A method and system for starting and purging a v94.2 gas turbine

Abstract

The application discloses a V94.2 type gas turbine starting blow-off optimization method and system, and the system comprises a combustible gas detection preprocessing cabinet arranged at an exhaust diffusion section and a chimney inlet, wherein a pneumatic pump, a gas analysis instrument, a cooling device and the like are integrated in the cabinet, sampling and analysis are controlled through a TCS system, and combustible gas concentration (LEL) is monitored in real time. The method comprises the following steps: dynamically determining a blow-off time, establishing a blow-off time model based on multiple variables such as load, shutdown time length, flame signal disappearance event and combustible gas concentration threshold, and optimizing the blow-off time length by comparing the actual measured concentration with a safety threshold (25% LEL). Through hardware modification and logic optimization, the application reduces energy waste caused by fixed blow-off time, improves the starting efficiency of the gas turbine, and reduces the risk of deflagration.

Description

TECHNICAL FIELD

[0001] The application relates to a V94.2 type gas turbine starting blow-down optimization method and system and belongs to the technical field of gas turbines. BACKGROUND

[0002] As a key equipment in the modern energy field, a gas turbine is widely applied to power generation and industrial driving. In the starting process of the gas turbine, in order to ensure safety and avoid potential dangers caused by combustible gas accumulation, a blow-down operation needs to be performed.

[0003] After the gas turbine is tripped, abnormally stopped or the natural gas valve is not tightly closed after being stopped, a small amount of unburned combustible gas is left in the gas turbine or the waste heat boiler, at this time, if the gas turbine is ignited and started, there is a risk of deflagration, which causes damage to the gas turbine and the waste heat boiler equipment.

[0004] Generally, each gas turbine manufacturer (OEM) designs a starting blow-down control, and the main purpose is to purge the combustible gas left in the gas turbine hot channel and the waste heat boiler. Its main function is to first rotate the gas turbine to 700-800 rpm (lower than the first critical speed) through SFC before ignition and rotation, then the SFC controls the gas turbine at a constant speed or fluctuating speed, and lasts for 10-15 minutes, a large amount of air is used to discharge the possible residual natural gas outside the chimney, then the ignition sequence control is permitted, and then it is lowered to the ignition speed to start the ignition program.

[0005] However, the above-mentioned method still has the following defects: first, the blow-down process often needs a long time, which prolongs the starting cycle of the gas turbine; in addition, frequent starting and blow-down process increases the thermal stress of the downstream equipment such as the waste heat boiler, not only shortens the service life of the equipment, but also increases the maintenance cost; secondly, the long blow-down process causes the steam pipe wall temperature of the waste heat boiler to rapidly drop, thereby affecting its heat preservation and pressure maintaining capacity, resulting in low thermal efficiency and energy waste.

[0006] Therefore, on the basis of comprehensive analysis of the domestic and foreign OEM starting blow-down optimization, a gas turbine starting blow-down program optimization scheme suitable for the current situation of a certain type of Siemens gas turbine equipment is developed, which adopts a dynamic blow-down time. SUMMARY

[0007] In view of the problems in the prior art, the application provides a V94.2 type gas turbine starting blow-down optimization method and system, so as to reduce the SFC power consumption and auxiliary machine power consumption, reduce the warm-up time of the waste heat boiler, reduce the blow-down time, and the unit is free of blow-down in normal start-stop working conditions; dynamic starting time is adopted in abnormal working conditions, so that the economic efficiency and rapid starting of the gas turbine are achieved.

[0008] In order to achieve the above object, the technical scheme adopted by the present application is: a V94.2 type gas turbine starting blow-off optimization system, characterized in that it comprises a combustible gas detection preprocessing cabinet arranged at a gas sampling hole reserved in an exhaust diffusion section and a chimney inlet gas sampling hole; The combustible gas detection preprocessing cabinet is provided with a precision filter, a gas source processor, a sampling flow meter, a pressure reducing valve, a pneumatic pump, a water trap, a gas analysis instrument, a solenoid valve, an air inlet cooling device and a joint. One side of the combustible gas detection preprocessing cabinet is connected with a gas turbine TCS system.

