A dual cycle organic rankine cycle power generation system with dual heat source collaborative control

Abstract

The application relates to the technical field of engine devices applying special working fluid or circulation, and discloses a double-circulation organic Rankine cycle power generation system and method with double-heat-source cooperative control. The system comprises high-temperature and low-temperature closed cycles which are isolated from each other and use R245fa as working medium; each cycle makes R245fa pressurized by a working medium pump, vaporized by absorbing heat in an evaporator, expanded to do work in an expander, and returned to the working medium pump after being condensed in a condenser, and drives a generator to generate power. Dry hot rock geothermal fluid supplies heat to a first evaporator and a preheater in sequence, and industrial waste heat fluid supplies heat to a second evaporator. A control module adjusts a waste heat inlet adjusting valve V1 according to actual power generation power, and determines the supercooling degree according to the temperature and pressure of the working medium outlet of the preheater; when the supercooling degree is not higher than a threshold value, the opening degree of a geothermal bypass adjusting valve V2 is increased, so that the working medium at the preheater outlet is kept in liquid phase. The application realizes step utilization of geothermal heat and industrial waste heat, and compensates for geothermal input fluctuation.

Description

Technical Field

[0001] This application relates to the technical field of engine devices that utilize special working fluids or circulation, and more specifically to dual-cycle organic Rankine cycle power generation systems. Background Technology

[0002] The Organic Rankine Cycle (ORC) typically utilizes a low-boiling-point organic working fluid to absorb heat from a medium- or low-temperature heat source, causing the organic working fluid to vaporize and drive an expander to perform work. The organic working fluid is then returned to the evaporation process through condensation and pressurization. Compared to the Rankine Cycle, which uses water vapor as the working fluid, the Organic Rankine Cycle is more adaptable to relatively low-temperature heat sources such as geothermal energy and industrial waste heat.

[0003] Low-temperature dry hot rock geothermal energy is a highly promising clean and renewable energy source, but existing single-source organic Rankine cycle (ORC) power generation systems face significant bottlenecks in practical applications. Affected by geological conditions and fluctuations in injection-production pressure differentials, the output flow and temperature of dry hot rock geothermal energy exhibit strong volatility: during peak heat source periods, the heat exchange capacity of a single ORC unit cannot match the geothermal output power, resulting in a large amount of excess geothermal heat that cannot be absorbed and is directly emitted, causing serious energy waste; while during periods of heat source fluctuation, the geothermal output power is insufficient to support the continuous and stable operation of two ORC units, leading to frequent system start-ups and shutdowns, large fluctuations in power generation, and a significant decrease in both power generation efficiency and operational reliability.

[0004] Currently, existing technologies for mixed working fluid ORC systems suffer from drawbacks such as component misalignment, high working fluid loss rates, and high maintenance costs. Dual-pressure single-cycle systems are prone to cross-contamination of working fluids between high and low pressure sides, leading to a decrease in cycle efficiency. The industry has yet to develop a mature solution that addresses the fluctuating characteristics of dry hot rock geothermal energy by introducing industrial waste heat as a dynamic compensation heat source and simultaneously resolving the issues of surplus heat absorption and power generation fluctuations through dual-cycle coupling. This approach fails to balance geothermal utilization efficiency with system operational stability.

[0005] Therefore, there is an urgent need in this field to develop a dual-cycle organic Rankine cycle power generation system with dual heat source coordinated control, which can solve the problems of unstable power generation and waste of geothermal energy caused by fluctuations in geothermal input heat. Summary of the Invention

[0006] The purpose of this application is to provide a dual-cycle organic Rankine cycle power generation system with dual heat source coordinated control, which solves the problems of unstable power generation and waste of geothermal energy caused by fluctuations in geothermal input heat.

