An Adaptive Adjustment Method for Regenerative Rate of Transcritical / Supercritical CO2 Industrial High-Temperature Steam Heat Pump

Abstract

This invention discloses an adaptive adjustment method for the regeneration rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump, comprising an air-source evaporator assembly, a waste heat source gas heater assembly, a regenerator assembly, a centrifugal compressor assembly, a gas cooler assembly, a high-temperature water / steam circuit, an electronic expansion valve, a medium-pressure liquid storage tank, a working fluid pump, several temperature and pressure sensors, solenoid valves, etc. The CO2 heat pump system, based on system requirements and environmental conditions, adjusts the speed of the centrifugal compressor and controls the solenoid valve assembly to switch between air-source heating and industrial waste heat heating modes in real time, corresponding to transcritical CO2 and supercritical CO2 cycle conditions respectively. This effectively changes the compression ratio of the compressor in the system, achieving adaptive adjustment of the regeneration rate of the regenerator.

Description

Technical Field

[0001] This invention belongs to the field of industrial high-temperature steam heat pumps, specifically relating to an adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump. Background Technology

[0002] Industrial waste heat resources are abundant, especially in industries such as steel, non-ferrous metals, chemicals, cement, building materials, petroleum and petrochemicals, light industry, and coal, where waste heat accounts for approximately 17-67% of total fuel consumption, of which about 60% is recoverable. However, most industrial sectors directly discharge large amounts of industrial waste heat as flue gas and wastewater, resulting in enormous waste. Currently, the waste heat recovery rate is only about 30%, indicating significant potential for improvement. In the industrial sector, the demand for steam or other forms of heating at temperatures below 260℃ accounts for a considerable proportion. This temperature range applies to multiple industries, including but not limited to petroleum refining, smelting, and energy storage. However, the main heating methods in this temperature range are still traditional primary energy combustion or electric heating. These heating methods suffer from low energy conversion efficiency: the energy conversion efficiency of primary energy combustion heating is typically no more than 50%; the efficiency of electric heating is also limited by the electricity generation process itself, often not exceeding 100%; a large amount of energy is wasted during the conversion process, not only increasing energy consumption costs but also exacerbating environmental impacts.

[0003] CO2 heat pumps, as an advanced heating technology, possess excellent heating performance. By employing an oil-free multi-stage centrifugal compressor, CO2 heat pumps can achieve high exhaust temperatures, reaching up to approximately 300°C, thus broadening their applicability in heating processes. Furthermore, CO2 heat pump technology expands the heat source to include air energy and waste heat energy. By utilizing these often-overlooked energy sources, the electrothermal conversion efficiency exceeds 200%, and can even reach over 350% under suitable operating conditions. This high-efficiency energy conversion not only reduces energy consumption costs but also decreases dependence on traditional energy sources, thereby reducing adverse environmental impacts and opening a new channel for bridging carbon storage and utilization in the industrial heating sector.

[0004] However, industrial waste heat temperatures are unstable, and in some cases, switching between waste heat sources and air source heat sources is necessary, resulting in a wide operating temperature range for CO2 heat pump cycles, potentially operating in transcritical or supercritical modes. Under these conditions, the physical properties of CO2 change significantly, leading to variations in heat and mass transfer processes, posing challenges to system design and control. In such cases, the system requires complex control logic to determine the operating mode, achieving adaptive adjustment and stable operation of the CO2 heat pump. This includes controlling and regulating various components such as the centrifugal compressor, cooler, and evaporator to ensure stable heating temperatures and efficient energy conversion under different conditions. However, current research is limited, particularly regarding control strategies and optimization methods for CO2 heat pump systems operating under transcritical or supercritical conditions. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump. This method addresses the problems of unstable industrial waste heat temperature, the need to switch between industrial and air heat sources, the large evaporation temperature range of the CO2 heat pump, and the difficulty in switching heat and mass transfer processes in the prior art.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] An adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump, based on an adjustment system comprising:

[0008] The centrifugal compressor has its outlet connected to the hot-side inlet of a gas cooler. The hot-side outlet of the gas cooler is connected to the hot-side inlet of a regenerator. The hot-side outlet of the regenerator is connected to a medium-pressure storage tank. The outlet of the medium-pressure storage tank is connected in parallel to two heating pipes. The outlets of the two heating pipes are connected to the cold-side inlet of the regenerator. The cold-side outlet of the regenerator is connected to the inlet of the centrifugal compressor. The cold-side inlet of the gas cooler is connected to water, and the outlet outputs high-temperature steam.

[0009] An air source evaporator and a waste heat source gas heater are respectively installed on the two heating pipelines. A first electronic expansion valve and a first solenoid valve are installed before the air source evaporator, and a second electronic expansion valve and a second solenoid valve are installed before the waste heat source gas heater. An electronic expansion valve is installed at the inlet of the medium-pressure liquid storage tank. A branch is installed after the outlet of the two heating pipelines. The branch is connected to the inlet of the centrifugal compressor, and a regulating valve is installed on the branch.

[0010] When the air source evaporator is running, the opening of the first electronic expansion valve is adjusted by the centrifugal compressor suction temperature PID controller, so that the suction temperature of the centrifugal compressor reaches the optimized value.

[0011] When the waste heat source gas heater is running, the opening of the second electronic expansion valve is adjusted by the centrifugal compressor suction pressure PID controller, so that the suction pressure of the centrifugal compressor reaches the optimized value.

[0012] During the operation of the air source evaporator or waste heat source gas heater, the opening of the regulating valve is adjusted by the centrifugal compressor exhaust temperature PID controller to achieve the optimized value of high temperature steam temperature.

