A two-stage coupled heat pump for comprehensive utilization of regenerative high temperature and its control method

Abstract

The present invention discloses a two-stage coupled heat pump for comprehensive utilization of regenerative heat at high temperature and its control method, which includes a first-stage heat pump, an intermediate buffer water circuit, and a second-stage heat pump arranged in sequence; the first-stage heat pump includes a first-stage evaporator, a first-stage waste heat recovery device, a first-stage compressor, a first-stage condenser, a first-stage expansion valve, and a refrigerant suitable for low-temperature evaporation used in the pipeline, which are connected by pipelines in sequence; the intermediate buffer water circuit includes a first-stage condensation water supply pipeline, a first-stage condensation water return pipeline, a buffer water tank, a second-stage evaporation water supply pipeline, a second-stage evaporation water return pipeline, a second-stage evaporation water supply pump, and a first-stage condensation water supply pump; the second-stage heat pump includes a second-stage compressor, a second-stage condenser, a second-stage expansion valve, a second-stage evaporator, a second-stage waste heat recovery device, and a refrigerant suitable for high-temperature condensation used in the pipeline, which are connected by pipelines in sequence. The present invention can operate in a low-temperature environment and can carry out waste heat recovery and valley electricity heat storage.

Description

Technical Field

[0001] The present invention relates to a two-stage coupled air source heat pump, and particularly to a heat storage type high-temperature comprehensive utilization two-stage coupled heat pump and its control method. Background Art

[0002] With the steady progress of carbon peak and carbon neutrality work, as the main industry of carbon emissions, energy conservation and emission reduction in the industrial field are extremely urgent. As an energy-efficient device, with the development of high-temperature refrigerants and high-temperature compressors, heat pumps will surely play a huge role in the energy conservation and emission reduction work in the industrial field. At present, in addition to the required high temperature, industrial heat pumps also face problems such as difficult operation in low-temperature environments, industrial waste heat recovery, wide range of waste heat temperatures, and utilization of valley electricity. Summary of the Invention

[0003] The purpose of the embodiments of the present invention is to address the defects of the above-mentioned existing technologies, and provide a heat storage type high-temperature comprehensive utilization two-stage coupled heat pump that can operate in low-temperature environments and can perform waste heat recovery and valley electricity heat storage.

[0004] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0005] A heat storage type high-temperature comprehensive utilization two-stage coupled heat pump includes a first-stage heat pump, an intermediate buffer water circuit, and a second-stage heat pump arranged in sequence;

[0006] The first-stage heat pump includes a first-stage evaporator. The outlet of the first-stage evaporator is connected to the inlet on one side of the first-stage condenser through a first-stage compressor. The outlet on one side of the first-stage condenser is connected to the inlet of the first-stage evaporator through a first-stage expansion valve. A first-stage evaporation fan is provided on the first-stage evaporator;

[0007] The intermediate buffer water circuit includes a buffer water tank. The outlet on one side of the buffer water tank is connected to the inlet on the other side of the first-stage condenser through a first-stage condensate supply pipeline. The outlet on the other side of the first-stage condenser is connected to the inlet on one side of the buffer water tank through a first-stage condensate return pipeline. A first-stage condensate supply pump is provided on the circulation pipeline connecting the buffer water tank and the first-stage condenser; The outlet on the other side of the buffer water tank is connected to the inlet on one side of the second-stage evaporator through a second-stage evaporation supply pipeline. The outlet on one side of the second-stage evaporator is connected to the inlet on the other side of the buffer water tank through a second-stage evaporation return pipeline. A second-stage evaporation supply pump is provided on the circulation pipeline connecting the buffer water tank and the second-stage evaporator;

[0008] The second-stage heat pump includes a second-stage condenser. The outlet of the second-stage condenser is connected to the inlet on the other side of the second-stage evaporator through a second-stage expansion valve. The outlet on the other side of the second-stage evaporator is connected to the inlet of the second-stage condenser through a second-stage compressor. A second-stage waste heat recovery device is provided on the circulation pipeline connecting the second-stage condenser and the second-stage evaporator.

[0009] Further, it also includes a primary waste heat recovery device, and the primary waste heat recovery device is connected to the pipeline between the primary evaporator and the primary compressor.

[0010] The secondary waste heat recovery device is arranged on the pipeline connecting the outlet on the other side of the secondary evaporator and the secondary compressor.

