System and method for coupling utilization of low-temperature flue gas waste heat and solar energy

Abstract

The application discloses a system and method for coupling and utilizing low-temperature flue gas waste heat and solar energy, and relates to an industrial energy-saving equipment, which comprises a first heat exchanger, a thermal power generation device and a heat pump device. The first heat exchanger of the thermal power generation device is provided with a first high-temperature medium pipeline and a first low-temperature medium pipeline. The two ends of the first high-temperature medium pipeline are respectively provided with a first high-temperature medium inlet and a first high-temperature medium outlet. The two ends of the first low-temperature medium pipeline are respectively provided with a first low-temperature medium inlet and a first low-temperature medium outlet. The first high-temperature medium inlet is connected with high-temperature flue gas. The first low-temperature medium outlet is connected with a hot side inlet of a first unit evaporator. A hot side outlet of the first unit evaporator is connected with the first low-temperature medium inlet. A cold side inlet of a first unit condenser is connected with a fourth cold water source. A cold side outlet of the first unit condenser is connected with a hot side inlet of a second unit evaporator of the heat pump device. The application can make full use of flue gas waste heat and power generation waste heat, and improve energy efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to an industrial energy-saving equipment, in particular to a system and method for coupling and utilizing low-temperature flue gas waste heat and solar energy. BACKGROUND

[0002] The low-temperature flue gas of industrial kilns such as ceramic and steel has the characteristics of low energy grade and large flue gas volume, but it is difficult to utilize, and is usually directly discharged, and a large amount of waste heat is wasted. Meanwhile, the existing organic Rankine cycle power generation technology (ORC) has a low thermoelectric efficiency, and a large amount of low-temperature waste heat is directly discharged, causing energy waste. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a system and method for coupling and utilizing low-temperature flue gas waste heat and solar energy, which fully utilize flue gas waste heat, improve the energy efficiency of a thermal power generation device, fully utilize power generation waste heat, and improve the energy efficiency of a heat pump device.

[0004] In order to solve the above technical problems, the present application provides the following technical solutions:

[0005] The system for coupling and utilizing low-temperature flue gas waste heat and solar energy comprises a first heat exchanger, a thermal power generation device, and a heat pump device. The thermal power generation device comprises a first unit evaporator, an expander, a generator, a first unit condenser, and a first working medium pump. The cold side outlet of the first unit evaporator, the expander, the hot side inlet of the first unit condenser, the hot side outlet of the first unit condenser, the first working medium pump, and the cold side inlet of the first unit evaporator are connected by pipes in the direction of working medium flow. The first heat exchanger is provided with a first high-temperature medium pipe and a first low-temperature medium pipe. The two ends of the first high-temperature medium pipe are respectively a first high-temperature medium inlet and a first high-temperature medium outlet. The two ends of the first low-temperature medium pipe are respectively a first low-temperature medium inlet and a first low-temperature medium outlet. The first high-temperature medium inlet is connected to high-temperature flue gas. The first low-temperature medium outlet is connected to the hot side inlet of the first unit evaporator. The hot side outlet of the first unit evaporator is connected to the first low-temperature medium inlet. The heat pump device comprises a second unit evaporator, a second unit condenser, and a compressor. The cold side outlet of the second unit evaporator, the compressor, the hot side inlet of the second unit condenser, the hot side outlet of the second unit condenser, and the cold side inlet of the second unit evaporator are connected by pipes in the direction of working medium flow. A fifth flow regulating valve is arranged between the hot side outlet of the second unit condenser and the cold side inlet of the second unit evaporator. The cold side inlet of the first unit condenser is connected to a fourth cold water source. The cold side outlet of the first unit condenser is connected to the hot side inlet of the second unit evaporator. The hot side outlet of the second unit evaporator outputs hot water.

