Drying tower for preparing low-moisture ethylene-vinyl alcohol copolymer granules

Abstract

Disclosed in the present invention is a drying tower for preparing low-moisture ethylene-vinyl alcohol copolymer granules, the drying tower comprising a head, a drying cylinder, a first conical section, a cooling pipe, a second conical section, a granule feeding pipe, a granule distributor, two gas distributors, granule discharging pipes, gas inlets, and gas outlets, wherein each of the gas distributors comprises a buffer chamber, an annular pipe, a plurality of sector-shaped pipes communicating the buffer chamber with the annular pipe, an air inlet pipe communicating the buffer chamber with the air inlet, a first flow guide hole provided on the top of the annular pipe, a second flow guide hole provided on the top of each sector-shaped pipe, and a granule overflow hole at the bottom of each sector-shaped pipe, the plurality of sector-shaped pipes being arranged between the buffer chamber and the annular pipe at equal intervals in a circumferential direction; each sector-shaped pipe gradually increases in diameter and inclines down from the buffer chamber to the annular pipe; the two gas inlets are connected to a gas generation device; under the action of the gas generation device, the gas distributors generate axial flows flowing from the first and second flow guide holes in a direction opposite to a target granule movement direction. The present invention has a good drying effect and high drying efficiency.

Description

A drying tower for preparing low-water-content ethylene-vinyl alcohol copolymer particles Technical Field

[0001] The invention relates to the technical field of chemical manufacturing, in particular to a drying tower for preparing ethylene-vinyl alcohol copolymer particles with low water content. Background Art

[0002] Ethylene-vinyl alcohol copolymer (EVOH) is composed of two comonomers, ethylene and vinyl alcohol. It combines the good processing properties of polyethylene with the excellent barrier properties of polyvinyl alcohol, and has the characteristics of high barrier properties, good moisture absorption, good heat sealing properties, and excellent mechanical properties. Its thermophysical properties, gas barrier properties, and processing properties can be adjusted with the change of the molar content of the ethylene segment. The series of products can be widely used in food or pharmaceutical packaging with a long shelf life, for the manufacture of medical selective permeable membranes, and as heating and insulation materials in the construction industry. Although EVOH has high gas barrier properties, the barrier properties of the material decrease significantly under high temperature and high humidity environments. This is because the large number of hydroxyl groups in the vinyl alcohol block easily form complex hydrogen bonds with water molecules, destroying the large number of intramolecular and intermolecular hydrogen bonds, thereby reducing the interchain cohesion and greatly reducing the gas barrier properties of the material.

[0003] The EVOH copolymer production process is similar to that of polyvinyl alcohol, including copolymerization, alcoholysis, and granulation. However, the EVOH granules after the alcoholysis process have a high internal moisture content (typically close to 10wt%), requiring drying to remove moisture from both the surface and interior of the granules. Failure to do so directly impacts subsequent extrusion processes such as blown film, and also affects the overall performance of the final product. Traditionally, wet polymer granule drying employs batch-fed vacuum drying in an intermittent operation, using an inclined vacuum drum dryer. While typically suitable for small-batch production, the resulting granules often exhibit poor uniformity, large batch variations, and low production capacity and yield.

[0004] In recent years, the domestic chemical fiber industry has developed large-scale continuous drying equipment such as polyester PET continuous solid-phase polycondensation towers and nylon 6 solid-phase drying towers. However, due to the particularity of the polymer chain structure, this type of equipment still cannot meet the production needs of low-water-content EVOH pellets, which is mainly reflected in the following aspects:

[0005] (1) The use of single-stream axial nitrogen drying results in low adjustability of parameters such as drying gas flow rate and tower temperature, resulting in a bottleneck in equipment production capacity. It also causes a high nitrogen moisture content, which increases the water vapor concentration in the tower and hinders the mass transfer of moisture on the particle surface to the gas phase. Increasing the gas flow rate will significantly increase production energy consumption.

[0006] (2) Radial airflow drying lacks gas redistribution function in the tower. When the pressure and flow rate of the hot carrier gas change, it is easy to cause uneven airflow in the drying tower, and the contact time and temperature with the particles are also different, resulting in uneven drying of the particles, affecting product uniformity.

