Method for preventing and controlling reheater over-temperature and improving heating capacity under main steam heating condition

Abstract

The present application relates to the technical field of heat supply operation optimization of thermal power generating units, and discloses a reheater over-temperature prevention and control and heat supply capacity improvement method under a main steam heat supply condition.The present application supplements cooling working medium to the reheater through a high-pressure bypass, solves the problems of reheater flow shortage, wall temperature and outlet steam temperature over-limit under the main steam heat supply condition from the root, avoids the risks of pipeline oxidation, creep and pipe burst, accurately regulates and controls the reheater pressure through the low-pressure bypass, matches the high-pressure bypass steam injection amount, eliminates abnormal pressure fluctuation, ensures the safe operation of the steam turbine and the boiler, discards the traditional "heat supply limiting temperature control" mode, removes the constraint of reheater over-temperature on the heat supply load, and maximizes the heat supply potential of the unit.The multi-parameter interlocking protection logic realizes self-adaptive regulation and control under all conditions, has fast response speed and high precision, and is reliable in operation and strong in popularization.

Description

Technical Field

[0001] This invention relates to the field of thermal power generating unit heating operation optimization technology, and in particular to a method for reheater overheating prevention and heating capacity improvement under main steam heating conditions. Background Technology

[0002] Currently, thermal power generating units are the core equipment for centralized industrial heating, playing a crucial role in power system peak shaving and regional energy supply security. During normal pure condensing operation, the exhaust steam from the turbine's high-pressure cylinder can stably provide sufficient cooling medium to the boiler reheater, ensuring that the reheater wall temperature and outlet steam temperature remain within the design safety range, and the unit's operational stability is controllable.

[0003] Currently, when the unit enters the external steam supply heating mode, a large amount of high-temperature, high-pressure main steam is extracted for external heating, resulting in a sharp decrease in the steam flow entering the high-pressure cylinder of the turbine. Consequently, the exhaust steam flow from the high-pressure cylinder drops drastically, ultimately causing a severe shortage of cooling medium flow in the boiler reheater. Due to insufficient cooling medium, the metal wall temperature of the reheater's heating surface and the outlet reheat steam temperature are highly likely to exceed the equipment's design limits, leading to continuous overheating.

[0004] However, to avoid safety accidents such as pipe oxidation, material creep, and pipe rupture caused by reheater overheating, operators typically control reheater temperature by limiting the main steam extraction rate and reducing the unit's heating load. This operating method severely restricts the unit's heating potential and cannot meet the high-load demands of winter heating and continuous industrial heat use. Meanwhile, the industry currently lacks a targeted solution for coordinated control of reheater flow and pressure. The single method of desuperheating spray control suffers from temperature lag, low control accuracy, and is prone to steam parameter fluctuations. It cannot simultaneously address the multiple needs of reheater overheating prevention, safe unit operation, and improved heating capacity, becoming a core technological bottleneck restricting the efficient and safe heating of cogeneration units. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preventing and controlling reheater overheating and improving heating capacity under main steam heating conditions, which solves the problems of insufficient reheater flow, overheating and exceeding limits, limited heating capacity and poor operational safety of the unit under main steam heating conditions in the prior art.

[0006] To achieve the above objectives, this invention provides a method for preventing reheater overheating and improving heating capacity under main steam heating conditions, comprising the following steps: After the unit enters the main steam external supply heating mode, the reheater metal wall temperature, reheater outlet steam temperature, reheat steam header pressure, main steam heating extraction rate, and high-pressure cylinder exhaust pressure are collected in real time to determine whether the reheater cooling medium flow rate, temperature, and pressure parameters are within the safe range. When the reheater cooling medium flow rate is insufficient, or the wall temperature or outlet steam temperature rises abnormally, the high-pressure bypass is opened, and the main steam is injected into the reheater after being de-heated and de-pressurized to supplement the cooling medium flow rate and suppress the reheater overheating. By dynamically adjusting the reheater system pressure through the low-pressure bypass and matching the high-pressure bypass steam injection rate, the high exhaust pressure is stably controlled within the turbine safety threshold. Construct a multi-parameter interlock protection logic for high-pressure cylinder exhaust pressure and reheater temperature, and set up a graded early warning and protection action mechanism to avoid the risk of parameter exceeding limits; By dynamically adjusting the opening of high and low pressure bypasses based on unit load and heating demand, closed-loop adaptive control is achieved, thereby improving the unit's heating capacity.

