A blowdown control device and method for a double reheat unit

Abstract

This invention discloses a blowdown control device and method for a double reheat unit. The device includes a superheater, with its inlet connected to the separator outlet. The superheater outlet is connected to the main steam valve of the ultra-high pressure cylinder, which is connected to a superheater temporary control valve. The outlet of the superheater temporary control valve is sequentially connected to a superheater target plate, a pellet collector, and a first reheat temporary control valve. A second reheat temporary control valve is connected between the pellet collector and the first reheat temporary control valve. The first reheat temporary control valve is connected to a pipe on the primary reheater side, and the primary reheater outlet is connected to the first reheater target plate, which is connected to a silencer. The second reheat temporary control valve is connected to the high-pressure main steam valve. The high-pressure cylinder main steam valve is connected to the inlet pipe of the secondary reheater, and the secondary reheater is connected to the intermediate-pressure main steam valve. The intermediate-pressure cylinder main steam valve is connected to the second reheater target plate, which is connected to a silencer. This invention satisfies the blowdown coefficient requirements while ensuring that each heating surface is fully heated. During shutdown cooling, each heating surface can effectively remove oxide scale, improving the blowdown effect.

Description

Technical Field

[0001] This invention relates to the field of blowdown in reheat units, specifically to a blowdown control device for reheat units, and also to a control method for blowdown in reheat units. Background Technology

[0002] With the current goals of carbon peaking and carbon neutrality, newly built thermal power plants are increasingly demanding higher unit efficiency. Simultaneously, advancements in equipment manufacturing and related materials technologies have made the development of units with higher parameters an inevitable trend. According to the Rankine cycle, higher parameters generally lead to higher unit efficiency, and double reheat units have a more significant effect on improving unit efficiency. Therefore, a large number of double reheat units have been built in recent years.

[0003] From a system perspective, double reheat units are more complex than single reheat units, with higher pressure parameters. Furthermore, due to the reduced volume of the boiler water-cooled walls and superheaters compared to the unit's capacity, the heat capacity is also reduced. Therefore, units using conventional blowdown arrangements often struggle to achieve the required blowdown coefficient. Some units, in an attempt to meet the blowdown coefficient requirements, have opted to increase the blowdown pressure to 11.5 MPa, posing significant safety risks during the blowdown process.

[0004] Currently, the control methods for blow-off in primary reheat units are relatively standardized, but the control of blow-off processes in secondary reheat units is not yet perfect. On the one hand, the secondary reheat unit system is complex, and there are many ways to arrange temporary piping for the blow-off coefficient. The blow-off method can be divided into single-stage blow-off, two-stage blow-off, three-stage blow-off, etc. At the same time, the temporary control valve can be placed at the superheater outlet or the primary reheater outlet, which makes it difficult to achieve a relatively unified standard for the blow-off control method and brings greater uncertainty to the blow-off process control. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a blowdown control device and method for a secondary reheat unit, so as to solve the technical problems of high blowdown frequency, high shutdown frequency, low blowdown coefficient, and high safety risk in the current blowdown process of secondary reheat units.

[0006] The technical solution adopted in this invention is a blowdown control device for a double reheat unit, including a superheater. The superheater inlet is connected to the separator outlet through a pipeline, and the superheater outlet is connected to the main steam valve of the ultra-high pressure cylinder through a pipeline. The main steam valve of the ultra-high pressure cylinder is connected to the superheater temporary control valve through a pipeline. The outlet of the superheater temporary control valve is connected to the superheater target plate, the particle collector and the first reheat temporary control valve in sequence through a pipeline. The particle collector and the first reheat temporary control valve are connected to the second reheat temporary control valve through a pipeline.

[0007] The reheat valve is connected to the reheater side pipe via a pipeline, the reheater outlet is connected to the reheat target plate via a pipeline, and the reheat target plate is connected to the silencer via a pipeline.

[0008] The secondary reheat control valve is connected to the high-pressure main steam valve via a pipeline. The high-pressure cylinder main steam valve is connected to the inlet pipe of the secondary reheater. The secondary reheater is connected to the intermediate-pressure main steam valve. The intermediate-pressure cylinder main steam valve is connected to the secondary reheat target plate via a pipeline. The secondary reheat target plate is connected to the silencer via a pipeline.

