Waste heat utilization power generation device and power generation method applied to pure condensing peak shaving gas turbine

Abstract

The invention relates to the technical field of gas turbine waste heat utilization, and discloses a waste heat utilization power generation device and method applied to a pure condensing peak shaving gas turbine. The device comprises a closed loop taking isobutane as a cycle working medium, a waste heat-organic working medium heat exchanger, an isobutane turbine generator set, a condensation backflow part and a control system. After the gas turbine is shut down, heat storage steam or hot water is led out from the waste heat boiler steam-water system, heat energy is transmitted to isobutane through the heat exchanger, the isobutane is evaporated into superheated steam and drives the turbine generator set to generate electricity, and working media after acting are pumped into the heat exchanger again through the condensation backflow part to complete circulation. Isobutane is adopted as a working medium, the system adapts to medium and low temperature and transient heat source characteristics, stable grid connection is achieved through the clutch transmission mechanism, the control system dynamically adjusts operation parameters, the problem that heat stored in the waste heat boiler cannot be recycled after the pure condensing peak shaving gas turbine stops is effectively solved, and the energy utilization efficiency and the power plant economy are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of waste heat utilization technology for gas turbines, specifically to a waste heat utilization power generation device and power generation method applied to pure condensing peak-shaving gas turbines. Background Technology

[0002] Gas-steam combined cycle units play an increasingly important role in peak shaving in the power grid due to their advantages such as fast start-up and shutdown speed, good peak shaving performance, and low carbon emissions. Among them, peak shaving gas turbines operating in pure condensing mode need to be frequently started and stopped or run at low loads during periods of low grid load to balance grid fluctuations.

[0003] However, even after such units are shut down, their associated waste heat boilers (HRSG) still store a large amount of high-temperature, high-pressure stored steam and hot water in their steam-water systems. If this high-quality waste heat energy is not utilized promptly and effectively, it will dissipate into the environment through natural cooling, resulting in significant energy waste. Currently, conventional steam power cycles cannot operate after the main unit is shut down, and there is a lack of a technological means to independently and efficiently recover and utilize this "idle" heat energy.

[0004] Organic Rankine Cycle (ORC) technology has attracted widespread attention due to its ability to efficiently utilize medium- and low-temperature heat sources. However, when applied to heat storage in boilers recovering waste heat after gas turbine shutdown, it faces several unique challenges: First, the heat source is intermittent and transient saturated steam or hot water, whose temperature and flow rate continue to decrease as the shutdown time increases, requiring the power generation system to have wide operating condition adaptability and rapid response capability; second, conventional ORC working fluids may be inefficient or pose safety issues in such temperature ranges.

[0005] Therefore, there is an urgent need to develop a waste heat utilization power generation device and method for pure condensing peak-shaving gas turbines, which aims to recover and utilize the residual heat in the boiler after the unit is shut down and convert it into electrical energy, thereby improving the overall energy efficiency of the power plant, reducing heat loss, and enhancing the economic and environmental benefits of peak-shaving power plants. Summary of the Invention

[0006] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a waste heat utilization power generation device and method for pure condensing peak-shaving gas turbines. It has the advantages of independently recovering and utilizing the heat energy of the waste heat boiler after the pure condensing peak-shaving gas turbine is shut down, and solves the problem that conventional steam power cycles cannot operate after the main unit is shut down, and lack effective means of recovering and utilizing the heat storage technology of the waste heat boiler after the gas turbine is shut down.