[0007] This application provides a dual-cycle organic Rankine cycle power generation system with dual heat source coordinated control, including a high-temperature organic Rankine cycle system, a low-temperature organic Rankine cycle system, a geothermal loop, an industrial waste heat loop, and a control module; wherein... The high-temperature organic Rankine cycle includes a first working fluid pump, a first evaporator, a first expander, and a first condenser connected in sequence to form a first closed working fluid loop; and the high-temperature organic Rankine cycle system also includes a first generator connected to the first expander; The low-temperature organic Rankine cycle includes a second working fluid pump, a preheater, a second evaporator, a second expander, and a second condenser connected in sequence to form a second closed working fluid loop; and a second generator connected to the second expander. The first closed working fluid loop and the second closed working fluid loop are isolated from each other and both use R245fa as the circulating working fluid. The geothermal circuit is configured such that the dry hot rock geothermal fluid flows sequentially through the heat source side of the first evaporator and the heat source side of the preheater before being discharged from the preheater. The geothermal circuit also includes a bypass branch that bypasses the heat source side of the preheater. A geothermal bypass regulating valve V2 is installed on the bypass branch, and the bypass branch is configured to regulate the flow rate of the dry hot rock geothermal fluid entering the preheater. The industrial waste heat circuit is configured such that the industrial waste heat fluid flows through the heat source side of the second evaporator via a waste heat inlet regulating valve V1 before being discharged. The control module is connected to the first generator, the second generator, the waste heat inlet regulating valve V1, the geothermal bypass regulating valve V2, and temperature and pressure sensing elements located at the working fluid outlet of the preheater. It is configured to: adjust the waste heat inlet regulating valve V1 based on the difference between the actual power output of the second generator and the set power output, thereby compensating for fluctuations in the flow rate of the dry hot rock geothermal fluid using industrial waste heat input; and adjust the outlet temperature T measured by the temperature sensing element. o The outlet pressure P measured by the pressure detection element o And R245fa at the outlet pressure P o The saturation temperature T below sat (Po), determine the subcooling ΔT at the working fluid outlet of the preheater. sc =T sat (Po)-T o And in the supercooling ΔT sc When the temperature is below the preset subcooling threshold, the opening of the geothermal bypass regulating valve V2 is increased to reduce the flow rate of the dry hot rock geothermal fluid flowing through the preheater, so that R245fa at the working fluid outlet of the preheater remains in the liquid phase. The regulation of the waste heat inlet regulating valve V1 and the regulation of the geothermal bypass regulating valve V2 are performed independently with the actual power generation and the subcooling as feedback quantities, respectively.

[0008] In another preferred embodiment, the preset subcooling threshold is 1-2℃, and there is no fixed value. It needs to be determined according to the system design and resistance loss of different projects.

[0009] In another preferred embodiment, the control module is configured to increase the opening of the waste heat inlet regulating valve V1 when the actual power output of the second generator is less than the set power output, and is configured to decrease the opening of the waste heat inlet regulating valve V1 when the actual power output of the second generator is higher than the set power output.

[0010] In another preferred embodiment, the preheater is used to preheat the liquid R245fa after it has been pressurized by the second working fluid pump, and the second evaporator is used to use the industrial waste heat fluid to further heat up and vaporize the preheated R245fa and form steam for the expansion of the second expander.

[0011] In another preferred embodiment, the preheater is located downstream of the second working fluid pump and upstream of the second evaporator.

[0012] In another preferred embodiment, the bypass branch branches off between the heat source side outlet of the first evaporator and the heat source side inlet of the preheater, and merges into the geothermal circuit downstream of the heat source side outlet of the preheater.

[0013] In another preferred embodiment, the control module is further configured to reduce or maintain the opening of the geothermal bypass regulating valve V2 when the subcooling degree is greater than the preset subcooling degree threshold.

[0014] In another preferred embodiment, the dry hot rock geothermal fluid enters the heat source side inlet of the first evaporator from the geothermal inlet, and the temperature of the dry hot rock geothermal fluid entering the heat source side inlet of the first evaporator is 120-180°C.

[0015] In another preferred embodiment, the temperature of the industrial waste heat fluid entering the heat source side inlet of the second evaporator is 80-150°C.

[0016] In another preferred embodiment, the system further includes an R245fa purity detection device, a hydrogen fluoride concentration detection device, and a molecular sieve adsorption device. The R245fa purity detection device is used to detect the purity of R245fa in the first closed working fluid loop and the second closed working fluid loop. The hydrogen fluoride concentration detection device is used to detect the concentration of hydrogen fluoride produced by the decomposition of R245fa. The control module is also configured to activate the molecular sieve adsorption device when the detected hydrogen fluoride concentration is higher than a preset hydrogen fluoride concentration threshold.