[0009] A control method for blowdown in a double reheat unit, comprising three stages, with each stage controlled as follows:

[0010] Phase 1:

[0011] Superheater purging:

[0012] The separator outlet pressure reaches the blow-off pressure. When the superheater is in operation, the superheater control valve is opened for steam blowing. The steam passes through the superheater control valve and the granulator, then splits into two streams. One stream passes through the primary reheater control valve, the primary reheater, and the silencer before exiting; the other stream passes through the secondary reheater control valve, the secondary reheater, and the silencer before exiting. The superheater control valve is closed when the superheater blowing coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, until the superheater control valve is completely closed. The separator outlet pressure must meet the requirement that the superheater blowing coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. Second-rate;

[0013] in:

[0014] ;

[0015] ;

[0016] ;

[0017] First reheater purge:

[0018] Close the secondary emergency control valve. At this time, the superheat emergency control valve closes, the primary emergency control valve opens, and the separator outlet pressure reaches the blow-off pressure. When the superheater control valve is opened, steam passes through the superheater control valve and the granulator, then through the primary reheater control valve, the primary reheater, and the silencer before being discharged. When the primary reheater blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve is closed until it is completely closed; the separator outlet pressure... The value must ensure that the primary reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. ;

[0019] in:

[0020] ;

[0021] Secondary reheater purging:

[0022] Close the first re-emergency control valve. At this time, the superheat control valve closes, the second re-emergency control valve opens, and the separator outlet pressure reaches the blow-off pressure. When the superheater control valve is opened, steam passes through the superheater control valve and the granulator, then through the secondary reheater control valve, the secondary reheater, and the silencer before being discharged. When the secondary reheater blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve is closed until it is completely closed; the separator outlet pressure... The value must ensure that the primary reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. ;

[0023] in:

[0024] ;

[0025] After the above process is completed, the first stage of purging is finished;

[0026] Second stage: First reheater purge:

[0027] Close the secondary emergency control valve. At this time, the superheat emergency control valve closes, the primary emergency control valve opens, and the separator outlet pressure reaches the blow-off pressure. When the superheater control valve is opened, steam passes through the superheater control valve and the granulator, then through the primary reheater control valve, the primary reheater, and the silencer before being discharged. When the primary reheater blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve is closed until it is completely closed; the separator outlet pressure... The value must ensure that the reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. ;

[0028] in:

[0029] ;

[0030] Secondary reheater purging:

[0031] Close the first re-emergency control valve. At this time, the superheat control valve closes, the second re-emergency control valve opens, and the outlet pressure of the separator (26) reaches the blow-off pressure. When the superheater control valve is opened, steam passes through the superheater control valve and the granulator, then through the secondary reheater control valve, the secondary reheater, and the silencer before being discharged. When the secondary reheater blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve is closed until it is completely closed; the separator outlet pressure... The value must ensure that the secondary reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. ;

[0032] in:

[0033] ;

[0034] Superheater purging:

[0035] The superheater has already been purged during the primary and secondary reheater purging processes. If the superheater blow-off coefficient is greater than 1 or the purging pressure drop ratio is greater than 1.4 during the primary and secondary reheater purging processes, then separate purging is not required. satisfy: Otherwise, purge the superheater according to the following control procedures:

[0036] Open the second re-emergency control valve, then open the first re-emergency control valve. The separator outlet pressure reaches the blowdown pressure. When the superheater is in operation, the superheater control valve is opened for steam blowing. The steam passes through the superheater control valve and the granulator, then splits into two streams. One stream passes through the primary reheater control valve, the primary reheater, and the silencer before exiting; the other stream passes through the secondary reheater control valve, the secondary reheater, and the silencer before exiting. The superheater control valve is closed when the superheater blowing coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, until the superheater control valve is completely closed. The separator outlet pressure must meet the requirement that the superheater blowing coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. Second-rate,

[0037] in:

[0038] ;

[0039] Phase Three:

[0040] Superheater purging and target firing:

