CN116481263A - Cereal microwave drying method and device - Google Patents

Cereal microwave drying method and device Download PDF

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Publication number
CN116481263A
CN116481263A CN202211327428.8A CN202211327428A CN116481263A CN 116481263 A CN116481263 A CN 116481263A CN 202211327428 A CN202211327428 A CN 202211327428A CN 116481263 A CN116481263 A CN 116481263A
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CN
China
Prior art keywords
drying
grains
water content
grain
microwave
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Pending
Application number
CN202211327428.8A
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Chinese (zh)
Inventor
孙铜生
杨震
曹冉
王静平
王凯
刘家豪
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Anhui Polytechnic University
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Anhui Polytechnic University
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Priority to CN202211327428.8A priority Critical patent/CN116481263A/en
Publication of CN116481263A publication Critical patent/CN116481263A/en
Pending legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B1/00—Preliminary treatment of solid materials or objects to facilitate drying, e.g. mixing or backmixing the materials to be dried with predominantly dry solids
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B9/00—Preservation of edible seeds, e.g. cereals
    • A23B9/08—Drying; Subsequent reconstitution
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
    • F26B17/02—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by belts carrying the materials; with movement performed by belts or elements attached to endless belts or chains propelling the materials over stationary surfaces
    • F26B17/04—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by belts carrying the materials; with movement performed by belts or elements attached to endless belts or chains propelling the materials over stationary surfaces the belts being all horizontal or slightly inclined
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
    • F26B25/001—Handling, e.g. loading or unloading arrangements
    • F26B25/002—Handling, e.g. loading or unloading arrangements for bulk goods
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
    • F26B25/22—Controlling the drying process in dependence on liquid content of solid materials or objects
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/32—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action
    • F26B3/34—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action by using electrical effects
    • F26B3/347—Electromagnetic heating, e.g. induction heating or heating using microwave energy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B2200/00—Drying processes and machines for solid materials characterised by the specific requirements of the drying good
    • F26B2200/06—Grains, e.g. cereals, wheat, rice, corn
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P60/00—Technologies relating to agriculture, livestock or agroalimentary industries
    • Y02P60/80—Food processing, e.g. use of renewable energies or variable speed drives in handling, conveying or stacking
    • Y02P60/85—Food storage or conservation, e.g. cooling or drying

Abstract

The invention relates to the technical field of microwave drying, and discloses a grain microwave drying method which comprises four steps of grain humidity detection, grain analysis, grain adsorption and grain drying. According to the method, through the pre-drying analysis process, the water content of the part of the grain with the water content being greater than the selected balance water content is evaporated, the maximum water content value of the grain is reduced, and in the pre-drying adsorption process, the part of the grain with the water content being lower than the selected balance water content absorbs the water, and the minimum water content value of the grain is improved, so that the difference of the water content of the grain is reduced, the uniformity of the water content of the grain is improved, the problem of excessive local drying of the grain caused by uneven water content distribution in the normal drying process is avoided, and the quality of the dried grain is improved.

Description

Cereal microwave drying method and device
Technical Field
The invention relates to the technical field of microwave drying, in particular to a grain microwave drying method and device.
Background
Microwaves are electromagnetic waves having a wavelength ranging from 0.001 to 1m, a frequency ranging from 0.3 to 300GHz, and a penetrating power. The magnetron of the microwave generator receives the power to generate microwaves, the microwaves are transmitted to the microwave heater through the waveguide, and the materials to be heated are heated under the action of the microwave field. Microwave heating is different from a general heating mode, and the latter is conducted heating from the outside to the inside by heat radiation through an external heat source; whereas microwave heating is bulk heating of a material in an electromagnetic field caused by dielectric losses. This heating converts electromagnetic energy into thermal energy, which is transmitted in the form of electromagnetic waves through space or a medium, and has a close relationship with the heating process of the substance and the polarization of molecules inside the substance. The polarization of the microwave field by the medium is manifested as loss of electric field current density, the dielectric constant of the general material is not more than 50, and the dielectric constant of water is 78.54. When an aqueous material is placed in an electromagnetic field generated by a microwave generator, the microwave field periodically changes the direction of the applied electric field at a rate of hundreds of millions of times per second, causing water molecules to oscillate rapidly, producing a significant thermal effect, and thus causing the interior and surface temperatures of the material to rise rapidly simultaneously.
