Radio frequency combined heat pump gas jet dryer and agricultural product drying method

Abstract

The present invention discloses a radio frequency combined heat pump gas jet dryer and a method for drying agricultural products, and relates to the field of agricultural product processing. At present, green, energy-saving and efficient drying is an urgent need for primary processing of agricultural products at the place of origin; the present invention includes a dehumidification unit, a radio frequency heating system, an air energy heat pump, a gas circulation jet unit, an automatic weighing unit and an automatic control system; the air energy heat pump is arranged on the outside of the box; the inner cavity of the box includes an upper cavity, a middle cavity, a lower cavity, a vertical return air duct located on one side and an outlet duct connected to the return air duct. This technical solution integrates a dehumidification unit, a radio frequency heating system, an air energy heat pump, and a gas circulation jet unit; the radio frequency heating system is assisted by the hot air blown out by the air energy heat pump to reduce the temperature difference between materials and improve the uniformity of drying; the hot air acts as a medium to promptly take away the water vapor evaporated from the surface of the material, and the surface is cooled; rapid dehumidification reduces the drying time, low energy consumption, and high safety of the dried agricultural products.

Description

Technical Field

[0001] The invention relates to the field of agricultural product processing, and in particular to a radio frequency combined heat pump gas jet dryer and an agricultural product drying method. Background Art

[0002] my country is a major producer of agricultural products. Agricultural products are prone to mold, rot and deterioration due to their high moisture content after harvest, especially vegetables and fruits with large root tubers and fruits. According to expert estimates, the post-harvest loss rates of Chinese farmers' stored grain, potatoes, fruits and vegetables are 7% to 11%, 15% to 20%, 15% to 20% and 20% to 25% respectively, which are much higher than the average loss rates in developed countries, and the economic losses are equivalent to hundreds of billions.

[0003] The drying methods for agricultural products after harvesting at the production site mostly use natural drying and drying in drying rooms. There are common problems such as long drying time, hollow interior, and serious quality degradation. Although natural drying is simple to operate and does not require additional energy output, it requires huge resources for drying sites, especially for larger products that are more likely to deteriorate during the drying process. Existing drying technologies mostly use convection and conduction heating, which works better for flaky or thin-layer agricultural products. However, for larger agricultural products, the internal temperature rise depends on the heat conduction of the material itself, so the heating rate is slow, and the internal moisture diffusion path is long, resulting in a slow drying process; long-term heat accumulation has an adverse effect on heat-sensitive components. At present, there is infrared radiation combined with heat pump drying, but the infrared radiation has weak penetration ability and the material heats up slowly. Therefore, green, energy-saving, and efficient mechanical drying technology and equipment are urgent needs for primary processing of agricultural products at the production site. Summary of the invention

[0004] The technical problem to be solved and the technical task proposed by the present invention are to improve and perfect the existing technical solutions and provide a radio frequency combined heat pump gas jet dryer to achieve the purpose of drying agricultural products in a green, energy-saving and efficient manner. To this end, the present invention adopts the following technical solutions.

[0005] A radio frequency combined heat pump gas jet dryer, comprising a box, a dehumidification unit, a radio frequency heating system, an air energy heat pump, a gas circulation jet unit, an automatic weighing unit and an automatic control system;

[0006] The air energy heat pump is arranged on the outside of the box; the inner cavity of the box includes an upper cavity, a middle cavity, a lower cavity, a vertical return air duct located on one side and an air outlet duct communicating with the return air duct, wherein the upper cavity accommodates a gas circulation jet unit; the middle cavity accommodates a radio frequency heating system, a support rack, and an automatic weighing unit connected to the support rack; the lower cavity accommodates a dehumidification unit; the air flow passes through the air energy heat pump, the gas circulation jet unit, the radio frequency heating system, the dehumidification unit, the air outlet duct, and the return air duct and returns to the gas circulation jet unit.