[0041] Open the second re-emergency control valve, then open the first re-emergency control valve. The separator outlet pressure reaches the blow-through pressure. When the superheater is in operation, the superheater control valve is opened for steam blowing. The steam passes through the superheater control valve and the granulator, then splits into two streams. One stream passes through the primary reheater control valve, the primary reheater, and the silencer before exiting; the other stream passes through the secondary reheater control valve, the secondary reheater, and the silencer before exiting. When the superheater blowing coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve is closed until it is completely closed. The separator outlet pressure must meet the requirement that the superheater blowing coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. Second-rate;

[0042] in Must meet:

[0043] ;

[0044] Install a target plate on the superheater target plate and purge the superheater. If there are no particles larger than 0.8 mm on the target plate and there are ≤ 8 spots in the range of 0.2 mm to 0.8 mm, purge the target plate continuously. When the target plate meets the above standards twice in a row, the superheater purge is qualified and the purge is stopped. Otherwise, repeat the superheater purge process.

[0045] First reheater purging and target firing:

[0046] Close the secondary emergency control valve. At this time, the superheat emergency control valve closes, the primary emergency control valve opens, and the separator outlet pressure reaches the blow-off pressure. When the superheater control valve is opened, steam passes through the superheater control valve and the granulator, then through the primary reheater control valve, the primary reheater, and the silencer before being discharged. When the primary reheater blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve is closed until it is completely closed; the separator outlet pressure... The value must ensure that the reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. ;

[0047] in satisfy:

[0048] ;

[0049] Install a target plate on the target plate and purge the reheater. If there are no particles larger than 0.8 mm on the target plate and there are ≤ 8 spots in the range of 0.2 mm to 0.8 mm, purge the target plate continuously. When the target plate meets the above standards for two consecutive times, the superheater purge is qualified and the purge is stopped. Otherwise, repeat the reheater purge process.

[0050] Secondary reheater blow-through and target firing:

[0051] Close the first re-emergency control valve. At this time, the superheat control valve closes, the second re-emergency control valve opens, and the separator outlet pressure reaches the blow-off pressure. When the superheater control valve is opened, steam passes through the superheater control valve and the granulator, then through the secondary reheater control valve, the secondary reheater, and the silencer before being discharged. When the secondary reheater blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve is closed until it is completely closed; the separator outlet pressure... The value must ensure that the reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. Second-rate;

[0052] in Must meet:

[0053] ;

[0054] A target plate is installed on the secondary reheater to purge and target it. If there are no particles larger than 0.8 mm on the target plate and there are ≤ 8 blemishes in the range of 0.2 mm to 0.8 mm, the purging is carried out continuously. When the target plate meets the above standards for two consecutive times, the superheater purging is qualified and the purging is stopped. Otherwise, the secondary reheater purging process is repeated.

[0055] Furthermore, the aforementioned overheat control door, first re-control door, and second re-control door are electrically driven.

[0056] Furthermore, the aforementioned overheat control valve flow area , and the flow area of ​​the control gate Second, the flow area of ​​the re-control gate satisfy:

[0057] ;

[0058] in, The maximum flow area of ​​the pipeline and valves before the overheat control valve;

[0059] ;

[0060] in, The maximum flow area of ​​the pipeline and valves in front of the re-imposed control gate;

[0061] ;

[0062] in, This refers to the maximum flow area of ​​the pipeline and valves in front of the re-imposed control gate.

[0063] Compared with the prior art, the beneficial effects of the present invention are:

[0064] This invention proposes a blowdown control method for a secondary reheat unit. It adjusts the traditional blowdown control method by blowing all heating surfaces of the superheater, primary reheater, and secondary reheater before the first and second shutdowns of the secondary reheat unit. In each stage, a corresponding blowdown method and a reasonable number of blowdowns are set for each heating surface, ensuring that the blowdown coefficient requirements are met while each heating surface is fully heated. This allows for sufficient oxide scale removal from each heating surface during shutdown cooling, improving the blowdown effect. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0066] The present invention will be further described below with reference to specific embodiments.

