A plastic drying and sorting system and method of using the same

Abstract

The application relates to a plastic material drying and sorting system, which comprises a material conveying assembly, a lifting drying pipe and a descending drying pipe, the outlet of the material conveying assembly is communicated with the inlet of the lifting drying pipe, and a gas distribution assembly is arranged at the communication position of the lifting drying pipe and the descending drying pipe; the gas distribution assembly is used for blowing the material to make the material in a suspended state; a material breaker is arranged at the upper half section of the descending drying pipe and is used for scattering the material; the plastic content in the material is 60-80% by weight. The application not only solves the problems that the plastic is easy to accumulate and easy to form a bridge, but also improves the drying effect.

Description

Technical Field

[0001] This application relates to the technical field of plastic drying, and in particular to a drying and sorting system for industrial waste plastics used in the high-moisture film industry of paper mills. Background Technology

[0002] Current plastic drying systems mainly include rotary drying units, tunnel drying units, and pipeline drying units. Rotary drying units, in particular, have low drying efficiency, high investment costs, high operating costs, and uneven drying quality.

[0003] While existing pipeline drying equipment has solved the problems of investment and operating costs, there are still some defects and shortcomings in system design and operation. For example, the material stays in the drying pipeline for a short time and is not completely dried; impurities are not separated out, affecting the use of fans and subsequent equipment; pipe bends are prone to wear; the feed rate is unstable, which easily leads to material blockage and bridging, and the system cannot operate continuously. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this application is to provide a plastic material drying system with high drying efficiency, uniform drying quality, and the ability to sort out impurities.

[0005] The above-mentioned objective of this application is achieved through the following technical solution:

[0006] A drying and sorting system for plastic materials includes a material conveying component, an lifting drying pipe, and a descending drying pipe. The outlet of the material conveying component is connected to the inlet of the lifting drying pipe. A gas distribution component is arranged at the connection between the lifting drying pipe and the descending drying pipe. The gas distribution component is used to blow the material to suspend it. A material distributor is arranged in the upper half of the descending drying pipe to disperse the material. The plastic content in the material is about 60%-80% by weight.

[0007] In one embodiment, the feeder includes a main shaft and blades fixedly connected to the main shaft. The blades are arranged perpendicular to the main shaft, and a rubber sheet is connected to the free end of the blade. The total length of the blade and the rubber sheet is sufficient to achieve a sealed contact with the wall of the descending drying tube. Optionally, the free end of the rubber sheet is arc-shaped.

[0008] In one implementation, the feeder maintains a flexible seal with the descending drying tube.

[0009] In one implementation, the upper edge of the rotary feeder blades is 200-400 mm away from the discharge port of the descending drying tube.

[0010] In one embodiment, the gas distribution assembly includes a hollow shell, the upper half of which has a trapezoidal longitudinal section and the lower half has a cylindrical longitudinal section, and the overall longitudinal section of the shell is torch-shaped; a gas inlet is provided at the bottom of the lower half, and the upper surface of the upper half is covered with through holes as gas outlets, forming a gas chamber in the space between the upper and lower halves.

[0011] In one embodiment, the material conveying assembly includes a feed box and two air-tight feeders respectively arranged above and below the feed box outlet; a surface elastic roller is arranged at the feed box outlet and between the two air-tight feeders, and a gas distribution device is arranged downstream of the surface elastic roller, with the gas outlet of the gas distribution device facing the inlet of the lifting drying pipe.

[0012] In one embodiment, the air-tight feeder includes a rotatable impeller and a housing that matches the shape of the impeller.

[0013] In one implementation, the diameter of the lowering drying tube is 1.2 to 1.5 times the diameter of the raising drying tube.

[0014] In one implementation, the height of the drying tube is lowered by 0.6 to 0.8 times the height of the drying tube is raised.

[0015] This application also relates to a method for drying and sorting plastic materials, which is implemented using the drying and sorting system of this application.

[0016] In one embodiment of the method for drying and sorting plastic materials, the following parameters are specified: the height H (m) of the lifting drying pipe, the gas velocity V (m / s) of the gas distribution component, the diameter D (m) of the lifting drying pipe, and the gas density ρ (kg / m³). 3 The following relationship must be satisfied:

[0017] H*V2 / 2 / D*ρ*0.02≤100pa.

