Multi-stage heat pump drying system and drying method

Abstract

The present invention relates to the technical field of heat pump drying, and particularly relates to a multi-stage heat pump drying system and a drying method. The multi-stage heat pump drying system includes: a main machine room, in which a plurality of heat pump units are arranged in parallel; a plurality of groups of drying units, which are connected to the same main machine room in parallel, and an air outlet and an air return opening are respectively provided at the connection between each group of drying units and the main machine room, and the air outlets and air return openings of each group are respectively arranged around each heat pump unit in a one-to-one correspondence; wherein, each group of drying units is provided with a feed door, and an internal circulation air flow can be formed between the air return opening, the feed door and the air outlet in the drying unit, and an external circulation air flow can be formed between the drying unit, the main machine room and the external environment. In the system of the present invention, multiple drying units share the same main machine room, which can not only ensure that the energy consumption distribution of the system is more uniform, but also can utilize the waste heat of other drying units for rapid compensation in case of insufficient waste heat in any drying unit, realizing the efficient utilization of waste heat at low ambient temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pump drying, and particularly to a multi-stage heat pump drying system and a drying method. Background Art

[0002] Drying is a major energy-consuming part of industrial energy consumption, accounting for up to about 15%. During the drying process, the heat pump system can recover the waste heat of the drying process, and it has the advantages of low energy consumption, high precision in temperature and humidity control, and high drying efficiency. Therefore, the heat pump drying technology has significant advantages in the drying field.

[0003] Currently, some heat pump drying devices usually use a parallel air supply method to dry materials, but a heat storage device is required to buffer the recovery and utilization of the waste heat in the drying process. In another part of the heat pump drying devices, based on the zone control of belt drying, different drying conditions are controlled for multiple heat pump drying units to realize the entire drying process. In the above drying processes, there are problems such as the discharge, recovery and utilization of waste heat at low ambient temperatures and uneven energy consumption distribution in the system, which result in relatively high overall energy consumption of the current heat pump drying system. Especially in the cold environment in winter in the north, the above problems cause low energy efficiency of the heat pump system in semi-open and open systems, and even inability to operate normally, and cause a reduction in the heat load of the heat pump, unable to meet the design requirements. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. For this purpose, the present invention provides a multi-stage heat pump drying system to solve the problems of low system performance, insufficient discharge, recovery and utilization of waste heat, and uneven energy consumption distribution in the existing heat pump drying devices at low ambient temperatures.

[0005] The present invention also provides a multi-stage heat pump drying method.

[0006] A multi-stage heat pump drying system according to an embodiment of the first aspect of the present invention includes:

[0007] A main machine room, in which a plurality of heat pump units are arranged in parallel;

[0008] A plurality of groups of drying units, which are connected to the same main machine room in parallel. An air outlet and an air return opening are respectively provided at the connection of each group of drying units and the main machine room. The air outlets and the air return openings of each group are respectively arranged around each heat pump unit in a one-to-one correspondence;

[0009] Wherein, an inlet door is provided on each group of drying units, and an internal circulating air flow can be formed in the drying unit between the air return opening, the inlet door and the air outlet, and an external circulating air flow can be formed among the drying unit, the main machine room and the external environment.

[0010] According to an embodiment of the present invention, the inside of the drying unit is partitioned into a heating chamber, a drying chamber, and a return air chamber. The heating chamber and the drying chamber are sequentially arranged between the feed door and the return air outlet, and the return air chamber is arranged between the feed door and the exhaust outlet. The return air chamber is respectively communicated with the heating chamber and the drying chamber.

[0011] According to an embodiment of the present invention, the drying unit includes an enclosed box body, a partition board, and a return air board. One end of the enclosed box body is connected to the main machine chamber through the partition board, and the other end of the enclosed box body is provided with the feed door. The return air board is placed inside the enclosed box body and is used to partition the inside of the enclosed box body into a vertically juxtaposed drying space and the return air chamber. In the drying space, the heating chamber and the drying chamber that are communicated with each other are sequentially arranged from the partition board to the feed door; one end of the return air board faces the partition board and there is a first air supply opening between the return air board and the partition board, and the other end of the return air board faces the feed door and there is a second air supply opening between the return air board and the feed door; both the return air outlet and the exhaust outlet are arranged on the partition board located in the return air chamber.

