Multi-heat-source multi-layer belt type heat pump drying device and drying method

Abstract

The invention discloses a multi-heat-source multi-layer belt type heat pump drying device and a drying method.The drying device comprises a drying machine main machine, a plurality of mutually-separated drying layers are arranged in the drying machine main machine, each drying layer is internally provided with a rotary net belt transmission device used for conveying materials, every two adjacent drying layers are communicated through a material changing plate which is arranged in an inclined mode, and the material changing plates are arranged in the drying machine main machine; each drying layer is divided into an air path area and a drying area through a partition plate, and the front ends and the rear ends of the air path area and the drying area on the same layer are communicated to form a circulation loop. And the air path area is provided with a circulating fan and a secondary heating device. The feeding device is arranged at one end of the drying machine main machine, the discharging device is arranged at a discharging port below the drying machine main machine, the air source heat pump machine is communicated with an air path area of the drying layer and used for conveying hot air into the drying layer, and the air return device is arranged on the side away from the air inlet device and used for discharging and recycling dry waste gas. According to the drying method based on the drying device, the heat efficiency and the waste heat utilization rate of the multi-layer belt type drying machine with the open type heat pump as a heat source are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of drying devices, and particularly to a multi-source multi-layer belt-type heat pump drying device and a drying method. Background Art

[0002] Heat pump drying is a drying technology that uses a heat pump device to consume a small amount of high-grade electric energy, and makes the material meet the drying requirements by heating and dehumidifying or using refrigeration dehumidification. A large number of studies and practices have shown that heat pump drying is a drying technology with significant energy efficiency. Especially with the development of medium and high temperature heat pump units, heat pumps as drying heat sources and energy recovery devices are gradually being applied to drying fields such as agricultural products and biochemical products. Heat pump units can be divided into open-type, semi-open and closed-type heat pump drying units according to their structural forms. Among them, open-type heat pump drying units are widely used due to their better economy. Their drying methods are usually divided into intermittent drying and continuous drying. Intermittent drying mainly uses box-type drying rooms, and continuous drying mostly uses belt dryers.

[0003] Box-type drying rooms use trays to load materials, with low automation and high manual labor intensity, which is not conducive to continuous production. Such as CN113498872A and CN218329014U. In belt dryers, the materials move with the conveyor belt. Especially in multi-layer belt dryers, the materials can also automatically fall from the upper layer to the lower layer by the action of gravity, changing their relative positions, which can strengthen heat and mass transfer, reduce uneven drying of the materials, and is more suitable for uniform and continuous drying of heat-sensitive granular materials. From existing patents, the design of belt-type heat pump dryers mainly focuses on solving drying uniformity and automatic control, such as CN115355695A. In fact, open-type heat pump drying units use heat pumps to heat air, heat and dehumidify the materials, and make the materials dry. When using only a heat pump as the heat source, at the initial stage of drying high-moisture materials, the material temperature rises slowly. At the same time, the waste heat utilization degree and environmental conditions of such dryers can significantly affect the performance coefficient and drying efficiency of the heat pump unit. The existing multi-layer belt dryers with open-type heat pumps have a low waste heat utilization degree. Summary of the Invention

[0004] The purpose of the present invention is to provide a multi-source multi-layer belt-type heat pump drying device and a drying method to solve the problems existing in the above-mentioned prior art, and improve the waste heat utilization rate of multi-layer belt dryers with open-type heat pumps as the heat source.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] The present invention provides a multi-source multi-layer belt-type heat pump drying device, including:

[0007] The main body of the dryer has multiple mutually separated drying layers inside. Each drying layer is provided with a rotary belt drive device for conveying materials. The adjacent two drying layers are connected by a slantingly arranged material-changing plate, and the rotary belt drive devices in the adjacent two drying layers rotate in opposite directions; the same drying layer is separated into an air passage area and a drying area by a partition board, and the front and rear ends of the air passage area and the drying area in the same drying layer are connected to form a circulation loop; an axial flow fan and a secondary heating device are provided in the air passage area;

[0008] The feeding device is arranged at one end of the main body of the dryer and is used for conveying materials onto the rotary belt drive device in the uppermost drying layer;

[0009] The discharging device is arranged below the other end of the main body of the dryer and is used for conveying the dried materials out;

[0010] The air source heat pump unit is connected to the air passage areas of multiple drying layers respectively through an air inlet device and is used for conveying hot air into the drying layers;

[0011] The air return device is arranged on the side far from the air inlet device. The air return device is connected to the drying area and is used for discharging the dried waste gas in the drying layer, and part of the dried waste gas is discharged to the evaporator of the air source heat pump unit and is absorbed by the evaporator for waste heat, and the other part of the dried waste gas is merged with fresh air after passing through the fresh air device and then re-enters the air source heat pump unit for heating.

[0012] Optionally, the main body of the dryer includes a heat-insulating outer shell. A main body support is arranged inside the heat-insulating outer shell. The adjacent two drying layers are mutually separated by a layered partition board, and the layered partition board is arranged on the main body support.

