Discussion on Starting Mode of 600MW Power Unit without Electric Pump Wang Jian, Jiang Xiaojun (Zhejiang Electric Power Construction Corporation, Ningbo, Zhejiang, 315010) Turning a small steam turbine driven steam pump to realize the cold starting of the unit. Before the unit rushed, the boiler was ignited after the steam pump pre-pump was used to feed the boiler. Auxiliary steam impulses a small steam turbine and continues to replenish the boiler with a steam pump. When a certain load is reached, another small steam turbine is started with a four-stage extraction steam, and the steam is then used as a backup. The actual operation shows that: Unit 6 was forced to use a non-electric pump due to a fault in the electric pump. The cold start was successful in the 4X600MW phase 2 project of the Jiaxing Power Plant. The 6th steam turbine was of the N600-167/538/538 type subcritical, An intermediate reheat, single-axis, four-cylinder four-bar steam, condensing steam turbine. The water supply system uses 2 sets of 50% steam-powered water feed pumps and 1 set of 30% electric power feed pumps.
Design parameters of the steam source of the steam feed water pump group The design parameters of the steam turbine for the water pump are three steam sources: the normal working steam source uses four steam extractions; the standby steam source comes from the reheater cold-end steam; and the commissioning steam source comes from the auxiliary steam. Table 1 shows the design parameters of each steam source under several working conditions;
Table 1 steam turbine design parameters for the four steam extraction section of the steam extractor reheater cold steam steam pressure MPa temperature / pressure MPa temperature; c pressure MPa temperature / C 50% rated 30% rated 2 unit without electric pump start feasibility And the key occupies 1~4 丨 during commissioning, the unit can not start normally because of the supercharger level failure of the electric feed pump. As the maintenance took more than half a month and there was no spare core pack, this seriously affected the normal commissioning process of Unit 6.
In order to smooth the commissioning work and try to restore unnecessary time loss, it was decided to start the unit with an auxiliary steam impulse steam pump. Other domestic power plants have had precedents for the unit to start without electric pumps. Drawing on successful experience, after careful analysis, it is believed that relying on the current design of this unit, it is feasible to use a non-electric pump to start.
According to the design, the steam source used for debugging the small turbine is an auxiliary steam, and the auxiliary steam of the four units can be supplied to each other. Therefore, a neighboring engine is used for auxiliary steam to drive a set of feed pump to start the unit. After the unit is connected to the grid and rises to a certain load, use the machine to extract the steam from the fourth stage to another pump, and then the steam source is used as backup; when the steam is extracted to a certain parameter, the steam pump is incorporated into the operation. . This completes the unit without electric pump start. Then continue to increase the load in accordance with the normal operating procedures, cut the steam from another small turbine to four, until full load.
As mentioned above, the following basic conditions are key points for the implementation of the plan and must be considered.
1Because the electric pump core package is removed, it must be ensured that the electric pump is reliably isolated and the valves connected to the interface pipes of the main body should be closed tightly and work reliably. This is the basic premise for implementing the plan. These valves include: electric pump inlet and outlet electric valve, electric pump outlet bypass valve rear isolation valve, electric pump recirculation regulator valve front and rear isolation valve, electric pump booster level outlet electric valve, electric pump middle tap outlet electric valve. In the process of boiler warming, boosting and loading, it is necessary to closely monitor the tightness of the valve.
22 The original design idea of ​​the auxiliary steam source is used as a steam turbine commissioning test. The inlet steam pipeline is the test data of the auxiliary steam turbine of Table 2. The auxiliary steam pressure is MlPa Small steam turbine low pressure throttle opening/% steam pump speed/(rmin-1 ) Steam pump outlet pressure MPa Steam pump outlet flow (th-') 3 Boiler drum water level control points are as follows: As the steam pump speed range is relatively small compared to the electric pump, the drum water level is not easy to control. Because the non-electric pump uses the steam pump pre-pump or the condensate pump to feed the boiler water, during the boiler's heating and pressure raising (less than 2 MPa), the fixed row and connecting means are adopted; when the steam drum pressure rises above 2 MPa At the same time, according to the test data of the auxiliary steam turbine, the speed of the steam pump is adjusted to adjust the water level of the steam drum. When the steam pump speed is greater than 2200r/nin, the steam pump automatically controls the water level of the steam drum.
3 electric pump start operation points and precautions 1 electric pump start-up mode is different, non-normal start should enforce the following chain signal and carry out logical modification: (1) Forced host trips when the steam pump and the front pump chain trip; (2 ) Forcing the linkage of the steam pump and its pre-pump when the boiler MFT is forced; (3) Forcibly implementing the high-side shut-off logic when the high-side desuperheating water differential is low; (4) Forcing the boost valve to fully open when the electric valve at the outlet of the steam pump is fully open. And the middle tap motor valve automatically open logic; (5) when the small turbine speed is less than 2200rmn, manually adjust the steam pump speed to control the drum water level.
2 When the boiler is flooded, it should be based on the actual situation, use the steam pump front pump or condensate water pump to the boiler water to the normal water level low position.
3 After the boiler water is applied, it is ignited. Before the pressure of the steam drum rises to 2 MPa, the water level of the steam drum is controlled by using the outlet valve of the steam pump, the fixed row, and the row discharge valve to be at a slightly higher position.
During the start-up period, the auxiliary steam is taken from the adjacent cold reheater, which is beneficial to increase the steam parameters. At the same time, the adjacent machine should maintain the load stability so as to maintain the auxiliary steam parameters within the design value range.
