A method and system for switching steam source of feedwater pump during unit startup phase

Abstract

The present invention provides a method and system for switching the steam source of a feedwater pump during the startup phase of a unit, comprising judging whether the unit is connected to the grid, whether the steam-driven feedwater pump is in operation, and whether the drain valve of the cold re-steam pipeline has reached the maximum opening; if all of them are true, opening the cold re-steam inlet electric door; judging whether the opening of the cold re-steam inlet electric door is greater than a second preset opening; if so, judging whether the pressure of the four pumping units is greater than a first preset pressure, and whether the temperature of the four pumping units is greater than the first four-pump preset temperature; if so, opening the four-pump steam inlet electric door and closing the auxiliary steam inlet electric door; so that when the disturbance is minimized, the auxiliary steam source is switched to the low-pressure steam source to ensure the safety of the steam source of the steam-driven feedwater pump and safe and stable water supply control.

Description

Technical Field

[0001] The present invention relates to the technical field of steam-driven water supply pumps, and in particular to a method and system for switching air sources of water supply pumps during the startup phase of a unit. Background Art

[0002] The steam-driven feedwater pump has a complete high- and low-pressure steam distribution mechanism, and can be switched under high- and low-pressure steam source conditions. The high-pressure steam comes from the cold section of the reheater, and the low-pressure steam comes from the fourth-stage extraction of the main engine. During the startup phase of the unit, an auxiliary steam source is usually used as the starting steam source to flush the steam-driven feedwater pump to start the unit. After the unit is connected to the grid and the pressure of the low- and high-pressure steam sources is normal, the auxiliary steam source is switched to the low-pressure steam source for steam supply, and the high-pressure steam source is used as a hot standby. The entire steam source switching not only increases the operating workload of the operating personnel, but also brings about fluctuations in the feedwater volume caused by disturbances in the steam source parameters due to improper operation. In severe cases, the minimum water inlet flow of the boiler cannot be met instantly, leading to the risk of boiler MFT.

[0003] In view of this, the present application proposes a method and system for switching the air source of the water feed pump during the unit startup phase, so that the auxiliary steam source can be switched to the low-pressure steam source with minimal disturbance to ensure the safety of the steam source of the steam-driven water feed pump and the safe and stable water feed control. Summary of the invention

[0004] The object of the present invention is to provide a method for switching the steam source of a feedwater pump during the startup phase of a unit, wherein the feedwater pump is a steam-driven feedwater pump, and the steam-driven feedwater pump includes a cold re-steam pipeline drain valve, a cold re-inlet steam electric valve, four-pump, four-pump drain valve, an auxiliary steam inlet electric valve and a four-pump steam inlet electric valve, including step 101, judging whether the unit is connected to the grid, whether the steam-driven feedwater pump is in operation, and whether the cold re-steam pipeline drain valve reaches the maximum opening; step 102, if all are yes, then opening the cold re-inlet steam electric valve at a first opening rate; step 103, judging whether the steam temperature behind the cold re-inlet steam electric valve is greater than the first cold re-preset temperature; step 104, if yes, then making the cold re-inlet steam electric valve maintain the current opening for the first preset time; step 105, judging whether the steam temperature behind the cold re-inlet steam electric valve is less than the second cold re-preset temperature; step 106, if yes, then continuing to open the cold re-inlet steam electric valve; step 107, judging the Whether the opening of the cold steam re-inlet electric door exceeds the first preset opening; step 108, if so, open the cold steam re-inlet electric door at a second opening rate; the second opening rate is greater than the first opening rate; step 109, determine whether the opening of the cold steam re-inlet electric door is greater than the second preset opening; step 110, if so, determine whether the pressure of the four pumping is greater than the first preset pressure, and whether the temperature of the four pumping is greater than the first four pumping preset temperature; step 111, if both are yes, determine whether the steam-driven water supply pump is in operation and whether the four-pump drain valve has reached the maximum opening; step 112, if both are yes, close the auxiliary steam inlet electric door at the first closing rate; step 113, determine whether the steam inlet pressure of the steam-driven water supply pump is lower than the pressure of the four pumping and the deviation is less than the preset deviation threshold; step 114, if so, open the four-pump steam inlet electric door at the first opening rate, and close the auxiliary steam inlet electric door at the first closing rate.

