Drying device and method for reducing loss of active ingredients of American ginseng

Abstract

The invention discloses a drying device and method for reducing the loss of active ingredients of American ginseng, and relates to the technical field of drying equipment, the drying device comprises a drying box body, the drying box body is provided with a tray support and an air supply flow equalizing cavity, and the tray support is provided with a tray and a porous flow equalizing plate; the flow guide cover plate is positioned at the upper part in the drying box body; the air supply unit is provided with a centrifugal fan and a circulating air pipeline; the heat pump unit is provided with a heat release side and a heat absorption side; and the atomizing unit is provided with a water storage tank and an atomizer. The drying uniformity is improved, local overheating or insufficient drying is effectively prevented, the problem that the upper layer and the lower layer are dried unevenly due to improper airflow distribution of traditional equipment is solved, active ingredient degradation caused by too high local temperature is avoided, the relative humidity of the drying environment is accurately controlled through atomization humidification in the speed reduction drying period, and the drying efficiency is improved. Hardening and crusting of the surface of the American ginseng due to too fast water loss are prevented, mild drying at a relatively low temperature is realized, and components such as heat-sensitive ginsenoside are protected.

Description

Technical Field

[0001] The present invention relates to the technical field of drying devices, in particular to a drying device and a method for reducing the loss of active ingredients of American ginseng. Background Art

[0002] American ginseng is a valuable medicinal plant. Its main bioactive components, such as ginsenosides and polysaccharides, are extremely sensitive to temperature, humidity, and oxidation conditions. Drying, a key step in the ginseng processing process, directly determines the quality, active ingredient content, and economic value of the final product.

[0003] At present, large-scale drying of American ginseng mainly adopts hot air circulation drying technology, which usually includes an insulated box, a heating unit, a fan circulation system and a multi-layer material rack. Its basic working principle is to use a fan to drive hot air to circulate in the box, flowing through the American ginseng laid on a tray or mesh disk, and removing moisture through convection heat exchange to achieve drying. However, due to the natural rising effect of hot air, there is a significant vertical temperature gradient in the insulated box, and the drying rates of the upper and lower layers of materials are inconsistent. The upper or lower layer dries slowly due to insufficient heated air volume, or the surface hardens and crusts due to excessive drying. This hardened layer will hinder the escape of internal moisture. In order to achieve the target moisture content, it is often necessary to extend the drying time or increase the temperature, thereby exacerbating the damage to heat-sensitive active ingredients. Therefore, this type of drying device has poor drying uniformity and is prone to local degradation of active ingredients.

[0004] In traditional hot air drying, water vapor, rich in volatile flavor compounds and active ingredients in American ginseng, is typically discharged directly as exhaust gas. This not only wastes energy but also directly depletes active ingredients, failing to maximize the value of the medicinal material. Furthermore, existing drying methods often use fixed temperature and time settings, making it impossible to dynamically adjust temperature and humidity parameters based on the moisture characteristics of American ginseng at different drying stages. Especially during the critical deceleration drying period, when the internal moisture diffusion rate slows, continued high-temperature, low-humidity drying will directly lead to the decomposition and loss of active ingredients such as ginsenosides due to the high temperature and prolonged heating. Summary of the Invention

[0005] The purpose of the present invention is to provide a drying device and method for reducing the loss of active ingredients of American ginseng, so as to solve one or more technical problems existing in the prior art and at least provide a beneficial option or create conditions.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows: The present invention provides a drying device for reducing the loss of active ingredients of American ginseng, comprising: The drying box has two side walls with multi-layer height-adjustable tray supports, a first isolation chamber and a second isolation chamber at the bottom, the first isolation chamber is provided with an air supply flow chamber, the tray support is provided with a tray for placing American ginseng and a porous flow plate located below the tray, an air duct gap is provided between the porous flow plate and the tray, and the air supply flow chamber is connected to the porous flow plate; A guide cover is located above the drying box body, and a plurality of supporting brackets are provided on both side walls of the drying box body at the same horizontal height. The bottom edge of the guide cover is overlapped on the supporting bracket, and the top edge is inclined toward the center of the drying box body. The top edges of the guide cover plates on both sides are separated to form an upward airflow channel. The side walls of the drying box body are provided with an annular water collecting trough, and the annular water collecting trough is located below the bottom edge of the guide cover plate; An air supply unit having a centrifugal fan and a circulating air duct, wherein the centrifugal fan is arranged in the second isolation chamber, the air outlet end of the centrifugal fan is connected to the air supply flow chamber, and the air inlet end is connected to the first isolation chamber, one end of the circulating air duct is arranged on the top of the drying box and is connected to the space inside the drying box, and the other end is connected to the first isolation chamber; The heat pump unit has a heat release side and a heat absorption side, the heat release side is located in the first isolation cavity, and the heat absorption side is embedded in the guide cover, so that when the hot and humid gas rises to the guide cover, it is cooled and forms condensed water, and the condensed water flows along the surface of the guide cover to the annular water collecting tank; The atomizing unit comprises a water tank and an atomizer. The water tank is connected to the annular water collecting tank through a return pipe, the atomizer is connected to the water tank through an atomizing pipe, and the atomizing nozzle of the atomizer is arranged at the air outlet end of the centrifugal fan.

[0007] During operation, the heat pump unit and the centrifugal fan are started. The centrifugal fan draws in air from the drying box through the circulating air duct. The air first passes through the heat release side of the heat pump unit and is heated to become dry hot air. The air is then blown into the air supply equalizing chamber and then becomes a uniform vertical upward hot air flow through the porous equalizing plate. The hot air flow penetrates the American ginseng layer on the tray, takes away moisture and dries it. The hot air flow becomes humid hot air, which rises to the top of the drying box. At this time, it exchanges heat with the heat absorption side embedded in the guide cover. The humid hot air is cooled, and the water vapor is condensed into liquid water. The condensed water flows along the surface of the guide cover to the annular water collecting tank and flows into the water storage tank through the return pipe. The dehumidified and cooled air is again sucked in by the centrifugal fan through the circulating air duct and the first isolation chamber for circulation. During the speed-down drying period, when the relative humidity in the drying box is too low, such as below 40% RH, the atomizer is started to atomize the condensed water in the water tank and spray it into the air outlet of the centrifugal fan through the atomizing nozzle. After mixing with the dry hot air, it is sent into the drying box together, so that the condensed water containing the volatile flavor substances and active ingredients of American ginseng is sprayed back onto the surface of American ginseng.

