Method and system for recovering and removing water from a polyolefin powder

Abstract

The present application relates to the technical field of dust recovery, and discloses a method and system for recovering and dehydrating polyolefin powder, which comprises the following steps: (1) centrifuging and separating the polyolefin powder to obtain treated powder a; (2) flash evaporating the powder a under ultrasonic vibration; and (3) infrared drying the powder obtained in step (2); wherein the flash evaporation temperature is greater than the melting temperature of the powder a, and the difference between the two is 5-20 DEG C. The method provided by the present application has high drying efficiency for polyolefin powder, significantly improves the dehydration rate, effectively avoids the risk of combustion and explosion caused by dust raising, effectively avoids the problem of dust combustion and explosion in the subsequent system when the dust is finally discharged in a molten state, and has high operability.

Description

Technical Field

[0001] This invention relates to the field of dust recovery technology, specifically to a method and system for recovering and removing water from polyolefin powder. Background Technology

[0002] Thermoplastic resins prepared from polyolefins have low density, are water and corrosion resistant, have high mechanical strength, and good insulation properties. They are widely used in films, plastic equipment, wires and cables, etc. Polyolefins are mainly thermoplastic resins obtained by the individual polymerization and copolymerization of olefins such as ethylene, propylene, octene, and hexene, as well as certain cyclic olefins.

[0003] Polyolefins are mainly prepared by low-pressure polymerization and high-pressure polymerization. In the process, olefins polymerize in a reactor and then enter the granulation system in a thermoplastic molten state. The granulation system primarily uses extrusion to press the molten polyolefin into a mold, where a bottom cutter cuts it into uniformly sized polyolefin particles. This pelletizing process generates a large amount of dust, which can easily clog mold holes and inlet / outlet valves, causing granulator malfunctions and preventing pelletizing from being completed. Industrial production often involves the recycling of polyolefin dust to improve yield. However, dust re-entrainment during dust recycling can easily lead to dust explosions. Therefore, effective and proper dehydration, drying, and recycling of polyolefin dust is crucial for safe production in the polyolefin industry. Currently, hot-fluid drying is the main method used in industry to dry polyolefin dust; however, this method easily generates dust, posing a high risk of dust explosions, and also has low dehydration efficiency and poor dehydration effect. Therefore, it is imperative to propose an effective dust drying method, improve the utilization and recycling rate of polyolefin dust, and effectively reduce the potential explosion risk of dust. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of low dehydration efficiency and easy dust explosion accidents caused by existing polyolefin dust drying methods. This invention provides a method and system for polyolefin powder recycling and dehydration. This method has high drying efficiency for polyolefin dust, significantly improves the dehydration rate, effectively avoids the risk of combustion and explosion caused by dust in various systems, and is highly operable.

[0005] To achieve the above objectives, the present invention provides a method for recovering and dewatering polyolefin powder, the method comprising the following steps:

[0006] (1) The polyolefin powder is centrifuged and separated to obtain the treated powder a;

[0007] (2) Under ultrasonic vibration conditions, the powder a is flash-evaporated;

[0008] (3) The powder obtained in step (2) is dried by infrared drying;

[0009] The flash temperature is greater than the melting temperature of powder a, and the difference between the two is 5 to 20°C.

[0010] Preferably, in step (1), the particle size range of the polyolefin powder is 1 to 2000 μm.

[0011] Preferably, in step (1), the centrifugation conditions include: centrifugation time of 30 to 90 minutes and centrifugation rate of 2500 to 3000 r / min.

[0012] Preferably, in step (1), the separation method is static separation.

[0013] Preferably, the settling time is 60–120 minutes.

[0014] Preferably, step (1) includes: centrifuging the polyolefin powder, then letting it stand for 60 to 120 minutes, and then draining the water to obtain the treated powder a;

[0015] Preferably, the drainage rate is 5–10 mL / min.

[0016] Preferably, the drainage rate is 60-90% during drainage.

[0017] Preferably, step (2) is carried out in a high-temperature flash evaporation device, and the vacuum degree of the high-temperature flash evaporation device is maintained at -0.02 to -0.09 MPa.

[0018] Preferably, in step (2), the ultrasonic vibration frequency is 30-50 kHz.

[0019] Preferably, in step (2), the ultrasonic power used for ultrasonic vibration is 800 to 1200 W.

[0020] Preferably, in step (3), the infrared drying temperature is 90–150°C.

[0021] A second aspect of the present invention provides a system for recovering and removing water from polyolefin powder, the system comprising:

[0022] A centrifugal device is used to centrifuge the powder.

[0023] A separating device is used to allow the powder from the centrifuge to stand and separate into powder a;

[0024] A high-temperature flash evaporation device is provided, wherein an ultrasonic vibration tank is provided in the high-temperature flash evaporation device, so that the powder a from the liquid separation device is flashed under ultrasonic vibration.

[0025] An infrared dryer is used to perform infrared drying on powders from the high-temperature flash evaporation device.

[0026] The flash temperature is greater than the melting temperature of powder a, and the difference between the two is 5 to 20°C.