[0013] During the operation of the air source evaporator or waste heat source gas heater, the opening of the electronic expansion valve is adjusted by the centrifugal compressor exhaust pressure PID controller, so that the outlet exhaust pressure of the centrifugal compressor reaches the optimized value.

[0014] A further improvement of the present invention is that:

[0015] Preferably, when the air source evaporator is running, the first solenoid valve is open, the first electronic expansion valve is in working condition, the second solenoid valve is closed, and the second electronic expansion valve is fully open.

[0016] Preferably, when the waste heat source gas heater is running, the second solenoid valve is open, the second electronic expansion valve is in working condition, the first solenoid valve is closed, and the first electronic expansion valve is fully open.

[0017] Preferably, during the operation of the air source evaporator, the centrifugal compressor suction temperature PID controller obtains the optimized value of the high-temperature steam temperature and the optimized value of the centrifugal compressor suction temperature based on the high-temperature steam temperature setpoint and the actual suction temperature of the centrifugal compressor; by adjusting the opening of the first electronic expansion valve through the centrifugal compressor suction temperature PID controller, the suction temperature of the centrifugal compressor is close to the optimized value.

[0018] Preferably, the centrifugal compressor suction temperature PID controller adopts differential control, and the calculation formula is as follows:

[0019]

[0020] Where ΔT is the difference between the current inhalation temperature and the optimized inhalation temperature, n is the number of calculations, and K is the value of K. P K I and K D These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of K respectively. P =9,K I =0.7, K D =5.

[0021] Preferably, during the operation of the waste heat source gas heater, the centrifugal compressor suction pressure PID controller obtains the optimized value of the high-temperature steam temperature and the optimized value of the suction pressure based on the high-temperature steam temperature setpoint and the actual suction pressure of the centrifugal compressor. The opening of the second electronic expansion valve is adjusted by the centrifugal compressor suction pressure PID controller, so that the suction pressure of the centrifugal compressor is close to the optimized value.

[0022] Preferably, the centrifugal compressor suction pressure PID controller uses differential PID control, and the calculation formula is as follows:

[0023]

[0024] Where ΔP is the difference between the current inspiratory pressure and the optimized inspiratory pressure, n is the number of calculations, and K is the value of K. P K I and K D These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of K respectively. P =2,K I =3,K D =0.4.

[0025] Preferably, during the operation of the air source evaporator or waste heat source gas heater, the optimized and real-time values ​​of the regeneration rate are calculated; the opening of the regulating valve is adjusted by the centrifugal compressor exhaust temperature PID controller, the regeneration rate is adaptively adjusted, and the high-temperature steam temperature approaches the optimized value.

[0026] Preferably, the PID controller for the centrifugal compressor exhaust temperature is calculated using the differential method, and the calculation formula is as follows:

[0027]

[0028] Where ΔT is the difference between the current exhaust temperature and the set exhaust temperature, n is the number of calculations, and K is the number of operations. P K I and K D These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of K respectively. P =7,K I =0.3, K D =0.8.

[0029] Preferably, during the operation of the air source evaporator or waste heat source gas heater, the optimized value of the outlet exhaust pressure of the centrifugal compressor is calculated. Based on the optimized value and the actual value of the exhaust pressure, the opening of the electronic expansion valve is adjusted by the centrifugal compressor exhaust pressure PID controller, so that the exhaust pressure of the centrifugal compressor reaches the target value.

[0030] Preferably, the centrifugal compressor discharge pressure PID controller uses the differential method for calculation, and the calculation formula is as follows:

[0031]

[0032] Where ΔP is the difference between the current exhaust pressure and the optimized exhaust pressure value, n is the number of calculations, and K is the value of ... P K I and K D These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of K respectively. P =0.3, K I =2,K D =0.07.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This invention discloses an adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump. The method includes an air-source evaporator assembly, a waste heat source gas heater assembly, a regenerator assembly, a centrifugal compressor assembly, a gas cooler assembly, a high-temperature water / steam circuit, an electronic expansion valve, a medium-pressure storage tank, a working fluid pump, several temperature and pressure sensors, and solenoid valves. The CO2 heat pump system, based on system requirements and environmental conditions, adjusts the speed of the centrifugal compressor and controls the solenoid valve assembly to switch between air-source heating and industrial waste heat heating modes in real time, corresponding to transcritical and supercritical CO2 cycle conditions respectively. This effectively changes the compressor's compression ratio, achieving adaptive adjustment of the regenerative rate. Furthermore, the operating temperature and pressure of the evaporator and gas cooler are flexibly adjusted to enable rapid and efficient operation in different modes. Combined with a PID control logic algorithm, the system dynamically adjusts the opening and closing of multiple solenoid valves based on the real-time operating status and environmental conditions, achieving precise system control and maximizing system performance optimization. This invention also has the following advantages:

[0035] (1) This invention enables flexible switching from air source to waste heat source and adaptive adjustment of operating parameters in different modes. This switching can better adapt to different operating conditions and improve the applicability and flexibility of the system.

[0036] (2) In this invention, the compression ratio and exhaust temperature of the centrifugal compressor change significantly under these two working modes, resulting in unstable heating temperature. By setting the opening of the bypass regulating valve of the regenerator and supplementing it with a certain control algorithm, the regeneration rate in the regenerator is controlled, thereby maintaining the stability of the exhaust temperature and improving the stability and heating effect of the system.