[0012] According to an embodiment of the present invention, a circulation fan and a condenser are arranged inside the drying unit. The circulation fan is horizontally placed at the connection position between the heating chamber and the drying chamber and is connected to the surface of the return air board facing away from the return air chamber, and the condenser is horizontally placed inside the heating chamber.

[0013] According to an embodiment of the present invention, the drying unit further includes an exhaust duct. The exhaust duct penetrates through the exhaust outlet. One end of the exhaust duct is located in the return air chamber, and the other end of the exhaust duct is located in the main machine chamber and on one side of the heat pump unit.

[0014] According to an embodiment of the present invention, an exhaust valve is installed at the end of the exhaust duct located in the main machine chamber.

[0015] According to an embodiment of the present invention, a fresh air inlet for communicating with the external environment is provided on the side wall of the return air chamber. The fresh air inlet is arranged facing the first air supply opening, and a fresh air valve is installed at the fresh air inlet.

[0016] According to an embodiment of the present invention, a return air valve is installed at the return air outlet.

[0017] According to an embodiment of the present invention, an openable inspection door is provided on the side wall of the main machine chamber, and a moisture exhaust port for communicating with the external environment is provided on the outer wall of the main machine chamber. A moisture exhaust valve is installed at the moisture exhaust port.

[0018] A multi - stage heat pump drying method according to an embodiment of the second aspect of the present invention is executed by the multi - stage heat pump drying system as described above; the multi - stage heat pump drying method executes a closed - loop drying operation mode, a semi - open drying operation mode, or a coupled drying operation mode;

[0019] In the closed - loop drying operation mode, the working parameters of each heat pump unit in the main machine room are adjusted to adjust the temperature in the corresponding drying unit; and, an internal circulation air flow is formed in the drying unit, and the dehumidification amount of the heat pump unit is adjusted by using the internal circulation air flow;

[0020] In the semi - open drying operation mode, the working parameters of each heat pump unit are adjusted to adjust the temperature in the corresponding drying unit; and, an external circulation air flow is formed among the drying unit, the main machine room, and the external environment, and the dehumidification amount of the heat pump unit is adjusted by using the external circulation air flow;

[0021] In the coupled drying operation mode, the working parameters of each heat pump unit are adjusted to adjust the temperature in the corresponding drying unit; and, the dehumidification amount of the heat pump unit is synchronously adjusted by using the internal circulation air flow and the external circulation air flow.

[0022] One or more of the above - mentioned technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0023] A multi - stage heat pump drying system according to an embodiment of the present invention includes: a main machine room, in which a plurality of heat pump units are arranged in parallel; a plurality of groups of drying units, which are connected to the same main machine room in parallel, and an air outlet and an air return opening are respectively provided at the connection between each group of drying units and the main machine room, and the air outlets and air return openings of each group are respectively arranged around each heat pump unit in one - to - one correspondence. The system of the present invention can connect a plurality of drying units in parallel to the same main machine room, so that a plurality of drying units share the same main machine room. Thus, when the waste heat of any drying unit is insufficient, the waste heat of other drying units can be used for compensation, realizing the sharing of waste heat sources of multiple drying units, that is, ensuring that each drying unit has waste heat available during the pre - heating stage of the system, and all drying units can make full use of waste heat during the drying process. This can not only improve the operating performance of the multi - stage heat pump drying system in the pre - heating stage under low - temperature environments (i.e., the "low ambient temperature" described in the present invention), improve the pre - heating efficiency and reduce the time required for the pre - heating stage, but also ensure that the distribution of system energy consumption is more uniform and realize the efficient utilization of waste heat in the system.