[0005] Furthermore, it also includes judging whether the steam inlet temperature of the steam-driven water supply pump is greater than the second cooling preset temperature and whether the water supply amount decreases by the preset water supply amount; if both are true, maintaining the current opening of the four-extraction steam inlet electric door and the auxiliary steam inlet electric door for the first preset time; judging whether the steam inlet temperature of the steam-driven water supply pump after the first preset time is less than the second cooling preset temperature; if so, continuing to open the four-extraction steam inlet electric door and close the auxiliary steam inlet electric door until the four-extraction steam inlet electric door reaches the maximum opening and the auxiliary steam inlet electric door is closed.

[0006] Furthermore, it also includes judging whether the boiler and the steam-driven feed water pump have tripped; if the boiler has tripped but the steam-driven feed water pump has not tripped, closing the four-extraction steam inlet electric door, and opening the auxiliary steam inlet electric door at the first opening rate; after opening the auxiliary steam inlet electric door to the maximum opening, repeating the steps of opening the four-extraction steam inlet electric door and closing the auxiliary steam inlet electric door.

[0007] Furthermore, it also includes closing the four-extraction steam inlet electric door and the auxiliary steam inlet electric door if both the boiler and the steam-driven feed water pump trip; re-operating the steam-driven feed water pump after the shutdown is completed, and opening the auxiliary steam inlet electric door at the first opening rate; after opening the auxiliary steam inlet electric door to the maximum opening, repeating the steps of opening the four-extraction steam inlet electric door and closing the auxiliary steam inlet electric door.

[0008] Furthermore, the first opening rate is 0.1% / s, and the second opening rate is 0.5% / s.

[0009] The object of the present invention is to provide a steam source switching system for a feedwater pump during the startup phase of a unit, wherein the feedwater pump is a steam-driven feedwater pump, and the steam-driven feedwater pump includes a cold re-steam pipeline drain valve, a cold re-inlet steam electric door, four-pump, four-pump drain valve, an auxiliary steam inlet electric door and a four-pump steam inlet electric door, including a first judgment module, a first opening module, a second judgment module, a holding module, a third judgment module, a fourth judgment module, a fifth judgment module, a sixth judgment module, a seventh judgment module, a first closing module, an eighth judgment module and a second opening module; the first judgment module is used to judge whether the unit is connected to the grid, whether the steam-driven feedwater pump is in operation, and whether the cold re-steam pipeline drain valve has reached the maximum opening; the first opening module The module is used to open the cold re-inlet steam electric door at a first opening rate when the unit is connected to the grid, the steam-driven feedwater pump is in operation, and the cold re-inlet steam pipeline drain valve reaches the maximum opening; the first opening module is also used to continue to open the cold re-inlet steam electric door when the steam temperature after the cold re-inlet steam electric door is less than the second cold re-preset temperature; the first opening module is also used to open the cold re-inlet steam electric door at a second opening rate when the opening of the cold re-inlet steam electric door exceeds the first preset opening; the second opening rate is greater than the first opening rate; the second judgment module is used to judge whether the steam temperature after the cold re-inlet steam electric door is greater than the first cold re-preset temperature; the holding module is used when the When the steam temperature behind the cold steam re-inlet electric door is greater than the first cold re-preset temperature, the cold steam re-inlet electric door is kept at the current opening for the first preset time; the third judgment module is used to judge whether the steam temperature behind the cold steam re-inlet electric door is less than the second cold re-preset temperature; the fourth judgment module is used to judge whether the opening of the cold steam re-inlet electric door exceeds the first preset opening; the fifth judgment module is used to judge whether the opening of the cold steam re-inlet electric door is greater than the second preset opening; the sixth judgment module is used to judge whether the pressure of the four extractions is greater than the first preset pressure and whether the temperature of the four extractions is greater than the first four extraction preset temperature when the opening of the cold steam re-inlet electric door is greater than the second preset opening; the seventh judgment module Used to judge whether the steam-driven feedwater pump is in operation and whether the drain valve of the four pumps has reached the maximum opening when the pressure of the four pumps is greater than the first preset pressure and the temperature of the four pumps is greater than the first preset temperature of the four pumps; the first closing module is used to close the auxiliary steam inlet electric door at a first closing rate when the steam-driven feedwater pump is in operation and the drain valve of the four pumps has reached the maximum opening; the first closing module is also used to close the auxiliary steam inlet electric door at a first closing rate when the steam inlet pressure of the steam-driven feedwater pump is lower than the pressure of the four pumps and the deviation is less than the preset deviation threshold; the eighth judgment module is used to judge whether the steam inlet pressure of the steam-driven feedwater pump is lower than the pressure of the four pumps and the deviation is less than the preset deviation threshold;The second opening module is used to open the four-pump steam inlet electric door at a first opening rate when the steam inlet pressure of the steam-driven feedwater pump is lower than the pressure of the four-pump and the deviation is less than a preset deviation threshold.