[0037] (3) Improved stability: The invention is equipped with a regenerator bypass regulating valve, which can effectively control the stability of the exhaust temperature by dynamically and adaptively adjusting the regeneration rate.

[0038] (4) Fast response speed: The system adopts an advanced PID control algorithm, combined with real-time monitoring of the system's working status and environmental conditions, which enables the system to respond quickly and maintain efficient operation.

[0039] (5) This invention can replace traditional methods such as electric heating and primary energy combustion heating in industrial heating below 260°C. It can flexibly utilize air energy and low-temperature waste heat energy below 100°C to provide heating heat below 260°C with an electrothermal conversion efficiency of over 200%, such as steam preparation, and is expected to bring sustainable, efficient and economical heating solutions to the industrial field. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating the adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump according to the present invention.

[0041] Among them, 1-centrifugal compressor; 201-first gas cooler; 202-second gas cooler; 3-regenerator; 4-third electronic expansion valve; 5-medium pressure liquid storage tank; 6-working fluid pump; 7-first electronic expansion valve; 8-second electronic expansion valve; 9-first solenoid valve, used to start and stop 11 air source evaporator; 10-second solenoid valve, used to start and stop 12 waste heat source gas heater; 11-air source evaporator; 12-waste heat source gas heater; 13-regulating valve; 14-first pressure sensor at the outlet of centrifugal compressor; 15-first temperature sensor at the outlet of centrifugal compressor; 16-second pressure sensor; 17-second temperature sensor; 18-third temperature sensor; 19-fourth temperature sensor; 20-fifth temperature sensor; 21-steam supply temperature sensor; 22-high temperature water flash tank; 23-pressurization pump.

[0042] Figure 2 This is a schematic diagram of a control system module for an adaptive adjustment method of the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump. Detailed Implementation

[0043] The present invention will now be described in further detail with reference to the accompanying drawings:

[0044] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] This invention discloses an adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump, which can be used for industrial waste heat recovery, heating and steam supply.

[0046] See Figure 1 The adjustment method of the present invention is based on the following system, including a centrifugal compressor 1, a first gas cooler 201, a second gas cooler 202, a high-temperature water flash tank 22, a regenerator 3, a medium-pressure liquid storage tank 5, an air source evaporator 11, and a waste heat source gas heater 12. The outlet of the centrifugal compressor 1 is connected to the hot side inlet of the first gas cooler 201, the hot side outlet of the first gas cooler 201 is connected to the hot side inlet of the second gas cooler 202, the hot side outlet of the second gas cooler 202 is connected to the hot side inlet of the regenerator 3, the hot side outlet of the regenerator 3 is connected to the inlet of the medium-pressure liquid storage tank 5, the outlet of the medium-pressure liquid storage tank 5 is connected to the working fluid pump 6, the outlet of the working fluid pump 6 is connected to the air source evaporator 11 and the waste heat source gas heater 12 respectively, the outlets of the air source evaporator 11 and the waste heat source gas heater 12 are connected together to the cold side inlet of the regenerator 3, and the cold side outlet of the regenerator 3 is connected to the centrifugal compressor 1.

[0047] A second pressure sensor 16 and a second temperature sensor 17 are installed on the common connecting pipe between the outlet of the air source evaporator 11 and the waste heat source gas heater 12 and the cold side inlet of the regenerator 3. A branch is installed on the connecting pipe after the second pressure sensor 16 and the second temperature sensor 17, and a regulating valve 13 is installed on the branch.

[0048] Tap water is supplied through a booster pump 23. The outlet of the booster pump 23 is connected to the cold side inlet of the second gas cooler. The cold side outlet of the second gas cooler 202 is connected to the high-temperature water flash tank 22. The outlet of the high-temperature water flash tank 22 is connected to the cold side inlet of the first gas cooler 201. The cold side outlet of the first gas cooler 202 is connected to the high-temperature steam supply pipeline. A temperature sensor 21 is installed at the cold side outlet of the first gas cooler 201.

[0049] A first temperature sensor 15 and a pressure sensor 14 are connected to the outlet of centrifugal compressor 1 to detect the temperature and pressure of the CO2 working fluid. The working fluid is then introduced into a first gas cooler 201 and a second gas cooler 202. The outlet of the second gas cooler 202 is connected to a fifth temperature sensor 20, followed by a regenerator 3 and an electronic expansion valve 4. The electronic expansion valve 4 is located at the inlet of the medium-pressure storage tank 5. After the working fluid is introduced into the medium-pressure storage tank 5, it passes through a working fluid pump 6, which pumps the CO2 working fluid into the heat-absorbing side. The heat-absorbing side has two modes: First, CO2 flows through a first electronic expansion valve 7 and a first solenoid valve 9 before being introduced into an air-source evaporator 11 to absorb heat from the air side, and then enters the regenerator 3. Second, CO2 flows through a second electronic expansion valve 8 and a second solenoid valve 10 before being introduced into a waste heat source gas heater 12 to absorb energy from industrial waste heat, and finally enters the regenerator 3. A second temperature sensor 17 and a second pressure sensor 16 are connected to the inlet of the regenerator 3 to measure the temperature and pressure of the inlet CO2 working fluid. A regulating valve is installed at the inlet and outlet of the regenerator 3 to regulate the bypass flow of the CO2 working fluid, thereby significantly adjusting the regeneration rate.