[0018] In one embodiment of drying and sorting plastic materials, the gas velocity inside the lifting drying pipe is 15m / s-20m / s, the diameter of the lifting drying pipe is in the range of DN700-DN800, and the height of the lifting drying pipe is in the range of 9.9m-13m.

[0019] In one embodiment of drying and sorting plastic materials, the residence time of the material in the pipe is 4.5s-5.5s.

[0020] The plastic material drying and sorting system of this application operates in a completely enclosed state throughout the entire process of drying and sorting materials, ensuring that the materials do not come into contact with the outside environment. This achieves efficient drying and material sorting without polluting the environment. The device employs a specially designed feeding arrangement at the inlet, which not only achieves sealed feeding but also effectively prevents gas leakage, controls the feeding speed, and prevents material accumulation and bridging. Furthermore, the device incorporates a material distributor within the descending drying pipe, ensuring that the material is evenly distributed during its descent and preventing tangling. Attached image description:

[0021] Figure 1 This is a schematic diagram of the drying and sorting system of this application;

[0022] Figure 2 This is a schematic diagram of the feeder structure;

[0023] Figure 3 This is a schematic diagram of the air-tight feeder.

[0024] Figure 4 This is a schematic diagram of the gas distribution component;

[0025] Figure 5 This is a comparison chart of the moisture content of materials after drying and sorting using the system of this application and existing technology systems;

[0026] Figure 6 This is a comparison chart of the impurity content of materials after drying and sorting using the system of this application and existing technology systems. Detailed Implementation

[0027] The plastic material drying and sorting system of this application is mainly used for the simultaneous sorting and drying of lightweight materials. The plastic content in the plastic material is in the range of 60%-80%, and the moisture content of the plastic material is less than 40%. When the plastic content is less than 50%, the drying efficiency will decrease, the sorting difficulty will increase, and the economic benefits will be poor. Preferably, the particle size of the plastic material is 50mm-100mm, and the plastic material with a particle size of less than 50mm accounts for more than 80% by weight.

[0028] The plastic material drying and sorting system of this application includes a descending drying pipe and an ascending drying pipe, with a gas distribution component arranged at the connection point between the descending and ascending drying pipes. The gas distribution component is used to blow the material to suspend it. A material feeder is arranged in the upper half of the descending drying pipe to disperse the material. During operation, the gas distribution component blows gas into the inner cavity of the connecting pipe, keeping the material in a suspended state. In one embodiment, the gas blowing direction is tapered along the diameter of the pipe, preferably with a cone angle of 0-80 degrees (excluding 0 degrees), and preferably, the gas blowing direction is parallel to the diameter of the pipe.

[0029] In the preferred embodiment of this application, the total residence time of the material in the pipeline is ensured to be within the range of 4.5s-5.5s, thereby achieving better drying and sorting results. To meet the above residence time, this application studies and controls various factors such as the descending drying pipe, the rising drying pipe, and the gas velocity.

[0030] In one embodiment, within the descending drying tube, the relationship between the diameter of the descending drying tube and the gas velocity is V = Q / 3600 / (0.785D). 2 ), where Q(m) 3 / h) is the gas flow rate, D(m) is the pipe diameter, and V(m / s) is the gas velocity, thus satisfying the requirement that the suspension height of the material in the pipe is 1 / 3 to 2 / 3 of the pipe diameter.

[0031] In one embodiment, the diameter of the descending drying tube is in the range of 800mm-900mm, the gas velocity is in the range of 14m / s-18m / s, and the gas flow rate Q is 28000m³ / s. 3 / h-36000m 3 Between / h.

[0032] To meet the gas velocity requirements, the diameter of the descending drying tube is 1.12-1.15 times that of the ascending drying tube.

[0033] In one embodiment, the height of the drying tube is lowered by 0.6-0.8 times, preferably 0.8 times, the height of the drying tube is increased.

[0034] To achieve ideal material drying and sorting results, the plastic material must not only be fed into the lifting drying pipe and smoothly conveyed to the descending drying pipe, but the gas velocity, lifting drying pipe diameter, and lifting drying pipe height must also satisfy the following relationship:

[0035] H×V 2 / 2 / D×ρ×0.02≤100pa,

[0036] H(m) is the height of the drying riser pipe, V(m / s) is the gas velocity inside the pipe, D(m) is the diameter of the drying riser pipe, and ρ(kg / m²) is the gas velocity inside the pipe. 3 () represents the gas density.

[0037] Typically, the gas can be air, nitrogen, or other inert gases.

