Generator set black start method based on boiler side 5% drain bypass system
By installing electric adjustment doors and auxiliary steam connection boxes on the boiler side of the thermal power plant, using 5% water-breathing on the boiler side as the starting steam source, the black start-up problem of thermal power plant is solved, and fast and low-cost start-up is achieved, which improves safety and reliability adapts to the needs of the new power market.
Patent Information
- Application Number
- CN202411519775.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-29
- Publication Date
- 2024-12-17
AI Technical Summary
During power outages or cold starts, thermal power plants lack starting steam sources, especially electric water supply pumps or high and low voltage bypass systems, which makes it difficult to start the boiler, and the existing black start method is costly and unsafe.
Using a 5% hydrophobic bypass system on the boiler side, by installing electric adjustment doors and auxiliary steam connection boxes on the boiler side, 5% hydrophobic water on the boiler side is used as the initial steam source for the start-up, so that the condensate is directly poured into the boiler drum, satisfying the start-up Initial steam pressure demand, and switch to cooling and then supply steam after the unit is operating normally.
It significantly shortens the start time of boilers and generator sets, reduces costs, improves the safety and reliability of thermal power plants, avoids high-cost transformation and safety risks, and meets the black start-up needs of power plants in the new power market.
Smart Images
Figure CN119145929A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of emergency recovery of power plants in power systems, and specifically to a black start method for a generator set based on a 5% drain bypass system on a boiler side, which aims to improve the rapid recovery capability of a power plant after a power outage or cold start and ensure the stable operation of a power grid. Background Art
[0002] With the vigorous development of new energy, the utilization hours of thermal power units are decreasing year by year due to the influence of wind power and photovoltaic power. In particular, the large-scale operation of photovoltaic power stations is restricted by the promotion of energy storage technology. In order to increase the amount of photovoltaic power grid-connected electricity, the load of thermal power units is gradually reduced during the day, and the operation of a single unit in a thermal power plant has become the norm. When a single unit in a thermal power plant trips during operation, the entire plant faces the problem of black start.
[0003] The black start of a power plant mainly involves two aspects: external power supply back to the plant power supply and recovery of the plant steam source. With the maturity of UHV transmission technology, the security of regional power grids has been strengthened. Therefore, there is no difficulty in the black start of a single power plant. The main difficulty is the recovery of the plant steam source, which is used for boiler fuel atomization, air preheater soot blowing, turbine steam seal steam source, etc.
[0004] In particular, with the improvement of equipment reliability, cost control of thermal power plant construction and the requirement to reduce plant electricity consumption, some power plants have cancelled electric feedwater pumps. Therefore, some power plants still face the problem of starting the steam source to drive the steam-driven feedwater pumps.
[0005] Therefore, as the single-unit operation of power plants becomes normalized, some power plants are faced with the problem of black start with no starting steam source, no boiler water supply method, and inability to connect the steam generated by the boiler to the plant steam system.
[0006] At present, conventional black-start power plants use start-up boilers to supply steam. The investment in the transformation of conventional start-up boilers is about 5 million yuan, which is a large investment and requires a lot of subsequent maintenance work. Some power plants need to build oil stations for start-up boilers. As a major source of danger, oil stations bring risks to the safety and environmental protection of power plants.
[0007] The existing black start method uses electric feed water pumps, starter boilers, etc., which are costly. For power plants that have already been put into operation and do not have electric pumps, starter boilers, high and low pressure bypasses, the additional cost is high and due to space limitations, it cannot meet the requirements. Summary of the invention
[0008] The present invention provides a black start method for the generator set based on the 5% drain bypass system on the boiler side for the power plant that has been put into operation and has no start-up boiler, electric feed water pump or high and low pressure bypass system, so as to realize the direct water supply of condensate to the boiler drum and solve the problem of water supply in the initial stage of boiler start-up. Through the existing 5% boiler start-up drain, the boiler steam is connected to the plant steam main pipe to realize the steam supply to the shaft seal and the steam source demand of the steam driven feed water pump when the steam turbine is started. The black start of the thermal power plant can be realized with relatively low cost and a small amount of modification.