[0013] Optionally, the partition board in the drying layer is a vertically arranged air passage partition board. The drying layer is separated into an air passage area and a drying area by the air passage partition board. Openings for connecting the air passage area and the drying area are provided at both ends of the air passage partition board; the axial flow fan and the secondary heating device are installed in the air passage area, and the rotary belt drive device is arranged in the drying area; the air source heat pump unit is connected to the air passage area through the air inlet device, and the air return device is connected to the drying area.

[0014] Optionally, the specific structure of the secondary heating device is not limited. An electric heating device, or a biomass hot water heat exchanger, or a steam heat exchanger can be adopted. On this basis, other structures capable of achieving secondary heating can also be selected.

[0015] Optionally, the return air device includes return air straight pipes respectively communicated with the plurality of drying zones one by one. The plurality of return air straight pipes are communicated with a moisture exhaust pipe. A moisture exhaust port is formed on one side of the moisture exhaust pipe. A moisture exhaust air valve is arranged at the moisture exhaust port. The moisture exhaust port is located at a position close to the evaporator of the air source heat pump unit. The end of the moisture exhaust pipe is communicated with a fresh air device. The fresh air device is communicated with the air source heat pump unit through a blower.

[0016] Optionally, the fresh air device includes an air duct and a tee pipe. One end of the air duct is communicated with the air source heat pump unit through a blower, and the other end is connected with a tee pipe. One end of the tee pipe away from the air duct is communicated with the end of the moisture exhaust pipe through a main valve of the return air device. A fresh air inlet is formed on the tee pipe. A fresh air valve is arranged at the fresh air inlet. The fresh air valve, the main valve of the return air device, and the moisture exhaust air valve are respectively externally connected with an electric control device. During operation, the four-way pipe aggregates the waste heat of the drying exhaust gas of the three drying layers and then sequentially passes through other devices. The fresh air device is connected to a centrifugal fan, and the centrifugal fan is connected to the air source heat pump unit. The air path layout of the present invention adopts an internal and external double-circulation mode in each drying layer. The internal circulation can achieve cross-flow drying with controllable material temperature in each layer, providing reasonable heat and drying time for materials at different stages. The external circulation can be controlled by the opening degree of the air path valve to realize the utilization of waste heat of drying exhaust gas. The present invention is suitable for energy-saving continuous drying of heat-sensitive materials and materials with uniform drying requirements for moisture content.

[0017] Optionally, the air inlet device includes a 90° round pipe elbow. One end of the 90° round pipe elbow is communicated with the air source heat pump unit, and the other end is connected with an air inlet straight pipe through an air inlet valve. The air inlet straight pipe is communicated with the air path area.

[0018] Optionally, the discharging device includes a rotary air lock valve. The rotary air lock valve is arranged at the discharging port below the main body of the dryer. A discharging conveyor is arranged at the bottom of the rotary air lock valve.

[0019] Optionally, the rotary net belt transmission device includes a bearing seat bracket arranged on the main machine bracket. A sprocket is connected to the bearing seat bracket through a bearing. A chain net is arranged on the outer ring of the sprocket. The chain net is used for conveying materials. The sprocket located at one end of the chain net is drivingly connected with a driving motor device. The material changing plate includes a blanking plate obliquely arranged below the end of the chain net. The blanking plate can convey the materials at the end of the chain net to the head end of the chain net in the next drying layer. A side leakage prevention device is arranged outside the chain net.

[0020] Optionally, the anti-leakage device includes front and rear chain mesh baffles and side chain mesh baffles; the front and rear chain mesh baffles are symmetrically arranged at both ends of the chain mesh, and the front and rear chain mesh baffles are installed on the main machine bracket; the side chain mesh baffles are arranged on both sides of the chain mesh, and there is a gap between the side chain mesh baffles and the front and rear chain mesh baffles and the rotary net belt transmission device; a chain guide rail is fixedly arranged inside the inner side of the side chain mesh baffle, and the chain outside the chain mesh is movably arranged on the chain guide rail; a high-temperature resistant silica gel gasket is clamped by a fixture on the inner side of the top of the side chain mesh baffle, and the bottom of the high-temperature resistant silica gel gasket is attached to the top side of the chain mesh.

