A wet nitrogen-filling maintenance method for quick start of a waste heat boiler of a combustion engine
By using the wet nitrogen purging maintenance method, the problems of long start-up and shutdown times and corrosion in the waste heat boiler of the gas turbine unit have been solved, achieving rapid start-up and shutdown and water conservation, inhibiting dissolved oxygen corrosion, and extending the boiler's lifespan.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG ZHENENG TECHN RES INST CO LTD
- Filing Date
- 2022-12-02
- Publication Date
- 2026-05-15
AI Technical Summary
Existing gas turbine waste heat boilers have long start-up and shutdown times, corrosion problems, and cannot meet the requirements for rapid start-up and shutdown, resulting in serious water waste.
The wet nitrogen purging maintenance method involves purging nitrogen into the boiler without draining water to isolate it from the outside air and maintain the internal pressure of the boiler. The pH value is increased by using a deaerator and ammonia addition, the dissolved oxygen in the feedwater is monitored, and nitrogen is obtained by using a nitrogen generator to maintain the boiler pressure.
It enables rapid start-up and shutdown of gas turbine units, saves water resources, inhibits dissolved oxygen corrosion, reduces chemical cleaning costs, and extends boiler life.
Smart Images
Figure CN115773492B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of energy application technology and environmental protection and energy conservation, and more specifically, it relates to a wet nitrogen charging maintenance method for rapid start-up of a gas turbine waste heat boiler. Background Technology
[0002] The rapid development of the global economy and society has increased people's demand for energy. With the upgrading and transformation of industrial structures, the electricity consumption structure has undergone significant changes. Correspondingly, more and more large-capacity generating units are participating in peak-shaving operations to meet the real-time requirements of different electricity demands. Peak-shaving operations require units to have fast start-up and shutdown speeds and flexible responses. Gas turbine units have the advantages of high efficiency, cleanliness, and environmental friendliness, and their installed capacity is increasing year by year. However, due to factors such as power grid planning, gas supply, and gas prices, most gas turbine units in my country operate on a daily start-up and shutdown model, which places higher demands on the rapid start-up and shutdown of these units. Currently, gas turbine units generally suffer from long start-up and shutdown times and equipment corrosion, among other prominent problems. This not only restricts the peak-shaving capacity of the units and is detrimental to the stable operation of the power grid, but also, due to the slow start-up speed, the boilers consume more fuel, which greatly increases the power generation costs for enterprises. Therefore, against the backdrop of increasing power grid peak-shaving demand and energy shortages, improving the operating speed of generating units during start-up, shutdown, and load changes, and achieving safe and economical operation of the units, has become increasingly urgent and important for power plants.
[0003] As one of the three main components of a gas-fired combined cycle power plant, the waste heat boiler (HRSG) sits between the gas turbine and the steam turbine, playing a crucial role in the overall system optimization and matching of major subsystems. Its structure, performance, and parameters significantly impact the performance of other equipment and the entire system. Therefore, in-depth research on waste heat boilers is essential for comprehensively improving the technical level of gas-fired combined cycle power plants and achieving optimized system design.
[0004] The current main process for starting and stopping gas turbine units involves draining the boiler water when the temperature drops to 100-120°C. After draining, the residual heat in the boiler is used to dry the inner surface. While this method is simple, it requires refilling with water when restarting, wasting water resources and failing to achieve rapid start-up and shutdown. Furthermore, air entering during draining can easily lead to dissolved oxygen corrosion. Therefore, researching start-up, shutdown, and maintenance methods suitable for waste heat boilers in gas turbine units to achieve rapid start-up and shutdown and suppress dissolved oxygen corrosion is of great significance. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a wet nitrogen charging maintenance method for rapid start-up of gas turbine waste heat boilers.
[0006] Currently, the start-up and shutdown process for waste heat boilers in gas turbine power plants mainly involves draining water after the boiler temperature drops. This creates negative pressure inside the boiler, inevitably allowing outside air to leak in and corrode the boiler's inner walls. When restarting, the inner walls require chemical cleaning followed by rinsing with large amounts of water, increasing costs and wasting water resources. In contrast, the method provided by this invention involves filling the boiler with nitrogen without draining water, maintaining internal pressure and fundamentally preventing outside air from entering. This saves water resources and inhibits corrosion of the inner walls. Furthermore, for rapid start-up, simply adjusting the pressure without nitrogen filling is sufficient to meet the pre-startup requirements.
