Bypass steam supply system control method and steam supply system

Abstract

This application discloses a bypass steam supply system control method and steam supply system, including: when the main steam supply system of a cogeneration unit is in an abnormal state, entering a bypass steam supply state; opening the high-pressure bypass pressure regulating valve to control the reheat steam pressure; opening the high-pressure bypass water spray desuperheating regulating valve group to control the high-pressure bypass outlet steam temperature; reducing boiler power; closing all low-pressure steam supply valve groups; when the high-pressure steam supply pressure exceeds a preset abnormal high-pressure threshold, opening the low-pressure bypass pressure regulating valve group until the high-pressure steam supply pressure is lower than or equal to a preset normal high-pressure threshold; opening the high-pressure to low-pressure emergency connection steam supply regulating valve group to control the emergency low-pressure steam supply pressure and emergency low-pressure steam supply temperature. This application additionally adds a bypass steam supply PID automatic control loop for the bypass steam supply state, which can realize fully automatic control and continue to provide two-stage industrial steam supply under shutdown-but-uninterrupted boiler operation conditions, improving safety and stability.

Description

Technical Field

[0001] This application relates to the field of thermal automatic control technology for coal-fired power generating units, and in particular to a bypass steam supply system control method and steam supply system. Background Technology

[0002] Large-scale combined heat and power (CHP) units must have both power generation and heating functions. They must have good heating reliability during the external steam supply process. In particular, for industrial production projects such as petrochemicals that have high requirements for the pressure and temperature parameters of the steam used, CHP units are required to have the ability to continue to supply high-quality steam safely and stably even when the boiler is shut down.

[0003] In existing technologies, multi-stage steam supply is generally ensured by storing steam in advance or reheating low-temperature steam using a separate thermal storage device. Of course, more complex systems use bypass steam supply methods. However, existing bypass steam supply methods require additional steam supply lines, which makes the lines complex and usually can only restore a single steam supply. For example, it can only continue high-pressure steam supply or low-pressure steam supply, making it difficult to efficiently guarantee the continued supply of high-quality two-stage industrial steam.

[0004] Therefore, a bypass steam supply system control method is needed to ensure that the boiler does not trip and continues to provide high-quality two-stage industrial steam when the steam turbine or generator suddenly fails and stops, so as to realize safe and reliable industrial steam supply for cogeneration units under all operating conditions. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a bypass steam supply system control method and steam supply system, which can continue to provide high-quality two-stage industrial steam without tripping the boiler when the steam turbine or generator suddenly fails and shuts down, thus realizing safe and reliable industrial steam supply for cogeneration units under all operating conditions. The specific solution is as follows:

[0006] A bypass steam supply system control method includes:

[0007] When the main steam supply system of a cogeneration unit is in an abnormal state, it will switch to bypass steam supply mode.

[0008] The high-pressure bypass pressure regulating valve is automatically controlled by a separate bypass steam supply PID automatic control loop to control the hot reheat steam pressure to the first target value.

[0009] The bypass steam supply PID automatic control loop is used to automatically control the high-pressure bypass water spray desuperheating regulating valve group to control the high-pressure bypass outlet steam temperature to the second target value.

[0010] Reduce the boiler power to the third target value within a preset time;

[0011] Close all valve groups for low-pressure steam supply and keep the hot reheat steam to high-pressure steam supply valve group in the state that was before the main steam supply system was in an abnormal state.

[0012] When the high-pressure steam supply pressure exceeds the preset abnormal high-pressure threshold, the low-pressure bypass pressure regulating valve group is automatically opened using the bypass steam supply PID automatic control loop until the high-pressure steam supply pressure is lower than or equal to the preset normal high-pressure threshold.

[0013] The bypass steam supply PID automatic control loop is used to automatically control the high-pressure to low-pressure emergency connection steam supply regulating valve group, control the emergency low-pressure steam supply pressure to the fourth target value, and control the emergency low-pressure steam supply temperature to the fifth target value.

[0014] Optionally, the process of switching to bypass steam supply mode when the main steam supply system of the cogeneration unit is in an abnormal state includes:

[0015] When the total power generation of the cogeneration unit exceeds the preset power generation threshold and / or the turbine of the cogeneration unit fails and / or the generator fails, the unit enters the bypass steam supply state.

[0016] Optionally, the process of automatically controlling the high-pressure bypass pressure regulating valve using a separate bypass steam supply PID automatic control loop to control the hot reheat steam pressure to the first target value includes:

[0017] The high-pressure bypass pressure regulating valve is quickly opened to the first preset opening degree. After the first delay, the high-pressure bypass pressure regulating valve automatic control loop is automatically engaged to control the hot resteam pressure. At the moment the automatic control is engaged, the hot resteam pressure value before shutdown is memorized and assigned to the corresponding first PID controller as the first target value, so as to use the first PID controller to control the hot resteam pressure to the first target value.

[0018] The first preset opening degree is obtained from the first real-time piecewise linear function of the power generation before the turbine or generator failure.

[0019] Optionally, the process of automatically controlling the high-pressure bypass water spray desuperheating regulating valve group using the bypass steam supply PID automatic control loop to control the high-pressure bypass outlet steam temperature to the second target value includes:

[0020] The high-pressure bypass spray desuperheating shut-off valve is interlocked and the high-pressure bypass spray desuperheating regulating valve is quickly opened to the second preset opening degree. After the second delay, the high-pressure bypass spray desuperheating regulating valve automatic control circuit is automatically engaged to control the high-pressure bypass outlet steam temperature. At the moment the automatic control is engaged, the actual value of the high-pressure bypass outlet steam temperature before shutdown is memorized and assigned to the second PID controller as the second target value, so as to use the second PID controller to control the high-pressure bypass outlet steam temperature to the second target value.

[0021] The second preset opening degree is obtained from the second real-time piecewise linear function of the power generation before the turbine or generator failure.

[0022] Optionally, the process of reducing the boiler power to the third target value within a preset time includes:

[0023] Reduce the coal feed rate and / or water feed rate and / or primary air volume and / or secondary air volume of the boiler until the boiler power reaches the third target value.

[0024] Optionally, the process of automatically controlling the low-pressure bypass pressure regulating valve group using the bypass steam supply PID automatic control loop until the high-pressure steam supply pressure is lower than or equal to a preset normal high-pressure threshold includes:

[0025] When the high-pressure steam supply pressure is higher than the preset abnormal high-pressure threshold, the interlock automatically opens the low-pressure bypass pressure regulating valve to the third preset opening degree. When the high-pressure steam supply pressure is lower than or equal to the preset normal high-pressure threshold, the interlock automatically closes the low-pressure bypass pressure regulating valve. The low-pressure bypass water spray desuperheating regulating valve is automatically adjusted according to the steam temperature deviation after the valve throughout the process.

[0026] The third preset opening degree is obtained based on the third real-time broken line function of the high-pressure steam supply pressure, which can better and more appropriately open and close the low-pressure bypass pressure regulating valve according to the high-pressure steam supply pressure adjustment needs.

[0027] Optionally, the process of automatically controlling the high-pressure to low-pressure emergency connection steam supply regulating valve group using the bypass steam supply PID automatic control loop, controlling the emergency low-pressure steam supply pressure to the fourth target value, and controlling the emergency low-pressure steam supply temperature to the fifth target value, includes:

[0028] The interlock opens the high-pressure to low-pressure emergency communication steam supply shut-off valve, quickly opens the fourth preset opening degree of the high-pressure to low-pressure emergency communication steam supply regulating valve, and after the third delay, automatically engages the automatic control loop of the high-pressure to low-pressure emergency communication steam supply regulating valve to control the low-pressure steam supply pressure. At the moment of automatic engagement, the low-pressure steam supply pressure value before shutdown is memorized and assigned to the third PID controller corresponding to the high-pressure to low-pressure emergency communication steam supply regulating valve as the fourth target value, so as to use the third PID controller to control the low-pressure steam supply pressure to the fourth target value.

[0029] The high-pressure to low-pressure emergency communication steam and water spray desuperheating regulating valve is opened to its fifth preset opening degree. After the fourth delay, the automatic control loop of the high-pressure to low-pressure emergency communication steam and water spray desuperheating regulating valve is automatically activated to control the low-pressure steam supply temperature. Upon activation, the low-pressure steam supply temperature value before shutdown is memorized and assigned to the fourth PID controller corresponding to the high-pressure to low-pressure emergency communication steam and water spray desuperheating regulating valve as the fifth target value. The fourth PID controller is then used to control the low-pressure steam supply temperature to the fifth target value.

