Grain dryer

Abstract

The utility model relates to a grain dryer which comprises a grain inlet layer, a drying layer, a grain outlet layer, a conveyor and an elevator, the grain inlet layer, the drying layer, the grain outlet layer and the conveyor are sequentially communicated from top to bottom, the conveyor is communicated with the lower end of the elevator, the upper end of the elevator is communicated with the grain inlet layer, and the drying layer comprises a drying shell and an air return fan. A drying cavity, an air inlet cavity, an air outlet cavity and an air return cavity are formed in the drying shell, a plurality of net pipe type air pipes are vertically arranged in the drying cavity at intervals, grains circularly enter the net pipe type air pipes of the drying cavity from top to bottom to be dried under the lifting of a lifting machine, hot air enters the drying cavity from the air inlet cavity and is blown into the drying cavity through an air return fan, and the drying effect is improved. Communicated air outlets are formed between the drying cavity and the air inlet cavity and between the drying cavity and the air outlet cavity, so that part of hot air is blown out of the air outlet cavity, and the other part of hot air is attracted by the air return fan to form hot air backflow. The improved grain dryer is provided with the drying layer, so that the drying layer has the effects of hot air backflow and reduction of impact on grains.

Description

Technical Field

[0001] This utility model relates to the field of grain drying equipment, and in particular to a grain dryer. Background Technology

[0002] A grain dryer is an agricultural machine used to reduce the moisture content of grains (such as rice, wheat, and corn). Its main function is to quickly remove excess moisture from grains by controlling temperature and airflow, preventing mold, sprouting, or pests, thereby extending storage time and maintaining grain quality. Currently, grain dryers generally adopt a horizontal angled box array drying layer structure. A lifting device raises the grain to the top of the drying layer, allowing it to flow downwards and achieve drying. Grain falling from the drying layer is then conveyed back to the lifting device, allowing for continuous circulation through the drying layer. However, the existing horizontal angled box array drying layer structure has limitations in structural design and drawbacks of modular design. These structural design limitations lead to insufficient hot air circulation efficiency. The horizontal angled boxes are arranged in a horizontal matrix within the drying layer, forming grain flow channels between adjacent boxes. Hot air penetrates the grain layer unidirectionally through ventilation holes / gaps on the surface of the corner boxes, achieving basic drying functions. However, due to the horizontal layout, a hot air recirculation path cannot be formed within the drying layer, resulting in low waste heat utilization, increased energy consumption, and mechanical impact that degrades grain quality. The falling grain flow collides directly with the surface of the horizontal corner boxes, especially under high-speed drying conditions. This mechanical impact easily causes damage to the outer skin or internal cracks of grain particles (such as rice and corn), significantly increasing the breakage rate and directly affecting commercial value and storage stability. Because the modular structure creates a contradiction between load-bearing capacity and durability, the horizontal corner boxes are arranged in a modular matrix. A single unit integrates multiple sets of corner boxes, which are then spliced ​​together to form the drying layer. In continuous operation, the unit structure needs to withstand the vertical load of tons of grain and hot air pressure, which can easily lead to local deformation or even fracture due to stress concentration. It has strict requirements for material strength and welding process, which significantly increases the equipment manufacturing cost. In addition, the modular structure also leads to high maintenance costs. The modular design results in poor maintenance fault tolerance: a single corner box failure requires the disassembly of the entire matrix unit. Maintenance work involves large-scale shutdown and structural reorganization, which seriously affects the continuity of production. Utility Model Content

[0003] The purpose of this utility model is to solve the above-mentioned technical problems and provide a grain dryer. The improved grain dryer of this application has a drying layer that enables hot air recirculation and reduces impact on the grain.

