Method for discharging sewage during normal operation period of horizontal steam generator

Abstract

The invention relates to a method for discharging sewage during normal operation of a horizontal steam generator, which can more scientifically and effectively discharge the sewage of the steam generator, introduce the sewage to a purification system, remove corrosion products and dissolved impurities, and return the purified sewage to a secondary loop steam-water circulation system to maintain the hydrochemical working condition index of the secondary loop. Comprising continuous blowdown and regular blowdown, the continuous blowdown refers to a blowdown pipeline and blowdown flow fixed on the lower portion of a cold end salt chamber of the steam generator, and the regular blowdown refers to blowdown with set time in turn through a plurality of blowdown pipelines at the bottom of the steam generator. The invention provides a method for discharging sewage during normal operation of a horizontal steam generator, so that the sewage can be discharged scientifically, effectively, automatically and continuously, and the water chemical working condition of a secondary loop is maintained in a normal range.

Description

Technical Field

[0001] The invention relates to a method for discharging wastewater during normal operation of a horizontal steam generator, which can more scientifically and effectively discharge wastewater from the steam generator, and lead the wastewater to a purification system to remove corrosion products and dissolved impurities, and return the purified wastewater to a secondary circuit steam-water circulation system to maintain the water chemical working condition indicators of the secondary circuit. Background Art

[0002] Nuclear power units have clear requirements for the water quality of steam generators during power operation, that is, the water chemistry of the secondary circuit must be maintained within the specified range. Therefore, continuous blowdown of the steam generator must be ensured during power operation, and continuous monitoring of the blowdown of the steam generator is also required to ensure that the water quality indicators meet the specified requirements.

[0003] During the power operation of Tianwan Nuclear Power Units 1-4, when the temperature, pressure and liquid level of the steam generator are stable, if the water quality indicators of the steam generator exceed the design requirements, the units need to be withdrawn in accordance with the requirements of the technical specifications.

[0004] By setting up continuous and regular blowdown procedures, the steam generator blowdown can be carried out scientifically and effectively, and the water quality requirements of the steam generator can be effectively guaranteed by continuous monitoring of the blowdown water. Therefore, a scientific steam generator blowdown method can more effectively guarantee the water chemistry operating indicators of the secondary circuit. Summary of the invention

[0005] The object of the present invention is to provide a method for discharging waste during normal operation of a horizontal steam generator, so that the waste discharge can be scientifically and effectively automatically and continuously operated to ensure that the water chemical condition of the secondary circuit is maintained within a normal range.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for discharging sewage during normal operation of a horizontal steam generator includes continuous sewage discharge and periodic sewage discharge. The continuous sewage discharge is a sewage discharge pipeline and sewage discharge flow fixed at the lower part of the salt chamber at the cold end of the steam generator. The periodic sewage discharge is carried out through multiple sewage discharge pipelines at the bottom of the steam generator, and the sewage is discharged in turn at set times.

[0008] Continuous sewage discharge: Each steam generator has a sewage discharge pipeline, which is the pipeline where the stop valve V8 is located. The sewage discharge flow rate is set to 4.2kg / s. By controlling the regulating valve V 10 Ensure the continuous blowdown flow of the steam generator, and appropriately increase the continuous blowdown flow when the secondary circuit water chemistry conditions deviate.

[0009] There are 10 water supply manifolds on the hot end side of the steam generator and 5 water supply manifolds on the cold end side.

[0010] Regular sewage discharge: Each steam generator has 10 regular sewage discharge pipes, which are evenly arranged and used for regular sewage discharge from the bottom of the steam generator, and then collected into a header; the four steam generators take turns to carry out regular sewage discharge, and each steam generator opens the stop valve V1, stop valve V4, stop valve V5, and stop valve V7 in sequence.