[0007] This technical solution integrates a dehumidification unit, a radio frequency heating system, an air energy heat pump, and a gas circulation jet unit; the radio frequency heating system supplemented by the hot air blown by the air energy heat pump can reduce the temperature difference between materials and improve the uniformity of drying; at the same time, the hot air can be used as a medium to promptly take away the water vapor evaporated from the surface of the material, thereby cooling the surface of the sample. In addition, the use of a dehumidification unit can accelerate the dehumidification effect and reduce the drying time. This technical solution has low drying energy consumption, greatly improved drying efficiency, and high safety of agricultural products after drying.

[0008] As a preferred technical means: an L-shaped plate is provided under the support rack, and the L-shaped plate is a component of the air outlet duct; the dehumidification unit includes a dehumidification fan and a humidity sensor, and the dehumidification fan is installed under the bottom of the L-shaped plate, and the L-shaped plate is provided with a moisture through hole connected to the dehumidification fan; a dehumidification hole connected to the outside is provided on the box body located in the lower cavity; the humidity sensor is arranged in the middle cavity near the support rack; the air energy heat pump is arranged on the outside of the box body.

[0009] As a preferred technical means: the radio frequency heating system includes an upper electrode plate, a lower electrode plate, a radio frequency generator, and an optical fiber temperature sensor; the upper electrode plate is an aluminum plate, and flow holes are evenly distributed on the electrode plate; the lower electrode plate is an aluminum plate, which is directly below the upper electrode plate, and the opening positions correspond one-to-one to the flow holes of the upper electrode plate; a material tray for placing materials is provided on the support rack, the upper electrode plate is above the material tray, and the lower electrode plate is below the material tray.

[0010] As a preferred technical means: the radio frequency generator is on the lower left side of the box, there are at least two optical fiber temperature sensors, one of which is installed on the side of the vertical plate and can be directly inserted into the material, and the other optical fiber temperature sensor monitors the temperature in the middle cavity; the box where the middle cavity is located is a drying box, and the drying box is composed of a box frame, a horizontal plate and a vertical plate.

[0011] As an optimal technical means: the gas circulation jet unit includes an air duct, a centrifugal fan, a top swirl air supply port, a bell-shaped air flow uniformity chamber, a gas jet device, an air outlet duct and a return air duct, the air outlet of the air duct is connected to the air inlet of the centrifugal fan, the centrifugal fan is installed in the middle position at the top end of the box body, one end of the top swirl air supply port is connected to the air outlet of the centrifugal fan, the bell-shaped air flow uniformity chamber is connected to the air outlet of the top swirl air supply port, the gas jet device is installed on the upper side of the upper electrode plate, communicates with the bell-shaped air flow uniformity chamber upward, and the downward air flow injection end passes through the flow hole of the upper electrode plate and is tightly assembled, and the gas jet vertically passes through the material, the material tray and the lower electrode plate; the upper electrode plate, the gas jet device and the lower electrode plate are all relatively fixed on the columns, there are 4 columns, and the four columns are respectively fixed on the four corners of the box body formed by the horizontal plate, the L-shaped plate, the vertical plate and the box frame.

[0012] As a preferred technical means: the gas jet device includes a nozzle bracket and multiple jet components, each jet component is composed of a jet pipe, a nozzle, a sealing ring and a locking nut; the nozzles are evenly distributed in a diamond shape; the air outlet duct is composed of an L-shaped plate, a vertical plate and a lower electrode plate, one end of which is connected to the return air duct, and the other end is connected to the drying box to form a circulating airflow; one end of the return air duct is connected to the air outlet duct, and the other end is connected to the air duct and the air inlet of the centrifugal fan.

[0013] As a preferred technical means: the automatic weighing unit includes a material tray, material, a weighing pillar, and a weighing sensor; the weighing pillar is fixedly installed on the bottom surface of an L-shaped plate under the lower electrode plate, there are at least three weighing sensors, and the three weighing sensors are respectively fixed on the three corners of the bottom of the weighing pillar, the humidity sensor is installed on the side wall of the drying box near the lower electrode plate, and a plurality of small holes are evenly distributed on the material tray.

