the membrane tube 11. The shear force generated retains the advantages of the dynamic cross-flow rotating blade to generate shear force to reduce the concentration polarization degree, prevent membrane pollution, and achieve thin layer or even cake-free layer filtration. In addition, the black liquor of the dynamic cyclone method rotates in the spiral channel formed by the spiral blade 2. The centrifugal action makes the large particle pollutants away from the membrane surface to achieve preliminary separation, thereby slowing down the membrane pollution. The rotating flow fluid can be used to achieve real-time cleaning of the pollution on the outer surface of the membrane tube 11. The driving force generated by the spiral blade 2 can also prevent the deposition of the concentrated liquid in the filtration device.

[0048] like Figure 2 As shown, the dynamic cyclone membrane filtration device includes: a housing 1, a spiral blade 2, an end cover sealing ring 3, a membrane tube sealing ring 4, an end cover 5, a bolt 6, a membrane tube sleeve 7, a rotating shaft 1 8, a bearing 1 9, a dynamic sealing structure 16, a membrane tube 11, a bearing 2 12 and a rotating shaft 2 10. A black liquor suspension feed port 13 is provided at the upper left corner of the housing 1, and a black liquor concentrate discharge port 14 is provided at the lower right corner. The spiral blade 2 is placed between the housing 1 and the membrane tube 11, surrounding the membrane tube 11 and filling the entire chamber. The external electric device drives the spiral blade 2 to rotate through the rotating shaft. The plane of the left end of the rotating shaft is parallel to the plane of the left end of the housing 1. A dynamic sealing device is used to seal and reduce friction and prevent black liquor leakage. The right end of the rotating shaft 8 is connected to the housing 1 by a bearing 1 9. The bearing 1 9 is integrally formed with the housing 1. The bearing 1 9 is a sliding bearing, and a dynamic sealing structure 16 is provided on the bearing 1 9. The left end of the membrane tube 11 is sealed, and a membrane tube sleeve 7 is provided on the left side of the membrane tube 11. The membrane tube sleeve 7 is connected to the rotating shaft 8 through a bearing 3 17 to maintain the rigidity of the membrane tube 11. The right end of the membrane tube 11 is fixed by an end cap 5 and sealed with a membrane tube sealing ring 4. The end cap 5 is provided with a clear liquid discharge port 15 to facilitate the timely discharge of the filtered clear liquid.

[0049] like Figure 3 As shown, the right side of the housing 1 and the end cover 5 are connected by four bolts 6, which is convenient for disassembly and replacement of internal parts. The end cover 5 is provided with a clear liquid discharge port 15. As shown in the figure, the two ends of the spiral blade 2 are fixedly connected to the rotating shaft 1 8 and the rotating shaft 2 10 respectively.

[0050] like Figures 1 to 4 As shown, a pulping black liquor lignin separation device includes: a shell 1, a membrane tube 11, a spiral blade 2, a rotating shaft, a bearing, an end cover 5 and a bolt 6.

[0051] The housing 1 is provided with a black liquor feed port 13 on the upper left and a concentrated liquid discharge port 14 on the lower right; the housing 1 is the main container of the entire device, and the housing 1 not only provides a closed space to accommodate the black liquor and internal components, but also protects and supports other structural elements. It is provided with a black liquor feed port 13 on the upper left for introducing the black liquor to be treated; and a concentrated liquid discharge port 14 on the lower right for discharging the concentrated liquid containing high concentration of lignin and other macromolecular substances after separation. Corrosion-resistant and high-strength materials such as stainless steel or Teflon-coated metal are usually selected to resist the erosion of chemicals in the black liquor and ensure long-term stable operation.

[0052] The membrane tube 11 is located inside the housing 1 and is used to filter the black liquor. One end of the membrane tube 11 is closed and the other end is open.

[0053] The spiral blade 2 is disposed around the membrane tube 11 and the housing 1, one end of which is connected to the rotating shaft 1 8 and the other end is connected to the rotating shaft 2 10. The spiral blade 2 generates shear force and centrifugal action through rotation to reduce membrane pollution and promote large particle pollutants to stay away from the membrane surface. When the rotating shaft 1 8 drives the spiral blade 2 to rotate, shear force and centrifugal action are generated on the outer surface of the membrane tube 11. This can not only effectively reduce the concentration polarization phenomenon, but also keep large particle pollutants in the black liquor away from the membrane surface, thereby slowing down the occurrence of membrane pollution.

