An optimization method for accelerated warm-up of H159 steam turbine

Abstract

The present invention discloses an optimization method for accelerating the warm-up of an H159 steam turbine, comprising the following accelerated warm-up steps: Step S1: reducing initial parameters, increasing the reheat steam temperature, and increasing the steam intake; the initial parameters include the main steam pressure and the reheat steam pressure; Step S2: reducing final parameters and increasing the steam intake; Step S3: gradually opening the high-pressure and low-pressure extractions of the steam turbine, and discharging high-pressure and low-pressure drains directly to the turbine condenser via an emergency drain to increase the steam flow during warm-up; Step S4: reducing the turbine's intermediate pressure cylinder temperature limit in the X7D criterion from >261°C to >231°C. This optimization method significantly reduces startup time, improves safety, saves costs, and reduces pollutant emissions, resulting in excellent economic benefits.

Description

Technical Field

[0001] The present invention relates to a method for accelerating warm-up, and in particular to an optimization method for accelerating warm-up of an H159 steam turbine. Background Art

[0002] Thermal power plants currently play a crucial role in peak load regulation for the power grid, and frequent unit starts and stops are becoming increasingly commonplace. During a unit's cold start, turbine warm-up is performed to fully preheat the metal components of the turbine, a crucial step in ensuring the turbine can safely reach rated speed.

[0003] The H159 steam turbine is a C350-24.2 / 0.4 / 566 / 566 350MW supercritical intermediate reheat extraction condensing, single-shaft, single intermediate reheat, two-cylinder and two-exhaust, condensing (extraction capable) steam turbine manufactured by Shanghai Steam Turbine Works.

[0004] During a cold start, the turbine warms up to fully preheat the metal components of the turbine. This is a crucial step in ensuring the turbine can safely reach rated speed. However, the H159 turbine warm-up period accounts for half of the total time from boiler ignition to grid connection, resulting in significant coal and fuel consumption during the H159 turbine startup phase. Initially, the turbine run-up time for this turbine was approximately 13 hours, significantly longer than for other turbine models. Summary of the Invention

[0005] To solve the above problems, the purpose of the present invention is to provide an optimization method for accelerating the warm-up of an H159 type steam turbine, which improves the startup efficiency by optimizing each link in the startup process during the turbine start-up process.

[0006] The present invention provides an optimization method for accelerating warm-up of an H159 steam turbine, comprising the following steps:

[0007] Step S1: Lower the initial parameters, increase the reheat steam temperature, and increase the steam inlet volume; the initial parameters include the main steam pressure and the reheat steam pressure;

[0008] Step S2: reducing the final parameter and increasing the steam intake, where the final parameter refers to the vacuum pressure of the main engine of the steam turbine;

[0009] Step S3: gradually start the high-pressure extraction and low-pressure extraction of the steam turbine, and discharge the high-pressure and low-pressure drains directly to the condenser of the steam turbine through the emergency drain to increase the steam volume during warm-up;

[0010] Step S4: Lowering the restriction condition of the intermediate pressure cylinder temperature of the steam turbine in the X7D criterion from temperature>261°C to temperature>231°C.

[0011] A further improvement of the present invention is that in step S1, the main steam pressure is reduced from 8.4 MPa to 2.8-4 MPa, the reheat steam pressure is reduced from 0.828 MPa to 0.4 MPa, and the reheat steam temperature is increased to 400-420°C. When the turbine speed reaches 600 rpm, the reheat steam temperature is further increased to 430°C.

[0012] A further improvement of the present invention is that in step S2, after the steam turbine starts at 600 rpm, the vacuum pressure of the main engine of the steam turbine is reduced from -93 kPa to about -82 kPa, thereby increasing the steam inlet; the frequency of the circulating water pump of the steam turbine is reduced from 40 Hz to 35 Hz, thereby reducing the amount of cooling water for the condenser of the steam turbine.

[0013] A further improvement of the present invention is that it also includes an accelerated valve warming step; before the accelerated warming step, the accelerated valve warming step is performed first.

[0014] A further improvement of the present invention is that the steps of accelerating the valve warming are as follows:

[0015] Step S01: Adjust the reheat steam pressure and the intermediate pressure main steam valve temperature to enable the steam turbine to quickly pass the X6 criterion;

[0016] Step S02: When the X6 criterion is passed, the reheat steam pressure is restored to the start-up parameter.

[0017] A further improvement of the present invention is that in step S01, after the turbine main sequence control SGC is put into operation, the reheat steam pressure is quickly increased to 0.9 MPa, and the steam temperature in front of the medium-pressure main steam valve is increased from 400°C to 430°C by driving the steam flow through high pressure, so as to quickly pass the X6 criterion.

