Energy-saving cascade heat pump all-in-one machine system and control method thereof

Abstract

The invention relates to the technical field of coating tail gas treatment equipment, in particular to an energy-saving cascade heat pump all-in-one machine system and a control method thereof.The all-in-one machine system comprises a plurality of heat pump devices, a plurality of circulating air devices, a circulating water tank, a circulating water heat exchanger, a cooling water tower, a circulating water pump and a temperature control device; the heat pump device comprises a first heat pump module and a second heat pump module which are connected to the circulating air device; the circulating air device comprises a circulating air pipeline connected to the drying oven, and the circulating air pipeline comprises an exhaust pipe section, a circulating pipe section and an air return pipe section; the first heat pump module is connected to the circulating pipe section, and the second heat pump module is connected to the air return pipe section; the first heat pump module and the second heat pump module are connected to the circulating water heat exchanger and the circulating water tank through circulating water pipes. The cooling water tower is connected to the circulating water pump and the circulating water heat exchanger through circulating water pipes. The circulating water tank and the circulating water pipe are used for heat collection and utilization, the energy utilization rate can be effectively increased, and the overall energy consumption of the coating machine production line is reduced.

Description

Technical Field

[0001] This application relates to the technical field of coating exhaust gas treatment equipment, and in particular to an energy-saving cascade heat pump integrated system and its control method. Background Technology

[0002] During the production process, coating machine ovens generate exhaust gases containing heat and impurities. These exhaust gases need to be treated by a tail gas treatment system for heat recovery before they can be returned or discharged. A typical coating machine tail gas treatment system includes several heat pump modules. The coating machine oven has several sections, with each section corresponding to one heat pump module. The exhaust gases generated by the coating oven are fed into the heat pump modules for heat recovery. The heat pump modules use the heat to heat the fresh or return air to achieve the purpose of thermal energy utilization.

[0003] However, during the operation of the coating machine, the operating temperature and high-temperature exhaust temperature of each oven section are different. Typically, the exhaust temperature of the ovens at the head and tail sections is low, while the exhaust temperature of the ovens in the middle section is high. The lower the exhaust temperature, the less energy is recovered by the heat pump module. The energy recovered by the heat pump modules at the head and tail sections is insufficient to heat the fresh air or recirculated return air to the required temperature of the oven, requiring additional energy to be supplemented through devices such as electricity, steam, or heat transfer oil. On the other hand, the heat pump modules in the middle section recover excess energy, which is used to heat the recirculated return air to the required temperature of the oven. The excess energy is discharged through the circulating liquid, resulting in a high overall energy consumption of the coating exhaust gas treatment equipment. Summary of the Invention

[0004] The purpose of this application is to provide an energy-saving cascade heat pump integrated system and its control method, which aims to improve the high overall energy consumption of coating exhaust gas treatment equipment in related technologies and improve the energy utilization rate of coating exhaust gas treatment equipment.

[0005] On one hand, this application provides an energy-saving cascade heat pump integrated system, including a plurality of heat pump devices, a plurality of circulating air devices, a circulating water tank, a circulating water heat exchanger, a cooling tower, a circulating water pump, and a temperature control device; the plurality of heat pump devices are arranged along the length of the oven, and each heat pump device includes a first heat pump module and a second heat pump module connected to the circulating air device; the circulating air device includes a circulating air duct connected to the oven and a waste heat recovery heat exchanger disposed in the circulating air duct, and the circulating air duct includes an exhaust pipe section, a circulating pipe section, and a return air pipe section; the first heat pump module is connected to the circulating pipe section, and the second heat pump module is connected to the return air pipe section; the circulating water tank is connected to a circulating water pipe, and the plurality of first heat pump modules and the plurality of second heat pump modules are all connected to the circulating water heat exchanger and the circulating water tank through the circulating water pipe; the cooling tower is connected to a cooling water pipe, and the cooling tower is connected to the circulating water pump and the circulating water heat exchanger through the cooling water pipe.

[0006] Furthermore, the first heat pump module includes a first evaporator disposed on the circulation pipe section, a first compressor connected to the first evaporator, a first condenser, and a first expansion valve, wherein the first condenser is disposed on the circulation water pipe.