[0027] Preferably, the system further includes a vacuum pump connected to the high-temperature flash evaporation device for controlling the vacuum level within the high-temperature flash evaporation device.

[0028] Preferably, the system further includes a booster compressor for conveying the powder in the high-temperature flash evaporation device to the infrared dryer.

[0029] Preferably, the system further includes a storage device for storing powder from the infrared dryer.

[0030] In the method provided by this invention, polyolefin powder (containing water-laden dust) is first centrifuged and then allowed to stand to allow the dust to float. Moisture below the dust interface is separated based on the dust's location. The resulting powder (a) is then placed in a flash evaporator, with the flash temperature controlled slightly higher than the melting temperature of powder (a). Under ultrasonic vibration, the moisture in the dust is rapidly flash-evaporated and discharged. After sufficient moisture has been evaporated, the molten dust is subjected to infrared drying to remove residual moisture from its surface. This method offers high drying efficiency for polyolefin powder, significantly improves dehydration rate, effectively avoids the risk of combustion and explosion caused by dust, and the final discharge of the dust in a molten state also effectively avoids dust combustion and explosion problems in subsequent systems. It is also highly operable. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating a specific embodiment of the polyolefin powder recycling and dewatering system provided by the present invention.

[0032] Explanation of reference numerals in the attached figures

[0033] 10-Centrifuge device; 11-First drain outlet; 20-Separation device; 21-Second drain outlet; 30-High temperature flash evaporation device; 31-Ultrasonic vibration tank; 40-Infrared dryer; 50-Vacuum pump; 60-Booster; 70-Storage device. Detailed Implementation

[0034] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] In industrial production, polyolefin products enter the granulation unit in a molten state after polymerization. During the granulation process, a large amount of micron-sized powder is generated. This powder can cause blockage of pipes and valves, and there is also a risk of dust explosion due to dust generation.

[0037] In view of this, the present invention provides a method for the recovery and dehydration of polyolefin powder, aiming to solve the problem of dust drying, dehydration, and recovery generated after underwater granulation and pelletizing of polyolefin products, and at the same time fundamentally solve the potential risk of dust explosion in subsequent systems. In this invention, the method includes the following steps:

[0038] (1) The polyolefin powder is centrifuged and separated to obtain the treated powder a;

[0039] (2) Under ultrasonic vibration conditions, the powder a is flash-evaporated;

[0040] (3) The powder obtained in step (2) is dried by infrared drying;

[0041] The flash temperature is greater than the melting temperature of powder a, and the difference between the two is 5 to 20°C.

[0042] In this invention, by controlling the flash temperature to be 5 to 20°C higher than the melting temperature of powder a, and by controlling the difference between the flash temperature and the melting temperature of powder a within the above range, powder a can form a small-scale molten state, making it easy for moisture to evaporate, resulting in good drying effect, while avoiding the risk of combustion and explosion.

[0043] The method provided by this invention achieves rapid dehydration by employing dust melting accompanied by flash evaporation. Simultaneously, melting the powder avoids the risk of dust explosion in subsequent processes (such as dust recovery units and bag filters). This method offers high drying efficiency for polyolefin dust, significantly improving dehydration rates and effectively preventing the risk of explosion caused by dust generation within various systems. It is highly operable. Furthermore, the molten polyolefin dust can be recycled to the granulation system, significantly increasing the yield of polyolefin products.

[0044] This invention does not limit the specific source of the polyolefin powder, as long as it is a water-containing polyolefin powder. In a specific embodiment, the source of the polyolefin powder is: the water-containing dust generated after the polyolefin product is granulated by a water-jetting granulator is the polyolefin powder, and the generated granules are discharged into the granulation tank.

[0045] In specific implementations, the type of polyolefin powder can be polyethylene, polypropylene, polybutene, etc.

[0046] In a specific implementation, the template size of the water-cutting granulator is Φ800mm, the granulator speed is 0~200r / min, and the template hole diameter is Φ1.8mm.

[0047] More specifically, the water-cutting granulator has 25 to 30 cutters.

[0048] In a preferred embodiment, in step (1), the particle size range of the polyolefin powder is 1–2000 μm, more preferably 300–1000 μm. It is understood that when the particle size of the original polyolefin powder is outside the above range, sieving can be used to bring the particle size of the polyolefin powder to be processed within the above range.

[0049] In order to better separate the dust and water, in the preferred embodiment, the centrifugation conditions in step (1) include: centrifugation time of 30 to 90 min and centrifugation rate of 2500 to 3000 r / min.

[0050] In a specific implementation, in step (1), the liquid separation method is static liquid separation, wherein the static time is 60 to 120 minutes. During the above static time, the layers can be further separated to ensure that the dust floats to the upper part of the water surface, and then the water is drained to achieve liquid separation and obtain powder a.

[0051] In one specific embodiment, step (1) includes: centrifuging the polyolefin powder, then letting it stand for 60 to 120 minutes, and then draining the water through interface control to obtain the treated powder a.

