An oxygen removal, cooling and cavitation-resistant feed water system

Abstract

The present invention relates to a deaerating and cooling cavitation-resistant feed water system, which has a deaerator. The saturated water after deaeration in the deaerator water tank and condensate water or circulating water reduce the temperature of the water at the outlet of the deaerator through a non-contact heat exchange method, generating a certain degree of subcooling. The subcooled feed water then enters the feed water pump, which can significantly increase the net positive suction head (NPSH) of the working medium water at the inlet of the feed water pump to prevent cavitation of the feed water pump during the operation of the deaerator. At the same time, since the feed water and the cooling water adopt a non-contact heat exchange method, it can prevent external oxygen and impurities from entering the feed water to ensure that the oxygen content and water quality of the feed water do not change. The present invention provides great convenience for medium and high pressure deaerators set in the thermal system. In the thermal system, a deaerator with a stronger heat exchange capacity in the form of a mixed heat exchanger can be used to receive exhaust steam, high-temperature drain water, etc. for heating condensate water to achieve a significant temperature rise of the condensate water and reduce the use of large-sized high and low pressure heaters.

Description

Technical Field

[0001] The present invention relates to a secondary loop system of a nuclear power plant, and particularly to a mobile secondary loop system for supporting a fourth-generation nuclear power metal reactor. Background Art

[0002] The deaerator is an important device in the secondary loop system of a nuclear power plant. Its function is to heat the condensate to saturation to remove most of the non-condensable gases in the condensate to achieve the purpose of deaeration. To ensure the safe operation of the feed water pump, generally, the deaerator needs to be arranged at a high position. The installation height of the atmospheric deaerator is 7m, the medium-pressure deaerator is 11 - 13m, and the high-pressure deaerator is 17 - 18m.

[0003] The deaerator is a relatively large device, and the high-position arrangement has a high installation cost and brings great difficulties to maintenance and repair, etc. At present, the main measure to reduce the installation height of the deaerator is to increase the injection pump between the deaerator and the inlet of the feed water pump to increase the perfusion height in front of the feed water pump. After inquiry, there is no deaerating, cooling and cavitation-resistant feed water system of this type at home and abroad. Summary of the Invention

[0004] The problem to be solved by the present invention: In view of the above problems, a deaerating, cooling and cavitation-resistant feed water system is proposed, which can greatly reduce the installation height of the deaerator while ensuring that the oxygen content of the feed water meets the requirements.

[0005] To achieve the above object, the technical solution of the present invention is: A deaerating, cooling and cavitation-resistant feed water system has a deaerator. The saturated water after deaeration in the deaerator water tank and the condensate or circulating water reduce the temperature of the water at the outlet of the deaerator through a non-contact heat exchange method, generating a certain degree of subcooling. The subcooled feed water then enters the feed water pump, which can greatly increase the net positive suction head of the working medium water at the inlet of the feed water pump to prevent cavitation of the feed water pump during the operation of the deaerator. At the same time, since the feed water and the cooling water adopt a non-contact heat exchange method, it can prevent external oxygen and impurities from entering the feed water to ensure that the oxygen content and water quality of the feed water do not change.

[0006] Further, the net positive suction head at the inlet of the feed water pump is accurately set by adjusting the temperature reduction value of the water at the outlet of the deaerator.

[0007] Further, the non-contact heat exchange method adopts a cooler. After a small part of the feed water after the deaerated saturated water of the deaerator is pressurized by the feed water pump is led to the cooler through a branch pipe to be cooled by a certain temperature, it is injected into the outlet pipeline of the deaerator.

[0008] Further, at least one branch with an electric control valve is provided in the pipeline after the cooler. The branch with the electric control valve is used to adjust the cooling flow rate under variable working conditions, adjust the feed water temperature, and further adjust the net positive suction head in front of the feed water pump;

[0009] Furthermore, a branch with a manual valve is also provided on the pipeline behind the cooler to maintain the minimum flow rate and prevent cavitation of the feed water pump caused by misoperation or adjustment lag of the electric control valve.

[0010] Furthermore, for the non-contact heat exchange method, a condensate tank is adopted. The saturated water of the deaerator in the deaerator flows through the condensate tank and exchanges heat with the condensate therein to be cooled to a certain temperature, and then is pressurized by the feed water pump and supplied to the subsequent steam generator or high and low pressure heaters. A condensate pump is arranged behind the condensate tank and is injected into the deaerator after being pressurized by the condensate pump.