[0050] The system is equipped with two gas coolers (first and second). In addition to providing heat to the outside, the high-temperature water / steam circuit can also supply steam to the outside. Tap water is pressurized by the booster pump 23 and enters the second gas cooler to exchange heat with the CO2 working fluid. After that, it is stored in the high-temperature water flash tank 22. The high-temperature steam at the top then enters the first gas cooler to exchange heat with the high-temperature CO2 working fluid. After reaching the steam supply temperature, it is supplied to the outside.

[0051] When switching between the two modes, during transcritical CO2 circulation, the first solenoid valve 9 is open, the first electronic expansion valve 7 is in operation, the second solenoid valve 10 is closed, and the second electronic expansion valve 8 is fully open (to prevent throttling and safety issues during mode switching). During supercritical CO2 circulation, the second solenoid valve 10 is open, the second electronic expansion valve 8 is in operation, the first solenoid valve 9 is closed, and the first electronic expansion valve 7 is fully open.

[0052] During the transcritical CO2 cycle, the opening of the electronic expansion valve 4 controls the outlet pressure of the centrifugal compressor 1 in the entire system, i.e., the pressure value detected by the pressure sensor 14; the first electronic expansion valve 7 controls the superheat of the air source evaporator outlet, i.e., the difference between the temperature value detected by the second temperature sensor 17 and the saturation temperature corresponding to the pressure collected by the second pressure sensor 16.

[0053] During the supercritical CO2 cycle, the opening degree of the electronic expansion valve 4 controls the outlet pressure of the centrifugal compressor 1, i.e., the pressure value detected by the pressure sensor 14; the opening degree of the second electronic expansion valve 8 controls the outlet pressure of the waste heat source gas heater, i.e., the pressure value detected by the second pressure sensor 16.

[0054] Adaptive control methods for different modes:

[0055] Adaptive adjustment of exhaust temperature and system regenerative rate: The regenerative rate is defined as R h =(T 18 -T 17 ) / (T 20 -T 17 ), R h It also depends on the ambient temperature T0 or the residual heat temperature T. 12 Exhaust temperature T 15 It is related to factors such as return water temperature. The actual steam supply temperature T is used. 21 With stability as the sole objective, a correlation model is established between the regenerative rate and these variables, with the correlation equation being R0. h =f(T) 17 T 18 T 20 T0, T 12 T 15 Adjust T according to different modes 17 T 18 T 20 T0, T 12 T 15 The parameters, with the opening degree of the bypass regulating valve 13 as the input variable, and the controller output exhaust temperature T, are used to determine the exhaust temperature. 15 The set value, based on the system and T 21 Real-time feedback allows for online adjustment of the three parameters K of the PID module. P K i K d The system completes one cycle. If the temperature difference between the exhaust gas before and after the cycle exceeds the set accuracy value, this difference is used as an input parameter to the PID controller. The PID controller calculates the control quantity based on the error of the input parameter, adjusts the centrifugal compressor exhaust temperature, and regulates the regenerative rate in real time to ensure the actual steam supply temperature T is maintained. 21 A stable state has been reached.

[0056] Adaptive adjustment of discharge pressure: centrifugal compressor discharge pressure (P) 14 The phase state of the CO2 working fluid, ambient temperature (T0), or waste heat source temperature (T) 12 The temperature is related to the evaporation temperature, condensation temperature, and the inlet and outlet temperatures of the circulating water. With the goal of improving the coefficient of performance (COP) of the heat pump system, a correlation model is established between the exhaust pressure and these variables, with the correlation equation being P. 14 =f(T0, T) 12 (C). Taking the opening degree of electronic expansion valve 4 as the input variable, the controller outputs the set value of the exhaust pressure, and the three parameters K of the PID module are tuned according to the dynamic characteristics of the system. P K i K d Based on the model-driven control loop, the steady-state limit is determined, and K is adjusted. P The value of [value] causes the system to exhibit steady-state oscillations. After one cycle, if the difference in exhaust pressure before and after the cycle is greater than the set precision value, this difference is used as an input parameter to the PID controller. The PID controller calculates the control quantity based on the error of the input parameter and adjusts the exhaust pressure at the centrifugal compressor outlet. As the PID controller parameters are set appropriately, the calculated exhaust pressure will get closer and closer to the assumed target value until the absolute value of the difference is less than the set precision. By adjusting multiple parameters according to different operating conditions, and supplementing this with real-time adjustment of the exhaust pressure by the PID controller, the system performance can be optimized.

[0057] Adaptive adjustment of suction pressure in supercritical mode: centrifugal compressor suction pressure (P) 16 ) and waste heat source temperature (T 12 ), evaporation temperature, condensation temperature, suction temperature (T) 17 Related to variables such as suction pressure, etc. With the goal of improving the coefficient of performance (COP) of the heat pump system, a correlation model is established between suction pressure and these variables, with the correlation equation being P... 16 =f(T) 12 T 17 Using the opening degree of the second electronic expansion valve 8 as the input variable, the controller outputs the set value of the centrifugal compressor suction pressure, and tunes the three parameters K of the PID module according to the system dynamic characteristics. P K i K d After one cycle, if the difference in suction pressure before and after the cycle is greater than the set accuracy value, this difference is used as an input parameter and fed into the PID controller. The PID controller calculates the control quantity based on the error of the input parameter and adjusts the suction pressure of the centrifugal compressor to achieve optimal system performance.