The microwave drying has selectivity, the part with high moisture content absorbs more heat, the moisture is rapidly dispersed, and the temperature rise is higher than other parts. The molecular movement is more active when the temperature is increased, and the capability of absorbing microwaves of the material is enhanced. For a batch of grains, the moisture content may vary greatly from grain to grain, and the non-uniformity of moisture among grains is one of the main factors that cause the non-uniformity of moisture of the dried grains. In the case of single grains, there is a difference in moisture content between the embryo and endosperm, and there is a difference in moisture content between the inner and outer layers of the grain, thus affecting the drying characteristics of the grain.
Disclosure of Invention
Aiming at the defects of the prior grain microwave drying method and device in the use process, the invention provides the grain microwave drying method and device, which have the advantage of uniform drying and solve the problems in the prior art.
The invention provides the following technical scheme: a method for microwave drying of cereal grains, comprising the steps of:
step one, detecting humidity of grains: detecting average humidity of grains by using a moisture meter, selecting balanced moisture of the grains similar to the average humidity according to the types of the grains, and determining corresponding temperature and relative humidity of the grains during analysis and adsorption respectively when the moisture content of the grains is equal to the balanced moisture;
step two, cereal analysis: calculating the voltage and heating time of a microwave heater in the pre-drying cavity according to the analysis temperature of the grains when the water content of the grains determined in the first step is equal to the equilibrium water content; according to the relative humidity in the pre-drying cavity when the water content of the grains is equal to the equilibrium water content and the grains are in analysis, calculating the air pressure and the steam quantity of air required to be input into the pre-drying cavity, and pre-drying the grains in the pre-drying cavity;
step three, cereal adsorption: calculating the voltage and heating time of a microwave heater in the pre-drying cavity according to the adsorption temperature of the grains when the water content of the grains determined in the first step is equal to the equilibrium water content; according to the relative humidity in the pre-drying cavity when the water content of the grains is equal to the equilibrium water content and the grains are adsorbed, calculating the air pressure and the steam quantity of air required to be input into the pre-drying cavity, and pre-drying the grains in the pre-drying cavity;
step four, grain drying: the grains enter the drying cavity, the humidity of the grains is detected by the moisture meter, and then the parameters of the microwave heater in the drying cavity and the speed of the conveying belt are adjusted according to the humidity of the grains.
Preferably, in the second step and the third step, the hot air required in the pre-drying cavity is conveyed to the pre-drying cavity by the dehumidifying system.
Preferably, the number of the drying cavities is at least one, and a separate conveyor belt is arranged in each drying cavity.
The utility model provides a cereal microwave drying device, includes the frame, install predrying chamber and normal dry chamber and microwave suppressor in the frame, predrying chamber, normal dry intracavity all are provided with the conveyer belt, still are equipped with the cooling tube that is located the conveyer belt below in predrying chamber, the both ends of frame are equipped with feeder and tripper respectively, conveyer belt in the feeder extends to predrying intracavity, and the conveyer belt in the normal dry chamber that is close to the tripper extends to in the tripper, predrying chamber, normal dry intracavity all are provided with microwave heater, microwave heater electric connection has the controller, thermoscope, hygrometer and hygrometer are all installed to the inner chamber in predrying chamber, normal dry chamber, thermoscope and controller electric connection.
Preferably, the frame is provided with a dehumidifying device, an air inlet end of the dehumidifying device is communicated with the inner cavities of the pre-drying cavity and the normal drying cavity through a branch pipe, the branch pipes are provided with electric control valves, an output end of the dehumidifying device is communicated with the atmosphere and the branch pipes arranged on the pre-drying cavity, and the dehumidifying device and the electric control valves are electrically connected with a controller.
Preferably, the conveyer belt includes the area body, be provided with vertical hard board on the area body, be connected with the bag between two adjacent vertical hard boards, cereal has been placed to the top of bag, area body, vertical hard board and bag enclose into the heat absorption chamber.
Preferably, the transmitter is installed to the side of bag, install the receiver on the inner wall of frame, the receiver is used for receiving the signal of transmitter, receiver and controller electric connection.