[0006] Further, a second heat exchanger is further included, and a second high-temperature medium pipeline and a second low-temperature medium pipeline are arranged on the second heat exchanger, two ends of the second high-temperature medium pipeline are respectively a second high-temperature medium inlet and a second high-temperature medium outlet, two ends of the second low-temperature medium pipeline are respectively a second low-temperature medium inlet and a second low-temperature medium outlet, the second low-temperature medium inlet is connected with a second cold water source, the second low-temperature medium outlet is connected with a cold side inlet of the second unit evaporator, the second high-temperature medium outlet is connected with the first low-temperature medium inlet, the first low-temperature medium outlet is provided with a first output pipeline, the first output pipeline is provided with a first three-way valve, the first output pipeline is connected with an inlet of the first three-way valve, two outlets of the first three-way valve are respectively connected with the second high-temperature medium inlet and a hot side inlet of the first unit evaporator, the first output pipeline is provided with a first temperature sensor, the first temperature sensor is used to collect a temperature T1 of medium at the first low-temperature medium outlet, the second high-temperature medium outlet is provided with a second temperature sensor, the second temperature sensor is used to collect a temperature T2 of medium at the second high-temperature medium outlet, the second low-temperature medium inlet is provided with a second water inlet pipe, the second cold water source enters the second heat exchanger through the second water inlet pipe, the second water inlet pipe is provided with a second flow regulating valve, a cold side inlet of the first unit condenser is provided with a fourth water inlet pipe, the fourth water inlet pipe is provided with a fourth flow control valve, a third temperature sensor and a pressure sensor are arranged between a cold side outlet of the first unit evaporator and the expander, and the third temperature sensor is used to collect a temperature T3 of the cold side outlet of the first unit evaporator.

[0007] Further, a PV / T assembly and a water storage device are further included, an inlet of the PV / T assembly is connected with a sixth cold water source, an outlet of the PV / T assembly is connected with an inlet of the water storage device, an outlet of the water storage device is connected with a cold side inlet of the second unit condenser, and a cold side outlet of the second unit condenser outputs hot water.

[0008] Further, a seventh temperature sensor is arranged at the cold side outlet of the second unit condenser, a seventh regulating water pump is arranged between the outlet of the water storage device and the cold side inlet of the second unit condenser, and the seventh temperature sensor is used to collect a temperature T7 of the cold side outlet of the second unit condenser.

[0009] Further, a hot side outlet of the second unit evaporator is connected with the inlet of the PV / T assembly.

[0010] Further, the inlet of the PV / T assembly is provided with a sixth water inlet pipe, the outlet is provided with a sixth water outlet pipe, a sixth flow control valve is arranged on the sixth water inlet pipe, a sixth temperature sensor is arranged on the sixth water outlet pipe, the sixth temperature sensor is used to collect the PV / T assembly outlet water temperature T6, the sixth cold water source enters the PV / T assembly through the sixth water inlet pipe, the second unit evaporator hot side outlet is provided with a fifth water outlet pipe, the fifth water outlet pipe is communicated with the sixth water inlet pipe, a second three-way valve is arranged on the fifth water outlet pipe, the fifth water outlet pipe is connected with the inlet of the second three-way valve, the sixth water inlet pipe is connected with one outlet of the second three-way valve, and the other outlet of the second three-way valve is an external discharge passage.

[0011] The method for recovering waste heat by using the system for coupling utilization of low-temperature flue gas waste heat and solar energy comprises the following steps:

[0012] P 额定 is the rated power of the thermal power generation device, t0, t1 and t2 are set values, when the temperature T1 of the medium at the outlet of the first low-temperature medium is less than t0, the passage between the first three-way valve and the first unit evaporator is closed, the passage between the first three-way valve and the second high-temperature medium inlet of the second heat exchanger is opened, the second flow regulating valve is opened, and the opening degree of the second flow regulating valve is adjusted to stabilize the second high-temperature medium outlet temperature T2 at the limited value t2.

[0013] When t0 额定 < P < 1.1P 额定 , P 额定 is the rated power of the thermal power generation device, the passage between the first three-way valve and the first unit evaporator is fully opened, the passage between the first three-way valve and the second high-temperature medium inlet of the second heat exchanger is fully closed, the second flow regulating valve is closed, and the fourth flow control valve is opened.

[0014] When T1 > t1, the passage between the first three-way valve and the first unit evaporator is fully opened, the passage between the first three-way valve and the second high-temperature medium inlet of the second heat exchanger is fully opened, the second flow regulating valve is opened, the opening degree of the second flow regulating valve is adjusted to control P to be less than 1.1P 额定 , and the second high-temperature medium outlet water temperature T2 is stabilized at the limited value t2.

[0015] Further, when the output voltage of the PV / T assembly is less than or equal to P1, the PV / T assembly is not started, the passage of the second three-way valve to the PV / T assembly is opened, the external discharge passage of the second three-way valve is closed, the seventh regulating water pump is used to regulate the flow to keep the cold side outlet temperature T7 of the second unit condenser at 85-95 DEG C, and P1 is a set value.

