Steam turbine exhaust steam gradient utilization heat supply system and method based on electric compressor

Abstract

The invention discloses a steam turbine exhaust steam gradient utilization heat supply system and method based on an electric compressor. The system comprises a steam source leading unit, an electric steam compressor unit, a heat exchanger, a regulating valve, a parameter measuring unit and an integrated control unit. An inlet of the heat absorption side is connected with an outlet of the electric steam compressor unit; the outlet of the heat absorption side is used for outputting heat supply steam; the regulating valve is arranged on a pipeline between the reheating hot section pipeline and a heat release side inlet of the heat exchanger and is used for controlling the flow of reheating steam entering the heat release side; the integrated control unit is used for performing closed-loop regulation on the working rotating speed of the compressor unit and the opening degree of the regulating valve according to the deviation between the received pressure signal and the preset target pressure and the deviation between the temperature signal and the preset target temperature, so that the stability of the heat supply steam pressure and temperature is realized; according to the invention, cascade efficient utilization of energy can be realized with lower transformation cost and engineering implementation difficulty.

Description

Technical Field

[0001] This invention belongs to the field of thermal power generation and comprehensive energy utilization technology, and particularly relates to a steam turbine exhaust gas cascade utilization heating system and method based on an electric compressor. Background Technology

[0002] In large-scale combined heat and power (CHP) systems of thermal power units, the exhaust steam from the high-pressure turbine, i.e., cold resteam, typically has lower pressure and temperature parameters. This steam is generally returned to the boiler for reheating and then enters the medium- and low-pressure turbines to continue performing work. With the increasing demand for medium-pressure, medium-temperature steam from industrial users, how to effectively utilize this cold resteam has become a key issue in heating system retrofitting. The parameters of cold resteam are usually maintained within the range of 1.8-3.0 MPa pressure and 300-350 degrees Celsius temperature, while many industrial users often require higher steam parameters, making direct use of cold resteam insufficient to meet their needs.

[0003] The traditional solution is to draw steam with higher parameters from the main steam pipeline, reduce its parameters through a desuperheating and pressure-reducing device, and then supply it to users. While this method ensures that the steam supply parameters meet requirements, the main steam is a high-quality thermal energy source, and using it after desuperheating and pressure reduction means that a significant amount of work capacity is wasted, which is extremely unreasonable from the perspective of energy cascade utilization. Another approach is to simply pressurize the cold reheat steam, but the operating characteristics of the compressor mean that the steam temperature will change along with the pressure increase. Simple pressure control cannot guarantee the stability of temperature parameters, which are precisely the key process parameters in the production processes of many industrial users.

[0004] In actual operation, the steam load of heat users is not constant. When the load fluctuates, the steam supply pressure and temperature will deviate accordingly. Under traditional control methods, pressure and temperature regulation are often carried out independently, lacking effective coordination. This results in slow system response and long recovery time, making it difficult to meet users' stable requirements for steam supply quality. At the same time, the reliability of the heating system is also a crucial issue. When the booster equipment or heat exchange equipment malfunctions and needs to be shut down, ensuring uninterrupted steam supply to users and avoiding production losses due to steam supply interruptions is an important factor that must be considered in system design.

[0005] Based on the above situation, a heating solution is needed that can achieve coordinated control of exhaust pressure and temperature of the high-pressure cylinder of the steam turbine, has rapid load response capability, and can still ensure continuous steam supply in the event of a fault, so as to realize the efficient cascade utilization of energy. Summary of the Invention

[0006] The purpose of this invention is to provide a steam turbine exhaust gas cascade utilization heating system and method based on an electric compressor. This system can efficiently upgrade the exhaust gas from the high-pressure cylinder of the steam turbine into high-parameter industrial steam that meets user requirements, fundamentally avoiding the direct throttling and waste of high-quality main steam, and achieving cascade efficient utilization of energy with lower modification costs and engineering implementation difficulty.