[0030] The fourth preset opening degree is obtained based on the fourth real-time broken line function of the low-pressure steam supply flow rate before the turbine or generator failure; the fifth preset opening degree is obtained based on the fifth real-time broken line function of the low-pressure steam supply flow rate before the turbine or generator failure.

[0031] Optional, also includes:

[0032] When the boiler trips after the fifth delay, or the boiler main fuel trips after the sixth delay, or the main steam pressure before the turbine is lower than the preset main steam setpoint and is delayed for the seventh delay, or the turbine is started and the high-pressure bypass pressure regulating valve is closed for the eighth delay, the status signal of the bypass steam supply system that stops the boiler during shutdown will be reset, and the main steam supply system will start working and supply steam.

[0033] Optional, also includes:

[0034] When the high-pressure bypass pressure regulating valve is in manual mode, it receives the bypass steam supply status control signal input by the user to control the steam supply system to enter or exit the bypass steam supply status.

[0035] This application also discloses a steam supply system that uses the bypass steam supply system control method described above, including: a boiler, a steam turbine, a generator, a three-stage extraction steam to low-pressure steam supply shut-off valve, a three-stage extraction steam to low-pressure steam supply regulating valve, a hot reheat steam to high-pressure steam supply shut-off valve, a hot reheat steam to high-pressure steam supply regulating valve, a high-pressure bypass pressure regulating valve, a high-pressure bypass water spray desuperheating shut-off valve, a high-pressure bypass water spray desuperheating regulating valve, a high-pressure to low-pressure emergency communication steam supply shut-off valve, a high-pressure to low-pressure emergency communication steam supply regulating valve, a high-pressure to low-pressure emergency communication steam supply water spray desuperheating shut-off valve, a high-pressure to low-pressure emergency communication steam supply water spray desuperheating regulating valve, a low-pressure bypass pressure regulating valve, a low-pressure bypass water spray desuperheating shut-off valve, a low-pressure bypass water spray desuperheating regulating valve, a steam turbine high-pressure inlet valve group, and a steam turbine intermediate-pressure inlet valve group;

[0036] The boiler bypass steam supply output terminal is connected to the input terminal of the turbine intermediate-pressure inlet steam valve group, the input terminal of the high-pressure to low-pressure emergency connection steam supply shut-off valve, the input terminal of the hot reheat steam to high-pressure steam supply shut-off valve, and the input terminal of the low-pressure bypass pressure regulating valve. The low-pressure bypass water spray desuperheating shut-off valve and the low-pressure bypass water spray desuperheating regulating valve are connected in sequence. The output terminal of the low-pressure bypass water spray desuperheating regulating valve is used to spray water to cool the steam output from the low-pressure bypass pressure regulating valve. The output end of the high-pressure steam supply shut-off valve is connected to the input end of the hot reheat steam to high-pressure steam supply regulating valve, and the output end of the hot reheat steam to high-pressure steam supply regulating valve serves as the high-pressure steam supply end. The output end of the high-pressure to low-pressure emergency communication steam supply shut-off valve is connected to the input end of the high-pressure to low-pressure emergency communication steam supply regulating valve, and the output end of the high-pressure to low-pressure emergency communication steam supply regulating valve serves as the emergency low-pressure steam supply end. The high-pressure to low-pressure emergency communication steam supply water spray desuperheating shut-off valve and the high-pressure to low-pressure emergency communication steam supply water spray desuperheating regulating valve... The following components are connected sequentially: the output end of the high-pressure to low-pressure emergency communication steam-water spray desuperheating regulating valve is used to supply emergency low-pressure steam and water for cooling; the output end of the turbine intermediate-pressure steam inlet valve group is connected to the input end of the three-stage extraction steam to low-pressure steam supply shut-off valve; the output end of the three-stage extraction steam to low-pressure steam supply shut-off valve is connected to the input end of the three-stage extraction steam to low-pressure steam supply regulating valve; and the output end of the three-stage extraction steam to low-pressure steam supply regulating valve serves as the low-pressure steam supply end. The boiler... The main steam output terminal is connected to the input terminal of the high-pressure bypass pressure regulating valve and the input terminal of the turbine high-pressure inlet steam valve group, respectively. The output terminal of the turbine high-pressure inlet steam valve group is connected to the input terminal of the turbine. The output terminal of the high-pressure bypass pressure regulating valve outputs depressurized main steam. The high-pressure bypass spray desuperheating shut-off valve and the high-pressure bypass spray desuperheating regulating valve are connected in sequence. The output terminal of the high-pressure bypass spray desuperheating regulating valve sprays water to cool the depressurized main steam output from the output terminal of the high-pressure bypass pressure regulating valve.

[0037] In this application, the bypass steam supply system control method includes: when the main steam supply system of the cogeneration unit is in an abnormal state, entering the bypass steam supply state; opening the high-pressure bypass pressure regulating valve to control the reheat steam pressure; opening the high-pressure bypass spray desuperheating regulating valve group to control the high-pressure bypass outlet steam temperature; reducing boiler power; closing all low-pressure steam supply valve groups to maintain the reheat steam to high-pressure steam supply valve group in the state before the main steam supply system was in an abnormal state; when the high-pressure steam supply pressure is higher than the preset abnormal high-pressure threshold, opening the low-pressure bypass pressure regulating valve group until the high-pressure steam supply pressure is lower than or equal to the preset normal high-pressure threshold; opening the high-pressure to low-pressure emergency connection steam supply regulating valve group to control the emergency low-pressure steam supply pressure and emergency low-pressure steam supply temperature.

[0038] This application adds an additional bypass steam supply PID automatic control loop for bypass steam supply status. By controlling the corresponding valve groups through this automatic control loop, it is possible to continue to provide two-stage industrial steam supply under special operating conditions of shutdown without boiler interruption. Furthermore, it fully realizes automatic control, reduces the impact of human factors and operation and maintenance costs, and improves safety and stability. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0040] Figure 1 This is a schematic flowchart of a bypass steam supply system control method disclosed in an embodiment of this application;

[0041] Figure 2 This is a schematic diagram of another bypass steam supply system control method disclosed in an embodiment of this application;

[0042] Figure 3 This is a logic diagram for the memory formation and reset of the status signal of the bypass steam supply system during shutdown in the embodiments of this application.

[0043] Figure 4 This is a control logic diagram of the high-pressure bypass pressure regulating valve in two modes in the embodiments of this application;

[0044] Figure 5 This is a logic diagram of the override control and automatic adjustment of the high-pressure bypass spray desuperheating regulating valve in the embodiments of this application;

[0045] Figure 6 This is a logic diagram of the quick-opening and quick-closing method of the low-pressure bypass pressure regulating valve in the embodiment of this application, which allows for steam supply without shutting down the boiler during shutdown.

[0046] Figure 7 This is a control logic diagram of the high-pressure to low-pressure emergency communication steam supply pressure regulating valve in the embodiments of this application;

[0047] Figure 8 This is a control logic diagram of the high-pressure to low-pressure emergency communication steam injection desuperheating regulating valve in the embodiments of this application;

[0048] Figure 9 This is a schematic diagram of the bypass steam supply system for shutdown without shutting down the boiler, as described in an embodiment of the present invention.

[0049] Figure 9 middle:

[0050] 1-Supercritical boiler, 2-Steam turbine, 3-Generator, 4-Three-stage extraction steam to low-pressure steam supply shut-off valve, 5-Three-stage extraction steam to low-pressure steam supply regulating valve, 6-Hot reheat steam to high-pressure steam supply shut-off valve, 7-Hot reheat steam to high-pressure steam supply regulating valve, 8-High-pressure bypass pressure regulating valve, 9-High-pressure bypass spray desuperheating shut-off valve, 10-High-pressure bypass spray desuperheating regulating valve, 11-High-pressure to low-pressure emergency communication steam supply pressure shut-off valve, 12-High-pressure to low-pressure emergency communication steam supply pressure... 13-Pressure regulating valve, 14-Pressure-to-low-pressure emergency communication steam supply pressure spray desuperheating shut-off valve, 15-Low-pressure bypass pressure regulating valve, 16-Low-pressure bypass spray desuperheating shut-off valve, 17-Low-pressure bypass spray desuperheating regulating valve, 18-Turbine high-pressure inlet steam valve group, 19-Turbine intermediate-pressure inlet steam valve group, 20-Turbine rotating diaphragm, 80-Boiler reheater system, 81-Deaerator, 82-Steam recovery unit.