[0052] In one specific embodiment, the centrifugation and settling separation steps in step (1) can be carried out in a centrifuge device. That is, step (1) specifically includes: centrifuging the polyolefin powder in a centrifuge device, then settling it for 60 to 120 minutes to separate it into layers, and then draining the water to obtain the processed powder a.

[0053] Since the centrifugation and separation process in this invention has good stability, in another specific embodiment, the centrifugation and settling separation in step (1) can be carried out in different devices, so as to achieve continuous operation. The centrifugation is carried out in a centrifugation device and the settling separation is carried out in a settling device. That is, step (1) includes: centrifuging the polyolefin powder in a centrifugation device, then settling for 60 to 120 minutes, and then draining the water to obtain the processed powder a.

[0054] In a preferred embodiment, during the separation and drainage process, the drainage rate is controlled at 5–10 mL / min.

[0055] In a preferred embodiment, during the static separation and drainage, the drainage rate is 60-90%, wherein the drainage rate is determined by a level gauge installed on the centrifuge device and / or the separation device.

[0056] More preferably, during the settling and separation of liquids and drainage, the drainage rate is 80-85%. Within this range, as much drainage is possible, reducing the time required for subsequent drying, while minimizing dust loss due to excessive drainage.

[0057] In this article, "flash evaporation" refers to the phenomenon where a high-pressure saturated liquid enters a relatively low-pressure container, and due to the sudden drop in pressure, the saturated liquid transforms into a portion of the saturated vapor and saturated liquid at the container pressure. In a specific embodiment, step (2) is carried out in a high-temperature flash evaporation device, and the vacuum degree of the high-temperature flash evaporation device is maintained at -0.02 to -0.09 MPa, preferably -0.04 to -0.07 MPa.

[0058] In the method described in this invention, in step (2), powder a is moved by ultrasonic vibration, thereby improving the drying effect. In a specific embodiment, an ultrasonic vibration tank is set in the high-temperature flash evaporation device so that powder a is flashed under ultrasonic vibration.

[0059] In a preferred embodiment, in step (2), the ultrasonic vibration frequency is 30 to 50 kHz, specifically, for example, 30 kHz, 35 kHz, 38 kHz, 40 kHz, 42 kHz, 45 kHz or 50 kHz.

[0060] In a preferred embodiment, in step (2), the ultrasonic power used for ultrasonic vibration is 800 to 1200W, specifically, for example, 800W, 900W, 950W, 1000W, 1100W or 1200W.

[0061] In the method described in this invention, step (3) is performed in an infrared dryer.

[0062] In the method described in this invention, the molten powder obtained in step (2) is discharged into the subsequent infrared dryer during the pressurization process of the pressurizer, wherein the pressure of the pressurizer to discharge the molten material is 20-30 MPa.

[0063] In the method described in this invention, in step (3), the moisture on the surface of the molten polyolefin powder is dried by infrared drying. In a specific embodiment, in step (3), the infrared drying temperature is 90–150°C, preferably 110–120°C.

[0064] In a specific implementation, in step (3), the length of the polyolefin melt conveyor belt is 15-25m, the conveyor belt running speed is 0.1-0.3m / s, and the infrared lamp power is 24kW.

[0065] The method provided by this invention is applicable to the dehydration and drying of almost all types of polyolefin dust. The powder is recovered in a molten state and can be recycled back to the granulator for granulation.

[0066] This invention also proposes a system for recovering and removing water from polyolefin powder, please refer to the following: Figure 1 The system includes:

[0067] Centrifuge device 10, in which the powder is centrifuged;

[0068] Separating device 20 is used to separate the powder from the centrifuge device 10 by allowing it to stand and separate to obtain powder a;

[0069] A high-temperature flash evaporation device 30 is provided, wherein an ultrasonic vibration tank 31 is provided in the high-temperature flash evaporation device 30, so that the powder a from the liquid separation device 20 is flashed under ultrasonic vibration.

[0070] Infrared dryer 40 is used to perform infrared drying on powder from the high-temperature flash evaporation device 30;

[0071] The flash temperature is greater than the melting temperature of powder a, and the difference between the two is 5 to 20°C.

[0072] In this invention, the water-containing polyolefin powder first enters the centrifuge device 10 for centrifugation and stratification, and then enters the liquid separation device 20 to stand for the dust to float. The water in the lower part of the dust is separated according to the dust interface. The resulting powder a then enters the high-temperature flash evaporation device 30, where the flash evaporation temperature is controlled to be slightly higher than the melting temperature of the dust, and a pressure reduction system is provided to quickly flash evaporate and discharge the water in the dust under ultrasonic vibration. After the water in the dust has been fully evaporated, the molten dust is introduced into the infrared dryer 40 under the action of the booster 60 to dry the residual water on the surface of the molten dust, thereby recovering the dried molten polyolefin powder.

[0073] In the system described in this invention, the powder is centrifuged in the centrifuge device 10 and then separated into liquids in the liquid separator 20. In this way, the centrifuge device 10 can continue to centrifuge the next batch of powder, thereby realizing continuous operation and improving dehydration efficiency.

[0074] In a specific embodiment, the centrifugation device 10 is a centrifuge tank.