[0007] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a steam turbine exhaust gas cascade utilization heating system based on an electric compressor, comprising: a steam source extraction unit, an electric steam compressor unit, a heat exchanger, a regulating valve, a parameter measurement unit, and an integrated control unit; The inlet of the steam source extraction unit is connected to the high-pressure cylinder exhaust pipeline of the steam turbine for extracting steam. The inlet of the electric steam compressor unit is connected to the outlet of the steam source extraction unit, which is used to compress the extracted steam to obtain compressed steam. The heat exchanger has a heat absorption side and a heat release side. The inlet of the heat absorption side is connected to the outlet of the electric steam compressor unit to receive compressed steam. The outlet of the heat absorption side is used to output heating steam. The inlet of the heat release side is used to receive reheated steam after passing through the regulating valve. The outlet of the heat release side is connected to the high-pressure cylinder exhaust pipeline. The regulating valve is installed on the pipeline between the reheat hot section pipeline and the heat exchanger heat release side inlet, and is used to control the reheat steam flow rate entering the heat release side; The parameter measurement unit is installed on the heating steam output pipeline to detect the pressure and temperature of the heating steam in real time and output pressure and temperature signals. The integrated control unit is connected to the parameter measurement unit, the regulating valve, and the electric steam compressor unit respectively. It is used to adjust the operating speed of the compressor unit in a closed loop according to the deviation between the received pressure signal and the preset target pressure. At the same time, it adjusts the opening of the regulating valve in a closed loop according to the deviation between the received temperature signal and the preset target temperature. By controlling the reheat steam flow rate entering the heat release side, the temperature of the heating steam is stabilized, and finally, the decoupled control and stable output of the heating steam pressure and temperature are achieved.

[0008] Optionally, the steam source extraction unit includes an isolation valve and a steam filter connected in sequence along the steam flow direction.

[0009] Optionally, the electric steam compressor unit includes a variable frequency motor, a steam compressor driven by the variable frequency motor, and a safety valve disposed at the outlet of the steam compressor.

[0010] Optionally, the heat exchanger is a shell-and-tube heat exchanger, in which heat exchange is performed between the heat absorption side and the heat release side through a tube bundle.

[0011] Optionally, a check valve is also provided at the outlet on the heat-exerting side to prevent steam from flowing in the opposite direction.

[0012] The optional turbine exhaust steam cascade utilization heating system based on electric compressor may further include a bypass unit between the main steam pipeline and the heating steam output pipeline, for emergency heating in case of failure of the electric steam compressor unit or heat exchanger.

[0013] Optionally, the bypass unit includes a bypass valve and a bypass desuperheating and pressure reducing valve. One end of the bypass valve is connected to the main steam pipeline, and the other end is connected to the inlet of the bypass desuperheating and pressure reducing valve. The outlet of the bypass desuperheating and pressure reducing valve is connected to the heating steam output pipeline.

[0014] In a second aspect, the present invention provides a method for cascade utilization of turbine exhaust steam for heating based on an electric compressor, employing the cascade utilization of turbine exhaust steam for heating system based on an electric compressor as described in the first aspect, comprising: Steam is extracted from the high-pressure cylinder exhaust pipeline of the steam turbine based on the steam source extraction unit; The extracted steam is compressed using an electric steam compressor unit to obtain compressed steam. The compressed steam is introduced into the heat-absorbing side of the heat exchanger, and reheat steam is drawn from the reheat section pipeline of the steam turbine. After being regulated by the regulating valve, it is introduced into the heat-releasing side of the heat exchanger to heat the steam on the heat-absorbing side and obtain the heating steam. The parameter measurement unit is used to detect the pressure and temperature of the heating steam in real time and output pressure and temperature signals. The integrated control unit uses the deviation between the received pressure signal and the preset target pressure to adjust the operating speed of the compressor unit in a closed loop; it also uses the deviation between the received temperature signal and the preset target temperature to adjust the opening of the regulating valve in a closed loop. By controlling the flow rate of reheat steam entering the heat release side, the temperature of the heating steam is stabilized, ultimately achieving decoupled control and stable output of the heating steam pressure and temperature.