[0011] The primary condensate water supply pump is arranged on the primary condensate water supply pipeline.

[0012] The secondary evaporation water supply pump is arranged on the secondary evaporation water supply pipeline.

[0013] The primary waste heat recovery device is a water - fluorine heat exchanger, selected from shell - and - tube heat exchangers, plate heat exchangers or heat exchange tanks;

[0014] The secondary waste heat recovery device is a shell - and - tube heat exchanger, a plate heat exchanger, a heat exchange tank or a fin - type heat exchanger, and a secondary waste heat recovery fan is provided on the fin - type heat exchanger.

[0015] The secondary condenser is a shell - and - tube heat exchanger, a plate heat exchanger, a heat exchange tank or a fin - type heat exchanger, and a secondary condensation fan is provided on the fin - type heat exchanger.

[0016] A refrigerant suitable for low - temperature evaporation is provided in the circulation pipeline of the primary heat pump.

[0017] The refrigerant for low - temperature evaporation is selected from R410A, R404A or R32.

[0018] A refrigerant suitable for high - temperature condensation is provided in the circulation pipeline of the secondary heat pump.

[0019] The refrigerant for high - temperature condensation is selected from R515B, R134a or R245fa.

[0020] The present invention also provides a control method for the above - mentioned double - stage coupled heat pump, including the following steps:

[0021] When the temperature of the buffer water tank is lower than the set value, the primary heat pump operates, and at the same time, the primary condensate water pump is started. When the temperature of the buffer water tank is higher than the set value, the primary heat pump stops operating, and the primary condensate water pump is closed;

[0022] The secondary condenser is connected to the user - side pipeline. When the temperature in the user - side pipeline at the end does not reach the set temperature, the secondary heat pump operates, and the secondary evaporation water supply pump is turned on;

[0023] When the temperature of the high - temperature waste heat is above 25 °C, the heat of the high - temperature waste heat is recovered through the secondary waste heat recovery device;

[0024] When the heat of the recovered high-temperature waste heat is sufficient to meet the heat absorption of the secondary heat pump, that is, the refrigerant evaporation temperature at the outlet of the secondary waste heat recovery device reaches the set target value, the temperature of the intermediate buffer water circuit is maintained at 10-20°C at this time, and the secondary evaporation water supply pump is kept running;

[0025] When the heat of the recovered high-temperature waste heat is lower than the heat that the secondary heat pump needs to absorb, that is, the refrigerant evaporation temperature at the outlet of the secondary waste heat recovery device fails to reach the set target value, the primary heat pump is operated, the primary condensation water supply pump is turned on, the temperature of the intermediate buffer water circuit is raised above 25°C, the secondary evaporation water supply pump is turned on, the secondary heat pump is operated, the first-stage evaporation is carried out through the secondary evaporator, heat is absorbed from the intermediate buffer water circuit to supplement heat for the secondary heat pump, and then the second-stage evaporation is carried out through the secondary waste heat recovery device for waste heat recovery, so that the refrigerant evaporation temperature at the outlet of the secondary waste heat recovery device reaches the set value; when the temperature of the intermediate buffer water circuit is lower than the set value, the primary heat pump and the primary condensation water supply pump are operated to maintain the temperature of the intermediate buffer water circuit at the set value;

[0026] When both high-temperature waste heat and low-temperature waste heat need to be utilized, and the low-temperature waste heat is water, the primary heat pump and the secondary heat pump are operated, the primary condensation water supply pump and the secondary evaporation water supply pump are turned on. At this time, the low-temperature waste heat is recovered through the primary waste heat recovery device, and the heat is stored in the intermediate buffer water circuit, and the high-temperature waste heat is recovered through the secondary waste heat recovery device.

[0027] The beneficial effects brought by the technical solution provided by the embodiment of the present invention are:

[0028] In the present invention, a waste heat recovery device is added to each of the primary heat pump and the secondary heat pump, so that the low-temperature waste heat and high-temperature waste heat of the industry can be effectively recovered; in addition, the dual-stage coupled heat pump can overcome the inherent defect of too large pressure ratio when the evaporation temperature of the traditional heat pump is low and the condensation temperature is high through the cooperation of two groups of heat pumps with different refrigerants to achieve high-temperature heat supply; the primary heat pump can store heat in the buffer water tank during the valley electricity period. The present invention can operate in a low-temperature environment, can carry out waste heat recovery and valley electricity heat storage, and the energy is comprehensively utilized, saving energy and protecting the environment. Description of the Drawings

[0029] Figure 1 It is a schematic structural diagram of a dual-stage coupled heat pump for thermal high-low temperature comprehensive utilization provided by an embodiment of the present invention.