[0016] When the output voltage of the PV / T assembly is greater than P1, the PV / T assembly starts, when the water outlet temperature T6 of the PV / T assembly is less than 45 DEG C, the passage of the second three-way valve leading to the PV / T assembly is opened, the opening degree of the discharge passage of the second three-way valve is adjusted to control T6 to be stabilized at 45 DEG C + / - 0.1 DEG C, when T6 is greater than 45 DEG C, the passage of the second three-way valve leading to the PV / T assembly is opened, the discharge passage of the second three-way valve is closed, and the opening degree of the sixth flow control valve is adjusted to control T6 to be stabilized at 45 DEG C + / - 0.1 DEG C.

[0017] Compared with the prior art, the system for coupling and utilizing low-temperature flue gas waste heat and solar energy has at least the following beneficial effects:

[0018] The system for coupling and utilizing low-temperature flue gas waste heat and solar energy comprises a first heat exchanger, a thermal power generating device, and a heat pump device, the first high-temperature medium inlet is connected with high-temperature flue gas, the first low-temperature medium outlet is connected with the hot side inlet of a first unit evaporator, and the hot side outlet of the first unit evaporator is connected with the first low-temperature medium inlet, so that the waste heat of the high-temperature flue gas is recycled and utilized for power generation of the thermal power generating device, the flue gas waste heat is fully utilized, and the energy efficiency of the thermal power generating device is improved, meanwhile, the fourth cold water source exchanges heat with the working medium in the first unit condenser, the fourth cold water source exchanges heat with the working medium in the second unit evaporator after being heated and having a temperature rise in the first unit condenser, the low-temperature waste heat after power generation of the thermal power generating device is transmitted to the heat pump device, the power generation waste heat is fully utilized, the heat source temperature of the second unit evaporator is improved, the heat exchange temperature difference of the second unit condenser is reduced, and the energy efficiency value of the heat pump device is improved by 10% to 20%, and the heat pump equipment investment is reduced.

[0019] The system for coupling and utilizing low-temperature flue gas waste heat and solar energy will be further described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Fig. 1 is a structural schematic diagram of the system for coupling and utilizing low-temperature flue gas waste heat and solar energy. DETAILED DESCRIPTION

[0021] As Figure 1As shown, the system for coupling and utilizing low-temperature flue gas waste heat and solar energy of the present application comprises a first heat exchanger 01, a thermal power generation device, and a heat pump device. The thermal power generation device is an ORC power generation device. The thermal power generation device comprises a first unit evaporator 21, an expander 22, a generator 25, a first unit condenser 23, and a first working medium pump 24. The cold side outlet of the first unit evaporator 21, the expander 22, the hot side inlet of the first unit condenser 23, the hot side outlet of the first unit condenser 23, the first working medium pump 24, and the cold side inlet of the first unit evaporator 21 are connected by pipes in the direction of working medium flow. A power sensor 251 is arranged on the power transmission cable of the generator 25. The power sensor 251 is used to collect power generation power. The first heat exchanger 01 is provided with a first high-temperature medium pipeline and a first low-temperature medium pipeline. The two ends of the first high-temperature medium pipeline are respectively a first high-temperature medium inlet and a first high-temperature medium outlet. The two ends of the first low-temperature medium pipeline are respectively a first low-temperature medium inlet and a first low-temperature medium outlet. The first high-temperature medium inlet is connected to high-temperature flue gas. The first low-temperature medium outlet is connected to the hot side inlet of the first unit evaporator 21. The hot side outlet of the first unit evaporator 21 is connected to the first low-temperature medium inlet. The heat pump device comprises a second unit evaporator 31, a second unit condenser 32, and a compressor 33. The cold side outlet of the second unit evaporator 31, the compressor 33, the hot side inlet of the second unit condenser 32, the hot side outlet of the second unit condenser 32, and the cold side inlet of the second unit evaporator 31 are connected by pipes in the direction of working medium flow. A fifth flow regulating valve 34 is arranged between the hot side outlet of the second unit condenser 32 and the cold side inlet of the second unit evaporator 31. The cold side inlet of the first unit condenser 23 is connected to a fourth cold water source. The cold side outlet of the first unit condenser 23 is connected to the hot side inlet of the second unit evaporator 31. The hot side outlet of the second unit evaporator 31 outputs hot water. In the first unit evaporator 21, the working medium evaporates and absorbs heat. The warmed medium flowing out of the first low-temperature medium outlet of the first heat exchanger 01 exchanges heat with the working medium in the first unit evaporator 21. The warmed medium flowing out of the first low-temperature medium outlet reduces in temperature after passing through the first unit evaporator 21. The medium enters the first heat exchanger 01 through the first low-temperature medium inlet and exchanges heat with high-temperature flue gas. The temperature of the medium increases after the heat exchange. The medium enters the first unit evaporator 21 again and circulates. The fourth cold water source exchanges heat with the working medium in the first unit condenser 23. The fourth cold water source absorbs heat in the first unit condenser 23 and increases in temperature. The fourth cold water source exchanges heat with the working medium in the second unit evaporator 31 after the temperature increases. The temperature of the fourth cold water source decreases after the heat exchange. The fourth cold water source is output through the hot side outlet of the second unit evaporator 31.The system for coupling and utilizing low-temperature flue gas waste heat and solar energy comprises a first heat exchanger 01, a thermal power generation device, a heat pump device, a first high-temperature medium inlet connected to high-temperature flue gas, a first low-temperature medium outlet connected to a hot side inlet of a first unit evaporator 21, and a hot side outlet of the first unit evaporator 21 connected to the first low-temperature medium inlet, so that the waste heat of the high-temperature flue gas is recycled and utilized for power generation of the thermal power generation device, the flue gas waste heat is fully utilized, the energy efficiency of the thermal power generation device is improved, meanwhile, a fourth cold water source exchanges heat with a working medium in a first unit condenser 23, the fourth cold water source exchanges heat with the working medium in a second unit evaporator 31 after being heated and having a temperature increased in the first unit condenser 23, the low-temperature waste heat after power generation of the thermal power generation device is transmitted to the heat pump device, the power generation waste heat is fully utilized, the heat source temperature of the second unit evaporator 31 is increased, the heat exchange temperature difference of a second unit condenser is reduced, and the energy efficiency value of the heat pump device is increased by 10% to 20%, and the heat pump equipment investment is reduced.