[0038] In a preferred embodiment, the height of the lifting drying tube / the diameter of the lifting drying tube = 12.

[0039] In one embodiment, the gas velocity inside the lifting drying pipe is 15m / s-20m / s, the diameter of the lifting drying pipe is in the range of DN700-DN800, and the height of the lifting drying pipe is in the range of 9.9m-13m.

[0040] A rotatable feeder is arranged at the upper discharge port of the descending drying tube in this application. In one embodiment, two rotatable feeders are arranged at the upper discharge port of the descending drying tube.

[0041] During operation, the high-temperature gas in the pipeline carries the plastic material, and the temperature of the high-temperature gas is in the range of 130-180℃ in the direction of gas flow.

[0042] The diameter of the descending drying pipe is larger than that of the rising drying pipe, mainly to reduce the gas velocity in the descending drying pipe, extend the residence time of the plastic material in the descending drying pipe, and ensure the drying effect.

[0043] A rotatable feeder is installed inside the descending drying tube to quickly lift the plastic material carried by the gas upwards as it enters the tube. The ultimate goal is to extend the residence time of the plastic film within the tube. In one implementation, the feed rate is 2800 kg / h-5600 kg / h, and the feeder rotates at 120 r / min, ensuring both effective drying and smooth operation.

[0044] The drying medium in this application (i.e., the gas in the gas distribution component) is hot air at a temperature of 130-180°C, preferably 150°C. This temperature is chosen primarily to account for the unique thermal decomposition properties of plastics; if the temperature is too high, volatile gases will be produced; if the temperature is too low, the drying efficiency will decrease. Additionally, hot air has a strong drying capacity for materials with high moisture content. In this application, when the drying medium is hot air at a temperature of 130-180°C, the moisture content of the plastic material can be in the range of 10%-50%, and after drying, the moisture content of the material is reduced to 5%-8%. In a preferred embodiment, when the hot air temperature is 140-150°C, the moisture content of the plastic material can be in the range of 18%-22%, and after drying, the moisture content of the material is reduced to 3%-6%, achieving optimal drying results without melting the plastic.

[0045] In the device of this application, a material conveying assembly is provided in the feeding stage, including a feeding box and two air-locked feeders respectively arranged above and below the outlet of the feeding box; a surface elastic roller is arranged at the outlet of the feeding box and between the two air-locked feeders, and a gas distribution device is arranged downstream of the surface elastic roller, with the gas outlet of the gas distribution device facing the inlet of the lifting drying pipe.

[0046] In one embodiment, the airtight feeder includes a rotatable impeller and a housing that matches the shape of the impeller. The end of the impeller achieves a rotary seal with the inner wall of the feeder.

[0047] The material conveying component of this application can control the feed rate, avoid material accumulation, and prevent bridging.

[0048] During operation, in the material conveying assembly of this application, the surface-elastic roller applies centrifugal force to the moving material, causing lighter and heavier materials to acquire different velocity components. The lighter material then enters the lifting and drying pipe with hot air, while the heavier material is screwed into the discharge port, achieving the purpose of sorting. The roller's surface is designed to be elastic to utilize the differences in elastic recovery characteristics of different materials during collisions for sorting. In this application, the roller surface is a high-elasticity, heat-resistant rubber layer with a thickness of 20-30 mm, preferably PA10T rubber.

[0049] During operation, the material falls onto the rubber layer of the drum at a height of about 300-400mm above the upper surface of the drum. The drum surface rotates at a linear speed of 1-3m / s (adjustable). Under the action of the elasticity of the rubber layer surface and the scattering force applied by the rotation of the drum, lighter materials (such as plastics) will gain greater speed under the action of elasticity and scattering force and enter the drying pipe with the hot airflow, while heavier materials (such as sand, glass, metal, etc.) are difficult to bounce and scatter and eventually fall into the discharge valve.

[0050] In one embodiment, the bends in the pipes of this application can be made of wear-resistant materials to improve the wear resistance of the pipes and extend the service life of the equipment. For example, the TLD-DN800 ceramic-lined wear-resistant elbow.