[0007] Furthermore, the first heat pump module also includes an exhaust temperature control component, which includes an exhaust temperature sensor disposed on the circulation pipe section, an exhaust temperature controller electrically connected to the exhaust temperature sensor, and a first frequency converter, which is electrically connected to the first compressor.

[0008] Furthermore, the second heat pump module includes a second condenser disposed in the return air duct section, a second compressor connected to the second condenser, a second evaporator, and a second expansion valve, wherein the second evaporator is disposed in the circulating water pipe.

[0009] Furthermore, the second heat pump module also includes a return air temperature control component, which includes a return air temperature sensor disposed on the return air duct section, a return air temperature controller electrically connected to the return air temperature sensor, and a second frequency converter, which is electrically connected to the second compressor.

[0010] Furthermore, the circulating water tank is connected to a plurality of first condensers, a plurality of second evaporators, and a circulating water heat exchanger via the circulating water pipe.

[0011] Furthermore, the temperature control device is installed on the circulating water pump and the circulating water pipe. The temperature control device includes a water tank temperature sensor installed on the circulating water pipe, a water tank temperature controller electrically connected to the water tank temperature sensor, and a water pump frequency converter. The water pump frequency converter is electrically connected to the circulating water pump.

[0012] On the other hand, this application provides a control method applicable to the above-mentioned energy-saving cascade heat pump integrated system, comprising the following steps: S1: The exhaust gas from each oven section is fed into the corresponding heat pump devices; S2: Several heat pump devices, including a circulating air device, a first heat pump module, and a second heat pump module, work together with a temperature control device to circulate the gas. S3: The first heat pump unit monitors the exhaust air temperature and adjusts its parameters; the second heat pump unit monitors the return air temperature and adjusts its parameters. S4: The temperature control device monitors the circulating water temperature and adjusts its parameters; S5: Record exhaust air temperature, return air temperature, circulating water temperature, and the corresponding program design parameters.

[0013] Furthermore, the specific steps of S3 include: S3.1: Use a temperature sensor to monitor the exhaust temperature and compare it with the preset exhaust temperature value. If the deviation exceeds the set value range, increase or decrease the preset frequency value x of the first compressor until the deviation between the exhaust temperature and the preset exhaust temperature value is within the set value range. S3.2: Use a temperature sensor to monitor the return air temperature and compare it with the preset return air temperature value. If the deviation exceeds the set value range, increase or decrease the preset frequency value y of the second compressor until the deviation between the return air temperature and the preset return air temperature value is within the set value range.

[0014] Furthermore, the specific steps of S4 include: S4.1: Use a temperature sensor to monitor the water temperature in the circulating water pipe and compare it with the preset water temperature value. If the deviation exceeds the set value range, increase or decrease the preset value z of the circulating water pump frequency until the deviation between the water temperature in the circulating water pipe and the preset water temperature value is within the set value range.

[0015] The beneficial effects of this application are: 1. In the above-mentioned energy-saving cascade heat pump integrated system, the high-temperature gas generated during the operation of the coating machine oven enters the circulating air duct and the waste heat recovery heat exchanger. The high-temperature gas circulates through the exhaust pipe section, the circulating pipe section, and the return air pipe section. The high-temperature gas first recovers heat through the waste heat recovery heat exchanger and the first heat pump module. Several first heat pump modules are connected to the circulating water pipe, so that the heat recovered by the several first heat pump modules is collected through the circulating water pipe. Then, the circulating water pipe delivers the heat to the corresponding return air pipe section through the second heat pump module to heat the return air gas in the return air pipe section, thereby effectively recovering and utilizing the heat. The excess heat of the intermediate section oven can be used for the head section and tail section ovens, thereby improving the energy utilization rate and reducing the overall energy consumption of the coating machine production line.