[0054] The design of the spiral blade 2 needs to consider its shape, angle and spacing to optimize the effects of shear force and centrifugal force, while ensuring sufficient channel space for smooth flow of black liquor. The pitch of the spiral blade 2 is determined according to the size of the device, and the pitch is preferably 15-20 mm.

[0055] The end cover 5 and the bolts 6 are used to fix the right side of the housing 1 and allow disassembly for replacement of internal parts.

[0056] The end cover 5 is connected to the housing 1 by bolts 6, which plays a role of fixing and sealing. The end cover 5 is provided with a clear liquid discharge port 15 for discharging the clear liquid filtered by the membrane tube 11. The design of the bolts 6 makes the end cover 5 easy to disassemble, and it is convenient to inspect, clean and replace the internal parts.

[0057] The spiral channel formed by the spiral blades 2 allows the black liquor to flow in a rotational manner, and utilizes the centrifugal effect to move large particle pollutants away from the membrane surface, thereby alleviating membrane pollution.

[0058] A dynamic sealing structure 16 is provided between the rotating shaft 8 and the bearing 9 to prevent leakage of black liquid.

[0059] The dynamic seal structure 16 is installed between the rotating shaft 8 and the bearing 9 to prevent the black liquid from leaking from the contact point between the rotating shaft and the housing 1. The bearing 9 is an integral structure on the housing 1. It can maintain good sealing performance when the rotating shaft rotates at high speed, ensuring the safety and reliability of the system.

[0060] A membrane tube sleeve 7 is arranged on the left side of the membrane tube 11, and the membrane tube sleeve 7 is connected to the rotating shaft 1 8 through the bearing 3 17 to ensure the rigidity of the membrane tube 11; the right side of the membrane tube 11 is fixed by the end cover 5 and sealed with the membrane tube sealing ring 4.

[0061] The membrane tube sleeve 7 is used to support the left side of the membrane tube to ensure its rigidity and stability; the bearing three 17 is used to support the rotating shaft 8 to ensure its smooth rotation. The two work together to ensure the stability and reliability of the membrane tube 11 and the rotating shaft 8 when rotating at high speed.

[0062] The membrane tube 11 is the core component for black liquor filtration, and is made of tubular ceramic membrane or other high-efficiency membrane materials. The membrane tube 11 has the characteristics of high flux and chemical corrosion resistance, and can effectively separate small molecules (such as water and other soluble components) and macromolecules (such as lignin) in the black liquor. The filtered clear liquid flows out from the inner wall of the membrane tube 11, while the concentrated liquid flows downward along the outer wall of the membrane tube 11.

[0063] The two sealing rings, the end cover sealing ring 3 and the membrane tube sealing ring 4, are used to enhance the sealing between the housing 1 and the end cover 5 and the sealing between the membrane tube 11 and the shaft bearing. They are made of high-performance elastomer materials and can maintain good sealing performance under high pressure environments, prevent black liquid leakage, and ensure the normal operation of the system. The sealing ring is a wearing part and needs to be checked and replaced regularly to maintain the sealing and safety of the system.

[0064] The device further comprises at least one end cover sealing ring 3 for enhancing the sealing between the housing 1 and the end cover 5 .

[0065] A method, based on a black liquor lignin separation device, comprises the following steps:

[0066] Pulping black liquor containing lignin is introduced from the black liquor feed port 13 of the housing 1 .

[0067] The black liquor is made to rotate and flow in the spiral channel formed by the spiral blades 2, and the large particle pollutants are separated by centrifugal force.

[0068] The spiral blade 2 is driven to rotate by the rotating shaft to generate shear force to reduce the concentration polarization degree and prevent membrane pollution; the rotation speed of the spiral blade 2 is preferably -800 rpm.

[0069] The filtered clear liquid flows out from the clear liquid outlet 15 of the membrane tube 11 , while the concentrated liquid is discharged from the concentrated liquid outlet 14 of the housing 1 .

[0070] The method includes regularly disassembling the end cover 5 and inspecting and / or replacing internal parts to maintain the device in good operating condition.

