Grain vacuum heat pump drying system

Abstract

The utility model discloses a grain vacuum heat pump drying system which comprises a drying machine, a heat pump unit and a generator set, a grain drying cavity and a water vapor leading-out cavity are defined in the drying machine, and a heat transfer pipeline and an angular box are arranged in an inner cavity of the grain drying cavity. The heat pump unit comprises a compressor, a condenser, an expansion valve and an evaporator which are sequentially connected through pipelines, one end of the heat transfer pipeline is connected with the water outlet end of the condenser through a first pipeline, and the water inlet end of the condenser is connected with the cooling water outlet end of the generator unit through a second pipeline. The other end of the heat transfer pipeline is connected with the cooling water backflow end of the generator set through a hot water backflow pipe. The two ends of the angular box penetrate out of the grain drying cavity and communicate with the water vapor guiding-out cavity, an air extraction opening communicating with the water vapor guiding-out cavity is formed in the bottom of the drying machine, and the air extraction opening is connected with an air extraction device. The grain dryer can be used for quickly drying grains according to user requirements, and has the advantages of energy conservation, environmental protection and reliable performance.

Description

TECHNICAL FIELD

[0001] The utility model relates to grain drying treatment technical field especially relates to a grain vacuum heat pump drying system. BACKGROUND

[0002] In order to be able to long-term preservation of grain, need to carry out drying treatment to grain before storing grain, currently, grain drying equipment is generally used to carry out drying treatment to grain, conventional grain drying equipment usually adopts the mode of blowing hot air to realize drying grain treatment, for example, the utility model CN221649071U discloses a heat energy circulation type grain drying tower, which adopts hot steam to dry grain, and there are problems of large energy consumption, large heat loss, easy dust production and the like. UTILITY MODEL CONTENTS

[0003] The utility model discloses a grain vacuum heat pump drying system can carry out quick drying treatment to grain according to user requirement, has the advantages of energy saving and environmental protection, reliable performance, solves the problems of large heat loss, high temperature and poor quality of conventional grain drying machine.

[0004] In order to realize the above-mentioned purpose, the utility model adopts the following technical scheme:

[0005] A grain vacuum heat pump drying system, including dryer, heat pump unit and generator unit, the dryer includes shell and inner shell, the inner shell surrounds and forms grain drying chamber, the shell with the inner shell forms the water vapor export cavity between, the inner chamber of grain drying chamber is equipped with heat transfer pipeline and a plurality of bottom open angle box, the heat pump unit includes the compressor, condenser, expansion valve and evaporator connected in proper order through pipeline, the both ends of heat transfer pipeline are connected with hot water input end and hot water return end respectively, the hot water input end is connected with the water outlet of condenser through first pipeline, the water inlet of condenser is connected with the cooling water outlet of generator unit through second pipeline, the hot water return end is connected with the cooling water return end of generator unit through hot water return pipe, the second pipeline is installed with first valve, the hot water return pipe is installed with second valve, the second pipeline between first valve and condenser is connected with hot water return pipe between second valve and heat transfer pipeline through third valve, the both ends of angle box respectively wear out grain drying chamber and communicate with water vapor export cavity, the bottom of dryer is provided with the air extraction port that communicates with water vapor export cavity, the air extraction port is connected with the air extraction device.

[0006] Further, the air extraction device includes a first exhaust pipe connected to the air inlet of the evaporator, a second exhaust pipe connected to the air outlet of the evaporator, and a vacuum pump installed on the second exhaust pipe.

[0007] Further, the first exhaust pipe is provided with a fourth valve, the second exhaust pipe is provided with a first pressure sensor, and the dryer is provided with a second pressure sensor and a temperature sensor.

[0008] Further, the evaporator is a water-cooled evaporator, which comprises a cooling cavity provided with cooling water and an evaporating coil located in the cooling cavity, a water spraying head is arranged at the upper portion of the cooling cavity, a water spraying pipe connected with the water spraying head is arranged at the lower portion of the cooling cavity, a cooling water circulating pump is arranged in the water spraying pipe, and the first exhaust pipe and the second exhaust pipe are respectively communicated with the cooling cavity.