[0008] This technical solution utilizes an air flow cavities and porous flow plates to improve drying uniformity, effectively preventing localized overheating or insufficient drying. This solves the uneven drying problem of the upper and lower layers caused by improper airflow organization in traditional equipment, and avoids degradation of active ingredients caused by localized overheating. By introducing a heat pump unit, the energy efficiency ratio (COP) is significantly higher than that of traditional electric heating. The closed drying chamber and the circulating air duct of the air supply unit ensure that most heat and moisture circulate within the drying chamber, requiring only a small amount of fresh air, reducing exhaust heat loss, achieving extremely high energy efficiency, and significantly reducing operating costs. In addition to serving as a cooling source for the heat pump unit, the heat absorption side also performs dehumidification and condensation functions. The collected condensate contains volatile flavor compounds and some active ingredients that evaporate with the water during the initial drying phase. This condensate is then sprayed back onto the ginseng surface during the deceleration drying phase, effectively reattaching these high-value ingredients to the surface, directly reducing active ingredient loss. During the deceleration drying period, atomization humidification can also accurately control the relative humidity of the drying environment to prevent the surface of American ginseng from hardening and forming a crust due to rapid water loss, thereby ensuring the smooth outward migration of internal moisture, achieving gentle drying at a lower temperature, and protecting heat-sensitive ingredients such as ginsenosides.

[0009] As an extension of the above solution, the tray features a double-layered mesh structure, with a bottom layer consisting of a load-bearing frame with reinforced ribs and an upper layer consisting of a fine-mesh screen. The fine-mesh screen, made of food-grade stainless steel, ensures airflow through the ginseng in all directions, preventing the formation of drying dead spots on the bottom contact surface. The reinforced ribs prevent the tray from deforming when fully loaded with ginseng, thus ensuring the longevity and safety of the equipment.

[0010] As an extension of the above solution, the air distribution chamber is equipped with air ducts along the side walls of the drying box. These ducts connect to the bottom or side of the porous distribution plate, allowing the hot air from the air distribution chamber to flow through the ducts, the porous distribution plate, and the gaps in the air ducts to the American ginseng on the tray. This extension replaces the traditional centralized bottom air supply with independent air supply to each layer through sidewall ducts, further eliminating vertical drying unevenness.

[0011] As an extension of the above solution, the bottom surface of the porous flow equalizing plate is inclined from the center toward the edge, and the edge of the bottom surface extends along the inclined direction, with the end of the extension at least directly above the edge of the tray. The extended end ensures that water droplets drip outside the tray area and avoid dripping onto the surface of the American ginseng.

[0012] As an extension of the above solution, the outermost edge of the annular sump, which protrudes from the drying chamber sidewall, is offset from the edge of the tray. This allows water droplets condensing on the outer wall of the annular sump to drip outside the edge of the tray. This offset ensures that any water droplets that form there also fall outside the tray, providing complete protection.

[0013] As an extension of the above solution, the first isolation chamber is equipped with a fresh air supply duct and an exhaust gas exhaust duct. The fresh air supply duct is equipped with a fresh air solenoid valve, and the exhaust gas exhaust duct is equipped with an exhaust gas solenoid valve. During the initial drying process, American ginseng evaporates a large amount of water, and the humidity inside the drying chamber rises rapidly, far exceeding the heat pump's dehumidification capacity. At this time, the exhaust gas solenoid valve can be opened to quickly discharge some of the high-humidity air through the exhaust gas exhaust duct, while fresh air is replenished through the fresh air supply duct to maintain drying power. In the later stages of drying, when water evaporation is minimal, the fresh air solenoid valve and the exhaust gas solenoid valve are completely closed, causing the drying chamber to enter internal circulation mode, achieving energy-saving effects.

[0014] As an extension of the above solution, a bypass line is installed on the heat release side of the heat pump unit. One end of the bypass line is connected to the circulating air duct, and the other end is located at the air inlet of the centrifugal fan. This allows some air to enter the centrifugal fan without passing through the heat release side. A bypass solenoid valve is installed on the bypass line. During the deceleration drying period, to prevent overdrying and energy waste, the bypass solenoid valve can be opened to allow some air to circulate directly without passing through the condenser. This maintains an appropriate humidity level in the drying chamber, prevents excessive hardening of the surface, and protects the active ingredients.

[0015] As an extension of the above solution, the heat pump unit features a fin-tube heat exchanger on the heat-releasing side and an evaporator on the heat-absorbing side. The unit also includes a compressor and an expansion valve, which are located outside the drying chamber and connected to the condenser and evaporator via copper tubes. The fin-tube heat exchanger and condenser evaporator increase the heat exchange area and improve energy efficiency. Placing vibrating and heat-generating components like the compressor and expansion valve outside the drying chamber prevents vibration from interfering with airflow and heat from affecting the temperature inside the chamber, thereby improving system stability and control precision.

[0016] As an extension of the above solution, the atomization pipeline is equipped with an atomizing solenoid valve and a water pump. The atomizing solenoid valve is activated during the deceleration drying period, allowing condensed water containing volatile flavor substances and active ingredients in American ginseng to be sprayed back onto the surface of the American ginseng through the atomizing nozzle. The deceleration drying period is the period during the American ginseng drying process when the drying rate decreases because the internal water diffusion rate cannot keep up with the surface evaporation rate. The condensed water is sprayed back in a micro-atomized form during the deceleration drying period, overcoming the technical challenges of uneven drying and active ingredient loss caused by surface hardening, while also enabling the recovery of high-value ingredients.

[0017] On the other hand, the present invention also provides a drying method for reducing the loss of active ingredients of American ginseng, which is performed using the above-mentioned drying device for reducing the loss of active ingredients of American ginseng, and comprises the following steps: During the preheating period, place the tray containing the American ginseng to be dried on the tray support inside the drying chamber, set the first target temperature to 35°C-38°C, start the centrifugal fan at medium-low speed, start the heat pump unit to increase the temperature of the air as it flows through the heat release side, and allow the relative humidity in the drying chamber to naturally rise to above 85%RH. The drying time is 0.5-1 hour. During the constant-speed drying period, the temperature is gradually raised to the second target temperature of 50°C-55°C. The compressor of the heat pump unit is controlled to run at full power. The heat-absorbing side of the guide cover condenses the rising hot air flow, forming condensed water containing active ingredients on the surface of the guide cover. The condensed water converges into the annular water collection tank and flows to the water storage tank. At the same time, the centrifugal fan is controlled to run at high speed. The real-time weight value W of the tray is obtained and a weight loss curve is formed according to the drying time. When the weight loss curve begins to slow down, it means that the free water on the surface of the American ginseng is basically removed and the drying process begins. The weight loss curve begins to slow down as the weight difference ΔW per unit time n. n The weight difference ΔW compared to the previous unit time n-1 n-1 The weight difference ΔW per unit time is small and less than the set threshold k. n =W max -W min , Wmax and W min are the highest real-time weight value and the lowest real-time weight value per unit time, respectively, and the threshold k is set to a preset constant value; During the deceleration drying period, the temperature is lowered to the third target temperature of 45°C-48°C to prevent slow internal moisture migration of the American ginseng, which may lead to surface hardening and cracking. The centrifugal fan is adjusted to medium speed to avoid excessive wind force causing local overdrying. The real-time relative humidity value in the drying chamber is obtained. When the real-time relative humidity value is less than the set lower limit threshold, the atomizer unit is controlled to start intermittently. The atomizer atomizes the condensed water in the water storage tank and sprays it to the air outlet of the centrifugal fan through the atomizing nozzle, so that the condensed water containing the volatile flavor substances and active ingredients of the American ginseng is sprayed back onto the surface of the American ginseng. When the real-time relative humidity value returns to the set upper threshold, the atomizing unit will stop working; When the American ginseng reaches the target moisture content, drying is completed.