[0067] Example 1

[0068] like Figure 1 As shown, a secondary reheat unit blowdown control device includes a superheater 1, an ultra-high pressure main steam valve 2, an ultra-high pressure cylinder 3, a superheat temporary control valve 5, a superheat target plate 6, a particle collector 7, a reheat temporary control valve 8, a primary reheater 11, a primary reheat target plate 17, a secondary reheat temporary control valve 13, a high pressure main steam valve 14, a high pressure cylinder 16, a secondary reheater 19, a medium pressure main steam valve 20, a secondary reheat target plate 24, and formal or temporary pipelines connected to various thermal equipment.

[0069] The inlet of superheater 1 is connected to the outlet of separator 26 via a pipeline. The outlet of superheater 1 is connected to the main steam valve 2 of the ultra-high pressure cylinder via a pipeline (formal). There is a break 4 at the pipeline (formal) after the main steam valve 2 of the ultra-high pressure cylinder. It is connected to the superheater temporary control valve 5 via a pipeline (temporary). The outlet of the superheater temporary control valve 5 is connected to the superheater target plate 5, the particle collector 7 and the first re-temporary control valve 8 in sequence via a pipeline (temporary). The particle collector 7 and the first re-temporary control valve 8 are connected to the second re-temporary control valve 13 via a pipeline (temporary).

[0070] The temporary control valve 8 is connected to the permanent pipeline on the side of the primary reheater 11 via a pipeline (temporary) at the disconnection point 10 of the ultra-high pressure cylinder exhaust pipe. The pipeline (permanent) between the outlet of the primary reheater 11 and the main steam valve 14 of the high pressure cylinder is provided with a second break 12. The outlet pipeline of the primary reheater 11 is connected to the primary reheater target plate 17 via a pipeline (temporary) at the second break. The primary reheater target plate 17 is connected to the silencer 25 via a pipeline (temporary).

[0071] The secondary reheat valve 13 is connected to the high-pressure main steam valve 14 via a temporary pipeline at break point 12. The pipeline between the high-pressure cylinder main steam valve 14 and the high-pressure cylinder 16 is provided with break point 15. The pipeline between the high-pressure cylinder 16 and the secondary reheater 19 is provided with break point 18. The pipeline after the high-pressure main steam valve 14 is connected to the inlet pipe of the secondary reheater 19 via a temporary pipeline at break point 18. The secondary reheater 19 is connected to the intermediate-pressure main steam valve 20. The pipeline between the intermediate-pressure cylinder main steam valve 20 and the intermediate-pressure cylinder 22 is provided with break point 21. The exhaust pipe of the intermediate-pressure cylinder 22 is provided with break point 23. The pipeline after the intermediate-pressure main steam valve 20 is connected to the secondary reheat target plate via a temporary pipeline. The secondary reheat target plate is connected to the silencer 25 via a temporary pipeline.

[0072] A control method for blowdown in a double reheat unit, comprising three stages, with each stage controlled as follows:

[0073] Phase 1:

[0074] Superheater purging:

[0075] The outlet pressure of separator 26 reaches the blow-off pressure. When the superheater 1 blowdown valve 5 is opened, steam passes through the superheater 1 blowdown valve 5 and the granulator 7, then splits into two streams. One stream passes through the primary reheater 11, the secondary reheater 11, and the silencer 25 before exiting; the other stream passes through the secondary reheater 13, the secondary reheater 19, and the silencer 25 before exiting. When the superheater 1 blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater 1 blowdown valve 5 is closed until it is completely closed. The outlet pressure of the separator 26 must meet the requirement that the superheater 1 blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. Second-rate;

[0076] in:

[0077] ;

[0078] ;

[0079] ;

[0080] First reheater 11 purge:

[0081] Close the secondary emergency control valve 13. At this time, the superheat emergency control valve 5 is closed, the primary emergency control valve 8 is opened, and the outlet pressure of separator 26 reaches the blow-off pressure. When the superheater is open, the superheater control valve 5 is opened. Steam passes through the superheater control valve 5 and the granulator 7, then through the primary reheater control valve 8, the primary reheater 11, and the silencer 25 before being discharged. When the primary reheater 11 blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve 5 is closed until it is completely closed. Separator outlet pressure. The value must ensure that the blowdown coefficient of the reheater 11 is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. ;

[0082] in:

[0083] ;

[0084] Secondary reheater 19 purge:

[0085] Close the first re-emergency control valve 8. At this time, the superheat control valve 5 closes, and the second re-emergency control valve 13 opens. The outlet pressure of separator 26 reaches the blow-off pressure. When the superheater is open, the superheater control valve 5 is opened. Steam passes through the superheater control valve 5 and the granulator 7, then through the secondary reheater control valve 13, the secondary reheater 19, and the silencer 25 before being discharged. When the secondary reheater 19 blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve 5 is closed until it is completely closed. (Separator outlet pressure) The value must ensure that the primary reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. ;

[0086] in:

[0087] ;

[0088] After the above process is completed, the first stage of purging is finished.