[0009] Further, the angular boxes are arranged in layers along the height direction of the dryer, and each layer of the angular boxes is arranged with a plurality of angular boxes in the horizontal direction.

[0010] Further, the heat transfer pipe comprises a first vertical pipe, a second vertical pipe, a third vertical pipe and a plurality of serpentine pipes, the bottom end of the first vertical pipe is connected with the hot water input end, the top end of the second vertical pipe is connected with the hot water return end, and a plurality of serpentine pipes are respectively connected between the first vertical pipe and the third vertical pipe and between the second vertical pipe and the third vertical pipe.

[0011] Further, the serpentine pipes and the angular boxes are arranged in layers and staggered.

[0012] Further, the top portion of the inner shell is provided with a feeding port communicated with the grain drying cavity, the bottom portion of the inner shell is provided with a discharging port communicated with the grain drying cavity, and the inside of the dryer is provided with an elevator vertically distributed, the upper portion of the elevator is connected with a feeding channel communicated with the feeding port, and the lower portion of the elevator is connected with a discharging channel communicated with the discharging port.

[0013] Further, the feeding channel and the discharging channel are horizontally distributed, the feeding channel is provided with a feeding screw device, the discharging channel is provided with a discharging screw device, the lower portion of the elevator is respectively provided with a grain feeding port and a grain return port at both sides, the bottom portion of the end of the discharging channel close to the elevator is communicated with the grain return port, and the bottom portion of the end of the feeding channel close to the elevator is provided with a grain discharging port and a gate device arranged at the grain discharging port.

[0014] Further, the lower portion of the inner shell is provided with a lower hopper located above the discharging port, the upper portion of the lower hopper is communicated with the grain drying cavity, the lower portion of the lower hopper is communicated with the discharging channel, the lower hopper is provided with a plurality of guide members distributed at intervals, a rotating grain pushing wheel is arranged between two adjacent guide members, and the dryer is provided with a grain pushing driving mechanism for driving the rotation of the grain pushing wheel.

[0015] Compared with the prior art, the grain vacuum heat pump drying system has the following beneficial effects:

[0016] The utility model discloses adopt generator set output electric energy to heat pump unit and drying machine work, utilize generator set cooling water to give system temperature rise, reach target temperature by heat pump unit to material indirect heating. Heating medium hot water is indirectly transferred to material by heat transfer pipeline and realizes water evaporation, and water is guided and discharged by the angular box in grain drying cavity under the low vacuum condition formed by the suction of the air extraction device, and the effective moisture diffusion coefficient of rice increases with the increase of temperature, thereby the water in material is quickly separated, and the separated water is discharged after evaporator cooling and dehumidification under the action of vacuum pump, and the evaporator adopts water cooling circulation process, and the latent heat released by water condensation is recovered when cooling and dehumidifying to work for heat pump unit, and heat recovery is more energy-saving.

[0017] In addition, the material realizes the internal circulation of material in the drying machine by the grain wheel, the discharge screw device, the elevator and the feeding screw device, guarantees that the material is uniformly and fully heated and heated, to meet the uniformity requirement of material drying.

[0018] The utility model is driven by electric energy, and the energy saving can be more than 40% by adopting vacuum drying and condensation dehumidification technology, the gas zero emission in the vacuum air extraction drying process, and the environmental pollution is not produced, and the green drying energy-saving and environmental protection are realized, and the additional dust treatment system is not needed. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical scheme in the embodiment of the utility model or prior art, the following will briefly introduce the drawing needed to be used in the embodiment or prior art description, and obviously, the drawing in the following description is only some embodiments of the utility model, and for ordinary skilled person in the art, other drawings can be obtained according to these drawings without paying the creative labor.

[0020] Figure 1 It is the structure schematic drawing of the utility model;

[0021] Figure 2 It is the structure schematic drawing of the drying machine;

[0022] Figure 3 It is the structure schematic drawing of the inner shell;

[0023] Figure 4 It is the three-dimensional structure schematic drawing of the elevator;

[0024] Figure 5 It is the side view structure schematic drawing of the elevator;

[0025] Figure 6 It is the half cross section structure schematic drawing of the elevator;

[0026] Figure 7 This is a schematic diagram of the assembly of the gate device and the feeding channel;

[0027] Figure 8 This is a schematic diagram of the assembly of the feeding screw device and the feeding channel;

[0028] Figure 9 This is a schematic diagram showing the connection between the grain feeding wheel and the grain feeding wheel drive mechanism.