[0058] Adaptive regulation of intake temperature in transcritical mode: centrifugal compressor intake temperature (T) 17 ) and waste heat source temperature (T12 Inspiratory pressure (P) 16 The evaporation temperature and condensation temperature are related. With the goal of improving the coefficient of performance (COP) of the heat pump system, a correlation model is established between the suction temperature and these variables, with the correlation equation being T. 17 =f(T) 12 P 16 Using the opening degree of the first electronic expansion valve 7 as the input variable, the controller outputs the set value of the centrifugal compressor suction temperature, and tunes the three parameters K of the PID module according to the system dynamic characteristics. P K i K d After one cycle, if the difference in suction temperature before and after the cycle is greater than the set accuracy value, this difference is used as an input parameter and fed into the PID controller. The PID controller calculates the control quantity based on the error of the input parameter and adjusts the suction temperature of the centrifugal compressor to achieve optimal system performance.

[0059] The system's PID setting scheme optimizes the control of exhaust temperature, regenerative rate, exhaust pressure, and intake pressure using an electronic expansion valve opening adjustment method based on PID control. The electronic expansion valve opening can be adjusted between 0-100%. During operation, the optimal value under the current system operating conditions is calculated to set the PID controller's setpoint. Simultaneously, pressure or temperature sensors are used to measure the centrifugal compressor's exhaust pressure, intake temperature, and intake pressure as measured values ​​for the PID controller. The opening of the expansion valve is adjusted to keep the system operating under the set conditions. The first electronic expansion valve 7 is dynamically adjusted to maintain the intake temperature T of the centrifugal compressor 1. 17 To achieve the optimized value; dynamically adjust the second electronic expansion valve 8 to ensure that the suction pressure P of the centrifugal compressor 1 is optimized. 16 To achieve the optimized value; dynamically adjust the electronic expansion valve 4 to ensure the centrifugal compressor outlet discharge pressure P 14 To achieve the optimized value; the centrifugal compressor outlet discharge temperature T is controlled by adjusting the opening of the bypass regulating valve 13. 15 Dynamic adjustments were made to optimize the heat recovery rate, and the performance of the heat pump system reached its optimal value, with the actual steam supply temperature T... 21 A stable state has been reached.

[0060] The aforementioned PID system regulates the transcritical / supercritical CO2 industrial high-temperature steam heat pump system through four PID controllers: a centrifugal compressor suction temperature PID controller, with the input being the centrifugal compressor suction temperature T. 17 The output is the opening degree of the first electronic expansion valve 7; the centrifugal compressor suction pressure PID controller has the input being the centrifugal compressor suction pressure P. 16 The output is the opening degree of the second electronic expansion valve 8; the centrifugal compressor discharge temperature PID controller has the centrifugal compressor discharge temperature T as its input.15 The output is the opening degree of regulating valve 13; the centrifugal compressor discharge pressure PID controller has the input being the centrifugal compressor discharge pressure P. 16 The output is the opening degree of the electronic expansion valve 4.

[0061] In the air-source heat pump cycle, the system operates in a transcritical CO2 cycle. The first solenoid valve 9 is open, the first electronic expansion valve 7 is operational, the second solenoid valve 10 is closed, and the second electronic expansion valve 8 is fully open. The first electronic expansion valve 7 controls the temperature at the outlet of the air-source evaporator, thereby controlling the superheat at the inlet of the centrifugal compressor. The CO2 working fluid absorbs heat in the air-source evaporator 11, passes through the regenerator 3 and centrifugal compressor 1, and continuously releases heat through the first gas cooler A and the second gas cooler B. It then flows through the regenerator 3 and the electronic expansion valve 4 to the storage tank 5, and finally returns to the air-source evaporator 11 via the working fluid pump 6, the first electronic expansion valve 7, and the first solenoid valve 9, completing the transcritical CO2 cycle. On the water / steam side, tap water is pressurized by a booster pump and enters the second gas cooler B to exchange heat with the CO2 working fluid. It is then stored in a high-temperature water flash tank. The high-temperature steam at the top re-enters the first gas cooler A to exchange heat with the high-temperature CO2 working fluid, reaching the supply steam temperature before being supplied externally. The system's coefficient of performance (COP) and steam supply temperature (T) are used as the basis for determining the system's coefficient of 21 As feedback signals, the optimal discharge and suction pressures of the centrifugal compressor are used as reference values ​​for the PID controller. The optimal system operating state is achieved by adjusting the opening of the electronic expansion valve. By changing the opening of the bypass regulating valve 13, online parameter adjustments are made based on real-time system feedback, and the regenerative rate and actual steam supply temperature T are adaptively adjusted in real time. 21 A stable state has been reached.

[0062] The formula for calculating COP is as follows:

[0063] COP = Q1 / Q2 (1)

[0064] Q1=c*m*(T 15 -T 20 ), which is the heating capacity of the heat pump;

[0065] Q2 = Input power;

[0066] In this invention, the coefficient of performance (COP) / heat output and the steam supply temperature (T) of the heat pump system are improved. 21 With this as the ultimate goal, and using it as feedback, the discharge and suction pressures of the centrifugal compressor are adjusted to maintain the steam supply temperature T. 21 To reach stability.

