Hot air circulation drying system and drying method

Abstract

The invention discloses a hot air circulation drying system and method, and belongs to the technical field of wood drying, the hot air circulation drying system comprises a drying room, a drying support and a heat pump drying unit, an air supply pipe is laid on the ground in the drying room along the wall of the drying room, and an air feeder of the heat pump drying unit feeds air heated by a condenser into the drying room through the air supply pipe; a partition plate is arranged in the drying room to divide the drying room into an upper layer cavity and a lower layer cavity, at least one row of circulating fans arranged at equal intervals in the left-right direction is installed on the partition plate, and air return holes are evenly distributed in the circulating fans. And the drying bracket is vertically mounted, is placed in the lower-layer cavity and is used for vertically placing the slab. According to the hot air circulation drying system, the space utilization rate and the single-time drying amount are remarkably increased in the mode that the slabs are vertically placed, meanwhile, efficient airflow circulation is formed through reasonable layout of the circulating fan and the drying support, hot air is evenly distributed, the heat efficiency and the drying uniformity are improved, and therefore the production efficiency is greatly improved, energy is saved, and the production cost is reduced. The production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wood drying, and particularly relates to a hot air circulation drying system and a drying method for drying veneer sheets. Background Art

[0002] The veneer sheets used for architectural decoration and furniture production are thin sheets with a thickness between 1.5 - 3.0 mm cut from wood. The moisture content of the veneer sheets is very high, usually between 30 - 80%, and the moisture content of some woods is even as high as over 80%. Therefore, it must be dried before lamination. The drying of veneer sheets is an important process for making plywood and formwork.

[0003] The traditional drying method is to place the veneer sheets on a bracket for outdoor drying, but the natural drying process is very slow, seriously restricting the work progress and work efficiency. The most commonly used artificial drying method at present is to use a drying room for drying. During operation, the veneer sheets are laid flat and stacked on a rack with a certain gap between the sheets, and then the drying room is heated by circulating hot air to achieve the purpose of drying the veneer sheets. However, this flat stacking method has the following problems: 1. The flat laying of veneer sheets occupies a large amount of space, resulting in low space utilization rate and limited single - drying capacity; 2. The flat stacking blocks the air flow channels between the sheets, the rising channel of the hot air is not smooth, the thermal efficiency is low, and the air flow is difficult to be evenly distributed, causing uneven drying of the edge and middle parts of the veneer sheets, which not only affects the drying quality but also increases energy consumption. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the above problems, and provide a hot air circulation drying system, by reasonably designing the placement method of veneer sheets, the structural layout of the drying room and the air flow organization method, to improve the space utilization rate and single - drying capacity, and at the same time ensure that the hot air can be evenly distributed, improve the thermal efficiency and drying uniformity, so as to improve the production efficiency and save energy; at the same time, a drying method using the hot air circulation drying system is provided.

[0005] The technical solution of the present invention is as follows: A hot air circulation drying system includes a drying room, a drying bracket arranged in the drying room, and a heat pump drying unit arranged outside the drying room. The heat pump drying unit includes a compressor, an evaporator, a condenser and a blower. It is characterized in that: the evaporator and the condenser are respectively arranged in a first installation room and a second installation room, and the air inlet of the blower communicates with the second installation room; an air supply pipe is laid along the drying room wall on the ground in the drying room, and the air supply pipe has two air outlets respectively located at the front ends of the left and right side walls. The air outlet of the blower is connected to the air supply pipe through a pipeline for sending the air heated by the condenser into the drying room through the air supply pipe. A partition is provided inside the drying chamber to divide it into an upper cavity and a lower cavity. At least one row of circulation fans arranged at equal intervals in the left-right direction is installed on the partition, and the air outlets of the circulation fans face vertically downward; the partition is also evenly covered with air return holes. The drying bracket is a vertically installed drying bracket for vertically placing veneers. The drying brackets are placed in rows on the ground of the lower cavity of the drying chamber in the left-right direction. It further includes a control system, which is electrically connected to the heat pump drying unit and the circulation fans, and is used to control the operation of the heat pump drying unit and the circulation fans.

[0006] As an optimization, the above hot air circulation drying system further includes an electromagnetic heating device. The electromagnetic heating device includes a heating coil, a temperature sensor, and an electromagnetic heater connected to the heating coil. The pipeline after the air outlet of the air supply fan includes a heating pipe section adjacent to the air outlet of the air supply fan. The heating coil is wound outside the heating pipe section, and the temperature sensor is arranged inside the heating pipe section. The electromagnetic heater and the temperature sensor are respectively electrically connected to the control system. The control system controls the electromagnetic heater and the heating coil to work according to the temperature sensed by the temperature sensor to assist the heat pump drying unit in heating the air sent into the drying chamber.