[0029] Figure 10 This is a three-dimensional structural diagram of the grain-dispensing reel.

[0030] Reference numerals: 1. Dryer; 11. Outer shell; 111. Exhaust port; 12. Inner shell; 121. Feed inlet; 122. Discharge outlet; 123. Hopper; 124. Grain guide; 125. Grain feeding wheel; 13. Grain drying chamber; 14. Water vapor outlet chamber; 15. Heat transfer pipe; 151. Hot water input end; 152. Hot water return end; 153. First vertical pipe; 154. Second vertical pipe; 155. Third vertical pipe; 156. Serpentine pipe; 16. Angle box; 17. Second pressure sensor; 18. Temperature sensor; 19. Grain feeding wheel drive mechanism; 2. Heat pump unit; 21. Compressor; 22. Condenser; 23. Expansion valve; 24. Evaporator; 241. Cooling chamber; 242. Evaporation coil; 243. Spray nozzle; 244. Spray pipe; 245. Cooling water circulation. 1. Pump; 2. Generator set; 3. First pipeline; 4. Second pipeline; 5. First valve; 6. Hot water return pipe; 7. Second valve; 8. Third valve; 9. Air extraction device; 10. First exhaust pipe; 11. Second exhaust pipe; 12. Vacuum pump; 13. Fourth valve; 14. First pressure sensor; 15. Elevator; 16. Elevator housing; 17. Grain inlet; 18. Grain return outlet; 19. Upper impeller assembly; 20. Lower impeller assembly; 21. Belt; 32. Bucket; 43. Drive motor; 54. Chain and sprocket transmission assembly; 65. Feeding channel; 76. Feeding screw device; 87. Grain outlet; 88. Discharge channel; 89. Discharge screw device; 90. Gate device; 11. Pneumatic gate; 12. Cylinder; 13. Cylinder mounting base. Detailed Implementation

[0031] The technical solution of this utility model will be clearly and completely described below through detailed embodiments and in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0032] Please refer toFigures 1-10 The embodiment provides a grain vacuum heat pump drying system, which comprises a drying machine 1, a heat pump unit 2 and a generator set 3. The drying machine 1 comprises an outer shell 11 and an inner shell 12, the inner shell 12 surrounds a grain drying cavity 13, a water vapor leading-out cavity 14 is formed between the outer shell 11 and the inner shell 12, a heat transfer pipeline 15 and a plurality of bottom-opened angular boxes 16 are arranged in the inner cavity of the grain drying cavity 13. The heat pump unit 2 comprises a compressor 21, a condenser 22, an expansion valve 23 and an evaporator 24 which are sequentially connected through pipelines. The heat transfer pipeline 15 is respectively connected with a hot water input end 151 and a hot water return end 152. The hot water input end 151 is connected with a water outlet end of the condenser 22 through a first pipeline 4. A water inlet end of the condenser 22 is connected with a cooling water outlet end of the generator set 3 through a second pipeline 5. The hot water return end 152 is connected with a cooling water return end of the generator set 3 through a hot water return pipeline 6. The second pipeline 5 is provided with a first valve 51. The hot water return pipeline 6 is provided with a second valve 61. The second pipeline between the first valve 51 and the condenser 22 is connected with the hot water return pipeline between the second valve 61 and the heat transfer pipeline 15 through a third valve 62. The two ends of the angular box 16 respectively pass through the grain drying cavity 13 and are communicated with the water vapor leading-out cavity 14. The bottom of the drying machine 1 is provided with an air suction port 111 which is communicated with the water vapor leading-out cavity 14. The air suction port 111 is connected with an air suction device 7.