[0018] The present invention intermittently back-sprays the condensed water through an atomizer during the deceleration drying period, which can slightly increase the ambient humidity, slow down the evaporation rate of water on the surface of American ginseng, and keep the surface microstructure permeable to a certain extent, opening a channel for the escape of water inside the American ginseng. At the same time, the volatile active ingredients carried in the back-sprayed droplets can adhere to the surface of the American ginseng again, reducing the loss of active ingredients. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments; Figure 1 1 is a schematic structural diagram of a drying device according to an embodiment; Figure 2 is a schematic structural diagram of a tray of an embodiment; Figure 3 is a schematic structural diagram of a drying device according to another optional embodiment; Figure 4 yes Figure 3 Schematic diagram of the locally enlarged structure at point A in the middle.

[0020] In the accompanying drawings: 100: drying box, 110: tray bracket, 120: first isolation chamber, 121: fresh air supply duct, 122: exhaust gas exhaust duct, 130: second isolation chamber, 140: air supply equalization chamber, 141: air supply duct, 150: tray, 151: load-bearing frame, 152: fine mesh screen, 160: porous flow equalization plate, 170: annular water collecting trough, 200: guide cover, 210: supporting bracket, 310: centrifugal fan, 320: circulating air duct, 410: heat release side, 420: heat absorption side, 430: bypass pipe, 510: water storage tank, 520: atomizer, 521: atomizing nozzle, 530: water pump. DETAILED DESCRIPTION

[0021] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it should not be understood as a limitation on the scope of protection of the present invention.

[0022] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0023] In the description of the present invention, if there are words such as "several", it means one or more, and "more" means more than two. Greater than, less than, and exceed are understood as not including the number itself, and above, below, and within are understood as including the number itself.

[0024] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0025] Reference Figures 1 to 4 , several embodiments of the drying device and method for reducing the loss of active ingredients of American ginseng of the present invention are given below.

[0026] like Figures 1 to 2 As shown, an embodiment of the present invention provides a drying device for reducing the loss of active ingredients of American ginseng, comprising: The drying box 100 has multi-layer height-adjustable tray supports 110 on both side walls thereof, a first isolation chamber 120 and a second isolation chamber 130 at the bottom, the first isolation chamber 120 is provided with an air supply flow chamber 140, the tray support 110 is provided with a tray 150 for placing American ginseng and a porous flow equalizing plate 160 located below the tray 150, the porous flow equalizing plate 160 is a porous aluminum plate or a stainless steel plate, a flow equalizing cavity is provided in the plate body for the flow of hot air, a plurality of holes are opened on the upper surface of the plate body, the hole diameter is 3mm-8mm, the hole shape can be a circular hole or a louver-type strip hole, there is an air duct gap between the porous flow equalizing plate 160 and the tray 150, the air duct gap is between 50mm-150mm, and the air supply flow equalizing chamber 140 is connected to the porous flow equalizing plate 160; The guide cover 200 is located above the drying box 100. A plurality of support brackets 210 are provided on both side walls of the drying box 100 at the same height. The bottom edge of the guide cover 200 overlaps the support brackets 210, and the top edge is inclined toward the center of the drying box 100. The top edges of the guide covers 200 on both sides are spaced apart to form an upward airflow channel. The side walls of the drying box 100 are provided with an annular water collecting trough 170, which is located below the bottom edge of the guide cover 200. An air supply unit having a centrifugal fan 310 and a circulating air duct 320. The centrifugal fan 310 provides power for forced circulation of air within the drying box 100 and the circulating air duct 320. The centrifugal fan 310 is disposed in the second isolation chamber 130. The air outlet of the centrifugal fan 310 communicates with the air supply equalizing chamber 140, and the air inlet is connected to the first isolation chamber 120. One end of the circulating air duct 320 is disposed at the top of the drying box 100 and communicates with the interior of the drying box 100, and the other end is connected to the first isolation chamber 120. The heat pump unit has a heat release side 410 and a heat absorption side 420. The heat release side 410 is located in the first isolation cavity 120, and the heat absorption side 420 is embedded in the guide cover 200. When the hot and humid gas rises to the guide cover 200, it is cooled and forms condensed water. The condensed water flows along the surface of the guide cover 200 to the annular water collecting tank 170. The heat release side 410 is the condenser of the heat pump unit, and the heat absorption side 420 is the evaporator of the heat pump unit. The atomizing unit includes a water tank 510 and an atomizer 520. The water tank 510 is connected to the annular water collecting tank 170 through a return pipe, and the atomizer 520 is connected to the water tank 510 through an atomizing pipe. The atomizing nozzle 521 of the atomizer 520 is arranged at the air outlet end of the centrifugal fan 310. The air flow velocity here is high and the disturbance is severe. The atomized tiny droplets (particle size less than 30 μm) can be instantly blown away and vaporized, and fully mixed with the hot air to form a uniform humid hot air flow that enters the drying box 100, avoiding the situation where the local American ginseng is directly sprayed and over-wet.

[0027] In this embodiment, the drying box is a fully enclosed, insulated box with stainless steel inner and outer walls and a high-strength polyurethane foam insulation material filling the center. A door is provided on one side of the drying box for the entry and exit of trays and the materials on them. The door utilizes high-temperature-resistant silicone sealing strips, and all conduit and pipe threading points are sealed to ensure airtightness. The two side guide covers are arranged in an "eight" shape. This embodiment is illustrated with the guide covers positioned left and right. Their bottom edges provide a clearance between the left and right walls of the drying box to allow for the rise of hot air. The guide covers can be tilted and fixed by providing fixings or support brackets on the front and rear walls of the drying box. The front and rear sides of the guide covers overlap the support brackets or are secured with fixings. The front and rear edges of the guide covers also provide a clearance between the front and rear walls of the drying box to allow for the rise of hot air. Therefore, the hot and humid air passing through the American ginseng can not only rise through the airflow channel between the left and right guide covers, but can also flow through the gaps between the guide covers and the side walls of the drying box.