[0007] (3) The method is suitable for drying particles with surface moisture. The surface water of the particles is removed by a long period of gas-solid two-phase countercurrent contact. However, for highly hydrophilic polymer particles, the water removal efficiency is significantly reduced. The long-term high-temperature hot carrier gas can easily cause adhesion between polymer particles, further affecting the gas-solid two-phase contact, which greatly reduces the overall drying efficiency and makes it impossible to obtain polymer particles with low water content.

[0008] (4) In the actual production process, the particles tend to flow along the wall, resulting in incomplete contact between the particles at the tower edge and the high-temperature nitrogen. In addition, the small-hole distributor commonly used easily causes the particles to block the nitrogen outlet, which reduces the drying efficiency.

[0009] Summary of the Invention

[0010] The object of the present invention is to provide a drying tower for preparing ethylene-vinyl alcohol copolymer particles with low water content, so as to meet the production demand of EVOH particles with low water content.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] A drying tower for preparing low-water-content ethylene-vinyl alcohol copolymer particles, comprising:

[0013] The main body has a cavity inside, and the main body includes a head, a drying cylinder, a first cone section, a cooling pipe and a second cone section which are connected and arranged in an integral manner from top to bottom along the height direction;

[0014] A particle feeding pipe is provided on the head, one end of the particle feeding pipe extends into the cavity, and the other end extends out of the head;

[0015] a particle distributor, disposed in the drying cylinder and connected to the particle feed pipe, for evenly distributing the target particles in the drying cylinder;

[0016] A gas distributor group is arranged in the drying cylinder and below the particle distributor, the gas distributor group includes two gas distributors, and the two gas distributors are arranged in an upper and lower spacing in the height direction;

[0017] a particle discharge pipe, which is provided on the second cone section, with one end of the particle discharge pipe extending into the cavity and the other end extending out of the second cone section;

[0018] Two gas inlets are arranged on the drying cylinder and are connected to the two gas distributors in a one-to-one manner. The gas inlets are provided with an air inlet pressure measuring port and an air inlet temperature measuring port;

[0019] and a gas outlet, which is provided on the head and communicates with the cavity, and is provided with an outlet temperature measuring port and an outlet pressure measuring port;

[0020] The gas distributor includes a buffer chamber, an annular tube sleeved outside the buffer chamber, a plurality of fan-shaped tubes connecting the buffer chamber and the annular tube, an air inlet tube connecting the buffer chamber and the corresponding gas inlet, a plurality of first guide holes provided at the top of the annular tube, a plurality of second guide holes provided at the top of the fan-shaped tube, and a particle overflow hole provided at the bottom of the fan-shaped tube, wherein the plurality of fan-shaped tubes are arranged at equal intervals along the circumferential direction between the buffer chamber and the annular tube;

[0021] From the buffer chamber to the annular tube, the diameter of the fan-shaped tube gradually increases, and the fan-shaped tube is arranged to be tilted downward, the particle overflow hole is arranged close to the annular tube, and the diameter of the annular tube is adapted to the inner diameter of the drying cylinder;

[0022] The two gas inlets are connected one-to-one with a gas generating device, and the gas generating device is used to generate dry hot carrier gas. The gas distributor is suitable for generating axial airflow flowing out from the first guide hole and the second guide hole under the action of the corresponding gas generating device, and the flow direction of the axial airflow is opposite to the movement direction of the target particles.

[0023] Furthermore, the angle between the fan-shaped tube and the horizontal plane is 5° to 25°, preferably 5° to 15°.

[0024] Furthermore, the number of the fan-shaped tubes is 4 to 36, and the angle between adjacent fan-shaped tubes is 10° to 90°. Preferably, the number of the fan-shaped tubes is 8 to 12, and the angle between adjacent fan-shaped tubes is 30° to 45°.

[0025] Furthermore, the aperture of the second flow guide hole gradually increases from the buffer chamber to the annular tube, and the aperture of the second flow guide hole is 0.1 mm to 10 mm, preferably 0.5 mm to 2 mm.

[0026] Furthermore, the aperture of the first guide hole is 0.1 mm to 10 mm, preferably 0.5 mm to 2 mm.

[0027] Furthermore, the temperature of the dry hot carrier gas is in the range of 100°C to 150°C, preferably 110°C.