[0033] The generator set outputs electric energy for the heat pump unit and the drying machine to work. The cooling water of the generator set is used to heat the system to reach the target temperature. Then the heat pump unit indirectly heats the materials. The heating medium hot water indirectly transmits heat to the materials through the heat transfer pipeline to evaporate the water. The water is guided and discharged by the angular box in the grain drying cavity. Under the low vacuum condition formed by the suction force of the air suction device, the effective water diffusion coefficient of the rice increases with the increase of the temperature, so that the water in the materials is quickly separated out. The separated water is discharged after being cooled and dehumidified by the evaporator. The evaporator adopts the water cooling circulation process. When the water is cooled and dehumidified, the latent heat released by the condensation of the water is recovered to work for the heat pump unit, so that the heat recovery is more energy-saving.

[0034] In some specific embodiments, such as Figure 1As shown, the air extraction device 7 includes a first exhaust pipe 71 connected to the air inlet end of the evaporator 24, a second exhaust pipe 72 connected to the air outlet end of the evaporator 24, and a vacuum pump 73 installed on the second exhaust pipe 72. In this way, under the low vacuum condition of negative pressure formed in the water vapor extraction chamber and the grain drying chamber by the suction of the vacuum pump, the water in the material can be quickly separated and discharged. The first exhaust pipe 71 is provided with a fourth valve 74, the second exhaust pipe 72 is provided with a first pressure sensor 75, and the drying machine 1 is provided with a second pressure sensor 17 and a temperature sensor 18. By monitoring the air pressure and temperature, the operation of the vacuum pump, the heat pump unit and the generator set can be better controlled.

[0035] In some specific embodiments, as shown in Figure 1 As shown, the evaporator 24 is a water-cooled evaporator, which includes a cooling chamber 241 in which cooling water is stored, and an evaporating coil 242 located in the cooling chamber 241. The upper part of the cooling chamber 241 is provided with a water spraying head 243, and the lower part of the cooling chamber 241 is provided with a water spraying pipe 244 connected to the water spraying head 243. The water spraying pipe 244 is installed with a cooling water circulating pump 245, and the first exhaust pipe 71 and the second exhaust pipe 72 are respectively communicated with the cooling chamber 241. Cooling and dehumidification are achieved by water-cooled circulation, and gas zero emission is achieved, which does not pollute the environment and does not require an additional dust treatment system.

[0036] In some specific embodiments, as shown in Figures 1-3 The angular boxes 16 are arranged in layers along the height direction of the drying machine 1, and each layer of angular boxes 16 is arranged with a plurality of angular boxes 16 in the horizontal direction, so that the material can be heated more uniformly. Specifically, the angular box 16 includes an integrally formed triangular pipe and a rectangular pipe, which are in communication with each other. The two ends and the bottom of the angular box are open. By arranging the angular box, when the grain falls, it can contact the inclined surface of the angular box and be scattered, which can slow down the falling speed of the grain to prolong the residence time of the grain in the grain drying chamber, and on the other hand, since the grain is scattered, it can prevent mutual adhesion and promote the separated water to be discharged outward through the angular box.

[0037] In some specific embodiments, as shown in Figures 1-3The heat transfer pipe 15 comprises a first vertical pipe 153, a second vertical pipe 154, a third vertical pipe 155 and a plurality of serpentine pipes 156. The bottom end of the first vertical pipe 153 is connected with the hot water input end 151, the top end of the second vertical pipe 154 is connected with the hot water return end 152, and a plurality of serpentine pipes 156 are connected between the first vertical pipe 153 and the third vertical pipe 155 and between the second vertical pipe 154 and the third vertical pipe 155, respectively. In this way, the heating medium hot water flows from bottom to top, is input from the first vertical pipe, is branched by a plurality of serpentine pipes, is heated with the grain, is merged into the middle and lower part of the third vertical pipe, is branched again by a plurality of serpentine pipes from the middle and upper part of the third vertical pipe, is heated with the grain, and is finally merged into the second vertical pipe for discharge, so as to ensure that the material can be uniformly and sufficiently heated when the material is internally circulated in the dryer.

[0038] As a preferred embodiment, referring to Figures 1-3 The serpentine pipes 156 and the angular box 16 are arranged in a layered staggered manner. In this way, the grain can be heated more uniformly, and the moisture separated from the heated grain can be quickly discharged.

[0039] In some specific embodiments, the generator set 3 is a diesel generator set, which is connected with a circulating pump in a cooling water pipeline of a heat dissipation device of the generator set 3, so as to drive the cooling water to circulate.