[0004] To achieve the above objectives, the technical solution of this utility model is as follows:

[0005] A grain dryer includes a grain inlet layer, a drying layer, a grain outlet layer, a conveyor, and an elevator. The grain inlet layer, drying layer, grain outlet layer, and conveyor are connected sequentially from top to bottom. The conveyor connects to the lower end of the elevator, and the upper end of the elevator connects to the grain inlet layer. The drying layer includes a drying shell and a return air fan. The drying shell has a drying chamber, an air inlet chamber, an air outlet chamber, and a return air chamber. The drying chamber is equipped with multiple vertically spaced mesh-type air ducts. Under the lifting action of the elevator, the grain circulates from top to bottom into the mesh-type air ducts of the drying chamber for drying. A return air inlet is provided between the air chamber and the return air chamber. The return air fan is installed at the return air inlet. A first air inlet is provided between the return air chamber and the drying chamber. The upper end of a portion of the mesh-type air duct is connected to the first air inlet, so that hot air enters from the air inlet and is blown into the drying chamber by the return air fan. An air outlet is provided between the drying chamber and both the air inlet and the air outlet. The lower end of another portion of the mesh-type air duct is connected to the air inlet and the air outlet respectively through the air outlet, so that some hot air is blown out from the air outlet and the other portion of hot air is drawn in by the return air fan to form a hot air recirculation.

[0006] According to the grain dryer of this application, the horizontal corner boxes in the drying layer are omitted, and a new drying air duct structure is provided. The grain can fall directly without colliding with the vertically arranged mesh-type air duct, reducing the number of collisions between the grain and hard objects, avoiding damage to the grain under external force during the drying process, and reducing the grain breakage rate. Furthermore, since there are no horizontal corner boxes, the load-bearing and durability problems caused by horizontal corner boxes are also avoided. Hot air is blown in from the air inlet cavity and blown in from the upper end of the mesh-type air duct under the traction of the return air fan. The hot air is blown between the grains through the mesh holes on the mesh-type air duct to dry the grains. Afterward, the hot air with moisture is blown out from the air outlet. Part of the hot air is blown out from the air outlet cavity, and the other part of the hot air is drawn by the return air fan to form a hot air return flow to circulate and dry the grains in the drying layer. Therefore, the new drying air duct structure of this application has the advantages of saving heat, increasing the drying rate, and ensuring grain quality.

[0007] Furthermore, the drying housing includes a drying frame, an air inlet frame, an air outlet frame, and a return air frame. The drying chamber, air inlet chamber, air outlet chamber, and return air chamber are correspondingly arranged in the drying frame, air inlet frame, air outlet frame, and return air frame. The drying frame has a first side and a second side arranged opposite to each other. The air inlet frame and the return air frame are arranged on the first side, and the return air frame is arranged on the upper part of the air inlet frame. The first air inlet is arranged on the first side, the air outlet frame is arranged on the second side, and the air outlet is arranged on the first side and the second side.

[0008] Furthermore, it also includes an upper mounting base and a lower mounting base, with both ends of the upper and lower mounting bases fixed to a first side and a second side. The mesh-type air duct includes a mesh-type inlet pipe and a mesh-type outlet pipe. The upper end of the mesh-type inlet pipe is connected to a first air inlet, and the lower end of the mesh-type outlet pipe is connected to an air outlet. The upper end of the mesh-type inlet pipe is fixed to the upper mounting base, and the lower mounting base is provided with a plug-in post. The lower end of the mesh-type outlet pipe is plugged into the plug-in post. Hot air enters from the upper end of the mesh-type inlet pipe and diffuses through the mesh holes in the pipe wall into the grain between the mesh-type air ducts to dry the grain. After drying, the moist hot air enters through the mesh holes in the pipe wall of the mesh-type outlet pipe and exits from the outlet of the drying chamber.

[0009] Furthermore, a first mesh plate is provided on the first and second sides, connecting the drying chamber to the air inlet and air outlet chambers. The air inlet chamber has a second air inlet, and a guide plate is provided inside the air inlet. The second air inlet is opposite to the guide plate, guiding the hot air entering through the second air inlet to the return air fan. The humid hot air after drying the grain can also enter the air inlet or air outlet chamber through the mesh of the first mesh plate, improving the ventilation effect of the drying chamber.