[0011] Step 1: Open the stop valve V1, and set the flow rate to 6.7kg / s by controlling the regulating valve V9. After 25 minutes of sewage discharge, close the stop valve V1; Step 2: Open the stop valve V4, and set the flow rate to 5kg / s by controlling the regulating valve V9. After 45 minutes of sewage discharge, close the stop valve V4; Step 3: Open the stop valve V5, and set the flow rate to 6.7kg / s by controlling the regulating valve V9. After 25 minutes of sewage discharge, close the stop valve V5; Step 4: Open the stop valve V7, and set the flow rate to 5kg / s by controlling the regulating valve V9. After 25 minutes of sewage discharge, close the stop valve V5; Step 5: Open the stop valve V7, and set the flow rate to 6.7kg / s by controlling the regulating valve V9. After 25 minutes of sewage discharge, close the stop valve V5; Step 6: Open the stop valve V8, and set the flow rate to 5kg / s by controlling the regulating valve V9. After 25 minutes of sewage discharge, close the stop valve V8; Step 7: Open the stop valve V9, and set the flow rate to 5kg / s by controlling the regulating valve V9. After 25 minutes of sewage discharge, close the stop valve V8; Step 8: Regulating valve V9, set the flow rate to 6.7kg / s, and close stop valve V7 after 25 minutes of sewage discharge; Step 5: Open stop valve V1, stop valve V2, stop valve V3, stop valve V4, stop valve V5, stop valve V6, stop valve V7 at the same time, set regulating valve V9 to 5% valve position mode, maintain the total flow rate at 0.55kg / s, and ensure that the regular sewage discharge pipeline of this steam generator is in preheating mode; Step 6: Start the regular sewage discharge procedure of the next steam generator, and automatically repeat the above five steps.

[0012] For the Tianwan nuclear power unit, there are four horizontal steam generators. Only one steam generator is discharging sewage regularly at the same time, and the other three steam generators are in small flow preheating mode. The control program controls the four steam generators to continuously and automatically circulate and discharge sewage.

[0013] All wastewater is collected and supplied to the wastewater purification system filter. After a series of cooling and purification, the purified water is returned to the secondary steam-water circulation system.

[0014] Sampling monitoring is carried out on the continuous sewage discharge pipeline and the periodic sewage discharge pipeline respectively. Both automatic sampling monitoring and manual sampling monitoring are carried out to monitor the water chemical condition of the steam generator at any time. When the water quality of the steam generator deviates, it can be immediately discovered and the relevant alarm is triggered. The personnel can promptly check the defects and make judgments, and make relevant responses to ensure that the water quality of the secondary circuit is within the specified range, so that the unit can always operate in a safe and stable state.

[0015] The beneficial effects achieved by the present invention are:

[0016] ①It has broad promotion value and is widely used:

[0017] At present, units 1-4, 7 and 8 of Tianwan Nuclear Power Plant, and units 3 and 4 of Xudabao Nuclear Power Plant all use horizontal steam generators of the same design. This sewage discharge method can be widely used by nuclear power plants of the same industry to improve the overall operating stability of China's nuclear power units.

[0018] ② Improve equipment performance and extend service life:

[0019] This method of sewage discharge for horizontal steam generators maintains the water quality of the secondary circuit at a high level, improves equipment performance and extends its service life. This measure will improve the safety and stability of the operation of units at Tianwan Nuclear Power Plant and its peers.

[0020] ③Precise control of sewage discharge flow to ensure high efficiency of sewage discharge:

[0021] By setting up two blowdown programs for the steam generator, continuous blowdown and periodic blowdown, the flow and switching of the blowdown can be accurately controlled, and the blowdown of the horizontal steam generator can be effectively carried out, ensuring the high efficiency of the blowdown.

[0022] ④ Reduce costs and increase efficiency, with high economic efficiency:

[0023] This sewage discharge method can not only accurately and effectively control the sewage discharge flow rate, but also minimize the heat loss of the steam-water cycle in the secondary circuit, thereby improving the thermal efficiency of the steam-water cycle in the secondary circuit and having high economic efficiency.

[0024] ⑤Adopt automated program control, safe and reliable:

[0025] An automatic sequential control program for continuous and periodic blowdown of the steam generator is set up to ensure that the blowdown is continuous, automatic, safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a method for discharging waste during normal operation of a horizontal steam generator;

[0027] Among them: V1, V2, V3, V4, V5, V6, V7 represent the stop valves of the regular sewage pipelines at the bottom of the steam generator, a total of 10 pipelines, evenly arranged;

[0028] V8 represents the stop valve of the continuous blowdown line of the salt chamber at the cold end of the steam generator;

[0029] V9 represents the regular sewage header regulating valve;

[0030] V 10 Stands for Continuous Blowdown Line Regulating Valve. DETAILED DESCRIPTION

[0031] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] By setting up two drainage methods for steam generators, continuous drainage and periodic drainage, continuous drainage is a fixed drainage pipeline and drainage flow rate in the cold end salt chamber of the steam generator to ensure continuous and effective drainage. Periodic drainage uses multiple drainage pipelines at the bottom of the steam generator to drain the set time in turn, thereby ensuring the drainage effect of the bottom area.