[0040] In some specific embodiments, the condenser 22 is a brazed plate condenser.

[0041] In addition, as an improved embodiment, referring to Figures 1-8 The top of the inner shell 12 is provided with a feeding port 121 which is in communication with the grain drying cavity 13, the bottom of the inner shell 12 is provided with a discharging port 122 which is in communication with the grain drying cavity 13, and the inside of the dryer 1 is provided with an elevator 8 which is distributed in a vertical direction. The upper part of the elevator 8 is connected with a feeding channel 88 which is in communication with the feeding port 121, and the lower part of the elevator 8 is connected with a discharging channel 89 which is in communication with the discharging port 122. Through the elevator, the grain can be lifted in a vertical direction to above the grain drying cavity for the cyclic drying of the grain, so as to improve the grain drying treatment effect.

[0042] In some specific embodiments, referring to Figures 1-8The feeding channel 88 and the discharging channel 89 are horizontally distributed, the feeding channel 88 is provided with a feeding screw device 881, the discharging channel 89 is provided with a discharging screw device 891, the lower part of the elevator 8 is respectively provided with a grain feeding port 811 and a grain return port 812, the bottom of the end of the discharging channel 89 close to the elevator 8 is communicated with the grain return port 812, and the bottom of the end of the feeding channel 88 close to the elevator 8 is provided with a grain discharge port 882 and a gate device 9 installed on the grain discharge port 882. In this way, the grain to be dried can be fed into the grain feeding port, lifted to the feeding channel above by the action of the elevator, and guided into the grain drying cavity by the feeding screw device; the grain falls under its own gravity after entering the grain drying cavity and is heated by the heat transfer pipe, and finally discharged from the discharge port into the grain return port and lifted again by the elevator. When the drying process is completed, the grain can be discharged by opening the gate device.

[0043] In some specific embodiments, with reference to Figure 4 、 Figure 5 and Figure 7 , the gate device 9 comprises a pneumatic gate 91, a pneumatic cylinder 92 and a pneumatic cylinder fixing seat 93, the pneumatic gate 91 is in sliding sealing connection with the grain discharge port 882, the pneumatic cylinder 92 is fixedly installed on the pneumatic cylinder fixing seat 93, and the telescopic end of the pneumatic cylinder 92 is connected with the pneumatic gate 91. In this way, the pneumatic gate is automatically opened by the pneumatic cylinder to discharge the grain after the drying process is completed.

[0044] In some specific embodiments, with reference to Figure 2 、 Figure 4 and Figure 8 , the feeding screw device 881 and the discharging screw device 891 are both single-shaft screw conveyors, which comprise a screw shaft, a speed reducer, a driving sprocket connected with the output end of the speed reducer, and a driven sprocket connected with the screw shaft, and the driven sprocket is connected with the driving sprocket through a chain.

[0045] In some specific embodiments, with reference to Figure 1 、 Figure 2 、 Figures 4-6 , the elevator 8 is a bucket elevator, which comprises an elevator shell 81, an upper rotating wheel assembly 82 rotatably installed in the elevator shell 81, a lower rotating wheel assembly 83 rotatably installed in the elevator shell 81, a belt 84 connected between the upper rotating wheel assembly 82 and the lower rotating wheel assembly 83, a plurality of buckets 85 spacedly installed on the belt 84, a driving motor 86 arranged on the upper part of the elevator shell 81, and a chain and sprocket transmission assembly 87 connected between the output end of the driving motor 86 and the rotating shaft of the upper rotating wheel assembly 82.

[0046] As an improved embodiment, with reference to Figure 3 ,Figure 9 and Figure 10 The lower part of the inner shell 12 is provided with a lower hopper 123 located above the discharge port 122, the upper part of the lower hopper 123 is communicated with the grain drying cavity 13, the lower part of the lower hopper 123 is communicated with the discharge channel 89, the lower hopper 123 is provided with a plurality of interval distributed grain guide members 124, a rotatingly installed grain pushing wheel 125 is arranged between two adjacent grain guide members 124, and the drying machine 1 is provided with a grain pushing driving mechanism 19 for driving the grain pushing wheel 125 to rotate. In this way, under the driving of the grain pushing driving mechanism, the grain pushing wheel can be driven to rotate, so that the grain accumulated in the lower part of the grain drying cavity is pushed downward and falls to the discharge port for discharge.