[0015] Optionally, the aforementioned method for utilizing turbine exhaust steam for heating based on an electric compressor further includes a fault switching step: When a fault is detected in the electric steam compressor unit or heat exchanger, the bypass valve is opened, and the operation of the compressor unit and heat exchanger is stopped at the same time, so that the steam is automatically switched to the bypass unit for heating.

[0016] Thirdly, the present invention provides a thermal power plant that employs a turbine exhaust cascade utilization heating system based on an electric compressor as described in the first aspect.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The turbine exhaust steam cascade utilization heating system based on an electric compressor provided by this invention first extracts steam, i.e., cold resteam, from the turbine high-pressure cylinder exhaust pipeline using a steam source extraction unit. Then, an electric steam compressor unit precisely upgrades the medium-to-low grade cold resteam to ensure its pressure parameters meet user requirements. Finally, high-grade reheat steam extracted from the reheat section is used as a heat source to compensate for the temperature of the pressurized cold resteam. This process forms a clear energy cascade utilization path: cold resteam serves as the basic working medium, bearing the main work load for pressure boosting, while reheat steam is only used to supplement grade gaps, with each making the best use of its function. Compared to the traditional approach of directly throttling and devaluing ultra-high parameter main steam, from a life-cycle analysis perspective, this invention significantly reduces the devaluation loss of high-quality usable energy, avoids the waste of high-energy-efficiency energy, and significantly improves overall energy utilization efficiency. In addition, this invention employs a dual closed-loop decoupled control strategy for pressure and temperature. Pressure control is achieved by a variable frequency motor driving the compressor through stepless speed regulation, resulting in good linearity and fast response, capable of responding to load changes within seconds. Temperature control is achieved through a regulating valve that precisely controls the flow rate of high-grade reheat steam entering the heat exchanger's heat release side, with a temperature control accuracy of ±2 degrees Celsius. Both operate independently yet cooperate under the coordination of the control unit, rapidly smoothing fluctuations in steam source parameters and changes in heat user load, ensuring highly stable external steam supply pressure and temperature, and meeting the stringent steam quality requirements of high-end industrial users.

[0018] The turbine exhaust gas cascade utilization heating system based on an electric compressor provided by this invention completely eliminates complex mechanical regulating mechanisms such as pressure matching devices, which have a high failure rate. The core equipment of the system, such as the steam compressor and shell-and-tube heat exchanger, are mature and universally used equipment that has been applied for a long time in industries such as petroleum, chemical, and power. They operate stably and reliably, have long maintenance cycles, and offer highly interchangeable spare parts. Because the system operates under mild conditions, it does not face the harsh conditions encountered by high-pressure differential regulating valves in traditional solutions, significantly extending the service life of the equipment. This effectively solves the problem in existing technologies where frequent maintenance leads to pipeline welding heat treatment times approaching the material's upper limit, reducing the risk to pipeline integrity.

[0019] All new equipment in this invention is externally installed. During the construction process, no drilling, welding or body modification is required for the core main equipment such as steam turbines and boilers, which completely avoids the risk of affecting the safe operation of the main equipment and has good economic efficiency and feasibility.

[0020] The system of this invention is equipped with a bypass unit, which can quickly switch to bypass operation when the main equipment fails, ensuring uninterrupted steam supply to users. The produced steam parameters are stable. Attached Figure Description

[0021] Figure 1The diagram shown is a process flow chart of a turbine exhaust gas cascade utilization heating system based on an electric compressor in one embodiment of the present invention. In the diagram: 100, Steam source unit; 101, Isolation valve; 102, Steam filter; 200, Electric steam compressor unit; 201, Steam compressor; 202, Variable frequency motor; 203, Safety valve; 301, Heat exchanger; 302, Regulating valve; 303, Check valve; 300, Parameter measurement unit; 400, Integrated control unit; 500, Bypass unit; 501, Bypass valve; 502, Bypass desuperheating and pressure reducing valve. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0023] Example 1