[0033] To ensure the effectiveness and automatic controllability of the method, the temperature, pressure and liquid level of the steam generator are required to be stable during the discharge period, and at the same time, related operations that affect the normal operation of the discharge system should be avoided. Finally, the reliability of the discharge method is determined by monitoring the water quality of the discharge. This calculation method has been well verified in Tianwan Units 1-4 and achieved the expected effect.

[0034] 1. Continuous sewage discharge

[0035] In the structure of the steam generator, there are 10 water supply manifolds on the hot end side and only 5 water supply manifolds on the cold end side, so that the water supply flow on the hot end side is greater than that on the cold end side. On the one hand, this design can make the steam production of the cold end and the hot end uniform, and on the other hand, it can make the boiler water in the steam generator flow from the hot end to the cold end, bringing impurities from the hot end to the cold end. Therefore, a "salt chamber" is set at the cold end to effectively collect impurities.

[0036] In order to discharge the impurities in the "salt chamber" in time, a continuous sewage connection is installed at the bottom of the "salt chamber", which can discharge the impurities in the steam generator in the fastest and most direct way, ensuring the effective sewage discharge of the steam generator and the qualified water quality of the secondary circuit.

[0037] Each steam generator has a sewage pipe connection, namely Figure 1 The regulator sets the sewage flow rate to 4.2kg / s in the pipeline where the stop valve V8 is located. 10 Ensure the continuous blowdown flow of the steam generator, and appropriately increase the continuous blowdown flow when the secondary circuit water chemical conditions deviate.

[0038] 2. Regular sewage discharge

[0039] Each steam generator has 10 regular blowdown pipes, which are evenly arranged and used to regularly discharge blowdown from the bottom of the steam generator and then collect it into a header. Figure 1 .

[0040] The four steam generators take turns to discharge sewage regularly, and each steam generator opens valves V1, V4, V5, and V7 in sequence.

[0041] Step 1: Open the stop valve V1, set the flow rate to 6.7kg / s by controlling the regulating valve V9, and close the stop valve V1 after 25 minutes of sewage discharge;

[0042] Step 2: Open the stop valve V4, set the flow rate to 5kg / s by controlling the regulating valve V9, and close the stop valve V4 after 45 minutes of sewage discharge;

[0043] Step 3: Open the stop valve V5, set the flow rate to 6.7kg / s by controlling the regulating valve V9, and close the stop valve V5 after 25 minutes of sewage discharge;

[0044] Step 4: Open the stop valve V7, set the flow rate to 6.7kg / s by controlling the regulating valve V9, and close the stop valve V7 after 25 minutes of sewage discharge;

[0045] Step 5: Open stop valve V1, stop valve V2, stop valve V3, stop valve V4, stop valve V5, stop valve V6 and stop valve V7 at the same time, set the sewage pipeline regulating valve V9 to 5% valve position mode, maintain the total flow rate at 0.55 kg / s, and ensure that the regular sewage pipeline of this steam generator is in preheating mode;

[0046] Step 6: Start the regular blowdown procedure for the next steam generator and automatically repeat the above five steps.

[0047] For the Tianwan nuclear power unit, there are four horizontal steam generators. Only one steam generator is discharging sewage regularly at the same time, and the other three steam generators are in small flow preheating mode. The control program controls the four steam generators to continuously and automatically circulate and discharge sewage, which maximizes the sewage discharge effect of the steam generator, greatly improves the water chemistry conditions of the secondary circuit, and improves the safety and stability of the unit operation.

[0048] 3. Purification and monitoring of sewage discharge

[0049] In order to keep the water chemistry of the steam generator boiler water within the standard range, a steam generator sewage system is set up. The sewage is discharged from the places in the steam generator where corrosive products (salt chamber) and residues (shell bottom and primary side collecting pipe clamp cavity) are most likely to accumulate. All sewage is collected and supplied to the sewage purification system filter. After a series of cooling and purification, the purified water is returned to the secondary circuit steam-water circulation system, which not only ensures the sewage discharge effect, but also ensures the water capacity of the secondary circuit, does not cause steam and water loss, and greatly improves the efficiency and economy of the unit.

[0050] At the same time, a sampling system is set up to sample and monitor the continuous sewage discharge pipelines and periodic sewage discharge pipelines respectively. There are both automatic sampling and monitoring and manual sampling and monitoring. The water chemical conditions of the steam generator can be monitored at any time. When the water quality of the steam generator deviates, it can be immediately discovered and the relevant alarm can be triggered. Personnel can promptly check defects and make judgments, and make relevant responses to ensure that the water quality of the secondary circuit is within the specified range, so that the unit can always operate in a safe and stable state.