[0028] During operation, the heat pump unit and the centrifugal fan are started. The centrifugal fan draws in air from the drying box through the circulating air duct. The air first passes through the heat release side of the heat pump unit and is heated to become dry hot air. The air is then blown into the air supply equalization cavity and then becomes a uniform vertical upward hot air flow through the porous equalization plate. The hot air flow penetrates the American ginseng layer on the tray, takes away moisture and dries it. The hot air flow becomes humid hot air, which rises to the top of the drying box. At this time, it exchanges heat with the heat absorption side or evaporator embedded in the guide cover. The humid hot air is cooled, and the water vapor is condensed into liquid water. The condensed water flows along the surface of the guide cover to the annular water collection tank and flows into the water storage tank through the return pipe. The dehumidified and cooled air is sucked in again by the centrifugal fan for circulation.

[0029] During the speed-down drying period, when the relative humidity in the drying box is too low, such as below 40% RH, the atomizer is started to atomize the condensed water in the water storage tank and spray it to the air outlet of the centrifugal fan through the atomizing nozzle. After mixing with the dry hot air, it is sent into the drying box together, so that the condensed water containing the volatile flavor substances and active ingredients of American ginseng is sprayed back onto the surface of American ginseng.

[0030] This embodiment uses a heat pump unit as the heating unit. It does not directly generate electricity for heating, but rather transports heat. The energy efficiency ratio (COP) is usually much higher than 1. Active dehumidification of hot and humid air at the top through the heat-absorbing side can effectively reduce the humidity in the drying box. The humidity will be significantly reduced as the moisture is condensed and carried away. Compared with the traditional hot air drying mode that relies solely on dehumidification and ventilation to reduce humidity, this is more efficient and has less heat loss.

[0031] It should be noted that the condensed water collected in this embodiment is not ordinary water; it is condensed water containing volatile flavor substances and active ingredients of American ginseng, also known as "American ginseng dew." During the preheating period or the constant-rate drying period, some low-boiling-point volatile oils, some volatile active ingredients, and some aroma components on the surface of the American ginseng evaporate along with the water, eventually condensing on the surface of the guide cover, forming condensed water containing volatile flavor substances and active ingredients of American ginseng.

[0032] In traditional American ginseng drying, its hot and humid water vapor is typically discharged directly as exhaust gas, resulting in heat waste and direct loss of active ingredients. This embodiment introduces a heat pump unit with a heat-releasing side and a heat-absorbing side. Heat exchange is performed on the heat-absorbing side, condensing the hot and humid airflow into liquid water. This not only reduces heat loss but also actively dehumidifies the circulating airflow. The condensed water can also be used for humidification and sprayed back onto the surface of the American ginseng, reducing the loss of its active ingredients.

[0033] Those skilled in the art will appreciate that the drying process of American ginseng is not linear and is generally divided into three stages: a preheating period, a constant-rate drying period, and a decreasing-rate drying period. During the preheating period, the material temperature rises, increasing the drying rate. During the constant-rate drying period, surface moisture evaporates freely, while internal moisture continuously diffuses to the surface, maintaining a constant drying rate. During this period, the evaporation primarily occurs in free water. During the decreasing-rate drying period, the internal moisture diffusion rate cannot keep up with the surface evaporation rate, resulting in a decrease in the drying rate. At this point, bound water and some active ingredients evaporate, and the material temperature begins to rise. During the transition from the constant-rate drying period to the decreasing-rate drying period, if the external environment is too dry (low humidity), the surface of the American ginseng will shrink rapidly due to rapid water loss, forming a dense, hardened layer on the microstructure. This hard shell severely hinders the outward migration of internal moisture. To expel this internal moisture, the drying time must be extended or the temperature must be increased, which in turn exacerbates the degradation and loss of heat-sensitive active ingredients (such as ginsenosides). In this embodiment, the collected condensed water is sprayed back by the atomizing unit during the deceleration drying period, and the evaporation rate of the water on the surface of the American ginseng is slowed down by slightly increasing the relative humidity of the environment, so that the surface microstructure maintains a certain permeability, opening a channel for the escape of water inside the American ginseng.

[0034] In this embodiment, the condensed water is sprayed back onto the surface of the American ginseng during the deceleration drying period, thereby delaying the hardening of the surface of the American ginseng and maintaining the channel for the internal moisture of the American ginseng to migrate outward, so that drying can be carried out more continuously. Compared with the traditional drying scheme, the traditional drying rate continues to decrease because the internal moisture migration path is blocked due to surface hardening, and the drying becomes extremely slow. The drying rate of this embodiment is maintained or slowed down to a reduced extent.

[0035] In traditional drying methods, because water evaporation is reduced, more heat is used to heat the material itself, resulting in a rapid and high temperature rise, which puts heat-sensitive ingredients at risk of degradation. In this embodiment, the water sprayed back evaporates on the surface of the American ginseng, removing heat, i.e., evaporation absorbs heat, achieving an evaporative cooling effect, effectively controlling the surface temperature of the American ginseng. The temperature rise is slower and the peak temperature is lower. This directly avoids the damage of high temperatures to the active ingredients of the American ginseng, and is the most direct means to reduce the loss of active ingredients.

[0036] In order to expel the last bit of bound water, traditional drying schemes require the equipment to run for a long time, consuming a lot of energy, but the dehydration effect is minimal. In this embodiment, because the drying rate can be maintained or slowed down to a reduced extent, the total drying time may be shortened, avoiding the high energy consumption caused by blindly increasing the temperature to break through the surface hardening. The evaporation of a small amount of water is exchanged for a reduction in overall energy consumption, thereby improving the rationality of energy utilization. In this embodiment, the goal of the initial drying stage (preheating period and / or constant speed drying period) is to reduce the absolute humidity and dehumidify with all efforts, while the goal of the speed-decreasing drying period is to regulate the relative humidity and prevent quality deterioration. During the speed-decreasing drying period, the importance of maintaining the high quality of American ginseng has surpassed the pursuit of drying speed. A negligible increase in drying time (which may even shorten the total time) is exchanged for a significant increase in the retention rate of active ingredients.