[0007] (II) Technical Solution To achieve the aforementioned objective of independently recovering and utilizing the thermal energy of the waste heat boiler after the shutdown of a pure condensing peak-shaving gas turbine, the present invention provides the following technical solution: This invention provides a waste heat utilization power generation device for a pure condensing peak-shaving gas turbine, comprising: a closed working fluid circulation loop using isobutane as the working fluid, equipped with a working fluid power pump; a waste heat-organic working fluid heat exchanger, including two non-connected pipelines on the primary and secondary sides, the primary side inlet being connected to the high-temperature section of the waste heat boiler steam-water system for receiving heat-storage steam or hot water from the waste heat boiler, and the primary side outlet connecting the condensed water to the condenser hot well; the secondary side inlet and outlet being both connected to the working fluid circulation loop for transferring waste heat energy to isobutane, causing it to evaporate into superheated steam; and an isobutane vortex. The turbine generator set includes a turbine and a generator. The inlet of the turbine is connected to the secondary outlet of the heat exchanger to convert the thermal energy of isobutane vapor into mechanical energy. The generator is connected to the turbine via a clutchable transmission mechanism and is installed on the working fluid circulation loop. A condensation return section is installed on the working fluid circulation loop to condense the isobutane working fluid discharged from the turbine into a liquid state and return it to the secondary inlet of the heat exchanger via a working fluid power pump. A control system is connected to the working fluid power pump, the heat exchanger, the waste heat boiler, and the isobutane turbine generator set to monitor and regulate the system operation.

[0008] The waste heat-organic working fluid heat exchanger is a plate heat exchanger, and is equipped with a steam-water separator and a drain valve to separate condensate from the primary side medium and ensure heat transfer efficiency.

[0009] A safety pressure relief valve is installed on the primary side inlet pipe of the waste heat-organic working fluid heat exchanger to release steam or hot water when the system is overpressured.

[0010] It also includes a temperature control device for adjusting the flow rate of boiler heat storage steam or hot water on the primary side according to the isobutane steam temperature at the secondary side outlet of the waste heat-organic working fluid heat exchanger, so as to maintain the stability of the turbine inlet steam parameters.

[0011] The temperature control device employs a PID controller and achieves dynamic flow control through an electric regulating valve.

[0012] The clutchable transmission mechanism is a hydraulic clutch or a mechanical overrunning clutch, which is used to automatically engage and transmit torque after the turbine speed reaches the generator synchronous speed.

[0013] The condensation reflux section includes a condenser, a liquid storage tank, and a working fluid pressurization pump, which is used to condense the remaining gaseous isobutane into liquid and pump it back into the heat exchanger.

[0014] The waste heat-organic working fluid heat exchanger is also equipped with a dosing device at the secondary side inlet for injecting ammonia or heptafluoropropane to adjust the properties of isobutane and enhance system stability.

[0015] The control system is also equipped with a power output adjustment module, which can adjust the power generation load according to grid demand or fluctuations in waste heat sources.

[0016] In another aspect, the present invention provides a method for generating electricity using a waste heat recovery power generation device applied to a pure condensing peak-shaving gas turbine, comprising the following steps: S1: After the pure condensing peak-shaving gas turbine is shut down, heat storage steam or hot water is drawn from the high-temperature section of the waste heat boiler steam-water system. S2: The heat storage steam or hot water is introduced into the primary side of the waste heat-organic working fluid heat exchanger to transfer its heat energy to the isobutane circulating in the working fluid circulation loop, so that the isobutane evaporates into superheated steam. S3: The superheated isobutane vapor is introduced into the turbine of the isobutane turbine generator set, causing it to expand and do work, converting thermal energy into mechanical energy, and driving the generator to generate electricity through a clutchable transmission mechanism. S4: The isobutane working fluid discharged from the turbine after the work is done is transported to the condensation and reflux section, condensed into liquid, and then sent back to the secondary side inlet of the waste heat-organic working fluid heat exchanger by the working fluid power pump, thus completing the closed circulation of the isobutane working fluid. S5: The control system is used to dynamically monitor and adjust the key operating parameters of the power generation device in order to achieve automatic operation and safety protection of the system.