[0021] The present invention also provides a drying method based on the multi-heat-source multi-layer belt type heat pump drying device described above, including the following steps:

[0022] Step 1, the material enters the main body of the dryer through the feeding device, and the rotary net belt transmission device is driven by the transmission motor device to be conveyed between multiple drying zones;

[0023] Step 2, the air is preliminarily heated by the air source heat pump machine, is shunted to multiple air path zones by the air inlet device, and in the air path zone, the hot air is reheated to the set temperature by the axial flow fan and the secondary heating device, and then enters the drying zone through the opening of the air path partition for cross-flow drying. The dried exhaust gas reaches the position close to the air return device;

[0024] Step 3, a humidity threshold is set at the air return device. When the humidity is less than the threshold, both the moisture exhaust pipe and the fresh air device in the air return device are in a closed state. The dried exhaust gas passes through the opening on the air path partition at the end of the rotary net belt transmission device and returns to the air path zone to participate in the secondary temperature rise following the hot air heated by the air source heat pump machine, forming an in-layer circulation of the same layer; when the humidity of the dried exhaust gas is greater than the threshold, the moisture exhaust pipe and the fresh air device are opened. At this time, the dried exhaust gas is shunted at the end of the rotary net belt transmission device. Part of it passes through the opening on the air path partition and continues to participate in the in-layer circulation of the drying layer where it is located; the other part enters the air return device and is shunted again. Part of it is discharged from the moisture exhaust air valve, and the waste heat of the discharged dried exhaust gas is absorbed by the evaporator. The other part is mixed with the fresh air through the fresh air device and then re-enters the air source heat pump machine for heating, forming an external circulation;

[0025] Step 4, the dried material first falls onto the air lock of the discharging device, and the air lock transports the material to the discharging conveyor, and is taken out by the discharging conveyor.

[0026] The present invention has achieved the following technical effects compared with the prior art:

[0027] The materials of the present invention enter the main body of the dryer through the feeding device, are conveyed through the rotary mesh belt, and are taken out by the discharging device. The drying medium (air) is heated by the air source heat pump condenser under the action of the blower, and then is branched to each drying layer through the air inlet pipe. In the air duct area, after being heated twice by the axial flow fan and the secondary heating device, the hot air is heated to the set temperature and then enters the drying area for cross-flow drying. The heat-sensitive materials enter the dryer from the feeding device at the top and pass through the upper, middle, and lower drying areas in sequence. When the materials enter the upper drying area of the dryer, at this time, the moisture content of the materials is high, and a lower drying temperature can be set to reduce the thermal damage of the heat-sensitive components in the high-moisture environment caused by the drying temperature. After the materials and the drying air perform heat and moisture transfer, they enter the next drying area through the material-changing plate. After that, the moisture content of the materials decreases, and the thermal sensitivity of the active ingredients decreases. Then, the temperature can be set higher than that of the upper drying area. The materials move layer by layer from top to bottom, and the drying temperature increases layer by layer from top to bottom. This process can accelerate the transfer of moisture inside the materials to the drying air, which is beneficial to improving the drying rate in the falling-rate drying stage in the later stage of material drying. Under the controllable drying temperature, the higher the drying temperature, the faster the moisture loss of the materials. The present invention aims to utilize the different drying stages of the materials corresponding to each drying area of the belt dryer to realize the control of the air intake volume and drying temperature by the electric control device, reasonably allocate energy, reduce energy consumption, and improve the drying rate.

[0028] The present invention realizes the inner and outer double-cycle modes in each drying layer through a reasonable air duct layout. The inner cycle can provide reasonable heat and drying time for the materials at different stages, and realize cross-flow drying with controllable material temperature in each layer; the outer cycle is controlled by the opening degree of the valve in the air duct, and can realize the drying gas cycle and the utilization of waste heat. The present invention is suitable for the energy-saving continuous drying of heat-sensitive materials and materials with uniform drying requirements for moisture content. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0030] Figure 1 It is a schematic structural diagram of the multi-layer belt heat pump drying device and the air duct layout of the present invention;

[0031] Figure 2 It is a schematic internal structure diagram of the main body of the dryer of the present invention;

[0032] Figure 3 It is a schematic diagram of the inner cycle process of the present invention;

[0033] Figure 4 It is a schematic diagram of the cross-flow drying process of the present invention;

[0034] Figure 5 This is a schematic diagram of the external circulation process of the present invention;

[0035] Figure 6 This is a schematic diagram of the material movement direction of the present invention;

[0036] Figure 7 This is a schematic diagram of the structure of the axial flow fan inside the main body of the dryer of the present invention;

[0037] Figure 8 This is a schematic diagram of the structure of the electric heater inside the main body of the dryer of the present invention;

[0038] Figure 9 This is a schematic diagram of the fixture installation of the present invention.

[0039] In the figure: 1. Air source heat pump unit; 1-1. Blower; 1-2. Blower support; 2. Feeding device; 3. Discharging device; 3-1. Rotary air lock valve; 3-2. Discharge conveyor; 4. Driving motor device; 4-1. Motor support; 4-2. Motor backing plate; 4-3. Sprocket coupling; 4-4. Reducing motor; 5. Air inlet device; 5-1. 90° round pipe elbow; 5-2. Air inlet valve; 5-3. Air inlet straight pipe; 6. Return air device; 6-1. Return air straight pipe; 6-2. Four-way pipe; 6-3. Moisture exhaust pipe; 6-4. Moisture exhaust valve; 6-5. 90° square pipe elbow; 6-6. Main return air valve of the return air device; 6-7. Three-way pipe; 6-8. Fresh air valve; 6-9. Air duct; 7. Main body of the dryer; 7-1. Axial flow fan; 7-2. Secondary heating device; 7-3. Air duct partition; 7-4. Side baffle of the chain mesh; 7-5. Front and rear baffles of the chain mesh; 7-6. Material changing plate; 7-7. Bearing seat support; 7-8. Chain mesh; 7-9. Stratification partition; 7-10. Thermal insulation shell; 7-11. Main body support; 7-12. Fixture; 7-13. High-temperature silica gel gasket; 7-14. Chain guide rail; 8. Electric control device. Detailed implementation manners