[0075] In a specific embodiment, the centrifuge device 10 has first drain outlets 11 on both sides of its bottom.

[0076] In a specific embodiment, the liquid separating device 20 is a liquid separating tank. More specifically, the liquid separating tank has second drain outlets 21 on both sides of its bottom.

[0077] In this invention, by letting the powder stand in the liquid separating device 20 for 60 to 120 minutes, the powder can float in the upper part of the water surface, and then drain the water through the second drain outlet 21 at the bottom of the liquid separating device 20 to achieve liquid separation.

[0078] In a specific embodiment, the drainage rate of the liquid separating device 20 is 60-90%, preferably 80-85%.

[0079] In a specific implementation, the liquid separating device 20 is equipped with a level gauge (not shown in the figure) to determine the drainage rate by the change in liquid level.

[0080] In a specific implementation, the system further includes a vacuum pump 50, which is connected to the high-temperature flash evaporation device 30 and is used to control the vacuum level inside the high-temperature flash evaporation device 30, thereby maintaining the high-temperature flash evaporation device 30 at a suitable vacuum level.

[0081] In a specific embodiment, the system further includes a booster compressor 60, which is used to transport the powder in the high-temperature flash evaporation device 30 to the infrared dryer 40.

[0082] In a specific implementation, the high-temperature flash evaporation device 30 is a high-temperature flash evaporation tank.

[0083] In a specific implementation, the infrared dryer 40 is an infrared drying tank.

[0084] In this invention, molten powder from the high-temperature flash evaporation device 30 enters the infrared dryer 40 in the form of a mesh belt, and is dried by infrared lamps. In a preferred embodiment, the mesh belt length is 15-25m, the mesh belt speed is 0.1-0.3m / s, and the infrared lamp power is 24kW.

[0085] In a specific embodiment, the system further includes a storage device 70 for storing powder from the infrared dryer 40 to achieve material recovery.

[0086] In a specific implementation, the storage device 70 is a storage tank.

[0087] In this invention, after underwater pelletizing of polyolefin products, the resulting water-containing dust first enters a centrifuge 10 for centrifugal separation, then enters a liquid separator 20 to allow the dust to float, separating the lower part of the dust based on the dust interface. Subsequently, the water-containing dust enters a high-temperature flash evaporation device 30, where the flash evaporation temperature is controlled slightly higher than the melting temperature of the dust, and a pressure-reducing system is provided to rapidly flash evaporate and discharge the moisture from the dust under ultrasonic vibration. After the moisture in the dust has been fully evaporated, the molten dust is introduced into an infrared dryer 40 under the action of a booster 60 to dry the residual moisture on the surface of the molten dust, and finally enters a storage device 70 for material recovery. The process provided by this invention has high drying efficiency for polyolefin dust, significantly improves the dehydration rate, effectively avoids the risk of combustion and explosion caused by dust, and the final discharge of the dust in a molten state also effectively avoids dust combustion and explosion problems in subsequent systems. This process can be operated continuously, further improving drying efficiency.

[0088] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available products.

[0089] In the following embodiments, the process flow adopts... Figure 1 The system shown includes: a centrifuge 10, a liquid separator 20, a high-temperature flash evaporator 30, an infrared dryer 40, a vacuum pump 50, a booster 60, and a storage device 70. The centrifuge 10 is a centrifuge tank, the liquid separator 20 is a liquid separator, the high-temperature flash evaporator 30 is a high-temperature flash evaporator, and the storage device 70 is a storage tank. The high-temperature flash evaporator 30 is equipped with an ultrasonic vibration tank 31.

[0090] Example 1

[0091] This embodiment illustrates the method and system for recovering and removing water from polyolefin powder according to the present invention.

[0092] (1) The polymerized polyolefin material (low-density polyethylene) enters a granulator for granulation. The granulator has a template size of Φ800mm, a pelletizer speed of 200r / min, and a template aperture of Φ1.8mm. The pellets are discharged into the granulation tank. The dust particles generated after sieving have a particle size range of 300μm and are used as polyolefin powder to be processed. The polyolefin powder solution then enters a centrifuge device 10 for centrifugation to ensure that the dust is evenly distributed and concentrated on the top of the solution. The centrifugation time is 30min and the centrifugation speed is 2500r / min. After centrifugation, the polyolefin powder enters a separator 20 and is allowed to stand for 60min to ensure that the dust floats in the upper part of the water surface. After standing, water is drained from the bottom edges of the separator 20 at a rate of 5mL / min. The separator 20 drains water according to the dust interface, with a drainage volume of 60%, resulting in powder a (melting temperature of 100℃).

[0093] (2) The obtained powder a is conveyed to the high temperature flash evaporation device 30. The flash evaporation temperature is 105℃. At the same time as the flash evaporation, the ultrasonic vibration is turned on. The vibration frequency is selected as 40KHz and the ultrasonic working power is 1000W. After the high temperature flash evaporation, the system water vapor is discharged under reduced pressure. The vacuum degree is -0.09MPa. After the pressure is reduced, the pressure is increased to 20MPa by the booster 60 to discharge the molten material.