[0007] The steam parameters after the high-pressure bypass de-temperature and pressure reduction are adapted to the rated operating parameters of the reheater, and the temperature and pressure match the safe operating range of the reheater, ensuring stable injection of cooling steam.

[0008] The low-pressure bypass adopts a PID precision adjustment mode, with pressure regulation accuracy controlled within ±0.05MPa, achieving stable control of high-pressure discharge without fluctuations.

[0009] The multi-parameter interlocking protection logic includes three levels of control logic: first-level early warning, second-level early warning, and emergency protection. It can automatically match the control strategy and protection action according to the degree of parameter abnormality.

[0010] The unit does not have reheater over-temperature or over-limit issues under main steam heating conditions, and the unit's heating capacity can be effectively increased by more than 15%.

[0011] This invention relates to a method for preventing reheater overheating and improving heating capacity under main steam heating conditions. Addressing the technical bottleneck of existing units where large-scale extraction of main steam for external heating leads to a sharp reduction in high-pressure cylinder exhaust flow, resulting in insufficient reheater cooling medium, excessive wall and outlet steam temperatures, and severely limiting unit heating capacity, this invention proposes an optimized scheme combining high- and low-pressure bypass coordinated control with multi-parameter interlocking protection. This invention injects de-heated and depressurized superheated steam into the reheater through the high-pressure bypass, rapidly replenishing the cooling medium flow and suppressing reheater overheating at its source. Simultaneously, it utilizes the low-pressure bypass to precisely control the high-pressure exhaust pressure and the high-pressure cylinder pressure ratio, ensuring turbine operational safety. Combined with temperature and pressure multi-parameter interlocking protection logic, it achieves adaptive safety control under all operating conditions. This invention completely solves the operational problem of "temperature control inevitably leads to heat limitation" in traditional units. Under the premise of ensuring the safe and stable operation of boiler and turbine equipment, it maximizes the heating potential of the unit, significantly improves the external heating capacity of cogeneration units, adapts to high-load heating conditions of various cogeneration units, and has extremely high application value. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0013] Figure 1 This is a flowchart of the method for preventing reheater overheating and improving heating capacity under main steam heating conditions provided by the present invention. Detailed Implementation

[0014] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0015] Please see Figure 1 This invention provides a method for preventing reheater overheating and improving heating capacity under main steam heating conditions, comprising the following steps: After the S1 unit enters the main steam external supply heating mode, it collects the reheater metal wall temperature, reheater outlet steam temperature, reheat steam header pressure, main steam heating extraction rate, and high-pressure cylinder exhaust pressure in real time to determine whether the reheater cooling medium flow rate, temperature, and pressure parameters are within the safe range. Specifically, after the unit is put into main steam external supply heating mode, the DCS system collects key parameters in real time, such as reheater tube wall temperature, reheater outlet steam temperature, reheat header pressure, high-pressure cylinder exhaust pressure, and main steam heating extraction rate. It then sets minimum safe cooling flow rate thresholds, temperature over-limit warning thresholds, and pressure safety thresholds for the reheater. When the high-pressure cylinder exhaust pressure is detected to be below the safety threshold and the reheater wall temperature is close to the design upper limit temperature, a coordinated control strategy is activated.

[0016] When the reheater cooling medium flow rate is insufficient, or the wall temperature or outlet steam temperature rises abnormally, the high-pressure bypass is opened. The main steam is injected into the reheater after being de-heated and de-pressurized to supplement the cooling medium flow rate and suppress the reheater overheating. The steam parameters after the high-pressure bypass de-temperature and pressure reduction are adapted to the rated operating parameters of the reheater, and the temperature and pressure match the safe operating range of the reheater, ensuring stable injection of cooling steam.