[0089] Second stage: First reheater purge:

[0090] Close the secondary emergency control valve 13. At this time, the superheat emergency control valve 5 closes, and the primary emergency control valve 5 opens. The outlet pressure of separator 26 reaches the blowdown pressure. When the superheater is open, the superheater control valve 5 is opened. Steam passes through the superheater control valve 5 and the granulator 7, then through the primary reheater control valve 8, the primary reheater 11, and the silencer 25 before being discharged. When the primary reheater 11 blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve 5 is closed until it is completely closed. Separator outlet pressure. The value must ensure that the reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. ;

[0091] in:

[0092] ;

[0093] Secondary reheater purging:

[0094] Close the first re-emergency control valve 8. At this time, the superheat control valve 5 closes, and the second re-emergency control valve 13 opens. The outlet pressure of separator 26 reaches the blow-off pressure. When the superheater is open, the superheater control valve 5 is opened. Steam passes through the superheater control valve 5 and the granulator 7, then through the secondary reheater control valve 13, the secondary reheater 19, and the silencer 25 before being discharged. When the secondary reheater 19 blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve 5 is closed until it is completely closed. (Separator outlet pressure) The value must ensure that the secondary reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. ;

[0095] in:

[0096] ;

[0097] Superheater purging:

[0098] The superheater has already been purged during the primary and secondary reheater purging processes. If the superheater blow-off coefficient is greater than 1 or the purging pressure drop ratio is greater than 1.4 during the primary and secondary reheater purging processes, then separate purging is not required. satisfy: Otherwise, purge the superheater using the following control procedures:

[0099] Open the second re-emergency control valve 13, open the first re-emergency control valve 8, and the outlet pressure of separator 26 reaches the blow-through pressure. When the superheater is blown through the superheater, the control valve 5 is opened for steam blowing. The steam passes through the control valve 5 and the granulator 7, then splits into two streams. One stream passes through the primary reheater control valve 8, the primary reheater 11, and the silencer 25 before exiting. The other stream passes through the secondary reheater control valve 13, the secondary reheater 19, and the silencer 25 before exiting. When the superheater blowing coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve 5 is closed until it is completely closed. The outlet pressure of the separator 26 must meet the requirement that the superheater blowing coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. Second-rate;

[0100] in:

[0101] ;

[0102] Phase Three:

[0103] Superheater purging and target firing:

[0104] Open the second re-emergency control valve 13, open the first re-emergency control valve 8, and the outlet pressure of separator 26 reaches the blow-through pressure. When the superheater is blown through the superheater, the control valve 5 is opened for steam blowing. The steam passes through the control valve 5 and the granulator 7, then splits into two streams. One stream passes through the primary reheater control valve 8, the primary reheater 11, and the silencer 25 before exiting. The other stream passes through the secondary reheater control valve 13, the secondary reheater 19, and the silencer 25 before exiting. When the superheater blowing coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve 5 is closed until it is completely closed. The outlet pressure of the separator 26 must meet the requirement that the superheater blowing coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. Second-rate;

[0105] in Must meet:

[0106] ;

[0107] A target plate is installed on the superheated target plate 6 to purge the superheater 1. If there are no particles larger than 0.8 mm on the target plate and there are ≤ 8 spots in the range of 0.2 mm to 0.8 mm, the purging is carried out continuously. When the target plate meets the above standards for two consecutive times, the superheater purging is qualified and the purging is stopped. Otherwise, the superheater purging process is repeated.