[0024] like Figure 1 As shown in the figure, an embodiment of the present invention introduces a turbine exhaust steam cascade utilization heating system based on an electric compressor, comprising: Steam source extraction unit 100, electric steam compressor unit 200, heat exchanger 301, regulating valve 302, parameter measurement unit 300, and integrated control unit 400; The inlet of the steam source extraction unit 100 is connected to the high-pressure cylinder exhaust pipeline of the steam turbine for extracting steam. The inlet of the electric steam compressor unit 200 is connected to the outlet of the steam source extraction unit 100, and is used to compress the extracted steam to obtain compressed steam. The heat exchanger 301 has a heat absorption side and a heat release side. The inlet of the heat absorption side is connected to the outlet of the electric steam compressor unit 200 to receive compressed steam. The outlet of the heat absorption side is used to output heating steam. The inlet of the heat release side is used to receive reheated steam after passing through the regulating valve 302. The outlet of the heat release side is connected to the high-pressure cylinder exhaust pipeline. The regulating valve 302 is installed on the pipeline between the reheat hot section pipeline and the heat exchanger 301 heat release side inlet, and is used to control the reheat steam flow rate entering the heat release side. The parameter measurement unit 300 is installed on the heating steam output pipeline to detect the pressure and temperature of the heating steam in real time and output pressure and temperature signals. The integrated control unit 400 is connected to the parameter measurement unit 300, the regulating valve 302, and the electric steam compressor unit 200 (not shown in the figure), respectively. It is used to adjust the operating speed of the compressor unit 200 in a closed loop according to the deviation between the received pressure signal and the preset target pressure. At the same time, it adjusts the opening of the regulating valve 302 in a closed loop according to the deviation between the received temperature signal and the preset target temperature. By controlling the reheat steam flow rate entering the heat release side, the temperature of the heating steam is stabilized, and finally, the decoupled control and stable output of the heating steam pressure and temperature are achieved.

[0025] In this embodiment, the steam source extraction unit 100 includes an isolation valve 101 and a steam filter device 102 connected sequentially along the steam flow direction. Specifically, a DN300 branch pipe is connected from a suitable location on the existing cold reheat steam main pipeline. A forged steel gate valve of PN100, Class 600 grade is selected as the isolation valve 101. To prevent pipeline impurities from damaging the compressor, a steam filter 102 capable of online backflushing is installed. A first steam source parameter monitoring point, namely TPO1 in the figure, is also set after the steam source extraction unit 100. An intelligent pressure transmitter and a sheathed thermocouple are used to detect the pressure and temperature of the extracted steam, i.e., the cold reheat steam, and to provide a feedforward signal for the integrated control unit.

[0026] In this embodiment, the electric steam compressor unit 200 includes a variable frequency motor 202, a steam compressor 202 driven by the variable frequency motor 202, and a safety valve 203 located at the outlet of the steam compressor 202. Specifically, based on typical design conditions: inlet pressure 2.5 MPa, temperature 330℃, outlet pressure 4.2 MPa, and mass flow rate 170 t / h, the selected steam compressor 202 is a multi-stage centrifugal steam compressor with a rated shaft power of approximately 3.8 MW. The variable frequency motor 202 is a 10 kV high-voltage variable frequency asynchronous motor and a matching vector control frequency converter. The safety valve 203 is a spring-loaded micro-opening safety valve; a second steam source parameter monitoring point, namely TPO2 in the figure, is also provided after the electric steam compressor unit to monitor the pressure and temperature of the compressed steam in real time.