[0009] The technical solution of the present invention is as follows: A method for black starting a generator set based on a boiler side 5% drain bypass system, characterized in that it comprises the following steps: S1: Install an electric adjustment gate in the 5% drain pipe on the boiler side. The maximum pressure difference before and after the electric adjustment gate reaches 6MPa, which meets the flow rate of 20t / h; connect a branch line after the electric valve to the auxiliary steam header; S2: Use the 5% drain on the boiler side as the initial steam source for startup, open the four 5% drain electric doors on the boiler side, and the generated steam passes through the 5% drain pipe electric adjustment door on the boiler side and the 5% drain pipe electric adjustment door on the turbine side, and is sent to the auxiliary steam header for steam supply. Drain fully before supplying the auxiliary steam header, and ensure that the steam superheat is greater than 50℃; S3: When the unit is started, condensate is used to fill the boiler drum with water; the boiler ignition procedure is started to gradually increase the furnace temperature, and the steam from the auxiliary steam header is used to supply the unit with steam for starting. Through combustion adjustment, the steam pressure is maintained at 3MPa at the initial stage of starting; S4: After the boiler main steam temperature reaches the turbine start-up parameter requirements, start the turbine operation; S5: When the unit is operating normally, put the cold re-supply steam into operation, shut down the 5% drain bypass supply to the auxiliary steam manifold, and switch the steam supply to the auxiliary steam manifold to the cold re-supply steam.
[0010] After startup, the four-stage pumping pressure is set to 0.5MPa, and the drum pressure is controlled not to exceed 10MPa.
[0011] After the unit operates normally, switch the auxiliary steam header steam to cold resupply steam and shut down the 5% drain bypass system.
[0012] An electric gate valve and a temperature meter are installed in the branch circuit, and both the temperature meter and the electric gate valve are connected to the control system signal control.
[0013] The 5% drain on the boiler side is connected to the condenser through a pipe.
[0014] In step S4, closely monitor the boiler's steam temperature, steam pressure, and water level to ensure that the boiler operates within a safe range.
[0015] In step S4, closely monitor the boiler steam temperature, steam pressure, and water level. When the steam temperature and steam pressure fluctuate greatly, control the steam pressure stability by adjusting the boiler combustion, increasing or decreasing the coal supply, increasing or decreasing the primary air pressure, and adjusting the hot and cold air doors. Control the steam temperature stability by adjusting the cooling water. The steam turbine regulating valve assists the boiler in stabilizing the pressure by controlling the valve position opening, strengthens the monitoring of the main steam pressure set value and the actual value, and maintains the deviation between the set value and the actual value within 0.5MPa. The water level is stabilized by controlling the amount of water supply by increasing or decreasing the speed of the small machine. Under abnormal circumstances, it is necessary to manually adjust the opening of the feedwater pump recirculation door, the drum emergency drain door, the unit load, fixed discharge, continuous discharge, etc. to assist in adjusting the drum water level, so as to ensure that the boiler operates within a safe range.
[0016] The 5% drain system is located at the bottom of the flue wall at the rear of the boiler, and its flow rate is 5% of the rated evaporation capacity of the boiler. During the ignition and startup of the boiler, turning on this system can speed up the rate of increase of the main steam temperature, allowing the boiler to quickly increase the main steam temperature under a lower heat load, meet the turbine start-up requirements, and achieve energy saving.
[0017] The present invention installs an electric regulating valve at the 5% drain point on the boiler side. The maximum pressure difference before and after the electric regulating valve is 6MPa, which meets the flow rate of 20t / h. A pressure measuring point is set behind the electric regulating valve as the feedback signal of the electric regulating valve. A branch is set using the 5% drain pipeline and connected to the auxiliary steam header.
[0018] Advantages of the present invention: 1. The feedwater pump turbine of the present invention is started, and condensed water is used to feed water to the boiler. After completion, the condensed water is switched to the deaerator for operation.
[0019] 2. The present invention uses 5% drain as the initial steam source for startup, which is connected to the auxiliary steam header after decompression, solving the problem of black start in thermal power plants and significantly shortening the startup time of boilers and generator sets.