[0028] The temperature is 130°C, and the dry hot carrier gas is one or more of hot nitrogen, hot argon, hot CO2, and hot air.

[0029] Furthermore, the temperature of the axial airflow flowing out of the gas distributor located above is lower than the temperature of the axial airflow flowing out of the gas distributor located below.

[0030] Furthermore, the distance between the gas distributor located above and the bottom end of the drying cylinder is 13m to 18m, preferably 15m to 16m.

[0031] Furthermore, a plurality of sampling ports are provided on the main body.

[0032] Furthermore, a heat-insulating layer is provided on the outer side of the main body.

[0033] Due to the application of the above technical solution, the beneficial effects of this application compared with the prior art are:

[0034] 1. The drying cylinder of the present invention has two gas distributors arranged in an upper and lower interval in the height direction, and the two gas distributors are connected to a gas generating device in a one-to-one manner to achieve separate regulation of the gas flow rate and temperature of the axial airflow flowing out of each gas distributor. It has strong operability, low gas pressure requirements, greatly reduces gas loss, and the flow direction of the airflow is opposite to the movement direction of the particles. Both realize countercurrent efficient mass transfer and heat transfer in a plug flow manner, with high drying efficiency and good effect.

[0035] 2. The present invention is provided with an air inlet pressure measuring port and an air inlet temperature measuring port on the gas inlet, and an air outlet temperature measuring port and an air outlet pressure measuring port on the gas outlet, which facilitates viewing of the conditions inside the tower and enables timely adjustment and control of the particle flow, gas flow, and temperature, thereby better controlling the drying process and significantly enhancing the drying effect of EVOH particles, ensuring high-quality, high-efficiency, and low-energy-consumption production.

[0036] 3. The gas distributor provided in the present invention combines an annular tube and a fan-shaped tube and is provided with a particle overflow hole, thereby avoiding the problems of incomplete drying of particles and particle blockage near the cylinder wall, ensuring the uniformity of drying and improving the drying efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0038] FIG1 is a schematic cross-sectional view of a drying tower provided by the present invention;

[0039] FIG2 is a schematic top view of the structure of the gas distributor of the drying tower provided by the present invention;

[0040] FIG3 is a schematic diagram of the structure of the gas distributor of the drying tower provided by the present invention when viewed from above.

[0041] Explanation of the reference numerals: 1-particle feed pipe; 2-particle distributor; 3-gas distributor; 31-buffer chamber; 32-annular pipe; 33-fan-shaped pipe; 34-air inlet pipe; 35-first guide hole; 36-second guide hole; 37-particle overflow hole; 4-particle discharge pipe; 5-gas air inlet; 6-gas air outlet; 7-main body; 71-head; 72-drying cylinder; 73-first cone section; 74-cooling pipe; 75-second cone section; 81-air inlet pressure measuring port; 82-air inlet temperature measuring port; 83-air outlet temperature measuring port; 84-air outlet pressure measuring port; 10-cavity. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings 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 in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0043] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein. In addition, the terms "including" and "having" and any related variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0044] In this application, terms such as "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "center," "vertical," "horizontal," "transverse," and "longitudinal" indicate positions or locations based on the positions or locations shown in the accompanying drawings. These terms are primarily intended to better describe the present invention and its embodiments and are not intended to limit the devices, elements, or components indicated to having a specific orientation, or to being constructed or operated in a specific orientation.

[0045] Furthermore, some of the above terms may be used to express other meanings besides indicating a position or location. For example, the term "on" may also be used to indicate a dependency or connection in certain circumstances. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0046] Furthermore, the terms "installed," "disposed," "provided with," "connected," "connected," and "socketed" should be interpreted broadly. For example, they can refer to fixed connections, removable connections, or integral structures; mechanical connections or electrical connections; direct connections or indirect connections through an intermediary; or internal communication between two devices, elements, or components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0047] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0048] Please refer to Figures 1 to 3. The present invention provides a drying tower for preparing low-water-content ethylene-vinyl alcohol copolymer particles, the drying tower comprising a main body 7, a particle feed pipe 1, a particle distributor 2, a gas distributor group, a particle discharge pipe 4, two gas inlets 5 and a gas outlet 6. The particle distributor 2 is used to evenly distribute the target particles (not shown) in the main body 7, and the two gas inlets 5 are connected one-to-one with a gas generator (not shown), which is used to generate a dry hot carrier gas, which is one or more of hot nitrogen, hot argon, hot CO2, and hot air. The gas generator is an existing conventional structure, which may have a heater, a control system, a temperature sensor, a pipeline and a valve, which will not be described in detail here.