Preferably, electric control sealing doors are arranged between the pre-drying cavity and the normal drying cavity and between the normal drying cavity and the normal drying cavity, and the electric control sealing doors are electrically connected with the controller.
Preferably, the controller comprises a collecting unit, a storage unit, a comparing unit, a calculating unit and a driving unit, wherein the input end of the collecting unit is connected with the output ends of the thermometer, the hygrometer and the hygrometer, the input end of the comparing unit is connected with the output ends of the collecting unit and the comparing unit, the output end of the comparing unit is connected with the input end of the calculating unit, the calculating unit comprises a preheating parameter calculating module and a drying parameter calculating module, the output ends of the preheating parameter calculating module and the drying parameter calculating module are electrically connected with the driving unit, and the driving unit is connected with the microwave heater, the dehumidifying device, the branched pipes and the conveyor belt.
The invention has the following beneficial effects:
1. according to the method, through the pre-drying analysis process, the water content of the part of the grain with the water content being greater than the selected balance water content is evaporated, the maximum water content value of the grain is reduced, and in the pre-drying adsorption process, the part of the grain with the water content being lower than the selected balance water content absorbs the water, and the minimum water content value of the grain is improved, so that the difference of the water content of the grain is reduced, the uniformity of the water content of the grain is improved, the problem of excessive local drying of the grain caused by uneven water content distribution in the normal drying process is avoided, and the quality of the dried grain is improved.
2. According to the invention, the whole batch of grains is divided into small batches by utilizing the structure consisting of the bag and the heat absorption cavity, so that the temperature of the small batch of grains is monitored by paving the grains on the bag, the contact area between the bag and the grains is increased, and the accuracy of measuring the temperature of the grains is improved.
Drawings
FIG. 1 is a drying flow chart of the present invention;
FIG. 2 is a schematic diagram of a microwave drying apparatus according to the present invention;
FIG. 3 is a schematic view of a conveyor belt of the present invention;
FIG. 4 is a top view of a conveyor belt of the present invention;
fig. 5 is a block diagram of the controller of the present invention.
In the figure: 1. a frame; 2. a pre-drying chamber; 3. a normal drying chamber; 4. a microwave suppressor; 5. a conveyor belt; 501. a belt body; 502. vertical hard plates; 503. a pouch; 504. a heat absorption chamber; 6. a feeder; 7. a discharger; 8. a dehumidifying device; 9. a branch pipe; 10. an electric control valve; 11. a microwave heater; 12. a temperature measuring instrument; 13. a moisture meter; 14. a hygrometer; 15. a controller; 1501. an acquisition unit; 1502. a storage unit; 1503. a comparison unit; 1504. a calculation unit; 1540. a preheating parameter calculation module; 1541. a drying parameter calculation module; 1505. a driving unit; 16. a transmitter; 17. a receiver; 18. an electrically controlled closing door.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, a method and apparatus for microwave drying of grains include the following steps:
step one, detecting humidity of grains: detecting the average humidity of the grains by using a moisture meter, and determining the corresponding temperature and relative humidity of the grains during analysis and adsorption respectively when the water content of the grains is equal to the equilibrium water content;
step two, cereal analysis: calculating the voltage and heating time of a microwave heater in the pre-drying cavity according to the analysis temperature of the grains when the water content of the grains determined in the first step is equal to the equilibrium water content; according to the relative humidity in the pre-drying cavity when the water content of the grains is equal to the equilibrium water content and the grains are in analysis, calculating the air pressure and the steam quantity of air required to be input into the pre-drying cavity, and pre-drying the grains in the pre-drying cavity;
step three, cereal adsorption: calculating the voltage and heating time of a microwave heater in the pre-drying cavity according to the adsorption temperature of the grains when the water content of the grains determined in the first step is equal to the equilibrium water content; according to the relative humidity in the pre-drying cavity when the water content of the grains is equal to the equilibrium water content and the grains are adsorbed, calculating the air pressure and the steam quantity of air required to be input into the pre-drying cavity, and pre-drying the grains in the pre-drying cavity;
step four, grain drying: the grains enter the drying cavity, the humidity of the grains is detected by the moisture meter, and then the parameters of the microwave heater in the drying cavity and the speed of the conveying belt are adjusted according to the humidity of the grains.