[0009] Further, the combustible gas detection preprocessing cabinet is powered by 220VAC on the TCS system side, and the pneumatic pump is used to complete the air pumping action, and the solenoid valve in the collection box is controlled by the TCS system to control the sampling action, and then the combustible gas concentration after analysis is transmitted to the gas turbine TCS system in the form of 4-20mA.

[0010] Further, the pneumatic pump is used to complete the air pumping action and realize the function of compressed air.

[0011] Further, it further comprises a flight recorder for measuring the time from flame disappearance to fuel shut-off valve ESV closing.

[0012] A V94.2 type gas turbine starting blow-off optimization method, comprising the following methods, Step one: add two sets of combustible gas detection preprocessing cabinets at the gas sampling holes reserved in the exhaust diffusion section and the chimney inlet gas sampling hole; use the gas detection reserved hole to extract a section of sample gas to the combustible gas detection preprocessing cabinet; when sampling is needed, the TCS remotely opens the electric valve and the air pumping pump to extract the sample gas for analysis, and if the sample gas is high-temperature gas, it can also be cooled and processed, after the analysis is completed, the valve is closed to prevent gas leakage, and at the same time, the 4-20mA signal and the on-off signal of the natural gas concentration are sent to the TCS system for logical operation; Step two: study the minimum jump load that needs to be blown off and establish a function of load and residual natural gas concentration, use the flight recorder to measure the time from flame disappearance to fuel shut-off valve ESV closing, then check the total amount of natural gas entering the gas turbine at each load section, multiply the total amount of natural gas by the time when the ESV is closed, obtain the total volume of natural gas, and then divide by the volume of the furnace to obtain the calculated concentration of natural gas at each load section; Step three: the combustible gas concentration at the exhaust diffusion section or the exhaust gas heat recovery boiler outlet is greater than 25% LEL, i.e. the gas concentration reaches the deflagration limit, a function of natural gas concentration and blow-off time is established, the SFC blow-off sequence control is started, and the time required to reduce the natural gas concentration in the exhaust diffusion section and the chimney inlet to the safe range is checked; Step four: design a manual blow button, and the operator blows as needed.

[0013] When there is no flame signal for 15 seconds after the ESV is turned on, the ignition fails, and a large amount of natural gas is not burned, so the blow time is determined. First, the power supply of the burner ignition electrode is turned off, then the gas turbine sequential control is started, the ignition failure is simulated, the natural gas concentration is checked, and then the SFC blow sequential control is started. The required blow time to reduce the concentration to the safe range can be timed.

[0014] When the unit is stopped for more than 192h, the unit needs to be blown, to prevent natural gas leakage due to loose valves, which may cause local accumulation of natural gas, so the blow time is determined. The natural gas concentration in the exhaust diffusion section of the unit stopped for more than 192h is measured, then the SFC blow sequential control is started, and the required blow time to reduce the concentration to the safe range can be timed.

[0015] When the unit is stopped for more than 192h, the unit needs to be blown, to prevent natural gas leakage due to loose valves, which may cause local accumulation of natural gas, so the blow time is determined. The natural gas concentration in the exhaust diffusion section of the unit stopped for more than 192h is measured, then the SFC blow sequential control is started, and the required blow time to reduce the concentration to the safe range can be timed.

[0016] The beneficial effects of the present application are: the present application proposes an optimized blow time method by adding the hardware and control logic of the combustible gas collection box and the logic of the dynamic blow time, reduces the gas turbine start-up time, reduces the plant power consumption rate, reduces the boiler temperature drop, and completes the steam turbine pre-starting and grid connection in advance. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The dynamic blow time logic of the present application is shown in the figure; Figure 2 The combustible gas collection box installation schematic of the present application is shown in the figure. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present application more clear and obvious, the present application is further described in detail below by means of the drawings and examples. However, it should be understood that the specific examples described herein are only used to explain the present application, and are not intended to limit the scope of the present application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs, and the terms used in the specification of the present application are only for the purpose of describing specific examples, and are not intended to limit the present application.