[0049] As described above, the main body 7 has a cavity 10 within it. The main body 7 includes a head 71, a drying cylinder 72, a first cone section 73, a cooling pipe 74, and a second cone section 75, which are integrally connected and arranged from top to bottom along the height direction. The gas outlet 6 is provided on the head 71 and is connected to the cavity 10. It should be noted that the height direction is indicated by arrow a in Figure 1.

[0050] In order to prevent heat loss from affecting the temperature stability in the tower and to improve energy efficiency, an insulation layer (not shown) is provided on the outside of the main body 7. This is a conventional structure and will not be described in detail here.

[0051] The particle feed pipe 1 is installed on the head 71. One end of the particle feed pipe 1 extends into the cavity 10 to connect with the particle distributor 2 located in the drying cylinder 72. The other end extends from the head 71 to connect with other equipment (not shown) or pipelines (not shown), thereby facilitating the transportation and processing of the target particles. The particle distributor 2 is a conventional structure that can have several distribution pipes and several distribution holes provided in each distribution pipe. The distribution pipes are connected to the particle feed pipe 1 and extend into the interior of the drying cylinder 72. The distribution holes provided in the distribution pipes are used to evenly release the target particles into the drying cylinder 72. The details are not elaborated here.

[0052] The gas distributor assembly is located within the drying cylinder 72 and below the particle distributor 2. It includes two gas distributors 3, spaced vertically apart. Two gas inlets 5 are arranged on the drying cylinder 72 and communicate with the two gas distributors 3 in a one-to-one fashion. Specifically, the distance between the upper gas distributor 3 and the bottom of the drying cylinder 72 is 13 to 18 meters, including but not limited to 13, 14, 15, 16, 17, and 18 meters.

[0053] In detail, the gas distributor 3 includes a buffer chamber 31, an annular tube 32 sleeved outside the buffer chamber 31, a plurality of fan-shaped tubes 33 connecting the buffer chamber 31 and the annular tube 32, an air inlet pipe 34 connecting the buffer chamber 31 and the corresponding gas inlet 5, a plurality of first guide holes 35 provided at the top of the annular tube 32, a plurality of second guide holes 36 provided at the top of the fan-shaped tubes 33, and a particle overflow hole 37 provided at the bottom of the fan-shaped tubes 33. The fan-shaped tubes 33 are arranged at equal intervals along the circumferential direction between the buffer chamber 31 and the annular tube 32. The number of fan-shaped tubes 33 ranges from 4 to 36, and the angle between adjacent fan-shaped tubes 33 ranges from 10° to 90°.

[0054] The gas distributor 3 is suitable for generating an axial airflow flowing out of the first guide hole 35 and the second guide hole 36 under the action of the corresponding gas generating device, and the flow direction of the axial airflow is opposite to the movement direction of the target particles. Since the axial airflow flowing out of the gas distributor 3 located below has a longer flow path, in order to avoid heat loss affecting the temperature of the drying of the target particles, the temperature of the axial airflow flowing out of the gas distributor 3 located above is less than or equal to the temperature of the axial airflow flowing out of the gas distributor 3 located below. It should be noted that the flow direction of the axial airflow is from bottom to top in the height direction, and the movement direction of the target particles is from top to bottom in the height direction, so that the target particles entering from the particle feeding pipe 1 form a countercurrent contact with the axial airflow, so that the target particles move slowly from top to bottom, the temperature of the target particles gradually increases, and the moisture content gradually decreases. The hot drying carrier gas enters the buffer chamber 31 from the air inlet pipe 34, is then diverted to the fan-shaped pipe 33, and then flows into the annular pipe 32 to fill the entire gas distributor 3, so that the hot drying carrier gas can be evenly distributed in the drying cylinder 72 through the first guide hole 35 and the second guide hole 36, avoiding local gas dead zones.

