阅读说明：本技术 高温气冷堆核电厂二回路系统除氧剂联氨的加药系统和方法 (Dosing system and method for oxygen scavenger hydrazine in secondary loop system of high-temperature gas cooled reactor nuclear power plant ) 是由 滕维忠 郭俊文 曹松彦 姚洪猛 孙雅萍 闫爱军 于 2019-11-06 设计创作，主要内容包括：本发明公开了一种高温气冷堆核电厂二回路系统除氧剂联氨的加药系统和方法,该系统包括设置在高压加热器出口管道上用于加联氨的给水加联氨装置,设置在蒸汽发生器入口管处监测溶解氧、联氨含量用于控制联氨加入量的取样监测装置；本发明能够在核电机组二回路不改变化学水处理药剂、仅改变联氨加药位置的情况下,最大限度的降低二回路给水系统的流动加速腐蚀速率；本发明还对二回路系统的取样位置做了改变,使所取样品更合理、更具代表性。(The invention discloses a dosing system and a dosing method for a deoxidizer hydrazine in a secondary loop system of a high-temperature gas cooled reactor nuclear power plant, wherein the system comprises a water supply and hydrazine adding device which is arranged on an outlet pipeline of a high-pressure heater and is used for adding hydrazine, and a sampling monitoring device which is arranged at an inlet pipe of a steam generator and is used for monitoring dissolved oxygen and hydrazine content and controlling the adding amount of the hydrazine; the invention can reduce the flow accelerated corrosion rate of the two-loop water supply system to the maximum under the condition that the chemical water treatment agent of the two loops of the nuclear power unit is not changed and only the hydrazine dosing position is changed; the invention also changes the sampling position of the two-loop system, so that the sampled product is more reasonable and representative.)

1. The utility model provides a charge system of two return circuit system oxygen-eliminating agent hydrazine of high temperature gas cooled reactor nuclear power plant which characterized in that: the device comprises a water supply and hydrazine adding device arranged on an outlet pipeline of a high-pressure heater and used for adding hydrazine, and a sampling and monitoring device arranged at an inlet pipe of a steam generator and used for monitoring dissolved oxygen and hydrazine content and controlling the hydrazine adding amount.

2. The chemical dosing system for the oxygen scavenger hydrazine in the secondary loop system of the high temperature gas cooled reactor nuclear power plant according to claim 1, characterized in that: the water supply and hydrazine adding device is a high-pressure dosing pump.

3. The chemical dosing system for the oxygen scavenger hydrazine in the secondary loop system of the high temperature gas cooled reactor nuclear power plant according to claim 1, characterized in that: the sampling monitoring device comprises a dissolved oxygen content detector and a hydrazine content detector.

4. The chemical adding method of the chemical adding system for the oxygen scavenger hydrazine in the secondary loop system of the high temperature gas cooled reactor nuclear power plant as claimed in any one of claims 1 to 3, is characterized in that: when the unit normally operates, only ammonia is added from the outlet main pipe of the condensate fine treatment device, hydrazine is added to the secondary loop system of the high-temperature gas cooled reactor nuclear power plant at the outlet of the high-pressure heater through the feed water and hydrazine adding device arranged on the outlet pipeline of the high-pressure heater, the feeding point of the outlet main pipe of the condensate fine treatment device is cancelled, the premature addition of the hydrazine is avoided, the oxidation-reduction potential of a water vapor system is prevented from being reduced, the effect of more effectively inhibiting the flow accelerated corrosion of the secondary loop system of the high-temperature gas cooled reactor nuclear power plant is achieved, and meanwhile, the main feed water entering the heat exchange pipe of the steam generator is oxygen; the dosing points of ammonia and hydrazine in the downcomer of the deaerator are used as standby during starting and stopping of the unit and abnormality; the method comprises the steps of adjusting the ammonia adding amount at a mother pipe at the outlet of a condensate fine treatment device by detecting the conductivity of feed water at the inlet of a deaerator, controlling the conductivity of the inlet of the deaerator to be within the range of 8.5-26.0 mu S/cm, and ensuring the pH value of a secondary loop system of a high-temperature gas cooled reactor nuclear power plant to be 9.5-10.0; the dissolved oxygen and the hydrazine content are monitored by the sampling monitoring device arranged at the inlet pipe of the steam generator, so that the hydrazine adding amount is adjusted, the dissolved oxygen content of the feed water entering the steam generator is less than 3 mu g/L, and the hydrazine content is 50-100 mu g/L.

Technical Field

The invention relates to the technical field of water chemistry working conditions of a high-temperature gas cooled reactor nuclear power plant, in particular to a system and a method for adding an oxygen scavenger hydrazine in a secondary loop system of the high-temperature gas cooled reactor nuclear power plant.