[0016] 2. The control method of this application monitors the exhaust air temperature, return air temperature, and circulating water pipe temperature of the oven using temperature sensors, and adjusts the corresponding compressor and water pump frequencies according to the monitoring results to regulate the corresponding temperatures. This allows the integrated machine system to quickly and automatically reach the preset temperature value, thereby achieving a high energy utilization state. At the same time, by recording the current parameter values, the integrated machine can directly use these parameters to quickly adjust to a high energy utilization state when it needs to be started under the same operating conditions the next time. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of an energy-saving cascade heat pump integrated system provided in Embodiment 1 of this application; Figure 2 This is a schematic diagram of the heat pump device in Embodiment 1 of this application; Figure 3 This is a schematic diagram of the temperature control device in Embodiment 1 of this application; Figure 4 This is a schematic diagram of the steps of a control method provided in Embodiment 2 of this application.

[0018] Explanation of reference numerals in the attached figures: 1. Heat pump unit; 11. First heat pump module; 111. First evaporator; 112. First compressor; 113. First condenser; 114. First expansion valve; 115. Exhaust air temperature control assembly; 1151. Exhaust air temperature sensor; 1152. Exhaust air temperature controller; 1153. First frequency converter; 12. Second heat pump module; 121. Second condenser; 122. Second compressor; 123. Second evaporator; 124. Second expansion valve; 125. Return air temperature control assembly; 1251. Return air temperature sensor; 1 252. Return air temperature controller; 1253. Second frequency converter; 2. Circulating air device; 21. Circulating air duct; 211. Exhaust duct section; 212. Circulating duct section; 213. Return air duct section; 22. Waste heat recovery heat exchanger; 23. Demister; 24. Circulating fan; 25. Liquid receiving tray; 26. External exhaust valve; 3. Circulating water tank; 31. Circulating water pipe; 4. Circulating water heat exchanger; 5. Cooling tower; 6. Circulating water pump; 7. Temperature control device; 71. Water tank temperature sensor; 72. Water tank temperature controller; 73. Water pump frequency converter. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0020] It should be noted that although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0022] Example 1 Reference Figure 1 , Figure 2 as well as Figure 3On the one hand, this application provides an energy-saving cascade heat pump integrated system, including several heat pump devices 1, several circulating air devices 2, a circulating water tank 3, a circulating water heat exchanger 4, a cooling tower 5, a circulating water pump 6, and a temperature control device 7; the several heat pump devices 1 are arranged along the length of the oven, the oven has several sections, and each heat pump device 1 is installed corresponding to one section of the oven, and the several heat pump devices 1 are all connected to the circulating air devices 2. The several heat pump devices 1 and several circulating air devices 2 correspond one-to-one. When the integrated system is running, the high-temperature gas generated by the oven is passed into the corresponding heat pump device 1 and circulating air device 2. The heat pump device 1 recovers the heat of the high-temperature gas and then transports it to the circulating water pipe 31 for collection. The circulating water pipe 31 uses the collected heat to heat the return air or fresh air through the heat pump device 1, thereby effectively recovering and utilizing the heat. For example, the excess heat of the middle section oven can be used for the head section and tail section ovens, improving energy utilization and reducing the overall energy consumption of the coating machine production line.

[0023] Specifically, taking a single heat pump device 1 as an example, the heat pump device 1 includes a first heat pump module 11 and a second heat pump module 12 connected to the circulating air device 2. The circulating air device 2 is used to provide a circulating air path for high-temperature gas to cooperate with the first heat pump module 11 and the second heat pump module 12. The circulating air device 2 includes a circulating air duct 21 connected to the oven and a waste heat recovery heat exchanger 22 installed in the circulating air duct 21. The circulating air duct 21 includes an exhaust pipe section 211, a circulating pipe section 212, and a return air pipe section 213. The first heat pump module 11 is connected to the circulating pipe section 212, and the second heat pump module 12 is connected to the return air pipe section 213.

[0024] The exhaust duct section 211 is connected to the exhaust port of the oven and the waste heat recovery heat exchanger 22. The high-temperature gas generated by the oven is discharged from the exhaust port and enters the exhaust duct section 211. Then, the high-temperature gas enters the waste heat recovery heat exchanger 22, which recovers the heat of the high-temperature gas. During this process, the temperature of the high-temperature exhaust gas decreases and some impurities such as NMP and water are condensed and precipitated. Then, the high-temperature gas enters the circulation duct section 212. The first heat pump module 11 includes a first evaporator 111 disposed in the circulation duct section 212, a first compressor 112 connected to the first evaporator 111, a first condenser 113, and a first expansion valve 114. The first evaporator 111 is a low-temperature side evaporator, the first compressor 112 is a low-temperature compressor, the first condenser 113 is a low-temperature condenser, and the first expansion valve 114 is a low-temperature expansion valve.