[0024] Further, in the multi-stage heat pump drying system according to the embodiment of the present invention, a feed door is provided on the drying unit, and an internal circulation air flow can be formed in the drying unit between the air return port, the feed door and the air discharge port, and an external circulation air flow can be formed between the drying unit, the main machine room and the external environment. The multi-stage heat pump drying system can implement a closed drying operation mode, a semi-open drying operation mode or a coupled drying operation mode. In the closed drying operation mode, the dehumidification amount of the heat pump unit is adjusted by using the internal circulation air flow. In the semi-open drying operation mode, the dehumidification amount of the heat pump unit is adjusted by using the external circulation air flow. And in the coupled drying operation mode, the dehumidification amount of the heat pump unit is synchronously adjusted by using the internal circulation air flow and the external circulation air flow, thereby greatly improving the operation performance of the multi-stage heat pump drying system, especially improving the operation performance of the system under low ambient temperature conditions, avoiding the adverse effects of the external environment on the heat pump performance, and achieving energy conservation and emission reduction.

[0025] Still further, in the multi-stage heat pump drying system according to the embodiment of the present invention, since multiple groups of drying units are arranged in parallel and are independent of each other, there will be no mutual interference between the drying units; and each drying unit can achieve independent drying requirements, for example, the control of the temperature, humidity and air flow velocity in the drying unit are all independent of each other. It can be seen that the multi-stage heat pump drying system can perform drying processing of different materials in different drying units, thereby further improving the system operation efficiency and reducing the production cost.

[0026] A multi-stage heat pump drying method according to an embodiment of the present invention includes a closed drying operation mode, a semi-open drying operation mode and a coupled drying operation mode; wherein, in the closed drying operation mode, the dehumidification amount of the heat pump unit is adjusted by using the internal circulation air flow, in the semi-open drying operation mode, the dehumidification amount of the heat pump unit is adjusted by using the external circulation air flow, and in the coupled drying operation mode, the dehumidification amount of the heat pump unit is synchronously adjusted by using the internal circulation air flow and the external circulation air flow. This method can reliably adjust the temperature and humidity in the main machine room under different modes, so that the system has better operation performance under low ambient temperature, improves the universality of the system operation, and prolongs the service life of the system.

[0027] Further, the multi-stage heat pump drying method is executed by the multi-stage heat pump drying system as described above, so that the multi-stage heat pump drying method has all the advantages of the above multi-stage heat pump drying system, which will not be elaborated here.

[0028] The additional aspects and advantages of the present invention will be given in part in the following description, will become apparent in part from the following description, or will be understood through the practice of the present invention. Description of the Drawings

[0029] 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 for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 is a top view structural schematic diagram of the multi-stage heat pump drying system according to the embodiment of the present invention;

[0031] Figure 2 is Figure 1 the structural schematic diagram in the A-A direction shown in

[0032] Reference numerals:

[0033] 1: heat pump unit; 2: condenser; 3: circulation fan; 4: return air plate; 5: exhaust duct; 51: first channel; 52: second channel; 6: exhaust valve; 7: return air valve; 8: fresh air valve; 9: moisture exhaust valve; 10: feed door; 11: inspection door; 12: heating chamber; 13: drying chamber; 14: main machine chamber; 15: return air chamber. Specific embodiments

[0034] The following will further describe in detail the embodiments of the present invention in conjunction with the drawings and embodiments. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0035] As Figure 1 and Figure 2 shown, the embodiment of the present invention provides a multi-stage heat pump drying system (abbreviated as "drying system" in the embodiment of the present invention). And based on this drying system, the embodiment of the present invention also provides a multi-stage heat pump drying method (abbreviated as "drying method" in the embodiment of the present invention).