[0020] 3. Use a condensate pump to directly supply water to the boiler drum. Through combustion adjustment, the steam pressure is maintained at 3MPa during the initial startup, while the main steam temperature is controlled at the same time.
[0021] 4. It solves the problem of black start of existing thermal power plants, which requires the addition of starting boilers, electric feed water pumps, and large-scale renovation of high and low pressure bypass systems. It solves the problem of black start of thermal power plants in adapting to the new power market and improves the safety and reliability of thermal power plants. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is a piping structure diagram of the 5% hydrophobic system of the present invention.
[0023] See also Figure 1 .
[0024] A method for black starting a generator set based on a boiler side 5% drain bypass system comprises the following steps: S1: Install an electric adjustment gate in the 5% drain pipe on the boiler side. The maximum pressure difference before and after the electric adjustment gate reaches 6MPa, which meets the flow rate of 20t / h; connect a branch line after the electric valve to the auxiliary steam header; S2: Use the 5% drain on the boiler side as the initial steam source for startup, open the four 5% drain electric doors on the boiler side, and the generated steam passes through the 5% drain pipe electric adjustment door on the boiler side and the 5% drain pipe electric adjustment door on the turbine side, and is sent to the auxiliary steam header for steam supply. Drain fully before supplying the auxiliary steam header, and ensure that the steam superheat is greater than 50℃; S3: When the unit is started, condensate is used to fill the boiler drum with water; the boiler ignition procedure is started to gradually increase the furnace temperature, and the steam from the auxiliary steam header is used to supply the unit with steam for starting. Through combustion adjustment, the steam pressure is maintained at 3MPa at the initial stage of starting; S4: After the boiler main steam temperature reaches the turbine start-up parameter requirements, start the turbine operation; S5: When the unit is operating normally, put the cold re-supply steam into operation, shut down the 5% drain bypass supply to the auxiliary steam manifold, and switch the steam supply to the auxiliary steam manifold to the cold re-supply steam.
[0025] After startup, the four-stage pumping pressure is set to 0.5MPa, and the drum pressure is controlled not to exceed 10MPa.
[0026] After the unit operates normally, switch the auxiliary steam header steam to cold resupply steam and shut down the 5% drain bypass system.
[0027] An electric gate valve and a temperature meter are installed in the branch circuit, and both the temperature meter and the electric gate valve are connected to the control system signal control.
[0028] The 5% drain on the boiler side is connected to the condenser through a pipe.
[0029] In step S4, closely monitor the boiler's steam temperature, steam pressure, and water level to ensure that the boiler operates within a safe range.
[0030] After startup, the pressure of the fourth extraction is reduced to 0.5MPa, and the drum pressure is controlled not to exceed 10MPa. The steam source of the feed pump turbine can be switched. After stabilization, the auxiliary steam source is switched to the fourth extraction, and the 5% drain bypass system is shut down.
[0031] An electric gate valve and a temperature gauge are installed in the auxiliary steam manifold branch, and both the temperature gauge and the electric gate valve are connected to the control system signal control.
[0032] The following is a detailed analysis of the working principle and advantages of this generator set black start method based on the boiler side 5% drain bypass system: Drain bypass system settings: An electric adjustment door is installed in the 5% drain pipe on the boiler side. The electric adjustment door can withstand a maximum front-to-back pressure difference of up to 6MPa and meet a flow demand of 20t / h.
[0033] A branch line is connected to the auxiliary steam manifold after the electric valve so as to send the drain steam into the auxiliary steam manifold for steam supply.
[0034] Steam source utilization at the initial start-up: The 5% drain on the boiler side is used as the steam source at the initial start-up. By opening the four 5% drain electric doors on the boiler side, the generated steam is sent into the auxiliary steam manifold through the electric adjustment door.
[0035] Before supplying the auxiliary steam header, sufficient drainage should be carried out to ensure that the steam superheat is greater than 50°C to prevent steam from carrying water and causing damage to the equipment.
[0036] Unit startup and steam supply: When the unit is started, condensate is used to fill the boiler drum, and the boiler ignition procedure is started to gradually increase the furnace temperature.