[0017] This application also provides a dual-cycle organic Rankine cycle power generation method with dual heat source coordinated control, employing a high-temperature organic Rankine cycle system and a low-temperature organic Rankine cycle system, both isolated on the working fluid side and using R245fa as the working fluid. The method includes: The hot dry rock geothermal fluid is allowed to flow through the heat source side of the first evaporator of the high-temperature organic Rankine cycle system, so that the R245fa in the high-temperature organic Rankine cycle absorbs heat and vaporizes, driving the first expander impeller to rotate and driving the first generator to generate electricity. The hot dry rock geothermal fluid discharged from the heat source side of the first evaporator flows through the heat source side of the preheater of the low-temperature organic Rankine cycle system to preheat the liquid R245fa in the low-temperature organic Rankine cycle. The preheater is located downstream of the second working fluid pump and upstream of the second evaporator in the low-temperature organic Rankine cycle. The industrial waste heat fluid flows through the waste heat inlet regulating valve V1 through the heat source side of the second evaporator of the low-temperature organic Rankine cycle system, so that the R245fa, which has been preheated by the preheater, continues to absorb heat and vaporize, driving the second expander impeller to rotate and driving the second generator to generate electricity. Obtain the actual power output of the second generator, and adjust the waste heat inlet regulating valve V1 according to the difference between the actual power output and the set power output; Obtain the outlet temperature T at the working fluid side outlet of the preheater. o and export pressure P o According to R245fa at the outlet pressure P o The saturation temperature T below sat (Po), according to ΔT sc =T sat (Po)-T o Determine the subcooling ΔT at the working fluid side outlet of the preheater. sc And in the supercooling ΔT sc When the temperature is below the preset subcooling threshold, the opening of the geothermal bypass regulating valve V2 located on the bypass branch is increased, so that a portion of the dry hot rock geothermal fluid discharged from the first evaporator bypasses the preheater. The adjustment of the waste heat inlet regulating valve V1 and the adjustment of the geothermal bypass regulating valve V2 are respectively based on the actual power generation and the subcooling degree ΔT. sc Execute independently based on feedback volume.

[0018] In another preferred embodiment, adjusting the waste heat inlet regulating valve V1 based on the difference between the actual power generation and the set power generation includes: When the actual power generation is lower than the set power generation, the opening of the waste heat inlet regulating valve V1 is increased to increase the industrial waste heat flow rate input to the second evaporator; When the actual power generation is higher than the set power generation, the opening of the waste heat inlet regulating valve V1 is reduced to reduce the industrial waste heat flow rate input to the second evaporator.

[0019] In another preferred embodiment, adjusting the geothermal bypass regulating valve V2 includes: The supercooling ΔT sc When the temperature is below the preset subcooling threshold, the opening of the geothermal bypass regulating valve V2 is increased to increase the flow rate of the dry hot rock geothermal fluid bypassing the preheater. The supercooling ΔT sc When the degree of subcooling is greater than or equal to the preset subcooling threshold, the opening of the geothermal bypass regulating valve V2 is reduced or maintained. The adjustment of the geothermal bypass regulating valve V2 only changes the flow rate of the dry hot rock geothermal fluid flowing through the heat source side of the preheater, without changing the flow rate of the dry hot rock geothermal fluid flowing through the heat source side of the first evaporator.

[0020] This application has at least one of the following advantages: (a) The system of this application first supplies heat to the first evaporator of the high-temperature organic Rankine cycle through the dry hot rock geothermal fluid, and then uses the geothermal fluid after the first stage of heat release to preheat the low-temperature side liquid R245fa, which can realize the cascade utilization of geothermal energy. (b) In the system of this application, industrial waste heat only serves as a supplementary evaporation heat source in the second evaporator of the low-temperature organic Rankine cycle. The control module can increase or decrease the input of industrial waste heat according to the actual power generation of the second generator, thereby compensating for the fluctuation of geothermal input heat. (c) The control module of the system of this application calculates the subcooling based on the temperature and pressure at the outlet of the working fluid in the preheater, and increases the geothermal bypass flow when the subcooling is lower than the preset threshold, which can suppress the premature vaporization of R245fa in the preheater and reduce the risk of gas blockage and flow instability. (d) The geothermal bypass branch of the system in this application is located downstream of the first evaporator, so that V2 mainly regulates the geothermal flow rate entering the preheater without changing the geothermal flow rate entering the first evaporator. Therefore, the geothermal input of the high-temperature cycle will not be directly weakened due to the phase protection of the preheater. (e) The two closed working fluid loops of the system of this application are isolated from each other on the working fluid side but use the same R245fa working fluid, which facilitates working fluid storage, testing and maintenance management.

[0021] It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. It should be understood that the accompanying drawings described below are merely some implementation examples of the present invention, and those skilled in the art can obtain other implementation examples based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of a dual-cycle organic Rankine cycle power generation system according to one embodiment of this application.

[0024] Figure 2 This is a schematic diagram of the power generation compensation control and preheater outlet subcooling protection control in one embodiment of this application.