[0020] As Figure 1 , Figure 2As shown, a V94.2 type gas turbine starting blow-down optimization system comprises a combustible gas detection preprocessing cabinet arranged at a gas sampling hole reserved in an exhaust diffusion section and a chimney inlet gas sampling hole; A precision filter, a gas source processor, a sampling flow meter, a pressure reducing valve, a pneumatic pump, a water trap, a gas analysis instrument, a solenoid valve, an air inlet cooling device, and a joint are arranged in the combustible gas detection preprocessing cabinet. One side of the combustible gas detection preprocessing cabinet is connected with a gas turbine TCS system.

[0021] In this embodiment, the combustible gas detection preprocessing cabinet is powered by 220VAC on the TCS system side, and the pneumatic pump is used to complete the air pumping action. The solenoid valve in the TCS system control collection box is used to control the sampling action, and then the combustible gas concentration after analysis is transmitted to the gas turbine TCS system in the form of 4-20 mA.

[0022] In this embodiment, the pneumatic pump is used to complete the air pumping action and realize the function of compressed air.

[0023] In this embodiment, a flight recorder is further included, which is used to measure the time from flame disappearance to the closing of the fuel shut-off valve ESV.

[0024] A V94.2 type gas turbine starting blow-down optimization method comprises the following steps, Step one: two sets of combustible gas detection preprocessing cabinets are added and arranged at the gas sampling holes reserved in the exhaust diffusion section and the chimney inlet gas sampling hole. A section of sample gas is extracted to the combustible gas detection preprocessing cabinet through the gas detection reserved hole. When sampling is needed, the TCS remotely opens the electric valve and the air pumping pump to extract the sample gas for analysis. If the sample gas is high-temperature gas, it can also be cooled and processed. After the analysis is completed, the valve is closed to prevent gas leakage, and at the same time, the 4-20 mA signal and the on-off signal of the natural gas concentration are sent to the TCS system for logical operation; Step two: the minimum trip load for blow-down is studied, and a function of the load and residual natural gas concentration is established. The flight recorder is used to measure the time from flame disappearance to the closing of the fuel shut-off valve ESV, and then the total amount of natural gas entering the gas turbine at each load section is checked. The total amount of natural gas is multiplied by the closing time of the ESV, the total volume of natural gas is obtained, and then the volume of the furnace is divided to obtain the calculated concentration of natural gas at each load section. Step three: when the combustible gas concentration at the exhaust diffusion section or the waste heat boiler outlet is greater than 25% LEL, i.e., the gas concentration reaches the deflagration limit, a function of the natural gas concentration and the blow-down time is established, the SFC blow-down sequence control is started, and the time required to reduce the natural gas concentration in the exhaust diffusion section and the chimney inlet to the safe range is checked. Step four: a manual blow-down button is designed, and the operator performs blow-down as needed.

[0025] In this embodiment, when there is no flame signal for 15 seconds after the ESV is turned on, the ignition fails, and a large amount of natural gas is not burned, and the purging time is determined. First, the power supply of the igniter electrode of the combustor is turned off, then the engine sequential control is started, the ignition failure is simulated, the natural gas concentration is checked, and then the SFC purging sequential control is started. The purging time required to reduce the concentration to a safe range is timed.

[0026] In this embodiment, when the unit is shut down for more than 192 hours, the unit needs to be purged to prevent natural gas leakage due to loose natural gas valves, which causes local accumulation of natural gas, and the purging time is determined. The natural gas concentration in the exhaust diffusion section of the unit that has been shut down for more than 192 hours is measured, and then the SFC purging sequential control is started. The purging time required to reduce the concentration to a safe range is timed.