[0007] As an optimization, in the above hot air circulation drying system, the drying bracket includes a receiving frame for vertically placing veneers and support feet connected under the receiving frame. The veneers in the receiving frame are placed perpendicular to the left-right direction. Several drying brackets are stacked vertically and aligned to form a stack. Horizontal air ducts are formed between the upper and lower drying brackets and between the bottom drying bracket and the ground; multiple rows of stacked drying brackets are arranged in the drying chamber, and an aisle is left directly below each row of circulation fans to form the air supply channel of the circulation fans.

[0008] As an optimization, in the above hot air circulation drying system, the circulation fans installed on the partition are in one row and located at the middle position in the front-rear direction of the drying chamber; or in two rows, respectively located at the front and rear of the drying chamber.

[0009] As an optimization, in the above hot air circulation drying system, an air door is provided below each circulation fan. The size of the air door can cover the installation position of the circulation fan, and the opening and closing of the air door are controlled by the control system.

[0010] As an optimization, in the above hot air circulation drying system, a dehumidification port is opened at the lower part of the rear wall of the drying chamber. A dehumidification fan is associated with the dehumidification port, and the dehumidification port is connected to the first installation chamber of the evaporator through a pipeline.

[0011] As an optimization, in the above hot air circulation drying system, the first installation chamber is communicated with the second installation chamber, and a draft fan is provided between the two installation chambers for guiding the dry air cooled and dehydrated by the evaporator in the first installation chamber into the second installation chamber.

[0012] As an optimization, in the above hot air circulation drying system, a dehumidification port communicating with the outside is opened in the middle of the rear wall of the drying chamber, and a dehumidification fan is associated with the dehumidification port.

[0013] As an optimization, in the above hot air circulation drying system, at least one moisture exhaust port communicating with the outside is opened in the upper part of the rear wall of the drying chamber, and a moisture exhaust fan is associated with the moisture exhaust port.

[0014] A hot air circulation drying method, characterized in that: the hot air circulation drying system according to any one of claims 1-5 is adopted, and a damper controlled to open and close by a control system is provided below each of the circulation fans; a dehumidification port connected to the evaporator through a pipeline is further provided on the rear wall of the drying chamber, and a dehumidification fan is configured; a dehumidification port communicating with the outside is provided in the middle of the rear wall, and a dehumidification fan is associated with the dehumidification port; a moisture exhaust port communicating with the outside is provided in the upper part of the rear wall, and a moisture exhaust fan is associated with the moisture exhaust port; the first installation chamber is communicated with the second installation chamber, and a draft fan is provided between the two installation chambers; The hot air circulation drying method includes the following steps: Step 1, vertically place the board skin to be dried in the drying bracket so that the board skin is perpendicular to the left and right directions, then stack the drying brackets vertically and align them, and stack them in rows on the ground of the lower cavity of the drying chamber in the left and right directions. An appropriate interval is reserved between each row of drying brackets, and an aisle is left directly below each row of circulation fans; Step 2, the control system controls the damper to open 5-10 seconds in advance, and then starts the compressor, air supply fan, circulation fan, dehumidification fan, dehumidification fan and moisture exhaust fan. The compressor transports the refrigerant to circulate between the evaporator and the condenser. The hot air heated by the condenser in the second installation chamber enters the air supply duct through the pipeline under the action of the air supply fan; At this time, the temperature sensor senses the temperature in the pipeline. When the hot air temperature in the pipeline does not reach the set temperature, the control system controls the electromagnetic heater to start working, and heats the inside of the pipeline through the heating coil; when the hot air temperature in the pipeline is higher than the set temperature, the control system controls the electromagnetic heater to stop working; The hot air is sent into the drying chamber from the air outlets on both sides through the air supply duct. The circulation fan blows air downward. The hot air diffuses through the horizontal air duct between the drying brackets and rises through the intervals between adjacent stacks and the gaps between the vertically placed board skins, and at the same time takes away the moisture in the wood, and then returns to the upper cavity through the return air holes on the partition board to form a hot air circulation to dry the board skin; Meanwhile, the dehumidifying fan extracts the hot and humid air in the drying chamber to the first installation chamber, where it is cooled, condensed, dehydrated and dehumidified by the evaporator. The dried air after dehumidification is introduced into the second installation chamber by the guiding fan, and then sent back to the drying chamber after being heated by the condenser. The dehumidifying fan adjusts the balance of the air volume flowing in and out of the drying chamber to keep the air intake greater than the air outlet. The moisture exhaust fan accelerates the discharge of the moisture in the upper space. During the drying process, when it is necessary to pause some or all of the circulation fans, the control system controls the corresponding circulation fans to pause operation and delays for 5 - 10 seconds to control the corresponding air doors to close. When it is necessary to restart the circulation fans, the corresponding air doors are controlled to open 5 - 10 seconds in advance. Step 3, the control system maintains the temperature of the drying chamber stable at 40°C - 50°C, and the hot air continuously circulates to take away the moisture in the board skin until the board skin reaches the set moisture content. Step 4, after the drying is completed, the control system controls the compressor and all the fans to stop running.