In the second step and the third step, hot air in the drying cavity is conveyed to the pre-drying cavity by the hot air required in the pre-drying cavity through a dehumidifying system. When the grains are dried, the relative humidity of air in the pre-drying cavity can be adjusted when the grains are pre-dried, hot air emitted in the normal drying process of the grains in the previous batch can be reheated or cooled by the dehumidifying system and conveyed to the pre-drying cavity, and water vapor required in the pre-drying cavity can be conveyed into the pre-drying cavity through the dehumidifying system, so that the effect of energy source solving is achieved.
At least one drying chamber is provided, and a separate conveyor belt is arranged in each drying chamber. The microwave equipment of continuous drying among the prior art is mostly formed through many drying chamber intercommunication, all needs to set up a microwave generator in every drying chamber, and the quantity of conveyer belt is only one, therefore the microwave generator quantity that needs is more, and through all setting up a conveyer belt in every drying chamber in this application, can adjust the duration of cereal in the drying chamber through the transfer rate of adjustment conveyer belt, consequently can reduce the quantity of drying chamber, reduce cost.
In the above steps, the first to third steps are pre-drying processes, and the fourth step is a normal drying process.
Referring to fig. 2, a grain microwave drying device comprises a frame 1, a pre-drying cavity 2 and a normal drying cavity 3 are mounted on the frame 1, the pre-drying cavity 2 and the normal drying cavity 3 are identical in structure, a conveying belt 5 is arranged in each of the pre-drying cavity 2 and the normal drying cavity 3, a cooling pipe below the conveying belt 5 is further arranged in each of the pre-drying cavities 2 and used for cooling grains in the pre-drying cavities 2, a feeder 6 and a discharger 7 are respectively arranged at two ends of the frame 1, the conveying belt 5 in the feeder 6 extends into the pre-drying cavity 2, the conveying belt 5 in the normal drying cavity 3 close to the discharger 7 extends into the discharger 7, a microwave heater 11 is arranged in each of the pre-drying cavity 2 and the normal drying cavity 3, the microwave heater 11 is electrically connected with a controller 15, a temperature measuring instrument 12, a moisture meter 13 and a hygrometer 14 are mounted in each of the inner cavities of the pre-drying cavity 2 and the normal drying cavity 3, and the temperature measuring instrument 12, the moisture meter 13 and the hygrometer 14 are electrically connected with the controller 15.
Referring to fig. 3, the conveyor belt 5 includes a belt body 501, a vertical hard plate 502 is disposed on the belt body 501, a bag 503 is connected between two adjacent vertical hard plates 502, grains are placed above the bag 503, a heat absorbing cavity 504 is enclosed by the belt body 501, the vertical hard plates 502 and the bag 503, heat absorbing cavity 504 is filled with heat sensitive gas, referring to fig. 4, a transmitter 16 is mounted on a side surface of the bag 503, a receiver 17 is mounted on an inner wall of the frame 1, the receiver 17 is used for receiving signals of the transmitter 16, and the transmitter 16, the receiver 17 are electrically connected with a controller 15. When the temperature of the grains increases after absorbing microwaves emitted from the microwave applicator 11, the heat of the grains is conducted through the pocket 503 into the heat absorbing chamber 504, and the heat sensitive gas absorbs the heat to expand, so that the center point of the pocket 503 moves upward, and the position of the transmitter 16 located at the center of the pocket 503 correspondingly increases, and thus the height of the signal received by the receiver 17 from the transmitter 16 increases. By the collection and conversion of this height value, the temperature of the grain can be moved. Compared with the temperature sensor used in the prior art, the contact area between the bag 503 and the grains is large in the application, so that the detection area is also large, and the detection accuracy is higher. In this application, a plurality of bags 503 and heat absorbing cavities 504 are disposed on the whole belt body 501, so that a batch of grains on the conveyor belt 5 can be divided into a plurality of small batches, the temperature of each small batch of grains can be detected, if the height difference of the signals received by the plurality of receivers 17 from the transmitters 16 is smaller, the temperature difference between the small batches of grains is smaller, and further, the humidity difference of each small batch of grains is smaller, which is because the microwave drying has selectivity, the parts with high moisture content absorb more heat, the moisture loss is quick, the temperature rise is higher than other parts, the molecular movement is more active due to the temperature rise, and the capability of absorbing microwaves by the materials is enhanced, so that whether the moisture content of the batch of grains is uniform or not can be known through statistics of the signal transmitting height of each transmitter 16, and if the moisture content distribution is uniform, the drying is also uniform and the drying is qualified; if the moisture content of the batch of grains is not uniform, grains with low moisture content are excessively dried under the same power of microwaves, and grains with high moisture content do not meet the drying requirement, and the process of pre-drying and normal drying is needed to be carried out again for the batch of grains. In addition, when the gas expansion degree in the heat absorbing cavity 504 is too large, the grains on the bag 503 flow to two sides, so that the grains are mixed, and as the grains are not in the current bag 503, the heat-sensitive gas in the heat absorbing cavity 504 can not absorb the heat of the grains, so that the volume of the heat-sensitive gas is reduced and is sunken downwards, the grains accumulated on two sides of the bag 503 roll down to the sunken bag 503, and the grains are promoted to be mixed in the process of flowing to the two sides again, so that the accuracy of detecting the temperature of the grains is further improved.