[0010] Furthermore, it also includes a steam inlet monitoring module, which is used to determine whether the steam inlet temperature of the steam-driven water supply pump is greater than the second cooling preset temperature and whether the water supply amount decreases by the preset water supply amount; if both are true, the four-extraction steam inlet electric door and the auxiliary steam inlet electric door are maintained at the current opening for the first preset time; determine whether the steam inlet temperature of the steam-driven water supply pump after the first preset time is less than the second cooling preset temperature; if so, continue to open the four-extraction steam inlet electric door and close the auxiliary steam inlet electric door until the four-extraction steam inlet electric door reaches the maximum opening and the auxiliary steam inlet electric door is closed.

[0011] Furthermore, it also includes a trip monitoring module, which is used to determine whether the boiler and the steam-driven feed water pump have tripped; if the boiler trips and the steam-driven feed water pump has not tripped, the four-extraction steam inlet electric door is closed, and the auxiliary steam inlet electric door is opened at the first opening rate; after opening the auxiliary steam inlet electric door to the maximum opening, the four-extraction steam inlet electric door is repeatedly opened and the auxiliary steam inlet electric door is closed.

[0012] Furthermore, the trip monitoring module is also used to close the four-extraction steam inlet electric door and the auxiliary steam inlet electric door if both the boiler and the steam-driven feed water pump trip; after the shutdown is completed, the steam-driven feed water pump is restarted, and the auxiliary steam inlet electric door is opened at the first opening rate; after opening the auxiliary steam inlet electric door to the maximum opening, the four-extraction steam inlet electric door and the auxiliary steam inlet electric door are repeatedly opened and closed.

[0013] Furthermore, the first opening rate is 0.1% / s, and the second opening rate is 0.5% / s.

[0014] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0015] Some embodiments of the present application use auxiliary steam to start the pneumatic water supply pump group instead of the electric pump during the unit startup, which can reduce the power consumption of the plant, avoid the phenomenon of waiting for the small machine after the main machine is started, speed up the startup speed, and thus bring direct economic benefits to the power plant.

[0016] The present application proposes a method and system for switching the steam source of a water supply pump during the startup phase of a unit, which can realize fast, flexible and safe switching of the steam source under conditions such as unit tripping, load shedding and start-stop, shorten the unit recovery time, improve the safety and economy of the operation of the unit water supply system, and ensure the reliability of the operation of the entire unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 An exemplary flow chart of a method for switching a steam source of a feedwater pump during a unit startup phase provided in some embodiments of the present invention;

[0018] Figure 2 An exemplary module diagram of a feedwater pump steam source switching system during the unit startup phase is provided for some embodiments of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0020] The feed water pump can be a steam-driven feed water pump, which can at least include a cold re-steam pipeline drain valve, a cold re-steam inlet electric valve, four-pumping, a four-pumping drain valve, an auxiliary steam inlet electric valve and a four-pumping steam inlet electric valve.

[0021] Figure 1 This is an exemplary flow chart of a method for switching a steam source of a feedwater pump during a unit startup phase provided in some embodiments of the present invention. In some embodiments, process 100 may be executed by system 200.

[0022] like Figure 1 The process 200 shown includes the following steps:

[0023] Step 101 is to determine whether the unit is connected to the grid, whether the steam-driven feedwater pump is in operation, and whether the drain valve of the cold re-steam pipeline has reached the maximum opening. In some embodiments, step 101 can be executed by the first determination module 201.

[0024] The unit may refer to a generator unit. The maximum opening may refer to a valve being fully open, for example, 100%. The unit being connected to the grid may refer to the unit being able to generate electricity.