[0014] As a preferred technical means: the automatic control system includes a controller and a touch screen. The controller is installed at the bottom of the box frame. The air energy heat pump, optical fiber temperature sensor, humidity sensor, automatic weighing sensor, and radio frequency generator are all connected to the controller. The touch screen is set on the equipment door on the front side of the box frame, and the touch screen is connected to the controller by wires.

[0015] Another object of the present invention is to provide a method for drying agricultural products using a radio frequency combined heat pump gas jet dryer; the method for drying agricultural products comprises the following steps:

[0016] S1. Put the washed and sorted agricultural products into the material tray, and use the touch screen in the automatic control system to set the drying process parameters;

[0017] S2. After the drying process parameters are set, the program is started through the touch screen, and the radio frequency heating system and the gas jet device are started to increase the temperature of the material in the drying chamber, and the first stage of drying is carried out, and the moisture content of the agricultural products on a wet basis is reduced;

[0018] S3, the moisture content of the agricultural products on a wet basis is reduced to the first threshold, the air energy heat pump is turned on, the gas jet device is retained, and the radio frequency heating system is turned off at the same time, and the second stage of drying is carried out, and the moisture content of the agricultural products on a wet basis continues to decrease;

[0019] S4, the moisture content of the agricultural products on a wet basis is reduced to the second threshold value, the radio frequency heating system is turned on, the air energy heat pump and the gas jet device are retained, and the third stage of drying is carried out, and the moisture content of the agricultural products on a wet basis continues to decrease;

[0020] S5. When the wet basis moisture content of agricultural products drops to the third threshold, the air energy heat pump and radio frequency heating system are turned off, the equipment stops running, and the drying of agricultural products is completed.

[0021] Beneficial effects: The radio frequency combined heat pump gas jet dryer of the present invention can solve the problems of slow heating in the early stage and low dehumidification efficiency in the later stage of drying existing in single heat pump drying. At the same time, it can also solve the technical problem of uneven drying rate existing in single radio frequency drying. The radio frequency combined heat pump gas jet dryer not only recovers the sensible heat in the waste steam, but also recovers the latent heat in the waste steam through the combined heating and dehumidification drying process, which greatly reduces energy consumption and improves the efficiency of heat pump drying. It is not easy to cause microbial contamination during the drying process and is suitable for drying heat-sensitive materials. In addition, the use of radio frequency heating drying in the early stage of drying can give full play to the advantages of radio frequency heating depth, fast temperature rise and fast drying rate. This not only solves the problems of low drying temperature, slow drying rate and long drying time of heat pump drying of agricultural products that are easy to cause microbial contamination, but also can be applied to the drying processing of various heat-sensitive materials, reducing the energy consumption of the device when drying agricultural products.

[0022] Compared with the existing hot air drying method for agricultural products, the agricultural product drying method of the invention shortens the drying time by 30% to 50% and reduces the energy consumption by 20% to 30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the present invention.

[0024] Figure 2 It is a schematic diagram of the external structure of the present invention.

[0025] Figure 3 It is a schematic cross-sectional structural diagram of a drying box of the present invention;

[0026] Figure 4 It is a bottom view of the drying box of the present invention.

[0027] Figure 5 It is a schematic structural diagram of the gas jet device of the present invention.

[0028] Figure 6 for Figure 5 AA cross-sectional structure schematic diagram.

[0029] Figure 7 This is a flow chart of the working method of Example 1 of the present invention.

[0030] In the figure, 1, box frame; 2, dehumidification unit; 4, air energy heat pump; 6, automatic weighing unit; 50, air duct; 11, column; 12, horizontal plate; 13, L-shaped plate; 14, vertical plate; 15, silo door; 16, observation window; 17, handle; 18, moving wheel; 19, drying box; 20, dehumidification fan; 21, moisture through hole; 22, dehumidification hole; 23, humidity sensor; 31, upper electrode plate; 32, lower electrode plate; 33, radio frequency generator ; 34. Fiber optic temperature sensor; 50. Air duct; 51. Centrifugal fan; 52. Top swirl air supply port; 53. Bell-mouth air flow uniformity chamber; 54. Gas jet device; 55. Air outlet duct; 56. Return air duct; 541. Nozzle bracket; 542. Jet pipe; 543. Nozzle; 544. Sealing ring; 545. Locking nut; 61. Weighing support; 62. Material tray; 63. Material; 64. Weighing sensor; 72. Touch screen; 71. Controller. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Since the embodiments disclosed in the present invention can be arranged in different directions, these terms indicating directions are only for illustration and should not be regarded as limitations. For example, "up" and "down" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