The frame 1 is provided with a dehumidifying device 8, the air inlet end of the dehumidifying device 8 is communicated with the inner cavities of the pre-drying cavity 2 and the normal drying cavity 3 through a branch pipe 9, the branch pipe 9 is provided with an electric control valve 10, the output end of the dehumidifying device 8 is communicated with the atmosphere and the branch pipe 9 arranged on the pre-drying cavity 2, and the dehumidifying device 8 and the branch pipe 9 are electrically connected with a controller 15. That is, the dehumidifying device 8 can not only discharge the wet air in the pre-drying chamber 2 and the normal drying chamber 3, but also convey the air with humidity and temperature adjusted into the pre-drying chamber 2, so as to adjust the steam pressure of the air in the pre-drying chamber 2 and keep the air, and after a period of drying, when the steam pressure on the surface of the grains is equal to the steam pressure of the air in the pre-drying chamber 2, the moisture in the grains can reach the corresponding equilibrium moisture.
An electric control sealing door 18 is arranged between the adjacent pre-drying cavity 2 and the normal drying cavity 3 and between the normal drying cavity 3 and the normal drying cavity 3, and the electric control sealing door 18 is electrically connected with the controller 15. The electronically controlled closing door 18 is used to separate and keep sealed the pre-drying chamber 2, the normal drying chamber 3 in order to adjust the humidity and temperature of the air in the pre-drying chamber 2, the normal drying chamber 3.
Referring to fig. 5, the controller 15 includes an acquisition unit 1501, a storage unit 1502, a comparison unit 1503, a calculation unit 1504 and a driving unit 1505, wherein the input end of the acquisition unit 1501 is connected with the output ends of the thermometer 12, the hygrometer 13 and the hygrometer 14, the storage unit 1502 stores a table of equilibrium moisture relation values of different types of grains at various temperatures and relative air humidity, the data in the table are obtained by setting the temperature and the air humidity of different grains as variables, and the equilibrium moisture is obtained as a result, and the test method is quite mature in the prior art, and is not repeated in the application; the input end of the comparison unit 1503 is connected with the output ends of the acquisition unit 1501 and the comparison unit 1503, the output end of the comparison unit 1503 is connected with the input end of the calculation unit 1504, the calculation unit 1504 comprises a preheating parameter calculation module 1540 and a drying parameter calculation module 1541, the output ends of the preheating parameter calculation module 1540 and the drying parameter calculation module 1541 are electrically connected with the driving unit 1505, and the driving unit 1505 is connected with the microwave heater 11, the dehumidifying device 8, the branch pipe 9 and the conveyor belt 5.
