CN111322843A - Multi-layer vacuum radio frequency-hot air combined drying method and equipment for rhizome traditional Chinese medicinal materials - Google Patents

Multi-layer vacuum radio frequency-hot air combined drying method and equipment for rhizome traditional Chinese medicinal materials Download PDF

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Publication number
CN111322843A
CN111322843A CN202010296712.8A CN202010296712A CN111322843A CN 111322843 A CN111322843 A CN 111322843A CN 202010296712 A CN202010296712 A CN 202010296712A CN 111322843 A CN111322843 A CN 111322843A
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electrode plate
air
pipeline
electromagnetic valve
anode electrode
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CN111322843B (en
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郑志安
姜大龙
高磊
陈书峰
王文杰
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China Agricultural University
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China Agricultural University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B9/00—Machines or apparatus for drying solid materials or objects at rest or with only local agitation; Domestic airing cupboards
    • F26B9/06—Machines or apparatus for drying solid materials or objects at rest or with only local agitation; Domestic airing cupboards in stationary drums or chambers
    • F26B9/066—Machines or apparatus for drying solid materials or objects at rest or with only local agitation; Domestic airing cupboards in stationary drums or chambers the products to be dried being disposed on one or more containers, which may have at least partly gas-previous walls, e.g. trays or shelves in a stack
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B23/00—Heating arrangements
    • F26B23/04—Heating arrangements using electric heating
    • 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
    • F26B25/06—Chambers, containers, or receptacles
    • F26B25/14—Chambers, containers, receptacles of simple construction
    • F26B25/18—Chambers, containers, receptacles of simple construction mainly open, e.g. dish, tray, pan, rack
    • 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
    • F26B25/225—Controlling the drying process in dependence on liquid content of solid materials or objects by repeated or continuous weighing of the material or a sample thereof
    • 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
    • F26B5/00—Drying solid materials or objects by processes not involving the application of heat
    • F26B5/04—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum

Abstract

The invention belongs to the technical field of traditional Chinese medicinal material processing, and particularly relates to a multi-layer vacuum radio frequency-hot air combined drying method and device for rhizome traditional Chinese medicinal materials, wherein the method comprises the following steps: the system comprises a circulating hot air drying system, a radio frequency heating system, a pulsating vacuum generation system and an automatic control system; the circulating hot air drying system comprises a return air pipeline (9), a return air pipeline electromagnetic valve (11), a centrifugal fan (13), an air inlet pipeline (14), an axial flow fan (15) and the like; the automatic control system comprises a human-computer interaction interface (4); the pulsating vacuum generating system comprises a drain valve (33), a suction pipeline (34) and the like; the radio frequency heating system comprises an optical fiber temperature sensor (26), a material (27), a material tray (28), a weighing bracket (29), a drying box body (47) and the like; the change conditions of the medium and the material (27) in the drying box body (47) are monitored by a sensor in the drying process, and the analysis, decision and execution are performed based on an automatic control system, so that the whole set of equipment has the characteristics of high automation degree, low labor intensity and the like.

Description

Multi-layer vacuum radio frequency-hot air combined drying method and equipment for rhizome traditional Chinese medicinal materials
Technical Field
The invention belongs to the technical field of traditional Chinese medicinal material processing, and particularly relates to a multi-layer vacuum radio frequency-hot air combined drying method and device for rhizome traditional Chinese medicinal materials.
Background
The rhizome Chinese medicinal materials of gastrodia elata, pseudo-ginseng and salvia miltiorrhiza which are large in size are used as rare Chinese medicinal materials, the added value is high, and the problems of mildew, rot and deterioration are easy to occur due to high water content after the picking. The production place is mostly processed by natural airing and drying in a drying room, and the problems of long drying time, hollow interior, reduced quality and the like generally exist. Because this kind of rhizome class medicinal material is bulky, the convection current, conduction mode heating are adopted mostly to current drying technique, and is better to the slice medicinal material effect, but to the bulk medicinal material of great volume surface heating rate fast, inside intensification is slow. In addition, the medicinal material is bulky, the internal moisture diffusion path is long, the drying process is slow, the medicinal components have heat sensitivity, long-time heat accumulation has adverse effects on the medicinal components, and the existing drying technology is not favorable for drying the medicinal components. The vacuum radio frequency-hot air combined drying technology is that in integrated combined drying equipment, radio frequency can penetrate through the interior of a material to cause oscillation migration of polar molecules and charged ions in the material, so that the temperature of the material is rapidly increased from inside to outside; the boiling point of water is reduced in the vacuum stage, the evaporated water of the material can be rapidly removed, the pulse generation stage is favorable for breaking the partial pressure balance between the surface of the material and the medium water vapor, the water evaporation on the surface of the material is favorable, and the mass transfer power is increased; the hot wind energy washes and wraps the surface of the material in the hot wind drying process, so that the temperature of each position on the surface of the material can be uniformly increased, and meanwhile, the hot wind drying structure is simple and the cost is low. The method adopts a radio frequency-vacuum-hot air drying mode as a novel drying technology in different drying stages, has the advantages of fast material temperature rise, short drying time, good product quality, low drying energy consumption and the like, and is particularly suitable for drying traditional Chinese medicinal materials with larger volume.
The prior vacuum radio frequency-hot air combined drying technology has a plurality of defects, which restricts the popularization and application of the technology.
Most of the existing radio frequency drying is of a double-layer parallel polar plate type, and the loading capacity is small. In the radio-frequency heating process, the edge temperature of the material tray is obviously higher than the material temperature of the central area of the material tray due to the fact that the edge effect, namely the electric field lines at the edge of the material tray are bent, and the electric field density at the edge is increased; along with the reduction of the water content of the material, the dielectric property of the material is gradually reduced, the effect of radio frequency dielectric heating can be gradually attenuated, a high-frequency generator generates alternating high-frequency electromagnetic waves when the radio frequency works, and a large amount of electric energy can be consumed when the radio frequency works for a long time.
Most of the existing researches are focused on vacuum pulse drying and vacuum freeze drying technologies, most of the adopted heat sources are infrared radiation plates, the infrared radiation penetrating capacity is weak, the temperature rise of materials is slow, and the energy consumption of a vacuum pump is huge after the vacuum pump is operated for a long time.
The hot air drying of the multilayer materials has serious non-uniformity, and the drying rate of the upper layer and the lower layer of the material tray is inconsistent. Only the surface of the material can be heated by convection, and the inside of the material is difficult to be directly heated. The temperature gradient and the moisture diffusion gradient of the material are opposite, so that the drying process is slow, and the drying time is prolonged.
Disclosure of Invention
The invention aims to provide vacuum radio frequency-hot air combined drying equipment to solve the problems of uneven heating caused by small loading capacity and corner effect of the existing radio frequency drying, high energy consumption, poor heating capacity of a heat source in vacuum drying, uneven hot air drying of multiple layers of materials, difficulty in heating the interior of the materials, slow drying and the like.
The invention also aims to provide a method for drying rhizome traditional Chinese medicinal materials by using the vacuum radio frequency-hot air combined drying equipment.