[0010] Furthermore, it also includes a damper actuator and a temperature sensor. The temperature sensor senses the drying temperature within the drying layer, and the damper actuator is mounted on the air inlet frame. The damper actuator controls its opening degree based on the drying temperature. Overheating can occur in the drying layer during drying, especially when multiple grain dryers are used in tandem. Excessive temperature leads to a decline in grain quality. By coordinating the damper actuator and temperature sensor, when the drying temperature is detected to be too high, the damper actuator opens, allowing cooler outside air to enter the drying layer, thereby lowering the drying temperature and ensuring the quality of the dried grain.

[0011] Furthermore, the drying frame also has a third side and a fourth side arranged opposite to each other, and the third side and the fourth side are provided with drying mesh frames. The drying mesh frames are connected to the first side and the second side, and the outer side of the drying mesh frames is provided with an observation cover. The drying mesh frames can increase the ventilation effect of the drying layer, and the observation cover can facilitate the observation of the state of the grain in the drying layer.

[0012] Furthermore, it also includes duct connectors that connect adjacent mesh-type ducts. These duct connectors can make the structure of the mesh-type duct more stable.

[0013] Furthermore, the air outlet cavity is equipped with an air outlet fan, and the air outlet fan and the return air fan have the same power and the ratio of the number of air outlet fans to return air fans is 2:3.

[0014] Furthermore, the top of the drying chamber is provided with a conical top, which is positioned above the mesh-type air duct. The conical top allows the grain to smoothly enter between the mesh-type air ducts.

[0015] Furthermore, the grain feeding layer is provided with multiple unit frames, adjacent unit frames are spliced ​​together vertically, and fixed tie rods are provided on the opposite sides of the unit frames, and the height of the unit frames is 600-610mm.

[0016] Furthermore, the bottom of the drying layer has an outlet, and the grain discharge layer is provided with a collection funnel at the corresponding outlet position, and a grain feeding wheel is provided at the outlet of the collection funnel. Attached Figure Description

[0017] Figure 1 This is a perspective view of the grain dryer of this utility model.

[0018] Figure 2 This is a cross-sectional view of the grain dryer of this utility model.

[0019] Figure 3 for Figure 2 A magnified view of a portion of the image.

[0020] Figure 4 This is a perspective view of the unit frame of this utility model.

[0021] Figure 5 This is a perspective view of the drying layer of the grain dryer of this utility model.

[0022] Figure 6 This is an exploded view of the drying layer of the grain dryer of this utility model.

[0023] Figure 7 This is an exploded view of the drying frame of the grain dryer of this utility model.

[0024] Figure 8 This is a perspective view of the grain discharge layer and conveyor of the grain dryer of this utility model.

[0025] Figure 9 This is a schematic diagram of the structure of the hot air furnace of this utility model supplying hot air to the grain dryer.

[0026] Figure 10 This is a schematic diagram of the airflow path of the grain dryer of this utility model. Detailed Implementation

[0027] The present invention relates to a grain dryer, which is described in conjunction with the accompanying drawings.