[0036] As Figure 1 and Figure 2As shown in the figure, the drying system includes a main machine room 14 and several groups of drying units. The several groups of drying units share the same main machine room 14. Among them, several heat pump units 1 are arranged in parallel inside the main machine room 14. Preferably, the heat pump unit 1 is a heat pump device without a condenser 2, which is used to recover the latent heat and sensible heat in the waste gas. The several groups of drying units are connected to the same main machine room 14 in parallel. At the connection between each group of drying units and the main machine room 14, an air outlet and an air return port are respectively provided. The air outlet and the air return port of each group are respectively arranged around each heat pump unit 1 in one-to-one correspondence. Since each drying unit shares the main machine room 14, the waste heat air flow generated by any heat pump unit 1 can enter any drying unit through any air return port, but preferably enters the drying unit corresponding to the heat pump unit 1; the air outlet can send the air flow in the drying unit into the corresponding heat pump unit 1.

[0037] It can be seen that the drying system described in the embodiment of the present invention can connect multiple drying units in parallel to the same main machine room 14, so that multiple drying units share the same main machine room 14. Thus, in the case where the waste heat of any drying unit is insufficient, the waste heat of other drying units can be used to make up for it, realizing the sharing of waste heat sources of multiple drying units, that is, ensuring that each drying unit has waste heat available during the system preheating stage, and all drying units can make full use of waste heat during the drying process. This can not only improve the operating performance of the multi-stage heat pump drying system in the preheating stage under low temperature environment (i.e., the "low ambient temperature" described in the present invention), improve the preheating efficiency and reduce the time required for the preheating stage, but also ensure that the distribution of system energy consumption is more uniform, realizing the efficient utilization of waste heat in the system.

[0038] In the drying system described in the embodiment of the present invention, since multiple groups of drying units are arranged in parallel and are independent of each other, there will be no mutual interference between each drying unit; moreover, each drying unit can meet independent drying requirements, for example, the control of temperature, humidity, and air flow velocity in the drying unit is independent of each other. It can be seen that this multi-stage heat pump drying system can dry different materials in different drying units, thereby further improving the system operation efficiency and reducing the production cost.

[0039] In the drying system according to the embodiment of the present invention, a feed door 10 is respectively provided on each group of drying units, and materials enter the drying units through the feed door 10 for drying treatment. An internal circulation air flow can be formed among the air return port, the feed door 10 and the air discharge port in each group of drying units; an external circulation air flow can be respectively formed among each group of drying units, the main machine room 14 and the external environment. This drying system can execute a closed drying operation mode, a semi-open drying operation mode or a coupled drying operation mode. In the closed drying operation mode, the humidity of the main machine room 14 is adjusted by using the internal circulation air flow. In the semi-open drying operation mode, the humidity of the main machine room 14 is adjusted by using the external circulation air flow. In the coupled drying operation mode, the humidity of the main machine room 14 is synchronously adjusted by using the internal circulation air flow and the external circulation air flow, thereby greatly improving the operation performance of the multi-stage heat pump drying system, especially improving the system operation performance under low ambient temperature conditions, avoiding the adverse effects of the external environment on the heat pump performance, and achieving energy conservation and emission reduction.

[0040] It can be understood that the air flow direction of the internal circulation air flow described in the embodiment of the present invention is as follows: the air flow in the air return chamber 15 of the drying unit enters the main machine room 14 through the air discharge port, and is cooled and dehumidified by the heat pump unit 1; the cooled and dehumidified gas flows back into the drying unit through the air return port, and after sequentially passing through the heating chamber 12, the drying chamber 13 and the air return chamber 15, finally is discharged into the main machine room 14 again through the air discharge port.

[0041] It can be understood that the air flow direction of the external circulation air flow described in the embodiment of the present invention is as follows: on the one hand, the air flow of the external environment enters the drying unit, and in accordance with the flow direction of the internal circulation air flow in the drying unit, after sequentially passing through the heating chamber 12, the drying chamber 13 and the air return chamber 15, finally is discharged into the main machine room 14 through the air discharge port; on the other hand, the air flow in the air return chamber 15 of the drying unit enters the main machine room 14 through the air discharge port, and at the same time the air flow of the external environment enters the main machine room 14, and the air flow discharged from the air discharge port is jointly cooled and dehumidified by the heat pump unit 1, and the cooled and dehumidified gas is discharged from the main machine room 14 to the external environment.