The purpose of the invention is realized by the following technical scheme:
multilayer vacuum radio frequency-hot air combined drying equipment for rhizome traditional Chinese medicinal materials comprises: the system comprises a circulating hot air drying system, a radio frequency heating system, a pulsating vacuum generation system and an automatic control system;
the circulating hot air drying system comprises a return air pipeline 9, a return air pipeline electromagnetic valve 11, a moisture removal electromagnetic valve 12, a centrifugal fan 13, an air inlet pipeline 14, an axial flow fan 15, a heating pipe 16, a pressure stabilizing cavity 17, an airflow distribution chamber 18 and an air inlet pipeline electromagnetic valve 19; wherein the content of the first and second substances,
the air inlet side of the air return pipeline 9 is communicated with the inside of the drying box body 47 through the side wall of the drying box body 47 of the radio frequency heating system, the air outlet side of the air return pipeline 9 is connected with the air inlet side of the air inlet pipeline 14, and an air return pipeline electromagnetic valve 11 is arranged between the air outlet side of the air return pipeline 9 and the air inlet side of the air inlet pipeline 14; the side wall of the air inlet pipeline 14 is provided with a moisture-removing electromagnetic valve 12, and the other side of the moisture-removing electromagnetic valve 12 is connected with a centrifugal fan 13; an axial flow fan 15 and a heating pipe 16 are sequentially and fixedly installed in the air inlet pipeline 14 from the air inlet side to the air outlet side, the air outlet side of the air inlet pipeline 14 is connected with an inlet of a pressure stabilizing cavity 17, an outlet of the pressure stabilizing cavity 17 is connected with an inlet of an airflow distribution chamber 18, an outlet of the airflow distribution chamber 18 is communicated with the inside of a drying box body 47 of a radio frequency heating system through an airflow distribution chamber pipeline, and an air inlet pipeline electromagnetic valve 19 is arranged on the airflow distribution chamber pipeline;
the automatic control system comprises a human-computer interaction interface 4;
the human-computer interaction interface 4 is communicated with a return air pipeline electromagnetic valve 11, a moisture exhaust electromagnetic valve 12, a centrifugal fan 13, an axial flow fan 15, a heating pipe 16, an air inlet pipeline electromagnetic valve 19, an outer anode electrode plate 21, an inner anode electrode plate 22, a stepping motor 23, an optical fiber temperature sensor 26, a weighing sensor 30, a relative humidity sensor 31, a pressure sensor 32, a drain valve 33, an air suction pipeline electromagnetic valve 35 and an air breaking electromagnetic valve 45 through power lines and signal lines;
the pulsating vacuum generation system comprises a drain valve 33, an air suction pipeline 34, an air suction pipeline electromagnetic valve 35, an air suction pipeline one-way valve 36, a water circulation type vacuum pump 37, a water inlet pipeline 38, a water discharge pipeline 39, a self-sucking pump 40, a filter screen 41, a cooling water circulation pipeline 43, a cooling device 44, an air breaking electromagnetic valve 45 and a water tank 46; wherein the content of the first and second substances,
the wall surface of the drying box body 47 of the radio frequency heating system is provided with an air outlet pipeline communicated with the interior of the drying box body 47, and the air outlet pipeline is provided with an air breaking electromagnetic valve 45;
the wall surface of a drying box body 47 of the radio frequency heating system is provided with an air suction pipeline 34 communicated with the inside of the drying box body 47, the air inlet end of the air suction pipeline 34 is communicated with the inside of the drying box body 47 through the wall surface of the drying box body 47 of the radio frequency heating system, the air outlet end of the air suction pipeline 34 is connected with an air suction opening of a water circulation type vacuum pump 37, and the air suction pipeline 34 is sequentially provided with an air suction pipeline electromagnetic valve 35 and an air suction pipeline one-way valve 36 from the air inlet end to the air outlet end; the water outlet of the water circulation type vacuum pump 37 is connected with a water tank 46 through a water discharge pipeline 39, and the water tank 46 is communicated with the water inlet of the water circulation type vacuum pump 37 through a water inlet pipeline 38; a filter screen 41 is arranged in the water tank 46, and a drain valve 33 is arranged at the bottom of the water tank; the water tank 46 is filled with water 42; a cooling water circulation pipeline 43 is arranged between the water tank 46 and the cooling device 44, and a self-sucking pump 40 is arranged on the cooling water circulation pipeline 43; water 42 enters a cooling device 44 through a cooling water circulation pipeline 43 under the driving of the self-priming pump 40;
the radio frequency heating system comprises a screw 20, an outer anode electrode plate 21, an inner anode electrode plate 22, a stepping motor 23, an outer grid electrode plate 24, an inner grid electrode plate 25, an optical fiber temperature sensor 26, a material 27, a material tray 28, a weighing bracket 29, a weighing sensor 30, a relative humidity sensor 31, a pressure sensor 32 and a drying box body 47; wherein the content of the first and second substances,
a plurality of layers of weighing brackets 29 are arranged inside a drying box body 47 of the radio frequency heating system, a material tray 28 is placed on each layer of weighing brackets 29, and materials 27 are placed on the material tray 28;
a plurality of layers of anode and grid electrode plates are arranged in a drying box body 47 of the radio frequency heating system, and each layer of anode and grid electrode plate is divided into an inner part and an outer part; each layer of anode electrode plate comprises an outer anode electrode plate 21 and an inner anode electrode plate 22, and each layer of grid electrode plate comprises an outer grid electrode plate 24 and an inner grid electrode plate 25;
the lead screw 20 is fixedly arranged on the drying box body 47, and the stepping motor 23 is in screw transmission on the lead screw 20; a plurality of stepping motors 23 are respectively arranged below each outer anode electrode plate 21 and each inner anode electrode plate 22, and below each outer grid electrode plate 24 and each inner grid electrode plate 25; a top plate is arranged above the stepping motor 23 and used for supporting the outer anode electrode plate 21, the inner anode electrode plate 22, the outer grid electrode plate 24 and the inner grid electrode plate 25;
the outer anode electrode plate 21 and the inner anode electrode plate 22 are connected and fixed at the same height by adopting an insulating material and are horizontally placed; the outer grid electrode plate 24 and the inner grid electrode plate 25 are connected and fixed below the outer anode electrode plate 21 and the inner anode electrode plate 22 by adopting an insulating material and are horizontally placed at a certain distance; the arrangement positions of the outer anode electrode plate 21 and the outer grid electrode plate 24 correspond, and the arrangement positions of the inner anode electrode plate 22 and the inner grid electrode plate 25 correspond;
an outer anode electrode plate 21 and an inner anode electrode plate 22 are arranged above the material 27, an outer grid electrode plate 24 and an inner grid electrode plate 25 are arranged below the material 27, and the material 27 is horizontally arranged at the vertical middle positions of the outer anode electrode plate 21, the inner anode electrode plate 22, the outer grid electrode plate 24 and the inner grid electrode plate 25;
the optical fiber temperature sensor 26 is positioned inside the drying box body 47 and is directly inserted into the material 27; the weighing bracket 29 is fixedly arranged on the weighing sensor 30; the relative humidity sensor 31 and the pressure sensor 32 are mounted on the side wall of the drying cabinet 47.
The automatic control system also comprises an emergency stop knob 1, a power indicator lamp 2, an alarm 3, a filament voltmeter 5, an anode voltmeter 6, an anode ammeter 7 and a grid ammeter 8; wherein, the emergency stop knob 1, the power indicator lamp 2, the alarm 3, the filament voltmeter 5, the anode voltmeter 6, the anode ammeter 7 and the grid ammeter 8 are connected in parallel through a lead.
The radio frequency heating system further comprises a drying cavity door 10, the drying cavity door 10 is fixed on the right wall surface of the drying box body 47 through a hinge, and the drying cavity door 10 is located right in front of the drying box body 47.
The weighing sensors 30 are four in number and are arranged at the four corners of the bottom of the weighing carriage 29.
The air return pipeline 9, the drying cavity door 10, the air inlet pipeline 14, the pressure stabilizing cavity 17, the airflow distribution chamber 18, the air suction pipeline 34, the water inlet pipeline 38, the water discharge pipeline 39, the cooling water circulation pipeline 43, the water tank 46 and the drying box body 47 are all made of 2mm 304 stainless steel, and the outer wall surface of the drying box body is covered with heat insulation materials.