[0033] Heat pump drying has many advantages, such as low energy consumption, low drying temperature, wide adjustable drying range, easy to control operation process, high product quality, and environmental friendliness. It has been widely used in the drying of heat-sensitive materials such as wood, fruits and vegetables, aquatic products, and grains. However, in the early stage of heat pump drying, the material temperature rises slowly, and the mass transfer coefficient between air and material decreases in the middle and late stages of drying. It takes a long drying time and more energy to remove the moisture. At the same time, the air state at the inlet and outlet of the drying chamber changes very little, which affects the cooling and dehumidification capacity of the evaporator.

[0034] The rotating jet air outlet makes the air flow at the chamber air inlet more uniform, because the center of the rotating jet is in the negative pressure zone, it can induce a large amount of surrounding air to mix with it, and then send it to the working area, and then assist with gas jet drying. The gas ejected by the gas jet has an extremely high speed, and the fluid flow is short. When it directly impacts the surface of the material to be heated, a very thin boundary layer is generated between the airflow and the surface of the material. Therefore, the heat transfer coefficient of gas jet impact drying is several times or even an order of magnitude higher than that of general hot air heat exchange.

[0035] Radio frequency drying technology has stable temperature control and greater penetration depth. Radio frequency energy can cause the oscillation migration of polar molecules and charged ions inside the material, causing it to heat up rapidly as a whole, promoting the migration of moisture in agricultural products, significantly shortening the drying time, reducing energy consumption and obtaining higher product quality. However, during single radio frequency drying, the electric field is unevenly distributed in the radio frequency drying chamber, and there is also a heating effect in the corners or edges. At this time, the hot air blown out by the air energy heat pump can reduce the temperature difference between the materials and improve the uniformity of drying; at the same time, the hot air can be used as a medium to promptly take away the water vapor evaporated from the surface of the material, thereby cooling the sample surface.

[0036] Based on the above situation, this embodiment adopts the following solution:

[0037] like Figure 1-6 As shown, the present invention includes a box body, an air energy heat pump 4, a dehumidification unit 2, a radio frequency heating system 3, a gas circulation jet unit 5, an automatic weighing unit 6 and an automatic control system. The upper electrode plate 31 is installed in the drying box body 19, the dehumidification unit 2 is installed on the left side of the bottom of the L-shaped plate 13L, and the opening of the dehumidification unit 2 is matched with the heating unit. The airflow circulation unit passes through the heating unit and the dehumidification unit 2 in sequence, and the airflow jet circulation unit is connected end to end to form a circulation path.

[0038] The box body includes a box frame 1, which is a hollow shell. The front side panel of the box frame 1 is provided with a silo door 15 that can be opened and closed and other removable panels. The box frame 1 is provided with a horizontal plate 12, a vertical plate 14 and an L-shaped plate 13. The horizontal plate 12 and the L-shaped plate 13 divide the box body into three chambers: upper, middle and lower.

[0039] The box body between the box frame 1 and the horizontal plate 12 includes a centrifugal fan 51, a top swirl air supply port 52, and a bell-shaped air flow uniform chamber 53. The box frame 1, the horizontal plate 12, and the vertical plate 14 form a drying box 19. The upper end of the drying box 19 has a square hole connected to the bell-shaped air flow uniform chamber 53. A gas jet device 54 is installed downward. The upper electrode plate is below the gas jet device 54 and is tightly assembled with it. The L-shaped plate 13 and the vertical plate 14 form an air outlet 55. The connection between the air outlet 55 and the horizontal plate 12 is connected to the return air duct 56 by a circular pipe. The return air duct 56 is connected to the air inlet of the centrifugal fan 51. The lower compartment formed by the L-shaped plate 13 and the box frame 1 includes a dehumidification unit 2, a controller 71, and a radio frequency generator 33. A moisture through hole 21 is provided at the bottom of the L-shaped plate 13, which is connected to the drying box 19. The dehumidification fan 20 is installed on the left side of the bottom of the L-shaped plate, and the front and rear side plates and the left side plate next to it are provided with dehumidification holes 22. The air flowing through the drying box 19 will have some heavier moisture entering the dehumidification unit from the moisture through hole 21, reducing the moisture in the drying box 19 and playing a certain dehumidification role. When the dehumidification fan is installed in the dehumidification unit, the dehumidification fan 20 can accelerate the extraction of moisture in the drying box 19, thereby accelerating the drying of the gas in the drying box 19.