[0017] Specifically, the high-pressure bypass valve of the unit is gradually opened to draw out the main steam from the boiler. After being processed by the high-pressure bypass desuperheating and pressure reducing device, the low-temperature, low-pressure steam with appropriate parameters is sent into the reheater inlet pipeline to quickly replenish the reheater cooling medium flow. In this embodiment, after replenishing the flow through the high-pressure bypass, the reheater cooling flow is increased by more than 30%, which can quickly suppress the rising trend of reheater temperature and stabilize the tube wall temperature and outlet steam temperature within the design allowable range.

[0018] S3 dynamically adjusts the reheater system pressure through the low-pressure bypass and matches the high-pressure bypass steam injection amount to stably control the high exhaust pressure within the turbine safety threshold. Specifically, during the continuous steam injection process of the high-pressure bypass, the DCS system uses a PID algorithm to collect the high-pressure exhaust pressure in real time, dynamically adjusts the opening of the low-pressure bypass valve, and releases excess pressure in the system in real time. This counteracts the impact of the high-pressure cylinder exhaust pressure increase caused by the high-pressure bypass steam injection, and keeps the high-pressure cylinder exhaust pressure stably within the safe operating range of the turbine. This avoids problems such as high-pressure cylinder pressure ratio exceeding limits and large fluctuations in high-pressure cylinder exhaust pressure throughout the process.

[0019] S4 constructs a multi-parameter interlocking protection logic for high-pressure cylinder exhaust pressure and reheater temperature, and sets up a graded early warning and protection action mechanism to avoid the risk of parameter exceeding limits; The multi-parameter interlocking protection logic includes three levels of control logic: first-level early warning, second-level early warning, and emergency protection. It can automatically match the control strategy and protection action according to the degree of parameter abnormality.

[0020] Specifically, the DCS system incorporates multi-parameter interlocking protection logic for high-pressure cylinder exhaust pressure and temperature, and sets up a tiered early warning mechanism. When the reheater temperature slightly exceeds the limit, the system automatically increases the high-pressure bypass opening and increases the cooling flow; when the system pressure fluctuates slightly, it automatically fine-tunes the low-pressure bypass parameters; when an emergency condition occurs where temperature or pressure significantly exceeds limits, the system immediately locks the incremental heating steam extraction, stabilizes system operating parameters, and eliminates the risk of equipment damage.

[0021] S5 dynamically adjusts the opening of high and low pressure bypasses based on unit load and heating demand, achieving closed-loop adaptive control and improving the unit's heating capacity.

[0022] The unit has no reheater over-temperature or over-limit issues under main steam heating conditions, and the unit's heating capacity can be effectively increased by more than 15%.

[0023] Specifically, based on changes in external heat load demand and unit power generation load, the high and low pressure bypass ratio and valve opening are dynamically adjusted in real time to achieve adaptive closed-loop control of reheater temperature, flow rate, and high-pressure cylinder exhaust pressure. While ensuring zero over-temperature and zero over-limit conditions for the equipment, the main steam extraction rate is gradually increased to maximize the unit's heating capacity.

[0024] After adjustment using this method, the overheating problem of the reheater under the main steam heating condition of the unit was completely eliminated, with no high temperature over-limit alarms. The operating parameters of the turbine and boiler heating surfaces remained stable throughout the process, and the maximum heating capacity of the unit was increased by more than 15%, which can stably meet the heating demand during peak periods. Compared with the traditional load-limiting operation mode, the heating efficiency was greatly improved, and the safety of equipment operation was significantly optimized.