The material tray 28 and the weighing bracket 29 are made of polytetrafluoroethylene materials with the thickness of 5mm, and small holes are uniformly distributed on the material tray 28.
A multi-layer vacuum radio frequency-hot air combined drying method utilizing the multi-layer vacuum radio frequency-hot air combined drying equipment for the rhizome traditional Chinese medicinal materials comprises the following steps:
1) the materials 27 are evenly spread in the material tray 28, and the material tray 28 is placed on the weighing bracket 29; before drying begins, a return air pipeline electromagnetic valve 11, a moisture exhaust electromagnetic valve 12, a centrifugal fan 13, an axial flow fan 15, a heating pipe 16, an air inlet pipeline electromagnetic valve 19, a drain valve 33, an air suction pipeline electromagnetic valve 35, a water circulation type vacuum pump 37, a self-sucking pump 40, a cooling device 44 and an air breaking electromagnetic valve 45 are all closed, water 42 is filled in a water tank 46, an optical fiber temperature sensor 26 is inserted into a material 27, and parameters such as a target temperature value and the like are manually set on a human-computer interaction interface 4;
2) starting the radio frequency heating system, continuously heating materials among the outer anode electrode plate 21, the inner anode electrode plate 22, the outer grid electrode plate 24 and the inner grid electrode plate 25 under the dielectric action, continuously monitoring the internal temperature of the materials 27 by the optical fiber temperature sensor 26, and displaying the internal temperature on the human-computer interaction interface 4 in real time; the filament voltmeter 5, the anode voltmeter 6, the anode ammeter 7 and the grid ammeter 8 also display the current voltage and current readings in real time; the automatic control system continuously collects the sensing information inside the drying box body 47;
when the change of the internal temperature of the material is monitored to be less than 5 ℃ within 1 minute, the stepping motor 23 moves to synchronously reduce the distances between the outer anode electrode plate 21 and the outer grid electrode plate 24 and between the inner anode electrode plate 22 and the inner grid electrode plate 25, so that the radiation intensity of an electromagnetic field is increased; when the internal temperature of the material 27 changes by more than 5 ℃ within 1 minute, the stepping motor 23 stops moving, and the polar plate distances between the outer anode electrode plate 21 and the outer grid electrode plate 24 and between the inner anode electrode plate 22 and the inner grid electrode plate 25 are kept unchanged, so that the radiation intensity of the current electromagnetic field is maintained; when the first temperature inside the material 27 in the area close to the outer anode electrode plate 21 and the outer grid electrode plate 24 in the material tray 28 is monitored to be higher than the second temperature inside the material 27 in the area close to the inner anode electrode plate 22 and the inner grid electrode plate 25, and the temperature difference is over 5 ℃, the outer anode electrode plate 21 is closed, the inner anode electrode plate 22 is kept opened, and therefore the second temperature inside the material 27 in the area close to the inner anode electrode plate 22 and the inner grid electrode plate 25 is increased; when the first temperature inside the material 27 in the area close to the outer anode electrode plate 21 and the outer grid electrode plate 24 in the material tray 28 is monitored to be higher than the second temperature inside the material 27 in the area close to the inner anode electrode plate 22 and the inner grid electrode plate 25, and the temperature difference is less than 5 ℃, the outer anode electrode plate 21 is restarted, and the inner anode electrode plate 22 is kept unchanged;
when the internal temperature of the material 27 is monitored to approach or reach the target temperature value set in the step 1, the outer anode electrode plate 21, the inner anode electrode plate 22, the outer grid electrode plate 24 and the inner grid electrode plate 25 are all closed, and the radio frequency heating is stopped;
3) the pulsating vacuum generation system is started to enter a vacuum state, the suction pipeline electromagnetic valve 35, the water circulation type vacuum pump 37, the self-priming pump 40 and the cooling device 44 are opened, the drain valve 33 and the air breaking electromagnetic valve 45 are kept closed and unchanged, and the pressure sensor 32 monitors the pressure change in the drying box body 47;
when the internal pressure of the drying box body 47 is close to 0.2kPa, the air suction pipeline electromagnetic valve 35 and the water circulation type vacuum pump 37 are closed, so that the internal pressure of the drying box body 47 is maintained above 0.2kPa under a vacuum condition, and the vacuum breakdown phenomenon is avoided; when the pressure rises to 1kPa, the air pumping pipeline electromagnetic valve 35 and the water circulation type vacuum pump 37 are opened again, and the pressure range of the vacuum state in the drying box body 47 is maintained to be 0.2-1 kPa;
when the weighing sensor 30 monitors that the change in the mass of the material 27 within 10s is less than 3g, and the change in the internal temperature of the material 27 within 10s is less than 5 ℃, the pulsating vacuum generation system is switched to a normal pressure state, namely, the suction pipeline electromagnetic valve 35, the water circulation type vacuum pump 37, the self-priming pump 40 and the cooling device 44 are closed, the emptying electromagnetic valve 45 and the drain valve 33 are opened, and sewage is cleaned regularly; the outside atmosphere enters the drying box body 47 along the air inlet pipeline through the air breaking electromagnetic valve 45, so that the pressure of the outside atmosphere reaches 101kPa and is kept for a period of time set manually, and then the outside atmosphere is switched to a vacuum state again;
4) repeating the step 2-3;
5) when the mass of the material 27 is close to half of the initial value, the radio frequency heating system and the pulsating vacuum generation system are closed, namely the outer anode electrode plate 21, the inner anode electrode plate 22, the outer grid electrode plate 24, the inner grid electrode plate 25, the suction pipeline electromagnetic valve 35, the water circulation type vacuum pump 37, the self-priming pump 40, the cooling device 44, the drain valve 33 and the air breaking electromagnetic valve 45 are all kept closed; starting a circulating hot air drying system, opening a return air pipeline electromagnetic valve 11, an axial flow fan 15, a heating pipe 16 and an air inlet pipeline electromagnetic valve 19, and keeping a moisture-removing electromagnetic valve 12 and a centrifugal fan 13 closed;
6) when the relative humidity sensor 31 monitors that the relative humidity in the drying box body 47 is higher than 20%, the moisture-removing electromagnetic valve 12 and the centrifugal fan 13 are opened; when the weight sensor 30 monitors that the mass of the material 27 is less than 0.5g within 10 minutes, the circulating hot air drying system stops working; when the optical fiber temperature sensor 26 monitors that the internal temperature of the material 27 is close to the room temperature, the circulating hot air drying system is started to work;
7) and (5) repeating the step 6 until the mass of the material 27 does not change more than 1g within 5 hours, and finishing the drying.
The invention has the beneficial effects that:
1. in the earlier stage of drying, the moisture content of the material 27 is high, the radio frequency heating system enables the material 27 to be rapidly heated up through the dielectric action, the heating rate of the material 27 is indirectly adjusted by adjusting the distance between the electrode plates through the stepping motor 23, and the temperature of the material 27 at the outer edge of the material tray 28 and the central area is ensured to be uniform through the separation work of the outer anode electrode plate 21, the inner anode electrode plate 22 and the outer grid electrode plate 24 and the inner grid electrode plate 25. When the optical fiber temperature sensor 26 detects that the internal temperature of the material 27 reaches a set value, the radio frequency heating system stops working, and energy consumption is effectively reduced.
2. The boiling point of water is reduced in the vacuum stage, the evaporated water of the material 27 can be rapidly removed, the pulse generation stage is favorable for breaking the partial pressure balance between the surface of the material 27 and the medium water vapor, the water evaporation on the surface of the material is favorable, the mass transfer power is increased, the operation time of the water circulation type vacuum pump 37 is shortened in the pulse working mode, and the energy consumption is effectively reduced.