[0015] The beneficial effects of the present invention are as follows: 1. The hot air circulation drying system adopts the method of placing the board skin vertically, which significantly improves the space utilization rate and increases the single - time drying capacity. Through the reasonable layout of the circulation fans and drying brackets, an efficient air flow circulation path is formed, enabling the hot air to fully diffuse and evenly rise through the gaps between the vertically placed board skins to take away the moisture in the wood, reducing the air flow rising resistance, improving the thermal efficiency, ensuring the drying uniformity, thus greatly enhancing the production efficiency and drying effect, reducing energy waste and lowering the production cost.

[0016] 2. An electromagnetic heating device is set as an auxiliary heating unit of the heat pump drying unit, effectively making up for the disadvantage of the poor heating effect of the heat pump in low - temperature environments or high - load working conditions. At the same time, relying on its fast heating - up characteristic, it can rapidly increase the air temperature in the pipeline at the initial stage of system startup, thereby improving the overall heating capacity and working efficiency of the system.

[0017] 3. The air doors are set to effectively close the corresponding air flow channels when some of the circulation fans pause working, thereby optimizing the hot air circulation path in the drying chamber, preventing heat dissipation, improving the drying efficiency and reducing energy consumption.

[0018] 4. The drying chamber is provided with a dehumidification port. After the moisture in the drying chamber is extracted, it is cooled, condensed, dehydrated around the evaporator, thereby reducing the humidity in the drying chamber, improving the drying efficiency of the wood. At the same time, the waste heat of the discharged air is fully utilized to supply heat to the evaporator, improving the working efficiency of the heat pump drying unit and saving energy.

[0019] 5. A blower is provided between the installation chambers of the evaporator and the condenser to direct the dry air dehydrated by the evaporator to the condenser for heating and then re-introduce it into the drying chamber, realizing the reuse of the dried air after dehumidification. Compared with directly using outdoor air with higher humidity, it can significantly improve the drying efficiency and shorten the drying time.

[0020] 6. A dehumidification port is provided in the middle of the drying chamber, which can adjust the balance of the air volume entering and leaving the drying chamber to achieve the best drying efficiency.

[0021] 7. A moisture exhaust port is provided at the upper part of the drying chamber. Utilizing the characteristic that hot and humid air rises, it accelerates the discharge of high-humidity air, avoids moisture accumulation in the upper space, and speeds up the overall drying process. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of the hot air circulation drying system in Embodiment 1 of the present invention.

[0023] Figure 2 It is a top view layout diagram of the lower chamber of the drying chamber in Embodiment 1 of the present invention.

[0024] Figure 3 It is a schematic structural diagram of the partition in Embodiment 1 of the present invention.

[0025] Figure 4 It is a schematic structural diagram of the rear wall of the drying chamber in Embodiment 1 of the present invention.

[0026] Figure 5 It is a schematic structural diagram of the drying bracket in the embodiment of the present invention.

[0027] Figure 6 It is a schematic structural diagram of the integrated heating device in the embodiment of the present invention.

[0028] Figure 7 It is Figure 6 a top view schematic diagram of the connection between the integrated heating device and the drying chamber in

[0029] Figure 8 It is a top view layout diagram of the lower chamber of the drying chamber in Embodiment 2 of the present invention.

[0030] Figure 9 It is a schematic structural diagram of the partition in Embodiment 2 of the present invention.