[0030] In the figure:

[0031] 1 - Primary heat pump, 11 - Primary compressor, 12 - Primary condenser, 13 - Primary expansion valve, 14 - Primary evaporator, 15 - Primary evaporation fan, 16 - Primary waste heat recovery device;

[0032] 2 - Intermediate buffer water circuit, 21 - Buffer water tank, 22 - Primary condensation return water pipeline, 23 - Primary condensation water supply pipeline, 24 - Primary condensation water supply pump, 25 - Secondary evaporation water supply pump, 26 - Secondary evaporation water supply pipeline, 27 - Secondary evaporation return water pipeline;

[0033] 3 - Secondary heat pump, 31 - Secondary compressor, 32 - Secondary condenser, 33 - Secondary condensation fan, 34 - Secondary expansion valve, 35 - Secondary evaporator, 36 - Secondary waste heat recovery fan, 37 - Secondary waste heat recovery device. Specific embodiments

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings.

[0035] See Figure 1 , a double - stage coupled heat pump for thermal storage and high - temperature comprehensive utilization, comprising a primary heat pump 1, an intermediate buffer water circuit 2, a secondary heat pump 3, and a user - side pipeline arranged in sequence;

[0036] The primary heat pump 1 includes a primary evaporator 14. The outlet of the primary evaporator 14 is connected to the inlet on one side of the primary condenser 12 through the primary compressor 11. The outlet on one side of the primary condenser 12 is connected to the inlet of the primary evaporator 14 through the primary expansion valve 13. The primary evaporator 14 is provided with a primary evaporation fan 15;

[0037] The intermediate buffer water circuit 12 includes a buffer water tank 21. The outlet on one side of the buffer water tank 21 is connected to the inlet on the other side of the primary condenser 12 through the primary condensation water supply pipeline 23. The outlet on the other side of the primary condenser 12 is connected to the inlet on one side of the buffer water tank 21 through the primary condensation return water pipeline 22. A primary condensation water supply pump 24 is provided on the circulation pipeline connecting the buffer water tank 21 and the primary condenser 12; The outlet on the other side of the buffer water tank 21 is connected to the inlet on one side of the secondary evaporator 35 through the secondary evaporation water supply pipeline 26. The outlet on one side of the secondary evaporator 35 is connected to the inlet on the other side of the buffer water tank 21 through the secondary evaporation return water pipeline 27. A secondary evaporation water supply pump 25 is provided on the circulation pipeline connecting the buffer water tank 21 and the secondary evaporator 35;

[0038] The secondary heat pump 3 includes a secondary condenser 32. The outlet on one side of the secondary condenser 32 is connected to the inlet on the other side of the secondary evaporator 35 through the secondary expansion valve 34. The outlet on the other side of the secondary evaporator 35 is connected to the inlet on one side of the secondary condenser 32 through the secondary compressor 31. A secondary waste heat recovery device 37 is provided on the circulation pipeline connecting the secondary condenser 32 and the secondary evaporator 35.

[0039] Preferably, a refrigerant suitable for low - temperature evaporation, such as R410A, R404A, or R32, etc., is provided in the circulation pipeline of the primary heat pump 1.

[0040] Preferably, a primary waste heat recovery device 16 is further included. The outlet of the primary evaporator 14 is connected to the inlet of the primary waste heat recovery device 16, and the outlet of the primary waste heat recovery device 16 is connected to the inlet on one side of the primary condenser 12 through a primary compressor 11.

[0041] The advantage of arranging the primary waste heat recovery device 16 in the present invention is that when the waste heat temperature is lower than 30°C, the waste heat is not suitable as the heat source of the high-temperature compressor at this time. The waste heat can be used as the heat source of the primary heat pump 1, effectively recovering its low-temperature heat, increasing the heating capacity of the primary heat pump 1, and saving energy. When the ambient temperature is lower than -15°C, when the dual-stage coupled heat pump of the present invention is operating, the heat absorbed by the primary evaporator 14 will be significantly reduced. At this time, the refrigerant passing through the primary evaporator 14 may not be completely evaporated and needs to be further evaporated through the primary waste heat recovery device 16. Through two evaporations, the heating capacity of the primary heat pump 1 is ensured, and at the same time, the risk of liquid hammer in the compressor is reduced.

