A device and method for drying grain by microwave heat pump

Abstract

The present invention discloses a device for drying grains by microwave heat pump, comprising a control unit and a feeding unit, a drying unit, a slow recovery unit, a temperature-controlled dehumidification unit and a discharging unit connected to the control unit; the feeding unit comprises a feeding hopper and a grain conveying device; the drying unit comprises a drying box, in which a first microwave generator and a first conveying belt for conveying grains are arranged; the slow recovery unit comprises a slow recovery box, in which a second microwave generator and a second conveying belt for conveying grains are arranged; the temperature-controlled dehumidification unit is provided with a dehumidification device and a heat pump device; the discharging unit comprises a discharging pipe. The present invention has high drying efficiency and low energy consumption. The present invention also relates to a method for drying grains by microwave heat pump, which can improve drying efficiency, increase grain yield, reduce broken rice rate, and improve grain quality after drying.

Description

Technical Field

[0001] The invention relates to the technical field of grain drying equipment and methods, and in particular to a device and method for drying grain by combining a microwave heat pump. Background Art

[0002] Existing data shows that in the post-production links such as drying, storage and processing, my country's annual grain loss reaches more than 70 billion jin. At present, most grain drying companies use traditional hot air drying machinery to dry grain. However, there are many disadvantages in the use of traditional hot air drying machinery, such as high energy consumption, high noise, complex operation, low intelligence, and low yield rate, high broken rice rate and poor quality after hot air drying. At the same time, it is very easy to breed grain pests and spoilage microorganisms, which is easy to cause new losses in subsequent grain storage.

[0003] In order to overcome the defects of traditional hot air drying, researchers have tried to use other methods such as fluidized state drying, microwave drying and heat pump drying to process grains. Among them, fluidized state drying has the advantages of high heat transfer rate, fast drying speed and energy saving, but the bubble phenomenon in the fluidized bed can easily cause uneven drying and many broken rice. Microwave drying has the advantages of fast heating, fast drying speed, low noise and no pollution, and has insecticidal and antibacterial effects. However, the traditional microwave drying process generally has low automation, poor temperature control ability, uneven material heating, and high energy consumption, so its application is limited. Heat pump drying has the advantages of high stability and good quality, but it has defects such as low drying efficiency.

[0004] Therefore, in recent years, combining multiple drying methods has gradually become a hot spot for research and development. For example, the Chinese patent with publication number CN105928323A discloses a grain microwave fluidized combined drying equipment, drying method and application, the Chinese patent with publication number CN102735034A discloses a surface-inlet microwave drying equipment, the Chinese patent with publication number CN201974012U discloses a microwave hot air combined drying equipment, the Chinese patent with publication number CN103263064A discloses microwave, hot air and vacuum and their combined drying equipment, and the Chinese patent with publication number CN202853296U discloses a tunnel-type hot air, microwave, far-infrared combined drying machine. The technical solutions of the above patents all adopt two or more different drying methods for combined drying, but there are still disadvantages such as low hot air utilization, high energy consumption, low yield, and high broken rice rate. Summary of the invention

[0005] One of the technical problems solved by the present invention is to provide a device for drying grains by combining microwave and heat pump, so as to improve the grain drying efficiency and reduce energy consumption.

[0006] The second technical problem solved by the present invention is to provide a method for drying grains by combining microwave and heat pump, so as to improve grain drying efficiency, reduce energy consumption, increase grain yield, reduce broken rice rate, and improve the quality of dried grains.

[0007] The technical problem solved by the present invention is achieved by adopting the following technical solutions:

[0008] A microwave heat pump combined grain drying device comprises a control unit and a feeding unit, a drying unit, a slow refrigeration unit, a temperature control dehumidification unit and a discharging unit connected to the control unit;

[0009] The feeding unit includes a feeding hopper and a grain conveying device; the drying unit includes a drying box, in which a first microwave generator and a first conveying belt for conveying grain are arranged; the slow-down unit includes a slow-down box, in which a second microwave generator and a second conveying belt for conveying grain are arranged; the temperature-controlled dehumidification unit includes a dehumidification device and a heat pump device; the discharging unit includes a discharging pipe;

[0010] The drying box is connected to the feed hopper through the grain conveying device; the material outlet of the drying box is connected to the discharge pipe, the material outlet of the drying box is also connected to the buffer box, and the material outlet of the buffer box is connected to the grain conveying device;

[0011] A first air inlet is provided at the top or upper part of the feed end of the drying box, and a first air outlet is provided at the bottom or lower part of the discharge end of the drying box, and the first air inlet and the first air outlet are respectively connected to the dehumidification device through pipelines;

[0012] A second air inlet is provided at the bottom or lower part of the feed end of the drying box, and a second air outlet is provided at the top or upper part of the discharge end of the drying box. The second air inlet and the second air outlet are respectively connected to the heat pump device through pipelines.