[0025] The high-temperature gas enters the first evaporator 111 for secondary cooling, reducing the concentration of impurities such as NMP and water in the exhaust gas to below the specified concentration requirements. The heat released by the secondary cooling of the high-temperature exhaust gas in the first evaporator 111 is absorbed by the liquid refrigerant in the first evaporator 111, which evaporates and vaporizes into gaseous refrigerant. The gaseous refrigerant is compressed and heated by the first compressor 112. The heated refrigerant releases heat and condenses into liquid in the first condenser 113, and then passes through the first expansion valve 114 for throttling and depressurization before entering the first evaporator 111 to continue absorbing heat.

[0026] Meanwhile, the first heat pump module 11 also includes an exhaust temperature control component 115. The exhaust temperature control component 115 includes an exhaust temperature sensor 1151 installed in the circulation pipe section 212, an exhaust temperature controller 1152 electrically connected to the exhaust temperature sensor 1151, and a first frequency converter 1153. The first frequency converter 1153 is electrically connected to the first compressor 112. The exhaust temperature controller 1152 is a PID controller. By setting the exhaust temperature control component 115, the exhaust temperature sensor 1151 detects the exhaust temperature of the high-temperature exhaust gas and compares it with a program-set temperature value. Based on the comparison value, the exhaust temperature controller 1152 controls the frequency of the first compressor 112, thereby controlling the exhaust temperature of the high-temperature exhaust gas within the program-set value. The exhaust temperature sensor 1151, exhaust temperature controller 1152, first frequency converter 1153, and first compressor 112 are electrically connected via wires and signal lines, and all of these components are commercially available. Their principles and specific structures will not be elaborated further.

[0027] The circulating air device 2 also includes a demister 23, a circulating fan 24, several liquid receiving trays 25, and an exhaust valve 26, all installed in the circulating pipe section 212. In this embodiment, the first evaporator 111 is located between the demister 23 and the waste heat recovery heat exchanger 22. There are two liquid receiving trays 25, one located below the waste heat recovery heat exchanger 22 and the other located below the first evaporator 111. The exhaust valve 26 is located between the demister 23 and the waste heat recovery heat exchanger 22 and is connected to an external exhaust gas collection manifold. After the high-temperature exhaust gas, from which most impurities have been removed, is demisted by the demister 23 and pressurized by the circulating fan 24, most of it is reused as circulating return air, while a small portion enters the exhaust gas collection manifold through the exhaust valve 26 and is then uniformly sent to an external exhaust gas treatment device for further processing.

[0028] The second heat pump module 12 includes a second condenser 121 disposed in the return air duct section 213, a second compressor 122 connected to the second condenser 121, a second evaporator 123, and a second expansion valve 124. The second condenser 121 is a high-temperature condenser, the second compressor 122 is a high-temperature compressor, the second evaporator 123 is a high-temperature evaporator, and the second expansion valve 124 is a high-temperature expansion valve. The second heat pump module 12 also includes a return air temperature control component 125, which includes a return air temperature sensor 1251 disposed in the return air duct section 213, a return air temperature controller 1252 electrically connected to the return air temperature sensor 1251, and a second frequency converter 1253. The second frequency converter 1253 is electrically connected to the second compressor 122, and the return air temperature controller 1252 is a PID controller. The circulating water pipe 31 recovers the heat from the first heat pump module 11 and transfers it to the second heat pump module 12. The second heat pump module 12 heats the return air or fresh air, and the return air is heated to the specified temperature and then returned to the oven.