The application method of the invention is as follows:
the grains in the feeder 6 are laid on the conveyor belt 5, and under the gravity action of the grains, the bag 503 is depressed downwards, and the heat-sensitive gas in the heat absorbing cavity 504 is in a normal state as shown in fig. 3 because the heat is not absorbed; the grains enter the pre-drying cavity 2, and the humidity of the whole batch of grains is detected by the moisture meter 13 and is recorded as the average humidity; however, there may be a case where the humidity of a part of the grains is large and the humidity of a part of the grains is small and the humidity is not uniform; and for a grain, there may be uneven humidity, so that pre-drying is performed;
the temperature detector 12 detects the temperature of the air in the pre-drying cavity 2, the hygrometer 14 detects the humidity of the air in the pre-drying cavity 2, the average value of the heights of the transmitters 16 received by the receiver 17 is taken as the temperature of the whole batch of grains, then the analysis and adsorption equilibrium moisture value closest to the values of the three parameters is selected according to the grain temperature, the grain type and the air relative humidity in the pre-drying cavity 2 obtained by the equilibrium moisture test, the corresponding fixed grain temperature value in the table and the fixed air relative humidity value in the pre-drying cavity 2 are determined, the grains are heated by the microwave heater 11, the temperature of the grains reaches the corresponding fixed grain temperature value and the fixed grain temperature value is kept, and the humidity of the fixed air relative humidity value is kept by the moisture removing device 8 for the grains in the pre-drying cavity 2, and when the moisture detector 13 detects that the humidity of the grains reaches the equilibrium moisture value, the grains are stopped drying;
according to the current temperature value of the grain and the current water content of the grain, the air relative humidity value is found out according to the conditions lower than the current temperature value of the grain and higher than the current water content of the grain in the equilibrium water relation value table obtained through the test, the temperature of the grain can be naturally cooled, and the grain can be cooled through a cooling pipe arranged below the conveyor belt 5 in the frame 1, so that the temperature of the grain reaches the value in the table, the air relative humidity in the pre-drying cavity 2 is kept through the dehumidifying device 8, the grain temperature is kept, and when the moisture meter 13 detects that the water content of the grain is the corresponding equilibrium water in the table, the adsorption process is stopped.
In the pre-drying process, the uniformity of the water content distribution in the grains is balanced by the desorption and adsorption of the water in the grains. Specifically, during grain analysis, the part of the grain with the water content greater than the selected equilibrium moisture is dried, the water content is reduced, but the part with the water content less than the equilibrium moisture is not excessively dried because the current equilibrium moisture is small in the gap between the actual water content of the grain; in the grain adsorption process, the part with little original moisture of the grain adsorbs moisture, the part with large moisture does not absorb moisture if the part is higher than the equilibrium moisture, and absorbs moisture if the part is lower than the equilibrium moisture, and the equilibrium moisture is closest to the real moisture value of the grain, so that the moisture absorbed by the grain is smaller. Through resolving and adsorbing two processes, the uniformity of water content distribution in the grains is improved, and the problem of excessive local drying of the grains in the normal drying process is avoided, so that the uniformity of grain drying is improved, and the quality of grain drying is improved.
In addition, the equilibrium moisture relation value table is obtained by performing moisture equilibrium tests on different types of grains at different temperatures and different air humidities, and specific values are set according to data in the equilibrium moisture relation value table in the subsequent practical application.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (9)

1. A method for microwave drying of cereal grains, comprising the steps of:
step one, detecting humidity of grains: detecting average humidity of grains by using a moisture meter, selecting balanced moisture of the grains similar to the average humidity according to the types of the grains, and determining corresponding temperature and relative humidity of the grains during analysis and adsorption respectively when the moisture content of the grains is equal to the balanced moisture;
step two, cereal analysis: calculating the voltage and heating time of a microwave heater in the pre-drying cavity according to the analysis temperature of the grains when the water content of the grains determined in the first step is equal to the equilibrium water content; according to the relative humidity in the pre-drying cavity when the water content of the grains is equal to the equilibrium water content and the grains are in analysis, calculating the air pressure and the steam quantity of air required to be input into the pre-drying cavity, and pre-drying the grains in the pre-drying cavity;
step three, cereal adsorption: calculating the voltage and heating time of a microwave heater in the pre-drying cavity according to the adsorption temperature of the grains when the water content of the grains determined in the first step is equal to the equilibrium water content; according to the relative humidity in the pre-drying cavity when the water content of the grains is equal to the equilibrium water content and the grains are adsorbed, calculating the air pressure and the steam quantity of air required to be input into the pre-drying cavity, and pre-drying the grains in the pre-drying cavity;
step four, grain drying: the grains enter the drying cavity, the humidity of the grains is detected by the moisture meter, and then the parameters of the microwave heater in the drying cavity and the speed of the conveying belt are adjusted according to the humidity of the grains.
2. A method of microwave drying grain according to claim 1, wherein: in the second step and the third step, the hot air required in the pre-drying cavity is conveyed to the pre-drying cavity by utilizing a dehumidifying system.