[0042] It can be understood that in order to facilitate the control of the opening and closing, flow velocity and flow rate of the air flow, it is preferred that an air return valve 7 is installed at the air return port. In order to facilitate the rapid discharge of the air flow from the main machine room 14, it is preferred that a moisture discharge port for communicating with the external environment is provided on the outer wall of the main machine room 14, and a moisture discharge valve 9 is installed at the moisture discharge port. The moisture discharge valve 9 can discharge the air in the main machine room 14 to the external environment, and can adjust the flow velocity and flow rate of the gas. It is preferred that an openable inspection door 11 is provided on the side wall of the main machine room 14. The inspection door 11 can ensure the connection between the main machine room 14 and the external environment, ensure that a semi-open space can be formed in the main machine room 14 by opening the inspection door 11, and the inspection door 11 can also facilitate the maintenance of the heat pump unit 1.

[0043] In one embodiment, the drying unit is partitioned into a heating chamber 12, a drying chamber 13, and a return air chamber 15. The heating chamber 12 and the drying chamber 13 are sequentially constructed between the feed door 10 and the return air outlet, and the return air chamber 15 is constructed between the feed door 10 and the exhaust outlet. The return air chamber 15 is communicated with the heating chamber 12 and the drying chamber 13 respectively. The material enters the drying chamber 13 through the feed door 10 for drying treatment. As Figure 2 shown, an internal circulation air flow is formed inside the drying unit. Specifically, the air flow in the main machine chamber 14 enters the heating chamber 12, the drying chamber 13, and the return air chamber 15 in sequence through the return air outlet, and finally is discharged back into the main machine chamber 14 through the exhaust outlet.

[0044] In one embodiment, as Figure 2 shown, the drying unit includes a closed box body, a partition board, and a return air board 4. One end of the closed box body is connected to the main machine chamber 14 through the partition board, and the other end of the closed box body is provided with a feed door 10. The return air board 4 is placed inside the closed box body, and the return air board 4 is used to partition the inside of the closed box body into a drying space and a return air chamber 15 arranged vertically side by side, that is, as Figure 2 shown, the return air chamber 15 is located above the drying space. Inside the drying space, a heating chamber 12 and a drying chamber 13 that are connected in sequence are constructed from the partition board towards the feed door 10. One end of the return air board 4 faces the partition board and there is a first air supply opening between it and the partition board. The other end of the return air board 4 faces the feed door 10 and there is a second air supply opening between it and the feed door 10. The return air outlet and the exhaust outlet are both arranged on the partition board located inside the return air chamber 15. The internal circulation air flow enters the drying unit through the return air outlet, and without passing through the return air chamber 15, directly enters the heating chamber 12 through the first air supply opening from the return air chamber 15. The air flow flowing through the drying chamber 13 enters the return air chamber 15 through the second air supply opening, and after passing through the return air chamber 15, is discharged into the main machine chamber 14 through the exhaust outlet on the partition board. The above structure makes the internal structure of the drying unit compact, which is more conducive to structural optimization, simplifies the path of the drying air flow, and relatively prolongs the time for the air flow to pass through the drying chamber 13 and the return air chamber 15. On the one hand, the residence time of the air flow in the drying chamber 13 increases, enabling the waste heat carried in the air flow to be more fully utilized in the drying treatment of the material, improving the drying treatment efficiency and drying effect, and thus enhancing the system operation performance; on the other hand, the residence time of the air flow in the return air chamber 15 increases, enabling more air flow to be stored in the return air chamber 15, which is convenient for the drying system to more accurately and efficiently adjust the humidity in the main machine chamber 14 in the closed-loop drying operation mode and the coupled drying operation mode.