[0042] The primary waste heat recovery device 16 of the present invention is preferably arranged on the pipeline connecting the outlet on the other side of the primary evaporator 14 and the primary compressor 11, rather than before the inlet on the other side of the primary evaporator 14. Because the ambient temperature varies greatly with seasons, when the ambient temperature is lower than the temperature of the low-temperature waste heat, it may evaporate in the primary waste heat recovery device 16 first, and a condensation process may occur in the primary evaporator 14, unable to absorb heat from the air but instead releasing heat to the air, resulting in a reduction in the heating capacity of the primary heat pump 1.

[0043] Preferably, the circulating pipeline of the secondary heat pump 3 is provided with a refrigerant suitable for high-temperature condensation, such as R515B, R134a, or R245fa, etc.

[0044] Preferably, the secondary waste heat recovery device 37 is arranged on the pipeline connecting the outlet on the other side of the secondary evaporator 35 and the secondary compressor 31.

[0045] Advantages of arranging the secondary waste heat recovery device 37 in the present invention: The secondary waste heat recovery device 37 can recover waste heat at a temperature above 30°C, achieving the purpose of reducing energy consumption and saving energy. When the heat of the high-temperature waste heat is sufficient to meet the heat absorption of the secondary heat pump 3, the temperature of the intermediate buffer water circuit 2 can be maintained at a relatively low temperature at this time. Only the secondary evaporation water supply pump 25 needs to be kept running to prevent the secondary evaporator 35 from freezing and icing. When the heat of the high-temperature waste heat is insufficient, lower than the heat that the secondary heat pump 3 needs to absorb. For example, the secondary heat pump needs to absorb 30 kW of heat, while the high-temperature waste heat recovered by the secondary waste heat recovery device 37 can only provide 15 kW of heat, which is not enough to support the 30 kW of heat absorbed by the secondary heat pump. At this time, the first-stage evaporation needs to be carried out through the secondary evaporator 35 to absorb 15 kW of heat from the intermediate buffer water circuit, and timely supplement heat for the secondary heat pump 3, so as to ensure that the secondary heat pump 3 can continuously and efficiently work. When the high-temperature waste heat is relatively sufficient, but still not enough for the 30 kW of heat that the secondary heat pump needs to absorb. For example, the high-temperature waste heat recovered by the secondary waste heat recovery device 37 can provide 27 kW of heat. At this time, the secondary evaporator 35 only needs to absorb 3 kW of heat from the intermediate buffer water circuit to supplement the heat absorption required by the secondary heat pump. The intermediate buffer water circuit 2 needs to provide 3 kW of heat for the secondary heat pump 3, that is, the heat that the primary heat pump 1 needs to provide for the intermediate buffer water circuit 2 is only 3 kW. The primary heat pump 1 can greatly reduce the operation time, thereby effectively saving energy.

[0046] If both high-temperature waste heat and low-temperature waste heat are available for utilization, and the low-temperature waste heat is water, the high-temperature waste heat is used as the heat source of the secondary heat pump 3, and waste heat recovery is carried out through the secondary waste heat recovery device 37. The low-temperature waste heat is used as the heat source of the primary heat pump 1, and waste heat recovery is carried out through the primary waste heat recovery device 16, and the heat is stored in the intermediate buffer water circuit 2. When the low-temperature waste heat is air, waste heat recovery can be directly carried out through the primary evaporator 14, and there is no need to add a primary waste heat recovery device 16.

[0047] The secondary waste heat recovery device 37 of the present invention is preferably arranged on the pipeline connecting the outlet on the other side of the secondary evaporator 35 and the secondary compressor 31, and is not arranged before the inlet on the other side of the secondary evaporator 35. Because the lower the temperature in the intermediate buffer water circuit, the more energy-saving. If the secondary waste heat recovery device 37 is arranged before the inlet on the other side of the secondary evaporator 35, it may cause the condensation process of the secondary evaporator 35. Condensation will release heat to the intermediate buffer water circuit, and the effect of absorbing heat from the intermediate buffer water circuit cannot be achieved, resulting in the inability to further reduce the temperature of the intermediate buffer water circuit and the deterioration of the energy-saving effect.