[0017] (III) Beneficial Effects Compared with the prior art, the present invention provides a waste heat utilization power generation device applied to a pure condensing peak-shaving gas turbine, which has the following beneficial effects: This waste heat recovery power generation device and method applied to pure condensing peak-shaving gas turbines utilizes a closed-loop system with isobutane as the working fluid. It integrates a waste heat-organic working fluid heat exchanger, an isobutane turbine generator set, and a control system, achieving efficient recovery of intermittent and transient heat storage (saturated steam / hot water) in the waste heat boiler after the gas turbine shutdown. The isobutane working fluid is adapted to medium- and low-temperature heat sources. The heat exchanger converts waste heat into superheated steam to drive the turbine for power generation. A clutchable transmission mechanism ensures smooth grid connection. The control system dynamically adjusts the working fluid flow and heat source parameters, ensuring wide operating condition adaptability and rapid response. This device operates independently of the main unit, effectively converting "idle" heat energy into electrical energy, significantly improving power plant energy efficiency, reducing heat dissipation, enhancing the economic and environmental benefits of peak-shaving power plants, and solving the key problem of traditional technologies being unable to recover waste heat during shutdown. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the waste heat utilization power generation device of the present invention; Figure 2 This is a schematic diagram of the connection principle of the control system in this invention.

[0019] In the diagram: 1. Working fluid circulation loop; 2. Working fluid power pump; 3. Heat exchanger; 4. Waste heat boiler; 5. Condenser hot well; 6. Turbine generator set; 7. Condensate reflux section; 8. Control system; 9. Safety relief valve; 10. Temperature control device; 11. PID controller; 12. Electric regulating valve; 13. Dosing device; 14. Regulating module; 301. Primary side inlet; 302. Primary side outlet; 303. Secondary side outlet; 304. Secondary side inlet; 601. Turbine; 602. Generator; 603. Clutchable transmission mechanism; 701. Condenser; 702. Liquid storage tank; 703. Working fluid pressurization pump. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] Example 1 Please see Figure 1 and Figure 2 In the energy sector, particularly in the peak-shaving operation of gas-fired combined cycle power plants, the efficient recovery of the large amount of heat stored in waste heat boilers after unit shutdown has always been a technical challenge. Existing technologies typically lack solutions specifically for this scenario; conventional steam power cycles cannot operate independently after the main unit is shut down, resulting in the loss of high-quality thermal energy through natural cooling. A waste heat recovery power generation device for pure condensing peak-shaving gas turbines includes a closed loop 1 using isobutane as the circulating working fluid, equipped with a working fluid power pump 2. Isobutane was chosen because of its suitable boiling point, good thermophysical properties, and high conversion efficiency for medium- and low-temperature heat sources. Its moderate molecular weight allows it to expand in the turbine to generate sufficient work, making it ideal for utilizing the gradually decaying saturated steam or hot water in the waste heat boiler.

[0022] The waste heat-organic working fluid heat exchanger 3 functions to transfer heat energy from the waste heat boiler 4 to isobutane. Specifically, it includes two separate pipelines on the primary and secondary sides. The primary side inlet 301 of the heat exchanger 3 is connected to the high-temperature section (such as the steam drum or high-temperature economizer) of the steam-water system of the waste heat boiler 4 via a pipeline to receive the stored steam or high-temperature hot water released after shutdown. Its primary side outlet 302 guides the water generated after the primary side medium is condensed to the power plant's existing condenser hot well 5 for recovery, thereby realizing the recycling of water resources without the need for an additional drainage system. The secondary side inlet 304 and outlet 303 of the heat exchanger 3 are seamlessly connected to the isobutane closed-loop loop 1. Here, the heat of the stored steam or hot water is transferred to the isobutane, causing it to be heated and eventually evaporated into high-pressure isobutane steam with a certain degree of superheat, preparing it for the subsequent power generation stage.