[0055] In order to avoid the problem of incomplete drying and uneven drying of the target particles near the cylinder wall, the diameter of the fan-shaped tube 33 gradually increases from the buffer chamber 31 to the annular tube 32, and the fan-shaped tube 33 is arranged downwardly inclined. The particle overflow hole 37 is set close to the annular tube 32, and the diameter of the annular tube 32 is adapted to the inner diameter of the drying cylinder 72.

[0056] Specifically, the angle between the fan-shaped tube 33 and the horizontal plane is 5° to 25°, including but not limited to 5°, 6°, 7°, 8°, 9°, 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, and 25°. The diameter of the second guide hole 36 gradually increases from the buffer chamber 31 to the annular tube 32, and the diameter of the second guide hole 36 is 0.1mm to 10mm. The diameter of the first guide hole 35 is 0.1mm to 10mm.

[0057] The particle discharge pipe 4 is provided on the second cone section 75, one end of the particle discharge pipe 4 extends into the cavity 10, and the other end extends out of the second cone section 75 to connect to other equipment (not shown) or pipelines (not shown), thereby facilitating the transportation and processing of target particles.

[0058] To facilitate monitoring of the tower's internal conditions and timely adjust and control the target particle flow rate, gas flow rate, and temperature, thereby ensuring better control of the drying process, the gas inlet 5 is equipped with an inlet pressure measuring port 81 and an inlet temperature measuring port 82. The gas outlet 6 is equipped with an outlet temperature measuring port 83 and an outlet pressure measuring port 84. Several sampling ports (not shown) are also provided on the main body 7. These are conventional features and will not be described in detail here.

[0059] The area where the gas distributor 3 is located at the bottom is the main flow section, and the main flow gas-to-solid mass flow rate ratio FR1 is 1.3:1 to 2.0:1, including but not limited to 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, and 2.0:1. The area where the gas distributor 3 is located at the top is the branch flow section, and the branch flow gas-to-solid mass flow rate ratio FR2 is 2.2:1 to 3.1:1, including but not limited to 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3.0:1, and 3.1:1. The target particle residence time in the drying tower is 8 to 25 hours.

[0060] Due to the application of the above technical solution, the beneficial effects of this application compared with the prior art are:

[0061] 1. The drying cylinder of the present invention has two gas distributors arranged in an upper and lower interval in the height direction, and the two gas distributors are connected to a gas generating device in a one-to-one manner to achieve separate regulation of the gas flow rate and temperature of the axial airflow flowing out of each gas distributor. It has strong operability, low gas pressure requirements, greatly reduces gas loss, and the flow direction of the airflow is opposite to the movement direction of the particles. Both realize countercurrent efficient mass transfer and heat transfer in a plug flow manner, with high drying efficiency and good effect.

[0062] 2. The present invention is provided with an air inlet pressure measuring port and an air inlet temperature measuring port on the gas inlet, and an air outlet temperature measuring port and an air outlet pressure measuring port on the gas outlet, which facilitates viewing of the conditions inside the tower and enables timely adjustment and control of the particle flow, gas flow, and temperature, thereby better controlling the drying process and significantly enhancing the drying effect of EVOH particles, ensuring high-quality, high-efficiency, and low-energy-consumption production.

[0063] 3. The gas distributor provided in the present invention combines an annular tube and a fan-shaped tube and is provided with a particle overflow hole, thereby avoiding the problems of incomplete drying of particles and particle blockage near the cylinder wall, ensuring the uniformity of drying and improving the drying efficiency.

[0064] Example 1

[0065] This embodiment relates to a drying tower for preparing low-water-content ethylene-vinyl alcohol copolymer particles. The structure of the drying tower is the same as that of the above-mentioned drying tower, and reference may be made to the aforementioned content.

[0066] In this embodiment, the distance between the upper gas distributor and the bottom end of the drying cylinder is 16 m.

[0067] The number of the fan-shaped tubes is 8 to 12, and they are arranged around the outer periphery of the buffer chamber at intervals of 30° to 45°.

[0068] The aperture range of the first guide hole and the second guide hole is 0.5mm to 2mm.

[0069] The angle between the fan-shaped tube and the horizontal plane is 5° to 15°.