[0048] In addition, after the high-temperature waste heat is recovered by the secondary waste heat recovery device 37, its temperature will decrease, but the heat it contains still has utilizable value and can be used as the heat source of the primary waste heat recovery device 16 for waste heat recovery again. The secondary waste heat recovery device 37 and one side of the primary waste heat recovery device 16 are connected through a pipeline.

[0049] Preferably, the primary condensate supply pump 24 is arranged on the primary condensate supply pipeline 23.

[0050] Preferably, the secondary evaporation supply pump 25 is arranged on the secondary evaporation supply pipeline 26.

[0051] Preferably, the secondary waste heat recovery device 37 is a finned heat exchanger, and a secondary waste heat recovery fan 36 is arranged on the finned heat exchanger.

[0052] The primary heat pump 1 of the present invention includes a primary evaporator 14, a primary waste heat recovery device 16, a primary compressor 11, a primary condenser 12, a primary expansion valve 13, and a refrigerant suitable for low-temperature evaporation used in the pipeline, which are connected in sequence through a pipeline;

[0053] The intermediate buffer water circuit 2 includes a primary condensate supply pipeline 23, a primary condensate return pipeline 22, a buffer water tank 21, a secondary evaporation supply pipeline 26, a secondary evaporation return pipeline 27, a secondary evaporation supply pump 25, and a primary condensate supply pump 24;

[0054] The secondary heat pump 3 includes a secondary compressor 31, a secondary condenser, a secondary expansion valve 34, a secondary evaporator 35, a secondary waste heat recovery device 37, and a refrigerant suitable for high-temperature condensation used in the pipeline, which are connected in sequence through a pipeline.

[0055] By adding a waste heat recovery device to each of the primary heat pump and the secondary heat pump, the present invention can effectively recover the high- and low-temperature waste heat in industry; in addition, the two-stage coupled heat pump can overcome the defect of excessive pressure ratio when the evaporation temperature of the traditional heat pump is low and the condensation temperature is high by using two groups of heat pumps with different refrigerants to achieve high-temperature heating; the primary heat pump 1 of the present invention can store heat in the buffer water tank 21 during the valley electricity period for the secondary heat pump 3 to use during the peak electricity period.

[0056] The waste heat of the present invention can be the heat contained in the industrial exhaust gas and wastewater. The high-temperature waste heat refers to the heat contained in the exhaust gas or wastewater with a temperature greater than 25°C, including 25°C here, and the low-temperature waste heat refers to the heat contained in the exhaust gas or wastewater with a temperature less than 25°C.

[0057] When the industrial waste heat is wastewater, the primary waste heat recovery device 16 and the secondary waste heat recovery device 37 can be selected from equipment such as shell-and-tube heat exchangers, plate heat exchangers, and high-efficiency heat exchange tanks, and there is no need to add a secondary waste heat recovery fan 36.

[0058] Preferably, when water is used on the utilization side, the secondary condenser 32 is selected from equipment such as shell-and-tube heat exchangers, plate heat exchangers, and high-efficiency heat exchange tanks. There is no need to add a secondary condensation fan 33. The utilization-side pipeline includes a water supply pipeline and a return water pipeline (not shown in the figure). The water supply pipeline is connected to the inlet on the other side of the secondary condenser 32, and the return water pipeline is connected to the outlet on the other side of the secondary condenser 32. When hot air is required on the utilization side, the secondary condenser 32 is a finned heat exchanger, and a secondary condensation fan 33 is provided on the finned heat exchanger.

[0059] The present invention also provides a control method for the above-mentioned double-stage coupled heat pump, including the following steps:

[0060] When the temperature of the buffer water tank is lower than the set value of 25°C, operate the primary heat pump 1 and start the primary condensation water pump 24 at the same time. When the temperature of the buffer water tank is higher than the set value, stop operating the primary heat pump 1 and close the primary condensation water pump 24;

[0061] When the utilization side of the terminal does not reach the set temperature of 60°C, operate the secondary heat pump 3 and turn on the secondary evaporation water supply pump 25;

[0062] When the temperature of the high-temperature waste heat is above 25°C, recover the heat of the high-temperature waste heat through the secondary waste heat recovery device 37;

[0063] When the recovered heat of the high-temperature waste heat is sufficient to meet the heat absorption of the secondary heat pump 3, that is, the refrigerant evaporation temperature at the outlet of the secondary waste heat recovery device 37 reaches the set target value of 20°C, at this time, maintain the temperature of the intermediate buffer water circuit at 10 - 20°C and keep the secondary evaporation water supply pump 25 running;