[0025] In each of the attached figures, the markings are as follows: 11-First condenser; 12-First working fluid pump; 13-First evaporator; 14-First generator; 20 - Preheater; 21-Second condenser; 22-Second working fluid pump; 23-Second evaporator; 24 - Second generator. Detailed Implementation

[0026] Through extensive and in-depth research, the inventors have developed for the first time a dual-cycle organic Rankine cycle (ORC) power generation system and method with dual heat source coordinated control. This system is a dual-cycle ORC power generation system that couples hot dry rock geothermal energy with industrial waste heat. The system uses a single circulating working fluid, R245fa, with hot dry rock geothermal energy as the main heat source and industrial waste heat as a dynamically adjusted and compensated heat source. It achieves the cascade utilization of heat energy of different grades through two-stage ORC cycles. At the same time, the dynamic closed-loop control of waste heat input reverses the geothermal fluctuations, ensuring the long-term stable and efficient operation of the system while fully absorbing the excess geothermal heat.

[0027] In the following description, many technical details are presented to help the reader better understand this application. However, those skilled in the art will understand that the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0028] the term In this application, "high-temperature organic Rankine cycle" and "low-temperature organic Rankine cycle" are used to distinguish two organic Rankine cycles matched with heat sources of different temperature levels. For design conditions involving geothermal resources and waste heat resources at even lower temperatures, the R245fa evaporation temperature and pressure of the high-temperature organic Rankine cycle are higher than those of the low-temperature organic Rankine cycle. High temperature and low temperature are relative concepts and do not indicate that the working fluid at all locations within the cycle is within a fixed temperature range.

[0029] In this application, "subcooling" refers to the difference between the saturation temperature of R245fa at the pressure at the measurement location and the actual temperature of liquid R245fa at that measurement location. A subcooling greater than zero indicates that the working fluid temperature is lower than the saturation temperature at the corresponding pressure; the smaller the subcooling, the closer the working fluid is to a saturated liquid state.

[0030] It should be noted that in this patent application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this patent application, if it refers to performing an action according to an element, it means performing the action at least according to that element, including two cases: performing the action only according to that element, and performing the action according to that element and other elements. Expressions such as "multiple," "repeatedly," and "various" include two, two times, two kinds, and more than two, more than two times, and more than two kinds.

[0031] In this invention, all directional indicators (such as up, down, left, right, front, back, etc.) are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. It should be understood that these are merely examples provided to the reader of possible implementations of the present invention and are not intended to limit the scope of the invention.

[0033] like Figure 1As shown, the power generation system of this embodiment includes a high-temperature organic Rankine cycle, a low-temperature organic Rankine cycle, a geothermal circuit, an industrial waste heat circuit, and a control module. The high-temperature organic Rankine cycle and the low-temperature organic Rankine cycle are isolated from each other on the R245fa working fluid side, and the R245fa in the two cycles will not flow between each other. The two cycles can be equipped with separate liquid storage components, charging ports, discharge ports, and maintenance ports.

[0034] From the heat source side, the medium-to-high temperature geothermal fluid extracted from hot dry rock is introduced through the system's geothermal inlet. It first enters the first evaporator 13 of the high-temperature ORC cycle, transferring heat energy to the ORC working fluid. After the first stage of heat release, the geothermal water temperature drops significantly, and its remaining heat energy is insufficient to heat the working fluid of the low-temperature ORC cycle to an evaporative state. Therefore, the geothermal water continues to flow into the preheater 20 of the low-temperature ORC cycle, preheating only the low-temperature liquid working fluid. Finally, the geothermal fluid, having fully released heat, exits from the preheater 20 and is discharged back into the ground, completing the closed-loop geothermal cycle. A bypass branch is provided before the geothermal fluid enters the preheater 20, equipped with a geothermal bypass regulating valve V2 to regulate the geothermal flow rate through the preheater 20. This prevents premature partial vaporization of the working fluid within the preheater 20 when the geothermal flow rate is too high, which could cause air blockage and poor flow.

[0035] In one embodiment, a bypass branch branches off from the geothermal pipeline of the geothermal circuit between the heat source side outlet of the first evaporator 13 and the heat source side inlet of the preheater 20, and rejoins the geothermal circuit downstream of the heat source side outlet of the preheater 20. A geothermal bypass regulating valve V2 is installed on the bypass branch. When the opening of V2 increases, the geothermal flow bypassing the preheater 20 increases, and the geothermal flow through the heat source side of the preheater decreases accordingly; when the opening of V2 decreases, the geothermal flow bypassing the preheater 20 decreases, and the geothermal flow through the heat source side of the preheater 20 increases accordingly. Since the bypass branch is located downstream of the first evaporator 13, adjusting V2 does not change the geothermal flow entering the heat source side of the first evaporator 13. The geothermal fluid, after sufficient heat release, can be discharged from the geothermal outlet and reinjected into the ground.