[0037] This invention improves drying uniformity through an air flow cavities and porous flow plates, effectively preventing local overheating or insufficient drying. This solves the uneven drying problem of the upper and lower layers caused by improper airflow organization in traditional equipment and avoids degradation of active ingredients caused by localized overheating. By introducing a heat pump unit, its energy efficiency ratio (COP) is far higher than that of traditional electric heating. The closed drying chamber and the circulating air duct of the air supply unit allow the majority of heat and moisture to circulate within the drying chamber, requiring only a small amount of fresh air, reducing exhaust heat loss, achieving high energy efficiency, and significantly lowering operating costs. In addition to serving as a cooling source for the heat pump unit, the heat absorption side also performs dehumidification and condensation functions. The collected condensate contains volatile flavor substances and some active ingredients that evaporate with the water during the initial drying phase. Re-spraying this condensate during the deceleration drying phase effectively reattaches these high-value ingredients to the surface of the American ginseng, directly reducing the loss of active ingredients. During the deceleration drying period, atomization humidification can also accurately control the relative humidity of the drying environment to prevent the surface of American ginseng from hardening and forming a crust due to rapid water loss, thereby ensuring the smooth outward migration of internal moisture, achieving gentle drying at a lower temperature, and protecting heat-sensitive ingredients such as ginsenosides.

[0038] In an optional embodiment, if Figure 2As shown, the tray 150 is a double-layered mesh structure, with a bottom layer consisting of a load-bearing frame 151 with reinforcing ribs, and an upper layer consisting of a fine mesh screen 152. The fine mesh screen is made of food-grade stainless steel, ensuring that airflow can fully penetrate the American ginseng and preventing the formation of drying dead corners on the bottom contact surface. The reinforcing ribs are arranged in a "well" or "sun" shape at the bottom of the load-bearing frame, ensuring that the tray will not deform when fully loaded with American ginseng, thereby ensuring the service life and safety of the equipment.

[0039] In an optional embodiment, if Figure 1 and Figure 3 As shown, the air supply flow chamber 140 is provided with an air supply duct 141 along the side wall of the drying box 100, and the air supply duct 141 is connected to the bottom or side of the porous flow plate 160 (such as Figure 3 The branch port of the air supply duct shown is directly connected to the side of the porous flow equalizing plate. It should be noted that the porous flow equalizing plate is provided with a flow equalizing cavity composed of a conventional flow equalizing orifice plate or a flow equalizing barrier and other structures. The flow equalizing cavity can achieve that even if the air enters from different positions, the air outlet of the porous flow equalizing plate is still uniform through the flow equalizing structure in the cavity. The flow equalizing structure in the porous flow equalizing plate is realized by the existing technology, so that the hot air in the air supply flow equalizing cavity 140 flows through the air supply duct 141, the porous flow equalizing plate 160, and the air duct gap to the American ginseng on the tray 150. The air supply duct is a vertical main air duct that is drawn out from the air supply flow equalizing cavity and attached to the side wall of the drying box. Then a branch port is opened at the height corresponding to each layer of trays, and is connected to the side or bottom of each porous flow equalizing plate through a hose or flange. This embodiment changes the traditional bottom centralized air supply to independent air supply to each layer through the side wall duct, further eliminating the vertical drying unevenness.

[0040] In an optional embodiment, if Figure 3 and Figure 4 As shown, the bottom surface of the porous flow equalizing plate 160 is tilted from the center to the edge, and the edge of the bottom surface extends along the tilted direction, with the end of the extension at least passing directly above the edge of the tray 150 .

[0041] In the present embodiment, during the drying process, even if a trace amount of condensed water is formed at the bottom of the porous equalizing plate, its inclined surface liquid will guide the water droplets to the edge, and the extended end will ensure that the water droplets drip outside the tray area to avoid dripping on the surface of the American ginseng. It will be understood by those skilled in the art that during the rising process of the hot air flow, its temperature is much higher than the dew point temperature, so the possibility of a large amount of condensation at the bottom of the porous equalizing plate before rising to the upper heat release side or evaporator is extremely low. The main condensation phenomenon of the present invention only occurs on the surface of the guide cover plate whose temperature is actively cooled. In actual drying production, even if a trace amount of water droplets fall on the surface of the American ginseng where hot air continues to pass through, because its surrounding environment is dry hot air and the water droplets are temporarily on the surface of the American ginseng instead of penetrating into the interior, the water droplets will be quickly re-evaporated, and the effect on the overall drying effect and the retention of active ingredients will be minimal.

[0042] In an optional embodiment, if Figure 1 and Figure 3 The outermost edge of the annular water collecting trough 170 protruding from the side wall of the drying box 100 is staggered with the edge of the tray 150, so that water droplets condensed on the outer wall of the annular water collecting trough drip outside the edge area of ​​the tray.

[0043] In this embodiment, the temperature of the water collecting trough for collecting condensed water is relatively low. When the rising hot and humid air contacts its outer wall, it is possible for water droplets to condense on the outer wall surface. The staggered arrangement ensures that the water droplets formed here will fall outside the range of the tray, forming a complete protection. In some preferred embodiments, the bottom of the annular water collecting trough is inclined, such as Figure 1 The bottom wall of the annular water collecting trough 170 is tilted, so that the water droplets condensed on the outermost edge of the surface drip along the bottom tilt toward the side wall of the drying box and gather at the bottom wall of the drying box. The water storage tank 510 is provided with a return branch pipe 511 extending into the bottom wall of the drying box 100 to collect the condensed water on the bottom wall. The return branch pipe 511 is tilted or provided with a one-way valve to prevent the condensed water on the annular water collecting trough from flowing back into the drying box during the process of flowing into the water storage tank through the return pipe. In actual drying production, since the middle or lower part of the drying box is in dry hot air, a small amount of water droplets will quickly evaporate again during the process of sliding down, and the amount of condensed water that can be collected on the bottom wall of the drying box is limited. This preferred embodiment can set a slope on the bottom wall of the drying box so that the condensed water on the bottom wall can naturally flow toward the inlet of the return branch pipe, thereby avoiding the accumulation of condensed water on the bottom wall of the drying box. Therefore, the bottom setting of the porous flow equalizing plate in this embodiment and the above-mentioned optional embodiment can effectively avoid the risk of trace condensation water that may be generated on the surface of internal components dripping onto the material during the drying process, further improving the reliability of the device and product quality.

[0044] In an optional embodiment, if Figure 1 As shown, the first isolation chamber 120 is provided with a fresh air supply duct 121 and an exhaust gas exhaust duct 122, the fresh air supply duct 121 is provided with a fresh air solenoid valve, and the exhaust gas exhaust duct 122 is provided with an exhaust gas solenoid valve. The functions and structures of the fresh air supply duct and the exhaust gas exhaust duct to realize their own intake of fresh air and exhaust of exhaust gas are realized by existing technologies, which will not be elaborated here. In the early stage of drying, the amount of water evaporated by American ginseng is huge, and the humidity in the drying box rises rapidly, far exceeding the dehumidification capacity of the heat pump. At this time, the exhaust gas solenoid valve can be opened to quickly discharge part of the high-humidity air through the exhaust gas exhaust duct, and at the same time, fresh air can be replenished through the fresh air supply duct to maintain the drying power. In the later stage of drying, the amount of water evaporation is small, so the fresh air solenoid valve and the exhaust gas solenoid valve are completely closed, so that the drying box enters the internal circulation mode to achieve energy-saving effects.