[0045] In one embodiment, a circulation fan 3 and a condenser 2 are provided in the drying unit. The circulation fan 3 is horizontally disposed at the connection position between the heating chamber 12 and the drying chamber 13 and is connected to the surface of the return air plate 4 facing away from the return air chamber 15. The circulation fan 3 is used to provide power for the internal circulation air flow. The condenser 2 is horizontally disposed in the heating chamber 12, and the condenser 2 is used to heat-treat the internal circulation air flow passing through it so that the internal circulation air flow can play a role in drying treatment in the drying chamber 13.

[0046] In one embodiment, the drying unit further includes an exhaust air duct 5. The exhaust air duct 5 is arranged through the exhaust air opening. One end of the exhaust air duct 5 is located in the return air chamber 15. Taking the air flow inhaled from the return air chamber 15 by the return air duct as the return air flow and the air flow entering the return air chamber 15 through the return air opening and passing through the first air supply opening as the exhaust air flow, preferably, the end of the exhaust air duct 5 located in the return air chamber 15 extends towards the feeding door 10 and exceeds the position of the first air supply opening, so that the return air flow and the exhaust air flow do not interfere with each other. The other end of the exhaust air duct 5 is located in the main machine chamber 14 and on one side of the heat pump unit 1 to ensure that the air flow discharged from the exhaust air duct 5 can act more directly on the heat pump unit 1 corresponding to the current drying unit.

[0047] Preferably, as Figure 2 shown, the exhaust air duct 5 includes a first channel 51 and a second channel 52. The connection part of the first channel 51 and the second channel 52 is arranged through the exhaust air opening. The first channel 51 is located in the return air chamber 15 and is attached to the surface of the return air plate 4, and the second channel 52 is located in the main machine chamber 14 and is attached to the surface of the partition board. The first channel 51 is used to separate the return air flow and the exhaust air flow in the return air chamber 15. The second channel 52 is used to optimize the pipeline structure design in the main machine chamber 14 and guide the exhaust air flow around the corresponding heat pump unit 1, so that the discharged air flow of each group of drying units can act more accurately on the corresponding heat pump unit 1 and improve the system operation efficiency.

[0048] It can be understood that in order to facilitate the regulation of the opening and closing, flow velocity and flow rate of the air flow, an exhaust air valve 6 is installed at the end of the exhaust air duct 5 located in the main machine chamber 14.

[0049] It can be understood that preferably, a fresh air inlet for communicating with the external environment is provided on the side wall of the return air chamber 15. The fresh air inlet is arranged towards the first air supply opening so that the fresh air can be more preferentially incorporated into the internal circulation air flow, making the operation process of the coupled drying operation mode smoother. Preferably, a fresh air valve 8 is installed at the fresh air inlet, and the fresh air valve 8 is used to introduce air flow from the external environment into the return air chamber 15 and can reliably regulate the opening and closing, flow velocity and flow rate of the air flow.

[0050] The drying method described in the embodiments of the present invention is executed by the above-mentioned multi-stage heat pump drying system. This drying method can execute a closed drying operation mode, a semi-open drying operation mode, or a coupled drying operation mode. This drying method can reliably adjust the dehumidification amount of the heat pump unit 1 in different modes, and can reliably adjust the temperature and humidity in the drying chamber 13 and the main engine chamber 14, so that the system has better operating performance in low ambient temperature, improves the universality of system operation, and extends the service life of the system.

[0051] In the closed drying operation mode, the working parameters of each heat pump unit 1 in the main engine chamber 14 are adjusted to adjust the temperature in the corresponding drying unit; and when the humidity in the main engine chamber 14 is lower than the set humidity standard value, an internal circulation air flow is formed in the drying unit, and the internal circulation air flow is used to adjust the dehumidification amount of the heat pump unit 1.