[0029] The circulating water tank 3 is connected to a circulating water pipe 31. Several first heat pump modules 11 and several second heat pump modules 12 are all installed on the circulating water pipe 31. That is, the first condenser 113 is installed on the circulating water pipe 31, and the second evaporator 123 is installed on the circulating water pipe 31. The several first heat pump modules 11 and several second heat pump modules 12 are all connected to the circulating water heat exchanger 4 and the circulating water tank 3 through the circulating water pipe 31. The cooling water tower 5 is connected to a cooling water pipe, and the cooling water tower 5 is connected to the circulating water pump 6 and the circulating water heat exchanger 4 through the cooling water pipe.

[0030] In this embodiment, the circulating water heat exchanger 4 is located between the second evaporator 123 and the circulating water tank 3. A temperature control device 7 is installed on the circulating water pipe 31. The temperature control device 7 is used to control the temperature of the circulating cooling water in the circulating water pipe 31. The circulating water pipe 31 is equipped with a water tank temperature control component. The temperature control device 7 includes a water tank temperature sensor 71 installed on the circulating water pipe 31, a water tank temperature controller 72 electrically connected to the water tank temperature sensor 71, and a water pump frequency converter 73. The water tank temperature controller 72 is a PID controller, and the water pump frequency converter 73 is electrically connected to the circulating water pump 6.

[0031] The heat released by the condensation of the low-temperature refrigerant in the first condenser 113 is absorbed by the circulating cooling water in the circulating water tank 3. Most of the heat is transferred to the second condenser 121 through the second evaporator 123 and the second compressor 122. The excess heat enters the cooling tower 5 through the circulating water heat exchanger 4. After heat exchange in the circulating water heat exchanger 4, the circulating cooling water returns to the circulating water tank 3. The temperature of the circulating cooling water returning to the circulating water tank 3 is detected by the water tank temperature sensor 71 and compared with the program-set temperature value. The frequency of the circulating water pump 6 is controlled by the water tank temperature controller 72 to control the temperature of the circulating cooling water returning to the water tank to the program-set value.

[0032] The heat released by the circulating cooling water in the second evaporator 123 is absorbed by the high-temperature refrigerant, which evaporates and vaporizes the liquid refrigerant into a gaseous state. This gaseous refrigerant is then compressed and heated by the second compressor 122, releasing heat and condensing into a liquid state in the second condenser 121. After passing through the second expansion valve 124 for throttling and pressure reduction, it enters the second evaporator 123 to continue absorbing heat. The heat released by the condensation in the second condenser 121 is used to heat the circulating return air to the required temperature of the coating machine oven.

[0033] A small portion of the recirculated return air enters the exhaust gas collection manifold through the external exhaust valve 26, while the remaining recirculated return air passes through the waste heat recovery heat exchanger 22 to absorb some of the heat from the high-temperature exhaust gas before entering the second condenser 121 to raise its temperature to the required temperature of the drying oven, thus drying the materials in the oven. The final temperature of the recirculated return air is detected by the return air temperature sensor 1251 and compared with the program-set temperature value. The return air temperature controller 1252 controls the frequency of the second compressor 122 to maintain the return air temperature of the high-temperature exhaust gas within the program-set value.

[0034] Example 2 Reference Figure 4 On the other hand, embodiments of this application provide a control method for the above-mentioned energy-saving cascade heat pump integrated system, comprising the following steps: S1: The exhaust gas from each section of the drying oven is introduced into the corresponding heat pump devices 1; Specifically, the exhaust gas from each oven enters the corresponding heat pump device 1 through the circulation pipe section 212, and the high-temperature exhaust gas will pass through the exhaust pipe section 211, the circulation pipe section 212, and the return air pipe section 213 in sequence.

[0035] S2: Several heat pump devices 1, corresponding to circulating air devices 2, first heat pump module 11 and second heat pump module 12, work together with temperature control device 7 to perform heat circulation of gas; Specifically, the high-temperature exhaust gas passes through the exhaust duct section 211, then through the waste heat recovery heat exchanger 22, and enters the circulation duct section 212. In the circulation duct section 212, the high-temperature exhaust gas undergoes cooling, demisting, and exhaust treatment, as well as heat recovery treatment via the first heat pump module 11. Subsequently, the high-temperature exhaust gas re-enters the waste heat recovery heat exchanger 22 for heating. After heating, the high-temperature exhaust gas enters the second heat pump module 12 in the return air duct section 213. The second heat pump module 12 heats the return air to a preset temperature before returning it to the drying oven to heat the materials. Simultaneously, the temperature control device 7 monitors and records the water temperature.