[0022] Optionally, the system for coupling and utilizing low-temperature flue gas waste heat and solar energy further comprises a second heat exchanger 51, the second heat exchanger 51 is provided with a second high-temperature medium pipeline and a second low-temperature medium pipeline, two ends of the second high-temperature medium pipeline are respectively a second high-temperature medium inlet and a second high-temperature medium outlet, two ends of the second low-temperature medium pipeline are respectively a second low-temperature medium inlet and a second low-temperature medium outlet, the second low-temperature medium inlet is connected to a second cold water source, the second low-temperature medium outlet is connected to a cold side inlet of a second unit evaporator 31, the second high-temperature medium outlet is connected to a first low-temperature medium inlet, the first low-temperature medium outlet is provided with a first output pipeline 11, the first output pipeline 11 is provided with a first three-way valve 12, the first output pipeline 11 is connected to an inlet of the first three-way valve 12, the second high-temperature medium inlet and a hot side inlet of a first unit evaporator 21 are respectively connected to two outlets of the first three-way valve 12, the first output pipeline 11 is provided with a first temperature sensor 13, the first temperature sensor 13 is used for collecting a temperature T1 of a medium at the first low-temperature medium outlet, the second high-temperature medium outlet is provided with a second temperature sensor 511, the second temperature sensor 511 is used for collecting a temperature T2 of a medium at the second high-temperature medium outlet, the second low-temperature medium inlet is provided with a second water inlet pipe 512, the second cold water source enters the second heat exchanger 51 through the second water inlet pipe 512, the second water inlet pipe 512 is provided with a second flow adjusting valve 513, a cold side inlet of the first unit condenser 23 is provided with a fourth water inlet pipe 231, the fourth cold water source enters the first unit condenser 23 through the fourth water inlet pipe 231, the fourth water inlet pipe 231 is provided with a fourth flow control valve 232, a third temperature sensor 221 and a pressure sensor 222 are arranged between a cold side outlet of the first unit evaporator 21 and the expander 22, and the third temperature sensor 221 is used for collecting a temperature T3 of the cold side outlet of the first unit evaporator 21.

[0023] P is rated power, t0, t1, t2 are empirical values, when T1 < t0, the passage between the first three-way valve 12 and the first unit evaporator 21 is closed, the passage between the first three-way valve 12 and the second high-temperature medium inlet of the second heat exchanger 51 is opened, the thermal power generation device is closed, the second flow regulating valve 513 is opened, and the opening degree of the second flow regulating valve 513 is adjusted to stabilize the second high-temperature medium outlet water temperature T2 at the limited value t2.