[0051] Figure 3 middle:

[0052] 21 - Pulse, 22 - Logic OR, 23 - High limit comparison, 24 - Delayed disconnect, 25 - Logic AND, 26 - Delayed close, 27 - Low limit comparison, 28 - First RS flip-flop, 29 - Second RS flip-flop, 30 - Second logic OR.

[0053] Figure 4 middle:

[0054] 31-PID controller, 32-Manual operator (control valve command human-machine interface operator), 33-Pulse generator, 34-Selector switcher, 35-Polylinear function calculator.

[0055] Figure 5 middle:

[0056] 41 - Pulse generator; 42 - Piecewise linear function arithmetic unit.

[0057] Figure 6 middle:

[0058] 51 - Lower limit comparison, 52 - Upper limit comparison, 53 - Piece line function calculator.

[0059] Figure 7 middle:

[0060] 61 - Pulse generator, 62 - Piecewise linear function arithmetic unit.

[0061] Figure 8 middle:

[0062] 71 - Pulse generator, 72 - Piecewise linear function arithmetic unit. Detailed Implementation

[0063] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0064] This application discloses a bypass steam supply system control method. See also... Figure 1 As shown, the method includes:

[0065] Specifically, the main steam supply system of a cogeneration unit includes the boiler, turbine, generator, reheat steam to high-pressure steam supply valve group, and three-stage extraction steam to low-pressure steam supply valve group. Under normal circumstances, the main steam from the boiler enters the high-pressure cylinder of the turbine through the high-pressure inlet valve group to perform work and exhaust steam. Then, after being heated by the boiler reheater system, reheat steam is output from the boiler. The reheat steam is used for high-pressure steam supply to the outside, and part of it is extracted after performing work in the intermediate-pressure cylinder of the turbine to supply low-pressure steam to the outside. However, during operation, the turbine and / or generator may malfunction, resulting in turbine tripping and generator disconnection. This prevents the main steam from continuing to perform work and generate electricity through the high-pressure and low-pressure cylinders of the turbine, causing the main steam supply system to be interrupted, the steam consumption to decrease sharply, and the external two-stage steam supply to the outside. Therefore, other circuits are needed to continue supplying steam to the outside while ensuring system safety.

[0066] S11: When the main steam supply system of a cogeneration unit is in an abnormal state, it enters the bypass steam supply state.

[0067] Specifically, when a turbine and / or generator malfunctions, such as a turbine tripping or generator disconnection, the main steam supply system of the current cogeneration unit is considered to be in an abnormal state. At this time, the main steam automatic control loop used under normal conditions can no longer cope with the current situation. Therefore, it enters the bypass steam supply state so that steam can be continuously supplied to the outside through the bypass and low-pressure two-stage steam supply when controlling each valve group through another separate bypass steam supply PID automatic control loop, thus maintaining system stability.

[0068] S12: Automatically control the high-pressure bypass pressure regulating valve using a separate bypass steam supply PID automatic control loop to control the reheat steam pressure to the first target value.

[0069] Specifically, the PID automatic control loop corresponding to the high-pressure bypass pressure regulating valve in the separate bypass steam supply PID automatic control loop can be used to control the opening and closing degree of the high-pressure bypass pressure regulating valve, thereby controlling the hot resteam pressure in the steam pipeline and maintaining the hot resteam pressure near the set first target value.

[0070] Specifically, by adjusting the opening size of the high-pressure bypass pressure regulating valve, the amount of steam discharged after the valve is controlled, thereby regulating the hot reheat steam pressure after the valve. Through the corresponding PID automatic control loop, the current hot reheat steam pressure is used as the actual measured value as the input. By adjusting the opening size of the high-pressure bypass pressure regulating valve, the hot reheat steam pressure after the valve continuously approaches the set first target value, thus achieving automatic control.

[0071] S13: The high-pressure bypass water spray desuperheating regulating valve group is automatically controlled by the bypass steam supply PID automatic control loop to control the high-pressure bypass outlet steam temperature to the second target value.

[0072] Specifically, by utilizing the PID automatic control loop corresponding to the high-pressure bypass water spray desuperheating regulating valve group in the separate bypass steam supply PID automatic control loop, the opening and closing degree of the high-pressure bypass water spray desuperheating regulating valve group are controlled, thereby controlling the high-pressure bypass outlet steam temperature in the steam pipeline and maintaining the high-pressure bypass outlet steam temperature near the set second target value.

[0073] Specifically, the high-pressure bypass water spray desuperheating regulating valve assembly may include a high-pressure bypass water spray desuperheating regulating valve and a high-pressure bypass water spray desuperheating shut-off valve. The high-pressure bypass water spray desuperheating regulating valve controls the amount of water sprayed, thereby indirectly controlling the steam temperature at the high-pressure bypass outlet downstream of the valve. The high-pressure bypass water spray desuperheating shut-off valve, located upstream of the high-pressure bypass water spray desuperheating regulating valve, determines whether to supply water for desuperheating, ensuring a safer cut-off of desuperheating water when the steam temperature is too low or the water spray desuperheating system does not need to be operated. It is understood that for desuperheating to occur, both the high-pressure bypass water spray desuperheating regulating valve and the high-pressure bypass water spray desuperheating shut-off valve need to be open.

[0074] Specifically, by adjusting the opening size of the high-pressure bypass water spray desuperheating regulating valve, the amount of water sprayed after the valve is controlled, thereby regulating the steam temperature at the outlet of the high-pressure bypass. The corresponding PID automatic control loop uses the current measured value of the high-pressure bypass outlet steam temperature as the input, and by adjusting the opening size of the high-pressure bypass water spray desuperheating regulating valve, the steam temperature at the outlet of the high-pressure bypass after the valve continuously approaches the set second target value, thus achieving automatic control.

[0075] S14: Reduce boiler power to the third target value within a preset time.

[0076] Specifically, since the original steam-using equipment such as steam turbines or generators failed to operate normally, the steam consumption decreased sharply. Therefore, there is no need for the boiler to provide more heat power to output more high-temperature steam. For this reason, it is necessary to quickly reduce the boiler power to the preset third target value within a preset time, reduce the heat released by the boiler, reduce steam output, and make the boiler combustion rate and heating steam flow match to prevent the boiler from overheating and overpressure.

[0077] Specifically, reducing boiler power can be achieved by reducing the amount of coal and / or water and / or primary air and / or secondary air, etc., until the boiler power reaches the preset third target value.

[0078] S15: Close all valve groups of low-pressure steam supply and keep the hot reheat steam to high-pressure steam supply valve group in the state before the main steam supply system was in an abnormal state.

[0079] Specifically, if the turbine and / or generator malfunction, close all low-pressure steam supply valve groups downstream of it, shut off the original low-pressure steam supply channels, ensure the safe shutdown of the turbine, and prevent reverse steam intake and water vapor ingress into the intermediate-pressure cylinder. Maintain the hot reheat steam to high-pressure steam supply valve group in the state it was in before the main steam supply system malfunctioned, ensuring the high-pressure steam supply channels remain unobstructed.

[0080] S16: When the high-pressure steam supply pressure is higher than the preset abnormal high-pressure threshold, the low-pressure bypass pressure regulating valve group is automatically opened using the bypass steam supply PID automatic control loop until the high-pressure steam supply pressure is lower than or equal to the preset normal high-pressure threshold.

[0081] Specifically, if the steam turbine and / or generator cannot continue to use steam due to a malfunction, and the boiler cannot immediately reduce its steam production, the pressure in the steam pipeline will temporarily rise due to the reduced steam consumption. At this time, if the corresponding pressure detection equipment detects that the high-pressure steam supply pressure is higher than the preset abnormal high-pressure threshold, the PID automatic control loop corresponding to the low-pressure bypass pressure regulating valve group in the bypass steam supply PID automatic control loop can be used to open the low-pressure bypass pressure regulating valve group to release steam, discharging excess steam to equipment such as a steam recovery unit, reducing the high-pressure steam pressure in the high-pressure steam supply pipeline until the high-pressure steam supply pressure is lower than or equal to the preset normal high-pressure threshold. Then, the low-pressure bypass pressure regulating valve group can be automatically closed to stop the steam release.