[0036] Industrial waste heat serves as a supplementary heat source. Fluid enters the second evaporator 23 of the low-temperature ORC cycle through the waste heat inlet and the waste heat inlet regulating valve V1. This supplementary heat source heats and evaporates the working fluid on the low-temperature side, and the released waste heat fluid is discharged from the outlet. The waste heat inlet regulating valve V1 is linked to the control module and can adjust the flow rate of the waste heat fluid in real time, dynamically changing the heat input on the waste heat side. Specifically, the waste heat inlet regulating valve V1 is located upstream of the heat source inlet of the second evaporator 23. When the opening of V1 increases, the flow rate of the industrial waste heat fluid entering the second evaporator 23 increases, and the evaporation heat obtained by the low-temperature organic Rankine cycle increases; when the opening of V1 decreases, the industrial waste heat flow rate and the corresponding heat input decrease. V1 and V2 can be electric regulating valves, pneumatic regulating valves, or other flow regulation devices capable of receiving opening commands from the control module.

[0037] The working fluid side is divided into two independent cycles, both using R245fa as the working medium. In the high-temperature ORC cycle, the liquid working fluid is pressurized by the first working fluid pump 12 and enters the first evaporator 13, where it is heated and evaporated into high-pressure superheated steam by the geothermal fluid. The high-pressure steam enters the first turbine (i.e., the first expander) to expand and do work, driving the impeller to rotate and driving the first generator 14 to output electrical energy. The low-pressure exhaust steam after doing work enters the first condenser 11 to condense into liquid working fluid and flows back to the inlet of the first working fluid pump 12, completing the cycle. In the low-temperature ORC cycle, the liquid working fluid is pressurized by the second working fluid pump 22 and first enters the preheater 20 to be preheated by the geothermal water. Then it enters the second evaporator 23 to be further heated and evaporated into a superheated state by the industrial waste heat fluid. The evaporated working fluid steam enters the corresponding turbine (i.e., the second expander), expands and does work, driving the second generator 24 to generate electricity. The exhaust steam after doing work is condensed into liquid by the second condenser 21 and flows back to the inlet of the second working fluid pump 22 to complete the cycle.

[0038] In one example, the hot dry rock geothermal fluid enters the heat source side of the first evaporator 13 from the geothermal inlet, with an inlet temperature of 120°C to 180°C. After primary heat release in the first evaporator 13, the hot dry rock geothermal fluid exits from the heat source side outlet of the first evaporator 13 and flows to the heat source side of the preheater 20. The temperature of the hot dry rock geothermal fluid entering the heat source side inlet of the preheater 20 is 80°C to 150°C. The industrial waste heat fluid can be hot water, steam, heat transfer medium, or other process fluids generated by industrial processes. After releasing heat in the second evaporator 23, the industrial waste heat fluid exits from the industrial waste heat outlet.

[0039] See Figure 2 The dual-cycle organic Rankine cycle power generation system of this application adopts a dynamic compensation control logic for waste heat to the geothermal source, as well as a supporting geothermal bypass cooling protection mechanism. The two sets of regulation logics operate independently, jointly ensuring stable power generation and safe operation of the system.

[0040] Waste heat compensation uses the actual power generation of the system's second generator as the core control target (i.e., second generator power compensation control): the system collects the actual power generation (or power output) of the unit in real time and compares the actual power generation of the second generator with the rated power output / power generation. When the dry hot rock geothermal flow decreases and the geothermal input heat is insufficient, resulting in the actual power generation being lower than the set value, the waste heat inlet regulating valve V1 is opened to increase the flow rate of industrial waste heat fluid, increase the heat input on the waste heat side, and maintain stable power generation; when the geothermal flow increases and the geothermal input heat is excessive, resulting in the actual power generation being higher than the set value, the waste heat inlet regulating valve V1 is closed to reduce the industrial waste heat input, absorb the excess geothermal heat, and prevent the unit from over-generating. Through the dynamic increase and decrease of industrial waste heat, the flow and temperature fluctuations of the geothermal heat source are reversed, so that the unit always maintains stable operation within the power generation range.

[0041] The preheater bypass protection is based on the preheater working fluid outlet subcooling (i.e., preheater working fluid outlet subcooling protection control): The system monitors the working fluid temperature and the corresponding saturation temperature at the preheater outlet in real time and calculates the working fluid subcooling. When the geothermal flow is too large and the preheater has excessive heat exchange, causing the working fluid outlet subcooling to continuously decrease and approach the critical value, the geothermal side bypass valve V2 of the preheater is opened in conjunction, allowing some geothermal fluid to bypass directly, reducing the geothermal flow and heat exchange through the preheater, preventing the liquid working fluid from prematurely evaporating and vaporizing in the preheater, avoiding the risk of pipeline gas blockage and abnormal over-generation, and ensuring the safe and stable operation of the low-temperature circulating working fluid side.