[0028] like Figures 1 to 10The grain dryer shown includes a grain inlet layer 1, a drying layer, a grain outlet layer 3, a conveyor 4, and an elevator 5. The grain inlet layer 1, drying layer, grain outlet layer 3, and conveyor 4 are connected sequentially from top to bottom. The output port 41 of the conveyor 4 is connected to the lower end of the elevator 5. The elevator 5 also has a grain inlet 51 at its lower end, which allows for convenient feeding of grain to be dried into the grain dryer. The upper end of the elevator 5 has multiple outlets connected to the grain inlet layer via a circulation port 53. The upper end of the elevator 5 also has a grain outlet 52, which allows the dried grain to be discharged from the grain dryer under the lifting action of the elevator 5. The grain circulates through the drying layer in the grain dryer, ensuring even drying and preventing breakage due to prolonged heating. The drying layer includes a drying shell 2 and a return air fan 7. The drying shell 2 contains a drying chamber, an air inlet chamber, an air outlet chamber, and a return air chamber. The drying chamber is equipped with multiple vertically spaced mesh-type air ducts 25. Lifted by the elevator 5, the grain circulates from top to bottom into the mesh-type air ducts 25 for drying. The grain falls directly without colliding with the vertically arranged mesh-type air ducts 25, reducing the number of collisions between the grain and hard objects and preventing grain breakage during the drying process. Damage caused by external force will reduce the grain breakage rate. A return air inlet 223 is provided between the air inlet and return air chambers. The return air fan 7 is installed at the return air inlet 223. A first air inlet 215 is provided between the return air chamber and the drying chamber. A portion of the upper end of the mesh-type air duct 25 is connected to the first air inlet 215, allowing hot air to enter from the air inlet chamber and be blown into the drying chamber by the return air fan 7. The drying chamber is connected to both the air inlet and outlet chambers by air outlets (2112, 2122). Another portion of the lower end of the mesh-type air duct 25 is connected to the air inlet chamber via air outlets (2112, 2122). The air outlet is connected to the air inlet chamber, so that part of the hot air is blown out from the air outlet chamber, and the other part of the hot air is drawn by the return air fan 7 to form a hot air recirculation. The grain dryer generates heat through the hot air furnace, and the hot air furnace and the air inlet chamber are connected by the induced draft fan. The induced draft fan draws the hot air into the air inlet chamber, and under the traction of the return air fan 7, it is blown into the upper end of the mesh-type air duct 25. The air is blown into the grain through the mesh holes on the pipe wall of the mesh-type air duct 25 to dry the grain. After that, the moist hot air is blown out from the air outlet (2112, 2122). Part of the hot air is blown out from the air outlet chamber, and the other part of the hot air is drawn by the return air fan 7 to directly form a hot air recirculation in the drying layer to circulate and dry the grain in the drying chamber.

[0029] like Figures 5 to 7As shown, the drying housing 2 includes a drying frame 21, an air inlet frame 22, an air outlet frame 23, and a return air frame 24. The drying chamber, air inlet chamber, air outlet chamber, and return air chamber are respectively arranged in the drying frame 21, air inlet frame 22, air outlet frame 23, and return air frame 24. The drying frame 21 has a first side 211 and a second side 212 arranged opposite to each other. The air inlet frame 22 and the return air frame 24 are arranged on the first side 211, and the return air frame 24 is arranged on the upper part of the air inlet frame 22. The first air inlet 215 is arranged on the first side 211, the air outlet frame 23 is arranged on the second side 212, and the air outlet (2112, 2122) is arranged on the first side 211 and the second side 212.

[0030] The mesh-type air duct 25 includes a mesh-type air inlet duct 251 and a mesh-type air outlet duct 252. The upper end of the mesh-type air inlet duct 251 is connected to the first air inlet 215, and the lower end of the mesh-type air outlet duct 252 is connected to the air outlet (2112, 2122). Hot air enters from the upper end of the mesh-type air inlet duct 251 and diffuses into the grain between the mesh-type air ducts 25 through the mesh holes in the pipe wall of the mesh-type air inlet duct 251 to dry the grain. After drying, the humid hot air enters from the mesh holes in the pipe wall of the mesh-type air outlet duct 252 and is discharged from the drying chamber through the air outlet (2112, 2122). The mesh-type air inlet duct 251 is arranged in three rows, and the mesh-type air outlet duct 252 is arranged in two rows, with the two rows of mesh-type air outlet ducts 252 spaced apart between the three rows of mesh-type air inlet ducts 251.

[0031] like Figures 5 to 7 As shown, it also includes an upper mounting base 27 and a lower mounting base 28. There are three upper mounting bases 27 and two lower mounting bases 28. The two ends of the upper mounting base 27 and the lower mounting base 28 are fixed to the first side surface 211 and the second side surface 212 by bolts. The upper end of the mesh-type air inlet pipe 251 is fixed to the upper mounting base 27 by bolts. The lower mounting base 28 is provided with a plug-in post. The lower end of the mesh-type air outlet pipe 252 is inserted into the plug-in post. A channel is formed in the lower mounting base 28 to connect the air outlet (2112, 2122) and the lower end of the mesh-type air outlet pipe 252.