[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows:
[0008] Step 1: Close all isolation valves from the high-pressure system to the boiler expansion tank;
[0009] Step 2: Replenish the deoxygenated water tank with water and keep the deoxygenated circulation pump running to deoxygenate using waste heat and maintain the water temperature in the deoxygenated water tank. At the same time, add ammonia to the deaerator to increase the pH.
[0010] Step 3: Continuously monitor the feedwater using an online dissolved oxygen meter. When the dissolved oxygen in the feedwater is less than 20 ppb, stop the deoxygenated water tank circulation pump.
[0011] Step 4: When the high-pressure steam drum wall temperature drops below 100℃, perform water replenishment operation, replenishing water to above 0mm;
[0012] Step 5: After the pressure in the high and low pressure steam drums drops below 0.3 MPa, ammonia is added to the steam drums, and forced circulation is performed during the process to increase the pH.
[0013] Step 6: Start the nitrogen generator, then open the nitrogen supply valves of each system, and at the same time monitor the pressure in the steam drum and adjust the power of the nitrogen generator in real time to maintain the pressure in the steam drum;
[0014] Step 7: As the steam drum temperature drops further, turn on the deaerator water tank to maintain the steam drum liquid level while adjusting the nitrogen generator power to maintain pressure.
[0015] Preferably, in step 2, the temperature of the deoxygenated water tank is maintained at 110℃-150℃; and the pH value of the ammonia addition operation is controlled at 8.8-9.5.
[0016] Preferably, in step 2, the temperature of the deoxygenated water tank is maintained at 110℃-120℃, and the pH index of the ammonia addition operation is controlled at 8.8-9.3.
[0017] Preferably, in step 5, the pH value of the steam drum during the ammonia addition operation is controlled at 9.3-9.8.
[0018] Preferably, in step 5, the pH value of the steam drum during the ammonia addition operation is controlled at 9.5-9.8.
[0019] Preferably, in step 6, the nitrogen generator uses pressure swing adsorption (PSA) to directly obtain nitrogen from compressed air.
[0020] Preferably, in step 6, the pressure of the steam drum after nitrogen filling by the nitrogen generator is maintained at 0.1-0.5 MPa.
[0021] Preferably, in step 6, the pressure of the steam drum after nitrogen filling by the nitrogen generator is maintained at 0.1-0.3 MPa.
[0022] The beneficial effects of this invention are:
[0023] (1) Shorten the start-up and shutdown time of the gas turbine unit to achieve rapid start-up and shutdown.
[0024] (2) Isolate the outside air and inhibit dissolved oxygen corrosion.
[0025] (3) The original water in the boiler is not discharged or wasted, thus saving water resources.
[0026] (4) No wastewater is discharged during boiler maintenance, achieving zero wastewater discharge.
[0027] (5) The waste heat boiler does not require chemical cleaning before restarting, saving manpower and material costs. Attached Figure Description
[0028] Figure 1 This is a schematic diagram of a wet nitrogen purging maintenance method for rapid start-up of a gas turbine waste heat boiler;
[0029] Figure 2 This is a front view of the waste heat boiler;
[0030] Figure 3 This is a side view of a waste heat boiler.
[0031] Figure 4 This is a schematic diagram of the nitrogen production process;
[0032] Explanation of reference numerals in the attached diagram: 1. Steam inlet pipe; 2. Steam outlet pipe; 3. Upper outer wall measuring point; 4. Pressure gauge; 5. Lower outer wall measuring point; 6. Water supply pipe; 7. Water temperature measuring point; 8. Downward seamless steel pipe SA106B; 9. Nitrogen inlet; 10. Steam temperature measuring point; 11. Air compressor; 12. Air purification device; CG. Air storage tank; 13. Oxygen-nitrogen separation device PSA; 14. Filter; 15. Nitrogen buffer tank; 16. Flow meter; 17. Nitrogen detection device; 18. Detailed Implementation
[0033] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.
[0034] Example 1
[0035] The No. 6 unit of a gas turbine power plant uses a combined cycle dual-pressure condensing steam turbine manufactured by Shanghai Turbine Co., Ltd., model LZN55-5.6 / 0.65, and a generator model WX18Z-054LLT. The boiler is a three-pressure forced cycle gas turbine waste heat boiler manufactured by Hangzhou Boiler Factory. In the previous start-up and shutdown process, boiler draining and waste heat drying were used for maintenance. However, due to the horizontal arrangement of the evaporator tubes, water could not be completely drained from the evaporator tubes, resulting in poor maintenance effectiveness. Therefore, it is proposed to optimize the waste heat drying maintenance measures. For example... Figure 1 As shown, the specific operation is as follows:
[0036] 1) Close all isolation valves from the high-pressure system to the boiler expansion tank.