[0047] In some specific embodiments, referring to Figure 9 The grain guide member 124 is composed of two inclined connected flat plates, and the opening between the two flat plates is downwardly distributed. Referring to Figure 3 and Figure 10 The grain pushing wheel 125 includes a grain pushing shaft and a plurality of blades fixed on the grain pushing shaft. Referring to Figure 9 The grain pushing driving mechanism 19 includes a speed reducer, a driving sprocket connected with the output end of the speed reducer, a driven sprocket connected with the grain pushing wheel, a plurality of guide sprockets rotatably connected with the outer shell, and the driven sprocket and the guide sprockets are connected with the driving sprocket through a chain.

[0048] Referring to Figures 1-10 The working principle of the utility model is as follows: the generator set 3 outputs electric energy to the heat pump set 2 and the drying machine 1 to work, the heat of the heat dissipation device of the generator set 3 is absorbed to heat the water in the heat transfer channel 15 introduced into the drying machine 1 to reach the target temperature, and the heat pump set 2 indirectly heats the material.

[0049] (1) Feeding: the grain material enters the elevator 8 through the grain feeding port 811 in the lower part of the elevator 8, is lifted by the elevator 8 to the upper feeding channel 88, and is sent into the grain drying cavity 13.

[0050] (2) Internal circulation: the material is discharged by the grain pushing wheel 125, is returned to the elevator 8 through the discharge channel 89, and is lifted to the upper part to realize internal circulation.

[0051] (3) Discharge: the material is discharged by the grain pushing wheel 125, is returned to the elevator 8 through the discharge channel 89, is lifted to the feeding channel 88, and is discharged from the grain discharge port 882.

[0052] (4) Water vapor discharge schematic: The grain material falls in the grain drying cavity 13 under its own gravity, and water vapor is separated after heat exchange and heating in the heat transfer channel 15. The heating medium hot water in the heat transfer channel 15 is heated and warmed by the generator set 3, and is indirectly heated by the heat pump set 2 after reaching the target temperature. The separated water vapor is guided and discharged from both sides by the angular box 16 to the water vapor discharge cavity 14, and is extracted by the vacuum pump 73 through the air outlet 111 at the bottom of the drying machine 1, and is discharged after heat exchange and cooling with the cooling medium (water) in the evaporator 24. This process not only allows the circulating water to absorb heat, but also reduces the amount of gas that needs to be treated by the vacuum pump, reduces energy consumption, and prolongs the service life of the equipment.

[0053] (5) The evaporator adopts a water cooling circulation process, and the latent heat released during cooling and dehumidification is recovered to heat the heat pump set, which is more energy-saving.

[0054] (6) In the heat pump set, the low-temperature and low-pressure refrigerant gas is compressed by the compressor 21 and is converted into high-temperature and high-pressure gas, and then enters the condenser 22. The condenser 22 uses water as the cooling medium, and removes heat through water circulation and sends it to the heat transfer pipeline 15 in the drying machine 1, and then heats and warms the grain material through indirect heat conduction through the heat transfer pipeline 15.

[0055] The utility model is driven by electric energy, can save energy by more than 40% by adopting vacuum drying and condensation dehumidification technology, and does not produce environmental pollution in the process of vacuum air extraction drying, is green, energy-saving, environment-friendly, and does not need additional dust treatment system.

[0056] The above embodiments only exemplarily illustrate the concept and technical scheme of the utility model, and are not used to limit the utility model. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and category of the utility model. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the utility model should be covered by the claims of the utility model.