[0013] Furthermore, the grain conveying device and the drying box, and the drying box and the slow recovery box are all connected through a material guide assembly, and the material guide assembly includes a horizontal flow channel and an inclined flow channel; a valve plate is provided on the horizontal flow channel, and the valve plate is used to control the opening and closing degree of the horizontal flow channel; a plurality of guide plates arranged at intervals are provided on the inclined flow channel, the guide plates are vertically arranged and the extension direction of the guide plates is consistent with the material discharge direction, and the plurality of guide plates can swing synchronously.

[0014] Furthermore, the feed end and the discharge end of the drying box and the slow recovery box are both provided with air temperature and humidity measuring devices; the feed end and the discharge end of the drying box are also provided with an online moisture monitoring device; in the drying box, a plurality of first microwave generators are arranged at intervals on the top of the first conveyor belt along the material conveying direction, and an infrared temperature measuring device is also provided above the first conveyor belt; in the slow recovery box, a plurality of second microwave generators are arranged at intervals on the top of the second conveyor belt along the material conveying direction, and the infrared temperature measuring device is also provided above the second conveyor belt.

[0015] Furthermore, the dehumidification device is a condensation dehumidification device, and an air temperature and humidity measuring instrument is arranged in the condensation dehumidification device; the heat pump device is also provided with a corresponding heat exchange device.

[0016] A method for drying grain by microwave heat pump, comprising the following steps:

[0017] 1) Microwave preheating: The feeding unit conveys the grain raw materials to the drying unit. The grain raw materials in the drying unit are laid on the first conveyor belt and conveyed along the first conveyor belt. During the conveying process, the first microwave generator is started to preheat the grain raw materials. The preheating time is 30 to 60 seconds.

[0018] 2) Primary heat pump drying: Turn on the heat pump device in the temperature-controlled dehumidification unit, and the hot air enters the drying box of the drying unit. The heat pump drying time is 5 to 10 minutes;

[0019] 3) Primary microwave slow recovery: the grain raw materials processed in step 2) enter the slow recovery unit, the grain raw materials are spread on the second conveyor belt and conveyed along the second conveyor belt, the second microwave generator is started during the conveying process to heat the grain raw materials, after the average surface temperature of the grain raw materials reaches 58-62° C., the second conveyor belt stops the conveying pipe and allows the grain raw materials to slow recover for 10-15 minutes;

[0020] 4) Secondary heat pump drying and microwave slow recovery: The processed grain raw materials in step 3) are transported to the drying unit through the grain transport device of the feeding unit, and the heat pump device in the temperature control dehumidification unit is turned on, and the hot air enters the drying box of the drying unit. The heat pump drying time is 5 to 10 minutes. After the heat pump drying is completed, the grain raw materials continue to enter the slow recovery unit for secondary microwave slow recovery, and the slow recovery unit time is 10 to 15 minutes.

[0021] 5) Three heat pump drying and microwave slow recovery: The processed grain raw materials in step 4 are transported to the drying unit through the grain transport device of the feeding unit, and the heat pump device in the temperature control dehumidification unit is turned on, and the hot air enters the drying box of the drying unit. The heat pump drying time is 5 to 10 minutes; after the heat pump drying is completed, the grain raw materials continue to enter the slow recovery unit for secondary microwave slow recovery, and the slow recovery unit time is 10 to 15 minutes;

[0022] 6) Grain cooling: Step 5) The processed grain raw materials are transported to the drying unit through the grain conveying device of the feeding unit, and the heat pump device is turned on to gradually reduce the average surface temperature of the grain raw materials for cooling. The cooled grain raw materials are discharged through the discharging unit.

[0023] Furthermore, in step 1), the thickness of the grain raw material laid on the first conveyor belt is 0.5-1.0 cm, the microwave radiation power per unit grain of the first microwave generator is 50-150 w / g, and heating is stopped when the average surface temperature of the grain raw material is 38-42°C.

[0024] Furthermore, in step 2), the hot air temperature entering the drying box of the drying unit is 48-52°C, the hot air relative humidity is 78-82%, and the hot air flow rate is 0.5-2.5 m / s. When the average surface temperature of the grain raw materials reaches 48-52°C, the hot air relative humidity is adjusted to 74-76%, and the dehumidification device is turned on to make the moisture content of the grain raw materials decrease at a rate lower than 0.5% / min.