[0071] Specifically, the pulping black liquor to be treated is pumped into the device from the black liquor feed port 13 of the outer shell 1. The external electric device is started to drive the rotating shaft and the spiral blade 2 to rotate, so that the black liquor forms a high-speed rotating flow in the spiral channel. Due to the effect of centrifugal force, larger particulate matter is thrown to a position away from the membrane surface, reducing the pollution of the membrane surface. Small molecular substances such as water and other soluble components in the black liquor pass through the wall of the membrane tube 11 to become clear liquid, and flow out from the clear liquid outlet 15 on the end cover 5 for collection. The concentrated black liquor (including macromolecular substances that have not passed through the membrane, such as lignin) flows downward along the inner wall of the outer shell 1 and is finally discharged from the concentrated liquid outlet 14. During the whole process, the spiral blade 2 continues to rotate, which not only helps to maintain a high shear force, but also prevents the sedimentation of the concentrated liquid in the device, ensuring continuous production.

[0072] The above descriptions are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A pulping black liquor lignin separation device, characterized in that: include: A housing (1), wherein the housing (1) is provided with a black liquor feed inlet (13) at the upper left and a concentrated liquid discharge outlet (14) at the lower right; A membrane tube (11) is located inside the housing (1) and is used to filter the black liquor; one end of the membrane tube (11) is closed and the other end is open; A spiral blade (2) is disposed around the membrane tube (11) and the housing (1), a first rotating shaft (8) is fixedly disposed at one end of the spiral blade (2), and a second rotating shaft (10) is disposed at the other end of the spiral blade (2), and generates shear force and centrifugal action through rotation to reduce membrane pollution and promote large particle pollutants to stay away from the membrane surface; Bearing 1 (9) is used to support rotating shaft 1 (8), and bearing 2 (12) is used to support rotating shaft 2 (10) to ensure stable rotation; The end cover (5) and bolts (6) are used to fix the right side of the housing (1) and allow disassembly for replacement of internal parts.

2. The pulping black liquor lignin separation device according to claim 1, characterized in that: The rotating shaft 1 (8) is a sliding bearing on the housing (1) and is provided with a dynamic sealing structure (16) to prevent leakage of black liquid.

3. The pulping black liquor lignin separation device according to claim 1, characterized in that: The pitch of the spiral blade (2) is 15-20 mm.

4. The pulping black liquor lignin separation device according to claim 1, characterized in that: A membrane tube sleeve (7) is arranged on the left side of the membrane tube (11), and the membrane tube sleeve (7) is connected to the rotating shaft (8) through the bearing three (17) to ensure the rigidity of the membrane tube (11); the right side of the membrane tube (11) is fixed by the end cover (5) and sealed by the membrane tube sealing ring (4).

5. The pulping black liquor lignin separation device according to claim 4, characterized in that: The membrane tube sleeve (7) has a stepped inner wall structure and is used to position the membrane tube (11) and the bearing three (17).

6. The pulping black liquor lignin separation device according to claim 1, characterized in that: The end cover (5) is provided with a clear liquid discharge port (15) for discharging the filtered clear liquid.

7. The pulping black liquor lignin separation device according to claim 1, characterized in that: The device further comprises at least one end cover sealing ring (3) for enhancing the sealing performance between the housing (1) and the end cover (5).

8. A separation method, characterized in that: The method is based on the device according to any one of claims 1 to 7, and the method comprises the following steps: Introducing pulping black liquor containing lignin from the black liquor feed port (13) of the housing (1); The black liquor is caused to rotate and flow in the spiral channel formed by the spiral blades (2), and large particles of pollutants are separated by centrifugal force; The spiral blade (2) is driven to rotate by the rotating shaft to generate shear force to reduce the concentration polarization degree and prevent membrane fouling; The filtered clear liquid flows out from the clear liquid outlet (15) of the membrane tube (11), while the concentrated liquid is discharged from the concentrated liquid outlet (14) of the housing (1).

9. The separation method according to claim 8, characterized in that: The method comprises regularly disassembling the end cover (5) and inspecting and / or replacing internal parts to maintain the good operating condition of the device.

10. The separation method according to claim 8, characterized in that: The rotation speed of the spiral blade (2) is 200-800 rpm.

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