[0032] like Figures 6 to 7As shown, a first mesh plate (2111, 2121) is provided on the first side 211 and the second side 212. The mesh holes on the first mesh plate (2111, 2121) connect the drying chamber with the air inlet chamber and the air outlet chamber. The air inlet chamber has a second air inlet 221. A guide plate 222 is provided inside the air inlet chamber. The second air inlet 221 is opposite to the guide plate 222, which guides the hot air entering through the second air inlet 221 to the return air fan 7. The humid hot air after drying the grain can also come out from the first mesh plate. The mesh openings (2111, 2121) allow hot air to enter the air inlet or outlet chamber, improving the ventilation effect of the drying chamber. The induced draft fan of the hot air furnace is opposite to the second air inlet 221, thus blowing hot air into the air inlet chamber. The guide plate 222 can guide the hot air blown into the air inlet chamber toward the return air fan 7. Furthermore, the air outlet (2112, 2122) connected to the air inlet chamber also faces the guide plate 222. The guide plate 222 guides the returning hot air toward the return air fan 7, thus forming a hot air return flow within the drying layer.

[0033] like Figure 1 As shown, it also includes a damper actuator 6 and a temperature sensor. Both the damper actuator 6 and the temperature sensor are commercially available products. The damper actuator 6 is preferably a multi-leaf damper. The temperature sensor is used to sense the drying temperature in the drying layer. The damper actuator 6 is installed on the air inlet frame 22. The damper actuator 6 controls the opening degree according to the drying temperature. The drying layer may experience excessively high temperatures during drying, especially when multiple grain dryers are used in tandem. This problem can lead to a decline in grain quality. To address this, the damper actuator 6, in conjunction with a temperature sensor, opens when the drying temperature is detected as too high, allowing cooler outside air to enter the drying layer and thus lowering the drying temperature. This ensures the quality of the dried grain. A suitable drying temperature is crucial for optimal grain quality. Before drying, a stable drying temperature (hereinafter referred to as the set temperature) is set. Air intake begins at the start of drying. Since the temperature in the drying layer has not yet reached the set temperature, the damper actuator 6 remains closed. Once the set temperature is reached, the damper actuator opens, allowing cool air to enter the drying layer. If the drying temperature continues to rise, the opening of the damper actuator 6 is further increased; conversely, if the temperature continues to rise, the opening of the damper actuator 6 is decreased.

[0034] like Figure 7As shown, the drying frame 21 is generally rectangular. The drying frame 21 also has a third side 213 and a fourth side 214 arranged opposite to each other. The third side 213 and the fourth side 214 are provided with a drying mesh frame 26. The drying mesh frame 26 is connected to the first side 211 and the second side 212. The outer side of the drying mesh frame 26 is provided with an observation cover 261. The observation cover 261 is a detachable cover or a transparent cover, so that the state of the grain in the drying layer can be easily observed. The drying mesh frame 26 also includes a second mesh plate 263 and a frame 262. The second mesh plate 263 can be ventilated and does not affect the observation cover 261 to observe the state of the grain. The frame 262 provides support for the second mesh plate 263 and forms a ventilation space.

[0035] like Figure 2 As shown, the air outlet cavity is equipped with an air outlet fan 8. The air outlet fan 8 and the return air fan 7 have the same power and the quantity ratio is air outlet fan 8: return air fan 7 = 2:3, which can ensure that the air force generated by the return air fan 7 is greater than the air outlet air force of the air outlet cavity. According to the attached drawings, it can be determined that in the embodiment shown in the attached drawings of this application, there are 3 return air fans 7 and 2 air outlet fans 8.

[0036] like Figure 2 and Figure 4 As shown, the top of the drying chamber is provided with a conical top 29, which is set on the mesh-type air duct 25. The conical top 29 allows the grain to enter smoothly between the mesh-type air ducts 25. There are two sizes of conical tops 29. There are three larger conical tops 29, which cover the upper mounting base 27 of the three rows of mesh-type air inlet pipes 251 and form a channel connecting the first air inlet 215 and the upper end of the mesh-type air inlet pipes 251. There are two smaller conical tops 29, which cover the two rows of mesh-type air outlet pipes 252. The top of the lower mounting base 28 is also set as a conical surface to prevent the grain from accumulating on the lower mounting base 28.