[0025] Step 102 , if both are true, then open the cold re-inlet steam electric door at a first opening rate. In some embodiments, step 102 may be performed by the first opening module 202 .

[0026] The first opening rate may refer to a rate at which the cold re-intake steam electric door or the four-extraction steam inlet electric door begins to be opened. In some embodiments, the first opening rate may be 0.1% / s.

[0027] If there is a no, then step 101 is repeated.

[0028] Step 103 , determining whether the steam temperature after the cold re-inlet steam electric door is greater than the first cold re-preset temperature. In some embodiments, step 103 may be executed by the second determination module 203 .

[0029] The first cold re-preset temperature may refer to the minimum value of the steam temperature of the preheated steam pipeline. In some embodiments, the first cold re-preset temperature may be 0.5° C. / s.

[0030] Step 104 , if yes, then keep the cold re-inlet steam electric door at the current opening for a first preset time. In some embodiments, step 104 may be performed by the maintaining module 204 .

[0031] The first preset time may refer to the time for preheating the pipeline. In some embodiments, the first preset time may be 5 minutes to fully preheat the steam pipeline.

[0032] If not, repeat step 103.

[0033] Step 105 , determining whether the steam temperature after the cold re-inlet steam electric door is less than the second cold re-preset temperature. In some embodiments, step 105 may be executed by the third determination module 205 .

[0034] The second cold re-preset temperature may refer to a preset maximum value of the steam temperature after the cold re-inlet steam electric door is opened. In some embodiments, the second cold re-preset temperature may be 0.2° C. / s.

[0035] Step 106, if yes, continue to open the cold re-inlet steam electric door. In some embodiments, step 106 can be performed by. In some embodiments, step 106 can be performed by the first opening module 202.

[0036] If not, step 105 is repeated.

[0037] Step 107 , determining whether the opening of the cold re-inlet steam electric door exceeds a first preset opening. In some embodiments, step 107 may be executed by the fourth determination module 206 .

[0038] The first preset opening degree may refer to a preset minimum opening degree for increasing the opening rate of the cold re-intake electric door. In some embodiments, the first preset opening degree may be 50% of the maximum opening degree.

[0039] Step 108 , if yes, then open the cold re-inlet steam electric door at a second opening rate; the second opening rate is greater than the first opening rate. In some embodiments, step 108 may be performed by the first opening module 202 .

[0040] The second opening rate may refer to the rate of opening the cold re-inlet electric door when the opening degree of the cold re-inlet electric door reaches a certain condition. In some embodiments, the second opening rate may be 0.5% / s.

[0041] If not, step 107 is repeated.

[0042] Step 109 , determining whether the opening of the cold re-inlet steam electric door is greater than a second preset opening. In some embodiments, step 109 may be executed by the fifth determination module 207 .

[0043] The second preset opening may refer to a preset opening of the cold re-inlet electric door when the auxiliary steam inlet electric door can be closed. In some embodiments, the second preset opening may be 90% of the maximum opening.

[0044] Step 110 , if yes, then determine whether the pressure of the four pumps is greater than the first preset pressure, and whether the temperature of the four pumps is greater than the first preset temperature of the four pumps. In some embodiments, step 110 may be performed by the sixth determination module 208 .

[0045] The first preset pressure may refer to the preset minimum pressure of the four-stage extraction when the auxiliary steam inlet electric door is closed. In some embodiments, the first preset pressure may be 0.25 MPa. The first four-stage extraction preset temperature may refer to the minimum temperature of the four-stage extraction when the auxiliary steam inlet electric door is closed. In some embodiments, the first four-stage extraction preset temperature may be 200°C.

[0046] If not, step 109 is repeated.

[0047] Step 111 , if both are true, then determine whether the steam-driven water supply pump is in operation and whether the four-pump drain valve has reached the maximum opening. In some embodiments, step 111 may be executed by the seventh determination module 209 .

[0048] The maximum opening may refer to the opening of the four-pump drain valve reaching 100%.

[0049] If there is a no, step 110 is repeated.

[0050] Step 112 , if both are true, close the auxiliary steam inlet electric door at a first closing rate. In some embodiments, step 112 may be performed by the first closing module 210 .

[0051] The first closing rate may refer to a rate of closing the auxiliary steam inlet electric door. In some embodiments, the first closing rate may be 0.1% / s.