[0094] (3) The molten polyolefin powder enters the infrared dryer 40 under the action of the booster 60 for infrared drying to dry the residual moisture on its surface; the infrared dryer 40 has a mesh belt length of 20m, a mesh belt running speed of 0.1m / s, an infrared lamp power of 24kW, and an infrared drying heating temperature of 90℃; finally, the dried material enters the storage device 70 for subsequent recycling and granulation.

[0095] Example 2

[0096] This embodiment illustrates the method and system for recovering and removing water from polyolefin powder according to the present invention.

[0097] (1) The polymerized polyolefin material (low-density polyethylene) enters a granulator for granulation. The granulator has a template size of Φ800mm, a pelletizer speed of 200r / min, and a template aperture of Φ1.8mm. The pellets are discharged into the granulation tank. The dust particles generated after sieving have a particle size range of 300-1000μm and are used as polyolefin powder to be processed. The polyolefin powder solution then enters a centrifuge device 10 for centrifugation to ensure that the dust is evenly distributed and concentrated on the top of the solution. The centrifugation time is 30min and the centrifugation speed is 2500r / min. After centrifugation, the polyolefin powder enters a separator 20 and is allowed to stand for 60min to ensure that the dust floats in the upper part of the water surface. After standing, water is drained from the bottom edges of the separator 20 at a rate of 5mL / min. The separator 20 drains water according to the dust interface, with a drainage volume of 80%, to obtain powder a (melting temperature of 100℃).

[0098] (2) The obtained powder a is conveyed to the high temperature flash evaporation device 30. The flash evaporation temperature is 110℃. At the same time as the flash evaporation, the ultrasonic vibration is turned on. The vibration frequency is selected as 40KHz and the ultrasonic working power is 1000W. After the high temperature flash evaporation, the system water vapor is discharged under reduced pressure. The vacuum degree is -0.07MPa. After the pressure is reduced, the pressure is increased to 20MPa by the booster 60 to discharge the molten material.

[0099] (3) The molten polyolefin powder enters the infrared dryer 40 under the action of the booster 60 for infrared drying to dry the residual moisture on its surface; the infrared dryer 40 has a mesh belt length of 20m, a mesh belt running speed of 0.1m / s, an infrared lamp power of 24kW, and an infrared drying heating temperature of 110℃; finally, the dried material enters the storage device 70 for subsequent recycling and granulation.

[0100] Example 3

[0101] This embodiment illustrates the method and system for recovering and removing water from polyolefin powder according to the present invention.

[0102] (1) The polymerized polyolefin material (low-density polyethylene) enters the granulator for granulation. The granulator has a template size of Φ800mm, a pelletizer speed of 200r / min, and a template aperture of Φ1.8mm. The pellets are discharged into the granulation tank. The dust particles generated after sieving have a particle size range of 300-1000μm and are used as polyolefin powder to be processed. The polyolefin powder solution then enters the centrifuge device 10 for centrifugation to ensure that the dust is evenly distributed and concentrated on the top of the solution. The centrifugation time is 30min and the centrifugation speed is 2500r / min. After centrifugation, the polyolefin powder enters the separator 20 and is allowed to stand for 60min to ensure that the dust floats in the upper part of the water surface. After standing, the water is drained from the bottom edges of the separator 20 at a rate of 5mL / min. The separator 20 drains water according to the dust interface, with a drainage volume of 85%, to obtain powder a (melting temperature of 100℃).

[0103] (2) The obtained powder a is conveyed to the high temperature flash evaporation device 30. The flash evaporation temperature is 120℃. At the same time as the flash evaporation, the ultrasonic vibration is turned on. The vibration frequency is selected as 40KHz and the ultrasonic working power is 1000W. After the high temperature flash evaporation, the system water vapor is discharged under reduced pressure. The vacuum degree of the reduced pressure is -0.04MPa. After the pressure is reduced, the pressure is increased to 20MPa by the booster 60 to discharge the molten material.

[0104] The polyolefin powder then enters the infrared dryer 40 for infrared drying to remove residual moisture from its surface. The infrared dryer 40 has a 20m long mesh belt, a mesh belt speed of 0.1m / s, an infrared lamp power of 24kW, and an infrared drying heating temperature of 120℃. Finally, the dried material enters the storage device 70 for subsequent recycling and granulation.

[0105] Example 4

[0106] This embodiment illustrates the method and system for recovering and removing water from polyolefin powder according to the present invention.

[0107] (1) The polymerized polyolefin material (low-density polyethylene) enters the granulator for granulation. The granulator has a template size of Φ800mm, a pelletizer speed of 200r / min, and a template aperture of Φ1.8mm. The pellets are discharged into the granulation tank. The dust particles generated after sieving have a particle size range of 1000~2000μm and are used as polyolefin powder to be processed. The polyolefin powder solution then enters the centrifuge device 10 for centrifugation to ensure that the dust is evenly distributed and concentrated on the top of the solution. The centrifugation time is 30min and the centrifugation speed is 2500r / min. After centrifugation, the polyolefin powder enters the separator 20 and is allowed to stand for 60min to ensure that the dust floats in the upper part of the water surface. After standing, the water is drained from the bottom edges of the separator 20 at a rate of 5mL / min. The separator 20 drains water according to the dust interface, with a drainage volume of 60%, to obtain powder a (melting temperature of 100℃).