[0025] Furthermore, in step 3), the paving thickness on the second conveyor belt is 0.5-1.0 cm, and the unit grain microwave radiation power of the second microwave generator is 50-150 w / g.

[0026] Further, in step 4), the temperature of the hot air in the drying box of the drying unit is 48-52°C, the relative humidity of the hot air is 74-76%, and the flow rate of the hot air is 0.5-2.5 m / s. When the average surface temperature of the grain raw material reaches 48-52°C, the dehumidification device is turned on to make the relative humidity of the hot air 71-73%, and the rate of decrease of the moisture content of the grain raw material is lower than 0.5% / min. Controlling the process conditions so that the grain is only heated at the initial stage without dehydration, and dehydrating after the temperature of the rice is balanced and uniform, is conducive to reducing the cracking rate and broken rice rate, and further improving the quality of the dried grain.

[0027] Furthermore, in step 6), the temperature of the hot air entering the drying box of the drying unit is 48-52°C, the relative humidity of the hot air is 68-72%, and the hot air flow rate is 0.5-2.5 m / s. When the average surface temperature of the grain raw materials reaches 48-52°C, the hot air temperature is adjusted to 38-42°C. When the average surface temperature of the grain raw materials reaches 38-42°C, the hot air temperature is adjusted to 28-32°C and the hot air flow rate is 1.5-2.5 m / s. When the average surface temperature of the grain raw materials reaches 38-42°C, the cooling is completed. During the cooling process, the heat of the grain is gently and evenly reduced, which is further beneficial to reduce the cracking rate and broken rice rate of the dried grain and improve the quality of the dried grain.

[0028] Beneficial effects: The microwave heat pump combined grain drying device of the present invention has the advantages of high drying efficiency, good drying and sterilization effects and low energy consumption.

[0029] In the method of microwave heat pump combined grain drying described in the present invention, the grain needs to be heated and energy consumed in both the drying stage and the slow revival stage. The present invention cleverly uses the energy transferred to the grain in the drying stage to bring it into the slow revival stage. As long as the energy is slightly supplemented, the slow revival effect can be improved, and the grain energy after the slow revival can be brought into the next stage of grain drying. The grain raw materials after cyclic drying and slow revival enter the cooling stage. In this process, the heat is fully utilized, and the energy exceeding the grain drying temperature can be recovered, thereby greatly reducing energy consumption and saving energy.

[0030] The present invention combines microwave preheating, microwave drying, heat pump drying and slow thawing cycles to further improve drying efficiency and grain yield. Preheating allows the grain raw materials to be heated evenly and gently during the drying process; slow thawing allows the temperature of the dried rice to be more even, and the moisture is evenly redistributed, which is beneficial to reducing the cracking rate and broken rice rate of the dried rice, improving the quality of the dried rice, and improving the quality of the dried grain. The present invention can also reduce the nutritional loss of the dried grain and improve the storage performance of the grain after drying. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of a preferred embodiment of the present invention.

[0032] Figure 2 It is a schematic structural diagram of the material guiding assembly in a preferred embodiment of the present invention.

[0033] Among them: 1. control unit; 2. feeding unit; 21. feeding hopper; 22. grain conveying device; 221. lifting motor; 3. drying unit; 31. drying box; 311. first air inlet; 312. second air inlet; 313. second air outlet; 314. first air outlet; 32. first microwave generator; 33. first conveyor belt; 4. slow recovery unit; 41. slow recovery box; 42. second conveyor belt; 43. second microwave generator; 5. temperature control dehumidification unit; 51. dehumidification device; 52. heat exchange device; 53. heat pump device; 6. discharge pipe; 7. material guide assembly; 71. horizontal flow channel; 711. valve plate; 712. adjustment handle; 713. rotating shaft; 72. inclined flow channel; 721. guide plate; 722. short shaft. DETAILED DESCRIPTION

[0034] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0035] Example 1

[0036] The device for drying grain by microwave heat pump comprises a control unit 1 and a feeding unit 2, a drying unit 3, a slow refrigeration unit 4, a temperature control dehumidification unit 5 and a discharging unit connected to the control unit 1.

[0037] The feeding unit 2 includes a feeding hopper 21 and a grain conveying device 22; in this embodiment, the grain conveying device 22 is a grain lifting device, which includes a lifting motor 221 and a plastic funnel elevator. The grain raw materials enter from the feeding hopper 21 and enter the drying unit 3 through the grain lifting device.