[0031] In the figure: 1. drying chamber; 11. upper cavity; 12. lower cavity; 13. aisle; 2. drying bracket; 20. veneer; 21. receiving frame; 22. support feet; 3. heat pump drying unit; 31. compressor; 32. evaporator; 33. condenser; 34. air supply fan; 35. first installation room; 36. second installation room; 37. air guiding fan; 38. drain pipe; 4. air supply duct; 5. partition board; 51. circulation fan; 52. buckle plate; 53. return air hole; 6. dehumidification port; 61. dehumidification fan; 7. moisture extraction port; 71. moisture extraction fan; 8. moisture discharge port; 81. moisture discharge fan; 91. electromagnetic heater; 92. heating coil; 93. heating pipe section; 100. integrated heating device; 101. hot air outlet; 102. dehumidification air inlet; 103. drain outlet; 104. moisture extraction air inlet; 105. moisture extraction air outlet. Detailed implementation mode

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", "front", "rear", "lateral", "vertical", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or component referred to must have a specific orientation. Therefore, it should not be construed as a limitation to the present invention. Embodiment 1

[0033] As Figure 1 shown, a hot air circulation drying system provided in this embodiment includes a drying chamber 1, a drying bracket 2 arranged in the drying chamber 1, and a heat pump drying unit 3 arranged outside the drying chamber 1. In this embodiment, the internal dimensions of the drying chamber 1 are 7.5 meters in length from front to back, 7.5 meters in length from left to right, and 5.5 meters in height. The drying chamber 1 of this specification, in combination with the following structural design, can achieve large-batch and high-efficiency drying operations.

[0034] The heat pump drying unit 3 includes a compressor 31, an evaporator 32, a condenser 33, and an air supply fan 34. Its working principle is to use the compressor 31 to drive the refrigerant to circulate. The liquid refrigerant absorbs heat and evaporates into a gas in the evaporator 32, and then releases heat and condenses back into a liquid in the condenser 33, reciprocatingly circulating, so as to achieve the transfer of heat energy. This hot air circulation drying system uses the heat released in the condenser 33 to heat the drying chamber 1 to achieve the purpose of drying the veneer 20. Among them, the evaporator 32 and the condenser 33 are respectively arranged in the first installation room 35 and the second installation room 36, and the air inlet of the air supply fan 34 communicates with the second installation room 36.

[0035] As Figure 2As shown in the figure, an air supply duct 4 is laid along the wall of the drying chamber 1 on the ground inside the drying chamber 1. The air supply duct 4 is divided into a rear pipe section, a left pipe section, and a right pipe section, and is laid along the rear wall and the left and right side walls of the drying chamber 1. The left pipe section and the right pipe section of the air supply duct 4 extend to the front ends of the left and right side walls of the drying chamber 1 respectively, and air outlets are provided at their front ends. The distance between the left and right air outlets from the front wall of the drying chamber 1 is 20 - 30 cm. The air outlet of the air supply fan 34 is connected to the rear pipe section of the air supply duct 4 through a pipeline, and is used to send the air heated by the condenser 33 into the drying chamber 1 through the air supply duct 4.

[0036] In order to make up for the shortcoming that the heat pump drying unit 3 has poor heating effect in low-temperature environments or high-load working conditions, the hot air circulation drying system is provided with an electromagnetic heating device. The electromagnetic heating device includes a heating coil 92, a temperature sensor (not shown in the figure), and an electromagnetic heater 91 connected to the heating coil 92. The pipeline after the air outlet of the air supply fan 34 includes a heating pipe section 93 arranged adjacent to the air outlet of the air supply fan 34. The heating coil 92 is wound around the heating pipe section 93, and the temperature sensor is arranged inside the heating pipe section 93 to sense the hot air temperature inside the pipeline. When the hot air temperature inside the heating pipe section 93 is lower than the set temperature, the electromagnetic heater 91 and the heating coil 92 work to assist the heat pump drying unit 3 in heating the air sent into the drying chamber 1. In addition, the heating coil 92 is also wrapped with heat insulation cotton (not shown in the figure) to prevent heat from dissipating outward, reduce energy waste, and improve heating efficiency.

[0037] As Figure 3 As shown in the figure, a partition 5 is provided inside the drying chamber 1 to divide the drying chamber 1 into an upper cavity 11 and an upper cavity 12. At least one row of circulation fans 51 arranged at equal intervals in the left-right direction is installed on the partition 5. In this embodiment, the partition 5 is 4.2 meters away from the ground of the drying chamber 1, and the circulation fans 51 are in one row. This row of circulation fans 51 is arranged at equal intervals from one end to the other end of the partition 5 in the left-right direction and is located at the middle position in the front-rear direction of the drying chamber 1. The air outlets of the circulation fans 51 face vertically downward to form a downward air flow. A buckle plate 52 installation position for installing the circulation fans 51 is provided on the partition 5. Each circulation fan 51 is respectively installed on a buckle plate 52, and the buckle plate 52 is detachably buckled on the corresponding buckle plate 52 installation position for easy maintenance and replacement. An air door (not shown in the figure) is provided below each circulation fan 51. The size of the air door can cover the installation position of the circulation fan 51. When some of the circulation fans 51 stop working, closing the corresponding air doors can effectively seal the corresponding air flow channels to prevent heat loss. In addition, the partition 5 is also evenly covered with air return holes 53 for air return.