[0052] If there is a no, then step 111 is repeated.

[0053] Step 113 , determining whether the steam inlet pressure of the steam-driven feedwater pump is lower than the pressure of the fourth pumping unit and the deviation is smaller than a preset deviation threshold. In some embodiments, step 113 may be executed by the eighth determination module 211 .

[0054] The preset deviation threshold may refer to a preset maximum difference between the steam inlet pressure of the steam-driven feedwater pump and the pressure of the four-pump pump. In some embodiments, the preset deviation threshold may be 0.1 MPa.

[0055] Step 114 , if yes, then open the four-extraction steam inlet electric door at a first opening rate, and close the auxiliary steam inlet electric door at a first closing rate. In some embodiments, step 114 may be performed by the second opening module 212 and the first closing module 210 .

[0056] If not, step 113 is repeated.

[0057] In some embodiments, it also includes judging whether the steam inlet temperature of the steam-driven water pump is greater than the second cold preset temperature and whether the water supply volume has decreased by the preset water supply volume; if both are true, the four-extraction steam inlet electric door and the auxiliary steam inlet electric door are maintained at the current opening for the first preset time; if not, it is repeated to judge whether the steam inlet temperature of the steam-driven water pump is greater than the second cold preset temperature and whether the water supply volume has decreased by the preset water supply volume. It is judged whether the steam inlet temperature of the steam-driven water pump after the first preset time is less than the second cold preset temperature; if so, the four-extraction steam inlet electric door is continued to be opened and the auxiliary steam inlet electric door is closed until the four-extraction steam inlet electric door reaches the maximum opening and the auxiliary steam inlet electric door is closed; if not, it is repeated to judge whether the steam inlet temperature of the steam-driven water pump after the first preset time is less than the second cold preset temperature. The preset water supply volume may refer to the preset maximum value of the allowed water supply volume to decrease. In some embodiments, the preset water supply volume may refer to 50t / h.

[0058] In some embodiments, it also includes determining whether the boiler and the steam-driven feed water pump have tripped; if the boiler trips but the steam-driven feed water pump has not tripped, closing the four-extraction steam inlet electric door, and opening the auxiliary steam inlet electric door at a first opening rate; after opening the auxiliary steam inlet electric door to the maximum opening, repeating the steps of opening the four-extraction steam inlet electric door and closing the auxiliary steam inlet electric door.

[0059] In some embodiments, it also includes closing the four-extraction steam inlet electric door and the auxiliary steam inlet electric door if both the boiler and the steam-driven feed water pump trip; re-operating the steam-driven feed water pump after the shutdown is completed, and opening the auxiliary steam inlet electric door at a first opening rate; after opening the auxiliary steam inlet electric door to the maximum opening, repeating the steps of opening the four-extraction steam inlet electric door and closing the auxiliary steam inlet electric door.

[0060] Figure 2 This is an exemplary module diagram of a feedwater pump steam source switching system during the unit startup phase provided by some embodiments of the present invention. Figure 2 As shown, the system 200 includes a first judgment module 201, a first opening module 202, a second judgment module 203, a holding module 204, a third judgment module 205, a fourth judgment module 206, a fifth judgment module 207, a sixth judgment module 208, a seventh judgment module 209, a first closing module 210, an eighth judgment module 211, and a second opening module 212.

[0061] The first judgment module 201 is used to judge whether the unit is connected to the grid, whether the steam-driven feedwater pump is in operation, and whether the drain valve of the cold re-steam pipeline has reached the maximum opening.

[0062] The first opening module 202 is used to open the cold re-inlet steam electric door at a first opening rate when the unit is connected to the grid, the steam-driven feedwater pump is in operation, and the cold re-inlet steam pipe drain valve reaches the maximum opening; the first opening module is also used to continue to open the cold re-inlet steam electric door when the steam temperature after the cold re-inlet steam electric door is less than the second cold re-preset temperature; the first opening module is also used to open the cold re-inlet steam electric door at a second opening rate when the opening of the cold re-inlet steam electric door exceeds the first preset opening; the second opening rate is greater than the first opening rate.

[0063] The second judgment module 203 is used to judge whether the steam temperature after the cold re-inlet steam electric door is greater than the first cold re-inlet preset temperature.