[0042] In one embodiment, the control module may include a data acquisition unit, a processing unit, a storage unit, and an output control unit. The control module may be implemented by a programmable logic controller, a distributed control system, an industrial control computer, or other control device capable of executing the following control logic. The actual power generation of the first and second generators can be obtained from the power measurement devices of the corresponding generators.

[0043] The control module obtains the actual power output P2 of the second generator, and then further determines the set power output P. set With the actual power generation P ２ The power difference between them is eP: eP=P set -P ２ When P ２ Below P set When eP is positive, the control module increases the opening of V1, increasing the industrial waste heat flow into the second evaporator, thereby increasing the power generation of the low-temperature organic Rankine cycle. When P ２ Higher than P setAt this time, the control module reduces the opening of V1, decreasing the industrial waste heat input. Thus, industrial waste heat serves as an adjustable supplementary heat source, compensating for fluctuations in geothermal input heat caused by changes in the flow rate and / or temperature of the dry hot rock geothermal fluid. The set power generation capacity can be a fixed target value or updated based on load commands, equipment allowable output, or operating plans.

[0044] In one embodiment, the temperature sensing element and the pressure sensing element are located at the working fluid side outlet of the preheater or at an adjacent location that can characterize the outlet state. The temperature sensing element measures the outlet temperature T. o The pressure sensing element measures the outlet pressure P. o The control module determines the pressure of R245fa at P based on the pre-stored saturation temperature-pressure relationship of R245fa, the fitting function, or the working fluid state calculation module. o The saturation temperature T below sat (Po), and calculate the subcooling ΔT. sc Pressure P o The absolute pressure diameter is preferred.

[0045] ΔT sc =T sat (Po)-T o When ΔT sc When the temperature falls below the preset subcooling threshold, it indicates that R245fa at the preheater working fluid outlet is at risk of vaporization. The control module increases the opening of V2, allowing more of the dry hot rock geothermal fluid after primary heat release to bypass the preheater, thereby reducing the geothermal flow and heat exchange on the preheater's heat source side, and lowering the outlet temperature T. o Decrease or stop increasing the temperature, increasing the temperature margin of R245fa from saturation. When ΔT sc When the temperature exceeds the preset subcooling threshold, the control module can reduce or maintain the opening of V2 to improve the utilization of geothermal water or maintain the current operating state.

[0046] The preset subcooling threshold can be determined based on the preheater's heat transfer characteristics, temperature detection error, pressure detection error, and allowable phase safety margin. The preset subcooling threshold is used to trigger protective regulation and does not require R245fa to have already vaporized before activation. Therefore, V2 control can reduce the preheater's heat input before the working fluid outlet reaches saturation.

[0047] V1 control and V2 control are based on the actual power output P2 of the second generator and the subcooling degree ΔT, respectively. scThe feedback parameters are applied to the industrial waste heat input and the geothermal bypass flow rate of the preheater, respectively. The two control processes can be executed in parallel, alternately, or independently according to their respective sampling periods. The objective of V1 control is to compensate for changes in the system's second power generation; the objective of V2 control is to maintain the liquid phase state at the preheater's working fluid outlet. V2 is positioned downstream of the first evaporator to ensure that the subcooling protection does not directly alter the geothermal flow rate obtained by the high-temperature organic Rankine cycle.

[0048] This embodiment also provides a dual-cycle organic Rankine cycle power generation method with dual heat source coordinated control. First, the hot dry rock geothermal fluid flows through the heat source side of the first evaporator of the high-temperature organic Rankine cycle system, thereby supplying heat to the R245fa of the high-temperature organic Rankine cycle in the first evaporator 13 of the hot rock geothermal fluid, causing the R245fa to absorb heat and vaporize, and drive the first expander and the first generator to generate electricity.

[0049] The dry hot rock geothermal fluid, after the first stage of heat release (i.e., discharged from the first evaporator 13), enters the heat source of the preheater 20 of the low-temperature organic Rankine cycle, and only the liquid R245fa output by the second working fluid pump 22 is preheated.

[0050] Subsequently, the preheated R245fa enters the second evaporator 23, and the industrial waste heat fluid enters the heat source side of the second evaporator 23 via V1 to utilize the industrial waste heat to complete the vaporization of the low-temperature R245fa. The industrial waste heat fluid flows through the waste heat inlet regulating valve V1 through the heat source side of the second evaporator 23 of the low-temperature organic Rankine cycle system, allowing the R245fa, preheated by the preheater 20, to continue absorbing heat and vaporizing. The vaporized R245fa drives the second expander and the second generator to generate electricity, and after condensation in the second condenser, it returns to the second working fluid pump.