3. The dry later stage, the material moisture content is low, and the dielectric heating effect of radio frequency heating reduces, and hot air drying can be wrapped up material 27 surface scouring through the convection current form, is favorable to material 27 surface each position to heat up evenly, and the intermittent heating mode is favorable to the inside moisture of material 27 to the surperficial migration of material 27, is favorable to moisture desorption and energy saving. According to the invention, the axial flow fan 15 is adopted to blow air through the heating pipe 16 and then enter the pressure stabilizing cavity 17, the flaring design is favorable for dynamic pressure balance to reduce the speed of the air flow center so as to enable the air flow center to be uniformly diffused, the air flow distribution chamber 18 adopts an inclined surface to solve the problem that the air speed is gradually reduced, the pressure stabilizing cavity 17 and the air flow distribution chamber 18 are matched to greatly improve the uniformity of the air flow, so that the materials 27 in different layers are uniformly heated, and the uniform drying is favorable.
4. The material tray 28 and the weighing material rack 29 are made of polytetrafluoroethylene materials with the thickness of 5mm, have the advantages of light weight, no influence of temperature, humidity and radiation, corrosion resistance, difficult deformation and the like, can be placed in a radio frequency electromagnetic field to contain the material 27, and avoid the condition that the sum of the weight of the weighing material rack made of metal materials and the mass of the material exceeds the maximum range of the weighing sensor 30.
5. The invention adopts a structure form of a multilayer material tray 28, thereby greatly improving the loading capacity.
6. The four weighing sensors 30 are uniformly arranged, the change of the material quality in the drying process is monitored by using a four-corner balance method, the four weighing sensors have the characteristics of stability and reliability, and the disturbance influence of airflow in a vacuum stage and a hot air drying stage on the weighing material rack 29, the material tray 28 and the material 27 is avoided.
7. The change conditions of the medium and the material 27 in the drying box body 47 are monitored by the sensor in the drying process, and analysis decision and execution are performed based on an automatic control system, and the whole set of equipment has the characteristics of high automation degree, low labor intensity and the like.
Drawings
Fig. 1 is a schematic front view of a multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials.
Fig. 2 is a schematic plan view of a multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials.
Fig. 3 is a schematic diagram of the multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials.
Fig. 4 is a position distribution diagram of the weighing bracket 29 and the weighing sensor 30 in the drying box body 47 of the multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials.
Fig. 5 is a shape structure and position distribution diagram of the outer anode electrode plate 21 and the inner anode electrode plate 22 of the multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials.
Fig. 6 is a schematic diagram of a radio frequency heating system of a multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials.
Fig. 7 is a schematic diagram of a circulating hot air drying system of a multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials.
Fig. 8 is a schematic diagram of the principle of the automatic control system of the multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials.
Fig. 9 is a schematic diagram of a pulse vacuum generating system of a multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials.
Fig. 10 is a partially enlarged schematic view of the anode, the grid electrode plate and the single-layer arrangement of the material of the multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials.
Fig. 11 is a schematic circuit basic composition diagram of a multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials.
Reference numerals:
1. emergency stop knob 2 and power indicator lamp
3. Alarm 4, human-computer interaction interface
5. Filament voltmeter 6 and anode voltmeter
7. Anode ammeter 8, grid ammeter
9. Air return pipeline 10 and drying cavity door
11. Electromagnetic valve 12 of air return pipeline and moisture-removing electromagnetic valve
13. Centrifugal fan 14, air inlet pipeline
15. Axial flow fan 16, heating pipe
17. Pressure stabilizing cavity 18 and airflow distribution chamber
19. Air inlet pipeline electromagnetic valve 20 and screw rod
21. Outer anode electrode plate 22 and inner anode electrode plate
23. Stepping motor 24, external grid electrode plate
25. Internal grid electrode plate 26 and optical fiber temperature sensor
27. Material 28, charging tray
29. Weighing bracket 30 and weighing sensor
31. Relative humidity sensor 32, pressure sensor
33. Drain valve 34, suction line
35. Air extraction line solenoid valve 36, air extraction line check valve
37. Water circulation type vacuum pump 38 and water inlet pipeline
39. Drain line 40, self priming pump
41. Filter screen 42, water
43. Cooling water circulation pipeline 44 and cooling device
45. Air breaking electromagnetic valve 46 and water tank
47. Drying box
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples.
A multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials comprises: the system comprises a circulating hot air drying system, a radio frequency heating system, a pulsating vacuum generation system and an automatic control system;
as shown in fig. 1 to 3 and 7, the circulating hot air drying system includes a return air pipeline 9, a return air pipeline electromagnetic valve 11, a moisture removal electromagnetic valve 12, a centrifugal fan 13, an air inlet pipeline 14, an axial flow fan 15, a heating pipe 16, a pressure stabilizing cavity 17, an air flow distribution chamber 18 and an air inlet pipeline electromagnetic valve 19; wherein the content of the first and second substances,
the air inlet side of the air return pipeline 9 is communicated with the inside of the drying box body 47 through the side wall of the drying box body 47 of the radio frequency heating system, the air outlet side of the air return pipeline 9 is connected with the air inlet side of the air inlet pipeline 14, and an air return pipeline electromagnetic valve 11 is arranged between the air outlet side of the air return pipeline 9 and the air inlet side of the air inlet pipeline 14. The side wall of the air inlet pipeline 14 is provided with a moisture-removing electromagnetic valve 12, and the other side of the moisture-removing electromagnetic valve 12 is connected with a centrifugal fan 13. An axial flow fan 15 and a heating pipe 16 are sequentially and fixedly installed in the air inlet pipeline 14 from the air inlet side to the air outlet side, the air outlet side of the air inlet pipeline 14 is connected with an inlet of a pressure stabilizing cavity 17, an outlet of the pressure stabilizing cavity 17 is connected with an inlet of an airflow distribution chamber 18, an outlet of the airflow distribution chamber 18 is communicated with the inside of a drying box body 47 of the radio frequency heating system through an airflow distribution chamber pipeline, and an air inlet pipeline electromagnetic valve 19 is arranged on the airflow distribution chamber pipeline.
As shown in fig. 8, the automatic control system comprises an emergency stop knob 1, a power indicator lamp 2, an alarm 3, a human-computer interaction interface 4, a filament voltmeter 5, an anode voltmeter 6, an anode ammeter 7 and a grid ammeter 8; wherein, the emergency stop knob 1, the power indicator lamp 2, the alarm 3, the filament voltmeter 5, the anode voltmeter 6, the anode ammeter 7 and the grid ammeter 8 are connected in parallel through a lead.
The human-computer interaction interface 4 is communicated with a return air pipeline electromagnetic valve 11, a moisture exhaust electromagnetic valve 12, a centrifugal fan 13, an axial flow fan 15, a heating pipe 16, an air inlet pipeline electromagnetic valve 19, an outer anode electrode plate 21, an inner anode electrode plate 22, a stepping motor 23, an optical fiber temperature sensor 26, a weighing sensor 30, a relative humidity sensor 31, a pressure sensor 32, a drain valve 33, an air suction pipeline electromagnetic valve 35 and an air breaking electromagnetic valve 45 through power lines and signal lines.
As shown in fig. 3 and 9, the pulsating vacuum generation system includes a drain valve 33, a suction line 34, a suction line solenoid valve 35, a suction line check valve 36, a water circulation type vacuum pump 37, a water inlet line 38, a drain line 39, a self-priming pump 40, a filter screen 41, a cooling water circulation line 43, a cooling device 44, a vacuum breaking solenoid valve 45, and a water tank 46; wherein the content of the first and second substances,
and an air outlet pipeline communicated with the interior of the drying box body 47 is arranged on the wall surface of the drying box body 47 of the radio frequency heating system, and an air breaking electromagnetic valve 45 is arranged on the air outlet pipeline. When the interior of the drying box body 47 needs to be kept in vacuum, the vacuum breaking electromagnetic valve 45 is closed; when the air breaking electromagnetic valve 45 is opened, outside air can enter the drying box body 47 to break a vacuum state.