[0067] In the industrial waste heat source heat pump cycle, the system operates in a supercritical CO2 cycle. The second solenoid valve 10 is open, the second electronic expansion valve 8 is operational, the first solenoid valve 9 is closed, and the first electronic expansion valve 7 is fully open. The second electronic expansion valve 8 controls the outlet pressure of the waste heat source gas heater. The CO2 working fluid absorbs heat in the waste heat source gas heater 12, then passes through the regenerator 3 and centrifugal compressor 1, releases heat in the gas cooler 2, flows through the regenerator 3 and electronic expansion valve 4, reaches the storage tank 5, and finally returns to the waste heat source gas heater 12 via the working fluid pump 6, the second electronic expansion valve 8, and the second solenoid valve 10, completing the supercritical CO2 cycle. Similarly, on the water / steam side, tap water is pressurized by a booster pump, enters the second gas cooler to exchange heat with the CO2 working fluid, and is then stored in a high-temperature water flash tank. The high-temperature steam at the top then enters the first gas cooler to exchange heat with the high-temperature CO2 working fluid, reaching the supply steam temperature before being supplied externally. The system's heating COP and supply steam temperature T are used as the basis for this process. 21 As feedback signals, the optimal discharge and suction pressures of the centrifugal compressor are used as reference values ​​for the PID controller. The optimal system operating state is achieved by adjusting the opening of the electronic expansion valve. By changing the opening of the bypass regulating valve 13, online parameter adjustments are made based on real-time system feedback, and the regenerative rate and actual steam supply temperature T are adaptively adjusted in real time. 21 A stable state has been reached.

[0068] When switching between the two modes, pressure sensor 14 monitors the pressure ratio of the centrifugal compressor. If the pressure ratio of the centrifugal compressor changes too much, the discharge temperature of the centrifugal compressor will change drastically. By adjusting the opening of the bypass regulating valve 13, the regeneration rate of the regenerator is adjusted to maintain a stable discharge temperature. When the centrifugal compressor is running, the setpoint of the PID controller is set by calculating the optimal value under the current operating conditions of the system. At the same time, the discharge pressure and suction temperature of the centrifugal compressor are measured by pressure or temperature sensors as the measured values ​​of the PID controller. The opening of the expansion valve is adjusted to make the system operate under the set conditions.

[0069] See Figure 2 The present invention proposes the following performance optimization and control method for the aforementioned transcritical / supercritical CO2 industrial high-temperature steam heat pump:

[0070] Intake temperature control

[0071] After the air source heat pump starts operating, the first step is to determine the steam supply temperature T. 21 and centrifugal compressor suction temperature T 17 Calculate the corresponding optimized steam supply temperature. When the steam supply temperature T... 21 When the temperature is below 20℃, the steam supply temperature T 21 and intake temperature T 17 The optimized formula is:

[0072] T21,opt =(η+12)(0.7T) 11 +0.051T 23 +14.8) (2)

[0073] T 17,opt =(η+7)(5T) 11 +0.62T 21 +0.35) (3)

[0074] When the steam supply temperature T 21 When the temperature is above 25℃, the steam supply temperature T 21 and intake temperature T 17 The optimized formula is:

[0075] T 21,opt =(η+9)(0.68T) 11 +0.047T 23 +11.3) (4)

[0076] T 17,opt =(η+5)(4T) 11 +0.37T 21 +0.58) (5)

[0077] Where η is the regenerator efficiency, T 11 T represents the temperature of the heat source. 23 T represents the inlet water temperature. 17 This refers to the intake temperature.

[0078] The second step is based on the calculated intake temperature T. 17,opt With real-time measurement of inhalation temperature T 17 The opening degree of the first electronic expansion valve 7 is controlled. When T 17 >(T 17,opt When +ε), increase the opening of the first electronic expansion valve 7; when T 17 <(T) 17，opt When -ε), reduce the opening of the first electronic expansion valve 7; when (T 17,opt -ε)≤T 17 ≤(T 17,opt When +ε), the opening of the electronic expansion valve remains unchanged. ε is the allowable control error.

[0079] The opening control of the electronic expansion valve 7 uses a PID controller to ensure that the intake temperature T... 17 The value is close to the optimal value. Differential PID control is used, and the calculation formula is as follows:

[0080]

[0081] Where ΔT is the difference between the current inhalation temperature and the set inhalation temperature, n is the number of calculations, and K is the value of K.P K I and K D These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of K respectively. P =9,K I =0.7, K D =5.

[0082] Third, if the system is not shut down, a delay is applied, then the process returns to the first step and enters the next operation control loop. The performance optimization control logic continues to run in a loop until the system shuts down.

[0083] Inspiratory pressure control

[0084] After the waste heat source heat pump starts operating, the first step is to determine the steam supply temperature T. 21 and centrifugal compressor suction pressure P 16 Calculate the corresponding optimized steam supply temperature. When the steam supply temperature T... 21 When the temperature is below 20℃, the steam supply temperature T 21 and inhalation pressure P 16 The optimized formula is:

[0085] T 21,opt =(η+12)(0.7T) 12 +0.051T 23 +14.8) (7)

[0086] P 16,opt =(η+7)(5T) 12 +0.62T 21 +0.35) (8)

[0087] When the steam supply temperature T 21 When the temperature is above 25℃, the steam supply temperature T 21 and inhalation pressure P 16 The optimized formula is:

[0088] T 21,opt =(η+12)(0.7T) 12 +0.051T 23 +14.8) (9)

[0089] P 16,opt =(η+7)(5T) 12 +0.62T 21 +0.35) (10)

[0090] Where η is the regenerator efficiency, T 12 T represents the temperature of the heat source. 23 P represents the inlet water temperature. 16 This is the inhalation pressure.

[0091] The second step is based on the calculated inhalation pressure P. 16,opt With real-time measurement of inspiratory pressure P 16 The opening degree of the second electronic expansion valve 8 is controlled. When P 16 >(P 16,opt When +ε), increase the opening of the electronic expansion valve 8; when P 16 <(P 16,opt When -ε), decrease the opening of the electronic expansion valve; when (P 16,opt -ε)≤P 16 ≤(P 16,opt When +ε), the opening of the electronic expansion valve remains unchanged. ε is the allowable control error.