[0025] Compared with the prior art, the present invention has the following significant advantages: 1. Precisely solves the core problem of reheater overheating: This invention replenishes the reheater with cooling working fluid through a high-pressure bypass, fundamentally solving the problem of insufficient reheat steam flow under main steam heating conditions, significantly improving the reheater's cooling and heat exchange capacity, effectively suppressing the reheater's metal wall temperature and outlet steam temperature from exceeding limits, avoiding equipment failures such as high-temperature oxidation, creep deformation, and pipe rupture in the reheater pipes, and extending the equipment's service life.

[0026] 2. Balancing pressure safety and operational stability: The high-pressure cylinder exhaust pressure is precisely controlled in a closed loop through the low-pressure bypass, matching the high-pressure bypass steam injection flow rate, preventing abnormal fluctuations in the high-pressure cylinder pressure ratio, and stabilizing the high-pressure cylinder exhaust pressure within the safe operating range of the steam turbine, thus ensuring the operational safety of the steam turbine, boiler heating surfaces, and bypass system throughout the entire process.

[0027] 3. Significantly improve the unit's heating capacity: This invention abandons the traditional conservative operation mode of "limited load and temperature control". Through intelligent collaborative regulation, it removes the constraint of reheater overheating on the heating load, maximizes the main steam heating potential of the cogeneration unit, effectively improves the unit's external heating capacity, and can fully meet the peak heating demand of industrial high-load heat use and centralized heating in winter.

[0028] 4. High degree of automation and strong adaptability: The multi-parameter interlocking protection logic constructed by this invention can realize adaptive control under all working conditions without frequent manual intervention. It has fast control response speed and high accuracy, and can adapt to complex working conditions with different unit loads and different heating extraction volumes. It has high operational reliability and strong scalability.

[0029] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A method for preventing reheater overheating and improving heating capacity under main steam heating conditions, characterized in that, Includes the following steps: After the unit enters the main steam external supply heating mode, the reheater metal wall temperature, reheater outlet steam temperature, reheat steam header pressure, main steam heating extraction rate, and high-pressure cylinder exhaust pressure are collected in real time to determine whether the reheater cooling medium flow rate, temperature, and pressure parameters are within the safe range. When the reheater cooling medium flow rate is insufficient, or the wall temperature or outlet steam temperature rises abnormally, the high-pressure bypass is opened, and the main steam is injected into the reheater after being de-heated and de-pressurized to supplement the cooling medium flow rate and suppress the reheater overheating. By dynamically adjusting the reheater system pressure through the low-pressure bypass and matching the high-pressure bypass steam injection rate, the high exhaust pressure is stably controlled within the turbine safety threshold. Construct a multi-parameter interlock protection logic for high-pressure cylinder exhaust pressure and reheater temperature, and set up a graded early warning and protection action mechanism to avoid the risk of parameter exceeding limits; By dynamically adjusting the opening of high and low pressure bypasses based on unit load and heating demand, closed-loop adaptive control is achieved, thereby improving the unit's heating capacity.

2. The method for preventing reheater overheating and improving heating capacity under main steam heating conditions as described in claim 1, characterized in that, The steam parameters after the high-pressure bypass de-temperature and pressure reduction are adapted to the rated operating parameters of the reheater, and the temperature and pressure match the safe operating range of the reheater, ensuring stable injection of cooling steam.

3. The method for preventing reheater overheating and improving heating capacity under main steam heating conditions as described in claim 1, characterized in that, The low-pressure bypass adopts a PID precision regulation mode, with pressure regulation accuracy controlled within ±0.05MPa, achieving stable control of high-pressure discharge without fluctuations.

4. The method for preventing reheater overheating and improving heating capacity under main steam heating conditions as described in claim 1, characterized in that, The multi-parameter interlocking protection logic includes three levels of control logic: first-level early warning, second-level early warning, and emergency protection. It can automatically match the control strategy and protection action according to the degree of parameter abnormality.

5. The method for preventing reheater overheating and improving heating capacity under main steam heating conditions as described in claim 1, characterized in that, The unit has no reheater over-temperature or over-limit issues under main steam heating conditions, and the unit's heating capacity can be effectively increased by more than 15%.

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