[0037] The steam in the auxiliary steam header is used for unit startup. Through combustion adjustment, the steam pressure at the initial stage of startup is maintained at 3MPa.
[0038] Steam turbine startup and steam supply switching: After the boiler main steam temperature reaches the turbine start-up parameter requirements, the turbine start-up operation is carried out.
[0039] After the unit is operating normally, put the cold re-supply steam into operation, shut down the 5% drain bypass to supply the auxiliary steam manifold, and switch the steam supply to the auxiliary steam manifold to the cold re-supply steam.
[0040] Using 5% of the boiler side drain as the starting steam source can reduce dependence on external energy and improve the starting efficiency of the unit.
[0041] By installing an electric adjustment door in the drain pipe and conducting sufficient drainage, the steam superheat can be ensured to be greater than 50°C, preventing steam from carrying water and causing damage to the equipment.
[0042] This method can be adjusted and optimized according to the actual situation and needs of the unit, such as adjusting the opening of the electric adjustment door, controlling the steam pressure and temperature, etc.
[0043] Compared with the traditional startup method, this method can make full use of the energy of the boiler-side steam trap, reduce energy waste and emissions, and meet the requirements of energy conservation and environmental protection.
[0044] When a power system failure causes a large-scale power outage, this method can be used as part of a black start plan to reduce the losses caused by the power outage by quickly starting the generator set and restoring power supply.
[0045] In summary, this black start method of the generator set based on the 5% drain bypass system on the boiler side has the advantages of improving starting efficiency, protecting equipment safety, high flexibility, energy saving and environmental protection, and rapid power supply restoration.
Claims
1. A black start method for a generator set based on a 5% drain bypass system on the boiler side, characterized in that: The following steps are involved: S1: Install an electric adjustment valve in the 5% drain pipe on the boiler side. The maximum pressure difference before and after the electric adjustment valve reaches 6 MPa, which meets the flow rate of 20 t / h. Connect a branch line after the electric valve to the auxiliary steam manifold. S2: Use the 5% drain on the boiler side as the initial steam source for startup. Open the four 5% drain electric valves on the boiler side. The generated steam passes through the electric adjustment valves on the 5% drain pipe on the boiler side and the electric adjustment valves on the 5% drain pipe on the turbine side and is sent to the auxiliary steam header for steam supply. Drain the steam fully before supplying it to the auxiliary steam header and ensure that the steam superheat is greater than 50°C. S3: When the unit is started, condensate is used to fill the boiler drum; the boiler ignition procedure is started, the furnace temperature is gradually increased, and the steam from the auxiliary steam header is used to supply the unit with steam for starting. Through combustion adjustment, the steam pressure is maintained at 3MPa during the initial start-up period. S4: After the boiler main steam temperature reaches the turbine start-up parameter requirements, start the turbine operation; S5: When the unit is operating normally, put the cold re-supply steam into operation, shut down the 5% drain bypass supply to the auxiliary steam manifold, and cut the steam supply from the auxiliary steam manifold to the cold re-supply steam.
2. The method for black starting a thermal power generator set based on a 5% drain bypass system on the boiler side according to claim 1, characterized in that: After starting up, the four-stage pumping pressure is reduced to 0.5MPa, and the boiler pressure is controlled not to exceed 10MPa.
3. The method for black starting a thermal power generator set based on a 5% drain bypass system on the boiler side according to claim 1, characterized in that: After the unit is operating normally, the steam in the auxiliary steam header will be switched to cold resupply steam, and the 5% drain bypass system will be shut down.
4. The method for black starting a thermal power generator set based on a 5% drain bypass system on the boiler side according to claim 1, characterized in that: An electric gate valve and a temperature meter are installed in the branch line, and both the temperature meter and the electric gate valve are connected to the control system signal control.
5. The method for black starting a thermal power generator set based on a 5% drain bypass system on the boiler side according to claim 1, characterized in that: The 5% drain on the boiler side is connected to the condenser through a pipe.
6. The method for black starting a thermal power generator set based on a 5% drain bypass system on the boiler side according to claim 1, characterized in that: In step S4, closely monitor the boiler's steam temperature, steam pressure, and water level to ensure that the boiler operates within a safe range.