[0038] As Figure 5As shown in the figure, the drying bracket 2 is a vertically-mounted bracket for vertically placing veneers 20. The drying bracket 2 includes a receiving frame 21 for vertically placing veneers 20 and support feet 22 connected to the lower part of the receiving frame 21. The veneers 20 in the receiving frame 21 are placed perpendicular to the left-right direction. Specifically, the drying bracket 2 can adopt the veneer drying bracket disclosed in the Chinese patent with the publication number CN222027370U applied by the applicant. As Figure 1 and Figure 2 shown, several drying brackets 2 are stacked vertically and aligned in a stack. Horizontal air ducts are formed between the upper and lower drying brackets 2 and between the bottom drying bracket 2 and the ground. The stacked drying brackets 2 are placed in rows along the left-right direction on the ground of the upper cavity 12 of the drying room 1. Multiple rows of stacked drying brackets 2 are arranged in the drying room 1, and aisles 13 are left directly below each row of circulation fans 51, thereby forming the air supply channel of the circulation fans 51. In this embodiment, the size of the veneer 20 is 1.32 meters × 0.66 meters, and the thickness is 1.6 - 1.7 millimeters. The size of the drying bracket 2 is 2.2 meters in length × 1.5 meters in width × 1.35 meters in height (excluding the support feet 22). Each drying bracket 2 has two receiving frames 21 with the size of 2.1 meters in length × 0.66 meters in width × 1.35 meters in height. Approximately 1250 veneers 20 can be placed in each receiving frame 21. Every 3 drying brackets 2 are stacked vertically to form a stack, and 3 stacks are placed in one row. There are two rows in the front and back in the drying room 1, and an aisle 13 corresponding to the circulation fan 51 is left in the middle, with a total of 4 rows and 36 drying brackets 2 in total. Approximately 2500 veneers 20 can be placed in each drying bracket 2. Approximately 90,000 veneers 20, about 120 cubic meters, equivalent to the workload of about 4500 square meters of drying yard can be dried simultaneously in the entire drying room 1, greatly improving the land utilization rate.

[0039] As Figure 1 and Figure 4 shown, in order to reduce the humidity in the drying room 1 and improve the drying efficiency of wood, a dehumidification port 6 is opened at the lower part of the rear wall of the drying room 1. The dehumidification port 6 is connected to the first installation chamber 35 of the evaporator 32 through a pipeline, and a dehumidification fan 61 for driving air flow is associated with the dehumidification port 6. The moisture in the drying room 1 is extracted and then cooled and condensed around the evaporator 32 to achieve the purpose of dehumidification. At the same time, the waste heat of the discharged air is fully utilized to heat the evaporator 32, improving the working efficiency of the heat pump drying unit 3. In this embodiment, the dehumidification port 6 is 0.2 - 0.25 meters above the ground. The dehumidification fan 61 can be installed in the dehumidification port 6, or in the pipeline, or at the outlet of the pipeline, or at the air outlet of the first installation chamber 35 according to the actual situation. A drain pipe 38 is also connected to the first installation chamber 35. The water condensed during the dehumidification process is discharged through the drain pipe 38.

[0040] To adjust the balance of the air inflow and outflow in the drying chamber 1, a dehumidifying port 7 communicating with the outside is provided in the middle of the rear wall of the drying chamber 1. A dehumidifying fan 71 is associated with the dehumidifying port 7. By controlling the operation of the dehumidifying fan 71, the net air inflow can be controlled while dehumidifying, achieving the best drying efficiency. In this embodiment, the dehumidifying port 7 is 1.2 - 1.3 meters above the ground.

[0041] To avoid moisture accumulation in the upper space, at least one moisture exhaust port 8 communicating with the outside is provided in the upper part of the rear wall of the drying chamber 1. A moisture exhaust fan 81 is associated with the moisture exhaust port 8 to accelerate the discharge of high-humidity air and speed up the overall drying process. In this embodiment, the number of moisture exhaust ports 8 is 3. In this embodiment, the moisture exhaust port 8 is 5 meters above the ground.

[0042] To make full use of the dried air after dehumidification, the first installation chamber 35 and the second installation chamber 36 are in communication, and a guiding fan 37 is provided between the two installation chambers. The guiding fan 37 guides the dried air that has been cooled and dehumidified by the evaporator 32 in the first installation chamber 35 into the second installation chamber 36, and after being heated by the condenser 33, it is sent back into the drying chamber 1. Compared with directly using the outdoor air with higher humidity, the drying efficiency can be significantly improved and the drying time can be shortened.