[0092] The electronic expansion valve's 8-degree opening control uses a PID controller to ensure the intake pressure is close to the optimized value. Differential PID control is employed, and the calculation formula is as follows:

[0093]

[0094] Where ΔP is the difference between the current inspiratory pressure and the set inspiratory pressure, n is the number of calculations, and K is the number of operations. P K I and K D These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of K respectively. P =21, K I =8,K D =3.

[0095] Third, if the system is not shut down, a delay is applied, then the process returns to the first step and enters the next operation control loop. The performance optimization control logic continues to run in a loop until the system shuts down.

[0096] Optimization of exhaust pressure

[0097] The first step is to determine the exhaust pressure P. 14 Calculate the corresponding optimized exhaust pressure value. When the exhaust pressure P 14 When the pressure is less than 25 MPa, the exhaust pressure P 14 The optimized formula is:

[0098] P 14,opt =0.85P 16 +(1.2R h +0.007n0)(1.2T 17 +0.5T 21 +37) (12)

[0099] When the exhaust pressure P 14 When the pressure is greater than 30 MPa, the exhaust pressure P 14 The optimized formula is:

[0100] P 14,opt =0.63P 16 +(0.85R h +0.005n0)(1.1T 17 +0.2T 21 +54) (13)

[0101] Among them, P 14 P is the exhaust pressure. 16 R is the inspiratory pressure. h Where n is the regenerative rate, n0 is the centrifugal compressor speed, and T is the regenerative rate. 17 T is the intake temperature. 21 This refers to the steam supply temperature.

[0102] The second step is based on the calculated exhaust pressure P. 14,opt With real-time measurement of exhaust pressure P 14 The opening degree of the electronic expansion valve 4 is controlled. When P 14 >(P 14,opt When +ε), increase the opening of electronic expansion valve 4; when P 14 <(P 14,opt When -ε), decrease the opening of the electronic expansion valve; when (P 14,opt -ε)≤P 14 ≤(P 14,opt When +ε), the opening of the electronic expansion valve remains unchanged. ε is the allowable control error.

[0103] The third step is to use a PID controller to bring the exhaust pressure close to the set value.

[0104] The centrifugal compressor discharge pressure PID controller uses the differential method for calculation, and the calculation formula is as follows:

[0105]

[0106] Where ΔP is the difference between the current exhaust pressure and the optimized exhaust pressure value, n is the number of calculations, and K is the value of ... P K I and K D These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of K respectively. P =0.3, K I =2,K D =0.07.

[0107] exhaust temperature T 15 Optimization, and adaptive adjustment of the regenerative rate:

[0108] The first step is to define the regenerative rate as R. h =(T 18 -T17 ) / (T 20 -T 17 Based on this formula, the corresponding heat recovery rate can be calculated. When the heat recovery rate is less than 20%, the optimized formula for the heat recovery rate is:

[0109] R h,opt =(-0.035T) 15 (T) 18 -T 17 (1.2T) 21 +0.7T 11 ) / (T 20 -T 17 (15)

[0110] When the heat recovery rate is greater than 50%, the optimized formula for the heat recovery rate is:

[0111] R h,opt =(-0.048T) 15 (T) 18 -T 17 (0.8T) 21 +0.5T 11 ) / (T 20 -T 17 (16)

[0112] Among them, T 18 T is the inlet temperature of the centrifugal compressor. 17 T is the intake temperature. 20 T is the air-cooled outlet temperature. 21 For steam supply temperature, T 11 The heat source temperature (T during supercritical cycles) 12 ), T 15 This refers to the exhaust temperature.

[0113] The second step is to optimize the regeneration rate R based on the calculated value. h,opt With real-time regeneration rate R h =(T 18 -T 17 ) / (T 20 -T 17 The opening degree of regulating valve 13 is used to control the exhaust temperature T. 15 This allows the high-temperature steam temperature to approach the set value. When R h >(R h,opt When +ε), increase the opening of regulating valve 13; when R h <(R) h,opt When -ε), reduce the opening of regulating valve 13; when (R h,opt -ε)≤R h ≤(R h,opt When +ε), the opening of regulating valve 13 remains unchanged. ε is the allowable control error.

[0114] The third step is to use a PID controller to ensure that the heat recovery rate is within the allowable range.

[0115] The opening degree of regulating valve 13 is controlled by a centrifugal compressor exhaust temperature PID controller. The centrifugal compressor exhaust temperature PID controller uses the differential method for calculation, and the calculation formula is as follows:

[0116]

[0117] Where ΔT is the current exhaust temperature T 15 With exhaust temperature T 15 The difference between the set values, where n is the number of operations, and K P K I and K D These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of K respectively. P =7,K I =0.3, K D =0.8.