[0070] The temperature of the axial airflow flowing out of the gas distributor located at the top is 110°C to 120°C, and the temperature of the axial airflow flowing out of the gas distributor located at the bottom is 120°C to 130°C.

[0071] The ratio of gas-solid mass flow rate in the main line FR1 is 1.3:1 to 1.5:1, and the ratio of gas-solid mass flow rate in the branch line FR2 is 2.2:1 to 2.5:1. The target particle residence time in the drying tower is 12 hours to 15 hours.

[0072] In this embodiment, two streams of hot dry carrier gas at different temperatures enter the drying tower from two separate gas distributors. After distribution, they come into countercurrent contact with the high-moisture target particles continuously entering from the pellet feed pipe. Two gas generators control the different temperatures and flow rates of the hot dry carrier gas, achieving sufficient heat and mass transfer and drying within the drying tower. Within a short residence time, the target particles are reduced to a moisture content below 0.5 wt%. The target particles are discharged from the pellet discharge pipe, and the vapor-containing gas phase is discharged from the gas outlet. The overall moisture transfer process can be divided into two parts: first, heat transfer. The lower-temperature, high-moisture target particles contact the hot dry carrier gas and heat up. Water on the target particle surface is heated until it vaporizes and is continuously transferred to the surrounding hot dry carrier gas, representing a gas-solid mass transfer process. Water within the target particle continuously diffuses toward the surface, representing an internal diffusion-controlled moisture removal process. After these two steps of diffusion and mass transfer, the moisture in the target particle is ultimately carried away from the drying tower by the hot dry carrier gas. The drying tower in this embodiment is suitable for high-throughput drying of hydrophilic EVOH wet pellets with a moisture content exceeding 5 wt%.

[0073] Example 2

[0074] This embodiment relates to a drying tower for preparing low-water-content ethylene-vinyl alcohol copolymer particles. The structure of the drying tower is similar to that of the drying tower in Example 1, except that:

[0075] In this embodiment, the distance between the upper gas distributor and the bottom end of the drying cylinder is 15 meters. The number of fan-shaped pipes is 15 to 20, and they are arranged around the outer periphery of the buffer chamber at intervals of 18° to 24°.

[0076] The temperature of the axial airflow flowing out of the gas distributor located at the top is 120°C to 130°C, and the temperature of the axial airflow flowing out of the gas distributor located at the bottom is 130°C to 140°C.

[0077] The ratio of gas-solid mass flow rate in the main circuit FR1 is 1.5:1 to 2.0:1, and the ratio of gas-solid mass flow rate in the branch circuit FR2 is 2.5:1 to 3.0:1. The particle residence time in the drying tower is 20h to 25h.

[0078] In this embodiment, two gas generators control different drying hot carrier gas temperatures and flow rates, achieving sufficient heat and mass transfer and drying within the drying tower. This simultaneously increases the temperature and flow rates of the main and branch drying hot carrier gases, while also lowering the branch air inlet locations. This allows the drying tower to provide more heat. The increased number of fan-shaped tubes ensures more uniform distribution of the drying hot carrier gas, extending the residence time and resulting in more thorough drying of the target particles. This drying tower is suitable for drying wet EVOH pellets with a moisture content of less than 0.2 wt%.

[0079] Example 3

[0080] This embodiment relates to a drying tower for preparing low-water-content ethylene-vinyl alcohol copolymer particles. The structure of the drying tower is similar to that of the drying tower in Example 1, except that:

[0081] In this embodiment, the distance between the upper gas distributor and the bottom end of the drying cylinder is 15 meters. The number of fan-shaped pipes is 15 to 20, and they are arranged around the outer periphery of the buffer chamber at intervals of 18° to 24°.

[0082] The aperture range of the first guide hole and the second guide hole is 1 mm to 2.5 mm.

[0083] The temperature of the axial airflow flowing out of the gas distributor located at the top is 110°C to 120°C, and the temperature of the axial airflow flowing out of the gas distributor located at the bottom is 130°C to 140°C.

[0084] The ratio of gas-solid mass flow rate in the main line FR1 is 1.3:1 to 1.5:1, and the ratio of gas-solid mass flow rate in the branch line FR2 is 2.5:1 to 3.0:1. The particle residence time in the drying tower is 20h to 25h.