[0027] In this embodiment, heat exchanger 301 is a shell-and-tube heat exchanger, with heat exchange between its absorber and exothermic sides via a tube bundle. The inlet of the exothermic side is connected to the reheater outlet (reheat hot section) to receive high-temperature reheat steam after passing through a regulating valve. The outlet of the exothermic side is connected to the high-pressure cylinder exhaust pipe (reheat cold section) to send the exothermic, low-temperature steam into the reheater for heating. A check valve 303 is installed at the exothermic outlet to prevent backflow of low-temperature steam. In this embodiment, the absorber side is designed according to the parameters of the heating steam, with a design pressure of 4.5 MPa and a design temperature of 400℃; the exothermic side is designed according to the parameters of the reheat hot section steam, with a design pressure of 4.5 MPa and a design temperature of 580℃. High-temperature and high-pressure resistant alloy steel is selected as the material.

[0028] In this embodiment, the regulating valve 302 is a cage-type regulating valve with linear flow characteristics.

[0029] In this embodiment, a bypass unit 500 is also provided between the main steam pipeline and the heating steam output pipeline for emergency heating in case of failure of the electric steam compressor unit or heat exchanger. The bypass unit 500 includes a bypass valve 501 and a bypass desuperheating and pressure reducing valve 502. One end of the bypass valve 501 is connected to the main steam pipeline, and the other end is connected to the inlet of the bypass desuperheating and pressure reducing valve 502. The outlet of the bypass desuperheating and pressure reducing valve 502 is connected to the heating steam output pipeline. Specifically, the bypass desuperheating and pressure reducing valve 502 is a key piece of equipment. To cope with pressure differences of up to 10 MPa and ensure the stability of the steam after pressure reduction, a multi-stage pressure reducing valve with a labyrinth sleeve structure is selected.

[0030] In this embodiment, the integrated control unit 400 includes a start-up and commissioning controller, a first PID controller, a second PID controller, and a fault switching controller, which are used to realize the start-up and commissioning of the entire system, automatic pressure regulation, automatic temperature regulation, and emergency switching under fault conditions, respectively.

[0031] Specifically, this embodiment applies to a 660MW supercritical, single-reheat, direct air-cooled condensing unit, model NZK660-24.2 / 566 / 566. The rated parameters of the unit's high-pressure cylinder exhaust steam (cold reheat steam) are approximately 4.725 MPa and 320℃. In actual operation, its pressure fluctuates between 1.8 and 3.5 MPa depending on the main unit load. The industrial park outside the plant requires stable high-parameter industrial steam with the following requirements: pressure 4.1 MPa, temperature 390℃, maximum flow rate 185 t / h, and average flow rate approximately 170 t / h.

[0032] (i) When the unit meets the conditions for cold start, first confirm that the main unit load is stable above 50% of the rated load, and that the cold reheat steam parameters meet the requirements of pressure greater than 1.8 MPa and temperature greater than 300℃. After receiving the operator's start command, the start-up controller executes the following sequence of controls: 1) The start-up controller issues a command to fully open isolation valve 101, while simultaneously slightly opening bypass desuperheating and pressure-reducing valve 502. A small amount of steam is used to slowly preheat the main pipeline and bypass pipeline to prevent excessive thermal stress in the pipeline. The warm-up time is controlled by a preset timer or feedback from the first and second steam source parameter monitoring points to ensure a uniform increase in pipeline temperature.

[0033] 2) After the warm-up is completed, the start-up controller sends a command to start the compressor variable frequency motor 202 and increase the compressor speed to the minimum stable speed, such as 2800 rpm. At this time, steam is still supplied to the heat user through the bypass valve 501 and the pressure reducing valve 502, and the system is in bypass operation state.

[0034] 3) The start-up controller enters the load transfer procedure. First, it slowly closes the bypass valve 501. Simultaneously, based on the feedback value from the parameter measurement unit 300, it gradually increases the compressor speed through the first PID controller. The first PID controller uses the pressure setpoint as the target, calculates the pressure deviation in real time, and outputs a speed adjustment command to ensure that the speed of the steam compressor 202 increases smoothly. During this process, the start-up controller coordinates the closing rate of the bypass valve 501 with the rate of increase of the steam compressor speed to ensure that the pressure fluctuation measured by the parameter measurement unit 300 does not exceed the allowable range. When the bypass valve 501 is fully closed, the steam compressor speed reaches the stable value of the corresponding load, and the outlet parameters are stable, the start-up controller determines that the system has successfully switched to main circuit operation, then exits the start-up mode and hands over control to the normally operating first PID controller and second PID controller, and the system enters fully automatic operation.