The wall surface of the drying box body 47 of the radio frequency heating system is provided with an air suction pipeline 34 communicated with the inside of the drying box body 47, the air inlet end of the air suction pipeline 34 is communicated with the inside of the drying box body 47 through the wall surface of the drying box body 47 of the radio frequency heating system, the air outlet end of the air suction pipeline 34 is connected with the air suction port of the water circulation type vacuum pump 37, and the air suction pipeline 34 is sequentially provided with an air suction pipeline electromagnetic valve 35 and an air suction pipeline one-way valve 36 from the air inlet end to the air outlet end. The water outlet of the water circulation type vacuum pump 37 is connected to a water tank 46 through a water discharge line 39, and the water tank 46 is communicated with the water inlet of the water circulation type vacuum pump 37 through a water inlet line 38. The water tank 46 is provided with a filter screen 41 inside and a drain valve 33 at the bottom. The water tank 46 is filled with water 42. A cooling water circulation pipeline 43 is arranged between the water tank 46 and the cooling device 44, and a self-priming pump 40 is arranged on the cooling water circulation pipeline 43. Water 42 enters a cooling device 44 driven by a self-priming pump 40 through a cooling water circulation line 43.
As shown in fig. 3, 4, 5 and 6, the rf heating system includes a drying chamber door 10, a lead screw 20, an outer anode electrode plate 21, an inner anode electrode plate 22, a stepping motor 23, an outer grid electrode plate 24, an inner grid electrode plate 25, an optical fiber temperature sensor 26, a material 27, a tray 28, a weighing bracket 29, a weighing sensor 30, a relative humidity sensor 31, a pressure sensor 32 and a drying box 47; wherein the content of the first and second substances,
the drying chamber door 10 is fixed on the right wall surface of the drying box body 47 through a hinge and a hinge, and the drying chamber door 10 is positioned right in front of the drying box body 47.
A plurality of layers of weighing brackets 29 are arranged inside a drying box body 47 of the radio frequency heating system, a material tray 28 is placed on each layer of weighing brackets 29, and materials 27 are placed on the material tray 28.
The drying box body 47 of the radio frequency heating system is internally provided with a plurality of layers of anode and grid electrode plates, and each layer of anode and grid electrode plate is divided into an inner part and an outer part. Each layer of anode electrode plate comprises an outer anode electrode plate 21 and an inner anode electrode plate 22, and each layer of grid electrode plate comprises an outer grid electrode plate 24 and an inner grid electrode plate 25.
As shown in fig. 11, a 380V ac power supply is connected to the power amplifier module and the resonance module, the resonance module is connected to each layer of anode electrode plates, and ac power generates a 27MHz high frequency electromagnetic field between each anode and the gate electrode plate through resonance, coupling, and excitation.
The lead screw 20 is fixedly arranged on the drying box body 47, and the stepping motor 23 is in screw transmission on the lead screw 20. A plurality of stepping motors 23 are respectively arranged below each outer anode electrode plate 21 and each inner anode electrode plate 22, and below each outer grid electrode plate 24 and each inner grid electrode plate 25. A top plate is provided above the stepping motor 23 for supporting the outer and inner anode electrode plates 21 and 22 and the outer and inner grid electrode plates 24 and 25.
The outer anode electrode plate 21 and the inner anode electrode plate 22 are connected and fixed at the same height by adopting an insulating material and are horizontally placed; the outer grid electrode plate 24 and the inner grid electrode plate 25 are connected and fixed by insulating materials to be horizontally placed at a certain distance below the outer anode electrode plate 21 and the inner anode electrode plate 22. The outer anode electrode plate 21 and the outer gate electrode plate 24 correspond in arrangement position, and the inner anode electrode plate 22 and the inner gate electrode plate 25 correspond in arrangement position.
An outer anode electrode plate 21 and an inner anode electrode plate 22 are arranged above the material 27, an outer grid electrode plate 24 and an inner grid electrode plate 25 are arranged below the material 27, and the material 27 is horizontally arranged at the vertical middle positions of the outer anode electrode plate 21, the inner anode electrode plate 22, the outer grid electrode plate 24 and the inner grid electrode plate 25.
The distance between the anode and the grid electrode plate can be adjusted by controlling the movement of the stepping motor 23. The distance between the polar plates is changed to adjust the radiation intensity of the electromagnetic field, and the temperature of the material is indirectly influenced. Because the material temperature can not be too high, the distance between the polar plates needs to be adjusted according to the material temperature.
The fiber optic temperature sensor 26 is located inside the drying cabinet 47 and can be directly inserted inside the material 27. The weighing bracket 29 is fixedly mounted on the weighing cell 30. Preferably, the weighing sensors 30 are four in number, as shown in fig. 4, and are arranged at the four corners of the bottom of the weighing bracket 29. The relative humidity sensor 31 and the pressure sensor 32 are mounted on the side wall of the drying cabinet 47.
The air return pipeline 9, the drying cavity door 10, the air inlet pipeline 14, the pressure stabilizing cavity 17, the airflow distribution chamber 18, the air suction pipeline 34, the water inlet pipeline 38, the water discharge pipeline 39, the cooling water circulation pipeline 43, the water tank 46 and the drying box body 47 are all made of 2mm 304 stainless steel, and the outer wall surface of the drying box body is covered with heat insulation materials.
Wherein, the charging tray 28 and the weighing support 29 are made of 5 mm-thick polytetrafluoroethylene materials, and small holes are uniformly distributed on the charging tray 28.
The temperature range of the automatic control system is 0-150 ℃, the temperature control precision is +/-1.5 ℃, the humidity monitoring range is 0-100% RH, the error is +/-55 RH, the vacuum degree range is 0-100 kPa, the error is +/-1 kPa, the weighing range is 0-3 kg, the precision is +/-0.1 g, the high-frequency oscillation power is 3kW, and the high-frequency rated frequency is 27.12 MHz.
A multi-layer vacuum radio frequency-hot air combined drying method for rhizome traditional Chinese medicinal materials comprises the following steps:
1. the materials 27 are evenly spread in the material tray 28, and the material tray 28 is placed on the weighing bracket 29; before drying begins, the air return pipeline electromagnetic valve 11, the moisture exhaust electromagnetic valve 12, the centrifugal fan 13, the axial flow fan 15, the heating pipe 16, the air inlet pipeline electromagnetic valve 19, the drain valve 33, the air suction pipeline electromagnetic valve 35, the water circulation type vacuum pump 37, the self-sucking pump 40, the cooling device 44 and the air breaking electromagnetic valve 45 are all closed, the water tank 46 is filled with water 42, the optical fiber temperature sensor 26 is inserted into the material 27, and parameters such as a target temperature value and the like are manually set on the human-computer interaction interface 4.
2. When the radio frequency heating system is started, the materials between the outer anode electrode plate 21 and the inner anode electrode plate 22 and the materials between the outer grid electrode plate 24 and the inner grid electrode plate 25 are heated continuously under the dielectric action, and the optical fiber temperature sensor 26 continuously monitors the internal temperature of the materials 27 and displays the internal temperature on the human-computer interaction interface 4 in real time. The filament voltmeter 5, the anode voltmeter 6, the anode ammeter 7 and the grid ammeter 8 also display the current voltage and current readings in real time. The automatic control system continuously collects the sensing information inside the drying cabinet 47.