[0052] Specifically: during the drying process, the inspection doors 11 on both sides of the main engine chamber 14 are closed, and the fresh air valve 8 and the moisture exhaust valve 9 are in the closed state. When the temperature in the drying chamber 13 is lower than the set temperature value, the frequency of the compressor in the heat pump unit 1 is increased or the compressor is turned on to increase the temperature in the drying chamber 13; when the temperature in the drying chamber 13 meets the set temperature value, the current on state of the heat pump unit 1 is maintained; when the temperature in the drying chamber 13 is higher than the set temperature value, the frequency of the compressor in the heat pump unit 1 is decreased or the compressor is turned off. When the humidity in the main engine chamber 14 is relatively low compared to the set humidity value, the exhaust air valve 6 and the return air valve 7 are opened, the air in the return air chamber 15 is discharged into the main engine chamber 14, and after the air is cooled and dehumidified by the heat pump unit 1, it is discharged into the heating chamber 12 through the return air valve 7. By adjusting the opening degrees of the exhaust air valve 6 and the return air valve 7, the dehumidification amount of the heat pump unit 1 and the temperature in the main engine chamber 14 are controlled.

[0053] In the semi-open drying operation mode, the working parameters of each heat pump unit 1 are adjusted to adjust the temperature in the corresponding drying unit; and when the humidity in the drying unit is higher than the set humidity standard value, an external circulation air flow is formed among the drying unit, the main engine chamber 14 and the external environment, and the external circulation air flow is used to adjust the dehumidification amount of the heat pump unit 1.

[0054] Specifically: during the drying process, the inspection doors 11 on both sides of the main engine chamber 14 are in the open state, and the return air valve 7 is in the closed state. In the semi-open drying operation mode, the temperature control process of the drying chamber 13 is basically the same as that in the closed drying operation mode. For the specific control process, please refer to the part of the closed drying operation mode and will not be elaborated here; when the humidity in the drying chamber 13 is higher than the set humidity value, the fresh air valve 8, the exhaust air valve 6 and the moisture exhaust valve 9 are opened, the air in the return air chamber 15 is discharged into the main engine chamber 14 through the exhaust air duct 5 and the exhaust air valve 6, and the air discharged into the main engine chamber 14 is cooled and dehumidified by the heat pump unit 1, and then discharged into the environment through the moisture exhaust valve 9.

[0055] In the coupled drying operation mode, the operating parameters of each heat pump unit 1 are adjusted to regulate the temperature in the corresponding drying unit; and the dehumidification capacity of the heat pump unit 1 is synchronously regulated by using the internal circulation air flow and the external circulation air flow.

[0056] Specifically: The semi-open drying mode and the closed drying mode are coupled for operation. In the coupled drying operation mode, the temperature control process of the drying chamber 13 is basically the same as that of the semi-open drying mode and the closed drying mode. For the specific control process, please refer to the part of the closed drying operation mode and will not be elaborated here; in terms of humidity control, first, the opening degrees of the exhaust valve 6 and the return air valve 7 are adjusted to control the temperature of the main engine room 14 and the humidity of the drying chamber 13. When the regulation by relying on the exhaust valve 6 and the return air valve 7 cannot meet the humidity requirement of the drying chamber 13, the fresh air valve 8, the exhaust valve 6 and the moisture exhaust valve 9 are regulated.

[0057] It can be seen that in the drying method described in the embodiments of the present invention, the coupled drying operation mode can more effectively reduce the influence of external factors (such as low temperature environment) on the performance of the heat pump unit 1, and combines the control advantages of the semi-open drying mode and the closed drying mode.

[0058] It is understandable that this drying method is executed by the multi-stage heat pump drying system as described above, so that the multi-stage heat pump drying method also has all the advantages of the above multi-stage heat pump drying system and will not be elaborated here.

[0059] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of 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, and therefore cannot be understood as a limitation to the embodiments of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0060] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific situations.

[0061] In the embodiments of the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may mean that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the horizontal height of the first feature is less than that of the second feature.

[0062] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, without conflict, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0063] The above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that various combinations, modifications, or equivalent replacements of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and should all be covered by the scope of the claims of the present invention.