[0023] In this embodiment, a plate heat exchanger is preferred due to its advantages of high heat transfer efficiency, compact structure, and ability to handle transient heat source conditions. To ensure complete condensation and efficient heat transfer of the primary-side steam, a steam-water separator and a steam trap are also installed on the primary side to promptly separate and discharge the generated condensate, preventing water hammer or reduced heat transfer efficiency.

[0024] In addition, a safety relief valve 9 is crucially installed on the primary side inlet 301 pipeline. As a passive protection measure, it can automatically release steam or hot water when the system pressure rises abnormally, ensuring the safety of heat exchanger 3 and subsequent pipelines.

[0025] The isobutane turbine generator set 6 is the core of the system's energy conversion, transforming thermal energy into electrical energy. It mainly consists of a turbine 601 and a generator 602. The inlet of turbine 601 is directly connected to the secondary side outlet 303 of the aforementioned heat exchanger 3, receiving superheated, high-pressure isobutane vapor. The vapor expands within turbine 601, driving the rotor to rotate and converting thermal and pressure energy into mechanical energy. Generator 602 is connected to the output shaft of turbine 601 via a clutchable transmission mechanism 603. This mechanism 603 is crucial for handling rapid system start-up and shutdown and variable operating conditions; it can be a hydraulic clutch or a mechanical overrunning clutch. Its function is as follows: In the initial stage of system startup, when turbine 601 operates at a low speed and has not reached the synchronous speed of generator 602 (e.g., 3000 rpm), the clutch is disengaged, allowing the turbine to accelerate independently and preventing generator 602 from becoming a starting load; once the turbine speed accelerates to synchronize with generator 602, the clutch automatically engages, smoothly transmitting torque to generator 602 to drive its rotation and grid connection for power generation. The entire generator set 6 is installed as a modular unit on the working fluid circulation loop 1.

[0026] The condenser reflux section 7 is responsible for completing the working fluid circulation. Installed downstream of the turbine 601 outlet, it converts the low-temperature, low-pressure gaseous isobutane working fluid discharged after work into a liquid state. This section consists of a condenser 701 (typically cooled by the power plant's circulating cooling water), a liquid storage tank 702 (for storing and purifying the liquid working fluid), and a working fluid pressurization pump 703. After being pressurized by the working fluid power pump 2, the liquid isobutane is pumped back into the secondary inlet 304 of the waste heat-organic working fluid heat exchanger 3, thus forming a complete, closed power cycle.

[0027] The control system 8 is connected to the working fluid power pump 2, the booster device, the heat exchanger 3, the waste heat boiler 4, and the isobutane turbine generator set 6. It continuously monitors key parameters through a series of sensors, including but not limited to: the pressure of the steam drum in the waste heat boiler 4 (used to determine the energy grade and total amount of available heat source), the temperature of the primary side inlet 301 and outlet 302 of the heat exchanger 3, the temperature and pressure of the secondary side inlet 304 and outlet 303, the turbine speed, and the voltage, frequency, and grid connection status of the generator 602. Based on this real-time data, the control system 8 dynamically adjusts the system operating parameters through preset algorithms, such as adjusting the frequency, working fluid flow rate, or pressure through the working fluid power pump 2 and the booster device, to achieve automatic start-up and shutdown, stable operation, and safe shutdown in case of faults in the power generation system. In particular, the control system 8 also integrates a power output regulation module 14, which can respond to grid dispatch commands or adaptively adjust the power generation load intelligently according to fluctuations in waste heat source parameters (such as the natural decrease in heat source temperature and flow rate over time), ensuring the system always operates near its optimal operating point and maximizing energy recovery efficiency.

[0028] In some optimized embodiments, a temperature control device 10 is also added. This device uses the isobutane steam temperature at the secondary side outlet 303 of the heat exchanger 3 as the control target. It outputs a signal through a PID controller 11 to operate an electric regulating valve 12 installed on the primary side inlet 301, dynamically adjusting the flow rate of boiler heat storage steam or hot water. In this way, regardless of changes in the primary side heat source parameters, the superheat and pressure of the isobutane steam entering the turbine 601 can be maintained stably, thereby ensuring the efficient operation of the turbine 601.