When the change of the internal temperature of the material is monitored to be less than 5 ℃ within 1 minute, the stepping motor 23 moves to synchronously reduce the distances between the outer anode electrode plate 21 and the outer grid electrode plate 24 and between the inner anode electrode plate 22 and the inner grid electrode plate 25, so that the radiation intensity of an electromagnetic field is increased; when the internal temperature of the material 27 changes by more than 5 ℃ within 1 minute, the stepping motor 23 stops moving, and the plate distances between the outer anode electrode plate 21 and the outer grid electrode plate 24 and between the inner anode electrode plate 22 and the inner grid electrode plate 25 are kept unchanged, so that the radiation intensity of the current electromagnetic field is maintained. When it is monitored that a first temperature inside the material 27 in the area of the tray 28 close to the outer anode electrode plate 21 and the outer grid electrode plate 24 is higher than a second temperature inside the material 27 in the area close to the inner anode electrode plate 22 and the inner grid electrode plate 25, and the temperature difference exceeds 5 ℃, the outer anode electrode plate 21 is closed, the inner anode electrode plate 22 is kept open, and therefore the second temperature inside the material 27 in the area close to the inner anode electrode plate 22 and the inner grid electrode plate 25 is increased. When the first temperature inside the material 27 in the area close to the outer anode electrode plate 21 and the outer grid electrode plate 24 in the tray 28 is monitored to be higher than the second temperature inside the material 27 in the area close to the inner anode electrode plate 22 and the inner grid electrode plate 25, and the temperature difference is less than 5 ℃, the outer anode electrode plate 21 is turned on again, and the inner anode electrode plate 22 is kept on.
When the internal temperature of the material 27 is monitored to approach or reach the target temperature value set in the step 1, the outer anode electrode plate 21, the inner anode electrode plate 22, the outer grid electrode plate 24 and the inner grid electrode plate 25 are all closed, and the radio frequency heating is stopped.
The radio frequency drying technology utilizes the polar motion of water molecules under the action of a high-frequency electric field to cause severe collision in a dried object, so that the water molecules are evaporated from the inside, the drying rate is increased, the swelling effect can be realized on blocky materials, and good effects of improving elasticity, chewiness and the like are realized.
3. The pulsating vacuum generation system is started to enter a vacuum state, the suction pipeline electromagnetic valve 35, the water circulation type vacuum pump 37, the self-priming pump 40 and the cooling device 44 are opened, the drain valve 33 and the air breaking electromagnetic valve 45 are kept closed and unchanged, and the pressure sensor 32 monitors the pressure change in the drying box body 47.
When the internal pressure of the drying box body 47 is close to 0.2kPa, the air suction pipeline electromagnetic valve 35 and the water circulation type vacuum pump 37 are closed, so that the internal pressure of the drying box body 47 is maintained above 0.2kPa under a vacuum condition, and the vacuum breakdown phenomenon is avoided; when the pressure rises to 1kPa again, the air pumping pipeline electromagnetic valve 35 and the water circulation type vacuum pump 37 are opened again, and the pressure range of the vacuum state in the drying box body 47 is maintained to be 0.2-1 kPa.
When the weighing sensor 30 monitors that the change in the mass of the material 27 within 10s is less than 3g, and the change in the internal temperature of the material 27 within 10s is less than 5 ℃, the pulsating vacuum generation system is switched to a normal pressure state, namely, the suction pipeline electromagnetic valve 35, the water circulation type vacuum pump 37, the self-priming pump 40 and the cooling device 44 are closed, the emptying electromagnetic valve 45 and the drain valve 33 are opened, and sewage is cleaned regularly. The outside atmosphere enters the drying box body 47 through the air breaking electromagnetic valve 45 along the air inlet pipeline, the pressure of the outside atmosphere reaches 101kPa and is kept for a period of time set manually, and then the drying box body is switched to the vacuum state again.
4. Repeating the step 2-3;
5. when the mass of the material 27 is close to half of the initial value, the radio frequency heating system and the pulsating vacuum generation system are closed, that is, the outer anode electrode plate 21, the inner anode electrode plate 22, the outer grid electrode plate 24, the inner grid electrode plate 25, the suction pipeline electromagnetic valve 35, the water circulation type vacuum pump 37, the self-priming pump 40, the cooling device 44, the drain valve 33 and the air breaking electromagnetic valve 45 are all kept closed. And starting the circulating hot air drying system, opening the air return pipeline electromagnetic valve 11, the axial flow fan 15, the heating pipe 16 and the air inlet pipeline electromagnetic valve 19, and keeping the moisture-removing electromagnetic valve 12 and the centrifugal fan 13 closed.
6. When the relative humidity sensor 31 monitors that the relative humidity in the drying box body 47 is higher than 20%, the moisture-removing electromagnetic valve 12 and the centrifugal fan 13 are opened; when the weight sensor 30 monitors that the mass of the material 27 is less than 0.5g within 10 minutes, the circulating hot air drying system stops working; when the optical fiber temperature sensor 26 detects that the internal temperature of the material 27 is close to the room temperature, the circulating hot air drying system is started to work.
7. And (5) repeating the step 6 until the mass of the material 27 does not change more than 1g within 5 hours, and finishing the drying.
The multi-layer vacuum radio frequency-hot air combined drying method and the multi-layer vacuum radio frequency-hot air combined drying equipment for the rhizome traditional Chinese medicinal materials can be suitable for drying and processing the traditional Chinese medicinal materials with larger volume such as the gastrodia elata, the pseudo-ginseng and the salvia miltiorrhiza.