[0037] 2) Replenish the deoxygenated water tank with water and keep the deoxygenated circulation pump running to deoxygenate using waste heat and maintain the water temperature in the deoxygenated water tank. At the same time, add ammonia to the deaerator to raise the pH value of the liquid in the deoxygenated water tank to 9.0.
[0038] 3) Continuously monitor the feedwater using an online dissolved oxygen meter. When the dissolved oxygen in the feedwater is less than 20 ppb, stop the deoxygenated water tank circulation pump.
[0039] 4) When the high-pressure steam drum wall temperature drops below 100℃, perform a water replenishment operation, replenishing water to above 0mm.
[0040] 5) After the pressure of the high and low pressure steam drums drops to 0.3 MPa, ammonia is added to the steam drums. During the strengthening process, forced circulation is carried out to increase the pH value of the liquid in the high and low pressure steam drums to 9.6.
[0041] 6) Start the nitrogen generator, then open the nitrogen supply valves of each system, and at the same time monitor the pressure in the steam drum and adjust the power of the nitrogen generator in real time to maintain the pressure in the steam drum at 0.3MPa.
[0042] 7) As the steam drum temperature drops further, open the deaerator water tank, maintain the steam drum liquid level, and adjust the nitrogen generator power to maintain the pressure at 0.3MPa.
[0043] The evaluation indicators for nitrogen purging maintenance methods are mainly based on the shutdown time and water vapor quality at startup. This is primarily used to determine whether nitrogen purging maintenance can meet the requirements for different startup and shutdown times and whether it can inhibit dissolved oxygen corrosion. Once dissolved oxygen corrosion occurs, the Fe content (in ppb) in the water vapor will inevitably fail to meet the standards. Sampling results after startup are shown in Table 1.
[0044] Table 1
[0045]
[0046] From the perspective of start-up and shutdown time, whether it's a short start-up or shutdown of a few days or a long start-up or shutdown of up to four months, the nitrogen purging maintenance method can meet the requirements for smooth start-up. Compared with the traditional water draining maintenance method, the method provided by this invention saves water resources and eliminates the need for chemical cleaning and large-volume demineralized water flushing before start-up. From the perspective of steam quality after start-up, the Fe content in all steam is low, meeting the standard requirements. Therefore, the wet nitrogen purging maintenance method provided by this invention can inhibit dissolved oxygen corrosion, reduce chemical cleaning, and extend boiler life.
[0047] Example 2
[0048] The No. 1 unit of a gas turbine power plant uses a combined cycle dual-pressure condensing steam turbine manufactured by Shanghai Turbine Co., Ltd., model LZN55-5.6 / 0.65, and a generator model WX18Z-054LLT. The boiler is a three-pressure forced cycle gas turbine waste heat boiler manufactured by Hangzhou Boiler Factory. In the previous start-up and shutdown process, boiler draining and waste heat drying were used for maintenance. However, due to the horizontal arrangement of the evaporator tubes, water could not be completely drained from the evaporator tubes, resulting in poor maintenance effectiveness. Therefore, it is proposed to optimize the waste heat drying maintenance measures. For example... Figure 1 As shown, the specific operation is as follows:
[0049] 1) Close all isolation valves from the high-pressure system to the boiler expansion tank.
[0050] 2) Replenish the deoxygenated water tank with water and keep the deoxygenated circulation pump running. Use waste heat to deoxygenate and maintain the water temperature in the deoxygenated water tank. At the same time, add ammonia to the deaerator to bring the pH value of the liquid in the deoxygenated water tank to 8.9.
[0051] 3) Continuously monitor the feedwater using an online dissolved oxygen meter. When the dissolved oxygen in the feedwater is less than 20 ppb, stop the deoxygenated water tank circulation pump.
[0052] 4) When the high-pressure steam drum wall temperature drops below 100℃, perform a water replenishment operation, replenishing water to above 0mm.
[0053] 5) After the pressure of the high and low pressure steam drums drops to 0.3 MPa, ammonia is added to the steam drums. During the strengthening process, forced circulation is carried out to increase the pH value of the liquid in the high and low pressure steam drums to 9.5.