[0108] (2) The obtained powder a is conveyed to the high temperature flash evaporation device 30. The flash evaporation temperature is 110℃. At the same time as the flash evaporation, the ultrasonic vibration is turned on. The vibration frequency is selected as 40KHz and the ultrasonic working power is 1000W. After the high temperature flash evaporation, the system water vapor is discharged under reduced pressure. The vacuum degree of the reduced pressure is -0.09MPa. After the pressure is reduced, the pressure is increased to 20MPa by the booster 60 to discharge the molten material.

[0109] The polyolefin powder then enters the infrared dryer 40 for infrared drying to remove residual moisture from its surface. The infrared dryer 40 has a 20m long conveyor belt, a conveyor belt speed of 0.1m / s, an infrared lamp power of 24kW, and an infrared drying heating temperature of 90℃. Finally, the dried material enters the storage device 70 for subsequent recycling and granulation.

[0110] Example 5

[0111] This embodiment illustrates the method and system for recovering and removing water from polyolefin powder according to the present invention.

[0112] (1) The polymerized polyolefin material (low-density polyethylene) enters the granulator for granulation. The granulator has a template size of Φ800mm, a pelletizer speed of 200r / min, and a template aperture of Φ1.8mm. The pellets are discharged into the granulation tank. The dust particles generated after sieving have a particle size range of 1000-2000μm and are used as polyolefin powder to be processed. The polyolefin powder solution then enters the centrifuge device 10 for centrifugation to ensure that the dust is evenly distributed and concentrated on the top of the solution. The centrifugation time is 30min and the centrifugation speed is 2500r / min. After centrifugation, the polyolefin powder enters the separator 20 and is allowed to stand for 60min to ensure that the dust floats in the upper part of the water surface. After standing, the water is drained from the bottom edges of the separator 20 at a rate of 5mL / min. The separator 20 drains water according to the dust interface, with a drainage volume of 80%, to obtain powder a (melting temperature of 100℃).

[0113] (2) The obtained powder a is conveyed to the high temperature flash evaporation device 30. The flash evaporation temperature is 110℃. At the same time as the flash evaporation, the ultrasonic vibration is turned on. The vibration frequency is selected as 40KHz and the ultrasonic working power is 1000W. After the high temperature flash evaporation, the system water vapor is discharged under reduced pressure. The vacuum degree is -0.07MPa. After the pressure is reduced, the pressure is increased to 20MPa by the booster 60 to discharge the molten material.

[0114] (3) The molten polyolefin powder enters the infrared dryer 40 under the action of the booster 60 for infrared drying to remove residual moisture from its surface; the infrared dryer 40 has a mesh belt length of 20m, a mesh belt running speed of 0.1m / s, an infrared lamp power of 24kW, and an infrared drying heating temperature of 110℃. Finally, the dried material enters the storage device 70 for subsequent recycling and granulation.

[0115] Example 6

[0116] This embodiment illustrates the method and system for recovering and removing water from polyolefin powder according to the present invention.

[0117] (1) The polymerized polyolefin material (low-density polyethylene) enters a granulator for granulation. The granulator has a template size of Φ800mm, a pelletizer speed of 200r / min, and a template aperture of Φ1.8mm. The pellets are discharged into a granulation tank. The dust particles generated after sieving have a particle size range of 1000-2000μm and are used as polyolefin powder to be processed. The polyolefin powder solution then enters a centrifuge device 10 for centrifugation to ensure that the dust is evenly distributed and concentrated on the top of the solution. The centrifugation time is 30min and the centrifugation speed is 2500r / min. After centrifugation, the polyolefin powder enters a separator 20 and is allowed to stand for 60min to ensure that the dust floats in the upper part of the water surface. After standing, water is drained from the bottom edges of the separator 20 at a rate of 5mL / min. The separator 20 drains water according to the dust interface, with a drainage volume of 85%, resulting in powder a (melting temperature of 100℃).

[0118] (2) The obtained powder a is conveyed to the high temperature flash evaporation device 30. The flash evaporation temperature is 120℃. At the same time as the flash evaporation, the ultrasonic vibration is turned on. The vibration frequency is selected as 40KHz and the ultrasonic working power is 1000W. After the high temperature flash evaporation, the system water vapor is discharged under reduced pressure. The vacuum degree of the reduced pressure is -0.02MPa. After the pressure is reduced, the pressure is increased to 20~30MPa by the booster 60 to discharge the molten material.

[0119] (3) The molten polyolefin powder enters the infrared dryer 40 under the action of the booster 60 for infrared drying to dry the residual moisture on its surface; the infrared dryer 40 has a mesh belt length of 20m, a mesh belt running speed of 0.1m / s, an infrared lamp power of 24kW, and an infrared drying heating temperature of 120℃; finally, the dried material enters the storage device 70 for subsequent recycling and granulation.