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0041] The purpose of the present invention is to provide a multi-source multi-layer belt-type heat pump drying device and a drying method to solve the problems existing in the above-mentioned prior art and improve the waste heat utilization rate of a multi-layer belt-type dryer with an open-type heat pump as the heat source.

[0042] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Referring Figure 1 to Figure 2 and as shown in the figures, the present invention provides a multi-heat-source multi-layer belt-type heat pump drying device, which includes a dryer main body 7, inside which there are a plurality of mutually partitioned drying layers. In this embodiment, three drying layers are taken as an example for illustration. A rotary belt transmission device for conveying materials is provided in each drying layer. The adjacent two drying layers are connected by an inclined material-changing plate 7-6, and the rotary belt transmission devices in the adjacent two drying layers rotate in opposite directions; as Figure 6 shown, one end of the dryer main body 7 is provided with a feeding device 5 for conveying materials onto the rotary belt transmission device in the uppermost drying layer. The feeding device 5 can adopt a screw conveyor or other structures. In this embodiment, the feeding device 5 adopts a structure of a plurality of vertically arranged feeding sprockets. Feeding chains are arranged on the feeding sprockets, and a plurality of material frames are arranged on the feeding chains. The driving device drives the feeding sprockets to rotate, and then drives the material frames to rotate. When the material frame runs to the feeding port, it can hold materials. When the material frame carries the materials up to the inlet at the top of the dryer main body 7, the control end drives the material frame to turn over through a hydraulic rod, an electric rod, or other driving structures, and dumps the materials onto the rotary belt transmission device in the uppermost layer inside the dryer main body 7; The discharging device 3 includes a rotary air lock 3-1, and the rotary air lock 3-1 is arranged at the discharging port below the dryer main body 7. A discharging conveyor 3-2 is arranged at the bottom of the rotary air lock 3-1 for conveying the dried materials out; Each drying layer is separated by a partition into a drying area and an air duct area that are connected at both ends. The air source heat pump unit 1 is connected to the air duct areas of the three drying layers respectively through the air inlet device 5, and after passing through the axial flow fan 7-1 and the secondary heating device 7-2, hot air is conveyed into the drying layer. The air inlet device 5 includes a 90° circular pipe elbow 5-1. One end of the 90° circular pipe elbow 5-1 is connected to the air source heat pump unit 1, and the other end is connected to an air inlet straight pipe 5-3 through an air inlet valve 5-2. The air inlet straight pipe 5-3 is connected to the air duct area of the corresponding drying layer; The air return device 6 is arranged on the side far from the air inlet device 5 for discharging the drying waste gas in the drying layer, and part of the drying waste gas is discharged to the evaporator of the air source heat pump unit 1 to be absorbed by the evaporator for waste heat, and the other part of the drying waste gas is combined with fresh air after passing through the fresh air device and then re-enters the air source heat pump unit 1 for heating.

[0044] Further preferably, in order to achieve a better drying effect and avoid heat loss, the main body of the dryer 7 is provided with a heat-insulating outer shell 7-10. Inside the heat-insulating outer shell 7-10, there is a main body support 7-11. Adjacent drying layers are separated from each other by a layered partition board 7-9, so as to facilitate setting the hot air temperature in different drying layers and implementing the drying process in a targeted manner. In order to enable the hot air entering the drying layer to be reheated and achieve different heating temperatures in different drying layers, a vertically arranged air passage partition board 7-3 is provided in the drying layer. Each drying layer is divided into an air passage area and a drying area by the air passage partition board 7-3. Openings for connecting the air passage area and the drying area are provided at both ends of the air passage partition board 7-3; an axial flow fan 7-1 and a secondary heating device 7-2 are installed in the air passage area, as Figure 7 and Figure 8 shown, which is convenient for reheating the drying air to the set temperature. The rotary net belt transmission device is arranged in the drying area; axial flow fans 7-1 and secondary heating devices 7-2 are installed in the air passage areas of all three drying layers. The secondary heating device 7-2 is installed directly in front of the air outlet of the axial flow fan 7-1. The specific structure of the secondary heating device 7-2 is not limited and can adopt an electric heating device, or a biomass hot water heat exchanger, or a steam heat exchanger. The air source heat pump 1 is communicated with the air passage area through the air inlet device 5, and the air return device 6 is communicated with the drying area.