[0064] The maintaining module 204 is used for maintaining the current opening of the cold re-inlet steam electric door for a first preset time when the steam temperature after the cold re-inlet steam electric door is greater than a first cold re-inlet preset temperature.

[0065] The third judgment module 205 is used to judge whether the steam temperature after the cold re-inlet steam electric door is less than the second cold re-inlet preset temperature.

[0066] The fourth judgment module 206 is used to judge whether the opening of the cold re-intake steam electric door exceeds a first preset opening.

[0067] The fifth judgment module 207 is used to judge whether the opening of the cold re-intake steam electric door is greater than a second preset opening.

[0068] The sixth judgment module 208 is used to judge whether the pressure of the four extractions is greater than the first preset pressure and whether the temperature of the four extractions is greater than the first four extraction preset temperature when the opening of the cold re-inlet steam electric door is greater than the second preset opening.

[0069] The seventh judgment module 209 is used to judge whether the steam-driven water supply pump is in operation and whether the four-pump drain valve reaches the maximum opening when the pressure of the four-pump is greater than the first preset pressure and the temperature of the four-pump is greater than the first four-pump preset temperature.

[0070] The first closing module 210 is used to close the auxiliary steam inlet electric door at a first closing rate when the steam-driven feedwater pump is in operation and the four-pump drain valve reaches the maximum opening; the first closing module is also used to close the auxiliary steam inlet electric door at a first closing rate when the steam inlet pressure of the steam-driven feedwater pump is lower than the four-pump pressure and the deviation is less than a preset deviation threshold.

[0071] The eighth judgment module 211 is used to judge whether the steam inlet pressure of the steam-driven feedwater pump is lower than the pressure of the four pumping units and the deviation is less than a preset deviation threshold.

[0072] The second opening module 212 is used to open the four-extraction steam inlet electric door at a first opening rate when the steam inlet pressure of the steam-driven feedwater pump is lower than the pressure of the four-extraction and the deviation is less than a preset deviation threshold.

[0073] In some embodiments, the system 200 may also include a steam inlet monitoring module, which is used to determine whether the steam inlet temperature of the steam-driven feed water pump is greater than the second cooling preset temperature and whether the water supply volume has decreased by a preset water supply volume; if both are true, the four-extraction steam inlet electric door and the auxiliary steam inlet electric door are maintained at the current opening for the first preset time; determine whether the steam inlet temperature of the steam-driven feed water pump after the first preset time is less than the second cooling preset temperature; if so, continue to open the four-extraction steam inlet electric door and close the auxiliary steam inlet electric door until the four-extraction steam inlet electric door reaches the maximum opening and the auxiliary steam inlet electric door is closed.

[0074] In some embodiments, the system 200 may further include a trip monitoring module, which is used to determine whether the boiler and the steam-driven feed water pump have tripped; if the boiler trips and the steam-driven feed water pump has not tripped, the four-extraction steam inlet electric door is closed, and the auxiliary steam inlet electric door is opened at the first opening rate; after opening the auxiliary steam inlet electric door to the maximum opening, the four-extraction steam inlet electric door is repeatedly opened and the auxiliary steam inlet electric door is closed.

[0075] In some embodiments, the trip monitoring module is also used to close the four-extraction steam inlet electric door and the auxiliary steam inlet electric door if both the boiler and the steam-driven feed water pump trip; re-operate the steam-driven feed water pump after the shutdown is completed, and open the auxiliary steam inlet electric door at the first opening rate; after opening the auxiliary steam inlet electric door to the maximum opening, repeatedly open the four-extraction steam inlet electric door and close the auxiliary steam inlet electric door.