[0038] The drying unit 3 includes a drying box 31, which is a horizontally placed rectangular box structure. A first microwave generator 32 and a first conveyor belt 33 for conveying grain are arranged in the drying box 31; the first conveyor belt 33 is arranged horizontally in the drying box 31, and guard plates are arranged on both sides of the first conveyor belt 33 to prevent grain from falling. In the drying box 31, a plurality of mutually independent first microwave generators 32 are arranged at intervals on the top of the first conveyor belt 33 along the material conveying direction, preferably evenly distributed, and an infrared temperature measuring device is also arranged above the first conveyor belt 33.

[0039] The slow-release unit 4 includes a slow-release box 41, in which a second microwave generator 43 and a second conveyor belt 42 for conveying grain are arranged; in the slow-release box 41, the second conveyor belt 42 is arranged horizontally in the slow-release box 41, and guard plates are arranged on both sides of the second conveyor belt 42 to prevent grain from falling. In the slow-release box 41, multiple independent second microwave generators 43 are arranged at intervals on the top of the second conveyor belt 42 along the material conveying direction, preferably evenly distributed, and an infrared temperature measuring device is also arranged above the second conveyor belt 42.

[0040] The feeding end and the discharging end of the drying box 31 and the slow recovery box 41 are both provided with air temperature and humidity measuring devices.

[0041] The feeding end and the discharging end of the drying box 31 are also provided with an online moisture monitoring device for online monitoring of the moisture of the grain raw materials entering and leaving the drying box 31 .

[0042] The temperature control dehumidification unit 5 is provided with a dehumidification device 51 and a heat pump device 53; the dehumidification device 51 is a condensation dehumidification device, and an air temperature and humidity measuring instrument is provided in the condensation dehumidification device; the heat pump device 53 is also provided with a corresponding heat exchange device 52. The heat exchange device 52 is used to control the temperature of the hot air entering the drying box 31, and can further recover the excess heat in the drying box 31.

[0043] The discharging unit comprises a discharging pipe 6 .

[0044] The drying box 31 is connected to the feed hopper 21 through the grain conveying device 22; the material outlet of the drying box 31 is connected to the discharge pipe, and the material outlet of the drying box 31 is also connected to the buffer box, and the material outlet of the buffer box is connected to the grain conveying device 22. Therefore, the grain raw materials enter from the feed hopper 21, enter the drying box 31 through the grain conveying device 22, and the grain raw materials in the drying box 31 are conveyed by the first conveyor belt. The grain in the drying box 31 can enter the buffer box 41, and the grain raw materials in the buffer box are conveyed by the second conveyor belt. The grain in the buffer box enters the circulating drying through the grain conveying device 22, and the grain raw materials after drying are discharged from the drying box 31 into the discharge pipe 6. Whether the grain raw materials enter the buffer box 41 or the discharge pipe during operation can be realized by the shunt pipe and the control valve arranged on the shunt pipe.

[0045] A first air inlet 311 is provided at the top or upper part of the feeding end of the drying box 31, and a first air outlet 314 is provided at the bottom or lower part of the discharging end of the drying box 31. The first air inlet 311 and the first air outlet 314 are respectively connected to the dehumidification device 51 through pipelines. During temperature-controlled drying, moisture in the grain raw materials enters the air, and the wet air gathers at the bottom of the drying box 31. Therefore, the wet air can be better entered by the dehumidification device 51 through the first air outlet 314 provided at the bottom or lower part of the discharging end of the drying box 31, and the dry air quickly enters the top of the drying box 31 through the first air inlet 311, which can promote the wet air at the discharging end and the lower layer in the drying box 31, and at the same time prevent the dry air and the wet air from mixing, so as to better form a dehumidification cycle.

[0046] The bottom or lower part of the feed end of the drying box 31 is provided with a second air inlet 312, and the top or upper part of the discharge end of the drying box 31 is provided with a second air outlet 313, and the second air inlet 312 and the second air outlet 313 are respectively connected to the heat pump device 53 through pipelines. After the food raw materials are heated by the first microwave generator 32 in the drying box 31, the hot air gathers at the top of the drying box 31, and the hot air gathered at the top of the drying box 31 can be quickly extracted by the heat exchange device through the second air outlet 313 set at the top or upper part of the discharge end of the drying box 31, and energy is recovered and, while the new temperature-controlled hot air enters through the second air inlet 312 set at the bottom or lower part of the feed end of the drying box 31, thereby pushing the original hot air in the drying box 31, preventing the new and old hot air from mixing, and better promoting the temperature and humidity control cycle.