Background

The material of the steam generator of the high-temperature gas cooled reactor nuclear power unit comprises nickel-based alloy, which has certain sensitivity to oxygen and requires that the content of dissolved oxygen in main feed water entering the steam generator is less than 3 mug/L. The deoxygenation mode of the secondary loop water supply system of the nuclear power plant is thermal deoxygenation of a deoxygenator and chemical deoxygenation by adding hydrazine so as to ensure that the main water supply entering a steam generator does not contain oxygen.

However, hydrazine belongs to a reducing agent, and after the hydrazine is added, the oxidation-reduction potential of the two-loop water supply system is reduced, and the flow accelerated corrosion rate is increased; according to the operation experience of thermal power, a unit for removing oxygen by hydrazine is added, and after the hydrazine is stopped, the iron content of a water supply system is obviously reduced, and the scaling rate of a boiler is reduced.

Flow accelerated corrosion is a significant cause of nuclear power plant secondary loop system pipe failure and steam generator iron oxide deposition. The accelerated flow corrosion not only can cause the pipelines of the middle and low water supply systems of the second loop of the nuclear power station to be thinned and even to be leaked, but also can increase the migration of corrosion products of the water supply systems to the steam generator and deposit the corrosion products in the heat exchange tube of the steam generator, thereby influencing the heat exchange efficiency and the running safety of the unit.

The method for inhibiting the flow accelerated corrosion of the secondary loop steam system of the nuclear power station comprises the following steps: (1) the use of alloy steel containing chromium in an amount greater than 0.5% by mass is effective in suppressing FAC, but requires a large amount of capital. At present, no clear regulation is made for the nuclear power units at home and abroad. (2) The cyclic chemical treatment mode is changed from a water supply ammonia adding and hydrazine treatment mode to an ammonia adding and oxygen adding combined treatment mode, but because many parts (valves and pipes) of the nuclear power station contain nickel-cobalt alloy and have certain sensitivity to dissolved oxygen, at present, no nuclear power unit adopting the oxygen adding treatment mode in the cyclic chemical treatment mode exists internationally. (3) The addition of ammonia is increased, the pH value of a water vapor system is increased, the FAC rate of a part of water supply pipelines can be reduced to a certain degree, but the ammonia content in condensed water is high, so that the period of the condensed water fine treatment system running in an H/OH mode is greatly shortened, the regeneration cost is increased, and the discharge amount of regenerated waste liquid is increased. (4) The method uses a proper alkalizer, meets the requirements of improving the pH value of a water supply system, a condensate system and a hydrophobic system, generally needs to select the alkalizer with the steam-water distribution coefficient smaller than or close to 1, and the novel alkalizer commonly used in the pressurized water reactor nuclear power station at present basically belongs to organic amines such as ethanolamine, morpholine and the like. Compared with a secondary loop system of a pressurized water reactor nuclear power plant unit, the secondary loop system of the high-temperature gas cooled reactor nuclear power plant unit has obviously higher steam parameters, and the primary steam parameters of the high-temperature gas cooled reactor nuclear power plant unit are as follows: the temperature is 570 ℃ and the pressure is 14.3 MPa; main steam parameters of a pressurized water reactor nuclear power unit: the temperature is 270 ℃, and the pressure is 5.2 MPa. The organic amine alkalizer is easy to decompose at high temperature, so the organic amine is not suitable for a secondary loop system of a high-temperature gas cooled reactor nuclear power unit.

According to the analysis, the four ways of inhibiting the flow accelerated corrosion are not the best choice ways for the built high-temperature gas cooled reactor nuclear power unit. At present, the pH value of a water supply system can be controlled to 9.5-10.0 only by increasing the ammonia adding amount so as to inhibit the flow accelerated corrosion; at the same time, hydrazine is added to the feedwater system to ensure that the primary feedwater entering the steam generator is oxygen-free water.

The purpose of the two-loop system plus hydrazine is primarily to remove dissolved oxygen from the feed water entering the steam generator. The thermal decomposition of hydrazine is affected by temperature, pH, reaction time and catalyst, and studies have shown that the temperature at which hydrazine starts to decompose is about 200 ℃ and that complete decomposition can be achieved at about 350 ℃. The hydrazine oxygen removal effect and the oxygen removal speed are related to the temperature, the hydrazine oxygen removal speed increases along with the increase of the temperature, and the research shows that 100 mu g/L of dissolved oxygen can be removed within 0.83min at 205 ℃. The flow accelerated corrosion is related to the temperature, wherein the flow accelerated corrosion rate is the largest at about 180 ℃, for a high-temperature gas cooled reactor, the most obvious area of the flow accelerated corrosion is a medium-pressure water supply system and a low-pressure water supply system, the outlet water supply temperature of a high-pressure heater exceeds 200 ℃, and the flow accelerated corrosion rate of the area is obviously reduced. It is therefore contemplated that the flow accelerated corrosion of the two-circuit system may be reduced by varying the hydrazine addition location while ensuring that the feedwater entering the steam generator is oxygen-free water.