[0076] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for switching the steam source of a feedwater pump during the unit startup phase, characterized in that: The feed water pump is a steam-driven feed water pump, which includes a cold re-steam pipeline drain valve, a cold re-inlet steam electric valve, a four-pump, a four-pump drain valve, an auxiliary steam inlet electric valve and a four-pump steam inlet electric valve. Step 101, determining whether the unit is connected to the grid, whether the steam-driven feedwater pump is in operation, and whether the drain valve of the cold re-steam pipeline has reached the maximum opening; Step 102, if both are true, then open the cold re-inlet steam electric door at a first opening rate; Step 103, determine whether the steam temperature after the cold re-inlet steam electric door is greater than the first cold re-inlet preset temperature; Step 104, if yes, keeping the cold re-inlet steam electric door at the current opening for a first preset time; Step 105, determining whether the steam temperature after the cold re-inlet steam electric door is less than the second cold re-preset temperature; Step 106, if yes, continue to open the cold steam re-inlet electric door; Step 107, determining whether the opening of the cold steam re-inlet electric door exceeds a first preset opening; Step 108, if yes, opening the cold steam re-inlet electric door at a second opening rate; the second opening rate is greater than the first opening rate; Step 109, determining whether the opening of the cold re-inlet steam electric door is greater than the second preset opening; Step 110, if yes, determining whether the pressure of the four pumping units is greater than the first preset pressure, and whether the temperature of the four pumping units is greater than the first four pumping unit preset temperature; Step 111, if both are true, then determine whether the steam-driven water supply pump is in operation and whether the four-pump drain valve has reached the maximum opening; Step 112, if both are true, close the auxiliary steam inlet electric door at a first closing rate; Step 113, determining whether the steam inlet pressure of the steam-driven feedwater pump is lower than the pressure of the four-pump and the deviation is less than a preset deviation threshold; Step 114: If yes, then open the four-extraction steam inlet electric door at a first opening rate, and close the auxiliary steam inlet electric door at a first closing rate.

2. The method for switching the steam source of a feedwater pump during the unit startup phase according to claim 1, characterized in that: Also includes Determine whether the steam inlet temperature of the steam-driven feedwater pump is greater than the preset temperature of the second cooling unit and whether the feedwater amount decreases to a preset feedwater amount; If both are true, the four-extraction steam inlet electric door and the auxiliary steam inlet electric door are kept at the current opening for the first preset time; Determining whether the steam inlet temperature of the steam-driven feedwater pump after the first preset time is less than the second cooling preset temperature; If so, continue to open the four-extraction steam inlet electric door and close the auxiliary steam inlet electric door until the four-extraction steam inlet electric door reaches the maximum opening and the auxiliary steam inlet electric door is closed.

3. The method for switching the steam source of a feedwater pump during the unit startup phase according to claim 1, characterized in that: Also includes Determine whether the boiler and the steam-driven feedwater pump have tripped; If the boiler trips but the steam-driven feedwater pump does not trip, the four-extraction steam inlet electric door is closed, and the auxiliary steam inlet electric door is opened at the first opening rate; After the auxiliary steam inlet electric door is opened to the maximum opening, the steps of opening the four-extraction steam inlet electric door and closing the auxiliary steam inlet electric door are repeated.

4. The method for switching the steam source of a feedwater pump during the unit startup phase according to claim 3, characterized in that: Also includes If the boiler and the steam-driven feedwater pump are both tripped, the four-extraction steam inlet electric door and the auxiliary steam inlet electric door are closed; After the shutdown is completed, the steam-driven water supply pump is restarted, and the auxiliary steam inlet electric door is opened at the first opening rate; After the auxiliary steam inlet electric door is opened to the maximum opening, the steps of opening the four-extraction steam inlet electric door and closing the auxiliary steam inlet electric door are repeated.

5. The method for switching the steam source of a feedwater pump during the unit startup phase according to claim 1, characterized in that: The first opening rate is 0.1% / s, and the second opening rate is 0.5% / s.