[0120] Example 7

[0121] This embodiment illustrates the method and system for recovering and removing water from polyolefin powder according to the present invention.

[0122] (1) The polymerized polyolefin material (low-density polyethylene) enters a granulator for granulation. The granulator has a template size of Φ800mm, a pelletizer speed of 200r / min, and a template aperture of Φ1.8mm. The pellets are discharged into a granulation tank. The dust particles generated after sieving have a particle size range of 300-1000μm and are used as polyolefin powder to be processed. The polyolefin powder solution then enters a centrifuge device 10 for centrifugation to ensure that the dust is evenly distributed and concentrated on the top of the solution. The centrifugation time is 30min and the centrifugation speed is 2500r / min. After centrifugation, the polyolefin powder enters a separator 20 and is allowed to stand for 60min to ensure that the dust floats in the upper part of the water surface. After standing, water is drained from the bottom edges of the separator 20 at a rate of 5mL / min. The separator 20 drains water according to the dust interface, with a drainage volume of 60%, resulting in powder a.

[0123] (2) The obtained powder a is conveyed to the high-temperature flash evaporation device 30. The flash evaporation temperature is 110℃. At the same time as the flash evaporation, ultrasonic vibration is turned on. The vibration frequency is selected as 40KHz and the ultrasonic working power is 1000W. After the high-temperature flash evaporation, the system water vapor is discharged under reduced pressure. The vacuum degree is -0.07MPa. After the pressure is reduced, the pressure is increased to 20MPa by the booster 60 to discharge the molten material (melting temperature is 100℃).

[0124] (3) The molten polyolefin powder enters the infrared dryer 40 under the action of the booster 60 for infrared drying to dry the residual moisture on its surface; the infrared dryer 40 has a mesh belt length of 20m, a mesh belt running speed of 0.1m / s, an infrared lamp power of 24kW, and an infrared drying heating temperature of 120℃; finally, the dried material enters the storage device 70 for subsequent recycling and granulation.

[0125] Example 8

[0126] This embodiment illustrates the method and system for recovering and removing water from polyolefin powder according to the present invention.

[0127] (1) The polymerized polyolefin material (low-density polyethylene) enters the granulator for granulation. The granulator has a template size of Φ800mm, a pelletizer speed of 200r / min, and a template aperture of Φ1.8mm. The pellets are discharged into the granulation tank. The dust particles generated after sieving have a particle size range of 300-1000μm and are used as polyolefin powder to be processed. The polyolefin powder solution then enters the centrifuge device 10 for centrifugation to ensure that the dust is evenly distributed and concentrated on the top of the solution. The centrifugation time is 30min and the centrifugation speed is 2500r / min. After centrifugation, the polyolefin powder enters the separator 20 and is allowed to stand for 60min to ensure that the dust floats in the upper part of the water surface. After standing, the water is drained at the bottom edges of the separator 20 at a rate of 5mL / min. The separator 20 drains water according to the dust interface, with a drainage volume of 85%, to obtain powder a (melting temperature of 100℃).

[0128] (2) The obtained powder a is conveyed to the high temperature flash evaporation device 30. The flash evaporation temperature is 110℃. At the same time as the flash evaporation, the ultrasonic vibration is turned on. The vibration frequency is selected as 40KHz and the ultrasonic working power is 1000W. After the high temperature flash evaporation, the system water vapor is discharged under reduced pressure. The vacuum degree of the reduced pressure is -0.04MPa. After the pressure is reduced, the pressure is increased to 20MPa by the booster 60 to discharge the molten material.

[0129] (3) The molten polyolefin powder enters the infrared dryer 40 under the action of the booster 60 for infrared drying to remove residual moisture from its surface. The infrared dryer 40 has a mesh belt length of 20m, a mesh belt running speed of 0.2m / s, an infrared lamp power of 24kW, and an infrared drying heating temperature of 100℃. Finally, the dried material enters the storage device 70 for subsequent recycling and granulation.

[0130] Example 9

[0131] The method described in Example 2 is implemented, except that in step (2), the flash temperature is 115°C.

[0132] Example 10

[0133] The method described in Example 2 is implemented, except that in step (2), the ultrasonic vibration frequency is 30KHz.

[0134] Comparative Example 1

[0135] The method described in Example 2 is implemented, except that ultrasonic vibration is not turned on during the high-temperature flash evaporation process in step (2).

[0136] Comparative Example 2

[0137] The method described in Example 2 is implemented, except that after high-temperature flash evaporation, the product does not pass through the infrared dryer 40 and directly enters the storage device 70.

[0138] Comparative Example 3

[0139] The method described in Example 2 is implemented, except that in step (2), the flash temperature is 140°C.

[0140] In the drying process of this comparative example, a blockage occurred during the discharge process of the high-temperature flash tank.

[0141] Comparative Example 4

[0142] The method described in Example 2 is implemented, except that in step (2), the flash temperature is 80°C.