[0036] S3: The first heat pump unit 1 monitors the exhaust air temperature and adjusts its parameters; the second heat pump unit 1 monitors the return air temperature and adjusts its parameters. The specific steps of S3 include: S3.1: Monitoring the exhaust temperature using a temperature sensor and comparing it with a preset exhaust temperature value. If the deviation exceeds the set value range, increasing or decreasing the frequency x of the first compressor 112 until the deviation between the exhaust temperature and the preset exhaust temperature value is within the set value range. More specifically, if the exhaust temperature deviation exceeds the set value range, it is determined whether to increase or decrease the frequency of the first compressor 112, and then the frequency x of the first compressor 112 is increased or decreased, where frequency x is a preset value. Then, the exhaust temperature is acquired again and compared and adjusted with the preset exhaust temperature value until the deviation between the exhaust temperature and the preset exhaust temperature value is within the set value range.

[0037] S3.2: Monitor the return air temperature using a temperature sensor and compare it with a preset return air temperature value. If the deviation exceeds the set value range, increase or decrease the frequency y of the second compressor 122 until the deviation between the return air temperature and the preset return air temperature value is within the set value. More specifically, if the return air temperature deviation exceeds the set value range, determine whether to increase or decrease the frequency of the second compressor 122, and then increase or decrease the frequency y of the second compressor 122, where the frequency y is a preset value. Then, acquire the return air temperature again and compare and adjust it with the preset return air temperature value until the deviation between the return air temperature and the preset return air temperature value is within the set value range.

[0038] S4: Temperature control device 7 monitors the circulating water temperature and adjusts its parameters; The specific steps of S4 include: S4.1: Monitoring the circulating water temperature of the circulating water pipe 31 using a temperature sensor and comparing it with a preset circulating water temperature value. If the deviation exceeds the set value range, increasing or decreasing the frequency z of the circulating water pump 6 until the deviation between the water temperature of the circulating water pipe 31 and the preset water temperature value is within the set value range. More specifically, if the circulating cooling water temperature deviation exceeds the set value range, it is determined whether to increase or decrease the frequency of the circulating water pump 6, and then the frequency z of the circulating water pump 6 is increased or decreased. The frequency z is a preset value. Then, the circulating cooling water temperature is acquired again and compared and adjusted with the preset water temperature value until the deviation between the circulating cooling water temperature and the preset water temperature value is within the set value range.

[0039] S5: Record exhaust air temperature, return air temperature, circulating water temperature, and the corresponding program design parameters.

[0040] Specifically, once the integrated machine system stabilizes, it records the current operating conditions and adjusted parameter values. These parameters include the current frequency X of the first compressor 112, the current frequency Y of the second compressor 122, and the current frequency Z of the circulating water pump 6. By recording the current operating conditions and parameter values, the integrated machine can quickly adjust to a high energy efficiency state using the programmed parameters the next time it needs to be started under those conditions.

[0041] Exemplary embodiments of this disclosure have been specifically shown and described above. It should be understood that this disclosure is not limited to the detailed structures, arrangements, or implementations described herein; rather, this disclosure is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.

Claims

1. An energy-saving cascade heat pump integrated system, characterized in that, The oven includes several heat pump units (1), several circulating air units (2), a circulating water tank (3), a circulating water heat exchanger (4), a cooling tower (5), a circulating water pump (6), and a temperature control device (7); several of the heat pump units (1) are arranged along the length of the oven, and each heat pump unit (1) includes a first heat pump module (11) and a second heat pump module (12) connected to the circulating air unit (2); the circulating air unit (2) includes a circulating air duct (21) connected to the oven and a waste heat recovery heat exchanger (22) installed in the circulating air duct (21), and the circulating air duct (21) includes an exhaust pipe section (211) and a circulating air duct section (22). Pipe section (212) and return air pipe section (213); the first heat pump module (11) is connected to the circulating pipe section (212), and the second heat pump module (12) is connected to the return air pipe section (213); the circulating water tank (3) is connected to a circulating water pipe (31), and several of the first heat pump modules (11) and several of the second heat pump modules (12) are connected to the circulating water heat exchanger (4) and the circulating water tank (3) through the circulating water pipe (31); the cooling water tower (5) is connected to a cooling water pipe, and the cooling water tower (5) is connected to the circulating water pump (6) and the circulating water heat exchanger (4) through the cooling water pipe.