Disclosure of Invention

According to the chemical treatment process of the water supply of the nuclear power unit at home and abroad, the material and the direct-current working condition of the high-temperature gas cooled reactor evaporator, the invention aims to provide the chemical feeding system and the chemical feeding method of the deoxidant hydrazine of the two-loop system of the high-temperature gas cooled reactor nuclear power plant, under the premise of not changing the prior water supply ammonia and hydrazine chemicals, the flow accelerated corrosion problem caused by the ammonia supply to a water supply pipeline in front of the evaporator is eliminated by changing the chemical feeding position of the hydrazine on the one hand, and the flow accelerated corrosion of the water supply system pipeline and equipment is greatly reduced by ensuring that the main water supply entering a steam generator is oxygen-free water on the other hand, so that the deposition of corrosion products in a heat exchange pipe of the steam generator and.

In order to achieve the purpose, the invention adopts the following technical scheme:

the utility model provides a medicine system of two return circuit system oxygen-eliminating agent hydrazine of high temperature gas cooled reactor nuclear power plant, is used for adding the feedwater of hydrazine and adds the hydrazine device including setting up on high pressure feed ware export pipeline, sets up the sample monitoring device that is used for controlling the addition of hydrazine of monitoring dissolved oxygen content in steam generator inlet tube department.

The water supply and hydrazine adding device is a high-pressure dosing pump.

The sampling monitoring device comprises a dissolved oxygen content detector and a hydrazine content detector.

According to the dosing method of the dosing system of the deoxidant hydrazine of the secondary loop system of the high-temperature gas cooled reactor nuclear power plant, when a unit normally operates, only ammonia is added from the outlet main pipe of the condensate fine treatment device, hydrazine is added to the secondary loop system of the high-temperature gas cooled reactor nuclear power plant at the outlet of the high-pressure heater through the water supply and hydrazine adding device arranged on the outlet pipeline of the high-pressure heater, the hydrazine dosing point of the outlet main pipe of the condensate fine treatment device is cancelled, the phenomenon that the oxidation reduction potential of a water vapor system is reduced by adding hydrazine prematurely is avoided, the effect of more effectively inhibiting the flow accelerated corrosion of the secondary loop system of the high-temperature gas cooled reactor nuclear power plant is achieved, and meanwhile, the fact that main water supply entering a heat exchange pipe of; the method comprises the steps of adjusting the ammonia adding amount at a mother pipe at the outlet of a condensate fine treatment device by detecting the conductivity of feed water at the inlet of a deaerator, controlling the conductivity of the inlet of the deaerator to be within the range of 8.5 mu S/cm-26.0 mu S/cm, and ensuring the pH value of a secondary loop system of a high-temperature gas cooled reactor nuclear power plant to be 9.5-10.0; the dissolved oxygen and the hydrazine content are monitored by the sampling monitoring device arranged at the inlet pipe of the steam generator, so that the hydrazine adding amount is adjusted, the dissolved oxygen content of the feed water entering the steam generator is less than 3 mu g/L, and the hydrazine content is 50-100 mu g/L.

Compared with the prior art, the invention has the following advantages:

(1) the method of the invention cancels the hydrazine adding point of the outlet main pipe of the fine treatment mixed bed, and changes the hydrazine adding point to one point of the outlet pipeline of the high-pressure heater. When the unit normally operates, hydrazine is added only from a little point of the outlet of the high-pressure heater, so that the oxidation-reduction potential of the medium-pressure and low-pressure water supply system is improved, and the flow accelerated corrosion rate of the water supply system (the temperature is 130-200 ℃) is reduced.

(2) The newly improved hydrazine dosing point has the water supply temperature of 205 ℃, the reaction rate of hydrazine and dissolved oxygen is high, and the rapid decomposition of hydrazine is avoided.

(3) And a sampling point is arranged at the inlet of the steam generator and is used for monitoring the hydrazine dosing and the oxygen removal condition so as to ensure that the dissolved oxygen of the main feed water entering the steam generator is close to 0 mu g/L.

(4) The invention can reduce the accelerated corrosion rate of the flowing of the water supply system and ensure that the dissolved oxygen entering the steam generator meets the requirements under the condition of not changing the original water supply treatment agent.