[0027] In this embodiment, due to the Flame off caused by the trip, the combustion process is extinguished, and a large amount of natural gas is not burned. The natural gas concentration is checked, and then the SFC purging sequential control is started. The purging time required to reduce the concentration to a safe range is timed.

[0028] The core of the present invention is to dynamically adjust the purging time by real-time monitoring of the combustible gas concentration and analyzing the unit trip / shutdown conditions, and intelligently calculating the optimal purging time to avoid the inefficiency of fixed purging time. The working principle can be divided into the following key parts: 1. On-line monitoring of combustible gas concentration (1) Gas sampling and pretreatment Sampling point arrangement: Install a combustible gas detection and pretreatment cabinet at the exhaust diffusion section of the gas turbine and the inlet of the waste heat boiler chimney to extract sample gas and analyze the lower explosive limit (LEL).

[0029] Pretreatment process: High-temperature gas cooling: The exhaust gas temperature of the gas turbine is high, and it needs to be cooled to a safe temperature below by an air inlet cooling device.

[0030] Dust and moisture removal: Remove particulate matter through a precision filter, and separate water through a water trap to ensure dry and clean gas.

[0031] Flow control: Adjust the air intake through a sampling flowmeter and a pressure reducing valve to maintain constant flow.

[0032] Gas analysis: Use infrared or catalytic combustion type gas sensors to detect the concentration of combustible gases such as methane (CH4), and output a 4-20 mA signal to the TCS system.

[0033] (2) Concentration threshold triggers purging When the concentration of combustible gas is detected to be >25% LEL (25% of the lower explosive limit), the TCS system automatically triggers the purging program.

[0034] The concentration is continuously monitored during the purging process until <5% LEL is allowed to ignite, ensuring safety.

[0035] 2. Dynamic purging time calculation model The purging time is no longer fixed, but is dynamically calculated based on the unit load, shutdown time, flame state, etc. The main logic is as follows: (1) Purging time based on load shedding When the gas turbine is tripped, the amount of residual natural gas is proportional to the load before tripping.

[0036] The flight recorder records the time difference (Δt) between the flame disappearing and the fuel shut-off valve (ESV) closing, and calculates the residual amount based on the load shedding.

[0037] For example: High load shedding (>50MW): large natural gas inlet flow, more residual gas, purging time needs to be extended (e.g. 10 minutes).

[0038] Low load shedding (<20MW): less residual gas, purging time can be shortened (e.g. 6 minutes).

[0039] (2) Purging time based on shutdown time After a long shutdown, air or trace amounts of natural gas may accumulate inside the gas turbine, requiring conservative purging: Shutdown >192 hours: forced purging for 10 minutes (to prevent accumulation of small valve leaks).

[0040] Shutdown <24 hours: only 5 minutes of purging is required (assuming natural gas has naturally diffused).

[0041] (3) Purging triggered by no flame signal When there is no flame signal within 15 seconds after the ESV valve is opened, it is determined that the ignition has failed, and the purging program is automatically started (default 8 minutes).

[0042] (4) Comprehensive decision logic The TCS system selects the longest purging time from the above conditions as the final value, ensuring safety coverage for the most stringent conditions.

[0043] The core innovation of the invention is: Hardware: Add a high-precision combustible gas monitoring system to solve the problem of "blind blowing" in traditional gas turbines.

[0044] Software: Through a dynamic calculation model, the purging time is matched with the real risk, taking into account safety and economy.

[0045] Engineering value: suitable for Siemens V94.2, Mitsubishi M701F and other models, especially for the frequent start-stop scene benefit of peak shaving power plant.