[0082] S17: Utilize the bypass steam supply PID automatic control loop to automatically control the high-pressure to low-pressure emergency contact steam supply regulating valve group, control the emergency low-pressure steam supply pressure to the fourth target value, and control the emergency low-pressure steam supply temperature to the fifth target value.

[0083] Specifically, the high-pressure to low-pressure emergency communication steam supply regulating valve group includes a high-pressure to low-pressure emergency communication steam supply shut-off valve, a high-pressure to low-pressure emergency communication steam supply regulating valve, a high-pressure to low-pressure emergency communication steam supply water spray shut-off valve, and a high-pressure to low-pressure emergency communication steam supply water spray regulating valve. The high-pressure to low-pressure emergency communication steam supply shut-off valve and the high-pressure to low-pressure emergency communication steam supply regulating valve can regulate the downstream steam output, while the high-pressure to low-pressure emergency communication steam supply water spray shut-off valve and the high-pressure to low-pressure emergency communication steam supply water spray regulating valve can regulate the downstream water spray output, thereby regulating the downstream emergency low-pressure steam supply temperature. Therefore, using the PID automatic control loop corresponding to the high-pressure to low-pressure emergency communication steam supply regulating valve group in the bypass steam supply PID automatic control loop, the corresponding regulating valves are continuously adjusted using the current emergency low-pressure steam supply pressure and the current emergency low-pressure steam supply temperature as actual measured values ​​(i.e., input quantities), so that the emergency low-pressure steam supply pressure approaches the preset fourth target value, and the emergency low-pressure steam supply temperature approaches the preset fifth target value.

[0084] It should be noted that S12 to S17 are steps that can be asynchronous and parallelized. Each step can be automatically triggered and adjusted according to the triggering conditions, and there is no strict order.

[0085] As can be seen, this application embodiment adds an additional bypass steam supply PID automatic control loop for bypass steam supply status. By controlling the corresponding valve groups through this automatic control loop, it is possible to continue to provide two-stage industrial steam supply under special operating conditions of shutdown without boiler interruption, and fully realize automatic control, reduce the impact of human factors and operation and maintenance costs, and improve safety and stability.

[0086] This application discloses a specific control method for a bypass steam supply system. Compared to the previous embodiment, this embodiment further explains and optimizes the technical solution. See also... Figure 2 and Figure 3 As shown, specifically:

[0087] S21: When the total power generation of the cogeneration unit is higher than the preset power generation threshold and / or the turbine and / or generator of the cogeneration unit fails, the unit enters the bypass steam supply state.

[0088] For details, see Figure 3 As shown, when the generator and / or turbine fails, for example, Figure 3 When the turbine trips or the generator disconnects, and the total power generation of the combined heat and power unit exceeds the preset power generation threshold, the corresponding first RS trigger is activated. This causes the automatic control system to enter the bypass steam supply state without shutting down the boiler, and the main steam supply system is switched to the bypass steam supply PID automatic control loop.

[0089] For details, see Figure 3 As shown, when the power generation of the cogeneration unit is greater than the preset power generation threshold 23 during normal operation, if the turbine 2 trips or the generator 3 disconnects, the signal of the bypass steam supply system that is set to "1" will be set, which means that the bypass steam supply system will be entered. Figure 3 When the total power generation exceeds the preset power generation threshold 23 and a delayed disconnection arithmetic unit 24 is used, it ensures that after the unit's power generation falls below the threshold 23, the system waits for the delay time before returning to "0". This ensures that the turbine trip signal or generator disconnection signal and the unit power generation below the threshold 23 signal can be logically ANDed within the same DCS controller scan cycle, accurately triggering the shutdown-without-furnace bypass steam supply system signal to the "1" state. A separate pulser is used for turbine 2 tripping or generator 3 disconnection states. It correctly determines whether to enter the shutdown-without-furnace bypass steam supply state only within the short pulse duration of the turbine tripping pulse or the short pulse duration of the generator disconnection pulse. This prevents erroneous triggering of the shutdown-without-furnace bypass steam supply state when thermal control personnel need to force a power generation signal during shutdown or unit shutdown maintenance.

[0090] S22: When the boiler trips after the fifth delay, or the boiler main fuel trips after the sixth delay, or the main steam pressure before the turbine is lower than the preset main steam setpoint and is delayed for the seventh delay, or the turbine is started and the high-pressure bypass pressure regulating valve is closed for the eighth delay, the status signal of the bypass steam supply system is reset and the main steam supply system starts working.

[0091] For details, see Figure 3 As shown, when the boiler trips after the fifth delay, or the boiler main fuel trips after the sixth delay, or the main steam pressure before the turbine is lower than the preset main steam setpoint and is delayed for the seventh delay, or the turbine is started and the high-pressure bypass pressure regulating valve is closed for the eighth delay, the status signal of the bypass steam supply system will be reset, and the turbine and generator will enter normal operation, with two-stage heating provided by the main steam supply system, and the bypass steam supply system will enter standby state.

[0092] Specifically, the purpose of setting the fifth delay is to ensure that the boiler trips and shuts down, and that there is indeed no ability to continue heating after a certain period of time, taking into account the boiler's inertia and heat storage capacity. The purpose of setting the sixth delay is to ensure that the boiler's main fuel trips and is interrupted, and that there is indeed no ability to continue heating after a certain period of time, taking into account the boiler's inertia and heat storage capacity. The purpose of setting the seventh delay is to confirm that the main steam pressure in front of the turbine has truly dropped to the low set value and that the boiler has indeed no ability to continue heating. The purpose of setting the eighth delay is to confirm that the turbine restarts and resumes normal heating, and that the bypass system is closed and enters the main steam supply system state.

[0093] S23: When the high-pressure bypass pressure regulating valve is in manual mode, it receives the bypass steam supply status control signal input by the user to control the steam supply system to enter or exit the bypass steam supply status.

[0094] For details, see Figure 3 As shown, if the high-pressure bypass pressure regulating valve is in manual mode, the user can manually reset the status signal of the bypass steam supply system during shutdown by inputting a device such as a keyboard, and manually adjust the parameters of each valve. For example, if the high-pressure bypass pressure regulating valve is in manual mode, the operator can also manually set the high-pressure bypass pressure regulating valve to control the reheat steam pressure, i.e., the high-pressure steam supply pressure mode. This means the operator can flexibly choose between two operating modes for the high-pressure bypass pressure regulating valve. First, the high-pressure bypass pressure regulating valve can be released from manual mode, and then manually set to control the reheat steam pressure in the bypass steam supply system mode to ensure stable industrial steam supply. Alternatively, the operator can manually reset the high-pressure bypass pressure regulating valve to control the main steam pressure before the turbine in the turbine and generator restart mode, while also ensuring stable industrial steam supply.

[0095] S24: Automatically control the high-pressure bypass pressure regulating valve using a separate bypass steam supply PID automatic control loop to control the reheat steam pressure to the first target value.

[0096] For details, see Figure 4 As shown, the high-pressure bypass pressure regulating valve is quickly opened to the first preset opening degree using the time reserved by the first delay for override control. After the first delay, the high-pressure bypass pressure regulating valve automatic control loop is automatically engaged to control the hot reheat steam pressure. At the moment the automatic control is engaged, the hot reheat steam pressure value before shutdown is memorized and assigned to the corresponding first PID controller as the first target value, so as to use the first PID controller to control the hot reheat steam pressure to the first target value.

[0097] For details, see Figure 4 As shown, the first delay is achieved by pulser 33. Pulser 33 sets the pulse time to the first delay duration, so that the high-pressure bypass pressure regulating valve overshoots and forces the output to the first preset opening degree within the first delay time.

[0098] The first preset opening degree is obtained based on the first real-time piecewise linear function 35(F1(x)) of the power generation before the turbine or generator failure; after automatic control, the operator can manually modify the first target value according to the working conditions.

[0099] S25: The high-pressure bypass water spray desuperheating regulating valve group is automatically controlled by the bypass steam supply PID automatic control loop to control the high-pressure bypass outlet steam temperature to the second target value.