Claims

1. A multi-stage heat pump drying system, characterized in that, Comprising: A main machine room, in which a number of heat pump units are arranged in parallel; A number of groups of drying units, connected in parallel to the same main machine room, and an air outlet and an air return opening are respectively provided at the connection between each group of drying units and the main machine room, and the air outlets and the air return openings of each group are respectively arranged around each heat pump unit in a one-to-one correspondence; Wherein, each group of drying units is provided with a feeding door, and an internal circulation air flow can be formed between the air return opening, the feeding door and the air outlet in the drying unit, and an external circulation air flow can be formed between the drying unit, the main machine room and the external environment; The interior of the drying unit is divided into a heating chamber, a drying chamber and an air return chamber. The drying unit includes a closed box body, a partition board and an air return board. One end of the closed box body is connected to the main machine room through the partition board, and the other end of the closed box body is provided with the feeding door. The air return board is placed in the closed box body and is used to divide the interior of the closed box body into a drying space and the air return chamber which are arranged vertically in parallel. The heating chamber and the drying chamber which are connected in sequence are constructed in the drying space from the partition board to the feeding door; One end of the air return board faces the partition board and there is a first air supply opening between it and the partition board, and the other end of the air return board faces the feeding door and there is a second air supply opening between it and the feeding door; The air outlet and the air return opening are both arranged on the partition board located in the air return chamber; A circulation fan and a condenser are arranged in the drying unit. The circulation fan is horizontally arranged at the connection position between the heating chamber and the drying chamber and is connected to the surface of the air return board facing away from the air return chamber, and the condenser is horizontally arranged in the heating chamber; The drying unit further includes an exhaust air duct, the exhaust air duct penetrates through the air outlet, one end of the exhaust air duct is located in the air return chamber, and the other end of the exhaust air duct is located in the main machine room and on one side of the heat pump unit.

2. The multi-stage heat pump drying system according to claim 1, wherein The heating chamber and the drying chamber are sequentially constructed between the feeding door and the air return opening, the air return chamber is constructed between the feeding door and the air outlet, and the air return chamber is respectively communicated with the heating chamber and the drying chamber.

3. The multi-stage heat pump drying system according to claim 2, wherein An exhaust air valve is installed at the end of the exhaust air duct located in the main machine room.

4. The multi-stage heat pump drying system according to claim 2, wherein A fresh air inlet for communicating with the external environment is provided on the side wall of the air return chamber, the fresh air inlet is arranged facing the first air supply opening, and a fresh air valve is installed on the fresh air inlet.

5. The multi-stage heat pump drying system according to any one of claims 1 to 4, characterized in that, An air return valve is installed on the air return opening.

6. The multi-stage heat pump drying system according to any one of claims 1 to 4, characterized in that, A closable inspection door is provided on the side wall of the main machine room, and a moisture exhaust opening for communicating with the external environment is provided on the outer wall of the main machine room, and a moisture exhaust valve is installed on the moisture exhaust opening.

7. A multi-stage heat pump drying method, characterized in that, Executed by the multi-stage heat pump drying system according to any one of claims 1 to 6; The multi-stage heat pump drying method executes a closed drying operation mode, a semi-open drying operation mode or a coupled drying operation mode; In the closed drying operation mode, the working parameters of each heat pump unit in the main machine room are adjusted to adjust the temperature in the corresponding drying unit; And, an internal circulation air flow is formed in the drying unit, and the dehumidification amount of the heat pump unit is adjusted by using the internal circulation air flow; In the semi-open drying operation mode, the working parameters of each heat pump unit are adjusted to adjust the temperature in the corresponding drying unit; In addition, an external circulation air flow is formed among the drying unit, the main engine room and the external environment, and the dehumidification amount of the heat pump unit is adjusted by using the external circulation air flow; In the coupled drying operation mode, the working parameters of each heat pump unit are adjusted to adjust the temperature in the corresponding drying unit; In addition, the dehumidification amount of the heat pump unit is synchronously adjusted by using the internal circulation air flow and the external circulation air flow.

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