[0043] This hot air circulation drying system is also provided with a control system (not shown in the figure). The control system is electrically connected to the heat pump drying unit 3, the electromagnetic heater 91, the temperature sensor, the circulation fan 51, the dehumidifying fan 61, the dehumidifying fan 71, the moisture exhaust fan 81, and the guiding fan 37, and is used to control the intelligent and efficient operation of the entire drying system. The opening and closing of the air damper are also controlled by the control system.

[0044] In specific implementation, such as Figure 6 and Figure 7As shown in the figure, the heat pump drying unit 3, the electromagnetic heating device, and the control system can be integrated into an integrated heating device 100. The dehumidification fan 61 and the moisture extraction fan 71 can also be integrated into this device. The device is provided with a hot air outlet 101, a dehumidification air inlet 102, a drain outlet 103, a moisture extraction air inlet 104, and a moisture extraction air outlet 105. The hot air outlet 101 is connected to the rear pipe section of the air supply pipe 4 in the drying chamber 1 through a pipeline. The dehumidification air inlet 102 and the drain outlet 103 are both arranged in the first installation chamber 35 of the evaporator 32. The dehumidification air inlet 102 is connected to the dehumidification port 6 of the drying chamber 1 through a pipeline. The dehumidification fan 61 is arranged between the first installation chamber 35 and the second installation chamber 36 in the same way as the guide fan 37. A drain pipe 38 is connected to the drain outlet 103. The moisture extraction air inlet 104 and the moisture extraction air outlet 105 are respectively connected to the air inlet and the air outlet of the moisture extraction fan 71. The moisture extraction air inlet 104 is connected to the moisture extraction port 7 of the drying chamber 1 through a pipeline, and the moisture extraction air outlet 105 is directly communicated with the outside. A display device and an input device (not shown in the figure) can also be arranged on the device to monitor and display the operating state of the drying system and input set parameters. Specifically, this device can adopt a wood drying device disclosed in a Chinese patent with the publication number CN210801849U applied by the applicant.

[0045] Based on the above hot air circulation drying system, the present invention also provides a hot air circulation drying method, including the following steps: Step 1: Vertically place the slab 20 to be dried in the drying bracket 2, make the slab 20 perpendicular to the left-right direction, then stack the drying brackets 2 vertically and stack them in piles, and stack them in rows on the ground of the upper cavity 12 of the drying chamber 1 along the left-right direction. An appropriate interval is reserved between each row of drying brackets 2, and an aisle 13 is left directly below each row of circulation fans 51. Step 2: The control system starts the compressor 31, the air supply fan 34, the circulation fan 51, and the dehumidification fan 61. The compressor 31 transports the refrigerant to circulate between the evaporator 32 and the condenser 33. The hot air heated by the condenser 33 in the second installation chamber 36 enters the air supply pipe 4 through the pipeline under the action of the air supply fan 34. At this time, the temperature sensor senses the temperature in the heating pipe section 93. When the hot air temperature in the heating pipe section 93 does not reach the set temperature, the control system controls the electromagnetic heater 91 to start working, and heats the inside of the heating pipe section 93 through the heating coil 92. When the hot air temperature in the heating pipe section 93 is higher than the set temperature, the control system controls the electromagnetic heater 91 to stop working. In this embodiment, it is necessary to make the hot air temperature in the heating pipe section 93 reach 110°C - 150°C.

[0046] Hot air is sent into the drying chamber 1 from the air outlets on both sides through the air supply duct 4. The circulating fan 51 blows air downward. The hot air diffuses through the horizontal air ducts between the drying brackets 2 and rises through the gaps between adjacent stacks and the gaps of the vertically placed board skins 20, taking away the moisture in the wood at the same time. Then it flows back to the upper cavity 11 through the air return holes 53 on the partition board 5 to form a hot air cycle, drying the board skins 20; Meanwhile, the dehumidifying fan 61 extracts the humid air in the drying chamber 1 to the first installation chamber 35, cools and condenses it through the evaporator 32 to remove moisture. The dehumidified dry air is introduced into the second installation chamber 36 through the air guiding fan 37, and is sent back into the drying chamber 1 after being heated by the condenser 33; The air extraction fan 71 effectively adjusts the balance of the air volume in and out of the drying chamber 1, keeping the air intake volume greater than the air outlet volume; The moisture exhaust fan 81 accelerates the discharge of the moisture in the upper space; During the drying process, when it is necessary to pause some or all of the circulating fans 51, the control system controls the corresponding circulating fans 51 to pause operation and delays for 5 - 10 seconds to control the corresponding air doors to close; When it is necessary to restart the circulating fans 51, the corresponding air doors are controlled to open 5 - 10 seconds in advance; Step 3, the control system maintains the temperature of the drying chamber 1 stable at 40°C - 50°C, and the hot air continuously circulates to take away the moisture in the board skins 20 until the board skins 20 reach the set moisture content; Step 4, after the drying is completed, the control system controls the compressor 31 and all the fans to stop running.