[0100] For details, see Figure 5As shown, when the high-pressure bypass pressure regulating valve is opened, the high-pressure bypass spray desuperheating shut-off valve is interlocked and the high-pressure bypass spray desuperheating regulating valve is quickly opened to the second preset opening degree for override control. After the second delay, the automatic control loop of the high-pressure bypass spray desuperheating regulating valve is automatically engaged to control the high-pressure bypass outlet steam temperature. At the moment the automatic control is engaged, the actual value of the high-pressure bypass outlet steam temperature before shutdown is memorized and assigned to the second PID controller as the second target value, so as to use the second PID controller to control the high-pressure bypass outlet steam temperature to the second target value.

[0101] For details, see Figure 5 As shown, the second delay is achieved by pulser 41. Pulser 41 sets the pulse time to the second delay duration, so that the high-pressure bypass water spray desuperheating regulating valve overshoots and forces the output to the second preset opening degree during the second delay period.

[0102] The second preset opening degree is obtained based on the second real-time piecewise linear function 42(F2(x)) of the power generation before the turbine or generator failure; after automatic control, the operator can manually modify the second target value according to the operating conditions.

[0103] S26: Reduce boiler power to the third target value within a preset time.

[0104] For example, the total coal feed rate of the boiler is rapidly reduced to 48% of the actual total coal feed rate before the turbine or generator failure at a rate of 150% MCR / Min (this set value needs to be set according to the heat and power ratio of the cogeneration unit). The total coal feed command is set with a minimum value for the bypass steam supply system during shutdown to ensure the minimum stable combustion of the boiler. The boiler's water feed rate, primary air volume, and secondary air volume are automatically and rapidly adjusted in real time according to the coal feed rate.

[0105] S27: Close all valve groups of low-pressure steam supply and keep the hot reheat steam to high-pressure steam supply valve group in the state before the main steam supply system was in an abnormal state;

[0106] S28: When the high-pressure steam supply pressure is higher than the preset abnormal high-pressure threshold, the low-pressure bypass pressure regulating valve group is automatically opened using the bypass steam supply PID automatic control loop until the high-pressure steam supply pressure is lower than or equal to the preset normal high-pressure threshold.

[0107] For details, see Figure 6 As shown, after entering the bypass steam supply state, when the high-pressure steam supply pressure is higher than the preset abnormal high-pressure threshold, the interlock automatically opens the low-pressure bypass pressure regulating valve to the third preset opening degree for override control. When the high-pressure steam supply pressure is lower than or equal to the preset normal high-pressure threshold, the interlock automatically closes the low-pressure bypass pressure regulating valve. The low-pressure bypass water spray desuperheating regulating valve is automatically adjusted according to the steam temperature deviation after the valve throughout the entire process.

[0108] The third preset opening degree is obtained based on the third real-time broken line function 53(F3(x)) of the high-pressure steam supply pressure, which can better open and close the low-pressure bypass pressure regulating valve appropriately according to the high-pressure steam supply pressure regulation needs.

[0109] S29: Utilize the bypass steam supply PID automatic control loop to automatically control the high-pressure to low-pressure emergency connection steam supply regulating valve group, control the emergency low-pressure steam supply pressure to the fourth target value, and control the emergency low-pressure steam supply temperature to the fifth target value.

[0110] For details, see Figure 7 As shown, after entering the bypass steam supply state, the interlock opens the high-pressure to low-pressure emergency communication steam supply shut-off valve. Utilizing the time reserved by the third delay, the high-pressure to low-pressure emergency communication steam supply regulating valve is quickly opened to the fourth preset opening degree for override control. After the third delay, the automatic control loop of the high-pressure to low-pressure emergency communication steam supply regulating valve is automatically activated to control the low-pressure steam supply pressure. Upon activation of automatic control, the low-pressure steam supply pressure value before shutdown is memorized and assigned to the third PID controller corresponding to the high-pressure to low-pressure emergency communication steam supply regulating valve as the fourth target value. The third PID controller is then used to control the low-pressure steam supply pressure to the fourth target value.

[0111] For details, see Figure 7 As shown, the third delay is achieved by pulser 61. Pulser 61 sets the pulse time to the third delay duration, so that the high-pressure to low-pressure emergency communication steam supply regulating valve overshoots and forces the output to the fourth preset opening degree within the third delay time.

[0112] For details, see Figure 8 As shown, the fifth preset opening degree of the high-pressure to low-pressure emergency communication steam and water spray desuperheating regulating valve is quickly opened using the fourth delay time for override control. After the fourth delay, the automatic control loop of the high-pressure to low-pressure emergency communication steam and water spray desuperheating regulating valve is automatically activated to control the low-pressure steam supply temperature. At the moment of activation, the low-pressure steam supply temperature value before shutdown is memorized and assigned to the fourth PID controller corresponding to the high-pressure to low-pressure emergency communication steam and water spray desuperheating regulating valve as the fifth target value, so as to use the fourth PID controller to control the low-pressure steam supply temperature to the fifth target value.

[0113] For details, see Figure 8 As shown, the fourth delay is achieved by pulse generator 71. Pulse generator 71 sets the pulse time to the fourth delay duration, so that the high-pressure to low-pressure emergency communication steam supply regulating valve overshoots and forces the output to the fifth preset opening degree within the fourth delay time.

[0114] The fourth preset opening degree is obtained based on the fourth real-time broken line function 62 (F4(x)) of the low-pressure steam supply flow before the turbine or generator failure; the fifth preset opening degree is obtained based on the fifth real-time broken line function 72 (F5(x)) of the low-pressure steam supply flow before the turbine or generator failure; after automatic control, the operator can manually modify the fourth target value and / or the fifth target value according to the operating conditions.

[0115] As can be seen, see Figures 3 to 8 As shown, two independent PID controllers 31 are used to configure the two control modes of the high-pressure bypass pressure regulating valve, which can seamlessly switch to form the opening command of the high-pressure bypass pressure regulating valve. This enables the high-pressure bypass system to meet both the unit startup requirements and the need to continue to provide high-quality two-stage industrial steam supply safely and stably after a sudden turbine 2 or generator 3 failure trip during normal unit operation.

[0116] It should be noted that, Figures 3 to 8 Modules with the same symbol in the code have the same function; the only difference may be the specific parameters in different control loops. Figures 3 to 8 Not all icons are labeled, but those skilled in the art can determine the meaning and function of each icon, as well as the connection relationship and signal transmission direction, based on the arrows, labels, or existing text labels in the figure.

[0117] Understandably, before entering automatic control, each of the aforementioned valves sets a preset opening degree according to its corresponding relevant parameters and performs override control. This ensures a smoother transition when switching control modes and avoids large parameter fluctuations caused by switching PID automatic control loops.

[0118] It should be noted that steps S24 to S29 are asynchronous and can be performed in parallel. Each step can be automatically triggered and adjusted according to the triggering conditions, and there is no strict order.

[0119] Furthermore, this application also discloses a specific application scenario for a bypass steam supply system control method:

[0120] For example, in one configuration of a combined heat and power (CHP) unit, the high-pressure steam supply pressure is 4.4–5.0 MPa, the temperature is 440–450℃, and the maximum flow rate is 465 t / h; the low-pressure steam supply pressure is 1.3–1.8 MPa, the temperature is 320–330℃, and the maximum flow rate is 200 t / h. During normal operation, all valve groups on the high-pressure and low-pressure bypasses are closed. High-pressure steam is supplied from reheat steam through the high-pressure steam supply regulating valve to the high-pressure steam distribution station. Low-pressure steam is supplied from the third-stage extraction steam through the low-pressure steam supply regulating valve to the low-pressure steam distribution station. All high-pressure to low-pressure emergency connection steam supply valve groups are closed. The turbine high-pressure inlet steam regulating valve controls the high-pressure steam supply pressure, and the reheat to high-pressure steam supply regulating valve is manually operated to maximize its opening without throttling. The turbine intermediate-pressure inlet steam regulating valve controls the low-pressure steam supply pressure, and the third-stage extraction to low-pressure steam supply regulating valve is manually operated to maximize its opening without throttling. When a turbine trips or a generator disconnects from the grid, the boiler is required to continue operating by maintaining a two-stage heating steam supply through the bypass system and the high-pressure to low-pressure emergency communication steam supply valve group. This ensures effective control of the bypass steam supply system during shutdown, with the control strategy referring to... Figures 3 to 8 As shown, the automatic adjustment logic is optimized and configured in the DCS. The specific implementation steps are as follows:

[0121] Step 1: Optimize the setting and resetting of status signals for the bypass steam supply system during shutdown. See [link to specific logic] for details. Figure 3 ;

[0122] When the generating unit's power output is greater than 50MW and it is in normal operation for both high-pressure and low-pressure heating, if a turbine trips or the generator is disconnected, the shutdown-without-boiler bypass steam supply system signal will be set to "1". If the boiler BT delay is 1800 seconds, or the boiler MFT delay is 2400 seconds, or the main steam pressure before the turbine is lower than 3MPa for 60 seconds, or the turbine is started and the power output is greater than 40MW and the high-pressure bypass pressure regulating valve is closed for 30 seconds, the shutdown-without-boiler bypass steam supply system signal will be reset to "0". If the high-pressure bypass pressure regulating valve is in manual mode, the operator can also manually reset the shutdown-without-boiler bypass steam supply system status signal.