[0035] (ii) Once the system is put into automatic operation, the operator sets the target pressure to 4.1 MPa and the target temperature to 390℃ through the human-machine interface. At this time, the first PID controller and the second PID controller work in parallel to achieve decoupled control of pressure and temperature.

[0036] Pressure control: The first PID controller receives the pressure signal from the parameter measurement unit 300 in real time and calculates the deviation from the set pressure. When the feedback pressure is lower than the set value, the first PID controller increases its output, raising the speed command of the variable frequency motor 202, increasing the compressor speed, increasing the compression work on the reheat steam, and the outlet pressure rises accordingly. Conversely, when the feedback pressure is higher than the set value, the first PID controller decreases its output, reducing the compressor speed, causing the pressure to drop back to the set value. In actual operation, to cope with fluctuations in the steam source pressure within the range of 1.8-3.0 MPa, the compressor speed is typically adaptively adjusted within the range of 2800-3200 rpm.

[0037] Temperature control: The second PID controller receives the temperature signal from the parameter measurement unit 300 in real time and calculates the deviation from the set temperature. When the feedback temperature is lower than the set value, the second PID controller increases its output, opens the regulating valve 302, and increases the reheat steam flow into the heat exchanger 301 on the heat release side, thereby increasing the steam temperature on the heat absorption side. Conversely, when the feedback temperature is higher than the set value, the second PID controller decreases its output, closes the regulating valve 302, and reduces the heat source flow. In actual operation, the opening degree of the regulating valve 302 typically varies within the range of 15%-40% to maintain a constant temperature.

[0038] In this embodiment, the two PID controllers are independent of each other, and the sampling period of each controller is set to 200 ms to ensure that the system can respond quickly to parameter changes.

[0039] (iii) When the demand from heat users suddenly increases from 170 t / h to 185 t / h, the system outlet pressure will drop instantaneously. The first PID controller quickly detects the pressure deviation and increases the compressor speed command to a new equilibrium point within 2-3 seconds, thereby increasing the steam extraction rate and pressure rise. Within 20-30 seconds, the system flow rate and outlet pressure are restored to the set values. At the same time, the second PID controller detects the slight temperature drop caused by the increase in flow rate and automatically fine-tunes the opening of the regulating valve 302 to compensate for heat loss and maintain a stable outlet temperature. Throughout the process, the pressure and temperature controls are decoupled and do not interfere with each other, ensuring a high degree of stability in the steam supply quality.

[0040] Specifically, when a planned shutdown is required, the operator issues a shutdown command through the DCS, and the fault switching controller executes sequential control: first, it slowly opens the bypass desuperheating and pressure reducing valve 502 to a preset opening degree to establish bypass flow; then, it simultaneously and slowly reduces the compressor speed and closes the bypass valve 501, achieving a seamless switch from the main line to the bypass; finally, it shuts down the steam compressor 202 after reducing its speed to the minimum, and steam is supplied to the user entirely through the bypass. During the switching process, the fault switching controller monitors the outlet pressure in real time to ensure that pressure fluctuations do not exceed the allowable range.

[0041] When the main equipment, namely steam compressor 202 or heat exchanger 301, experiences a sudden malfunction requiring emergency shutdown, the fault switching controller responds immediately. Within 0.5 seconds, it simultaneously issues commands to quickly open bypass valve 501 and pressure reducing valve 502, and urgently stops the compressor to ensure uninterrupted heating. During bypass operation, the steam pressure is reduced to approximately 4.0-4.3 MPa at the output via pressure reducing valve 502, and the temperature decreases slightly, but still meets the user's basic production needs. Simultaneously, the fault switching controller sends an alarm signal to the DCS, prompting operators to address the fault promptly.