Claims (7)

1. Multilayer vacuum radio frequency-hot air combined drying equipment for rhizome traditional Chinese medicinal materials is characterized in that: it includes: the system comprises a circulating hot air drying system, a radio frequency heating system, a pulsating vacuum generation system and an automatic control system;
the circulating hot air drying system comprises a return air pipeline (9), a return air pipeline electromagnetic valve (11), a moisture-removing electromagnetic valve (12), a centrifugal fan (13), an air inlet pipeline (14), an axial flow fan (15), a heating pipe (16), a pressure stabilizing cavity (17), an air flow distribution chamber (18) and an air inlet pipeline electromagnetic valve (19); wherein the content of the first and second substances,
the air inlet side of the air return pipeline (9) is communicated with the inside of the drying box body (47) through the side wall of the drying box body (47) of the radio frequency heating system, the air outlet side of the air return pipeline (9) is connected with the air inlet side of the air inlet pipeline (14), and an air return pipeline electromagnetic valve (11) is arranged between the air outlet side of the air return pipeline (9) and the air inlet side of the air inlet pipeline (14); a moisture-removing electromagnetic valve (12) is arranged on the side wall of the air inlet pipeline (14), and the other side of the moisture-removing electromagnetic valve (12) is connected with a centrifugal fan (13); an axial flow fan (15) and a heating pipe (16) are sequentially and fixedly installed in the air inlet pipeline (14) from the air inlet side to the air outlet side, the air outlet side of the air inlet pipeline (14) is connected with an inlet of a pressure stabilizing cavity (17), an outlet of the pressure stabilizing cavity (17) is connected with an inlet of an airflow distribution chamber (18), an outlet of the airflow distribution chamber (18) is communicated with the inside of a drying box body (47) of a radio frequency heating system through an airflow distribution chamber pipeline, and an air inlet pipeline electromagnetic valve (19) is arranged on the airflow distribution chamber pipeline;
the automatic control system comprises a human-computer interaction interface (4);
the human-computer interaction interface (4) is communicated with the air return pipeline electromagnetic valve (11), the moisture discharging electromagnetic valve (12), the centrifugal fan (13), the axial flow fan (15), the heating pipe (16), the air inlet pipeline electromagnetic valve (19), the outer anode electrode plate (21), the inner anode electrode plate (22), the stepping motor (23), the optical fiber temperature sensor (26), the weighing sensor (30), the relative humidity sensor (31), the pressure sensor (32), the drain valve (33), the air suction pipeline electromagnetic valve (35) and the air breaking electromagnetic valve (45) through power lines and signal lines;
the pulsating vacuum generation system comprises a drain valve (33), an air pumping pipeline (34), an air pumping pipeline electromagnetic valve (35), an air pumping pipeline one-way valve (36), a water circulation type vacuum pump (37), a water inlet pipeline (38), a water drainage pipeline (39), a self-sucking pump (40), a filter screen (41), a cooling water circulation pipeline (43), a cooling device (44), an air breaking electromagnetic valve (45) and a water tank (46); wherein the content of the first and second substances,
the wall surface of a drying box body (47) of the radio frequency heating system is provided with an air outlet pipeline communicated with the interior of the drying box body (47), and the air outlet pipeline is provided with an air breaking electromagnetic valve (45);
an air suction pipeline (34) communicated with the inside of the drying box body (47) is arranged on the wall surface of the drying box body (47) of the radio frequency heating system, an air inlet end of the air suction pipeline (34) is communicated with the inside of the drying box body (47) through the wall surface of the drying box body (47) of the radio frequency heating system, an air outlet end of the air suction pipeline (34) is connected with an air suction opening of the water circulation type vacuum pump (37), and an air suction pipeline electromagnetic valve (35) and an air suction pipeline one-way valve (36) are sequentially arranged on the air suction pipeline (34) from the air inlet end to the air outlet; a water outlet of the water circulation type vacuum pump (37) is connected with a water tank (46) through a water discharge pipeline (39), and the water tank (46) is communicated with a water inlet of the water circulation type vacuum pump (37) through a water inlet pipeline (38); a filter screen (41) is arranged in the water tank (46), and a drain valve (33) is arranged at the bottom of the water tank; the water tank (46) is filled with water (42); a cooling water circulation pipeline (43) is arranged between the water tank (46) and the cooling device (44), and a self-sucking pump (40) is arranged on the cooling water circulation pipeline (43); water (42) enters a cooling device (44) through a cooling water circulation pipeline (43) under the driving of a self-sucking pump (40);
the radio frequency heating system comprises a screw rod (20), an outer anode electrode plate (21), an inner anode electrode plate (22), a stepping motor (23), an outer grid electrode plate (24), an inner grid electrode plate (25), an optical fiber temperature sensor (26), a material (27), a material tray (28), a weighing bracket (29), a weighing sensor (30), a relative humidity sensor (31), a pressure sensor (32) and a drying box body (47); wherein the content of the first and second substances,
a plurality of layers of weighing supports (29) are arranged inside a drying box body (47) of the radio frequency heating system, a material tray (28) is placed on each layer of weighing supports (29), and materials (27) are placed on the material tray (28);
a plurality of layers of anode and grid electrode plates are arranged in a drying box body (47) of the radio frequency heating system, and each layer of anode and grid electrode plate is divided into an inner part and an outer part; each layer of anode electrode plate comprises an outer anode electrode plate (21) and an inner anode electrode plate (22), and each layer of grid electrode plate comprises an outer grid electrode plate (24) and an inner grid electrode plate (25);
the screw rod (20) is fixedly arranged on the drying box body (47), and the stepping motor (23) is in screw transmission on the screw rod (20); a plurality of stepping motors (23) are respectively arranged below each outer anode electrode plate (21) and each inner anode electrode plate (22) and below each outer grid electrode plate (24) and each inner grid electrode plate (25); a top plate is arranged above the stepping motor (23) and is used for supporting the outer anode electrode plate (21), the inner anode electrode plate (22), the outer grid electrode plate (24) and the inner grid electrode plate (25);
the outer anode electrode plate (21) and the inner anode electrode plate (22) are connected and fixed at the same height by adopting an insulating material and are horizontally placed; the outer grid electrode plate (24) and the inner grid electrode plate (25) are fixedly connected to the lower parts of the outer anode electrode plate (21) and the inner anode electrode plate (22) by adopting insulating materials and are horizontally placed at a certain distance; the arrangement positions of the outer anode electrode plate (21) and the outer grid electrode plate (24) correspond to each other, and the arrangement positions of the inner anode electrode plate (22) and the inner grid electrode plate (25) correspond to each other;
an outer anode electrode plate (21) and an inner anode electrode plate (22) are arranged above the material (27), an outer grid electrode plate (24) and an inner grid electrode plate (25) are arranged below the material (27), and the material (27) is horizontally arranged at the vertical middle positions of the outer anode electrode plate (21), the inner anode electrode plate (22), the outer grid electrode plate (24) and the inner grid electrode plate (25);
the optical fiber temperature sensor (26) is positioned inside the drying box body (47) and is directly inserted into the material (27); the weighing bracket (29) is fixedly arranged on the weighing sensor (30); a relative humidity sensor (31) and a pressure sensor (32) are arranged on the side wall of the drying box body (47).
2. The multi-layer vacuum radio-frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials as claimed in claim 1, wherein: the automatic control system also comprises an emergency stop knob (1), a power indicator lamp (2), an alarm (3), a filament voltmeter (5), an anode voltmeter (6), an anode ammeter (7) and a grid ammeter (8); the emergency stop device comprises an emergency stop knob (1), a power indicator lamp (2), an alarm (3), a filament voltmeter (5), an anode voltmeter (6), an anode ammeter (7) and a grid ammeter (8) which are connected in parallel through wires.
3. The multi-layer vacuum radio-frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials as claimed in claim 1, wherein: the radio frequency heating system further comprises a drying cavity door (10), the drying cavity door (10) is fixed on the right wall surface of the drying box body (47) through a hinge and a hinge, and the drying cavity door (10) is located right in front of the drying box body (47).
4. The multi-layer vacuum radio-frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials as claimed in claim 1, wherein: the four weighing sensors (30) are arranged at four corners of the bottom of the weighing bracket (29).
5. The multi-layer vacuum radio frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials as claimed in claim 3, wherein: the air return pipeline (9), the drying cavity door (10), the air inlet pipeline (14), the pressure stabilizing cavity (17), the airflow distribution chamber (18), the air suction pipeline (34), the water inlet pipeline (38), the water discharge pipeline (39), the cooling water circulation pipeline (43), the water tank (46) and the drying box body (47) are all made of 2mm 304 stainless steel, and the outer wall surface of the air return pipeline is covered with heat insulation materials.
6. The multi-layer vacuum radio-frequency-hot air combined drying device for rhizome traditional Chinese medicinal materials as claimed in claim 1, wherein: the material tray (28) and the weighing bracket (29) are made of polytetrafluoroethylene materials with the thickness of 5mm, and small holes are uniformly distributed on the material tray (28).