Claims

1. A method for discharging waste during normal operation of a horizontal steam generator, characterized in that: It includes continuous blowdown and periodic blowdown. Continuous blowdown is a fixed blowdown pipeline and blowdown flow at the bottom of the salt chamber at the cold end of the steam generator. Periodic blowdown is through multiple blowdown pipelines at the bottom of the steam generator, which take turns to discharge blowdown at set times.

2. The method for discharging waste during normal operation of a horizontal steam generator according to claim 1, characterized in that: Continuous sewage discharge: Each steam generator has a sewage discharge pipeline, which is the pipeline where the stop valve V8 is located. The sewage discharge flow rate is set to 4.2kg / s. By controlling the regulating valve V 10 Ensure the continuous blowdown flow of the steam generator, and appropriately increase the continuous blowdown flow when the secondary circuit water chemistry conditions deviate.

3. The method for discharging waste during normal operation of a horizontal steam generator according to claim 1, characterized in that: There are 10 water supply manifolds on the hot end side of the steam generator and 5 water supply manifolds on the cold end side.

4. The method for discharging waste during normal operation of a horizontal steam generator according to claim 1, characterized in that: Regular sewage discharge: Each steam generator has 10 regular sewage discharge pipes, which are evenly arranged and used for regular sewage discharge from the bottom of the steam generator, and then collected into a header; the four steam generators take turns to carry out regular sewage discharge, and each steam generator opens the stop valve V1, stop valve V4, stop valve V5, and stop valve V7 in sequence.

5. The method for discharging waste during normal operation of a horizontal steam generator according to claim 4, characterized in that: the first step: Open the stop valve V1, and set the flow rate to 6.7kg / s by controlling the regulating valve V9. After 25 minutes of sewage discharge, close the stop valve V1; Step 2: Open the stop valve V4, and set the flow rate to 5kg / s by controlling the regulating valve V9. After 45 minutes of sewage discharge, close the stop valve V4; Step 3: Open the stop valve V5, and set the flow rate to 6.7kg / s by controlling the regulating valve V9. After 25 minutes of sewage discharge, close the stop valve V5; Step 4: Open the stop valve V7, and set the flow rate to 5kg / s by controlling the regulating valve V9. After 45 minutes of sewage discharge, close the stop valve V5; Step 5: Open the stop valve V7, and set the flow rate to 6.7kg / s by controlling the regulating valve V9. After 25 minutes of sewage discharge, close the stop valve V5; Step 6: Open the stop valve V8, and set the flow rate to 5kg / s by controlling the regulating valve V9. After 25 minutes of sewage discharge, close the stop valve V8; Step 7: Open the stop valve V9, and set the flow rate to 5kg / s by controlling the regulating valve V9. After 25 minutes of sewage discharge, close the stop valve V8; Step 8: Valve V9, set the flow rate to 6.7kg / s, and close the stop valve V7 after 25 minutes of sewage discharge; Step 5: Open the stop valve V1, stop valve V2, stop valve V3, stop valve V4, stop valve V5, stop valve V6, and stop valve V7 at the same time, and set the regulating valve V9 to 5% valve position mode, maintain the total flow rate at 0.55kg / s, and ensure that the regular sewage discharge pipeline of this steam generator is in preheating mode; Step 6: Start the regular sewage discharge procedure of the next steam generator, and automatically repeat the above five steps.

6. The method for discharging waste during normal operation of a horizontal steam generator according to claim 4, characterized in that: For the Tianwan nuclear power unit, there are four horizontal steam generators. Only one steam generator is discharging sewage regularly at the same time, and the other three steam generators are in small flow preheating mode. The control program controls the four steam generators to continuously and automatically circulate and discharge sewage.

7. The method for discharging waste during normal operation of a horizontal steam generator according to claim 1, characterized in that: All sewage is collected and supplied to the sewage purification system filter. After a series of cooling and purification, the purified water is returned to the secondary loop steam-water circulation system.

8. The method for discharging waste during normal operation of a horizontal steam generator according to claim 1, characterized in that: Sampling monitoring is carried out on the continuous sewage discharge pipeline and the periodic sewage discharge pipeline respectively. Both automatic sampling monitoring and manual sampling monitoring are carried out to monitor the water chemical condition of the steam generator at any time. When the water quality of the steam generator deviates, it can be immediately discovered and the relevant alarm is triggered. The personnel can promptly check the defects and make judgments, and make relevant responses to ensure that the water quality of the secondary circuit is within the specified range, so that the unit can always operate in a safe and stable state.

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