[0029] Furthermore, to further enhance the long-term stability and adaptability of the system, a dosing device 13 can be installed before the secondary side inlet 304 of the waste heat-organic working fluid heat exchanger 3. This device 13 can be used to inject trace amounts of additives, such as ammonia or heptafluoropropane. These substances can be used to adjust the physical properties of the isobutane working fluid (such as specific heat capacity, thermal conductivity, etc.) through trace doping, or to fine-tune the pressure and temperature setpoints on the secondary side during the initial commissioning of the system, thereby optimizing the system's performance under different heat source conditions.

[0030] Example 2 A power generation method for a waste heat utilization power generation device applied to a pure condensing peak-shaving gas turbine includes the following steps: S1: After the pure condensing peak-shaving gas turbine is shut down, heat storage steam or hot water is drawn from the high-temperature section of the steam-water system of the waste heat boiler 4. S2: The heat storage steam or hot water is introduced into the primary side of the waste heat-organic working fluid heat exchanger 3, and its heat energy is transferred to the isobutane circulating in the working fluid circulation loop 1, so that the isobutane evaporates into superheated steam. S3: Superheated isobutane vapor is introduced into the turbine 601 of the isobutane turbine generator set 6, causing it to expand and do work, converting thermal energy into mechanical energy, and driving the generator 602 to generate electricity through the clutchable transmission mechanism 603. S4: The isobutane working fluid discharged from the turbine 601 after the work is done is transported to the condensation and reflux section 7, where it is condensed into a liquid state and then sent back to the secondary side inlet 304 of the waste heat-organic working fluid heat exchanger 3 through the working fluid power pump 2, thus completing the closed-loop circulation of the isobutane working fluid. S5: The control system 8 is used to dynamically monitor and adjust the key operating parameters of the power generation device in order to realize the automatic operation and safety protection of the system.

[0031] This method uses isobutane as the circulating working fluid, and uses heat exchanger 3 to efficiently recover the waste heat of the gas turbine after shutdown and boiler 4 to store the heat. The heat energy is transferred to isobutane, and the working fluid is then used to generate electricity through turbine generator set 6. In conjunction with condensation reflux section 7 and control system 8, the heat energy is converted into electrical energy, thereby achieving the goal of generating electricity from waste heat boiler 4 after shutdown.

[0032] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A waste heat recovery power generation device applied to a pure condensing peak-shaving gas turbine, characterized in that, include: A closed working fluid circulation loop (1) with isobutane as the circulating working fluid is equipped with a working fluid power pump (2). The waste heat-organic working fluid heat exchanger (3) includes two separate pipelines on the primary and secondary sides. Its primary side inlet (301) is connected to the high-temperature section of the steam-water system of the waste heat boiler (4) to receive heat storage steam or hot water from the waste heat boiler (4). Its primary side outlet (302) connects the condensed water to the condenser hot well (5). Its secondary side inlet (304) and secondary side outlet (303) are both connected to the working fluid circulation loop (1) to transfer waste heat energy to isobutane, causing it to evaporate into superheated steam. An isobutane turbine generator set (6) includes a turbine (601) and a generator (602). The inlet of the turbine (601) is connected to the secondary side outlet (303) of the heat exchanger (3) for converting the thermal energy of isobutane vapor into mechanical energy. The generator (602) is connected to the turbine (601) through a clutchable transmission mechanism (603) and is installed on the working fluid circulation loop (1). The condensation reflux section (7) is installed on the working fluid circulation loop (1) to condense the isobutane working fluid discharged from the turbine (601) into liquid and send it back to the secondary side inlet (304) of the heat exchanger (3) via the working fluid power pump (2). The system (8) is connected to the working fluid power pump (2), heat exchanger (3), waste heat boiler (4) and isobutane turbine generator set (6) respectively, and is used to monitor and regulate the operation of the system.