[0042] Through the coordinated operation of the aforementioned controllers, this invention achieves fully automatic, highly reliable, and high-quality operation of the cold resteam booster heating system, significantly improving energy utilization efficiency and system stability.

[0043] In summary, compared to the original emergency heating scheme that directly reduces the pressure of the main steam, this embodiment of the system reduces the consumption of high-grade main steam by approximately 0.15 tons per ton of qualified steam produced. Based on 6000 hours of operation per year and an average steam supply of 170 t / h, this translates to annual savings of approximately 12,000 tons of standard coal and a corresponding reduction of tens of thousands of tons of carbon dioxide emissions. From an operational reliability perspective, after the system was put into operation, it completely resolved the persistent problems of the original pressure matching valve stem bending, abnormal noise, and regulation failure, achieving 24 / 7 unattended automatic operation. The stability of the steam supply has been highly recognized by industrial users. From an economic perspective, the total investment for this embodiment is far lower than that of a newly built back-pressure unit. Considering the main energy-saving benefits, plus the reduced maintenance costs and failure losses due to improved reliability, the static investment payback period is expected to be between 3 and 4 years, demonstrating significant economic and social benefits.

[0044] Example 2

[0045] This invention provides a method for cascade utilization of turbine exhaust steam for heating based on an electric compressor, employing the turbine exhaust steam cascade utilization heating system based on an electric compressor as described in Example 1, comprising: Steam is extracted from the high-pressure cylinder exhaust pipeline of the steam turbine based on the steam source extraction unit; The extracted steam is compressed using an electric steam compressor unit to obtain compressed steam. The compressed steam is introduced into the heat-absorbing side of the heat exchanger, and reheat steam is drawn from the reheat section pipeline of the steam turbine. After being regulated by the regulating valve, it is introduced into the heat-releasing side of the heat exchanger to heat the steam on the heat-absorbing side and obtain the heating steam. The parameter measurement unit is used to detect the pressure and temperature of the heating steam in real time and output pressure and temperature signals. The integrated control unit uses the deviation between the received pressure signal and the preset target pressure to adjust the operating speed of the compressor unit in a closed loop; it also uses the deviation between the received temperature signal and the preset target temperature to adjust the opening of the regulating valve in a closed loop. By controlling the flow rate of reheat steam entering the heat release side, the temperature of the heating steam is stabilized, ultimately achieving decoupled control and stable output of the heating steam pressure and temperature.

[0046] Optionally, the aforementioned method for utilizing turbine exhaust steam for heating based on an electric compressor further includes a fault switching step: When a fault is detected in the electric steam compressor unit or heat exchanger, the bypass valve is opened, and the operation of the compressor unit and heat exchanger is stopped at the same time, so that the steam is automatically switched to the bypass unit for heating.

[0047] Example 3

[0048] This invention provides a thermal power plant equipped with a turbine exhaust gas cascade utilization heating system based on an electric compressor, as described in Embodiment 1.

[0049] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0050] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0051] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0052] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A turbine exhaust steam cascade utilization heating system based on an electric compressor, characterized in that, include: Steam source unit, electric steam compressor unit, heat exchanger, regulating valve, parameter measurement unit and integrated control unit; The inlet of the steam source extraction unit is connected to the high-pressure cylinder exhaust pipeline of the steam turbine for extracting steam. The inlet of the electric steam compressor unit is connected to the outlet of the steam source extraction unit, which is used to compress the extracted steam to obtain compressed steam. The heat exchanger has a heat absorption side and a heat release side. The inlet of the heat absorption side is connected to the outlet of the electric steam compressor unit to receive compressed steam. The outlet of the heat absorption side is used to output heating steam. The inlet of the heat release side is used to receive reheated steam after passing through the regulating valve. The outlet of the heat release side is connected to the high-pressure cylinder exhaust pipeline. The regulating valve is installed on the pipeline between the reheat hot section pipeline and the heat exchanger heat release side inlet, and is used to control the reheat steam flow rate entering the heat release side. The parameter measurement unit is installed on the heating steam output pipeline to detect the pressure and temperature of the heating steam in real time and output pressure and temperature signals. The integrated control unit is connected to the parameter measurement unit, the regulating valve, and the electric steam compressor unit respectively. It is used to adjust the operating speed of the compressor unit in a closed loop according to the deviation between the received pressure signal and the preset target pressure. At the same time, it adjusts the opening of the regulating valve in a closed loop according to the deviation between the received temperature signal and the preset target temperature. By controlling the reheat steam flow rate entering the heat release side, the temperature of the heating steam is stabilized, and finally, the decoupled control and stable output of the heating steam pressure and temperature are achieved.