[0037] like Figure 4 As shown, the grain inlet layer 1 is provided with multiple unit frames 11, and adjacent unit frames 11 are spliced ​​together vertically. The opposite sides of the unit frames 11 are provided with fixed tie rods 12. The number of tie rods 12 is set according to the density calculation of the grain. The structure of the grain inlet layer 1 is made more stable by the reinforcement of the tie rods 12. In addition, the tie rods 12 are relatively thin and will not cause the grain to be blocked. The height of the unit frame 11 is 600-610mm. Generally, the unit frame is processed from the original board material with a height of 1224mm. Therefore, setting the height of the unit frame 11 to 600-610mm can improve the utilization rate of the board material.

[0038] Multiple tie rods can be provided between the first side 211 and the second side 212 for reinforcement, making the structure of the first side 211 and the second side 212 more stable.

[0039] like Figure 3 and Figure 8 As shown, the bottom of the drying layer has an outlet, and the shell of the drying layer is formed into a large funnel shape. The bottom of the funnel is the outlet. The grain discharge layer 3 is provided with a collection funnel 31 at the corresponding outlet position. A grain feeding wheel 32 is provided at the outlet of the collection funnel 31. A conical top 29 is also provided at the outlet above the collection funnel. The grain is guided into the collection funnel 31 through the conical top 29.

[0040] The mesh size of this application is smaller than that of the grain, so that it can be used for ventilation while preventing the grain from leaking out of the mesh.

[0041] This application also tests the drying structure to verify the effect of the drying structure on improving drying efficiency and reducing energy consumption.

[0042] First group of experiments:

[0043] 1. Experimental Grouping

[0044] Control group: Grain dryer using a traditional transverse corner box drying layer

[0045] Experimental group: Grain dryer using the drying layer of this application.

[0046] 2. Experimental conditions

[0047] Grain type: Rice (initial moisture content 25%)

[0048] Weight: 30 tons

[0049] Target moisture content: 13.5%

[0050] Drying temperature: 65℃

[0051] Air volume: 14000m³ 3 / h (both groups are consistent)

[0052] 3. Data Collection

[0053] Record the time required to reach the target moisture content;

[0054] Measure the energy consumption of the hot blast stove.

[0055] Experimental results:

[0056] Group Drying time (hours) Calories burned (kcal / kg) control group 13.2 4435200 experimental group 9.8 3292800

[0057] Analysis conclusion:

[0058] The experimental group showed a 25.76% increase in drying efficiency and a 25.76% decrease in energy consumption, indicating that the structural design of this application significantly optimizes thermal energy utilization.

[0059] Second group of experiments:

[0060] 1. Experimental Grouping

[0061] Control group: Grain dryer using a traditional transverse corner box drying layer

[0062] Experimental group: Grain dryer using the drying layer of this application.

[0063] 2. Experimental conditions

[0064] Grain type: Rice (initial moisture content 27%)

[0065] Weight: 28 tons

[0066] Target moisture content: 14%

[0067] Drying temperature: 65℃

[0068] Air volume: 14000m³ 3 / h (both groups are consistent)

[0069] 3. Data Collection

[0070] Record the time required to reach the target moisture content;

[0071] Measure the energy consumption of the hot blast stove.

[0072] Experimental results:

[0073] Group Drying time (hours) Calories burned (kcal / kg) control group 15.1 5073600 experimental group 11.3 3796800

[0074] Analysis Conclusion

[0075] The experimental group showed a 25.16% increase in drying efficiency and a 25.16% decrease in energy consumption, indicating that the structural design of this application significantly optimizes thermal energy utilization.

[0076] Based on the disclosure and teachings of the above specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, this utility model is not limited to the specific embodiments disclosed and described above, and some modifications and changes to this utility model should also fall within the protection scope of the claims of this utility model. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on this utility model.