[0051] During system operation, the actual power output P2 of the second generator is acquired, and the actual power output P2 of the second generator is compared with the set power output P. set The difference between the two is adjusted by regulating the waste heat inlet regulating valve V1. Simultaneously, the outlet temperature T of the preheater working fluid side outlet is obtained. o and export pressure P o According to R245fa at the outlet pressure P o The saturation temperature T below sat (Po), and calculate the subcooling ΔT. sc When the supercooling ΔT sc When the temperature is below the preset subcooling threshold, the opening of V2 is increased. Preferably, when ΔT sc When the temperature is greater than or equal to the preset subcooling threshold, the opening of V2 can be reduced or maintained. The two adjustment processes are respectively based on P2 and ΔT. sc Execute independently based on feedback volume.

[0052] In one embodiment, the first closed-loop working fluid circuit and the second closed-loop working fluid circuit are respectively or jointly equipped with an R245fa purity detection device. The R245fa purity detection device can be an online gas chromatograph or other detection device capable of detecting the composition or purity of the working fluid. In a preferred example, the system maintains the R245fa purity at 99.5% or higher.

[0053] In one embodiment, a hydrogen fluoride concentration detection device is used to detect the hydrogen fluoride that may be generated during the thermal decomposition of R245fa. The control module activates the molecular sieve adsorption device when the hydrogen fluoride concentration exceeds a preset hydrogen fluoride concentration threshold. In a preferred example, the preset hydrogen fluoride concentration threshold is 1 ppm. The molecular sieve adsorption device can be connected to a first closed working fluid loop and a second closed working fluid loop respectively, or it can be selectively connected to both closed working fluid loops via a switching valve.

[0054] All documents mentioned in this application are considered to be incorporated in their entirety into the disclosure of this application so that they can serve as a basis for modifications if necessary. Furthermore, it should be understood that after reading the foregoing disclosure of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A dual-cycle organic Rankine cycle power generation system with dual heat source coordinated control, characterized in that, This includes a high-temperature organic Rankine cycle system, a low-temperature organic Rankine cycle system, a geothermal loop, an industrial waste heat loop, and a control module; among which, The high-temperature organic Rankine cycle includes a first working fluid pump, a first evaporator, a first expander, and a first condenser connected in sequence to form a first closed working fluid loop; and the high-temperature organic Rankine cycle system also includes a first generator connected to the first expander; The low-temperature organic Rankine cycle includes a second working fluid pump, a preheater, a second evaporator, a second expander, and a second condenser connected in sequence to form a second closed working fluid loop; and a second generator connected to the second expander. The first closed working fluid loop and the second closed working fluid loop are isolated from each other and both use R245fa as the circulating working fluid. The geothermal circuit is configured such that the dry hot rock geothermal fluid flows sequentially through the heat source side of the first evaporator and the heat source side of the preheater before being discharged from the preheater. The geothermal circuit also includes a bypass branch that bypasses the heat source side of the preheater. A geothermal bypass regulating valve V2 is installed on the bypass branch, and the bypass branch is configured to regulate the flow rate of the dry hot rock geothermal fluid entering the preheater. The industrial waste heat circuit is configured such that the industrial waste heat fluid flows through the heat source side of the second evaporator via a waste heat inlet regulating valve V1 before being discharged. The control module is connected to the first generator, the second generator, the waste heat inlet regulating valve V1, the geothermal bypass regulating valve V2, and temperature and pressure sensing elements located at the working fluid outlet of the preheater. It is configured to: adjust the waste heat inlet regulating valve V1 based on the difference between the actual power output of the second generator and the set power output, thereby compensating for fluctuations in the flow rate of the dry hot rock geothermal fluid using industrial waste heat input; and adjust the outlet temperature T measured by the temperature sensing element. o The outlet pressure P measured by the pressure detection element o And R245fa at the outlet pressure P o The saturation temperature T below sat (Po), determine the subcooling ΔT at the working fluid outlet of the preheater. sc =T sat (Po)-T o And in the supercooling ΔT sc When the temperature is below the preset subcooling threshold, the opening of the geothermal bypass regulating valve V2 is increased to reduce the flow rate of the dry hot rock geothermal fluid flowing through the preheater, so that R245fa at the working fluid outlet of the preheater remains in the liquid phase. The regulation of the waste heat inlet regulating valve V1 and the regulation of the geothermal bypass regulating valve V2 are performed independently with the actual power generation and the subcooling as feedback quantities, respectively.

2. The dual-cycle organic Rankine cycle power generation system as described in claim 1, characterized in that, The control module is configured to increase the opening of the waste heat inlet regulating valve V1 when the actual power output of the second generator is less than the set power output, and is configured to decrease the opening of the waste heat inlet regulating valve V1 when the actual power output of the second generator is higher than the set power output.