[0040] One end of the air duct 50 in the air circulation jet unit is connected to the air energy heat pump 4, and the other end is connected to the air inlet of the centrifugal fan 51 and the return air duct 56 respectively. The centrifugal fan 51 can draw the hot air of the air energy heat pump 4 into the circulation channel, and then send it to the bell-mouth air flow uniform chamber 53 through the top swirl air supply port 52, pass through the upper end of the drying box 19, and enter the gas jet device 54. The airflow is sprayed into the drying chamber to reach the surface of the material, and then enters the air outlet 55 through the bottom hole of the lower electrode plate 32. The humid air is discharged by the dehumidification fan. Under the action of the centrifugal fan 51, the airflow returns to the air duct 50 again, completing an airflow cycle.

[0041] The drying box 19 is provided with an automatic material weighing device. The automatic weighing unit 6 is composed of a material tray 62, a material 63, a weighing support 61, and a weighing sensor 64. The weighing sensor is connected to a controller 71. The weighing support 61 of the automatic weighing unit is fixedly mounted on the bottom surface of the L-shaped plate directly below the lower electrode plate 32. There are three weighing sensors 64, which are respectively fixed on the three corners of the bottom of the weighing support 61. The weighing support 61 is made of 5mm thick polytetrafluoroethylene material. The material tray 62 is evenly distributed with many small air holes to facilitate the loss of moisture in the material.

[0042] The radio frequency generator 33 is on the lower right side of the box frame 1. The upper electrode plate 31 and the lower electrode plate are both made of aluminum. The electrode plates are evenly distributed with diamond holes, and they correspond one to one. The two plates are installed opposite each other. The upper electrode plate 31, the gas jet device 54 and the lower electrode plate 32 in the drying box 19 are relatively fixed to the column 11. There are four columns 11, which are respectively fixed to the four corners of the box body formed by the horizontal plate 12, the L-shaped plate 13, the vertical plate 14 and the box frame 1. The material 63 is on the material tray of the automatic weighing device, with the upper electrode plate 31 on the top and the lower electrode plate 32 on the bottom. The material 63 is placed flat in the vertical middle position between the upper electrode plate 31 and the lower electrode plate 32.

[0043] like Figure 2 As shown, for the convenience of viewing, an observation window 16 is provided on the silo door 15, and for the convenience of opening the door, a handle 17 is provided on the silo door 15.

[0044] For easy movement, a moving wheel 18 is provided at the lower end of the box frame 1 .

[0045] like Figure 6 As shown, in this embodiment, the gas jet device 54 includes a nozzle bracket 541 and a plurality of jet components, each of which is composed of a jet pipe 542, a nozzle 543, a sealing ring 544 and a locking nut 545; the nozzles 543 are evenly distributed in a rhombus shape; the air outlet 55 is composed of an L-shaped plate 13, a vertical plate 14 and a lower electrode plate 32, one end of which is connected to the return air duct 56, and the other end is connected to the drying box 19 to form a circulating airflow; one end of the return air duct 56 is connected to the air outlet duct 55, and the other end is connected to the air duct 50 and the air inlet of the centrifugal fan 51.

[0046] There are two optical fiber temperature sensors 34 installed on the right side of the vertical plate 14. The sensor heads are inside the drying box 19, which can monitor the internal temperature of the material 63 and the temperature inside the drying box in real time; the humidity sensor 23 is installed in the drying box 19 on the right side wall of the vertical plate 14, close to the lower electrode plate, and the humidity sensor 23 can monitor the relative humidity in the drying chamber in real time.