[0123] Step 2: Optimize the control strategy and automatic adjustment method of the high-pressure bypass pressure regulating valve. Use two PID controllers: one PID controller is used during unit ignition and startup, with its process value PV representing the main steam pressure before the turbine; the other PID controller is used during shutdown without stopping the boiler bypass steam supply system, with its process value PV representing the reheat steam pressure, i.e., the high-pressure steam supply pressure. See [link to specific logic] for details. Figure 4 ;

[0124] Specifically, if the high-pressure bypass pressure regulating valve is in manual mode, operators can manually reset the status signal of the bypass steam supply system during shutdown without shutting down the boiler. Then, the high-pressure bypass pressure regulating valve controls the main steam pressure before the turbine, assisting in restarting the turbine while providing bypass steam supply until the generator is reconnected to the grid and the load is increased. Alternatively, if the high-pressure bypass pressure regulating valve is in manual mode, operators can also manually set it to control the reheat steam pressure, i.e., the high-pressure steam supply mode. In other words, operators can flexibly choose between two operating modes for the high-pressure bypass pressure regulating valve. They can first release the valve from manual mode, then manually set it to control the reheat steam pressure for bypass steam supply mode to ensure stable industrial steam supply. Or, they can manually reset it to control the main steam pressure before the turbine for turbine and generator restart mode, while simultaneously ensuring stable industrial steam supply.

[0125] Step 3: After the signal for triggering the shutdown-but-not-stop bypass steam supply system is in the "1" state, quickly open the preset opening degree K1 of the high-pressure bypass pressure regulating valve. After 8 seconds, automatically engage the automatic mode of the high-pressure bypass pressure regulating valve to control the hot reheat steam pressure. Upon engaging automatic mode, the pre-shutdown hot reheat steam pressure value is memorized and assigned to the PID controller's setpoint SP. Operators can then manually modify the high-pressure steam supply pressure target value according to operating conditions. See [link to specific logic] for details. Figure 4 ;

[0126] In particular, the preset opening degree K1 is not a fixed constant, but a real-time F1(X) piecewise linear function 35 of the power generation before the turbine trips or the generator is disconnected. This can better adapt to the steam flow of the bypass steam supply system that does not stop the boiler during shutdown, and ensure that the steam pressure of the two-stage steam supply fluctuates as little as possible.

[0127] Step 4: After the signal for triggering the shutdown without stopping the boiler in the bypass steam supply system is in the "1" state, the high-pressure bypass spray water desuperheating shut-off valve is interlocked open, and the preset opening degree K2 of the high-pressure bypass spray water desuperheating regulating valve is opened quickly. After 5 seconds, the high-pressure bypass spray water desuperheating regulating valve automatically enters automatic mode to control the high-pressure bypass outlet steam temperature. At the moment of automatic activation, the actual value of the high-pressure bypass outlet steam temperature before shutdown is memorized and assigned to the setpoint SP of the PID controller. Then, the operator can manually modify the target value of the high-pressure steam supply temperature according to the operating conditions. For specific logic, please refer to [link to relevant documentation]. Figure 5 ;

[0128] In particular, the preset opening degree K2 is not a fixed constant, but a real-time F2(X) piecewise linear function 42 of the power generated before the turbine trips or the generator is disconnected. This can better control the high-pressure steam supply temperature of the bypass system that does not shut down the boiler during shutdown, ensuring that the fluctuation range of the high-pressure steam supply temperature is as small as possible. At the same time, it can better ensure that the high-pressure bypass system will not be shut down due to the excessively high steam temperature after the high-pressure bypass regulating valve after the instantaneous overdrive opening, thus avoiding interruption of the two-stage industrial steam supply.

[0129] Step 5: After the signal of the bypass steam supply system that triggers shutdown without stopping the boiler is in the "1" state, the boiler immediately and rapidly reduces the coal feed rate, water feed rate, primary air volume, and secondary air volume;

[0130] The total coal feed rate of the boiler is rapidly reduced at a rate of 195 t / h to 48% of the actual total coal feed rate before the turbine trips or the generator is disconnected (this set value needs to be set according to the heat and power ratio of the cogeneration unit). The general coal feed command is set with a minimum value of 42 t for the bypass steam supply system during shutdown to ensure the boiler's minimum stable combustion. The boiler's water feed rate, primary air volume, and secondary air volume are automatically and rapidly adjusted in real time according to the coal feed rate.

[0131] Step 6: After the bypass steam supply system signal for the shutdown is "1", close all valve groups from the three-stage extraction steam to the low-pressure steam supply. The hot reheat steam to the high-pressure steam supply valve group remains in the pre-shutdown state. The low-pressure bypass system valve group remains closed. When the high-pressure steam supply pressure is greater than 5.4 MPa, the low-pressure bypass pressure regulating valve will automatically open to the preset opening degree K3. After the high-pressure steam supply pressure drops below 5.3 MPa and returns to normal, the low-pressure bypass pressure regulating valve will automatically close. The low-pressure bypass water spray desuperheating regulating valve will automatically adjust according to the downstream steam temperature deviation throughout the process. For the specific logic of the low-pressure bypass pressure regulating valve, please refer to [link to relevant documentation]. Figure 6 .

[0132] In particular, the preset opening degree K3 is not a fixed constant, but a real-time F3(X) piecewise linear function 53 of the high-pressure steam supply pressure, which can better ensure that the high-pressure steam supply pressure does not exceed the pressure and avoid the reheat steam safety valve from operating.

[0133] Step 7: After the signal for the bypass steam supply system that triggers a shutdown without stopping the boiler is in the "1" state, the interlock opens the high-pressure to low-pressure emergency communication steam supply shut-off valve. Quickly open the preset opening degree K4 of the high-pressure to low-pressure emergency communication steam supply regulating valve. After 6 seconds, the valve automatically enters automatic mode to control the low-pressure steam supply pressure. Upon entering automatic mode, the valve memorizes the low-pressure steam supply pressure value before shutdown and assigns it to the setpoint SP of the PID controller of the high-pressure to low-pressure emergency communication steam supply regulating valve. Then, the operator can manually modify the target value of the low-pressure steam supply pressure according to the operating conditions. Quickly open the preset opening degree K5 of the high-pressure to low-pressure emergency communication steam supply water spray desuperheating regulating valve. After 5 seconds, the valve automatically enters automatic mode to control the low-pressure steam supply temperature. Upon entering automatic mode, the valve memorizes the low-pressure steam supply temperature value before shutdown and assigns it to the setpoint SP of the PID controller of the high-pressure to low-pressure emergency communication steam supply water spray desuperheating regulating valve. Then, the operator can manually modify the target value of the low-pressure steam supply temperature according to the operating conditions. See the specific logic below. Figure 7 and Figure 8 ;

[0134] Specifically, the preset opening degree K4 is not a fixed constant, but a real-time F4(X) broken line function 62 of the low-pressure steam supply flow before the turbine trips or the generator disconnects. This can better adapt to the low-pressure steam supply flow during shutdown without stopping the boiler, ensuring that the steam pressure of the low-pressure steam supply fluctuates as little as possible. Similarly, the preset opening degree K5 is not a fixed constant, but a real-time F5(X) broken line function 72 of the low-pressure steam supply flow before the turbine trips or the generator disconnects. This can better control the low-pressure steam supply temperature of the bypass system during shutdown without stopping the boiler, ensuring that the fluctuation range of the low-pressure steam supply temperature is as small as possible while maintaining high-quality heating under all operating conditions.