[0045] In an optional embodiment, if Figure 1 As shown, a bypass line 430 is provided on the heat release side 410 of the heat pump unit. One end of the bypass line 430 is connected to the circulating air duct 320, and the other end is located at the air inlet end of the centrifugal fan 310, so that part of the air flow enters the centrifugal fan 310 for circulation without passing through the heat release side 410. A bypass solenoid valve is provided on the bypass line 430. In this embodiment, during the initial drying period (preheating period and / or constant speed drying period), the American ginseng has a high water content and requires a large amount of moisture removal. At this time, the bypass solenoid valve is closed, and all wet air is strongly dehumidified through the heat release side. During the deceleration drying period, to prevent over-drying and energy waste, the bypass solenoid valve can be opened to allow part of the air to circulate directly without passing through the condenser, thereby maintaining an appropriate humidity level in the drying chamber, preventing excessive hardening of the epidermis, and protecting the active ingredients.

[0046] In an optional embodiment, if Figure 1 As shown, the heat-releasing side 410 of the heat pump unit is a condenser that adopts fin-tube heat exchange, and the heat-absorbing side 420 of the heat pump unit is an evaporator that adopts fin-tube heat exchange. The heat pump unit also includes a compressor and an expansion valve (not shown in the figure). The compressor and expansion valve are placed outside the drying box 100 and connected to the condenser and evaporator through copper tubes. The application of the compressor and expansion valve of the heat pump unit in the heat pump system and the working principle of realizing energy transfer are conventional technologies and will not be described in detail here. The condenser and evaporator with fin-tube heat exchange can increase the heat exchange area and improve energy efficiency. The vibrating and heat-generating components such as the compressor and expansion valve are placed outside the drying box, which avoids the interference of vibration on the airflow organization in the drying box and the influence of heat on the temperature inside the drying box, thereby improving the stability of the system and the control accuracy.

[0047] In an optional embodiment, if Figure 1As shown, the atomizing pipe is provided with an atomizing solenoid valve and a water pump 530. The atomizing solenoid valve is opened during the deceleration drying period, so that the condensed water containing the volatile flavor substances and active ingredients of American ginseng is sprayed back to the surface of American ginseng through the atomizing nozzle 521. The deceleration drying period is the period during the drying process of American ginseng when the drying rate decreases because the internal moisture diffusion rate cannot keep up with the surface evaporation rate.

[0048] In this embodiment, the atomizing unit is not always on, but is turned on during the deceleration drying period. In the early stages of drying, such as the preheating period and / or the constant-speed drying period, the moisture content of the material is high, the self-evaporation is strong, and the humidity in the drying chamber is high. At this time, full dehumidification is required to reduce the absolute humidity and drive water evaporation. Back-spraying will increase the humidity burden and prolong the drying time. In this embodiment, the intermittent operation is controlled by the atomizing solenoid valve and the water pump during the deceleration drying period. When the humidity sensor detects that the humidity is lower than the lower limit of the set value, such as 40% RH, the atomizing solenoid valve and the water pump are turned on, and the atomizer works intermittently, such as atomizing for 10 seconds and pausing for 30 seconds, atomizing the condensed water containing the volatile flavor substances and active ingredients of American ginseng and spraying it to the outlet of the centrifugal fan through the atomizing nozzle. It is mixed with air and sent into the air supply equalization chamber and then flows to the surface of the American ginseng. The volatile active ingredients carried in the back-sprayed droplets can be attached to the surface of the American ginseng again, which is equivalent to a dynamic ingredient recovery process, reducing the loss of active ingredients.

[0049] When the humidity returns to the upper limit, such as 50% RH, the atomization operation is stopped. The intermittent atomization method of this embodiment can accurately maintain the humidity of the drying environment at 40-50% RH during the deceleration drying period, which can effectively prevent the active ingredients from being dried out or oxidized in a high temperature and low humidity environment, and achieve gentle drying from the inside out, avoiding surface hardening and component damage caused by over-drying, and preventing the material from rehydrating.

[0050] This embodiment sprays condensed water back in a trace amount of atomization during the deceleration drying period of American ginseng, overcoming the technical difficulties of uneven drying inside and outside and loss of active ingredients caused by surface hardening, while achieving the recycling of high-value ingredients.

[0051] In some embodiments, the water storage tank is provided with a pipeline connected to a concentration device. In this embodiment, after the condensed water is collected, it is guided through a pipeline to a small external concentration device, such as a thin film evaporator or a small vacuum concentrator. A valve is provided on the pipeline to switch between back-spray mode and concentration mode. When the condensed water does not need to be back-sprayed or for other process reasons, it can be guided out and concentrated into a high-value-added "American ginseng essence" product. In some preferred embodiments, the condensed water in the water storage tank can also be used for cleaning or a short spray pretreatment of the next batch of fresh American ginseng. The residual components in the condensed water are used to form a protective film on the surface of the fresh American ginseng before drying, which may reduce the loss of internal components during the subsequent drying process.

[0052] In some embodiments, the drying box is equipped with a temperature sensor and a humidity sensor, and the tray holder is equipped with a weight sensor. The temperature and humidity sensors are located at least at the top, middle, and bottom of the drying box to monitor the environmental gradient within the box. The weight sensor is used to monitor the weight change of each tray, and the weight change is used to monitor water loss. For example, a weight loss curve can be generated based on the real-time weight value according to the drying time. It will be understood by those skilled in the art that when multiple temperature sensors or humidity sensors are set, in the process of judging the real-time values ​​in other embodiments, the real-time values ​​of sensors at different positions should be obtained according to the actual working conditions for judgment and setting. For example, when it is necessary to judge whether the real-time temperature value reaches the target temperature, as long as the real-time temperature value of one of the temperature sensors meets the requirement, it can be regarded as meeting the standard; for example, when monitoring humidity, when the real-time humidity value of one of the humidity sensors in the drying box is lower than the set lower limit, it can be regarded as meeting the condition, and then subsequent setting operations are performed. Since the upper, middle and lower positions are in the same closed space, the real-time values ​​of the multiple temperature sensors or humidity sensors in actual production will not differ too much, and the deviation between multiple similar sensors will not cause substantial changes to the purpose and technical effects of the present invention. Therefore, the specific implementation means of monitoring and the specific position installation setting of the sensor can be set by technical personnel according to actual production requirements, and no further details will be given here.