[0047] During the operation, before the grain raw material enters the drying box 31 through the grain conveying device 22, the initial moisture content of the grain is detected by the moisture online monitoring device, and then the grain raw material enters the drying box 31 for microwave preheating, and the hot air generated by the heat pump device in the temperature control dehumidification unit preheats the grain in the drying box 31, and then the grain raw material enters the slow revival box 41 for a slow revival, and the grain raw material after the slow revival is completed re-enters the drying box 31 for temperature control drying, and the dehumidification device 51 is started after the temperature control drying is completed, and then enters the slow revival box 41 for a second slow revival, and the temperature control drying and slow revival are cyclically performed, and then the material is discharged after cooling. The upper and lower combined structures of the drying box 31 and the slow revival box can make the grain raw material continuously repeat the temperature control drying, microwave slow revival, dehumidification and other operations, and through the continuous deepening of the process, the moisture of the grain is gradually removed while killing insects, and the grain is dried fully and efficiently while ensuring the quality of the grain through continuous monitoring and control of the grain humidity, temperature, and air moisture. The whole process is completed automatically, which is convenient and fast.

[0048] In some preferred embodiments, a controller is provided in the control unit 1, and the infrared thermometer, air temperature and humidity measuring instrument, moisture online monitoring device, grain conveying device 22, first conveyor belt, second conveyor belt, dehumidification device, heat pump device, first microwave generator, second microwave generator, motor and control valves on each pipeline on the device of the present invention are all electrically connected to the controller.

[0049] In some preferred embodiments, as an improvement, Figure 2 As shown, the food conveying device 22 and the drying box 31, and the drying box 31 and the slow recovery box 41 are all connected through the material guide assembly 7. The material guide assembly 7 includes a horizontal flow channel 71 and an inclined flow channel 72; a valve plate 711 is provided on the horizontal flow channel 71, and the valve plate 711 is used to control the opening and closing degree of the horizontal flow channel 71. Preferably, the valve plate 711 is fixedly connected to a rotating shaft 713, and the rotating shaft 713 is connected to an adjusting handle 712. The rotating shaft 713 rotates at different angles under the adjustment of the adjusting handle 712, so that the valve plate 711 and the horizontal flow channel 71 are at different angles, thereby achieving the purpose of adjusting the opening and closing degree of the horizontal flow channel 71.

[0050] The inclined flow channel 72 is provided with a plurality of guide plates 721 arranged at intervals. The guide plates 721 are arranged vertically and the extension direction of the guide plates 721 is consistent with the material discharge direction. The plurality of guide plates 721 can swing synchronously. The plurality of guide plates 721 can swing synchronously in a variety of ways. In some schemes, one end of the guide plate 721 is connected to a rotatable short shaft 722, and the bottom of the short shaft 722 is connected to the output shaft of a rotating motor through a connecting rod. The rotating motor is a forward and reverse motor, thereby driving the plurality of guide plates 721 to swing synchronously within a certain amplitude range.

[0051] By controlling the opening of the valve plate 711, the thickness of the grain on the first conveyor belt or the second conveyor belt can be adjusted. By controlling the feed speed and the transmission speed of the first conveyor belt, the second conveyor belt and the transmission speed of the second microwave generator of the fifth unit 5, the grain thickness can be kept uniform. By synchronizing and swinging the multiple guide plates 721 left and right evenly, the grain is diverted on the first conveyor belt and the second conveyor belt and placed in an S shape, thereby increasing the spreading path and area of ​​the grain, making the temperature-controlled drying and dehumidification more thorough. Example 2

[0052] (1) A method for drying grain by microwave heat pump, comprising the following steps:

[0053] 1) Microwave preheating: In this embodiment, the rice raw material is fresh rice, and the initial moisture content of the grain raw material is about 23%. The grain raw material enters from the feed hopper and is transported to the drying unit through the grain conveying device. The conveying rate of the grain conveying device and the conveying rate of the first conveyor belt are controlled by the control unit to ensure that the thickness of the grain raw material on the first conveyor belt is controlled to be about 0.9 cm, at a uniform speed, and evenly spread. The grain raw material is conveyed along the first conveyor belt. During the conveying process, the first microwave generator is started to preheat the grain raw material. The unit grain radiation power of the first microwave generator is controlled to be 100w / g. When the infrared temperature measuring device detects that the surface temperature of the grain raw material reaches 40°C, the infrared temperature measuring device feeds back the detection information to the controller, and the controller controls the first microwave generator corresponding to the grain raw material to stop working. Preheating is completed, and preheating takes about 30s to complete.