[0024] When t0 < T1 < t1, corresponding to 0.5P 额定 < P < 1.1P 额定 , P 额定 is the rated power of the thermal power generation device, the passage between the first three-way valve 12 and the first unit evaporator 21 is fully opened, the passage between the first three-way valve 12 and the second high-temperature medium inlet of the second heat exchanger 51 is fully closed, the second flow regulating valve 513 is closed, and the fourth flow control valve 232 is opened. The frequency of the working medium pump 24 is controlled to ensure that the superheat ΔT is in the range of 3-5℃.

[0025] When T1 > t1, the passage between the first three-way valve 12 and the first unit evaporator 21 is fully opened, the passage between the first three-way valve 12 and the second high-temperature medium inlet of the second heat exchanger 51 is fully opened, the second flow regulating valve 513 is opened, and the opening degree of the second flow regulating valve 513 is adjusted to control P to be stable at less than 1.1P 额定 . The opening degree of the second flow regulating valve 513 is adjusted to control the second high-temperature medium outlet water temperature T2 to be stable at the limited value t. Through the second heat exchanger 51 and the first three-way valve 12, the flue gas waste heat can be effectively utilized when the flue gas waste heat fluctuates, ensuring the safety of the thermal power generation device and having strong resistance to heat source fluctuations.

[0026] Optionally, the system for coupling and utilizing low-temperature flue gas waste heat and solar energy according to the present application further comprises a (solar photovoltaic / thermal component) PV / T component 41 and a water storage device 42, the inlet of the PV / T component 41 is connected to the sixth cold water source, the outlet of the PV / T component 41 is connected to the inlet of the water storage device 42, the outlet of the water storage device 42 is connected to the cold side inlet of the second unit condenser 32, and the cold side outlet of the second unit condenser 32 outputs hot water. The temperature of the sixth cold water source is preliminarily raised to about 45℃ after passing through the PV / T component 41, and the temperature of the sixth cold water source preliminarily raised in temperature is further raised to 85-95℃ after passing through the second unit condenser 32, thereby widening the application range of the hot water output by the PV / T component 41.

[0027] Optionally, a seventh temperature sensor 321 is arranged at the cold side outlet of the second unit condenser 32, and a seventh regulating water pump 322 is arranged between the outlet of the water storage device 42 and the cold side inlet of the second unit condenser 32, the seventh temperature sensor 321 collects the temperature T7 of the cold side outlet of the second unit condenser 32, and the flow of the seventh regulating water pump 322 is controlled according to the value of T7 so as to keep T7 at 85-95℃.

[0028] Optionally, the hot side outlet of the second unit evaporator 31 is connected to the inlet of the PV / T assembly 41.

[0029] Optionally, the inlet of the PV / T assembly 41 is provided with a sixth water inlet pipe 411, and the outlet is provided with a sixth water outlet pipe 412, the sixth water inlet pipe 411 is provided with a sixth flow control valve 413, the sixth water outlet pipe 412 is provided with a sixth temperature sensor 414, the sixth temperature sensor 414 is used to collect the outlet water temperature T6 of the PV / T assembly, a sixth cold water source enters the PV / T assembly 41 through the sixth water inlet pipe 411, the hot side outlet of the second unit evaporator 31 is provided with a fifth water outlet pipe 311, the fifth water outlet pipe 311 is communicated with the sixth water inlet pipe 411, the fifth water outlet pipe 311 is provided with a fifth working medium pump 313 and a second three-way valve 312, the fifth water outlet pipe 311 is connected to the inlet of the second three-way valve 312, the sixth water inlet pipe 411 is connected to one outlet of the second three-way valve 312, and the other outlet of the second three-way valve 312 is an external discharge passage.

[0030] P1 is a set value, when the output voltage of the PV / T assembly 41 is less than or equal to P1, the PV / T assembly 41 is not started, at this time, the passage of the second three-way valve 312 leading to the PV / T assembly 41 is opened, the external discharge passage of the second three-way valve 312 is closed, the fourth cold water source output by the hot side of the second unit evaporator 31 enters the water storage device 42 after passing through the PV / T assembly 41, and the hot water at the outlet of the water storage device 42 enters the second unit condenser 32, and the flow is adjusted by the seventh regulating water pump 322 so as to keep T7 at 85-95℃.