7. A multi-layer vacuum radio frequency-hot air combined drying method using multi-layer vacuum radio frequency-hot air combined drying equipment for rhizome traditional Chinese medicinal materials according to any one of claims 1 to 6, wherein the multi-layer vacuum radio frequency-hot air combined drying method comprises the following steps: the method comprises the following steps:
1) the materials (27) are evenly spread in the material tray (28), and the material tray (28) is placed on the weighing bracket (29); before drying begins, a return air pipeline electromagnetic valve (11), a moisture exhaust electromagnetic valve (12), a centrifugal fan (13), an axial flow fan (15), a heating pipe (16), an air inlet pipeline electromagnetic valve (19), a drain valve (33), an air suction pipeline electromagnetic valve (35), a water circulation type vacuum pump (37), a self-sucking pump (40), a cooling device (44) and an emptying electromagnetic valve (45) are all closed, a water tank (46) is filled with water (42), an optical fiber temperature sensor (26) is inserted into a material (27), and parameters such as a target temperature value are manually set on a human-computer interaction interface (4);
2) starting a radio frequency heating system, continuously heating materials among an outer anode electrode plate (21), an inner anode electrode plate (22), an outer grid electrode plate (24) and an inner grid electrode plate (25) under the dielectric action, continuously monitoring the internal temperature of the materials (27) by an optical fiber temperature sensor (26), and displaying the internal temperature on a human-computer interaction interface (4) in real time; the filament voltmeter (5), the anode voltmeter (6), the anode ammeter (7) and the grid ammeter (8) also display the current voltage and current readings in real time; the automatic control system continuously collects sensing information inside the drying box body (47);
when the change of the internal temperature of the material is monitored to be less than 5 ℃ within 1 minute, the stepping motor (23) moves to synchronously reduce the distance between the outer anode electrode plate (21) and the outer grid electrode plate (24) and the distance between the inner anode electrode plate (22) and the inner grid electrode plate (25), so that the radiation intensity of an electromagnetic field is increased; when the internal temperature of the material (27) changes by more than 5 ℃ within 1 minute, the stepping motor (23) stops moving, and the plate distances between the outer anode electrode plate (21) and the outer grid electrode plate (24) and between the inner anode electrode plate (22) and the inner grid electrode plate (25) are kept unchanged, so that the radiation intensity of the current electromagnetic field is maintained; when a first temperature inside the material (27) in the material tray (28) close to the outer anode electrode plate (21) and the outer grid electrode plate (24) is higher than a second temperature inside the material (27) close to the inner anode electrode plate (22) and the inner grid electrode plate (25) and the temperature difference exceeds 5 ℃, the outer anode electrode plate (21) is closed, the inner anode electrode plate (22) is kept open, and therefore the second temperature inside the material (27) close to the inner anode electrode plate (22) and the inner grid electrode plate (25) is increased; when a first temperature inside the material (27) in the material tray (28) close to the outer anode electrode plate (21) and the outer grid electrode plate (24) is higher than a second temperature inside the material (27) close to the inner anode electrode plate (22) and the inner grid electrode plate (25) and the temperature difference is less than 5 ℃, the outer anode electrode plate (21) is turned on again, and the inner anode electrode plate (22) is kept on;
when the internal temperature of the material (27) is monitored to be close to or reach the target temperature value set in the step 1, the outer anode electrode plate (21), the inner anode electrode plate (22), the outer grid electrode plate (24) and the inner grid electrode plate (25) are all closed, and the radio frequency heating is stopped;
3) the pulsating vacuum generation system is started to enter a vacuum state, an air suction pipeline electromagnetic valve (35), a water circulation type vacuum pump (37), a self-priming pump (40) and a cooling device (44) are started, a drain valve (33) and an air breaking electromagnetic valve (45) are kept closed and unchanged, and a pressure sensor (32) monitors the pressure change in a drying box body (47);
when the internal pressure of the drying box body (47) is monitored to be close to 0.2kPa, the air suction pipeline electromagnetic valve (35) and the water circulation type vacuum pump (37) are closed, so that the internal pressure of the drying box body (47) is maintained to be above 0.2kPa under a vacuum condition, and the vacuum breakdown phenomenon is avoided; when the pressure rises to 1kPa, the air pumping pipeline electromagnetic valve (35) and the water circulation type vacuum pump (37) are opened again, and the pressure range of the vacuum state in the drying box body (47) is maintained to be 0.2-1 kPa;
when the weighing sensor (30) monitors that the change of the mass of the material (27) within 10s is less than 3g, and the change of the internal temperature of the material (27) within 10s is less than 5 ℃, the pulsating vacuum generation system is switched to a normal pressure state, namely an air suction pipeline electromagnetic valve (35), a water circulation type vacuum pump (37), a self-sucking pump (40) and a cooling device (44) are closed, an air breaking electromagnetic valve (45) and a drain valve (33) are opened, and sewage is cleaned regularly; the outside atmosphere enters a drying box body (47) along an air inlet pipeline through an air breaking electromagnetic valve (45), so that the pressure of the outside atmosphere reaches 101kPa and is kept for a period of time set manually, and then the outside atmosphere is switched to a vacuum state again;
4) repeating the step 2-3;
5) when the mass of the material (27) is close to half of the initial value, the radio frequency heating system and the pulsating vacuum generation system are closed, namely the outer anode electrode plate (21), the inner anode electrode plate (22), the outer grid electrode plate (24), the inner grid electrode plate (25), the suction pipeline electromagnetic valve (35), the water circulation type vacuum pump (37), the self-priming pump (40), the cooling device (44), the drain valve (33) and the vacuum breaking electromagnetic valve (45) are kept closed; starting a circulating hot air drying system, opening a return air pipeline electromagnetic valve (11), an axial flow fan (15), a heating pipe (16) and an air inlet pipeline electromagnetic valve (19), and keeping a moisture-removing electromagnetic valve (12) and a centrifugal fan (13) closed;
6) when the relative humidity sensor (31) monitors that the relative humidity in the drying box body (47) is higher than 20%, the dehumidifying electromagnetic valve (12) and the centrifugal fan (13) are opened; when the weight sensor (30) monitors that the mass of the material (27) is less than 0.5g within 10 minutes, the circulating hot air drying system stops working; when the optical fiber temperature sensor (26) monitors that the internal temperature of the material (27) is close to room temperature, the circulating hot air drying system is started to work;
7) and (5) repeating the step (6) until the mass of the material (27) does not change more than 1g within 5 hours, and finishing the drying.
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Cited By (8)

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CN111972488A (en) * 2020-07-19 2020-11-24 北京工商大学 Combined drying method of blackcurrants
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Publication number Priority date Publication date Assignee Title
CN111937953A (en) * 2020-07-19 2020-11-17 北京工商大学 Combined drying method of mulberries
CN111972488A (en) * 2020-07-19 2020-11-24 北京工商大学 Combined drying method of blackcurrants
CN112617267A (en) * 2020-12-21 2021-04-09 中国农业大学 Method and equipment for removing local moisture of case-packed tobacco flakes
CN112617267B (en) * 2020-12-21 2022-03-08 中国农业大学 Method and equipment for removing local moisture of case-packed tobacco flakes
CN113280581A (en) * 2021-05-31 2021-08-20 蚌埠学院 Vacuum microwave low-temperature dehydration equipment for meat
CN113280581B (en) * 2021-05-31 2022-01-25 蚌埠学院 Vacuum microwave low-temperature dehydration equipment for meat
CN113670015A (en) * 2021-07-23 2021-11-19 新疆农业科学院农业机械化研究所 Hot air drying system and use method thereof
WO2023096476A1 (en) * 2021-11-29 2023-06-01 Université Ibn Zohr Hybrid solar dryer with integrated anti-covid-19 disinfection
CN114223929A (en) * 2021-12-14 2022-03-25 中国农业大学 Combined parallel polar plate type box-packed tobacco slice dehydration device and dehydration method
CN114223929B (en) * 2021-12-14 2023-02-24 中国农业大学 Combined parallel polar plate type box-packed tobacco slice dehydration device and dehydration method
CN115349598A (en) * 2022-07-13 2022-11-18 西北农林科技大学 Preparation method of hot air assisted radio frequency variable temperature differential pressure puffed composite puffed snack
CN115349598B (en) * 2022-07-13 2024-03-22 西北农林科技大学 Preparation method of hot air-assisted radio frequency variable temperature differential pressure puffing composite puffed snack

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