[0054] 2) Primary heat pump drying: Turn on the heat pump device in the temperature control dehumidification unit, temporarily turn off the dehumidification device in the temperature control dehumidification unit, and let the hot air enter the drying box of the drying unit. The hot air temperature entering the drying box of the drying unit is 50°C, the hot air relative humidity is 80%, and the hot air flow rate is 1.5m / s. When the average surface temperature of the grain raw material reaches 50°C, adjust the hot air relative humidity to 75%, and keep other conditions unchanged. Turn on the dehumidification device for dehumidification. During the dehumidification process, the moisture content of the grain raw material decreases at a rate lower than 0.5% / min. The heat pump drying time is about 5 minutes. After drying, the moisture content of the grain raw material is about 19 (, ready to enter the slow recovery stage.

[0055] 3) Primary microwave slow recovery: The grain raw materials processed in step 2) are divided into the slow recovery unit, and the grain raw materials are spread on the second conveyor belt and conveyed along the second conveyor belt. When the grain raw materials contact the second conveyor belt, the second microwave generator is started to heat the grain raw materials. After the average surface temperature of the grain raw materials reaches 60°C, the infrared temperature measuring device feeds back the detection information to the controller, the second conveyor belt stops conveying, and the grain raw materials on the second conveyor belt are slow recovered at 60°C for 15 minutes. In this process, the thickness of the grain on the second conveyor belt is about 0.9 cm, and the unit grain microwave radiation power of the second microwave generator is controlled to be 150w / g.

[0056] 4) Secondary heat pump drying and microwave slow revival: Step 3) The processed grain raw materials are further transported to the drying unit through the grain conveying device of the feeding unit, the heat pump device in the temperature-controlled dehumidification unit is turned on, the dehumidification device is temporarily turned off, and the hot air enters the drying box of the drying unit. The hot air temperature entering the drying box of the drying unit is 50°C, the hot air relative humidity is 75%, and the hot air flow rate is 1.5m / s. During this process, the heat pump device causes the surface of the grain raw materials to cool down and recycles excess energy, and also plays a certain degree of slow revival effect, and does not dry and dehumidify the grain raw materials. When the infrared temperature measuring device detects that the average surface temperature of the grain raw materials reaches 50°C, the dehumidification device is turned on for dehumidification, the hot air relative humidity is adjusted to 70%, and the moisture content of the grain raw materials decreases at a rate lower than 0.5% / min. The heat pump drying time is about 10 minutes, and the moisture content of the grain raw materials is about 17% after drying.

[0057] After the heat pump drying is completed, the grain raw materials continue to enter the slow-down unit for secondary microwave slow-down, and the slow-down unit time is about 12 minutes.

[0058] 5) Three heat pump drying and microwave slow recovery: Step 4) The processed grain raw materials are transported to the drying unit through the grain conveying device of the feeding unit, and the heat pump device in the temperature control dehumidification unit is turned on, and hot air enters the drying box of the drying unit. The heat pump drying time is about 8 minutes, and the moisture content of the rice is 13.6% after the drying is completed. After the heat pump drying is completed, the grain raw materials continue to enter the slow recovery unit for secondary microwave slow recovery, and the slow recovery unit time is about 12 minutes;

[0059] 6) Grain cooling: Step 5) The processed grain raw materials are transported to the drying unit through the grain conveying device of the feeding unit, and the heat pump device is turned on to gradually reduce the average surface temperature of the grain raw materials for cooling. Specifically, during cooling, the hot air temperature initially entering the drying box of the drying unit is 50°C, the relative humidity of the hot air is 70%, and the hot air flow rate is 1.5m / s. When the average surface temperature of the grain raw materials reaches 50°C, the hot air temperature is adjusted to 40°C, and cooling is continued. When the average surface temperature of the grain raw materials reaches 40°C, the hot air temperature is adjusted to 30°C and the hot air flow rate is 1.5m / s; when the average surface temperature of the grain raw materials reaches 30°C, the cooling is completed. The cooled grain raw materials are discharged through the discharging unit and collected and stored.

[0060] (II) Effect verification

[0061] In order to verify the technical advantages of the equipment of the present invention, the present invention is compared with the prior art in terms of drying time, drying efficiency, energy consumption, cracking rate of dried rice, rough rice rate, and polished rice rate. The results are shown in Table 1.