[0018] A further improvement of the present invention is that in step S02, the punching parameter is 0.4 MPa.

[0019] A further improvement of the present invention is that, in step S3, the high-pressure steam extraction and the low-pressure steam extraction of the steam turbine are completed through the fifth steam extraction interface of the steam turbine, and the opening degree of the fifth steam extraction interface is 8%-12%.

[0020] Beneficial effects of the present invention:

[0021] The optimization method presented in this paper was applied to the warm-up process of an H159 steam turbine, significantly reducing the warm-up time from the start of the turbine main sequence control (SGC) to the turbine reaching 3000 rpm, down from 13 hours to approximately 8 hours, saving 5 hours of startup time. The temperature difference between the high-pressure and intermediate-pressure cylinders can be controlled within ±20°C, significantly improving safety. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0023] The purpose of the present invention is to provide an optimization method for accelerating the warm-up of an H159 type steam turbine, which can be applied to the H159 type steam turbine to reduce the warm-up time of the steam turbine.

[0024] A steam turbine, also known as a steam turbine engine, is a rotary steam-powered device. High-temperature, high-pressure steam passes through a fixed nozzle, accelerating into an airflow before being ejected onto blades. This causes the rotor, equipped with rows of blades, to rotate, simultaneously generating work. Steam turbines are a key component of modern thermal power plants.

[0025] The C350-24.2 / 0.4 / 566 / 566 350MW supercritical, reheated, extraction-condensing, single-shaft, single-stage reheat, two-cylinder, two-exhaust, condensing (with extraction) steam turbine manufactured by Shanghai Steam Turbine Works. This turbine, designated H159 within the Shanghai Steam Turbine Works, utilizes a combined high- and low-pressure (HP) cylinder and dual-flow arrangement. The HP and HP sections utilize integrated inner and outer cylinders in a through- and counter-flow configuration. The LP section utilizes a split-flow structure with downward exhaust.

[0026] The new H159 steam turbine utilizes the leading AIBT integrated design platform, significantly improving flow efficiency. The high- and medium-pressure sections utilize an integrated inner casing design, resulting in a simple and clean structure that fundamentally eliminates steam leakage caused by loose retaining rings and inner casing sealing surfaces. The low-pressure section utilizes a braced inner casing structure to enhance the sealing effect and reduce internal leakage. The turbine's guaranteed heat rate under THA conditions is 7723.2 kJ / kW·h at a back pressure of 5.2 kPa, a 60 kJ / kW·h reduction compared to the previous-generation 159 model.

[0027] The H159 steam turbine utilizes a new sliding pin system. The dead points of the high- and intermediate-pressure cylinders are located at the front bearing seat, while the dead point of the rotor is located at the high- and intermediate-pressure combined radial thrust bearings within the front bearing seat. The low-pressure inner cylinder is directly supported on the foundation via the bearing seat. Thermal expansion of the high- and intermediate-pressure outer cylinders is directly transmitted to the low-pressure inner cylinder via push-pull rods (located in the center bearing seat). The low-pressure outer cylinder rests on the condenser, with the two rigidly welded together. While the condenser is supported on the foundation, it can also expand axially toward the generator. In summary, the absolute dead point of the turbine stator and the relative dead point of the rotor are both located at the front bearing seat. Both the rotor and stator components expand toward the generator via the combined radial thrust bearings. Thanks to the new sliding pin system, dynamic and static friction caused by differential expansion is virtually non-issue during actual turbine startup and shutdown.

[0028] The H159 steam turbine incorporates and applies numerous SAIC supercritical steam turbine technologies in its structure, and its operational control also utilizes the Digital Electro-Hydraulic Control (DEH) system used in SAIC supercritical units. The DEH control system's superiority lies primarily in its application of turbine thermal stress calculations throughout the entire turbine startup and shutdown control process, enabling automatic turbine startup. The H159 steam turbine uses a turbine thermal stress estimator (TSE) to monitor temperature differences among heavy components, such as the turbine rotor, inlet valve body, and cylinder block, to control turbine startup and load variation. A mismatch between steam temperature and metal temperature can lead to excessive thermal stress in metal components, which can affect component life. The turbine TSE prevents this from occurring. The DEH system has a high degree of automation, automatically completing the entire turbine startup process through the turbine master sequence control (SGC). The turbine runs through the following stages: run-up, speed increase to 600 rpm, low-speed warm-up, speed increase to 3000 rpm, high-speed warm-up, and grid connection with load. The X-criteria control the allowable temperature difference between the main steam temperature, main steam pressure, and reheat steam temperature and the main steam valve, regulating valve, high-pressure outer casing intermediate layer temperature, or the average temperature of the high- and intermediate-pressure rotors. At each of these stages, the main sequence control system uses the X-criteria to determine whether thermal stress meets requirements, deciding whether to proceed to the next step or continue waiting at the current step. These decisions are automatically made by the program, requiring no operator intervention. Failure to do so could lead to excessive stress.