[0051] In the apparatus of this application, a gas distribution assembly is arranged at the connection between the lifting drying pipe and the lowering drying pipe. The gas distribution assembly includes a hollow shell, the upper half of which has a trapezoidal longitudinal section, and the lower half has a cylindrical longitudinal section. The overall longitudinal section of the shell is torch-shaped. A gas inlet is provided at the bottom of the lower half, and the upper surface of the upper half is covered with through holes as gas outlets, forming a gas chamber in the space between the upper and lower halves. To avoid material deposition and blockage in the horizontal section at the connection, the gas ejection range of the through holes is designed to cover at least 80° of the pipe cross-section. The axial ejection range of the gas in the pipe is such that the airflow direction forms a 60° angle with the horizontal, thereby giving the material a forward thrust.

[0052] In the apparatus of this application, a material feeder is arranged in the upper half of the descending drying pipe. The material feeder includes a main shaft and blades fixedly connected to the main shaft. The blades are arranged perpendicular to the main shaft, and rubber sheets are connected to the free ends of the blades. The total length of the blades and rubber sheets is sufficient to ensure sealing contact with the pipe wall of the descending drying pipe. In one embodiment, the free end of the rubber sheet is arc-shaped. During operation, the main shaft rotates under the drive of the drive device, and the blades rotate under the drive of the main shaft, quickly feeding up the falling material, thereby extending the residence time of the material in the pipe, thus enhancing the drying effect and improving the drying efficiency.

[0053] In one implementation, two horizontally arranged rotary feeders are arranged in the descending drying tube, allowing for greater space within the tube for the feeders to operate on, thereby lifting more material. In another implementation, the upper edge of the feeder blades is approximately 200-400 mm from the discharge port of the descending drying tube. If this distance is too close, it can easily clog the inlet; if it is too far, it will not achieve the purpose of delaying material discharge.

[0054] The structural schematic diagram of the plastic material drying and sorting system of this application is shown below. Figure 1 As shown.

[0055] like Figure 1 As shown, the plastic material drying and sorting system includes a material conveying assembly, lifting drying pipes (5, 10), and descending drying pipes (9, 11). The outlet of the material conveying assembly is connected to the inlet of the lifting drying pipe 5. A gas distribution assembly 7 is arranged at the connection between the lifting drying pipe and the descending drying pipe. The gas distribution assembly 7 is used to blow the material to keep it in a suspended state. A material feeder 8 is arranged in the upper half of the descending drying pipe (9, 11) to disperse the material. After the material is dried, it continues to move downstream under the action of the high-efficiency centrifugal fan 12 and the material's own gravity, and finally the gas and solid are separated by the cyclone separator (13) and discharged separately.

[0056] The blower 12 provides power to the system and can be a high-pressure centrifugal blower. The casing of the blower 12 can be made of high-strength steel, and the impeller can be made of stainless steel, which can prevent wear, deformation under high temperature and stress, etc., thereby ensuring the long-term operation of the system.

[0057] In one implementation, the cyclone dust collector 13 conforms to the FLUENT flow field simulation design, has reasonable size, and high separation efficiency, effectively separating drying gas and materials at the end of the process section.

[0058] The material conveying assembly includes a feed box, which includes a surface elastic roller 2 and two air-tight feeders 1 and an air inlet pipe 3 respectively arranged above and below the roller; a gas distribution device 4 is arranged downstream of the roller, and the air outlet of the gas distribution device 4 faces the inlet of the lifting drying pipe.

[0059] In one embodiment, the airtight feeder includes a rotatable impeller and a housing that matches the shape of the impeller. The end of the impeller achieves a rotary seal with the inner wall of the feeder.

[0060] In the material conveying assembly of this application, a surface-elastic roller applies centrifugal force to the moving material, causing lighter and heavier materials to acquire different velocity components. The lighter material is then carried by hot air into the lifting and drying pipe, while the heavier material is screwed into the discharge port, achieving the purpose of sorting. The roller's surface is designed to be elastic to utilize the differences in elastic recovery characteristics of different materials during collisions for sorting. In this application, the roller surface is a high-elasticity, heat-resistant rubber layer with a thickness of 20-30 mm, preferably PA10T rubber.

[0061] During operation, the material falls onto the rubber layer of the drum at a height of about 300-400mm above the upper surface of the drum. The drum surface rotates at a linear speed of 1-3m / s (adjustable). Under the action of the elasticity of the rubber layer surface and the scattering force applied by the rotation of the drum, lighter materials (such as plastics) will gain greater speed under the action of elasticity and scattering force and enter the drying pipe with the hot airflow, while heavier materials (such as sand, glass, metal, etc.) are difficult to bounce and scatter and eventually fall into the discharge valve.