[0047] The automatic controller 7 includes a controller 71 and a touch screen 72. The controller is installed on the lower side of the box frame 1. The air energy heat pump 4, the optical fiber temperature sensor 34, the humidity sensor 23, the automatic weighing sensor 64, the radio frequency generator 33 and the centrifugal fan 51 are all connected to the controller. The touch screen 72 is set on the cover plate on the front side of the box frame 1, and the touch screen 72 is electrically connected to the controller 71.

[0048] By monitoring the real-time temperature and humidity data in the drying room and making corresponding adjustments, the drying of materials can be accelerated and the drying efficiency can be improved.

[0049] Embodiment 2:

[0050] like Figure 7 As shown, a method for drying agricultural products, using the radio frequency combined heat pump gas jet dryer in Example 1 to heat, dehumidify and dry the agricultural products, includes the following steps:

[0051] S1. Put the washed and sorted agricultural products into the material tray 62, and use the touch screen 72 to set the drying process parameters: Specifically, rinse the freshly harvested fresh agricultural products with clean water, with a wet basis moisture content of 50% or more, mainly remove the sand on the agricultural products, and then put them into the drying tray and place them in the external environment for 2 hours to remove the surface moisture of the agricultural products, and then place the agricultural products in the material tray 62, set the agricultural products drying process parameters on the touch screen 72, and set 3 drying stages. In the first stage, the radio frequency generator 33 and the gas jet device 54 All work, the drying temperature of the RF heating is set to be below the extreme temperature that the agricultural products can withstand, and the wind speed of the centrifugal fan 51 is set to 1.5m / s; in the second stage, the air energy heat pump 4 and the gas jet device 54 work, the drying temperature is set to be below the extreme temperature that the materials can withstand, and the wind speed of the centrifugal fan 51 is set to 2.0m / s; in the third stage, the air energy heat pump 4, the RF generator 33, and the gas jet device 54 work, the drying temperature is set to be below the extreme temperature that the materials can withstand, and the wind speed of the centrifugal fan 51 is set to 1.0m / s.

[0052] S2, after the drying process parameters are set, the radio frequency heating system 3 is started through the touch screen 72 program setting, and the upper electrode plate 31 is energized to rapidly increase the temperature of the material 63 in the drying chamber, and the first stage of drying is performed, and the moisture content of the agricultural product on a wet basis is reduced;

[0053] S3, the wet basis moisture content of the agricultural products decreases to the first threshold value, the temperature of the optical fiber temperature sensor 34 reaches the first threshold value, the air energy heat pump 4 is turned on, the power supply of the upper electrode plate 31 is cut off, the radio frequency generator 33 is turned off, the air energy heat pump 4 is retained to dry the agricultural products, and the second stage of drying is carried out, and the wet basis moisture content of the agricultural products continues to decrease;

[0054] S4, the wet basis moisture content of the agricultural products decreases to the second threshold value, the temperature of the optical fiber temperature sensor 34 reaches the second threshold value, the radio frequency generator 33 is turned on, the air energy heat pump 4 is retained to dry the agricultural products, and the third stage of drying is carried out, and the wet basis moisture content of the agricultural products continues to decrease.

[0055] S5, the wet basis moisture content of the agricultural products is reduced to the third threshold value, the air energy heat pump 4 is turned off, the radio frequency generator 33 is turned off, and the drying of the agricultural products is completed.

[0056] In order to take into account both the drying effect and the drying efficiency, the drying time of the first stage in step S2 is 30 minutes to 45 minutes; the first threshold in step S3 is above 40%, the temperature threshold is below the allowable temperature limit of the agricultural product, and the drying time of the second stage is 4 hours to 6 hours; the second threshold in step S4 is 20% to 30%, the temperature threshold is above the allowable temperature limit of the agricultural product, and the drying time of the third stage is 6 hours to 8 hours; the third threshold in step S5 is below the safe moisture content of the agricultural product storage.