2. The energy-saving cascade heat pump integrated system according to claim 1, characterized in that, The first heat pump module (11) includes a first evaporator (111) disposed in the circulation pipe section (212), a first compressor (112) connected to the first evaporator (111), a first condenser (113) and a first expansion valve (114), wherein the first condenser (113) is disposed in the circulation water pipe (31).

3. The energy-saving cascade heat pump integrated system according to claim 2, characterized in that, The first heat pump module (11) further includes an exhaust temperature control component (115), which includes an exhaust temperature sensor (1151) disposed on the circulation pipe section (212), an exhaust temperature controller (1152) electrically connected to the exhaust temperature sensor (1151), and a first frequency converter (1153), which is electrically connected to the first compressor (112).

4. An energy-saving cascade heat pump integrated system according to claim 2 or 3, characterized in that, The second heat pump module (12) includes a second condenser (121) disposed in the return air duct section (213), a second compressor (122) connected to the second condenser (121), a second evaporator (123) and a second expansion valve (124), wherein the second evaporator (123) is disposed in the circulating water pipe (31).

5. The energy-saving cascade heat pump integrated system according to claim 4, characterized in that, The second heat pump module (12) further includes a return air temperature control component (125), which includes a return air temperature sensor (1251) disposed on the return air duct section (213), a return air temperature controller (1252) electrically connected to the return air temperature sensor (1251), and a second frequency converter (1253), which is electrically connected to the second compressor (122).

6. The energy-saving cascade heat pump integrated system according to claim 4, characterized in that, The circulating water tank (3) is connected to a plurality of first condensers (113), a plurality of second evaporators (123) and circulating water heat exchangers (4) via the circulating water pipe (31).

7. The energy-saving cascade heat pump integrated system according to claim 1, characterized in that, The temperature control device (7) is installed on the circulating water pump (6) and the circulating water pipe (31). The temperature control device (7) includes a water tank temperature sensor (71) installed on the circulating water pipe (31), a water tank temperature controller (72) electrically connected to the water tank temperature sensor (71), and a water pump frequency converter (73). The water pump frequency converter (73) is electrically connected to the circulating water pump (6).

8. A control method for an energy-saving cascade heat pump integrated system as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: The exhaust gas from each oven section is fed into the corresponding heat pump devices; S2: Several heat pump devices, including a circulating air device, a first heat pump module, and a second heat pump module, work together with a temperature control device to circulate the gas. S3: The first heat pump unit monitors the exhaust air temperature and adjusts its parameters; the second heat pump unit monitors the return air temperature and adjusts its parameters. S4: The temperature control device monitors the circulating water temperature and adjusts its parameters; S5: Record exhaust air temperature, return air temperature, circulating water temperature, and the corresponding program design parameters.

9. The control method according to claim 8, characterized in that, The specific steps of S3 include: S3.1: Use a temperature sensor to monitor the exhaust temperature and compare it with the preset exhaust temperature value. If the deviation exceeds the set value range, increase or decrease the preset frequency value x of the first compressor until the deviation between the exhaust temperature and the preset exhaust temperature value is within the set value range. S3.2: Use a temperature sensor to monitor the return air temperature and compare it with the preset return air temperature value. If the deviation exceeds the set value range, increase or decrease the preset frequency value y of the second compressor until the deviation between the return air temperature and the preset return air temperature value is within the set value range.

10. The control method according to claim 8, characterized in that, The specific steps of S4 include: S4.1: Use a temperature sensor to monitor the water temperature in the circulating water pipe and compare it with the preset water temperature value. If the deviation exceeds the set value range, increase or decrease the preset value z of the circulating water pump frequency until the deviation between the water temperature in the circulating water pipe and the preset water temperature value is within the set value range.

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