2. The turbine exhaust gas cascade utilization heating system based on an electric compressor according to claim 1, characterized in that, The steam source extraction unit includes an isolation valve and a steam filter connected in sequence along the steam flow direction.

3. The turbine exhaust gas cascade utilization heating system based on an electric compressor according to claim 2, characterized in that, The electric steam compressor unit includes a variable frequency motor, a steam compressor driven by the variable frequency motor, and a safety valve located at the outlet of the steam compressor.

4. The turbine exhaust gas cascade utilization heating system based on an electric compressor according to claim 3, characterized in that, The heat exchanger is a shell-and-tube heat exchanger, in which heat exchange is performed between the heat absorption side and the heat release side through a tube bundle.

5. The turbine exhaust gas cascade utilization heating system based on an electric compressor according to claim 4, characterized in that, The outlet on the heat-exporting side is also equipped with a check valve to prevent steam from flowing in the opposite direction.

6. The turbine exhaust gas cascade utilization heating system based on an electric compressor according to claim 5, characterized in that, It also includes a bypass unit between the main steam pipeline and the heating steam output pipeline for emergency heating in case of failure of the electric steam compressor unit or heat exchanger.

7. The turbine exhaust gas cascade utilization heating system based on an electric compressor according to claim 6, characterized in that, The bypass unit includes a bypass valve and a bypass desuperheating and pressure reducing valve. One end of the bypass valve is connected to the main steam pipeline, and the other end is connected to the inlet of the bypass desuperheating and pressure reducing valve. The outlet of the bypass desuperheating and pressure reducing valve is connected to the heating steam output pipeline.

8. A method for cascade utilization of turbine exhaust steam for heating based on an electric compressor, employing the cascade utilization of turbine exhaust steam for heating system based on an electric compressor as described in any one of claims 1-6, characterized in that, include: Steam is extracted from the high-pressure cylinder exhaust pipeline of the steam turbine based on the steam source extraction unit; The extracted steam is compressed using an electric steam compressor unit to obtain compressed steam. The compressed steam is introduced into the heat-absorbing side of the heat exchanger, and reheat steam is drawn from the reheat section pipeline of the steam turbine. After being regulated by the regulating valve, it is introduced into the heat-releasing side of the heat exchanger to heat the steam on the heat-absorbing side and obtain the heating steam. The parameter measurement unit is used to detect the pressure and temperature of the heating steam in real time and output pressure and temperature signals. The integrated control unit uses the deviation between the received pressure signal and the preset target pressure to adjust the operating speed of the compressor unit in a closed loop; it also uses the deviation between the received temperature signal and the preset target temperature to adjust the opening of the regulating valve in a closed loop. By controlling the flow rate of reheat steam entering the heat release side, the temperature of the heating steam is stabilized, ultimately achieving decoupled control and stable output of the heating steam pressure and temperature.

9. The method for cascade utilization of steam turbine exhaust gas for heating based on an electric compressor according to claim 8, characterized in that, It also includes fault switching steps: When a fault is detected in the electric steam compressor unit or heat exchanger, the bypass valve is opened, and the operation of the compressor unit and heat exchanger is stopped at the same time, so that the steam is automatically switched to the bypass unit for heating.

10. A thermal power plant employing a turbine exhaust cascade utilization heating system based on an electric compressor as described in any one of claims 1-8.

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