[0135] Step 8: Based on the boiler's heat storage capacity and the automatic adjustment characteristics of the bypass steam supply system, pre-set the estimated adjustment parameters and initial setpoints in the control strategy. As the bypass steam supply system is put into trial operation during shutdown, optimize and adjust to determine the optimal adjustment parameters and setpoints.

[0136] Under different heat load conditions, multiple adjustment tests were conducted on the bypass steam supply system during shutdown to obtain the optimal adjustment parameters and setpoints. The parameters and values ​​are shown in Table 1 (parameter table for F1(X) broken line function 35), Table 2 (parameter table for F2(X) broken line function 42), Table 3 (parameter table for F3(X) broken line function 53), Table 4 (parameter table for F4(X) broken line function 62), and Table 5 (parameter table for F5(X) broken line function 72).

[0137] Table 1

[0138]

[0139] Table 2

[0140]

[0141] Table 3

[0142]

[0143]

[0144] Table 4

[0145]

[0146] Table 5

[0147]

[0148] Accordingly, this application also discloses a steam supply system that uses the bypass steam supply system control method described above. See [link to relevant documentation]. Figure 9 As shown, the system includes: boiler 1, steam turbine 2, generator 3, three-stage extraction steam to low-pressure steam supply shut-off valve 4, three-stage extraction steam to low-pressure steam supply regulating valve 5, hot reheat steam to high-pressure steam supply shut-off valve 6, hot reheat steam to high-pressure steam supply regulating valve 7, high-pressure bypass pressure regulating valve 8, high-pressure bypass spray water desuperheating shut-off valve 9, high-pressure bypass spray water desuperheating regulating valve 10, high-pressure to low-pressure emergency communication steam supply shut-off valve 11, high-pressure to low-pressure emergency communication steam supply regulating valve 12, high-pressure to low-pressure emergency communication steam supply spray water desuperheating shut-off valve 13, high-pressure to low-pressure emergency communication steam supply spray water desuperheating regulating valve 14, low-pressure bypass pressure regulating valve 15, low-pressure bypass spray water desuperheating shut-off valve 16, low-pressure bypass spray water desuperheating regulating valve 17, steam turbine high-pressure inlet steam valve group 18, and steam turbine intermediate-pressure inlet steam valve group 19.

[0149] The bypass steam supply output of boiler 1 is connected to the input of the intermediate-pressure steam inlet valve group 19 of the steam turbine, the input of the high-pressure to low-pressure emergency connection steam supply shut-off valve 11, the input of the hot reheat steam to high-pressure steam supply shut-off valve 6, and the input of the low-pressure bypass pressure regulating valve 15. The low-pressure bypass spray water desuperheating shut-off valve 16 and the low-pressure bypass spray water desuperheating regulating valve 17 are connected in sequence. The output of the low-pressure bypass spray water desuperheating regulating valve 17 is used to spray water to cool the steam output from the low-pressure bypass pressure regulating valve 15. The hot reheat steam to high-pressure steam supply shut-off valve 6... The output end is connected to the input end of the hot reheat steam to high-pressure steam supply regulating valve 7. The output end of the hot reheat steam to high-pressure steam supply regulating valve 7 serves as the high-pressure steam supply end. The output end of the high-pressure to low-pressure emergency communication steam supply shut-off valve 11 is connected to the input end of the high-pressure to low-pressure emergency communication steam supply regulating valve 12. The output end of the high-pressure to low-pressure emergency communication steam supply regulating valve 12 serves as the emergency low-pressure steam supply end. The high-pressure to low-pressure emergency communication steam supply water spray desuperheating shut-off valve 13 and the high-pressure to low-pressure emergency communication steam supply water spray desuperheating regulating valve 14 are connected in sequence. The output of the steam supply water spray desuperheating regulating valve 14 is used to supply emergency low-pressure steam and water for cooling from the output of the high-pressure to low-pressure emergency communication steam supply regulating valve 12. The output of the turbine intermediate-pressure steam inlet valve group 19 is connected to the input of the three-stage extraction steam to low-pressure steam supply shut-off valve 4. The output of the three-stage extraction steam to low-pressure steam supply shut-off valve 4 is connected to the input of the three-stage extraction steam to low-pressure steam supply regulating valve 5. The output of the three-stage extraction steam to low-pressure steam supply regulating valve 5 serves as the low-pressure steam supply end. The main steam output of boiler 1 is connected to the input of the high-pressure bypass pressure regulating valve 8. The high-pressure inlet steam valve group 18 of the steam turbine is connected to the input end of the steam turbine 2. The output end of the high-pressure bypass pressure regulating valve 8 outputs the main steam after pressure reduction. The high-pressure bypass spray water desuperheating shut-off valve 9 and the high-pressure bypass spray water desuperheating regulating valve 10 are connected in sequence. The output end of the high-pressure bypass spray water desuperheating regulating valve 10 sprays water to cool the main steam output from the high-pressure bypass pressure regulating valve 8 and outputs cold reheat steam. Then, it is heated by the boiler reheater system 80 and outputs hot reheat steam.

[0150] in, Figure 9 It also includes a deaerator 81 and a steam recovery unit 82, and Figure 9 The specific connection relationships between the middle steam circuit and the equipment can be determined according to... Figure 9 The information is clearly identifiable, so I will not elaborate further here.

[0151] As can be seen, the steam supply system of this application uses the aforementioned bypass steam supply system control method, which adds an extra bypass steam supply PID automatic control loop for the bypass steam supply state to the steam supply system. By controlling the corresponding valve groups through this automatic control loop, it is possible to continue to provide two-level industrial steam supply under the special condition of shutdown without boiler interruption, and fully realize automatic control, reduce the impact of human factors and operation and maintenance costs, and improve safety and stability.

[0152] Finally, it should be noted that in this document, 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.