[0031] When the output voltage of the PV / T module 41 is greater than P1, the PV / T module 41 starts to operate. When the PV / T module 41 starts, the control logic for the water temperature at the outlet of the PV / T module starts to run. Control logic for the water temperature at the outlet of the PV / T module: When T6 is less than 45 °C, the passage of the second three-way valve 312 leading to the PV / T module 41 is opened, and the opening degree of the external discharge passage of the second three-way valve 312 is adjusted to control T6 to be stable at 45 ± 0.1 °C. When T6 is greater than 45 °C, the passage of the second three-way valve 312 leading to the PV / T module 41 is opened, the external discharge passage of the second three-way valve 312 is closed, and the opening degree of the sixth flow control valve 413 is adjusted to control T6 to be stable at 45 ± 0.1 °C. The hot water at the outlet of the PV / T module 41 enters the water storage device 42. Under rated conditions, the water output of the water storage device 42 is generally 1 / 4 of the water input.

[0032] Since the system for coupling and utilization of low-temperature flue gas waste heat and solar energy of the present invention further includes the PV / T module 41, it can effectively combine the thermal power generation device, the heat pump device and the PV / T module, realize the cascade utilization of flue gas waste heat, power generation waste heat and solar energy, improve the comprehensive energy utilization efficiency of the system and the ability to resist heat source fluctuations, increase the temperature of the hot water output by the PV / T module 41, and broaden the application range of the hot water output by the PV / T module 41.

[0033] A method for coupling and utilization of waste heat according to the present invention includes the following steps:

[0034] P 额定 is the rated power generation of the thermal power generation device, t0, t1, t2 are set empirical values. When the temperature T1 of the medium at the outlet of the first low-temperature medium is less than t0, the passage between the first three-way valve 12 and the first unit evaporator 21 is closed, the passage between the first three-way valve 12 and the second high-temperature medium inlet of the second heat exchanger 51 is opened, the thermal power generation device is shut down, the second flow control valve 513 is opened, and the opening degree of the second flow control valve 513 is adjusted to make the temperature T2 at the outlet of the second high-temperature medium stable at the limit value t2;

[0035] When t0 < T1 < t1, corresponding to 0.5P 额定 < P < 1.1P 额定 P 额定 is the rated power generation of the thermal power generation device, the passage between the first three-way valve 12 and the first unit evaporator 21 is fully opened, the passage between the first three-way valve 12 and the second high-temperature medium inlet of the second heat exchanger 51 is fully closed, the second flow control valve 513 is closed, and the fourth flow control valve 232 is opened. The frequency of the working fluid pump 24 is controlled to ensure that the superheat degree ΔT is within the range of 3 °C to 5 °C.

[0036] When T1>t1, the passage between the first three-way valve 12 and the first unit evaporator 21 is fully open, the passage between the first three-way valve 12 and the second high-temperature medium inlet of the second heat exchanger 51 is fully open, the second flow regulating valve 513 is opened, and by adjusting the opening degree of the second flow regulating valve 513, Pstable is controlled to be less than 1.1P 额定 . Adjusting the opening degree of the second flow regulating valve 513 controls the second high-temperature medium outlet water temperature T2 to stabilize at a defined value t.

[0037] Optionally, the waste heat coupling utilization method further comprises: when the output voltage of the PV / T assembly 41 is less than or equal to P1, the PV / T assembly 41 is not started, at this time, the passage of the second three-way valve 312 leading to the PV / T assembly 41 is open, the external discharge passage of the second three-way valve 312 is closed, the fourth cold water source of the hot side output of the second unit evaporator 31 enters the water storage device 42 through the PV / T assembly 41, and the hot water at the outlet of the water storage device 42 enters the second unit condenser 32, and the flow is adjusted by the seventh regulating water pump 322 to keep T7 at 85-95℃, and P1 is a set value.

[0038] When the output voltage of the PV / T assembly 41 is greater than P1, the PV / T assembly 41 is started to work, and when the PV / T assembly 41 is started, the PV / T assembly outlet water temperature control logic starts to run. The PV / T assembly outlet water temperature control logic: when T6 is less than 45℃, the passage of the second three-way valve 312 leading to the PV / T assembly 41 is open, and the opening degree of the external discharge passage of the second three-way valve 312 is adjusted to control T6 to stabilize at 45±0.1℃. When T6 is greater than 45℃, the passage of the second three-way valve 312 leading to the PV / T assembly 41 is open, the external discharge passage of the second three-way valve 312 is closed, the opening degree of the sixth flow control valve 413 is adjusted to control T6 to stabilize at 45±0.1℃, and the hot water at the outlet of the PV / T assembly 41 enters the water storage device 42, and the water output of the water storage device 42 is generally 1 / 4 of the water input under normal working conditions.