[0057] This embodiment is suitable for drying processing of various heat-sensitive materials.

[0058] This technical solution overcomes the low safety of the existing traditional sun drying of agricultural products, the slow heating rate in the early stage of drying of agricultural products and the low efficiency in the later stage of drying in single heat pump drying, and the technical problem of uneven drying rate in single radio frequency drying, and the problems of fast drying rate, high drying intensity, and difficult loss of moisture in agricultural products. This technical solution adopts radio frequency combined heat pump gas jet dryer, combines radio frequency drying with air source heat pump drying, sets up a rotating jet air supply uniformity chamber, and installs a gas jet drying device and other drying equipment. The drying procedure is adjusted according to the change of wet basis moisture content of agricultural products in a segmented drying method. The drying rate is fast, the energy consumption is low, the drying efficiency is greatly improved, and the safety of agricultural products after drying is high.

[0059] above Figure 1-7 The radio frequency combined heat pump gas jet dryer and agricultural product drying method shown are specific embodiments of the present invention, which have embodied the substantial characteristics and progress of the present invention. According to actual use needs and under the guidance of the present invention, equivalent modifications in shape, structure, etc. can be made to them, which are all within the protection scope of this scheme.

Claims

1. A radio frequency combined heat pump gas jet dryer, characterized in that: It comprises a box body, a dehumidification unit (2), a radio frequency heating system, an air energy heat pump (4), a gas circulation jet unit, an automatic weighing unit (6) and an automatic control system; The air energy heat pump (4) is arranged on the outside of the box; the inner cavity of the box comprises an upper cavity, a middle cavity, a lower cavity, a vertical return air duct (56) located on one side, and an air outlet duct (55) communicating with the return air duct, wherein the upper cavity accommodates a gas circulation jet unit; the middle cavity accommodates a radio frequency heating system, a support rack, and an automatic weighing unit (6) connected to the support rack; the lower cavity accommodates a dehumidification unit (2); the air flow passes through the air energy heat pump (4), the gas circulation jet unit, the radio frequency heating system, the dehumidification unit (2), the air outlet duct (55), and the return air duct (56) and returns to the gas circulation jet unit; An L-shaped plate is provided below the support rack, and the L-shaped plate is a component of the air outlet duct (55); the dehumidification unit (2) comprises a dehumidification fan (20) and a humidity sensor (23); the dehumidification fan (20) is installed below the bottom of the L-shaped plate (13); the L-shaped plate is provided with a moisture through hole (21) communicating with the dehumidification fan (20); a dehumidification hole (22) communicating with the outside is provided on the box body located in the lower cavity; the humidity sensor (23) is provided in the middle cavity near the support rack; the air energy heat pump (4) is provided on the outside of the box body; The radio frequency heating system comprises an upper electrode plate (31), a lower electrode plate (32), a radio frequency generator (33), and an optical fiber temperature sensor (34); the upper electrode plate (31) is an aluminum plate, and flow holes are evenly distributed on the electrode plate; the lower electrode plate (32) is an aluminum plate, and is located directly below the upper electrode plate (31), and the positions of the openings correspond one-to-one with the flow holes of the upper electrode plate (31); a material tray for placing materials is provided on the support frame, the upper electrode plate (31) is located above the material tray (62), and the lower electrode plate (32) is located below the material tray (62); The radio frequency generator (33) is located at the lower left side of the box body. There are at least two optical fiber temperature sensors (34), one of which is installed on the side of the vertical plate (14) and can be directly inserted into the material (63). The other optical fiber temperature sensor (34) monitors the temperature in the middle cavity. The box body in which the middle cavity is located is a drying box body (19), and the drying box body (19) is composed of a box body frame (1), a horizontal plate (12) and a vertical plate (14). The gas circulation jet unit comprises an air duct (50), a centrifugal fan (51), a top swirl air supply port (52), a bell-shaped air flow uniformity chamber (53), a gas jet device (54), an air outlet duct (55) and an air return duct (56); the air outlet of the air duct (50) is connected to the air inlet of the centrifugal fan (51); the centrifugal fan (51) is installed at the middle position of the top end of the box body; one end of the top swirl air supply port (52) is connected to the air outlet of the centrifugal fan (51); the bell-shaped air flow uniformity chamber (53) is connected to the air outlet of the top swirl air supply port (52); and the gas jet device (54) is connected to the air outlet of the top swirl air supply port (52). 54) is installed on the upper side of the upper electrode plate (31), communicates with the bell-mouth airflow uniform chamber (53) upward, and the downward airflow jet end passes through the flow hole of the upper electrode plate (31) and is tightly assembled, and the gas jet vertically passes through the material (63), the material tray (62) and the lower electrode plate (32); the upper electrode plate (31), the gas jet device (54) and the lower electrode plate (32) are all relatively fixed on the columns (11), and there are four columns (11), and the four columns (11) are respectively fixed on the four corners of the box body formed by the horizontal plate (12), the L-shaped plate (13), the vertical plate (14) and the box body frame; The gas jet device (54) comprises a nozzle bracket (541) and a plurality of jet components, each of which is composed of a jet pipe (542), a nozzle (543), a sealing ring (544) and a locking nut (545); the nozzles (543) are evenly distributed in a rhombus shape; the air outlet duct (55) is composed of an L-shaped plate (13), a vertical plate (14) and a lower electrode plate (32), one end of which is connected to the return air duct (56) and the other end is connected to the drying box (19) to form a circulating airflow; one end of the return air duct (56) is connected to the air outlet duct (55), and the other end is connected to the air duct (50) and the air inlet of the centrifugal fan (51).