[0118] Fourth, if the system is not shut down, a delay is applied, then the process returns to the first step and enters the next operation control loop. The performance optimization control logic continues to run in a loop until the system shuts down.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for adaptive adjustment of the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump, characterized in that, Based on the regulation system, the regulation system includes: Centrifugal compressor (1), the outlet of the centrifugal compressor (1) is connected to the hot side inlet of a gas cooler, the hot side outlet of the gas cooler is connected to the hot side inlet of a regenerator (3), the hot side outlet of the regenerator (3) is connected to a medium-pressure storage tank (5), the outlet of the medium-pressure storage tank (5) is connected to two heating pipes in parallel, the outlets of the two heating pipes are connected to the cold side inlet of the regenerator (3), the cold side outlet of the regenerator (3) is connected to the inlet of the centrifugal compressor (1); the cold side inlet of the gas cooler is connected to water, and the outlet outputs high-temperature steam; An air source evaporator (11) and a waste heat source gas heater (12) are respectively installed on the two heating pipelines. A first electronic expansion valve (7) and a first solenoid valve (9) are installed before the air source evaporator (11), and a second electronic expansion valve (8) and a second solenoid valve (10) are installed before the waste heat source gas heater (12). An electronic expansion valve (4) is installed at the inlet of the medium-pressure liquid storage tank (5). A branch is installed after the outlet of the two heating pipelines. The branch is connected to the inlet of the centrifugal compressor (1), and a regulating valve (13) is installed on the branch. When the air source evaporator (11) is running, the opening of the first electronic expansion valve (7) is adjusted by the centrifugal compressor suction temperature PID controller, and the suction temperature of the centrifugal compressor (1) reaches the optimized value. When the waste heat source gas heater (12) is running, the opening of the second electronic expansion valve (8) is adjusted by the centrifugal compressor suction pressure PID controller, and the suction pressure of the centrifugal compressor (1) reaches the optimized value. During the operation of the air source evaporator (11) or the waste heat source gas heater (12), the opening of the regulating valve (13) is adjusted by the centrifugal compressor exhaust temperature PID controller, and the high temperature steam temperature reaches the optimized value. During the operation of the air source evaporator (11) or the waste heat source gas heater (12), the opening of the electronic expansion valve (4) is adjusted by the centrifugal compressor exhaust pressure PID controller, and the outlet exhaust pressure of the centrifugal compressor (1) reaches the optimized value. During operation, the setpoint of the PID controller is set by calculating the optimal value under the current operating conditions of the system. At the same time, the discharge pressure, suction temperature and suction pressure of the centrifugal compressor are measured by pressure or temperature sensors as the measured values ​​of the PID controller. The opening of the expansion valve is adjusted to make the system operate under the set conditions.

2. The adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump according to claim 1, characterized in that, When the air source evaporator (11) is running, the first solenoid valve (9) is open, the first electronic expansion valve (7) is in working condition, the second solenoid valve (10) is closed, and the second electronic expansion valve (8) is fully open.

3. The adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump according to claim 1, characterized in that, When the waste heat source gas heater (12) is running, the second solenoid valve (10) is open, the second electronic expansion valve (8) is in working condition, the first solenoid valve (9) is closed, and the first electronic expansion valve (7) is fully open.

4. The adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump according to claim 1, characterized in that, During the operation of the air source evaporator (11), the centrifugal compressor suction temperature PID controller obtains the high-temperature steam temperature optimization value and the centrifugal compressor suction temperature optimization value based on the high-temperature steam temperature set value and the actual suction temperature of the centrifugal compressor; by adjusting the opening of the first electronic expansion valve (7) through the centrifugal compressor suction temperature PID controller, the suction temperature of the centrifugal compressor (1) approaches the optimization value.

5. The adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump according to claim 4, characterized in that, The centrifugal compressor suction temperature PID controller uses differential control, and the calculation formula is as follows: in, This is the difference between the current inhalation temperature and the optimized inhalation temperature. n The number of operations. , and These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of respectively. , , .

6. The adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump according to claim 1, characterized in that, During the operation of the waste heat source gas heater (12), the centrifugal compressor suction pressure PID controller obtains the optimized value of high temperature steam temperature and the optimized value of suction pressure based on the high temperature steam temperature set value and the actual suction pressure of the centrifugal compressor (1). The opening degree of the second electronic expansion valve (8) is adjusted by the centrifugal compressor suction pressure PID controller, and the suction pressure of the centrifugal compressor (1) approaches the optimized value.

7. The adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump according to claim 6, characterized in that, The centrifugal compressor suction pressure PID controller uses differential PID control, and the calculation formula is as follows: in, This is the difference between the current inspiratory pressure and the optimized inspiratory pressure value. n The number of operations. , and These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of respectively. , , .

8. The adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump according to claim 1, characterized in that, During the operation of the air source evaporator (11) or the waste heat source gas heater (12), the optimized value and real-time value of the regeneration rate are calculated; the opening of the regulating valve (13) is adjusted by the centrifugal compressor exhaust temperature PID controller, the regeneration rate is adaptively adjusted, and the high temperature steam temperature is close to the optimized value.

9. The adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump according to claim 8, characterized in that, The centrifugal compressor exhaust temperature PID controller uses the differential method for calculation, and the calculation formula is as follows: （17） in, The difference between the current exhaust temperature and the set exhaust temperature. n The number of operations. , and These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of respectively. , , .

10. The adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump according to claim 1, characterized in that, During the operation of the air source evaporator (11) or the waste heat source gas heater (12), the optimized value of the outlet exhaust pressure of the centrifugal compressor (1) is calculated. Based on the optimized value and the actual value of the exhaust pressure, the opening of the electronic expansion valve (4) is adjusted by the centrifugal compressor exhaust pressure PID controller, and the exhaust pressure of the centrifugal compressor (1) reaches the target value.

11. The adaptive adjustment method for the regenerative rate of a transcritical / supercritical CO2 industrial high-temperature steam heat pump according to claim 10, characterized in that, The centrifugal compressor discharge pressure PID controller uses the differential method for calculation, and the calculation formula is as follows: （14） in, This is the difference between the current exhaust pressure and the optimized exhaust pressure value. n The number of operations. , and These are the proportional control coefficient, integral control coefficient, and derivative control coefficient, with values ​​of respectively. , , .

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