[0054] 6) Start the nitrogen generator, then open the nitrogen supply valves of each system, and at the same time monitor the pressure in the steam drum and adjust the power of the nitrogen generator in real time to maintain the pressure in the steam drum at 0.3MPa.
[0055] 7) As the steam drum temperature drops further, open the deaerator water tank, maintain the steam drum liquid level, and adjust the nitrogen generator power to maintain the pressure at 0.2MPa.
[0056] The evaluation indicators for nitrogen purging maintenance methods are mainly based on the shutdown time and water vapor quality at startup. This is primarily used to determine whether nitrogen purging maintenance can meet the requirements for different startup and shutdown times and whether it can inhibit dissolved oxygen corrosion. Once dissolved oxygen corrosion occurs, the Fe content (in ppb) in the water vapor will inevitably fail to meet the standards. Sampling results after startup are shown in Table 2.
[0057] Table 2
[0058]
[0059]
[0060] From the perspective of start-up and shutdown time, whether it's a short start-up or shutdown of a few days or a long start-up or shutdown of up to four months, the nitrogen purging maintenance method can meet the requirements for smooth start-up. Compared with the traditional water draining maintenance method, the method provided by this invention saves water resources and eliminates the need for chemical cleaning and large-volume demineralized water flushing before start-up. From the perspective of steam quality after start-up, the Fe content in all steam is low, meeting the standard requirements. Therefore, the wet nitrogen purging maintenance method provided by this invention can inhibit dissolved oxygen corrosion, reduce chemical cleaning, and extend boiler life.
[0061] Example 3
[0062] The No. 2 unit of a gas turbine power plant uses a combined cycle dual-pressure condensing steam turbine manufactured by Shanghai Turbine Co., Ltd., model LZN55-5.6 / 0.65, and a generator model WX18Z-054LLT. The boiler is a three-pressure forced cycle gas turbine waste heat boiler manufactured by Hangzhou Boiler Factory. In the previous start-up and shutdown process, boiler draining and waste heat drying were used for maintenance. However, due to the horizontal arrangement of the evaporator tubes, water could not be completely drained from the evaporator tubes, resulting in poor maintenance effectiveness. Therefore, it is proposed to optimize the waste heat drying maintenance measures. For example... Figure 1 As shown, the specific operation is as follows:
[0063] 1) Close all isolation valves from the high-pressure system to the boiler expansion tank.
[0064] 2) Replenish the deoxygenated water tank with water and keep the deoxygenated circulation pump running to deoxygenate using waste heat and maintain the water temperature in the deoxygenated water tank. At the same time, add ammonia to the deaerator to bring the pH value of the liquid in the deoxygenated water tank to 8.8.
[0065] 3) Continuously monitor the feedwater using an online dissolved oxygen meter. When the dissolved oxygen in the feedwater is less than 20 ppb, stop the deoxygenated water tank circulation pump.
[0066] 4) When the high-pressure steam drum wall temperature drops below 100℃, perform a water replenishment operation, replenishing water to above 0mm.
[0067] 5) After the pressure of the high and low pressure steam drums drops to 0.3 MPa, ammonia is added to the steam drums. During the strengthening process, forced circulation is carried out to increase the pH value of the liquid in the high and low pressure steam drums to 9.4.
[0068] 6) Start the nitrogen generator, then open the nitrogen supply valves of each system, and at the same time monitor the pressure in the steam drum and adjust the power of the nitrogen generator in real time to maintain the pressure in the steam drum at 0.3MPa.
[0069] 7) As the steam drum temperature drops further, open the deaerator water tank, maintain the steam drum liquid level, and adjust the nitrogen generator power to maintain the pressure at 0.1 MPa.
[0070] The evaluation indicators for nitrogen purging maintenance methods are mainly based on the shutdown time and water vapor quality at startup. This is primarily used to determine whether nitrogen purging maintenance can meet the requirements for different startup and shutdown times and whether it can inhibit dissolved oxygen corrosion. Once dissolved oxygen corrosion occurs, the Fe content (in ppb) in the water vapor will inevitably fail to meet the standards. Sampling results after startup are shown in Table 3.