[0045] In order to realize the recovery and utilization of drying waste heat, the structure of the air return device 6 is uniquely designed in this embodiment. It adopts air return straight pipes 6-1 that are respectively communicated with the three drying areas. The three air return straight pipes 6-1 are communicated with a moisture discharge pipe 6-3 through a four-way pipe 6-2. A moisture discharge port is opened on one side of the moisture discharge pipe 6-3, and a moisture discharge air valve 6-4 is provided at the moisture discharge port. The moisture discharge port is located at a position close to the evaporator of the air source heat pump 1; the end of the moisture discharge pipe 6-3 is communicated with a fresh air device through a 90° square pipe elbow 6-5. The fresh air device is communicated with the air source heat pump 1 through a blower 1-1 arranged on the blower support 1-2.

[0046] Under the action of the axial flow fan 7-1, the materials in each drying layer and the drying air in the same layer undergo continuous cross-flow drying. The fresh air entering from the fresh air inlet and the part of the wet air flowing through the moisture exhaust pipe and the fresh air device are mixed, and then heated by heat exchange with the condenser of the air source heat pump 1 by the blower 1-1 to become dry air, which enters the air duct areas of each layer through the air inlet pipe. Under the action of the axial flow fan 7-1, after being further heated to the target drying temperature by the secondary heating device 7-2, it enters the front end of the drying area and performs cross-flow drying on the materials on the chain net 7-8, and then becomes nearly saturated wet air (waste gas). Part of the wet air enters the air duct area and is mixed with the dry air from the straight air inlet pipe 5-3, and continues to circulate through the axial flow fan 7-1 and the secondary heating device 7-2, and enters the front end of the drying area to participate in the material drying, forming an in-layer circulation. Another part of the wet air leaves the drying area through the return air pipe, part of it is discharged from the moisture exhaust port of the dryer, and part of it is mixed with the fresh air entering from the fresh air inlet through the fresh air device, and then heated by heat exchange with the condenser of the air source heat pump 1 by the blower 1-1 and enters the dryer to participate in the drying process, forming an out-of-layer circulation.

[0047] In the out-of-layer circulation, the moisture exhaust air valve 6-4 is arranged near the evaporator of the air source heat pump 1. The discharged hot and humid waste gas exchanges heat with the evaporator inlet. The heat absorbed by the working medium from the hot and humid waste gas and the environment is reheated at the condenser by the heat pump device to complete the recovery of part of the heat. The opening degree of the fresh air valve is the same as that of the moisture exhaust air valve 6-4 to ensure that the inhaled fresh air and the moisture exhaust air are equal in quantity. The fresh air and the waste heat of the dry exhaust gas that has not been discharged are mixed and then re-entered into the air source heat pump 1 for heating, and then diverted to each layer by the air inlet device 5 to form an out-of-layer circulation. The purpose of the present invention is to improve the utilization rate of drying heat and the drying uniformity through two circulation methods, and at the same time recycle the high-humidity air, that is, to achieve the purpose of reducing energy consumption.

[0048] In order to facilitate the supporting installation of the return air device 6, the fresh air device adopts an air duct 6-9. One end of the air duct 6-9 is connected to the air source heat pump 1 through the air supply fan 1-1 arranged on the air supply fan bracket 1-2, and the other end is connected to a three-way pipe 6-7. The end of the three-way pipe 6-7 away from the air duct 6-9 is connected to the end of the dehumidification pipe 6-3 through the return air device main valve 6-6. A fresh air inlet is opened on the three-way pipe 6-7, and a fresh air valve 6-8 is provided at the fresh air inlet; the fresh air valve 6-8, the return air device main valve 6-6 and the dehumidification air valve 6-4 are respectively connected to an electric control device 8. The electric control device 8 includes a controller for the feeding and discharging device, an air source heat pump controller, a controller for the electric heater of the dryer main unit, a transmission controller, and a frequency conversion controller for the reduction motor. The dryer main unit 7 is equipped with a temperature control valve, a temperature and humidity sensor and a controller, as well as a dehumidification air valve and a fresh air valve controller of the return air device 6. The control valves of the return air device 6 can be opened or closed according to the humidity and temperature values of the return air to realize internal circulation or external circulation. The discharging device 3 includes a fan 3-1 and a discharging conveyor 3-2. The fan 3-1 seals the discharging port to reduce the air from entering the dryer main unit from the discharging port during the discharging process, thereby reducing the heat energy loss. The temperature and humidity throttling control system composed of the temperature and humidity sensor, the temperature control valve, and the temperature and humidity controller realizes that the heat exchange time and the dehumidification and air supply speeds can be adjusted. During the dehumidification process, the waste heat of the drying exhaust gas is supplemented as a heat source to fully recover the heat energy, improve the heat exchange efficiency, and reduce the energy consumption of the system.