[0047] The hot air circulation drying system of this embodiment can dry about 90,000 board skins 20 at a time, and the cycle is about 7 - 10 days. Compared with the traditional drying yard, the hot air circulation drying system of the present invention has significant production efficiency advantages, low energy consumption, greatly reduced operating costs, and excellent economic benefits and environmental protection performance. Embodiment Two

[0048] This embodiment has basically the same structure as Embodiment One, the difference is that: as Figure 8 and Figure 9 shown, there are two rows of circulating fans 51 installed on the partition board 5, located at the front and rear of the drying chamber 1 respectively. An aisle 13 corresponding to the front circulating fan 51 is left between the drying bracket 2 in the front row in the drying chamber 1 and the front wall of the drying chamber 1, and an aisle 13 corresponding to the rear circulating fan 51 is left between the drying bracket 2 in the last row in the drying chamber 1 and the rear wall of the drying chamber 1. Setting two rows of circulating fans 51 in the front and rear can more flexibly selectively control the opening and closing of the front row circulating fan 51, the rear row circulating fan 51 or both rows of circulating fans 51 at the same time, so as to more precisely regulate the hot air distribution in each area of the drying chamber 1 according to the drying process requirements, which helps to improve the drying uniformity.

[0049] It will be understood that those of ordinary skill in the art can make various other corresponding changes and modifications according to the technical concept of the present invention, and all such changes and modifications should fall within the protection scope of the claims of the present invention.

Claims

1. A hot air circulation drying system, comprising a drying chamber, a drying bracket disposed in the drying chamber, and a heat pump drying unit disposed outside the drying chamber. The heat pump drying unit includes a compressor, an evaporator, a condenser, and a blower, and is characterized in that: The evaporator and the condenser are respectively arranged in the first installation chamber and the second installation chamber, and the air inlet of the air blower communicates with the second installation chamber; an air supply duct is laid along the inner wall of the drying chamber on the ground in the drying chamber, and the air supply duct has two air outlets respectively located at the front ends of the left and right side walls. The air outlet of the air blower is connected to the air supply duct through a pipeline, and is used to send the air heated by the condenser into the drying chamber through the air supply duct. A partition is arranged in the drying chamber to divide the drying chamber into an upper cavity and a lower cavity. At least one row of circulation fans arranged at equal intervals in the left-right direction is installed on the partition, and the air outlet of the circulation fan faces vertically downward; the partition is also evenly covered with air return holes. The drying bracket is a vertically installed drying bracket for vertically placing veneers. The drying brackets are placed in rows on the ground of the lower cavity of the drying chamber in the left-right direction. It further includes a control system, which is electrically connected to the heat pump drying unit and the circulation fan, and is used to control the operation of the heat pump drying unit and the circulation fan.

2. The hot air circulation drying system according to claim 1, characterized in that: It further includes an electromagnetic heating device. The electromagnetic heating device includes a heating coil, a temperature sensor, and an electromagnetic heater connected to the heating coil. The pipeline after the air outlet of the air blower includes a heating pipe section arranged adjacent to the air outlet of the air blower. The heating coil is wound outside the heating pipe section, and the temperature sensor is arranged inside the heating pipe section. The electromagnetic heater and the temperature sensor are respectively electrically connected to the control system. The control system controls the electromagnetic heater and the heating coil to work according to the temperature sensed by the temperature sensor, so as to assist the heat pump drying unit in heating the air sent into the drying chamber.

3. The hot air circulation drying system according to claim 2, wherein: The drying bracket includes a receiving frame for vertically placing veneers and support feet connected to the lower part of the receiving frame. The veneers in the receiving frame are placed perpendicular to the left-right direction. A number of drying brackets are stacked vertically and aligned to form a stack. Transverse air ducts are formed between the upper and lower drying brackets and between the bottom drying bracket and the ground; multiple rows of stacked drying brackets are arranged in the drying chamber, and aisles are left directly below each row of circulation fans to form the air supply channel of the circulation fans.