[0057] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description manner of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A grain vacuum heat pump drying system comprising a dryer, a heat pump unit and a generator set, characterized in that, The dryer comprises an outer shell and an inner shell, the inner shell encloses a grain drying cavity, a water vapor leading-out cavity is formed between the outer shell and the inner shell, a heat transfer pipeline and a plurality of bottom-opened corner boxes are arranged in the inner cavity of the grain drying cavity; the heat pump unit comprises a compressor, a condenser, an expansion valve and an evaporator which are connected in sequence by pipelines, the two ends of the heat transfer pipeline are respectively connected with a hot water input end and a hot water return end, the hot water input end is connected with a water outlet end of the condenser through a first pipeline, a water inlet end of the condenser is connected with a cooling water outlet end of the generator set through a second pipeline, the hot water return end is connected with a cooling water return end of the generator set through a hot water return pipeline, the second pipeline is provided with a first valve, the hot water return pipeline is provided with a second valve, the second pipeline between the first valve and the condenser is connected with the hot water return pipeline between the second valve and the heat transfer pipeline through a third valve; the two ends of the corner box respectively pass through the grain drying cavity and are communicated with the water vapor leading-out cavity, the bottom of the dryer is provided with an air extraction port communicated with the water vapor leading-out cavity, and the air extraction port is connected with an air extraction device.

2. The grain vacuum heat pump drying system according to claim 1, characterized in that, The air extraction device comprises a first exhaust pipe connected with an air inlet end of the evaporator, a second exhaust pipe connected with an air outlet end of the evaporator and a vacuum pump installed on the second exhaust pipe.

3. The food vacuum heat pump drying system according to claim 2, characterized in that, The first exhaust pipe is provided with a fourth valve, the second exhaust pipe is provided with a first pressure sensor, and the dryer is provided with a second pressure sensor and a temperature sensor.

4. The food vacuum heat pump drying system according to claim 2, characterized in that, The evaporator is a water-cooled evaporator, which comprises a cooling cavity filled with cooling water and an evaporating coil pipe arranged in the cooling cavity, a water spraying head is arranged at the upper portion of the cooling cavity, a water spraying pipe connected with the water spraying head is arranged at the lower portion of the cooling cavity, a cooling water circulating pump is installed on the water spraying pipe, and the first exhaust pipe and the second exhaust pipe are respectively communicated with the cooling cavity.

5. The food vacuum heat pump drying system according to claim 1, wherein, The corner boxes are arranged in layers along the height direction of the dryer, and a plurality of corner boxes are arranged in each layer along the horizontal direction.

6. The food vacuum heat pump drying system according to claim 5, characterized in that, The heat transfer pipeline comprises a first vertical pipe, a second vertical pipe, a third vertical pipe and a plurality of serpentine pipes, the bottom end of the first vertical pipe is connected with the hot water input end, the top end of the second vertical pipe is connected with the hot water return end, a plurality of serpentine pipes are connected between the first vertical pipe and the third vertical pipe and between the second vertical pipe and the third vertical pipe respectively.

7. The food vacuum heat pump drying system according to claim 6, characterized in that, The serpentine pipes and the corner boxes are arranged in layers and staggered.

8. The system according to any one of claims 1 to 7, wherein, The top of the inner shell is provided with a feeding port communicated with the grain drying cavity, the bottom of the inner shell is provided with a discharging port communicated with the grain drying cavity, and the inside of the dryer is provided with an elevator distributed in the vertical direction, the upper portion of the elevator is connected with a feeding channel communicated with the feeding port, and the lower portion of the elevator is connected with a discharging channel communicated with the discharging port.

9. The food vacuum heat pump drying system according to claim 8, characterized in that, The feeding channel and the discharging channel are horizontally distributed, the feeding channel is provided with a feeding screw device, the discharging channel is provided with a discharging screw device, the lower part of the elevator is respectively provided with a grain feeding port and a grain returning port, the bottom of the end of the discharging channel close to the elevator is communicated with the grain returning port, and the bottom of the end of the feeding channel close to the elevator is provided with a grain discharging port and a gate device arranged on the grain discharging port.

10. The food vacuum heat pump drying system according to claim 8, characterized in that, The lower part of the inner shell is provided with a lower hopper above the discharging port, the upper part of the lower hopper is communicated with the grain drying cavity, the lower part of the lower hopper is communicated with the discharging channel, the lower hopper is provided with a plurality of interval distributed grain guide members, adjacent two grain guide members are provided with a rotationally installed grain shifting wheel, and the drying machine is provided with a grain shifting driving mechanism for driving the rotation of the grain shifting wheel.

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