[0049] The specific structure of the rotary mesh belt transmission device of the present invention is not limited. It can be driven by a closed conveyor belt structure or a roller structure. In this embodiment, a chain net 7-8 structure composed of a chain and a mesh belt is adopted. The mesh belt is similar to a conveyor belt and is provided with fine and uniform mesh holes for conveying materials. The chain is connected to both sides of the mesh belt and is used to connect with the sprocket and the transmission device to achieve a transmission effect. Specifically, the rotary mesh belt transmission device includes a bearing seat bracket 7-7 arranged on the main frame bracket 7-11, and the bearing seat bracket 7-7 is provided on the bearing seat bracket 7-7. A sprocket is connected through a bearing, and a chain network 7-8 is provided on the outer ring of the sprocket. The chain network 7-8 is used to convey materials. The sprocket located at one end of the chain network 7-8 and connected to the chain network 7-8 is connected to a transmission motor device through a sprocket shaft transmission. Specifically, a reduction motor 4-4 of the transmission motor device is connected to the corresponding sprocket shaft transmission through a sprocket coupling 4-3. The reduction motor 4-4 is arranged on a motor pad 4-2, and the motor pad 4-2 is installed on a motor bracket 4-1. The motor bracket 4-1 is arranged on one side of the dryer main unit 7.

[0050] In order to enable the reciprocating conveyance of materials on different layers, in this embodiment, the material-changing plate 7-6 includes a blanking plate that is inclined and arranged diagonally below the end of the chain mesh. The blanking plate can convey the materials at the end of the chain mesh to the head end of the chain mesh 7-8 in the next drying layer. Specifically, the blanking plate includes a first blanking plate located above and a second blanking plate located below. The first blanking plate is installed on the side baffle 7-4 of the chain mesh and can adjust the placement angle to form a slope for material layer change. The second blanking plate is installed on the layered partition plate 7-9 and can also adjust the placement angle to ensure cooperation with the first blanking plate. There is a very small gap between the second blanking plate and the chain mesh 7-8 to prevent the materials from slipping out.

[0051] In order to avoid leakage and dropping of materials during the conveying process, a side leakage prevention device is provided outside the chain mesh 7-8. The side leakage prevention device includes front and rear chain mesh baffles 7-5 and side chain mesh baffles 7-4. Front and rear chain mesh baffles 7-5 are symmetrically arranged at both ends of the chain mesh 7-8, and the front and rear chain mesh baffles 7-5 are installed on the main machine bracket 7-11. Side chain mesh baffles 7-4 are provided on both sides of the chain mesh 7-8. There is a gap between the side chain mesh baffles 7-4 and the front and rear chain mesh baffles 7-5 and the rotary net belt transmission device. A chain guide rail 7-14 is fixedly provided inside the side chain mesh baffle 7-4, and the chain outside the chain mesh 7-8 is movably arranged on the chain guide rail 7-14. There is a certain gap between the side chain mesh baffle 7-4, the front and rear chain mesh baffles 7-5 and the rotary net belt transmission device, which not only ensures that the hot air heating area is similar to the material laying area but also facilitates the unobstructed passage of other moving parts. For example, Figure 9 As shown, a high-temperature resistant silicone gasket 7-13 is clamped by a fixture 7-12 on the side chain mesh baffle 7-4. The high-temperature resistant silicone gasket 7-13 has certain flexibility and wear resistance and can completely fit the chain mesh 7-8. When the chain mesh 7-8 moves, it automatically fits the chain mesh 7-8 to prevent side leakage of materials and improve the sealing effect. The fixture 7-12 is a stainless steel external hexagonal tiger clip with a hexagonal nut and a spring washer, which can clamp the high-temperature resistant silicone gasket 7-13 without moving along with the movement of the chain mesh 7-8.

[0052] The present invention also provides a drying method based on the above multi-heat-source multi-layer belt-type heat pump drying device, including:

[0053] Materials enter the dryer main body 7 through the feeding device 2, and the rotary net belt transmission device is driven by the transmission motor device 4 to convey between multiple drying zones.

[0054] Such as Figure 4As shown, air is preliminarily heated by the air source heat pump 1, and is split into three layers by the air inlet device 5. In the air duct area, it passes through the axial flow fan 7-1 and the secondary heating device 7-2, and the hot air is reheated to the set temperature and then passes through the air duct partition 7-3 for cross-flow drying. In this embodiment, the three drying layers are sequentially divided into the first temperature zone Ⅰ, the second temperature zone Ⅱ, and the third temperature zone Ⅲ from top to bottom, and the material drying process sequentially passes through the first temperature zone Ⅰ, the second temperature zone Ⅱ, and the third temperature zone Ⅲ. When the heat-sensitive material (such as agricultural products, etc.) enters the first temperature zone Ⅰ of the dryer main body 7, at this time the moisture content of the material is high, and a relatively low drying temperature such as 50°C can be set to reduce the thermal damage of the drying temperature to the heat-sensitive components in the high-moisture environment. After the material and the drying air perform heat and moisture transfer, it enters the second temperature zone Ⅱ of the next layer through the material changing plate 7-6. Thereafter, the moisture content of the material decreases, and the thermal sensitivity of the active ingredients decreases. The temperature can be set to 55°C, which is higher than the drying zone temperature of the upper layer.