[0011] Furthermore, for the non-contact heat exchange method, a cooler is adopted. The saturated water of the deaerator in the deaerator flows through the cooler to exchange heat and is cooled to a certain temperature, and then is pressurized by the feed water pump and supplied to the subsequent steam generator or high and low pressure heaters.

[0012] Furthermore, the cooling water in the cooler is condensate water. After absorbing heat and rising in temperature, the condensate water is injected into the deaerator.

[0013] Furthermore, two branches are arranged behind the cooler to maintain the minimum cooling water volume requirement of the cooler during operation. Each branch is provided with a regulating valve. One regulating valve is used to control the water volume entering the deaerator, and the other regulating valve is used to maintain the minimum condensate flow rate.

[0014] Furthermore, a bypass branch is arranged on the condensate side pipeline of the cooler to regulate the flow rate passing through the cooler and control the temperature of the feed water cooling.

[0015] The beneficial effects of the present invention are as follows:

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The vertical layout height between the deaerator and the feed water pump can be greatly reduced. If the feed water cooling temperature is sufficient, the layout height limit does not need to be considered, which can greatly increase the equipment layout flexibility, reduce the construction investment, and reduce the maintenance difficulty.

[0018] 2. While greatly reducing the vertical layout height between the deaerator and the feed water pump, it can ensure that the oxygen content of the feed water does not increase to meet the requirements of the steam generator for the oxygen content of the feed water.

[0019] 3. This type provides great convenience for setting medium and high pressure deaerators in the thermal system. In the thermal system, a deaerator with a stronger heat exchange capacity in the form of a mixing heat exchanger can be used to receive exhaust steam, high temperature drain water, etc. for heating the condensate, so as to achieve a large temperature rise of the condensate and reduce the use of large-sized high and low pressure heaters. Description of the Drawings

[0020] Figure 1It is the system diagram of the first type of the principle and embodiment of the deaeration, cooling and cavitation-resistant feed water system of the present invention;

[0021] Figure 2 It is the system diagram of the second type of the embodiment of the present invention;

[0022] Figure 3 It is the system diagram of the third type of the embodiment of the present invention;

[0023] In the figure: 1 - deaerator, 2 - regulating valve, 3 - electric regulating valve, 4 - feed water pump, 5 - manual valve, 6 - cooler, 7 - condensate tank, 8 - condensate pump, 9 - regulating valve A, 10 - regulating valve B. Specific embodiments

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0025] As Figure 1 shown, for a deaeration, cooling and cavitation-resistant feed water system provided by the present invention, the saturated water after deaeration in the deaerator 1 tank is in non-contact heat exchange with condensate water or circulating water to reduce the temperature of the water at the outlet of the deaerator 1 by a certain degree, generating a certain degree of subcooling. The subcooled feed water then enters the feed water pump. This method can significantly increase the net positive suction head (NPSH) of the working medium water at the pump inlet to prevent the feed water pump from cavitating due to various reasons during the operation of the deaerator. At the same time, since the feed water and the cooling water use non-contact heat exchange, it can prevent external oxygen and impurities from entering the feed water to ensure that the oxygen content and water quality of the feed water do not change. In a deaeration, cooling and cavitation-resistant feed water system of this solution, the net positive suction head at the inlet of the feed water pump 4 can be accurately set by adjusting the temperature reduction value of the water at the outlet of the deaerator 1. Its structural principle is mainly as Figure 1 shown.

[0026] Figure 1 After the deaerated saturated water in the deaerator 1 in

[0027] During the startup process of this type, to prevent cavitation of the feed water pump, there are two operating strategies: one is to start the feed water pump 4 through the recirculation loop before the water in the deaerator reaches the saturation temperature, and adjust the valve 2 to keep the water in the deaerator 1 in a low-flow circulation state. At this time, after the water in the deaerator 1 becomes saturated, the feed water pump 4 will not cavitate; the other is to set a branch pipe in the outlet pipeline of the deaerator 1, and inject a small amount of low-temperature condensate through this branch pipe before starting the feed water pump 4 to reduce the feed water temperature and meet the requirement of the cavitation margin for starting the feed water pump 4.