[0029] The steam turbine includes the main steam valve, regulating valve, steam turbine, condenser, extraction unit, circulating water pump, water pump condensation, low-pressure heater, deaerator, feed water pump, high-pressure heater, oil supply system, regulating device and protective device.

[0030] Specific embodiment 1:

[0031] The invention discloses an optimization method for accelerating warm-up of an H159 steam turbine, comprising an accelerated warm-up step.

[0032] The steps to accelerate warm-up are as follows:

[0033] Step S1: Lower the initial parameters, increase the reheat steam temperature, and increase the steam inlet volume; the initial parameters include the main steam pressure and the reheat steam pressure;

[0034] Specifically: the main steam pressure is reduced from 8.4MPa to 2.8-4MPa, the reheat steam pressure is reduced from 0.828MPa to 0.4MPa, and the reheat steam temperature is increased to 400℃-420℃. When the turbine speed reaches 600rpm, the reheat steam temperature is further increased to 430℃.

[0035] Step S2: reducing the final parameter and increasing the steam intake, where the final parameter refers to the vacuum pressure of the main engine of the steam turbine;

[0036] Specifically: when the steam turbine starts at 600rpm, the vacuum pressure of the main engine of the steam turbine is reduced from -93kPa to about -82kPa to increase the steam inlet; the steam turbine only keeps one water ring vacuum pump running, and the other two water ring vacuum pumps are shut down, and some vacuum system valves to the atmosphere are opened to further reduce the vacuum.

[0037] The turbine's circulating water pump frequency was reduced from 40 Hz to 35 Hz, reducing the turbine's condenser cooling water volume by 3,000 tons. In the summer, when the vacuum drops, the condensate temperature rises, potentially causing the chemical fine treatment to trip. In this case, the condensate recirculation valve should be fully opened, allowing some condensate to be sprayed onto the condenser's steel pipes for further cooling, achieving a cooling effect.

[0038] Step S3: gradually start the high-pressure extraction and low-pressure extraction of the steam turbine, and discharge the high-pressure and low-pressure drains directly to the condenser of the steam turbine through the emergency drain to increase the steam volume during warm-up.

[0039] When the turbine reaches 600 rpm and warms up, gradually open the high-pressure and low-pressure extraction steam lines (except for the fourth extraction line to the deaerator). Drains from the high and low pressure heaters are discharged directly to the condenser via the emergency drain to increase the warm-up steam flow. The fifth-stage extraction steam connection is located between the inner and outer layers of the HP and IP cylinders, and the steam source is the IP cylinder exhaust. The extraction steam line should be opened slightly, specifically 8%-12%. Excessive opening can negatively increase the temperature difference between the HP and IP cylinders, threatening unit safety.

[0040] Step S4: Lowering the restriction condition of the intermediate pressure cylinder temperature of the steam turbine in the X7D criterion from temperature>261°C to temperature>231°C.

[0041] The brittle transition temperature (FATT) is a characteristic of metal materials whereby their plasticity decreases significantly and their brittleness increases significantly as temperature decreases. The brittle transition temperature is measured using impact testing. Above the brittle transition temperature, the metal is ductile and fractures primarily through ductile fracture. Below the brittle transition temperature, the material is brittle and fractures primarily through brittle fracture. The lower the brittle transition temperature, the higher the steel's resistance to cold brittleness. Therefore, during the turbine warm-up process, the intermediate pressure (IP) cylinder temperature is limited based on the brittle transition temperature (FATT) of the high-pressure and intermediate-pressure (HP) rotors. The H159 turbine's HP and IP rotors have higher brittle transition temperatures than conventional models. Therefore, the X7D standard's limit of an IP cylinder temperature >261°C has been lowered to 231°C, reducing the slow-speed warm-up period.

[0042] Example 2:

[0043] The process of this embodiment is the same as that of embodiment 1 in the accelerated warm-up step; the difference is that this embodiment is further improved in that there is an accelerated valve warming step before the accelerated warm-up step.