3. The dual-cycle organic Rankine cycle power generation system as described in claim 1, characterized in that, The preheater is used to preheat the liquid R245fa after it has been pressurized by the second working fluid pump, and the second evaporator is used to use the industrial waste heat fluid to further heat up and vaporize the preheated R245fa and form steam for the expansion of the second expander.

4. The dual-cycle organic Rankine cycle power generation system as described in claim 1, characterized in that, The bypass branch branches off from the heat source side outlet of the first evaporator and the heat source side inlet of the preheater, and merges into the geothermal circuit downstream of the heat source side outlet of the preheater.

5. The dual-cycle organic Rankine cycle power generation system as described in claim 1, characterized in that, The control module is also configured to reduce or maintain the opening of the geothermal bypass regulating valve V2 when the subcooling degree is greater than the preset subcooling degree threshold.

6. The dual-cycle organic Rankine cycle power generation system as described in claim 1, characterized in that, The dry hot rock geothermal fluid enters the heat source side inlet of the first evaporator from the geothermal inlet, and the temperature of the dry hot rock geothermal fluid entering the heat source side inlet of the first evaporator is 120-180℃.

7. The dual-cycle organic Rankine cycle power generation system as described in claim 1, characterized in that, The temperature of the industrial waste heat fluid entering the heat source side inlet of the second evaporator is 80-150°C.

8. The dual-cycle organic Rankine cycle power generation system as described in claim 1, characterized in that, It also includes an R245fa purity detection device, a hydrogen fluoride concentration detection device, and a molecular sieve adsorption device. The R245fa purity detection device is used to detect the purity of R245fa in the first closed working fluid loop and the second closed working fluid loop. The hydrogen fluoride concentration detection device is used to detect the concentration of hydrogen fluoride produced by the decomposition of R245fa. The control module is also configured to activate the molecular sieve adsorption device when the detected hydrogen fluoride concentration is higher than a preset hydrogen fluoride concentration threshold.

9. A dual-cycle organic Rankine cycle power generation method with dual heat source coordinated control, characterized in that, The method comprises: a high-temperature organic Rankine cycle system and a low-temperature organic Rankine cycle system, both isolated on the working fluid side and using R245fa as the circulating working fluid; The hot dry rock geothermal fluid is allowed to flow through the heat source side of the first evaporator of the high-temperature organic Rankine cycle system, so that the R245fa in the high-temperature organic Rankine cycle absorbs heat and vaporizes, driving the first expander impeller to rotate and driving the first generator to generate electricity. The dry hot rock geothermal fluid discharged from the heat source side of the first evaporator flows through the heat source side of the preheater of the low-temperature organic Rankine cycle system to preheat the liquid R245fa in the low-temperature organic Rankine cycle. The preheater is located downstream of the second working fluid pump and upstream of the second evaporator in the low-temperature organic Rankine cycle. The industrial waste heat fluid flows through the waste heat inlet regulating valve V1 through the heat source side of the second evaporator of the low-temperature organic Rankine cycle system, so that the R245fa preheated by the preheater continues to absorb heat and vaporize, driving the second expander impeller to rotate and driving the second generator to generate electricity. Obtain the actual power output of the second generator, and adjust the waste heat inlet regulating valve V1 according to the difference between the actual power output and the set power output; Obtain the outlet temperature T at the working fluid side outlet of the preheater. o and export pressure P o According to R245fa at the outlet pressure P o The saturation temperature T below sat (Po), according to ΔT sc =T sat (Po)-T o Determine the subcooling ΔT at the working fluid side outlet of the preheater. sc And in the supercooling ΔT sc When the temperature is below the preset subcooling threshold, the opening of the geothermal bypass regulating valve V2 located on the bypass branch is increased, so that a portion of the dry hot rock geothermal fluid discharged from the first evaporator bypasses the preheater. The adjustment of the waste heat inlet regulating valve V1 and the adjustment of the geothermal bypass regulating valve V2 are respectively based on the actual power generation and the subcooling degree ΔT. sc Execute independently based on feedback volume.

10. The dual-cycle organic Rankine cycle power generation method as described in claim 9, characterized in that, Adjusting the waste heat inlet regulating valve V1 according to the difference between the actual power generation and the set power generation includes: When the actual power generation is lower than the set power generation, the opening of the waste heat inlet regulating valve V1 is increased to increase the industrial waste heat flow rate input to the second evaporator; When the actual power generation is higher than the set power generation, the opening of the waste heat inlet regulating valve V1 is reduced to reduce the industrial waste heat flow rate input to the second evaporator.

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