[0108] First reheater purging and target firing:

[0109] Close the secondary emergency control valve 13. At this time, the superheat emergency control valve 5 closes, and the primary emergency control valve 8 opens. The outlet pressure of separator 26 reaches the blow-off pressure. When the superheater is open, the superheater control valve 5 is opened. Steam passes through the superheater control valve 5 and the granulator 7, then through the primary reheater control valve 8, the primary reheater 11, and the silencer 25 before being discharged. When the primary reheater 11 blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve 5 is closed until it is completely closed. Separator outlet pressure. The value must ensure that the reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. ;

[0110] in satisfy:

[0111] ;

[0112] A target plate is installed on the target plate 17 to purge the reheater 11. If there are no particles larger than 0.8 mm on the target plate and there are ≤ 8 blemishes in the range of 0.2 mm to 0.8 mm, the purging is carried out continuously. When the target plate meets the above standards for two consecutive times, the superheater purging is qualified and the purging is stopped. Otherwise, the reheater purging process is repeated.

[0113] Secondary reheater blow-through and target firing:

[0114] Close the first re-emergency control valve 8. At this time, the superheat control valve 5 closes, and the second re-emergency control valve 13 opens. The outlet pressure of separator 26 reaches the blow-off pressure. When the superheater is open, the superheater control valve 5 is opened. Steam passes through the superheater control valve 5 and the granulator 7, then through the secondary reheater control valve 13, the secondary reheater 19, and the silencer 25 before being discharged. When the secondary reheater 19 blowdown coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve 5 is closed until it is completely closed. (Separator outlet pressure) The value must ensure that the reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. Second-rate;

[0115] in Must meet:

[0116] ;

[0117] A target plate is installed on the secondary target plate 24 to purge the secondary reheater 19. If there are no particles larger than 0.8 mm on the target plate and there are ≤ 8 blemishes in the range of 0.2 mm to 0.8 mm, purging is carried out continuously. When the target plate meets the above standards for two consecutive times, the superheater purging is qualified and the purging is stopped; otherwise, the secondary reheater purging process is repeated.

[0118] The aforementioned overheat emergency control door 5, first emergency control door 8, and second emergency control door 13 are electrically driven.

[0119] The above-mentioned overheat control valve 5 has a flow area , and the flow area of ​​the 8th passage of the control gate. 2. Re-control gate 13 flow area It should meet the following requirements:

[0120] ;

[0121] in, This represents the maximum flow area of ​​the pipeline and valves upstream of the overheat control valve 5;

[0122] ;

[0123] in, The maximum flow area of ​​the pipeline and valves before the re-emergency control valve 8;

[0124] ;

[0125] in, This is the maximum flow area of ​​the pipeline and valves before the re-emergency control valve 8.