[0071] Table 3
[0072]
[0073] From the perspective of start-up and shutdown time, whether it's a short start-up or shutdown of a few days or a long start-up or shutdown of up to four months, the nitrogen purging maintenance method can meet the requirements for smooth start-up. Compared with the traditional water draining maintenance method, the method provided by this invention saves water resources and eliminates the need for chemical cleaning and large-volume demineralized water flushing before start-up. From the perspective of steam quality after start-up, the Fe content in all steam is low, meeting the standard requirements. Therefore, the wet nitrogen purging maintenance method provided by this invention can inhibit dissolved oxygen corrosion, reduce chemical cleaning, and extend boiler life.
[0074] Example 4
[0075] A type of waste heat boiler, such as Figure 2 and Figure 3As shown, the wet nitrogen purging maintenance method applied to any of Examples 1 to 3 includes: steam inlet pipe 1, steam outlet pipe 2, upper outer wall measuring point 3, pressure gauge 4, lower outer wall measuring point 5, water supply pipe 6, water temperature measuring point 7, descending seamless steel pipe SA106B 8, nitrogen purging inlet 9, and steam temperature measuring point 10.
[0076] All pipes in the waste heat boiler (such as steam inlet pipe 1, steam outlet pipe 2, feedwater pipe 6, and downcomer pipe 8) are made of SA106B seamless pipe. Operators can obtain real-time parameters of the waste heat boiler based on the measuring points and instruments on the boiler, and then perform operations such as adding ammonia, replenishing water, and supplying nitrogen based on these parameters.
[0077] Furthermore, the nitrogen generator provided in this application includes: an air compressor 11, an air purification device 12, an air storage tank CG 13, an oxygen-nitrogen separation device PSA 14, a filter 15, a nitrogen buffer tank 16, a flow meter 17, and a nitrogen detection device 18. This nitrogen generator uses pressure swing adsorption (PSA) to directly obtain nitrogen from compressed air. Figure 4 As shown, air passes sequentially through air compressor 11, air purification device 12, air storage tank CG13, oxygen-nitrogen separation device PSA14, filter 15, nitrogen buffer tank 16, flow meter 17 and nitrogen detection device 18, which can obtain unqualified nitrogen and qualified nitrogen. Qualified nitrogen is introduced into the waste heat boiler for maintenance through nitrogen filling inlet 9.
[0078] In summary, this invention provides a wet nitrogen purging maintenance method suitable for the rapid start-up and shutdown of waste heat boilers in gas turbine units. It has technical advantages such as rapid start-up and shutdown, inhibition of dissolved oxygen corrosion, energy saving and environmental protection, and has broad industrial application prospects and huge potential value.
Claims
1. A wet nitrogen purging maintenance method for rapid start-up of a gas turbine waste heat boiler, characterized in that, include: Step 1: Close all isolation valves from the high-pressure system to the boiler expansion tank; Step 2: Replenish the deoxygenated water tank with water and keep the deoxygenated circulation pump running to deoxygenate using waste heat and maintain the water temperature in the deoxygenated water tank. At the same time, add ammonia to the deaerator to increase the pH value of the liquid in the deoxygenated water tank. In Step 2, the temperature of the deoxygenated water tank is maintained at 110℃-150℃; the pH value during the ammonia addition operation is controlled at 8.8-9.
5. Step 3: Continuously monitor the feedwater using an online dissolved oxygen meter. When the dissolved oxygen in the feedwater is less than 20 ppb, stop the deoxygenated water tank circulation pump. Step 4: When the high-pressure steam drum wall temperature drops below 100℃, perform water replenishment operation, replenishing water to above 0 mm; Step 5: After the pressure in the high-pressure and low-pressure steam drums drops below 0.3 MPa, ammonia is added to the steam drums. Forced circulation is performed during ammonia addition to increase the pH value of the liquid in the high-pressure and low-pressure steam drums. In Step 5, the pH value of the steam drums during ammonia addition is controlled between 9.3 and 9.
8. Step 6: Start the nitrogen generator, then open the nitrogen supply valves of each system, and simultaneously monitor the steam drum pressure and adjust the nitrogen generator power in real time to maintain the pressure in the steam drum; in Step 6, the nitrogen generator uses pressure swing adsorption to directly obtain nitrogen from compressed air; in Step 6, the steam drum pressure after nitrogen filling by the nitrogen generator is maintained at 0.1-0.5 MPa. Step 7: As the steam drum temperature drops further, turn on the deaerator water tank to maintain the steam drum liquid level while adjusting the nitrogen generator power to maintain pressure.