[0062] The existing technologies include microwave liquefaction combined drying, microwave hot air combined drying, hot air drying + microwave slow drying, microwave drying, and hot air drying. The specific methods and sources are shown in Table 1.

[0063] The cracking rate is determined according to the method of GB / T 5491-1985. The roughness rate is determined according to the method of GB / T 5495-2008. The polished rice rate is determined according to the method of GB / T 21719-2008. The insecticidal rate, antibacterial rate and water content calculation method refer to "Zhang Xijun, Xiong Shanbai, Zhao Siming. Effect of microwave treatment on rice quality [J], Chinese Agricultural Science, 2009, 42 (1): 224-229". Compared with the prior art, the present invention has obvious advantages in drying time, drying efficiency, energy consumption, cracking rate of dried rice, roughness rate, polished rice rate and other aspects. It has extremely important application value in the current promotion of energy conservation and emission reduction, improving rice drying efficiency, improving rice drying quality and ensuring grain storage safety.

[0064] Table 1

[0065]

[0066] The equipment and method of the present invention are used to dry several grain raw materials with an initial moisture content of 23%. After drying, the cracking rate, rough rice rate, polished rice rate and appearance quality of the grain raw materials are shown in Table 2. As shown in Table 2, the drying efficiency of the several grains is above 650kg / h, the energy consumption is below 2.9kW·h, the breakage rate is less than 2%, the rough rice rate is greater than 75%, the polished rice rate is greater than 80%, and the insecticidal rate and antibacterial rate are both 100%, which has great advantages compared with the current drying equipment and drying method.

[0067] Table 2

[0068]

[0069] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for drying grain by microwave heat pump, characterized in that: It includes microwave preheating, primary heat pump drying, primary microwave slow thawing, secondary heat pump drying and microwave slow thawing, tertiary heat pump drying, microwave slow thawing and grain cooling; when the grain is cooled, the heat pump device is turned on to gradually reduce the average temperature of the surface temperature of the grain raw materials for cooling; The grain drying is completed by using a device for drying grain in combination with a microwave heat pump, the device comprising a control unit and a feeding unit, a drying unit, a slow drying unit, a temperature-controlled dehumidification unit, and a discharging unit connected to the control unit; The feeding unit includes a feeding hopper and a grain conveying device; the drying unit includes a drying box, in which a first microwave generator and a first conveying belt for conveying grain are arranged; the slow-release unit includes a slow-release box, in which a second microwave generator and a second conveying belt for conveying grain are arranged; the temperature-controlled dehumidification unit includes a dehumidification device and a heat pump device; the discharging unit includes a discharging pipe; The drying box is connected to the feed hopper through the grain conveying device; the material outlet of the drying box is connected to the discharge pipe, the material outlet of the drying box is also connected to the buffer box, and the material outlet of the buffer box is connected to the grain conveying device; A first air inlet is provided at the top or upper part of the feed end of the drying box, and a first air outlet is provided at the bottom or lower part of the discharge end of the drying box, and the first air inlet and the first air outlet are respectively connected to the dehumidification device through pipelines; A second air inlet is provided at the bottom or lower part of the feed end of the drying box, and a second air outlet is provided at the top or upper part of the discharge end of the drying box, and the second air inlet and the second air outlet are respectively connected to the heat pump device through pipelines; The food conveying device and the drying box, the drying box and the slow recovery box are connected through a material guide assembly, the material guide assembly includes an inclined flow channel; a plurality of guide plates arranged at intervals are arranged on the inclined flow channel, the guide plates are arranged vertically and the extending direction of the guide plates is consistent with the material discharge direction, and the plurality of guide plates can swing synchronously; The material guiding component also includes a horizontal flow channel; a valve plate is arranged on the horizontal flow channel, and the valve plate is used to control the opening and closing degree of the horizontal flow channel.

2. The method for drying grain by microwave heat pump according to claim 1, characterized in that: The feeding end and the discharging end of the drying box and the slow-release box are both provided with air temperature and humidity measuring devices; the feeding end and the discharging end of the drying box are also provided with moisture online monitoring devices; in the drying box, a plurality of first microwave generators are arranged at intervals on the top of the first conveyor belt along the material conveying direction, and an infrared temperature measuring device is also provided above the first conveyor belt; in the slow-release box, a plurality of second microwave generators are arranged at intervals on the top of the second conveyor belt along the material conveying direction, and the infrared temperature measuring device is also provided above the second conveyor belt.

3. The method for drying grain by microwave heat pump according to claim 2, characterized in that: The dehumidification device is a condensation dehumidification device, and an air temperature and humidity measuring instrument is arranged inside the condensation dehumidification device; the heat pump device is also provided with a corresponding heat exchange device.