[0055] When the material enters the third temperature zone Ⅲ, the material is already in the falling rate drying stage, because the drying rate at this stage is determined by the speed of moisture moving from the inside of the material to the surface. At this time, most of the free water in the material has been removed, and the material has a certain heat resistance. Short-time high-temperature drying can significantly improve the drying rate of the material. The temperature of the third temperature zone Ⅲ can be set equal to or higher than that of the second temperature zone Ⅱ (such as 60°C) to end the drying process.

[0056] As Figure 3 , Figure 4 As shown, the materials in each drying layer and the drying air in the same layer are continuously cross-flow dried under the action of the axial flow fan 7-1. The purpose of the present invention is to recycle and treat the drying exhaust gas of different layers, and cooperate with the humidity sensor and the electric control device 8 according to the humidity setting threshold at the confluence of the four-way pipe 6-2 in the air return device 6. When the humidity is less than the threshold, the moisture discharge device and the fresh air device in the air return device 6 are both in the closed state. The drying exhaust gas passes through the openings on the air duct partition 7-3 at the end of the rotary belt transmission device and returns to the air duct area to participate in the secondary heating following the hot air heated by the air source heat pump 1, forming an internal circulation.

[0057] As Figure 5As shown, when the humidity of the exhaust gas reaches the defined value (such as 95% relative humidity), the electronic control device 8 will open the main valves of the moisture exhaust device and the return air device 6-6. At this time, the dry exhaust gas is shunted at the end of the rotary belt drive device. One part passes through the openings on the air duct partition 7-3 and continues to participate in the in-layer circulation of the drying layer where it is located; the other part enters the four-way pipe 6-2 of the return air device 6. The four-way pipe 6-2 collects and recovers the waste heat of the dry exhaust gas from the three drying layers, and part of it is discharged from the opening of the moisture exhaust air valve 6-4. The opening of the moisture exhaust air valve 6-4 is near the evaporator of the air source heat pump 1. The waste heat of the discharged dry exhaust gas is absorbed and utilized by the evaporator, and the heat re-enters the main body of the dryer 7 through the air inlet device 5 to participate in the circulation. At the same time, the fresh air device and the centrifugal fan 1-1 are turned on. The opening degree of the fresh air valve 6-8 is the same as that of the moisture exhaust air valve 6-4 to ensure that the inhaled fresh air and the moisture exhaust air are equal in quantity. The fresh air is mixed with the waste heat of the dry exhaust gas that has not been discharged and re-enters the air source heat pump 1 for heating, and then is shunted to each layer by the air inlet device 5 to form an out-layer circulation.

[0058] The dried material first falls onto the rotary air lock 3-1 of the discharging device 3, and the rotary air lock 3-1 conveys the material onto the discharging conveyor 3-2, which then conveys the material out.

[0059] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "top", "bottom", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0060] In the present invention, specific examples are used to elaborate on the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A multi-source multi-layer belt-type heat pump drying device, characterized in that, Comprising: The main body of the dryer, inside which there are multiple mutually partitioned drying layers. Each drying layer is provided with a rotary belt drive device for conveying materials. The adjacent two drying layers are connected through an inclined material-changing plate, and the rotary belt drive devices in the adjacent two drying layers rotate in opposite directions; the same drying layer is partitioned into an air passage area and a drying area by a partition plate, and the front and rear ends of the air passage area and the drying area on the same layer are connected to form a circulation loop; an axial flow fan and a secondary heating device are provided in the air passage area; The feeding device, which is arranged at one end of the main body of the dryer and is used for conveying materials onto the rotary belt drive device in the uppermost drying layer; The discharging device, which is arranged below the other end of the main body of the dryer and is used for conveying the dried materials out; The air source heat pump unit, which is respectively connected to the air passage areas of multiple drying layers through an air inlet device and is used for conveying hot air into the drying layers; The air return device, which is arranged on the side far from the air inlet device. The air return device is connected to the drying area and is used for discharging the drying waste gas in the drying layer, and part of the drying waste gas is discharged to the evaporator of the air source heat pump unit to be absorbed by the evaporator for waste heat, and the other part of the drying waste gas is merged with fresh air after passing through the fresh air device and then re-enters the air source heat pump unit for heating.

2. The multi-heat-source multi-layer belt-type heat pump drying device according to claim 1, wherein The main body of the dryer includes a heat-insulating outer shell. Inside the heat-insulating outer shell, there is a main body support. The adjacent two drying layers are mutually partitioned by a layered partition plate, and the layered partition plate is arranged on the main body support.

3. The multi-source multi-layer belt type heat pump drying device according to claim 1, characterized in that, The partition plate in the drying layer is a vertically arranged air passage partition plate. The drying layer is partitioned into an air passage area and a drying area by the air passage partition plate. Openings for connecting the air passage area and the drying area are provided at both ends of the air passage partition plate; the rotary belt drive device is arranged in the drying area.