3. A method of microwave drying grain according to claim 1, wherein: at least one drying cavity is arranged, and a separate conveyor belt is arranged in each drying cavity.
4. A cereal microwave drying device according to any of the claims 1-3 comprising a frame (1), said frame (1) being provided with a pre-drying chamber (2) and a normal drying chamber (3) and a microwave suppressor (4), characterized in that: the utility model discloses a drying device for drying a food, including frame (1), conveyer belt (5) are all provided with in predrying chamber (2), normal drying chamber (3), still be equipped with the cooling tube that is located conveyer belt (5) below in predrying chamber (2), the both ends of frame (1) are equipped with feeder (6) and tripper (7) respectively, conveyer belt (5) in feeder (6) extend to in predrying chamber (2), conveyer belt (5) in normal drying chamber (3) near tripper (7) extend to in tripper (7), all be provided with microwave heater (11) in predrying chamber (2), normal drying chamber (3), microwave heater (11) electric connection has controller (15), thermoscope (12), hygrometer (13) and hygrometer (14) are all installed to the inner chamber in predrying chamber (2), normal drying chamber (3), thermoscope (13) and hygrometer (14) and controller (15) electric connection.
5. A cereal microwave drying apparatus as claimed in any one of the claims 4, wherein: install damp device (8) on frame (1), the inlet end of damp device (8) is linked together through being in charge of (9) with the inner chamber in predrying chamber (2), normal drying chamber (3), all install automatically controlled valve (10) on being in charge of (9), the output of damp device (8) is linked together with atmosphere and being in charge of (9) of installing on predrying chamber (2), damp device (8) and automatically controlled valve (10) all are with controller (15) electric connection.
6. A cereal microwave drying apparatus as claimed in any one of the claims 4, wherein: the conveying belt (5) comprises a belt body (501), vertical hard plates (502) are arranged on the belt body (501), a bag (503) is connected between two adjacent vertical hard plates (502), grains are placed above the bag (503), and a heat absorption cavity (504) is formed by enclosing the belt body (501), the vertical hard plates (502) and the bag (503).
7. A cereal microwave drying apparatus as claimed in any one of the claims 6, wherein: the side face of the bag (503) is provided with a transmitter (16), the inner wall of the frame (1) is provided with a receiver (17), the receiver (17) is used for receiving signals of the transmitter (16), and the transmitter (16), the receiver (17) and the controller (15) are electrically connected.
8. A cereal microwave drying apparatus as claimed in any one of the claims 4, wherein: an electric control sealing door (18) is arranged between the pre-drying cavity (2) and the normal drying cavity (3) and between the normal drying cavity (3) and the normal drying cavity (3), and the electric control sealing door (18) is electrically connected with the controller (15).
9. A cereal microwave drying apparatus as claimed in any one of the claims 4, wherein: the controller (15) comprises a collection unit (1501), a storage unit (1502), a comparison unit (1503), a calculation unit (1504) and a driving unit (1505), wherein the input end of the collection unit (1501) is connected with the output ends of the thermometer (12), the hygrometer (13) and the hygrometer (14), the input end of the comparison unit (1503) is connected with the output ends of the collection unit (1501) and the comparison unit (1503), the output end of the comparison unit (1503) is connected with the input end of the calculation unit (1504), the calculation unit (1504) comprises a preheating parameter calculation module (1540) and a drying parameter calculation module (1541), the output ends of the preheating parameter calculation module (1540) and the drying parameter calculation module (1541) are electrically connected with the driving unit (1505), and the driving unit (1505) is connected with the microwave heater (11), the dehumidifying device (8), the branch pipe (9) and the conveying belt (5).
CN202211327428.8A 2022-10-27 2022-10-27 Cereal microwave drying method and device Pending CN116481263A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117722841A (en) * 2024-02-07 2024-03-19 云南师范大学 Agricultural material drying method based on temperature and humidity feedback microwave control

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117722841A (en) * 2024-02-07 2024-03-19 云南师范大学 Agricultural material drying method based on temperature and humidity feedback microwave control
CN117722841B (en) * 2024-02-07 2024-04-19 云南师范大学 Agricultural material drying method based on temperature and humidity feedback microwave control

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