6. A feedwater pump steam source switching system during the unit startup phase, characterized in that: The feed water pump is a steam-driven feed water pump, which includes a cold re-steam pipeline drain valve, a cold re-inlet steam electric door, four-pump, four-pump drain valve, auxiliary steam inlet electric door and four-pump steam inlet electric door, including a first judgment module, a first opening module, a second judgment module, a holding module, a third judgment module, a fourth judgment module, a fifth judgment module, a sixth judgment module, a seventh judgment module, a first closing module, an eighth judgment module and a second opening module; the first judgment module is used to judge whether the unit is connected to the grid, whether the steam-driven feed water pump is in operation, and whether the cold re-steam pipeline drain valve has reached the maximum opening; The first opening module is used to open the cold re-inlet steam electric door at a first opening rate when the unit is connected to the grid, the steam-driven feedwater pump is in operation, and the cold re-inlet steam pipe drain valve reaches the maximum opening; the first opening module is also used to continue to open the cold re-inlet steam electric door when the steam temperature after the cold re-inlet steam electric door is less than the second cold re-preset temperature; the first opening module is also used to open the cold re-inlet steam electric door at a second opening rate when the opening of the cold re-inlet steam electric door exceeds the first preset opening; the second opening rate is greater than the first opening rate; The second judgment module is used to judge whether the steam temperature after the cold re-inlet steam electric door is greater than the first cold re-inlet preset temperature; The holding module is used to keep the cold re-inlet steam electric door at the current opening for a first preset time when the steam temperature after the cold re-inlet steam electric door is greater than the first cold re-inlet preset temperature; The third judgment module is used to judge whether the steam temperature after the cold re-inlet steam electric door is less than the second cold re-preset temperature; The fourth judgment module is used to judge whether the opening of the cold re-inlet steam electric door exceeds a first preset opening; The fifth judgment module is used to judge whether the opening of the cold re-inlet steam electric door is greater than a second preset opening; The sixth judgment module is used for judging whether the pressure of the four-pump is greater than the first preset pressure and whether the temperature of the four-pump is greater than the first four-pump preset temperature when the opening of the cold re-inlet steam electric door is greater than the second preset opening; The seventh judgment module is used to judge whether the steam-driven water supply pump is in operation and whether the drain valve of the four pumps reaches the maximum opening when the pressure of the four pumps is greater than the first preset pressure and the temperature of the four pumps is greater than the first four pumps preset temperature; The first closing module is used to close the auxiliary steam inlet electric door at a first closing rate when the steam-driven feedwater pump is in operation and the four-pump drain valve reaches the maximum opening; the first closing module is also used to close the auxiliary steam inlet electric door at a first closing rate when the steam inlet pressure of the steam-driven feedwater pump is lower than the pressure of the four-pump and the deviation is less than a preset deviation threshold; The eighth judgment module is used to judge whether the steam inlet pressure of the steam-driven feedwater pump is lower than the pressure of the four pumps and the deviation is less than a preset deviation threshold; The second opening module is used to open the four-extraction steam inlet electric door at a first opening rate when the steam inlet pressure of the steam-driven water supply pump is lower than the pressure of the four-extraction and the deviation is less than a preset deviation threshold.

7. The feedwater pump steam source switching system during the unit startup phase according to claim 6, characterized in that: It also includes a steam inlet monitoring module. The steam inlet monitoring module is used to determine whether the steam inlet temperature of the steam-driven feedwater pump is greater than the second cooling preset temperature and whether the feedwater amount decreases to a preset feedwater amount; If both are true, the four-extraction steam inlet electric door and the auxiliary steam inlet electric door are kept at the current opening for the first preset time; Determine whether the steam inlet temperature of the steam-driven water supply pump after the first preset time is lower than the second cooling preset temperature; if so, continue to open the four-extraction steam inlet electric door and close the auxiliary steam inlet electric door until the four-extraction steam inlet electric door reaches the maximum opening and the auxiliary steam inlet electric door is closed.

8. The feedwater pump steam source switching system during the unit startup phase according to claim 6, characterized in that: Also includes trip monitoring module, The trip monitoring module is used to determine whether the boiler and the steam-driven feed water pump have tripped; if the boiler trips and the steam-driven feed water pump has not tripped, the four-extraction steam inlet electric door is closed, and the auxiliary steam inlet electric door is opened at the first opening rate; after opening the auxiliary steam inlet electric door to the maximum opening, the four-extraction steam inlet electric door is repeatedly opened and the auxiliary steam inlet electric door is closed.

9. The feedwater pump steam source switching system during the unit startup phase according to claim 8, characterized in that: The trip monitoring module is also used to close the four-extraction steam inlet electric door and the auxiliary steam inlet electric door if both the boiler and the steam-driven feed water pump trip; re-operate the steam-driven feed water pump after the shutdown is completed, and open the auxiliary steam inlet electric door at the first opening rate; after opening the auxiliary steam inlet electric door to the maximum opening, repeatedly open the four-extraction steam inlet electric door and close the auxiliary steam inlet electric door.

10. The feedwater pump steam source switching system during the unit startup phase according to claim 6, characterized in that: The first opening rate is 0.1% / s, and the second opening rate is 0.5% / s.

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