[0039] The above-described embodiments are merely preferred embodiments of the present application and are not intended to limit the scope of the present application. Various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art without departing from the design spirit of the present application shall fall within the protection scope of the present application.

Claims

1. A system for coupling and utilizing waste heat from low-temperature flue gas with solar energy, characterized in that, The system includes a first heat exchanger (01), a thermal power generation device, and a heat pump device. The thermal power generation device includes a first unit evaporator (21), an expander (22), a generator (25), a first unit condenser (23), and a first working fluid pump (24). The cold side outlet of the first unit evaporator (21), the expander (22), the hot side inlet of the first unit condenser (23), the hot side outlet of the first unit condenser (23), the first working fluid pump (24), and the cold side inlet of the first unit evaporator (21) are connected by pipes according to the direction of working fluid flow. The first heat exchanger (01) is provided with a first high-temperature medium pipe and a first low-temperature medium pipe. The two ends of the first high-temperature medium pipe are a first high-temperature medium inlet and a first high-temperature medium outlet, respectively. The two ends of the first low-temperature medium pipe are a first low-temperature medium inlet and a first low-temperature medium outlet, respectively. The first high-temperature medium inlet is connected to high-temperature flue gas, and the first low-temperature medium outlet is connected to the first unit evaporator (21), an expander (22), a generator (25), a first unit condenser (23), and a first working fluid pump (24). The heat pump device includes a second unit evaporator (31), a second unit condenser (32), and a compressor (33). The cold side outlet of the second unit evaporator (31), the compressor (33), the hot side inlet of the second unit condenser (32), the hot side outlet of the second unit condenser (32), and the cold side inlet of the second unit evaporator (31) are connected by pipes according to the working fluid flow direction. A fifth flow regulating valve (34) is provided between the hot side outlet of the second unit condenser (32) and the cold side inlet of the second unit evaporator (31). The cold side inlet of the first unit condenser (23) is connected to a fourth cold water source. The cold side outlet of the first unit condenser (23) is connected to the hot side inlet of the second unit evaporator (31). The hot side outlet of the second unit evaporator (31) outputs hot water.

2. The system for coupling and utilizing low-temperature flue gas waste heat with solar energy according to claim 1, characterized in that, It also includes a second heat exchanger (51), on which a second high-temperature medium pipeline and a second low-temperature medium pipeline are provided. The two ends of the second high-temperature medium pipeline are a second high-temperature medium inlet and a second high-temperature medium outlet, respectively. The two ends of the second low-temperature medium pipeline are a second low-temperature medium inlet and a second low-temperature medium outlet, respectively. The second low-temperature medium inlet is connected to a second cold water source, and the second low-temperature medium outlet is connected to the cold side inlet of the second unit evaporator (31). The second high-temperature medium outlet is connected to the first low-temperature medium inlet. The first low-temperature medium outlet is provided with a first output pipeline (11). The first output pipeline (11) is provided with a first three-way valve (12). The first output pipeline (11) is connected to the inlet of the first three-way valve (12). The second high-temperature medium inlet and the hot side inlet of the first unit evaporator (21) are respectively connected to the two outlets of the first three-way valve (12). The first output pipeline (11) is provided with a first temperature sensor (13). A temperature sensor (13) is used to collect the temperature T1 of the medium at the outlet of the first low-temperature medium. A second temperature sensor (511) is provided at the outlet of the second high-temperature medium. The second temperature sensor (511) is used to collect the temperature T2 of the medium at the outlet of the second high-temperature medium. A second water inlet pipe (512) is provided at the inlet of the second low-temperature medium. The second cold water source enters the second heat exchanger (51) through the second water inlet pipe (512). A second flow regulating valve (513) is provided on the second water inlet pipe (512). A fourth water inlet pipe (231) is provided at the cold side inlet of the first unit condenser (23). A fourth flow control valve (232) is provided on the fourth water inlet pipe (231). A third temperature sensor (221) and a pressure sensor (222) are provided between the cold side outlet of the first unit evaporator (21) and the expander (22). The third temperature sensor (221) is used to collect the cold side outlet temperature T3 of the first unit evaporator (21).

3. The system for coupling and utilizing low-temperature flue gas waste heat with solar energy according to claim 2, characterized in that, It also includes a PV / T component (41) and a water storage device (42). The inlet of the PV / T component (41) is connected to a sixth cold water source, the outlet of the PV / T component (41) is connected to the inlet of the water storage device (42), the outlet of the water storage device (42) is connected to the cold side inlet of the second unit condenser (32), and the cold side outlet of the second unit condenser (32) outputs hot water.