[0053] On the other hand, an embodiment of the present invention further provides a drying method for reducing the loss of active ingredients of American ginseng, which is performed using a drying device for reducing the loss of active ingredients of American ginseng as described in one embodiment or a combination of multiple optional embodiments. Figures 1 to 4 As shown, the following steps are included: During the preheating period, the tray 150 containing the American ginseng to be dried is placed on the tray support 110 in the drying box 100, the first target temperature is set to 35°C-38°C, the centrifugal fan 310 is started at a medium-low speed, the heat pump unit is started to increase the temperature of the air passing through the heat release side 410, and the relative humidity in the drying box 100 is allowed to naturally rise to above 85%RH. The drying time is 0.5-1 hour; During the constant-speed drying period, the temperature is gradually raised to a second target temperature of 50°C-55°C. The compressor of the heat pump unit is controlled to operate at full power. The heat-absorbing side 420 of the guide cover 200 condenses the rising hot air flow, forming condensed water containing active ingredients on the surface of the guide cover 200. The condensed water is then collected in the annular sump 170 and flows to the water storage tank 510. Simultaneously, the centrifugal fan 310 is controlled to operate at high speed. It should be noted that the condensation of the hot and humid air flow does not start from the constant-speed drying period. During the preheating period, due to the relatively high humidity and the heat-absorbing side of the heat pump unit as a cold source is already in working condition, the condensation of the hot and humid air flow has already begun from the preheating period. The constant-speed drying period of this embodiment is to improve the efficiency of condensation by running the compressor of the heat pump unit at full power, thereby accelerating the process of active dehumidification. It should be further noted that since the compressor is running at full power, the efficiency of the heat-releasing side is also improved. When the second target temperature is achieved, the additional heat can be transferred through existing technical means, such as setting up another condenser outside the drying box or in other processes, or sharing the energy released by the heat-releasing side of the present invention by setting up another hot air duct, and outputting it to the outside for other processes, etc. This embodiment does not impose any form of limitation on this, as long as it is ensured that the heat supply and regulation of the target temperature can be achieved by using the heat-releasing side as a heating unit; The real-time weight value W of the tray 150 is obtained and a weight loss curve is formed according to the drying time. When the weight loss curve begins to slow down, it indicates that the free water on the surface of the American ginseng is basically removed and the drying process begins. The weight loss curve begins to slow down as the weight difference ΔW per unit time n. n The weight difference ΔW compared to the previous unit time n-1 n-1 The weight difference ΔW per unit time is small and less than the set threshold k. n =W max -W min , W max and W min are the highest real-time weight value and the lowest real-time weight value per unit time, respectively. The threshold value k is set as a constant value preset according to factors such as the actual American ginseng species and production conditions; That is to say, when the free water on the surface of American ginseng is basically evaporated, the weight loss will enter a slowdown stage, because the water evaporated by continued drying is the water inside the American ginseng, and the evaporation rate of the internal water is slower than the evaporation rate of the free water on the surface. This stage can be clearly reflected by the slowdown of the weight loss curve, that is, when ΔW n -ΔW n-1 When <k, it enters the speed-decreasing drying period; During the deceleration drying period, the temperature is lowered to a third target temperature of 45°C-48°C to prevent slow internal moisture migration of the American ginseng, which may lead to surface hardening and cracking. The centrifugal fan 310 is adjusted to operate at a medium speed to prevent excessive wind force from causing local overdrying. The real-time relative humidity value in the drying box 100 is obtained. When the real-time relative humidity value is less than a set lower limit threshold, such as 40% RH, the atomizer unit is controlled to start intermittently. The atomizer 520 atomizes the condensed water in the water storage tank 510 and sprays it to the air outlet of the centrifugal fan 310 through the atomizing nozzle 521, so that the condensed water containing volatile flavor substances and active ingredients of the American ginseng is sprayed back onto the surface of the American ginseng. When the real-time relative humidity value returns to the set upper threshold, such as 50%RH, the atomizing unit stops working; When the American ginseng reaches the target moisture content, drying is completed.

[0054] In this embodiment, the medium and low speed operation of the centrifugal fan during the preheating period is set relative to the high speed operation during the constant speed drying period and the medium speed operation during the speed reduction drying period. The specific speed, power and other parameters are set according to the actual amount of American ginseng, the equipment parameters of the fan and other production conditions; in the early stage of American ginseng drying, that is, the preheating period and / or the constant speed drying period, the volatile oils and some volatile active ingredients on the surface of American ginseng will evaporate together with the water vapor, so the condensed water on the guide cover is condensed water containing volatile flavor substances and active ingredients of American ginseng. In this embodiment, the condensed water is intermittently back-sprayed through the atomizer during the speed reduction drying period, which can slightly increase the ambient humidity, slow down the evaporation rate of water on the surface of American ginseng, and keep the surface microstructure to a certain degree of permeability, opening a channel for the escape of water inside the American ginseng. At the same time, the volatile active ingredients carried in the back-sprayed droplets can adhere to the surface of American ginseng again, reducing the loss of active ingredients.

[0055] Those skilled in the art will appreciate that monitoring the target moisture content of American ginseng can be achieved by monitoring weight or by other existing technical means, such as near-infrared spectroscopy, which utilizes the characteristic absorption of near-infrared light of a specific wavelength (1200-1900 nm) by water molecules, collects the near-infrared spectrum of the American ginseng surface using a spectrometer, and combines it with pre-established moisture and spectral models to calculate the moisture content in real time. Conventional technical means are used to achieve the monitoring and calculation of the target moisture content, and this embodiment does not impose any limitations thereon.

[0056] The above specifically describes the preferred embodiments of the present invention, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A drying device for reducing the loss of active ingredients of American ginseng, characterized in that: include: A drying box (100) is provided with multi-layer height-adjustable tray supports (110) on both inner side walls thereof, a first isolation chamber (120) and a second isolation chamber (130) are provided at the bottom thereof, the first isolation chamber (120) is provided with an air supply flow distribution chamber (140), the tray support (110) is provided with a tray (150) for placing American ginseng and a porous flow distribution plate (160) located below the tray (150), an air duct gap is provided between the porous flow distribution plate (160) and the tray (150), and the air supply flow distribution chamber (140) is communicated with the porous flow distribution plate (160); A guide cover plate (200) is located above the drying box (100), and a plurality of support brackets (210) at the same level are provided on both side walls of the drying box (100). The bottom edge of the guide cover plate (200) is overlapped on the support bracket (210), and the top edge is inclined toward the center of the drying box (100). The top edges of the guide cover plates (200) on both sides are spaced apart to form an upward airflow channel. The side walls of the drying box (100) are provided with an annular water collecting trough (170), and the annular water collecting trough (170) is located below the bottom edge of the guide cover plate (200); An air supply unit, comprising a centrifugal fan (310) and a circulating air duct (320), wherein the centrifugal fan (310) is arranged in the second isolation chamber (130), an air outlet end of the centrifugal fan (310) is communicated with the air supply equalizing chamber (140), and an air inlet end is connected to the first isolation chamber (120); one end of the circulating air duct (320) is arranged at the top of the drying box (100) and communicates with the space inside the drying box (100), and the other end is connected to the first isolation chamber (120); A heat pump unit having a heat releasing side (410) and a heat absorbing side (420), wherein the heat releasing side (410) is located in the first isolation cavity (120), and the heat absorbing side (420) is embedded in the guide cover (200), so that when the hot and humid gas rises to the guide cover (200), it is cooled and forms condensed water, and the condensed water flows along the surface of the guide cover (200) to the annular water collecting trough (170); The atomizing unit comprises a water storage tank (510) and an atomizer (520), wherein the water storage tank (510) is connected to the annular water collecting tank (170) via a return pipe, and the atomizer (520) is connected to the water storage tank (510) via an atomizing pipe, and the atomizing nozzle (521) of the atomizer (520) is arranged at the air outlet end of the centrifugal fan (310).