4. The multi-source multi-layer belt-type heat pump drying device according to claim 3, characterized in that The air return device includes air return straight pipes corresponding to and connected to multiple drying areas one by one. The multiple air return straight pipes are connected to a moisture exhaust pipe. A moisture exhaust port is opened on one side of the moisture exhaust pipe, and a moisture exhaust air valve is arranged at the moisture exhaust port. The moisture exhaust port is located at a position close to the evaporator of the air source heat pump unit; the end of the moisture exhaust pipe is connected to a fresh air device, and the fresh air device is connected to the air source heat pump unit through a blower.

5. The multi-heat-source multi-layer belt-type heat pump drying device according to claim 4, characterized in that, The fresh air device includes an air duct and a three-way pipe. One end of the air duct is connected to the air source heat pump unit through a blower, and the other end is connected to a three-way pipe. The end of the three-way pipe far from the air duct is connected to the end of the moisture exhaust pipe through a main air return device valve. A fresh air port is opened on the three-way pipe, and a fresh air air valve is arranged at the fresh air port; the fresh air air valve, the main air return device valve, and the moisture exhaust air valve are respectively externally connected to an electric control device.

6. The multi-source multi-layer belt type heat pump drying device according to claim 1, characterized in that The air inlet device includes a 90° round pipe elbow. One end of the 90° round pipe elbow is connected to the air source heat pump unit, and the other end is connected to an air inlet straight pipe through an air inlet air valve. The air inlet straight pipe is connected to the drying layer.

7. The multi-heat-source multi-layer belt type heat pump drying device according to claim 1, characterized in that, The discharging device includes a rotary air lock valve, and the rotary air lock valve is arranged at the discharging port below the main body of the dryer. A discharging conveyor is arranged at the bottom of the rotary air lock valve.

8. The multi-heat-source multi-layer belt-type heat pump drying device according to claim 2, characterized in that, The rotary net belt transmission device includes a bearing seat bracket arranged on the main machine bracket. A sprocket is connected to the bearing seat bracket through a bearing. A chain net is provided on the outer ring of the sprocket. The chain net is used for conveying materials. The sprocket located at one end of the chain net is drivingly connected to a driving motor device. The material changing plate includes a blanking plate inclined obliquely below the end of the chain net. The blanking plate can convey the materials at the end of the chain net to the head of the chain net in the next drying layer; A side leakage prevention device is provided outside the chain net.

9. The multi-heat-source multi-layer belt type heat pump drying device according to claim 8, characterized in that, The side leakage prevention device includes front and rear chain net baffles and side chain net baffles; The front and rear chain net baffles are symmetrically arranged at both ends of the chain net. The front and rear chain net baffles are installed on the main machine bracket; The side chain net baffles are provided on both sides of the chain net. There is a gap between the side chain net baffles and the front and rear chain net baffles and the rotary net belt transmission device; A chain guide rail is fixedly provided inside the side chain net baffle. The chain outside the chain net is movably arranged on the chain guide rail; A high-temperature resistant silica gel gasket is clamped inside the top of the side chain net baffle through a clamp. The bottom of the high-temperature resistant silica gel gasket is attached to the top side of the chain net.

10. A drying method for a multi-heat-source multi-layer belt-type heat pump drying device according to any one of claims 1 to 9, characterized in that, It includes the following steps: Step 1, the materials enter the main body of the dryer through the feeding device, and the rotary net belt transmission device is driven by the driving motor device to be conveyed between multiple drying zones; Step 2, the air is preliminarily heated by the air source heat pump machine, shunted to multiple air path zones by the air inlet device, and the hot air is reheated to the set temperature in the air path zone through the axial flow fan and the secondary heating device, and then passes through the opening of the air path partition for cross-flow drying. The dried exhaust gas reaches the position near the air return device; Step 3, a humidity threshold is set at the air return device. When the humidity is less than the threshold, the exhaust pipe and the fresh air device in the air return device are both in the closed state. The dried exhaust gas passes through the opening on the air path partition at the end of the rotary net belt transmission device and returns to the air path zone to participate in the secondary temperature rise following the hot air heated by the air source heat pump machine, forming an internal circulation of the same layer; When the humidity of the dried exhaust gas is greater than the threshold, the exhaust pipe and the fresh air device are opened. At this time, the dried exhaust gas is shunted at the end of the rotary net belt transmission device. Part of it passes through the opening on the air path partition and continues to participate in the internal circulation of the drying layer where it is located; The other part enters the air return device and is shunted again. Part of it is discharged from the exhaust air valve. The waste heat of the discharged dried exhaust gas is absorbed by the evaporator. The other part is mixed with the fresh air through the fresh air device and then re-enters the air source heat pump machine for heating, forming an external circulation; Step 4, the dried materials first fall onto the air lock of the discharging device, and the air lock transports the materials to the discharging conveyor, which then transports the materials out.

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