4. The method for drying grain by microwave heat pump according to claim 1, characterized in that: The steps include: 1) Microwave preheating: The feeding unit conveys the grain raw materials to the drying unit. The grain raw materials in the drying unit are laid on the first conveyor belt and conveyed along the first conveyor belt. During the conveying process, the first microwave generator is started to preheat the grain raw materials. The preheating time is 30 to 60 seconds. 2) Primary heat pump drying: Turn on the heat pump device in the temperature-controlled dehumidification unit, and the hot air enters the drying box of the drying unit. The heat pump drying time is 5 to 10 minutes; 3) Primary microwave slow recovery: the grain raw materials processed in step 2) enter the slow recovery unit, the grain raw materials are spread on the second conveyor belt and conveyed along the second conveyor belt, the second microwave generator is started during the conveying process to heat the grain raw materials, after the average surface temperature of the grain raw materials reaches 58-62° C., the second conveyor belt stops the conveying pipe and allows the grain raw materials to slow recover for 10-15 minutes; 4) Secondary heat pump drying and microwave slow recovery: The processed grain raw materials in step 3) are transported to the drying unit through the grain transport device of the feeding unit, and the heat pump device in the temperature control dehumidification unit is turned on, and the hot air enters the drying box of the drying unit. The heat pump drying time is 5 to 10 minutes. After the heat pump drying is completed, the grain raw materials continue to enter the slow recovery unit for secondary microwave slow recovery, and the slow recovery unit time is 10 to 15 minutes. 5) Three heat pump drying and microwave slow recovery: The processed grain raw materials in step 4 are transported to the drying unit through the grain transport device of the feeding unit, and the heat pump device in the temperature control dehumidification unit is turned on, and the hot air enters the drying box of the drying unit. The heat pump drying time is 5 to 10 minutes; after the heat pump drying is completed, the grain raw materials continue to enter the slow recovery unit for secondary microwave slow recovery, and the slow recovery unit time is 10 to 15 minutes; 6) Grain cooling: Step 5) The processed grain raw materials are transported to the drying unit through the grain conveying device of the feeding unit, and the heat pump device is turned on to gradually reduce the average surface temperature of the grain raw materials for cooling. The cooled grain raw materials are discharged through the discharging unit.

5. The method for drying grain by microwave heat pump according to claim 4, characterized in that: In step 1), the thickness of the grain raw material on the first conveyor belt is 0.5-1.0 cm, the unit grain microwave radiation power of the first microwave generator is 50-150 w / g, and heating is stopped when the average surface temperature of the grain raw material is 38-42°C.

6. The method for drying grain by microwave heat pump according to claim 5, characterized in that: In step 2), the hot air temperature entering the drying box of the drying unit is 48-52°C, the hot air relative humidity is 78-82%, and the hot air flow rate is 0.5-2.5 m / s. When the average surface temperature of the grain raw materials reaches 48-52°C, the hot air relative humidity is adjusted to 74-76%, and the dehumidification device is turned on to make the moisture content of the grain raw materials decrease at a rate lower than 0.5% / min.

7. The method for drying grain by microwave heat pump according to claim 5, characterized in that: In step 3), the paving thickness on the second conveyor belt is 0.5-1.0 cm, and the microwave radiation power per unit grain of the second microwave generator is 50-150 w / g.

8. The method for drying grain by microwave heat pump according to claim 5, characterized in that: In step 4), the temperature of the hot air entering the drying box of the drying unit is 48-52°C, the relative humidity of the hot air is 74-76%, and the flow rate of the hot air is 0.5-2.5 m / s. When the average surface temperature of the grain raw materials reaches 48-52°C, the dehumidification device is turned on to make the relative humidity of the hot air 70-73%, and the moisture content of the grain raw materials decreases at a rate lower than 0.5% / min.

9. The method for drying grain by microwave heat pump according to claim 5, characterized in that: In step 6), the hot air temperature entering the drying box of the drying unit is 48-52°C, the hot air relative humidity is 68-72%, and the hot air flow rate is 0.5-2.5 m / s. When the average surface temperature of the grain raw materials reaches 48-52°C, the hot air temperature is adjusted to 38-42°C. When the average surface temperature of the grain raw materials reaches 38-42°C, the hot air temperature is adjusted to 28-32°C and the hot air flow rate is 1.5-2.5 m / s; when the average surface temperature of the grain raw materials reaches 38-42°C, the cooling is completed.

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