[0064] When the recovered heat of the high-temperature waste heat is lower than the heat that the secondary heat pump 3 needs to absorb, that is, the refrigerant evaporation temperature at the outlet of the secondary waste heat recovery device 37 cannot reach the set target value of 20°C, operate the primary heat pump 1, turn on the primary condensation water supply pump 24, raise the temperature of the intermediate buffer water circuit 2 above 25°C, turn on the secondary evaporation water supply pump 24, operate the secondary heat pump 3, perform the first-stage evaporation through the secondary evaporator 35, absorb heat from the intermediate buffer water circuit 2 to supplement heat for the secondary heat pump 3, and then perform the second-stage evaporation through the secondary waste heat recovery device 37 for waste heat recovery, so that the refrigerant evaporation temperature at the outlet of the secondary waste heat recovery device 37 reaches the set value of 20°C; when the temperature of the intermediate buffer water circuit 2 is lower than the set value of 25°C, the primary heat pump and the primary condensation water supply pump operate to maintain the temperature of the intermediate buffer water circuit at the set value;

[0065] When there is both high-temperature waste heat and low-temperature waste heat to be utilized, and the low-temperature waste heat is water, the first-stage heat pump 1 and the second-stage heat pump 3 are operated, and the first-stage condensate supply pump 24 and the second-stage evaporation supply pump 25 are turned on. At this time, the low-temperature waste heat is recovered through the first-stage waste heat recovery device 16, and the heat is stored in the intermediate buffer water circuit 2, and the high-temperature waste heat is recovered through the second-stage waste heat recovery device 37.

[0066] When the first-stage heat pump 1 of the present invention operates, the first-stage condensate supply pump 24 must operate. When the second-stage heat pump 3 operates, the second-stage evaporation supply pump 25 must operate; whether the first-stage heat pump 1 operates depends on whether the temperature of the intermediate buffer water circuit reaches the set value. If the temperature of the buffer water tank 21 is lower than the set value, the first-stage heat pump 1 will start to operate, and at the same time, the first-stage condensate pump 24 will be started to operate. Whether the second-stage heat pump 3 operates depends on whether the temperature of the end use side reaches the required temperature. If the required temperature is not reached or the required temperature needs to be maintained, the second-stage heat pump 3 will start, and at the same time, the second-stage evaporation supply pump 25 will be started to operate.

[0067] The working principle of the present invention:

[0068] The first-stage heat pump 1 absorbs heat from the air through the first-stage evaporator 14 and absorbs heat from the low-temperature waste heat through the first-stage waste heat recovery device 16, and heats the buffer water tank 21 through the first-stage condenser 12; the refrigerant in the second-stage heat pump 3 comes out of the compressor 3, is condensed through the second-stage condenser 32 to achieve high-temperature heat supply, is throttled and depressurized through the second-stage expansion valve 34, then undergoes the first-stage evaporation through the second-stage evaporator 35, and then undergoes the second-stage evaporation through the second-stage waste heat recovery device 37 to complete the waste heat recovery;

[0069] During the off-peak electricity period at night, the first-stage heat pump 1 can operate to store heat in the buffer water tank 21 for use by the second-stage heat pump 3 during the peak electricity period during the day.