[0062] The structural schematic diagram of the feeder in this application is shown below. Figure 2 As shown.

[0063] like Figure 2 As shown, the feeder 8 includes a main shaft 8-1 and blades 8-2 fixedly connected to the main shaft. The blades are arranged perpendicular to the main shaft. A rubber sheet 8-3 is connected to the free end of the blade. The total length of the blade and the rubber sheet is sufficient to seal the contact with the wall of the descending drying tube. Optionally, the free end of the rubber sheet is arc-shaped.

[0064] In one embodiment, the material conveying assembly includes a feed hopper and two air-tight feeders respectively arranged above and below the feed hopper outlet; a surface elastic roller is arranged at the feed hopper outlet, between the two air-tight feeders, and a gas distribution device is arranged downstream of the surface elastic roller, with the gas outlet of the gas distribution device facing the inlet of the lifting drying pipe. In this embodiment, the gas distribution device may be the same as or different from the gas distribution assembly mentioned above, as long as the gas distribution device can blow up the material and assist in feeding it into the lifting drying pipe.

[0065] In one implementation scheme, a schematic diagram of the air-tight feeder is shown below. Figure 3 As shown.

[0066] like Figure 3As shown, the airtight feeder includes a rotatable impeller 1-3 and a housing 1-2 that matches the shape of the impeller. The impeller 1-3 rotates under the drive of the central shaft 1-4. The material enters the airtight feeder from the inlet 1-1 and falls onto the surface of the drum 2 from the outlet 1-5 under the influence of the impeller. Under the action of the elastic force of the rubber layer on the surface of the drum and the scattering force applied by the rotation of the drum, lighter materials (such as plastics) enter the drying pipe with the hot drying medium, while heavier materials (such as sand, glass, metal, etc.) are difficult to bounce and scatter, and finally fall into the airtight feeder arranged below the drum and are discharged from the outlet of the airtight feeder.

[0067] In one implementation scheme, a schematic diagram of the gas distribution component is shown below. Figure 4 As shown.

[0068] like Figure 4 As shown, the gas distribution component includes a hollow shell. The longitudinal section of the upper half 7-1 of the shell is trapezoidal, and the longitudinal section of the lower half 7-4 is cylindrical. The overall longitudinal section of the shell is torch-shaped. A gas inlet is located at the bottom of the lower half, and the upper surface of the upper half is covered with through holes as gas outlets 7-2. A gas chamber 7-3 is formed in the space between the upper and lower halves. The distribution range of the through holes is: symmetrically distributed left and right with the center of the pipe as the center and the vertical radius as the axis of symmetry, forming a fan shape with a central angle of 80° or higher. If the central angle is lower than 80°, the fluidization effect of the material is poor; if the central angle is higher than 180°, the fluidization effect is not significant. The gas is ejected from the through holes, and the angle between the ejection direction and the horizontal line is in the range of 20° to 60° (as shown in the figure, the outer angle). If the angle is higher than 60°, an air curtain is easily formed, hindering the forward movement of the material; if the angle is lower than 20°, the effect of the airflow is small and not obvious.

[0069] In this application, the gas distribution device and the gas distribution component can be the same or different, as long as the gas distribution device can blow up the material and assist in feeding it into the lifting drying pipe.

[0070] Example

[0071] The drying and sorting system of this application is used to dry and sort plastic materials. It is equipped with two sets of lifting drying pipes and two sets of descending drying pipes. The cyclone separator is φ1720×5200, and the blower power is 75kw. The plastic material is a mixture of paper mill plastic film, plastic mulch film, etc., with a plastic content of 60-80% by weight, a moisture content of 18-22% by weight, and a particle size of 50mm-100mm. Plastic materials with a particle size below 50mm account for approximately 90% by weight.

[0072] The diameter of the lifting drying pipe is 700mm, the height is 12.5m, and the gas velocity inside the lifting drying pipe is 20m / s.

[0073] The diameter of the descending drying pipe is 900 mm, the height is 8 m, the gas velocity inside the descending drying pipe is 15 m / s, and the gas flow rate Q is 34335.9 m³ / s. 3 / h.

[0074] The drying medium is hot air at 150℃-180℃. The diameter of the surface elastic roller is 400mm.

[0075] Two feeders were installed at the inlet of each of the two sets of descending drying pipes.

[0076] In this embodiment, the plastic material was fed at a rate of 5000 kg / h and operated continuously for 25 days. The moisture content and plastic content of the plastic were recorded after drying and sorting.