Claims

1. A blowdown control device for a secondary reheat unit, characterized in that, Includes a superheater (1), the inlet of which is connected to the outlet of the separator (26) via a pipe, the outlet of which is connected to the main steam valve (2) of the ultra-high pressure cylinder via a pipe, the main steam valve (2) of the ultra-high pressure cylinder via a pipe, the superheat control valve (5) via a pipe, the outlet of the superheat control valve (5) via a pipe sequentially connected to the superheat target plate (6), the particle collector (7) and the first re-control valve (8), and the particle collector (7) and the first re-control valve (8) via a pipe connected to the second re-control valve (13); The reheat control valve (8) is connected to the reheater (11) side pipe via a pipe, the reheater (11) outlet is connected to the reheat target plate (17) via a pipe, and the reheat target plate (17) is connected to the silencer (25) via a pipe. The secondary reheat control valve (13) is connected to the high-pressure main steam valve (14) via a pipeline. The high-pressure cylinder main steam valve (14) is connected to the inlet pipe of the secondary reheater (19). The secondary reheater (19) is connected to the intermediate-pressure main steam valve (20). The intermediate-pressure cylinder main steam valve (20) is connected to the secondary reheat target plate (24) via a pipeline. The secondary reheat target plate (24) is connected to the silencer (25) via a pipeline. The control method for the blowdown of the secondary reheat unit is divided into three stages, with each stage controlled as follows: Phase 1: Superheater purging: The outlet pressure of the separator (26) reaches the blow-off pressure. When the superheater is blown through the superheater (5), the steam passes through the superheater (5) and the collector (7) and is then divided into two paths. One path passes through the first reheater (8), the first reheater (11), and the silencer (25) before being discharged. The other path passes through the second reheater (13), the second reheater (19), and the silencer (25) before being discharged. When the superheater (1) blow-through coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater (5) is closed until the superheater (5) is completely closed. The outlet pressure of the separator (26) must meet the requirement that the superheater (1) blow-through coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. Second-rate; in: ； ； ； First reheater purge: Close the secondary re-control valve (13). At this time, the superheat control valve (5) closes, the primary re-control valve (8) opens, and the outlet pressure of the separator (26) reaches the blow-off pressure. When the superheater control valve (5) is opened, the steam passes through the superheater control valve (5), the granulator (7), and then through the reheater control valve (8), the primary reheater (11), and the silencer (25) before being discharged. When the blowing coefficient of the primary reheater (11) is greater than 0.92 or the purging pressure drop ratio is greater than 1.3, the superheater control valve (5) is closed until the superheater control valve (5) is completely closed; the separator outlet pressure The value must ensure that the blowdown coefficient of the reheater (11) is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. ; in: ； Secondary reheater purging: When the first re-emergency control valve (8) is closed, the superheat control valve (5) is closed, the second re-emergency control valve (13) is opened, and the outlet pressure of the separator (26) reaches the blow-off pressure. When the superheater control valve (5) is opened, the steam passes through the superheater control valve (5) and the granulator (7) respectively, and then passes through the secondary reheater control valve (13), the secondary reheater (19), and the silencer (25) before being discharged. When the blowdown coefficient of the secondary reheater (19) is greater than 0.92 or the purging pressure drop ratio is greater than 1.3, the superheater control valve (5) is closed until the superheater control valve (5) is completely closed; the separator outlet pressure The value must ensure that the primary reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. ; in: ； After the above process is completed, the first stage of purging is finished; Second stage: First reheater purge: Close the secondary re-control valve (13). At this time, the superheat control valve (5) closes, the primary re-control valve (8) opens, and the outlet pressure of the separator (26) reaches the blow-off pressure. When the superheater control valve (5) is opened, the steam passes through the superheater control valve (5), the granulator (7), and then through the reheater control valve (8), the primary reheater (11), and the silencer (25) before being discharged. When the blowing coefficient of the primary reheater (11) is greater than 0.92 or the purging pressure drop ratio is greater than 1.3, the superheater control valve (5) is closed until the superheater control valve (5) is completely closed; the separator outlet pressure The value must ensure that the reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. ; in: ； Secondary reheater purging: When the first re-emergency control valve (8) is closed, the superheat control valve (5) is closed, the second re-emergency control valve (13) is opened, and the outlet pressure of the separator (26) reaches the blow-off pressure. When the superheater control valve (5) is opened, the steam passes through the superheater control valve (5) and the granulator (7) respectively, and then passes through the secondary reheater control valve (13), the secondary reheater (19), and the silencer (25) before being discharged. When the blowdown coefficient of the secondary reheater (19) is greater than 0.92 or the purging pressure drop ratio is greater than 1.3, the superheater control valve (5) is closed until the superheater control valve (5) is completely closed; the separator outlet pressure The value must ensure that the secondary reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. ; in: ； Superheater purging: The superheater has already been purged during the primary and secondary reheater purging processes. If the superheater blow-off coefficient is greater than 1 or the purging pressure drop ratio is greater than 1.4 during the primary and secondary reheater purging processes, then