2. A drying device for reducing the loss of active ingredients of American ginseng according to claim 1, characterized in that: The tray (150) is a double-layer mesh tray structure, wherein the bottom layer is a load-bearing frame (151) with reinforcing ribs, and the upper layer is a fine mesh screen (152).

3. The drying device for reducing the loss of active ingredients of American ginseng according to claim 1, characterized in that: The air supply flow equalization chamber (140) is provided with an air supply duct (141) along the side wall of the drying box (100), and the air supply duct (141) is connected to the bottom or side of the porous flow equalization plate (160), so that the hot air in the air supply flow equalization chamber (140) flows through the air supply duct (141), the porous flow equalization plate (160), and the air duct gap to the American ginseng on the tray (150).

4. The drying device for reducing the loss of active ingredients of American ginseng according to claim 1, characterized in that: The bottom surface of the porous flow equalizing plate (160) is inclined from the center to the edge, and the edge of the bottom surface extends along the inclined direction, with the end of the extension at least passing directly above the edge of the tray (150).

5. The drying device for reducing the loss of active ingredients of American ginseng according to claim 1, characterized in that: The outermost edge of the annular water collecting trough (170) protruding from the side wall of the drying box (100) is offset from the edge of the tray (150), so that water droplets condensed on the outer wall of the annular water collecting trough (170) drip outside the edge area of ​​the tray (150).

6. The drying device for reducing the loss of active ingredients of American ginseng according to claim 1, characterized in that: The first isolation chamber (120) is provided with a fresh air supply pipe (121) and an exhaust gas exhaust pipe (122); the fresh air supply pipe (121) is provided with a fresh air solenoid valve, and the exhaust gas exhaust pipe (122) is provided with an exhaust gas solenoid valve.

7. The drying device for reducing the loss of active ingredients of American ginseng according to claim 1, characterized in that: A bypass pipe (430) is provided on the heat release side (410) of the heat pump unit. One end of the bypass pipe (430) is connected to the circulating air duct (320), and the other end is located at the air inlet end of the centrifugal fan (310), so that part of the air flow does not pass through the heat release side (410) and enters the centrifugal fan (310) for circulation. A bypass solenoid valve is provided on the bypass pipe (430).

8. The drying device for reducing the loss of active ingredients of American ginseng according to claim 1, characterized in that: The heat-releasing side (410) of the heat pump unit is a condenser that adopts fin-tube heat exchange, and the heat-absorbing side (420) of the heat pump unit is an evaporator that adopts fin-tube heat exchange. The heat pump unit also includes a compressor and an expansion valve. The compressor and the expansion valve are placed outside the drying box (100) and are connected to the condenser and the evaporator through copper pipes.

9. The drying device for reducing the loss of active ingredients of American ginseng according to claim 1, characterized in that: The atomizing pipe is provided with an atomizing solenoid valve and a water pump (530). The atomizing solenoid valve is opened during the deceleration drying period, so that the condensed water containing the volatile flavor substances and active ingredients of American ginseng is sprayed back to the surface of American ginseng through the atomizing nozzle (521). The deceleration drying period is the period during the drying process of American ginseng when the drying rate decreases because the internal water diffusion rate cannot keep up with the surface evaporation rate.

10. A drying method for reducing the loss of active ingredients of American ginseng, characterized in that: The method is performed using a drying device for reducing the loss of active ingredients of American ginseng according to any one of claims 1 to 9, comprising the following steps: During the preheating period, the tray (150) containing the American ginseng to be dried is placed on the tray support (110) in the drying box (100), a first target temperature of 35°C-38°C is set, the centrifugal fan (310) is started to run at a medium-low speed, the heat pump unit is started to increase the temperature of the air when it flows through the heat release side (410), and the relative humidity in the drying box (100) is allowed to naturally rise to above 85%RH. The drying time is 0.5-1 hour; During the constant-speed drying period, the temperature is gradually raised to a second target temperature of 50° C. to 55° C., the compressor of the heat pump unit is controlled to operate at full power, the heat-absorbing side (420) of the guide cover (200) condenses the rising hot air flow, and condensed water containing active ingredients is formed on the surface of the guide cover (200). The condensed water flows into the annular water collecting trough (170) and flows into the water storage tank (510), and the centrifugal fan (310) is controlled to operate at high speed. The real-time weight value W of the tray (150) is obtained and a weight loss curve is formed according to the drying time. When the weight loss curve begins to slow down, it indicates that the free water on the surface of the American ginseng is basically removed and the drying period begins to decrease. The weight loss curve begins to slow down as the weight difference ΔW within the unit time n. n The weight difference ΔW compared to the previous unit time n-1 n-1 The weight difference ΔW per unit time is small and less than the set threshold k. n =W max -W min , W max and W min are the highest real-time weight value and the lowest real-time weight value per unit time, respectively, and the threshold k is set to a preset constant value; During the deceleration drying period, the temperature is lowered to a third target temperature of 45°C-48°C to prevent the surface of the American ginseng from hardening and cracking due to slow migration of moisture inside the ginseng. The centrifugal fan (310) is adjusted to run at a medium speed to prevent excessive wind force from causing local overdrying. The real-time value of the relative humidity in the drying box (100) is obtained. When the real-time value of the relative humidity is less than the set lower limit threshold, the atomizer unit is controlled to start intermittently. The atomizer (520) atomizes the condensed water in the water storage tank (510) and sprays it to the air outlet of the centrifugal fan (310) through the atomizing nozzle (521), so that the condensed water containing the volatile flavor substances and active ingredients of the American ginseng is sprayed back onto the surface of the American ginseng. When the real-time relative humidity value returns to the set upper threshold, the atomizing unit will stop working; When the American ginseng reaches the target moisture content, drying is completed.

Images