0 Overview With the strengthening of national energy-saving emission reduction efforts, various thermal power generation companies are gradually increasing their investment in energy conservation and emission reduction. Taking into account that the unit needs to participate in the peak shaving of the power grid, and it takes a long time to operate under low load, most newly-built power plant condensate pumps use variable frequency control to reduce the power consumption of the power plant. For power plants with multiple condensate pumps, in addition to the use of variable frequency control, a single pump can be safely operated within a wider load range. The maximum use of condensate pumps will play an important role in power plant energy saving. Taking a 1000 MW power plant as an example, when the unit load is 500~700 MW, the condensate system is changed from dual pump operation to single pump operation. The energy saving effect is significant. 00. The power plant condensate pump is a NLT400-500X5S vertical five-stage centrifugal pump. With 3x50% condensate pump. Normally, two units are running and one is standby. When any pump fails, the standby pump is automatically put into operation. When the unit load is 矣50%, a single condensate pump runs. An electric vacuum gate valve and a filter screen are arranged on the inlet pipe of the condensate pump, a check valve and an adjustable electric gate valve are arranged on the outlet pipe, and the electric valve of the import and export is interlocked with the condensate pump to prevent the condensate pump from operating when the import and export valve is closed.
1 The maximum output performance test of single congealer according to the design heat balance diagram, the rated load condensate flow is 1847t/h, and the high-pressure back pressure condition rated load condensate flow is 2042t/h. Calculated according to the condensate pump maximum operating point 1500t/h , Under the normal back pressure can bring 80% of the rated load, high back pressure conditions with 73% of the rated load of 0.60%, 5%, 0% rated load test, such as 70% load when the condensate flow rate is less than 1400t/h, try to increase the load until the condensate flow reaches 1400t/h, and the maximum condensate flow does not exceed 1400t/h13. According to the test result, a single condensate pump can carry a load to 700MW. The parameters of the condensate system are normal. stable.
-), Male, Yi County, Liaoning Province, graduated from the Dongbei Electric Power Institute, a dynamic professional, bachelor, engineer, engaged in power plant turbine operation technology management.
When the unit load is 500~700MW, a single condensate pump operates in the condensate system and the energy saving effect is significant.
2 Analysis of operation status of single condensate pump 2.1 Operation status of single condensate pump under load of 500~700 MW From the actual operation condition, under the influence of factors such as faster unit load rate and fluctuation of deaerator water supply control, etc., When the unit load is greater than 630MW, the condensate flow will fluctuate around 1400t/h, which can easily cause the condensate flow to be greater than 1420t/h, delay 5s, and make the standby condensate pump start. Due to the fluctuation of about 4% of the deaerator upper water control valve, the flow and pressure of the condensate jellyfish tube will fluctuate. In particular, when the load is around 600 MW, the condensing jelly tube pressure fluctuates at 2.9 MPa, and the ASD frequently alarms, which may easily cause operation. The staff relaxed their alarm.
2.2 Operational adjustment measures The following measures have been taken in response to the problem that a single condensate pump operates when the unit load is 500 ~ 700 MW: the condensate pump load.
When a single condensate pump is running, increasing the low-side opening command directly interlocks and starts a standby condensate pump to ensure low-side desuperheating water flow.
When a single condensate pump is running, a standby condensate pump is directly interlocked to increase the low temperature desuperheating water flow when the turbine is tripped.
When a single condensate pump is running, increase the condensate flow (two simultaneous low delay 5s) to jump the pump.
When a single condensate pump is running, increase the pump inlet filter differential pressure greater than 8kPa alarm.
When a single condensate pump is running, the condensate pump pressure is low and the value of the interlocking standby pump is changed from 2.6 MPa to 2.5 MPa; the alarm setting value is changed from 2.9 MPa to 2.5 MPa. When a single condensate pump is running, the condensate flow is low. The value of the lock standby pump was changed from 1150 t/h to 1420 t/h, and the 5 s delay was increased.
2.3 Energy Saving Analysis of Single Condensate Pump Operation When a 700 MW load is in operation, a single condensate pump operates safely, which is more energy efficient than using two condensate pumps.
In addition, the condensate system recycling call automatically opens at a load of less than 700 MW, maintaining a condensate flow of 1440 t/h. The pump's minimum flow is about 25% of the rated flow, which is about 350 t/h, so the total flow is 700 t/h. Above, the recirculation valve can be closed. Under the premise of ensuring the safety of the condensate pump operation, the opening time of the recirculation can be reduced, and the single pump operation mode and the low-load shutdown recirculation method can be implemented in two-pronged manner to achieve the maximum energy-saving effect.
50%, 55%, 60%, 65%, 70% of the rated load for a single condensate pump test, the economic comparison with the dual-pump operation, re-closed dual pump operation mode as shown in Table 1.
Table 1 Single and dual pumps operating economy comparison load / MW single pump operating power / kW dual pump operating power / kW single pump power saving / kW annual coal savings / t economic value / ten thousand yuan recirculation shut down double pump operating power / kW single pump to save power / kW annual savings / t economic value / million Note: economical daily operation at low load 6h, annual operation 300d, standard coal price 800 yuan / t, low load average load 550 MW calculation .
The single pump operation of the condensate system in ~700 MW has the best energy-saving effect, and it saves about 900 kW of power compared with the double-pump operation, 520 tons of coal per year, and an economic value of about RMB 420,000. The single-pump operation of the condensate system saves about 700kW compared with the double-pump operation of the recirculation valve, saves 425 tons of coal annually, and has an economic value of approximately RMB 340,000.
2.4 Safety Performance Analysis ~ 700MW, the pump thrust bearing temperature decreases as the load decreases, the pump's thrust mainly depends on its own balancing holes on each stage of the impeller, balanced cavity balance, so the pump for the thrust change adaptability is better, the single Pump operation does not constitute a limitation.
The motor coil temperature and radial bearing temperature rise with the increase of the load, but can quickly stabilize to a certain value, so the coil temperature and radial bearing temperature can be maintained within the normal range. In general, the realization of a single pump operation of the condensate system is safe and reliable. The main impact of the single pump operation mode comes from the daily start and stop. Starting and stopping twice a day, the average annual start is about 600 times. Frequent start-stops can affect the life of motors and pumps, and increase certain equipment maintenance costs.
3 Conclusion In summary, the use of multiple condensate pump operation unit, to achieve a single pump safer operation within a wider load range, make full use of the performance of the condensate pump, will play an important role in power plant energy saving. According to the actual operation of a 1000 MW unit, the single pump operation of the condensate system with a load of 500 ~ 700 MW has a better energy saving effect. It saves about RMB 420,000 compared with the double pump operation. The single pump operation of the condensate system is higher than that of the recirculation valve. Turning off dual pump operation saves about 34 million yuan. From a safety point of view, the single pump operation of the condensate system is guaranteed, but frequent start-stops can affect the life of the motor and pump, and increase certain equipment maintenance costs.
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