4. The hot air circulation drying system according to claim 2, characterized in that: The circulation fans installed on the partition are arranged in one row and located at the middle position in the front-rear direction of the drying chamber; or arranged in two rows and located at the front and rear parts of the drying chamber respectively.

5. The hot air circulation drying system according to claim 4, wherein: An air door is arranged below each circulation fan. The size of the air door can cover the installation position of the circulation fan, and the opening and closing of the air door are controlled by the control system.

6. The hot air circulation drying system according to claim 1, characterized in that: A dehumidification port is opened at the lower part of the rear wall of the drying chamber. A dehumidification fan is associated with the dehumidification port, and the dehumidification port is connected to the first installation chamber of the evaporator through a pipeline.

7. The hot air circulation drying system according to claim 6, characterized in that: The first installation chamber communicates with the second installation chamber, and a guiding fan is arranged between the two installation chambers for guiding the dry air cooled and dehydrated by the evaporator in the first installation chamber into the second installation chamber.

8. The hot air circulation drying system according to claim 1, characterized in that: A dehumidification port communicating with the outside is opened in the middle of the rear wall of the drying chamber. A dehumidification fan is associated with the dehumidification port.

9. The hot air circulation drying system according to claim 1, characterized in that: At least one moisture exhaust port communicating with the outside is opened at the upper part of the rear wall of the drying chamber. A moisture exhaust fan is associated with the moisture exhaust port.

10. A hot air circulation drying method, characterized in that: Adopt the hot air circulation drying system described in any one of claims 2-4, and a damper controlled by a control system to open and close is arranged below each of the circulation fans; a dehumidification port connected to the evaporator through a pipeline is further arranged on the rear wall of the drying chamber, and a dehumidification fan is configured; a dehumidification port communicating with the outside is arranged in the middle of the rear wall, and a dehumidification fan is associated with the dehumidification port; a moisture exhaust port communicating with the outside is arranged at the upper part of the rear wall, and a moisture exhaust fan is associated with the moisture exhaust port; the first installation chamber and the second installation chamber are communicated with each other, and a guiding fan is arranged between the two installation chambers; The hot air circulation drying method includes the following steps: Step 1, vertically place the board skin to be dried in the drying bracket, make the board skin perpendicular to the left-right direction, then stack the drying brackets vertically and align them into stacks, stack them row by row along the left-right direction on the ground of the lower cavity of the drying chamber, leave an appropriate interval between each row of drying brackets, and leave an aisle directly below each row of circulation fans; Step 2, the control system controls the damper to open 5-10 seconds in advance, and then starts the compressor, the air supply fan, the circulation fan, the dehumidification fan, the dehumidification extraction fan and the moisture exhaust fan. The compressor transports the refrigerant to circulate between the evaporator and the condenser. The hot air heated by the condenser in the second installation chamber enters the air supply pipe through the pipeline under the action of the air supply fan; At this time, the temperature sensor senses the temperature in the pipeline. When the hot air temperature in the pipeline does not reach the set temperature, the control system controls the electromagnetic heater to start working, and heats the inside of the pipeline through the heating coil; when the hot air temperature in the pipeline is higher than the set temperature, the control system controls the electromagnetic heater to stop working; The hot air is sent into the drying chamber from the air outlets on both sides through the air supply pipe, the circulation fan blows air downward, the hot air diffuses through the transverse air ducts between the drying brackets and rises through the intervals between adjacent row stacks and the gaps of the vertically placed board skin, and at the same time takes away the moisture in the wood, and then flows back to the upper cavity through the return air holes on the partition board to form a hot air circulation to dry the board skin; Meanwhile, the dehumidification fan extracts the humid hot air in the drying chamber to the first installation chamber, cools, condenses, dehydrates and dehumidifies it through the evaporator, and the dehumidified dry air is introduced into the second installation chamber through the guiding fan, and is reheated by the condenser and then sent back into the drying chamber; the dehumidification extraction fan adjusts the air volume balance of the drying chamber inlet and outlet to keep the inlet air volume greater than the outlet air volume; the moisture exhaust fan accelerates the discharge of moisture in the upper space; During the drying process, when it is necessary to pause some or all of the circulation fans, the control system controls the corresponding circulation fans to pause operation, and delays for 5-10 seconds to control the corresponding dampers to close; when it is necessary to restart the circulation fans, the corresponding dampers are controlled to open 5-10 seconds in advance; Step 3, the control system maintains the temperature of the drying chamber stable at 40°C - 50°C, and the hot air continuously circulates to take away the moisture in the board skin until the board skin reaches the set moisture content; Step 4, after the drying is completed, the control system controls the compressor and all the fans to stop running.

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