[0028] Embodiment Type 1:

[0029] As Figure 1 shown, a small part of the feed water after the deaerated saturated water in the deaerator 1 in Type 1 is pressurized by the feed water pump 4 is led to the cooler 6 through the branch pipe, cooled to a certain temperature, and then injected into the outlet pipeline of the deaerator 1. Preferably, two branch roads are set in the pipeline after the cooler 6 (it can be selected to set only one according to specific conditions), and independent valves are set on the two branch roads. Preferably, one is set with an electric control valve 3 and the other is set with a manual valve. The road with the electric control valve 3 is used to adjust the cooling flow rate under variable working conditions to maintain the stability of the outlet temperature of the feed water; the branch road with the manual valve is used to maintain the minimum flow rate to prevent cavitation of the feed water pump caused by misoperation or adjustment lag of the electric control valve 3.

[0030] During the startup process of this type, to prevent cavitation of the feed water pump, there are two operating strategies: one is to start the feed water pump 4 through the recirculation loop before the water in the deaerator reaches the saturation temperature, and adjust the valve 2 to keep the water in the deaerator in a low-flow circulation state. At this time, after the water in the deaerator becomes saturated, the feed water pump will not cavitate; the other is to set a branch pipe in the outlet pipeline of the deaerator, and inject a small amount of low-temperature condensate through this branch pipe before starting the feed water pump to reduce the feed water temperature and meet the requirement of the cavitation margin for starting the feed water pump.

[0031] Embodiment Type 2:

[0032] As Figure 2 shown, the deaerated saturated water in the deaerator 1 in Type 2 flows through the condensate tank 7, exchanges heat with the condensate in it, is cooled to a certain temperature, is pressurized by the feed water pump 4, and then supplied to the subsequent steam generator or high and low pressure heaters. A condensate pump 8 is set behind the condensate tank and is injected into the deaerator 1 after being pressurized by the condensate pump.

[0033] Embodiment Type 3:

[0034] As Figure 3 shown, the deaerated saturated water in the deaerator 1 in Type 3 flows through the cooler 6, exchanges heat and is cooled to a certain temperature, is pressurized by the feed water pump 4, and then supplied to the subsequent steam generator or high and low pressure heaters.

[0035] The cooling water in the cooler 6 is preferably condensate water. After absorbing heat in the cooler 6 and increasing in temperature, the condensate water is injected into the deaerator 1. To maintain the minimum cooling water volume requirement of the cooler 6 during operation, two branches are provided after the cooler 6, and a regulating valve is provided for each branch. One regulating valve A9 is used to control the water volume entering the deaerator 1, and the other regulating valve B10 is used to maintain the minimum condensate flow rate.

[0036] In this type, a bypass branch can be provided on the condensate side pipeline of the cooler 6 to regulate the flow rate passing through the cooler 6 to control the temperature of the feed water cooling.

Claims

1. A deaerating and cooling cavitation-resistant feed water system, having a deaerator, is characterized in that: The saturated water after deaeration in the deaerator tank and the condensate water or circulating water reduce the temperature of the water at the outlet of the deaerator through a non-contact heat exchange method, generating a certain degree of subcooling. The subcooled feed water then enters the feed water pump, which can significantly increase the net positive suction head (NPSH) of the working medium water at the inlet of the feed water pump to prevent cavitation of the feed water pump during the operation of the deaerator. At the same time, since the feed water and the cooling water use a non-contact heat exchange method, it can prevent external oxygen and impurities from entering the feed water to ensure that the oxygen content and water quality of the feed water do not change. The non-contact heat exchange method uses a cooler. After a small part of the feed water is pressurized by the feed water pump, it is led to the cooler through a branch pipe to be cooled by a certain temperature and then injected into the outlet pipe of the deaerator. At least one branch pipe with an electric control valve is provided in the pipeline after the cooler. The branch pipe with the electric control valve is used to adjust the cooling flow rate under variable working conditions, adjust the feed water temperature, and thus adjust the net positive suction head before the feed water pump. A branch pipe with a manual valve is also provided in the pipeline after the cooler to maintain the minimum flow rate to prevent cavitation of the feed water pump caused by misoperation or adjustment lag of the electric control valve.

2. The deaerating and cooling cavitation-resistant feed water system according to claim 1, characterized in that: The non-contact heat exchange method uses a cooler. A part of the high-temperature and high-pressure feed water at the outlet of the feed water pump flows through the cooler for heat exchange and cooling by a certain temperature and then is injected into the feed water header in front of the feed water pump to be mixed with the main feed water, so as to reduce the temperature of the feed water in the feed water header by a certain temperature. The mixed feed water is pressurized by the feed water pump and supplied to the subsequent steam generator or high and low pressure heaters.

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