Claims

1. A grain dryer, characterized by The application relates to a grain drying device, which comprises a grain inlet layer, a drying layer, a grain outlet layer, a conveyor and a hoist, wherein the grain inlet layer, the drying layer, the grain outlet layer and the conveyor are sequentially communicated from top to bottom, the lower end of the conveyor is communicated with the hoist, the upper end of the hoist is communicated with the grain inlet layer, the drying layer comprises a drying shell and a return air fan, the drying shell is internally provided with a drying cavity, an air inlet cavity, an air outlet cavity and a return air cavity, a plurality of net tube type air pipes are vertically and spacedly arranged in the drying cavity, and the grain is circulated into the net tube type air pipes in the drying cavity under the hoisting of the hoist and is dried, a return air port is arranged between the air inlet cavity and the return air cavity and is communicated with the air inlet cavity and the return air cavity, the return air fan is installed at the return air port, a first air inlet port is arranged between the return air cavity and the drying cavity, the upper ends of some of the net tube type air pipes are communicated with the first air inlet port, hot air is led into the air inlet cavity and is blown into the drying cavity by the return air fan, air outlets are arranged between the drying cavity and the air inlet cavity and the air outlet cavity and are communicated with the drying cavity, the air inlet cavity and the air outlet cavity, the lower ends of the other net tube type air pipes are respectively communicated with the air inlet cavity and the air outlet cavity through the air outlets, part of the hot air is blown out of the air outlet cavity, and the other part of the hot air is sucked by the return air fan to form a hot air return flow.

2. The grain dryer of claim 1, wherein, The drying shell comprises a drying frame, an air inlet frame, an air outlet frame and a return air frame, the drying cavity, the air inlet cavity, the air outlet cavity and the return air cavity are correspondingly arranged in the drying frame, the air inlet frame, the air outlet frame and the return air frame, the drying frame is provided with oppositely arranged first and second side faces, the air inlet frame and the return air frame are arranged on the first side face, the return air frame is arranged on the upper portion of the air inlet frame, the first air inlet port is arranged on the first side face, the air outlet frame is arranged on the second side face, and the air outlets are arranged on the first and second side faces.

3. The grain dryer of claim 2, wherein, The device further comprises upper and lower mounting seats, the two ends of the upper and lower mounting seats are fixed on the first and second side faces, the net tube type air pipes comprise net tube type air inlet pipes and net tube type air outlet pipes, the upper ends of the net tube type air inlet pipes are communicated with the first air inlet port, the lower ends of the net tube type air outlet pipes are communicated with the air outlets, the upper ends of the net tube type air inlet pipes are fixed on the upper mounting seat, the lower mounting seat is provided with plug-in columns, and the lower ends of the net tube type air outlet pipes are plug-in installed in the plug-in columns.

4. The grain dryer of claim 2, wherein, The first and second side faces are provided with first net plates, the first net plates communicate the drying cavity with the air inlet cavity and the air outlet cavity, the air inlet cavity is provided with a guide plate, the second air inlet port is opposite to the guide plate, and the hot air entering the second air inlet port is guided to the return air fan.

5. The grain dryer of claim 2, wherein, The device further comprises a damper actuator and a temperature sensor, the temperature sensor is used for sensing the drying temperature in the drying layer, the damper actuator is arranged on the air inlet frame, and the damper actuator controls the opening degree according to the drying temperature.

6. The grain dryer of claim 2, wherein, The drying frame is further provided with oppositely arranged third and fourth side faces, the third and fourth side faces are provided with drying net racks, the drying net racks are communicated with the first and second side faces, and the outer side faces of the drying net racks are provided with observation covers.

7. The grain dryer of claim 1, wherein, The air outlet cavity is provided with an air outlet fan, and the power of the air outlet fan is same as that of the air return fan, and the quantity ratio is air outlet fan: air return fan=2:

3.

8. The grain dryer of claim 1, wherein, The top of the drying cavity is provided with a conical top, which is arranged above the net tube type air pipe.

9. The grain dryer of claim 1, wherein, The grain inlet layer is provided with a plurality of unit frame bodies, adjacent unit frame bodies are spliced together, opposite sides of the unit frame body are provided with fixed pull rods, and the height of the unit frame body is 600-610mm.

10. The grain dryer of claim 1, wherein, The bottom of the drying layer is provided with an outlet, the grain outlet layer is provided with a collecting hopper at a position corresponding to the outlet, and the collecting hopper is provided with a grain stirring wheel at an outlet thereof.

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