[0070] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A control method for a two-stage coupled heat pump for comprehensive utilization of regenerative high temperature, characterized in that, It includes the following steps: When the temperature of the buffer water tank is lower than the set value, operate the primary heat pump and start the primary condensate water pump simultaneously. When the temperature of the buffer water tank is higher than the set value, stop operating the primary heat pump and close the primary condensate water pump; The secondary condenser is connected to the user side pipeline. When the temperature in the user side pipeline at the end does not reach the set temperature, operate the secondary heat pump and turn on the secondary evaporation water supply pump; When the temperature of the high-temperature waste heat is above 25°C, recover the heat of the high-temperature waste heat through the secondary waste heat recovery device; When the recovered heat of the high-temperature waste heat is sufficient to meet the heat absorption of the secondary heat pump, that is, the refrigerant evaporation temperature at the outlet of the secondary waste heat recovery device reaches the set target value, at this time, maintain the temperature of the intermediate buffer water path at 10 - 20°C and keep the secondary evaporation water supply pump running; When the recovered heat of the high-temperature waste heat is lower than the heat that the secondary heat pump needs to absorb, that is, the refrigerant evaporation temperature at the outlet of the secondary waste heat recovery device does not reach the set target value, operate the primary heat pump, turn on the primary condensate water supply pump, raise the temperature of the intermediate buffer water path above 25°C, turn on the secondary evaporation water supply pump, operate the secondary heat pump, perform the first-stage evaporation through the secondary evaporator, absorb heat from the intermediate buffer water path to supplement heat for the secondary heat pump, and then perform the second-stage evaporation through the secondary waste heat recovery device for waste heat recovery to make the refrigerant evaporation temperature at the outlet of the secondary waste heat recovery device reach the set value; when the temperature of the intermediate buffer water path is lower than the set value, the primary heat pump and the primary condensate water supply pump operate to maintain the temperature of the intermediate buffer water path at the set value; When both high-temperature waste heat and low-temperature waste heat need to be utilized and the low-temperature waste heat is water, operate the primary heat pump and the secondary heat pump, turn on the primary condensate water supply pump and the secondary evaporation water supply pump. At this time, the low-temperature waste heat is recovered through the primary waste heat recovery device and the heat is stored in the intermediate buffer water path, and the high-temperature waste heat is recovered through the secondary waste heat recovery device; The double-stage coupled heat pump for the combined utilization of regenerative high temperature includes a primary heat pump, an intermediate buffer water path, and a secondary heat pump arranged in sequence; The primary heat pump includes a primary evaporator. The outlet of the primary evaporator is connected to the inlet on one side of the primary condenser through a primary compressor. The outlet on one side of the primary condenser is connected to the inlet of the primary evaporator through a primary expansion valve. A primary evaporation fan is provided on the primary evaporator; The intermediate buffer water path includes a buffer water tank. The outlet on one side of the buffer water tank is connected to the inlet on the other side of the primary condenser through a primary condensate water supply pipeline. The outlet on the other side of the primary condenser is connected to the inlet on one side of the buffer water tank through a primary condensate return pipeline. A primary condensate water supply pump is provided on the circulation pipeline connecting the buffer water tank and the primary condenser; the outlet on the other side of the buffer water tank is connected to the inlet on one side of the secondary evaporator through a secondary evaporation water supply pipeline. The outlet on one side of the secondary evaporator is connected to the inlet on the other side of the buffer water tank through a secondary evaporation return pipeline. A secondary evaporation water supply pump is provided on the circulation pipeline connecting the buffer water tank and the secondary evaporator; The secondary heat pump includes a secondary condenser. The outlet of the secondary condenser is connected to the inlet on the other side of the secondary evaporator through a secondary expansion valve. The outlet on the other side of the secondary evaporator is connected to the inlet of the secondary condenser through a secondary compressor. A secondary waste heat recovery device is provided on the circulation pipeline connecting the secondary condenser and the secondary evaporator; It further includes a primary waste heat recovery device, which is connected to the pipeline between the primary evaporator and the primary compressor; The secondary waste heat recovery device is arranged on the pipeline connecting the outlet on the other side of the secondary evaporator and the secondary compressor.

2. The control method according to claim 1, characterized in that The primary condensate water supply pump is arranged on the primary condensate water supply pipeline.

3. The control method according to claim 1, characterized in that, The secondary evaporation water supply pump is arranged on the secondary evaporation water supply pipeline.

4. The control method according to claim 2, wherein The primary waste heat recovery device is a water-fluorine heat exchanger, selected from a shell-and-tube heat exchanger, a plate heat exchanger or a heat exchange tank; The secondary waste heat recovery device is a shell-and-tube heat exchanger, a plate heat exchanger, a heat exchange tank or a finned heat exchanger, and a secondary waste heat recovery fan is provided on the finned heat exchanger.

5. The control method according to any one of claims 1-4, characterized in that, The secondary condenser is a shell-and-tube heat exchanger, a plate heat exchanger, a heat exchange tank or a finned heat exchanger, and a secondary condensation fan is provided on the finned heat exchanger.

6. The control method according to claim 5, wherein A refrigerant suitable for low-temperature evaporation is provided in the circulation pipeline of the primary heat pump; a refrigerant suitable for high-temperature condensation is provided in the circulation pipeline of the secondary heat pump.

7. The control method according to claim 6, characterized in that The refrigerant for high-temperature condensation is selected from R515B, R134a or R245fa; the refrigerant for low-temperature evaporation is selected from R410A, R404A or R32.

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