[0044] The steps to accelerate the warming of the valve are as follows:

[0045] Step S01: Adjust the reheat steam pressure and the intermediate pressure main steam valve temperature to enable the steam turbine to quickly pass the X6 criterion;

[0046] After the turbine's main sequence control (SGC) was activated, the reheat steam pressure was quickly raised to 0.9 MPa. High-pressure steam flow was used to increase the steam temperature before the intermediate-pressure main steam valve from 400°C to 430°C, allowing for rapid passage of the X6 criterion. This step reduced the time required to pass the X6 criterion from 5 hours to 2.5 hours.

[0047] Step S02: When the X6 criterion is passed, the reheat steam pressure is restored to the start-up parameter, which is 0.4 MPa.

[0048] This optimized method for accelerating the warm-up of an H159 steam turbine, without adding any additional equipment, shortens the warm-up process from the start of the turbine's main sequence control (SGC) to the time it takes to reach 3000 rpm from 13 hours to approximately 8 hours, saving 5 hours. The temperature difference between the high-pressure and intermediate-pressure cylinders can be controlled within ±20°C, significantly improving safety.

[0049] After the optimization method of the present invention is fully implemented in the unit, it can save 5 hours of unit startup time and 393,000 yuan in costs for a single unit startup. Among the three major pollutants, it can reduce sulfur dioxide emissions by 7.15 kg, nitrogen oxide emissions by 629.5 kg, and dust emissions by 3.55 kg, which has considerable economic and environmental benefits.

[0050] Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

Claims

1. An optimization method for accelerating warm-up of an H159 steam turbine, characterized in that: Including accelerated warm-up steps; the accelerated warm-up steps are as follows: Step S1: Lower the initial parameters, increase the reheat steam temperature, and increase the steam inlet volume; the initial parameters include the main steam pressure and the reheat steam pressure; Step S2: reducing the final parameter and increasing the steam intake, where the final parameter refers to the vacuum pressure of the main engine of the steam turbine; Step S3: gradually start the high-pressure extraction and low-pressure extraction of the steam turbine, and discharge the high-pressure and low-pressure drains directly to the condenser of the steam turbine through the emergency drain to increase the steam volume during warm-up; Step S4: Lowering the restriction condition of the intermediate pressure cylinder temperature of the steam turbine in the X7D criterion from temperature>261°C to temperature>231°C.

2. The optimization method for accelerating warm-up of an H159 steam turbine according to claim 1, characterized in that: In step S1, the main steam pressure is reduced from 8.4MPa to 2.8-4MPa, the reheat steam pressure is reduced from 0.828MPa to 0.4MPa, and the reheat steam temperature is increased to 400-420℃. When the turbine speed reaches 600rpm, the reheat steam temperature is further increased to 430℃.

3. The optimization method for accelerating warm-up of an H159 steam turbine according to claim 2, characterized in that: In step S2, after the steam turbine starts at 600 rpm, the vacuum pressure of the main engine of the steam turbine is reduced from -93 kPa to -82 kPa to increase the steam inlet; the frequency of the circulating water pump of the steam turbine is reduced from 40 Hz to 35 Hz to reduce the cooling water volume of the condenser of the steam turbine.

4. The optimization method for accelerating warm-up of an H159 steam turbine according to claim 1, characterized in that: It also includes an accelerated valve warming step; before the accelerated warming step, the accelerated valve warming step is performed first.

5. The optimization method for accelerating warm-up of an H159 steam turbine according to claim 4, characterized in that: The steps to accelerate the warming of the valve are as follows: Step S01: Adjust the reheat steam pressure and the intermediate pressure main steam valve temperature to enable the steam turbine to quickly pass the X6 criterion; Step S02: When the X6 criterion is passed, the reheat steam pressure is restored to the start-up parameter.

6. The optimization method for accelerating warm-up of an H159 steam turbine according to claim 5, characterized in that: In step S01, after the turbine main sequence control SGC is put into operation, the reheat steam pressure is quickly increased to 0.9 MPa, and the steam temperature in front of the medium-pressure main steam valve is increased from 400°C to 430°C by driving the steam flow through high pressure, so as to quickly pass the X6 criterion.

7. The optimization method for accelerating warm-up of an H159 steam turbine according to claim 5, characterized in that: In step S02, the punching parameter is 0.4 MPa.

8. The optimization method for accelerating warm-up of an H159 steam turbine according to any one of claims 1 to 5, characterized in that: In step S3, the high-pressure steam extraction and the low-pressure steam extraction of the steam turbine are completed through the fifth steam extraction interface of the steam turbine, and the opening degree of the fifth steam extraction interface is 8%-12%.