[0046] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A V94.2 gas turbine start-up and cleaning optimization system, characterized in that, This includes combustible gas detection and pretreatment cabinets installed at the gas sampling holes reserved in the exhaust diffusion section and at the gas sampling holes at the chimney inlet; The combustible gas detection pretreatment cabinet is equipped with a precision filter, a gas source processor, a sampling flow meter, a pressure reducing valve, a pneumatic pump, a water blocker, a gas analysis instrument, a solenoid valve, an air intake cooling device, and connectors. The combustible gas detection and pretreatment cabinet is connected to the gas turbine TCS system on one side.

2. The V94.2 gas turbine start-up and cleaning optimization system according to claim 1, characterized in that, The combustible gas detection and pretreatment cabinet is powered by 220VAC from the TCS system side. A pneumatic pump is used to complete the gas extraction action. At the same time, the TCS system controls the solenoid valve in the acquisition box to control the sampling action. Then, the analyzed combustible gas concentration is transmitted to the gas turbine TCS system in the form of 4~20mA.

3. The V94.2 gas turbine start-up and cleaning optimization system according to claim 1, characterized in that, The pneumatic pump is used to perform the pumping action and compress the air.

4. The V94.2 gas turbine start-up and cleaning optimization system according to claim 1, characterized in that, It also includes a flight recorder, which measures the time from when the flame disappears to when the fuel shut-off valve (ESV) closes.

5. An optimized method for starting and cleaning a V94.2 gas turbine, characterized in that, Including the following methods, Step 1: Add two new combustible gas detection pretreatment cabinets and place them at the gas sampling holes reserved in the exhaust diffusion section and the gas sampling holes at the chimney inlet. Using the reserved gas detection holes, extract a sample gas to the combustible gas detection pretreatment cabinet. When sampling is required, the TCS remotely opens the electric valve and the gas pump to extract the sample gas for analysis. If the sample gas is a high-temperature gas, it can be cooled. After the analysis is completed, close the valve to prevent gas leakage. At the same time, the 4~20mA signal of natural gas concentration and the switch signal will be sent to the TCS system for logic calculation. Step 2: Study the minimum blowdown load that needs to be purged and establish a function of load and residual natural gas concentration. Use the flight recorder to measure the time from the flame disappearing to the fuel shut-off valve (ESV) closing. Then check the total amount of natural gas entering the gas turbine for each load segment. Multiply the total amount of natural gas by the ESV closing time to get the total volume of natural gas. Then divide by the volume of the furnace to get the calculated concentration of natural gas for each load segment. Step 3: If the combustible gas concentration at the exhaust diffusion section or waste heat boiler outlet is >25% LEL, that is, the gas concentration has reached the deflagration limit, establish a function of natural gas concentration and purging time, start SFC purging sequential control, check how much time is required, and reduce the natural gas concentration at the exhaust diffusion section and chimney inlet to a safe range. Step 4: Design a manual cleaning button so that operators can clean the system as needed.

6. The optimized start-up and cleaning method for a V94.2 gas turbine according to claim 5, characterized in that, If there is no flame signal 15 seconds after the ESV is turned on, ignition fails and a large amount of natural gas remains unburned. Determine the purging time. First, disconnect the power supply to the burner ignition electrode, then start the gas turbine using sequential control to simulate ignition failure and check the natural gas concentration. Then, start the SFC purging sequential control and time the purging time required to reduce the concentration to a safe range.

7. The optimized start-up and cleaning method for a V94.2 gas turbine according to claim 5, characterized in that, When a unit is shut down for more than 192 hours, it needs to be purged to prevent natural gas leaks caused by leaking valves, which could lead to localized natural gas accumulation. The purging time is determined by measuring the natural gas concentration in the exhaust diffusion section of units shut down for more than 192 hours, then activating the SFC purging sequence control and timing the process to reduce the concentration to a safe range.

8. The optimized start-up and cleaning method for a V94.2 gas turbine according to claim 5, characterized in that, The generator tripped due to a flameout, resulting in a large amount of unburned natural gas. The natural gas concentration was checked, and then the SFC purge sequential control was activated. The timer showed the purging time required to reduce the concentration to a safe range.

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