4. The system for coupling and utilizing low-temperature flue gas waste heat with solar energy according to claim 3, characterized in that, A seventh temperature sensor (321) is installed at the cold side outlet of the second unit condenser (32), and a seventh regulating water pump (322) is installed between the outlet of the water storage device (42) and the cold side inlet of the second unit condenser (32). The seventh temperature sensor (321) is used to collect the cold side outlet temperature T7 of the second unit condenser (32).

5. The system for coupling and utilizing low-temperature flue gas waste heat with solar energy according to claim 4, characterized in that, The hot-side outlet of the second unit evaporator (31) is connected to the inlet of the PV / T module (41).

6. The system for coupling and utilizing low-temperature flue gas waste heat with solar energy according to claim 5, characterized in that, The PV / T module (41) has a sixth inlet pipe (411) and an outlet pipe (412). A sixth flow control valve (413) is installed on the sixth inlet pipe (411), and a sixth temperature sensor (414) is installed on the sixth outlet pipe (412). The sixth temperature sensor (414) is used to collect the outlet water temperature T6 of the PV / T module. The sixth cold water source enters the PV / T module (41) through the sixth inlet pipe (411). The hot side outlet of the evaporator (31) of the second unit is provided with a fifth water outlet pipe (311), which is connected to the sixth water inlet pipe (411). A second three-way valve (312) is provided on the fifth water outlet pipe (311). The fifth water outlet pipe (311) is connected to the inlet of the second three-way valve (312), and the sixth water inlet pipe (411) is connected to one outlet of the second three-way valve (312). The other outlet of the second three-way valve (312) is an external discharge passage.

7. A method for recovering waste heat using a system that couples low-temperature flue gas waste heat with solar energy as described in any one of claims 1-6, characterized in that, Includes the following steps: P 额定 is the rated power generation of the thermal power generation device, t0, t1, and t2 are set values. When the temperature T1 of the medium at the outlet of the first low-temperature medium is less than t0, the passage between the first three-way valve (12) and the first unit evaporator (21) is closed, the passage between the first three-way valve (12) and the second high-temperature medium inlet of the second heat exchanger (51) is opened, the second flow regulating valve (513) is opened, and the opening of the second flow regulating valve (513) is adjusted to make the temperature T2 at the outlet of the second high-temperature medium stable at the limit value t2; When t0 < T1 < t1, it corresponds to 0.5P 额定 <P < 1.1P 额定 , P 额定 is the rated power generation of the thermal power generation device. The passage between the first three-way valve (12) and the first unit evaporator (21) is fully open, the passage between the first three-way valve (12) and the second high-temperature medium inlet of the second heat exchanger (51) is fully closed, the second flow regulating valve (513) is closed, and the fourth flow control valve (232) is opened; When T1>t1, the passage between the first three-way valve (12) and the first unit evaporator (21) is fully open, the passage between the first three-way valve (12) and the second high-temperature medium inlet of the second heat exchanger (51) is fully open, and the second flow regulating valve (513) is opened. By adjusting the opening degree of the second flow regulating valve (513), P is controlled to be stable less than 1.1P. 额定 The outlet water temperature T2 of the second high-temperature medium is controlled to remain stable at the limit value t2.

8. The method according to claim 7, characterized in that, When the output voltage of the PV / T component (41) is less than or equal to P1, the PV / T component (41) is not started, the passage of the second three-way valve (312) to the PV / T component (41) is opened, the external discharge passage of the second three-way valve (312) is closed, and the flow rate is adjusted by the seventh regulating water pump (322) to keep the cold side outlet temperature T7 of the second unit condenser (32) at 85℃~95℃, and P1 is the set value; When the output voltage of the PV / T component (41) is greater than P1, the PV / T component (41) starts. When the outlet water temperature T6 of the PV / T component is less than 45℃, the passage of the second three-way valve (312) to the PV / T component (41) is opened. The opening degree of the discharge passage of the second three-way valve (312) is adjusted to control T6 to stabilize at 45±0.1℃. When T6 is greater than 45℃, the passage of the second three-way valve (312) to the PV / T component (41) is opened, the discharge passage of the second three-way valve (312) is closed, and the opening degree of the sixth flow control valve (413) is adjusted to control T6 to stabilize at 45±0.1℃.

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