2. The waste heat recovery power generation device applied to a pure condensing peak-shaving gas turbine according to claim 1, characterized in that: The waste heat-organic working medium heat exchanger (3) is a plate heat exchanger and is equipped with a steam-water separator and a drain valve to separate condensate from the primary medium and ensure heat transfer efficiency.

3. The waste heat recovery power generation device applied to a pure condensing peak-shaving gas turbine according to claim 1, characterized in that: A safety relief valve (9) is provided on the primary side inlet (301) pipeline of the waste heat-organic working fluid heat exchanger (3) to release steam or hot water when the system is overpressured.

4. A waste heat recovery power generation device applied to a pure condensing peak-shaving gas turbine according to claim 1, characterized in that: It also includes a temperature control device (10) for adjusting the flow rate of boiler heat storage steam or hot water on the primary side according to the isobutane steam temperature at the secondary side outlet (303) of the waste heat-organic working fluid heat exchanger (3) in order to maintain the stability of the inlet steam parameters of the turbine (601).

5. A waste heat recovery power generation device applied to a pure condensing peak-shaving gas turbine according to claim 4, characterized in that: The temperature control device (10) uses a PID controller (11) and achieves dynamic flow control through an electric regulating valve (12).

6. A waste heat recovery power generation device applied to a pure condensing peak-shaving gas turbine according to claim 1, characterized in that: The clutchable transmission mechanism (603) is a hydraulic clutch or a mechanical overrunning clutch, used to automatically engage and transmit torque after the turbine (601) reaches the synchronous speed of the generator (602).

7. A waste heat recovery power generation device applied to a pure condensing peak-shaving gas turbine according to claim 1, characterized in that: The condensation reflux section (7) includes a condenser (701), a liquid storage tank (702), and a working fluid pressurization pump (703) for condensing the remaining gaseous isobutane into liquid and pumping it back into the heat exchanger (3).

8. A waste heat recovery power generation device applied to a pure condensing peak-shaving gas turbine according to claim 1, characterized in that: A dosing device (13) is also provided at the secondary side inlet (304) of the waste heat-organic working fluid heat exchanger (3) for injecting ammonia or heptafluoropropane to adjust the physical properties of isobutane and enhance system stability.

9. A waste heat recovery power generation device applied to a pure condensing peak-shaving gas turbine according to claim 1, characterized in that: The control system (8) is also equipped with a power output adjustment module (14), which can adjust the power generation load according to the grid demand or the fluctuation of waste heat source.

10. A method for generating electricity after a pure condensing peak-shaving gas turbine is shut down, characterized in that, The waste heat recovery power generation device according to any one of claims 1-9 includes the following steps: S1: After the pure condensing peak-shaving gas turbine is shut down, heat storage steam or hot water is drawn from the high-temperature section of the waste heat boiler (4) steam-water system; S2: The heat storage steam or hot water is introduced into the primary side of the waste heat-organic working fluid heat exchanger (3) to transfer its heat energy to the isobutane circulating in the working fluid circulation loop (1), so that the isobutane evaporates into superheated steam. S3: The superheated isobutane vapor is introduced into the turbine (601) of the isobutane turbine generator (602) group (6) to expand and do work, converting thermal energy into mechanical energy, and driving the generator (602) to generate electricity through the clutchable transmission mechanism (603); S4: The isobutane working fluid discharged from the turbine (601) after doing work is transported to the condensation reflux section (7), and after being condensed into liquid, it is sent back to the secondary side inlet (304) of the waste heat-organic working fluid heat exchanger (3) through the working fluid power pump (2) to complete the closed circulation of the isobutane working fluid. S5: The control system (8) is used to dynamically monitor and adjust the key operating parameters of the power generation device in order to realize the automatic operation and safety protection of the system.

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