[0153] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0154] The technical content provided in this application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A control method for a bypass steam supply system, characterized in that, include: When the main steam supply system of a cogeneration unit is in an abnormal state, it will switch to bypass steam supply mode. The high-pressure bypass pressure regulating valve is automatically controlled by a separate bypass steam supply PID automatic control loop to control the hot reheat steam pressure to the first target value. The bypass steam supply PID automatic control loop is used to automatically control the high-pressure bypass water spray desuperheating regulating valve group to control the high-pressure bypass outlet steam temperature to the second target value. Reduce the boiler power to the third target value within a preset time; Close all valve groups from the three-stage extraction steam to the low-pressure steam supply, and keep the hot reheat steam to the high-pressure steam supply valve group in the state that was before the main steam supply system was in an abnormal state. When the high-pressure steam supply pressure exceeds the preset abnormal high-pressure threshold, the low-pressure bypass pressure regulating valve group is automatically opened using the bypass steam supply PID automatic control loop until the high-pressure steam supply pressure is lower than or equal to the preset normal high-pressure threshold. The bypass steam supply PID automatic control loop is used to automatically control the high-pressure to low-pressure emergency connection steam supply regulating valve group, control the emergency low-pressure steam supply pressure to the fourth target value, and control the emergency low-pressure steam supply temperature to the fifth target value. The process of automatically controlling the high-pressure bypass pressure regulating valve using a separate bypass steam supply PID automatic control loop to control the reheat steam pressure to the first target value includes: The high-pressure bypass pressure regulating valve is quickly opened to the first preset opening degree. After a first delay, the automatic control loop of the high-pressure bypass pressure regulating valve is automatically activated to control the hot reheat steam pressure. At the moment the automatic control is activated, the hot reheat steam pressure value before shutdown is memorized and assigned to the corresponding first PID controller as the first target value, so as to use the first PID controller to control the hot reheat steam pressure to the first target value. The first preset opening degree is obtained based on the first real-time piecewise linear function of the power generation before the turbine or generator failure. The process of automatically controlling the high-pressure to low-pressure emergency connection steam supply regulating valve group using the bypass steam supply PID automatic control loop, controlling the emergency low-pressure steam supply pressure to the fourth target value, and controlling the emergency low-pressure steam supply temperature to the fifth target value, includes: The interlock opens the high-pressure to low-pressure emergency communication steam supply shut-off valve, quickly opens the fourth preset opening degree of the high-pressure to low-pressure emergency communication steam supply regulating valve, and after the third delay, automatically engages the automatic control loop of the high-pressure to low-pressure emergency communication steam supply regulating valve to control the low-pressure steam supply pressure. At the moment of automatic engagement, the low-pressure steam supply pressure value before shutdown is memorized and assigned to the third PID controller corresponding to the high-pressure to low-pressure emergency communication steam supply regulating valve as the fourth target value, so as to use the third PID controller to control the low-pressure steam supply pressure to the fourth target value. The high-pressure to low-pressure emergency communication steam and water spray desuperheating regulating valve is opened to its fifth preset opening degree. After the fourth delay, the automatic control loop of the high-pressure to low-pressure emergency communication steam and water spray desuperheating regulating valve is automatically activated to control the low-pressure steam supply temperature. Upon activation, the low-pressure steam supply temperature value before shutdown is memorized and assigned to the fourth PID controller corresponding to the high-pressure to low-pressure emergency communication steam and water spray desuperheating regulating valve as the fifth target value. The fourth PID controller is then used to control the low-pressure steam supply temperature to the fifth target value. The fourth preset opening degree is obtained based on the fourth real-time broken line function of the low-pressure steam supply flow rate before the turbine or generator failure; the fifth preset opening degree is obtained based on the fifth real-time broken line function of the low-pressure steam supply flow rate before the turbine or generator failure. The process of automatically controlling the high-pressure bypass water spray desuperheating regulating valve group using the bypass steam supply PID automatic control loop to control the high-pressure bypass outlet steam temperature to the second target value includes: The high-pressure bypass spray desuperheating shut-off valve is interlocked and the high-pressure bypass spray desuperheating regulating valve is quickly opened to the second preset opening degree. After the second delay, the high-pressure bypass spray desuperheating regulating valve automatic control circuit is automatically engaged to control the high-pressure bypass outlet steam temperature. At the moment the automatic control is engaged, the actual value of the high-pressure bypass outlet steam temperature before shutdown is memorized and assigned to the second PID controller as the second target value, so as to use the second PID controller to control the high-pressure bypass outlet steam temperature to the second target value. The second preset opening degree is obtained from the second real-time piecewise linear function of the power generation before the turbine or generator failure; The process of automatically controlling the low-pressure bypass pressure regulating valve group using the bypass steam supply PID automatic control loop until the high-pressure steam supply pressure is lower than or equal to the preset normal high-pressure threshold includes: When the high-pressure steam supply pressure is higher than the preset abnormal high-pressure threshold, the interlock automatically opens the low-pressure bypass pressure regulating valve to the third preset opening degree. When the high-pressure steam supply pressure is lower than or equal to the preset normal high-pressure threshold, the interlock automatically closes the low-pressure bypass pressure regulating valve. The low-pressure bypass water spray desuperheating regulating valve is automatically adjusted according to the steam temperature deviation after the valve throughout the process. The third preset opening degree is obtained based on the third real-time broken line function of the high-pressure steam supply pressure.

2. The bypass steam supply system control method according to claim 1, characterized in that, The process of switching to bypass steam supply mode when the main steam supply system of a cogeneration unit is in an abnormal state includes: When the total power generation of the cogeneration unit exceeds the preset power generation threshold and / or the turbine of the cogeneration unit fails and / or the generator fails, the unit enters the bypass steam supply state.

3. The bypass steam supply system control method according to claim 1, characterized in that, The process of reducing the boiler power to the third target value within a preset time includes: Within a preset time period, reduce the coal feed rate and / or water feed rate and / or primary air volume and / or secondary air volume of the boiler until the boiler power reaches the third target value.

4. The bypass steam supply system control method according to any one of claims 1 to 3, characterized in that, Also includes: When the boiler trips after the fifth delay, or the boiler main fuel trips after the sixth delay, or the main steam pressure before the turbine is lower than the preset main steam setpoint and is delayed for the seventh delay, or the turbine is started and the high-pressure bypass pressure regulating valve is closed for the eighth delay, the status signal of the bypass steam supply system that stops the boiler during shutdown will be reset, and the main steam supply system will start working and supply steam.

5. The bypass steam supply system control method according to claim 4, characterized in that, Also includes: When the high-pressure bypass pressure regulating valve is in manual mode, it receives the bypass steam supply status control signal input by the user to control the steam supply system to enter or exit the bypass steam supply status.

6. A steam supply system, characterized in that, The bypass steam supply system control method according to any one of claims 1 to 4 includes: a boiler, a steam turbine, a generator, a three-stage extraction steam to low-pressure steam supply shut-off valve, a three-stage extraction steam to low-pressure steam supply regulating valve, a hot reheat steam to high-pressure steam supply shut-off valve, a hot reheat steam to high-pressure steam supply regulating valve, a high-pressure bypass pressure regulating valve, a high-pressure bypass water spray desuperheating shut-off valve, a high-pressure bypass water spray desuperheating regulating valve, a high-pressure to low-pressure emergency communication steam supply shut-off valve, a high-pressure to low-pressure emergency communication steam supply regulating valve, a high-pressure to low-pressure emergency communication steam supply water spray desuperheating shut-off valve, a high-pressure to low-pressure emergency communication steam supply water spray desuperheating regulating valve, a low-pressure bypass pressure regulating valve, a low-pressure bypass water spray desuperheating shut-off valve, a low-pressure bypass water spray desuperheating regulating valve, a steam turbine high-pressure inlet valve group, and a steam turbine intermediate-pressure inlet valve group. The boiler bypass steam supply output terminal is connected to the input terminal of the turbine intermediate-pressure inlet steam valve group, the input terminal of the high-pressure to low-pressure emergency connection steam supply shut-off valve, the input terminal of the hot reheat steam to high-pressure steam supply shut-off valve, and the input terminal of the low-pressure bypass pressure regulating valve. The low-pressure bypass water spray desuperheating shut-off valve and the low-pressure bypass water spray desuperheating regulating valve are connected in sequence. The output terminal of the low-pressure bypass water spray desuperheating regulating valve is used to spray water to cool the steam output from the low-pressure bypass pressure regulating valve. The output end of the high-pressure steam supply shut-off valve is connected to the input end of the hot reheat steam to high-pressure steam supply regulating valve, and the output end of the hot reheat steam to high-pressure steam supply regulating valve serves as the high-pressure steam supply end. The output end of the high-pressure to low-pressure emergency communication steam supply shut-off valve is connected to the input end of the high-pressure to low-pressure emergency communication steam supply regulating valve, and the output end of the high-pressure to low-pressure emergency communication steam supply regulating valve serves as the emergency low-pressure steam supply end. The high-pressure to low-pressure emergency communication steam supply water spray desuperheating shut-off valve and the high-pressure to low-pressure emergency communication steam supply water spray desuperheating regulating valve... The following components are connected sequentially: the output end of the high-pressure to low-pressure emergency communication steam-water spray desuperheating regulating valve is used to supply emergency low-pressure steam and water for cooling; the output end of the turbine intermediate-pressure steam inlet valve group is connected to the input end of the three-stage extraction steam to low-pressure steam supply shut-off valve; the output end of the three-stage extraction steam to low-pressure steam supply shut-off valve is connected to the input end of the three-stage extraction steam to low-pressure steam supply regulating valve; and the output end of the three-stage extraction steam to low-pressure steam supply regulating valve serves as the low-pressure steam supply end. The boiler... The main steam output terminal is connected to the input terminal of the high-pressure bypass pressure regulating valve and the input terminal of the turbine high-pressure inlet steam valve group, respectively. The output terminal of the turbine high-pressure inlet steam valve group is connected to the input terminal of the turbine. The output terminal of the high-pressure bypass pressure regulating valve outputs depressurized main steam. The high-pressure bypass spray desuperheating shut-off valve and the high-pressure bypass spray desuperheating regulating valve are connected in sequence. The output terminal of the high-pressure bypass spray desuperheating regulating valve sprays water to cool the depressurized main steam output from the output terminal of the high-pressure bypass pressure regulating valve.

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