[0077] A DLSG1918 drying system (obtained from Zhengzhou Dingli Company, without a lifting drying pipe) was used to dry and sort the aforementioned plastic materials under the same conditions, running continuously for 25 days. The moisture content and impurity content of the plastic after drying and sorting were recorded daily.

[0078] The moisture content and impurities of the plastic after drying and sorting are as follows: Figure 5 and Figure 6 As shown.

[0079] from Figure 5 and Figure 6 As can be seen, using the drying and sorting system of this application, the moisture content of the plastic is below 5% by weight, and can even reach 0.5% by weight; the impurity content in the plastic is below 0.5% by weight, and the plastic content is above 99.5% by weight. Impurities such as metal, sand, and glass are basically sorted out, and no melting, entanglement or knotting is observed in the obtained plastic.

[0080] After being processed by the DLSG1918 drying system, the plastic material still had a high moisture content of 8-12% by weight, even reaching 17% by weight; the impurity content in the plastic was 70-85% by weight, with little change compared to before drying and sorting. On the 17th day of operation, the plastic material became blocked at the cyclone separator, causing the gas velocity in the pipeline to drop sharply to 5 m / s; after being shut down and manually cleared, operation resumed.

Claims

1. A drying and sorting system for plastic materials, comprising a material conveying component, an lifting drying pipe, and a descending drying pipe, wherein the outlet of the material conveying component is connected to the inlet of the lifting drying pipe, and a gas distribution component is arranged at the connection between the lifting drying pipe and the descending drying pipe; the gas distribution component is used to blow the material to suspend it; a material distributor is arranged in the upper half of the descending drying pipe to disperse the material, wherein the plastic content of the material is 60-80% by weight. The feeder includes a main shaft and blades fixedly connected to the main shaft. The blades are arranged perpendicular to the main shaft. A rubber sheet is connected to the free end of the blade. The total length of the blade and the rubber sheet is sufficient to ensure a sealed contact with the wall of the descending drying tube. The gas distribution assembly includes a hollow shell. The longitudinal section of the upper half of the shell is trapezoidal, and the longitudinal section of the lower half is cylindrical. The overall longitudinal section of the shell is torch-shaped. A gas inlet is provided at the bottom of the lower half, and the upper surface of the upper half is covered with through holes as gas outlets, forming a gas chamber in the space between the upper and lower halves. The material conveying assembly includes a feed box and two air-tight feeders respectively arranged above and below the feed box outlet; a surface elastic roller is arranged at the feed box outlet and between the two air-tight feeders, and a gas distribution device is arranged downstream of the surface elastic roller, with the gas outlet of the gas distribution device facing the inlet of the lifting drying pipe.

2. The system according to claim 1, characterized in that, The free end of the rubber sheet is curved.

3. The system according to claim 1, characterized in that, The feeder and the descending drying tube maintain a flexible seal.

4. The system according to claim 1, characterized in that, The upper edge of the feeder blades is 200-400mm away from the discharge port of the descending drying tube.

5. The system according to claim 1, characterized in that, The air-tight feeder includes a rotatable impeller and a housing that matches the shape of the impeller.

6. The system according to claim 1, characterized in that, The diameter of the descending drying tube is 1.2-1.5 times that of the ascending drying tube.

7. The system according to claim 1, characterized in that, The height of the lowering drying tube is 0.6-0.8 times that of the raising drying tube.

8. A method for drying and sorting plastic materials, characterized in that, The drying and sorting system according to any one of claims 1-7 shall be used.

9. The method according to claim 8, characterized in that, In the lifting and drying tube, the height H (m), gas velocity V (m / s) of the gas distribution component, diameter D (m) of the lifting and drying tube, and gas density ρ (kg / m³) are all considered. 3 The following relationship must be satisfied: H*V 2 / 2 / D*ρ*0.02≤100pa.

10. The method according to claim 9, characterized in that, In the lifting drying tube, the gas velocity is 15m / s-20m / s, the diameter of the lifting drying tube is in the range of DN700-DN800, and the height of the lifting drying tube is in the range of 9.9m-13m.

11. The method according to claim 8, characterized in that, Inside the descending drying tube, the relationship between the tube's diameter and the gas velocity is V = Q / 3600 / (0.785D). 2 ), Q(m) 3 ( / h) is the gas flow rate, D (m) is the pipe diameter, and V (m / s) is the gas velocity.

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