[0143] Test case

[0144] The moisture content of the powder before and after drying in the test examples and comparative examples was determined according to GB / T 16913-2008 "Test Methods for Physical Properties of Dust". The specific procedure was as follows: Six portions of sample powder were weighed and placed in an oven for drying. The initial temperature was set at 105℃, and the drying time was 4 hours. After 4 hours, the powder was removed, cooled in a desiccator, weighed, and the percentage weight reduction was calculated. The arithmetic mean of the six parallel samples was taken as the moisture content of the powder. The test results are shown in Table 1 below. The powder before drying is the powder at the inlet of the liquid separator, and the powder after drying is the dust obtained after drying in the powder flow cooler. The test results are also shown in Table 1 below. The powder before drying is the powder at the inlet of centrifuge 10, and the powder after drying is the powder at the outlet of infrared dryer 40.

[0145] Table 1

[0146]

[0147]

[0148] As can be seen from the results in Table 1, Examples 1-10 using the method described in this invention have a high dust recovery rate and low moisture content in the dried dust, resulting in a significantly better drying effect.

[0149] Comparing Example 2 with Comparative Example 1, it can be seen that the powder obtained after treatment in Comparative Example 1 has a significantly higher moisture content. This may be because without ultrasonic vibration, the moisture trapped inside the dust cannot be fully evaporated, and the moisture cannot be fully discharged from the dust.

[0150] A comparison of Example 2 and Comparative Example 2 shows that, without treatment by an infrared dryer, the residual moisture in the dust cannot be fully removed.

[0151] Comparing Example 2 with Comparative Example 3, it can be seen that the powder obtained after treatment in Comparative Example 3 has a higher moisture content and a lower dust recovery rate. This may be because the higher flash temperature causes the powder to melt rapidly, which can easily cause blockage of the discharge valve during the discharge process, and some of the molten powder adheres to the wall, resulting in insufficient dust recovery. At the same time, the excessively fast melting process prevents the moisture in the powder from being fully discharged.

[0152] Comparing Example 2 and Comparative Example 4, it can be seen that the powder obtained after treatment in Comparative Example 4 has a higher moisture content and a lower powder recovery rate. This may be because the flash evaporation temperature is lower than the melting temperature of powder a, and water vapor is trapped in the powder and cannot be fully evaporated.

[0153] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for recycling and dewatering polyolefin powder, characterized in that, The method includes the following steps: (1) The polyolefin powder is centrifuged and separated to obtain the treated powder a; (2) Under ultrasonic vibration conditions, the powder a is flash-evaporated; (3) The powder obtained in step (2) is dried by infrared drying; The flash temperature is greater than the melting temperature of powder a, and the difference between the two is 5 to 20°C.

2. The method according to claim 1, characterized in that, In step (1), the particle size range of the polyolefin powder is 1 to 2000 μm.

3. The method according to claim 1 or 2, characterized in that, In step (1), the centrifugation conditions include: centrifugation time of 30 to 90 minutes and centrifugation rate of 2500 to 3000 r / min.

4. The method according to claim 1, characterized in that, In step (1), the separation method is static separation; Preferably, the settling time is 60–120 minutes.

5. The method according to claim 1 or 4, characterized in that, Step (1) includes: centrifuging the polyolefin powder, then letting it stand for 60-120 minutes, then draining the water to obtain the treated powder a; Preferably, the drainage rate is 5–10 mL / min. Preferably, the drainage rate is 60-90% during drainage.

6. The method according to any one of claims 1-5, characterized in that, Step (2) is carried out in a high-temperature flash evaporation device, and the vacuum degree of the high-temperature flash evaporation device is maintained at -0.02 to -0.09 MPa.

7. The method according to any one of claims 1-6, characterized in that, In step (2), the ultrasonic vibration frequency is 30-50KHz.

8. The method according to claim 1 or 7, characterized in that, In step (2), the ultrasonic power used for ultrasonic vibration is 800-1200W.

9. The method according to any one of claims 1-8, characterized in that, In step (3), the infrared drying temperature is 90–150°C.

10. A system for recovering and removing water from polyolefin powder, characterized in that, The system includes: Centrifuge device (10) is used to centrifuge the polyolefin powder; Separating device (20) is used to separate the powder from the centrifuge device (10) by allowing it to stand and separate to obtain powder a; A high-temperature flash evaporation device (30) is provided with an ultrasonic vibration tank (31) so that the powder a from the liquid separation device (20) is flashed under ultrasonic vibration. Infrared dryer (40) for infrared drying of powder from the high-temperature flash evaporation device (30); The flash temperature is greater than the melting temperature of powder a, and the difference between the two is 5 to 20°C.

11. The system according to claim 10, characterized in that, The system also includes a vacuum pump (50), which is connected to the high-temperature flash evaporation device (30) and is used to control the vacuum level inside the high-temperature flash evaporation device (30).

12. The system according to claim 10 or 11, characterized in that, The system also includes a booster (60) for conveying the powder in the high-temperature flash evaporation device (30) to the infrared dryer (40).

13. The system according to claim 10 or 11, characterized in that, The system also includes a storage device (70) for storing powder from the infrared dryer (40).

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