[0085] In this embodiment, the branch drying hot carrier gas temperature and flow rate are increased, and the branch air inlet position is lowered, allowing the upper drying tower to provide more heat, which facilitates mass transfer between the gas and solid phases. Furthermore, the apertures of the first and second guide holes in the fan-shaped tubes are increased to prevent slicing blockage. Furthermore, the number of fan-shaped tubes is increased to achieve more uniform gas distribution and a closer plug flow between the gas and solid phases, achieving the desired particle drying performance with a shorter residence time. This drying tower is suitable for drying wet EVOH pellets less than 2 mm in size.

[0086] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A drying tower for preparing low-water-content ethylene-vinyl alcohol copolymer particles, characterized in that: include: The main body has a cavity inside, and the main body includes a head, a drying cylinder, a first cone section, a cooling pipe and a second cone section which are connected and arranged in an integral manner from top to bottom along the height direction; A particle feeding pipe is provided on the head, one end of the particle feeding pipe extends into the cavity, and the other end extends out of the head; a particle distributor, disposed in the drying cylinder and connected to the particle feed pipe, for evenly distributing the target particles in the drying cylinder; A gas distributor group is arranged in the drying cylinder and below the particle distributor, the gas distributor group includes two gas distributors, and the two gas distributors are arranged in an upper and lower spacing in the height direction; a particle discharge pipe, which is provided on the second cone section, with one end of the particle discharge pipe extending into the cavity and the other end extending out of the second cone section; Two gas inlets are arranged on the drying cylinder and are connected to the two gas distributors in a one-to-one manner, and the gas inlets are provided with an air inlet pressure measuring port and an air inlet temperature measuring port; and A gas outlet is provided on the head and is connected to the cavity, and an outlet temperature measuring port and an outlet pressure measuring port are provided on the gas outlet; The gas distributor includes a buffer chamber, an annular tube sleeved outside the buffer chamber, a plurality of fan-shaped tubes connecting the buffer chamber and the annular tube, an air inlet tube connecting the buffer chamber and the corresponding gas inlet, a plurality of first guide holes provided at the top of the annular tube, a plurality of second guide holes provided at the top of the fan-shaped tube, and a particle overflow hole provided at the bottom of the fan-shaped tube, wherein the plurality of fan-shaped tubes are arranged at equal intervals along the circumferential direction between the buffer chamber and the annular tube; From the buffer chamber to the annular tube, the diameter of the fan-shaped tube gradually increases, and the fan-shaped tube is arranged to be tilted downward, the particle overflow hole is arranged close to the annular tube, and the diameter of the annular tube is adapted to the inner diameter of the drying cylinder; The two gas inlets are connected one-to-one with a gas generating device, and the gas generating device is used to generate dry hot carrier gas. The gas distributor is suitable for generating axial airflow flowing out from the first guide hole and the second guide hole under the action of the corresponding gas generating device, and the flow direction of the axial airflow is opposite to the movement direction of the target particles.

2. The drying tower according to claim 1, wherein The angle between the fan-shaped tube and the horizontal plane is 5° to 25°.

3. The drying tower according to claim 1, wherein The number of the fan-shaped tubes is 4 to 36, and the angle between adjacent fan-shaped tubes is 10° to 90°.

4. The drying tower according to claim 1, wherein The aperture of the second flow guide hole gradually increases from the buffer chamber to the annular tube, and the aperture of the second flow guide hole is 0.1 mm to 10 mm.

5. The drying tower according to claim 1, wherein The aperture of the first guide hole is 0.1 mm to 10 mm.

6. The drying tower according to claim 1, wherein The temperature range of the dry hot carrier gas is 100° C. to 150° C., and the dry hot carrier gas is one or more of hot nitrogen, hot argon, hot CO 2 , and hot air.

7. The drying tower according to claim 6, wherein The temperature of the axial airflow flowing out of the gas distributor located above is lower than the temperature of the axial airflow flowing out of the gas distributor located below.

8. The drying tower according to claim 7, wherein The distance between the gas distributor located above and the bottom end of the drying cylinder is 13m to 18m.

9. The drying tower according to claim 1, wherein The main body is provided with a plurality of sampling ports.

10. The drying tower according to claim 1, wherein A heat-insulating layer is provided on the outer side of the main body.

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