2. The radio frequency combined heat pump gas jet dryer according to claim 1, characterized in that: The automatic weighing unit (6) comprises a material tray (62), material (63), a weighing support (61), and a weighing sensor (64); the weighing support (61) is fixedly mounted on the bottom surface of an L-shaped plate below a lower electrode plate (32); there are at least three weighing sensors (64), and the three weighing sensors (64) are respectively fixed on three corners of the bottom of the weighing support (61); the humidity sensor (82) is mounted on the side wall of the drying box (19) near the lower electrode plate; and the material tray (62) has a plurality of evenly distributed small holes.

3. The radio frequency combined heat pump gas jet dryer according to claim 2, characterized in that: The automatic control system comprises a controller (71) and a touch screen (72); the controller (71) is mounted at the bottom of the cabinet frame (1); the air energy heat pump (4), the optical fiber temperature sensor (34), the humidity sensor (23), the automatic weighing sensor (64), and the radio frequency generator (33) are all connected to the controller (71); the touch screen (72) is arranged on the equipment door on the front side of the cabinet frame (1); and the touch screen (72) is connected to the controller (71) by wires.

4. A method for drying agricultural products using a radio frequency combined heat pump gas jet dryer as claimed in any one of claims 1 to 3, wherein the agricultural products are dried using the radio frequency combined heat pump gas jet dryer, characterized in that: The following steps are involved: S1, placing the washed and sorted agricultural products into a material tray (62), and using a touch screen (72) in an automatic control system to set drying process parameters; S2. After the drying process parameters are set, the program is started through the touch screen, and the radio frequency heating system and the gas jet device 54 are started to increase the temperature of the material in the drying chamber, and the first stage of drying is carried out, and the moisture content of the agricultural product on a wet basis is reduced; S3, the wet basis moisture content of the agricultural products is reduced to the first threshold value, the air energy heat pump 4 is turned on, the gas jet device 54 is retained, and the radio frequency heating system is turned off at the same time, and the second stage of drying is carried out, and the wet basis moisture content of the agricultural products continues to decrease; S4, the wet basis moisture content of the agricultural products is reduced to the second threshold value, the radio frequency heating system is turned on, the air energy heat pump 4 and the gas jet device 54 are retained, and the third stage of drying is carried out, and the wet basis moisture content of the agricultural products continues to decrease; S5. The wet basis moisture content of the agricultural products is reduced to the third threshold value, the air energy heat pump is turned off 4. The radio frequency heating system is turned off, the equipment stops running, and the drying of the agricultural products is completed.

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