separate purging is not required. satisfy: Otherwise, purge the superheater according to the following control procedures: Open the second re-emergency control valve (13), open the first re-emergency control valve (8), and the outlet pressure of the separator (26) reaches the blow-through pressure. When the superheater is blown through the superheater, the superheater control valve (5) is opened for steam blowing. After passing through the superheater control valve (5) and the granulator (7), the steam is divided into two paths. One path passes through the first reheater control valve (8), the first reheater (11), and the silencer (25) before being discharged. The other path passes through the second reheater control valve (13), the second reheater (19), and the silencer (25) before being discharged. When the superheater blowing coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve (5) is closed until the superheater control valve (5) is completely closed. The outlet pressure of the separator (26) must meet the requirement that the superheater blowing coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. Second-rate, in: ； Phase Three: Superheater purging and target firing: Open the second re-emergency control valve (13), open the first re-emergency control valve (8), and the outlet pressure of the separator (26) reaches the blow-through pressure. When the superheater is blown through the superheater, the superheater control valve (5) is opened for steam blowing. After passing through the superheater control valve (5) and the granulator (7), the steam is divided into two paths. One path passes through the first reheater control valve (8), the first reheater (11), and the silencer (25) before being discharged. The other path passes through the second reheater control valve (13), the second reheater (19), and the silencer (25) before being discharged. When the superheater blowing coefficient is greater than 0.92 or the purge pressure drop ratio is greater than 1.3, the superheater control valve (5) is closed until the superheater control valve (5) is completely closed. The outlet pressure of the separator (26) must meet the requirement that the superheater (1) blowing coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4 and lower than the limit value. Repeat the above process. Second-rate; in Must meet: ； Install a target plate on the superheated target plate (6) and purge the superheater (1) with the target plate. If there are no particles larger than 0.8 mm on the target plate and there are ≤ 8 spots in the range of 0.2 mm to 0.8 mm, the target plate will be purged continuously. When the target plate meets the above standards twice in a row, the superheater is purged and the target plate is purged. Otherwise, repeat the superheater purging process. First reheater purging and target firing: Close the secondary re-control valve (13). At this time, the superheat control valve (5) closes, the primary re-control valve (8) opens, and the outlet pressure of the separator (26) reaches the blow-off pressure. When the superheater control valve (5) is opened, the steam passes through the superheater control valve (5), the granulator (7), and then through the reheater control valve (8), the primary reheater (11), and the silencer (25) before being discharged. When the blowing coefficient of the primary reheater (11) is greater than 0.92 or the purging pressure drop ratio is greater than 1.3, the superheater control valve (5) is closed until the superheater control valve (5) is completely closed; the separator outlet pressure The value must ensure that the reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. ; in satisfy: ； Install a target plate on the target plate (17) and purge the reheater (11) with the target plate. If there are no particles larger than 0.8 mm on the target plate and there are ≤ 8 spots in the range of 0.2 mm to 0.8 mm, purge the target plate continuously. When the target plate meets the above standards for two consecutive times, the superheater purge is qualified and the purge is stopped. Otherwise, repeat the reheater purge process. Secondary reheater blow-through and target firing: When the first re-emergency control valve (8) is closed, the superheat control valve (5) is closed, the second re-emergency control valve (13) is opened, and the outlet pressure of the separator (26) reaches the blow-off pressure. When the superheater control valve (5) is opened, the steam passes through the superheater control valve (5) and the granulator (7) respectively, and then passes through the secondary reheater control valve (13), the secondary reheater (19), and the silencer (25) before being discharged. When the blowdown coefficient of the secondary reheater (19) is greater than 0.92 or the purging pressure drop ratio is greater than 1.3, the superheater control valve (5) is closed until the superheater control valve (5) is completely closed; the separator outlet pressure The value must ensure that the reheater blowdown coefficient is greater than 1 or the purge pressure drop ratio is greater than 1.4, and the above process is repeated. Second-rate; in Must meet: ； The target plate is installed on the secondary target plate (24) to purge the secondary reheater (19). If there are no particles larger than 0.8 mm on the target plate and there are ≤ 8 spots in the range of 0.2 mm to 0.8 mm, the purging is carried out continuously. When the target plate meets the above standards for two consecutive times, the superheater is qualified and the purging is stopped. Otherwise, the secondary reheater purging process is repeated.

2. The control device for blowdown pipe of a secondary reheat unit according to claim 1, characterized in that, The overheat control door (5), the first re-control door (8), and the second re-control door (13) are electrically driven.

3. The control device for the blowdown pipe of a secondary reheat unit according to claim 1, characterized in that, The flow area of ​​the overheat control valve (5) 、One-time control gate (8) flow area 2. Re-entry control gate (13) flow area satisfy: ； in, The maximum flow area of ​​the pipeline and valves before the overheat control valve (5); ； in, The maximum flow area of ​​the pipeline and valves before the re-emergency control valve (8); ； in, The maximum flow area of ​​the pipeline and valves before the re-emergency control valve (8) is given.

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