When the auxiliary steam is used to drive the small steam turbine, the steam pump is started, and various parameters under different rotation speeds are obtained by experiments; at this time, another front-stage pump is in standby state, and if the steam drum pressure is lower than 1 MPa during the revolution , can give the steam bag timely replenishment.
36 When the drum pressure rises to 2 MPa, adjust the steam pump speed to adjust the water level.
37 Slowly turn on the high and low side and put it into the bypass system. When the high-side is turned on, it is necessary to maintain the pressure of the steam drum above 2 MPa and avoid large fluctuations. At the same time, the temperature of the high-side valve should be closely monitored to make it as close to the upper limit as possible to reduce the amount of desuperheating water.
38 fully open steam pump recirculation valve, make the steam pump run under large flow; strengthen the monitoring of exhaust temperature of small steam turbine, and promptly use the rear cylinder to spray water.
After the 39 steam pump steam source is cut to four draws, it shall be pumped and the load shall be increased. The logic of “high side turn off when the high temperature water differential pressure is low†shall be restored. At this time, the start of the non-electric pump is completed.
310 The following points should also be noted during the start-up process: (1) As soon as possible, the warm-up pipe of the high-pressure steam source of the steam pump is used as an auxiliary steam source for the auxiliary steam for the steam pump; (2) The operation of the steamer is closely monitored to prevent the auxiliary steam from passing through. (4) If the boiler MFT can not meet the boiler water supply needs, it should promptly carry out the boring table 3 turbine rushing. On-grid. Operating parameters at low load host state auxiliary pressure MPa small steam turbine B low pressure door opening steam pump B speed steam pump B outlet pressure MPa steam pump B outlet flow feedwater pressure / M water supply flow / (mainboard empty load 4 electric pump Start up the actual operation situation 1. Before the unit rushes to turn, first use the steam pump pre-pump A to feed the boiler, after completing the boiler ignition, the auxiliary steam impulse a small steam turbine B, when the pressure of the steam drum reaches 133 MPa, continue to use the B steam pump Boiler replenishment As the drum pressure increases, the steam drum water level is controlled by slowly adjusting the outlet valve of the steam pump and the speed of the steam pump;
2 After the steam parameters are met, the steam turbine will be flushed. Table 3 shows the relevant operating parameters in the process of turbine revolution, grid connection and low load.
3 When the load rises to more than 120MW, start another small turbine A (the steam pump outlet valve is fully closed and the recirculation valve is fully opened) with four pumps. At this time, four pumping to the small steam turbine A steam inlet and pump output parameters such as Table 4 Table 4 Parameters of inlet and outlet pumping parameters of four steam turbines to small turbine A Load four to small steam turbine A inlet steam pressure/M Small steam turbine A Low pressure throttle opening A steam pump A Speed ​​steam pump A outlet pressure/M steam pump A After the outlet flow 4 load rises to 246 MW, the A steam pump is incorporated into the operation. At this time, the B steam turbine steam source is still auxiliary steam. When pumping, the parameters are as shown in Table 5. Table 5 Load is 246 MW and the parameter when pumping The steam pump name Steam inlet pressure MPa Small steam turbine Low pressure throttle opening Valve steam pump speed / (rmin-1) Steam pump outlet pressure M/Pa Steam pump outlet flow / A steam pump group B steam pump unit 5 In order to ensure the safe and stable operation of the unit in the process of starting without electric pump, in the process of lifting the load, the small steam turbine A steam intake is used for four pumping, the small steam turbine B steam source is auxiliary steam supply And cold and then steam spare. When the load is 600MW, the steam pump B can still operate with the auxiliary steam, the auxiliary steam pressure is 083MPa, and the valve opening is 435%. Table 6 shows the operating parameters of the two steam pumps when the load is 600MW: Table 6600MW load when the steam pump Operating Parameters Steam Pump Name Steam Inlet Pressure Low Steam Turbine Low Pressure Door Opening Pump Speed ​​/ (rmin-1) Steam Pump Outlet Pressure M/Pa Steam Pump Outlet Flow / A Steam Pump Group B Steam Pump Set 5 Conclusion Actual Operation Status : Unit 6 was forced to use a cold pump without electric pump due to a fault in the electric pump.
How much of the load of the 1st steam-carrying belt is the key to smooth start-up.
Because the steam turbine diameter for auxiliary steam turbines for small turbines is set to 2 and the auxiliary steam for 4 units of Jiaxing Power Plant Phase 2 is connected through auxiliary steam turbines, the parameters and supply of auxiliary steam can be ensured. It is safe and reliable to start the steam pump. However, the auxiliary steam of No. 34 unit is supplied by four pumps, while the auxiliary steam of No. 5 unit is a cold reheater. Therefore, it is difficult for four auxiliary steam engines to operate in parallel. When designing, the auxiliary steam source of each unit should preferably be the same.
3 Since the initial stage of start-up, the use of steam pumps to regulate the water level is not as flexible as the use of electric pumps, and the amount of work required to control the water level of the drum is large. This plan regulates the water level of the steam drum by means of full-opening of the steam pump recirculation valve, adjusting the valve opening of the steam pump outlet and the speed of the steam pump, and the boiler row and row control valves. In addition, if the original design is to place the electric pump outlet bypass valve at the economizer inlet electric valve, the use of a steam pump to start the drum water level is easier to control, which increases the safety and reliability of the steam pump startup.
4 Power Plant Newly built units If the number of running units is large, the system design for starting the steam pump can be considered. This not only guarantees the safety and reliability of the start-up of the unit, but also saves a large amount of plant power used by the start of the electric pump. This is an energy saving measure of the power plant.
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