Drawings

FIG. 1 is a schematic view of a dosing system of the present invention.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings and specific embodiments.

As shown in fig. 1, the secondary loop system of the high temperature gas cooled reactor nuclear power plant comprises a condenser 1, a condensate pump 2, a condensate fine treatment device 3, a primary low-pressure heater 4, a secondary low-pressure heater 5, a tertiary low-pressure heater 6, a deaerator 7, a water feed pump 8, a high-pressure heater 9, a steam generator 10, a high-pressure cylinder 11 and a low-pressure cylinder 12 which are connected in sequence, and the primary loop comprises a nuclear reactor 20, a helium fan 19 and a steam generator 10 which are connected in sequence. The water vapor flow of the secondary loop system of the high-temperature gas cooled reactor nuclear power plant comprises the following steps: the desalted water is supplemented into a condenser 1, the condensed water is conveyed to a condensed water fine treatment device 3 through a condensed water pump 2 for treatment, the treated condensed water is fed water and passes through an ammonia adding point 14, the pH value of the condensed water is increased, then the condensed water sequentially enters a first-stage low-pressure heater 4, a second-stage low-pressure heater 5, a third-stage low-pressure heater 6 and a deaerator 7, after heating and deaerating, the pH value of the fed water is unchanged at the moment, the dissolved oxygen content is reduced, the temperature is increased to about 180 ℃, then the fed water is conveyed to a high-pressure heater 9 through a feed water pump 8, hydrazine is added through a feed water hydrazine adding device 17 newly arranged on an outlet pipeline of the high-pressure heater 9 for chemical deaerating, the dissolved oxygen and the hydrazine content of the main fed water are monitored by a sampling monitoring device 18 arranged at an inlet pipe of a steam generator 10, the main fed water is gradually, after the steam is completely converted into steam, the steam enters the high-pressure cylinder 11 and the low-pressure cylinder 12 in sequence to do work, and the exhaust steam enters the condenser 1 again to circulate in a reciprocating mode.

As shown in figure 1, the chemical dosing system for the deoxidizer hydrazine in the secondary loop system of the high-temperature gas cooled reactor nuclear power plant comprises a water feeding and hydrazine adding device 17 which is arranged on an outlet pipeline of a high-pressure heater 9 and is used for adding hydrazine, and a sampling monitoring device 18 which is arranged at an inlet pipe of a steam generator 10 and is used for monitoring the content of dissolved oxygen and hydrazine and controlling the adding amount of the hydrazine.

In a preferred embodiment of the present invention, the feed water hydrazine adding device 17 is a high-pressure dosing pump.

As a preferred embodiment of the present invention, the sampling monitoring device 18 includes a dissolved oxygen content detector and a hydrazine content detector.

As shown in figure 1, according to the dosing method of the dosing system of the deoxidant hydrazine in the secondary loop system of the high-temperature gas cooled reactor nuclear power plant, when a unit normally operates, only ammonia is added from the outlet main pipe 14 of the condensate fine treatment device, hydrazine is added to the secondary loop system of the high-temperature gas cooled reactor nuclear power plant at the outlet of the high-pressure heater through the water supply and hydrazine adding device 17 arranged on the outlet pipeline of the high-pressure heater 9, the hydrazine dosing point 13 of the outlet main pipe of the condensate fine treatment device 3 is cancelled, the premature addition of hydrazine is avoided, the oxidation reduction potential of a water vapor system is reduced, the effect of more effectively inhibiting the accelerated corrosion of the flow of the secondary loop system of the high-temperature gas cooled reactor nuclear power plant is achieved, and the main water entering a heat exchange pipe of a; the dosing point 16 of ammonia in the downcomer of the deaerator 7 and the dosing point 15 of hydrazine are used as standby when the unit is started and stopped and is abnormal; the method comprises the steps of adjusting the ammonia adding amount at a mother pipe at the outlet of a condensate fine treatment device by detecting the conductivity of feed water at the inlet of a deaerator, controlling the conductivity of the inlet of the deaerator to be within the range of 8.5 mu S/cm-26.0 mu S/cm, and ensuring the pH value of a secondary loop system of a high-temperature gas cooled reactor nuclear power plant to be 9.5-10.0; the dissolved oxygen and the hydrazine content are monitored by the sampling monitoring device arranged at the inlet pipe of the steam generator, so that the hydrazine adding amount is adjusted, the dissolved oxygen content of the feed water entering the steam generator is less than 3 mu g/L, and the hydrazine content is 50-100 mu g/L.

The invention relates to a dosing system and a dosing method of a deoxidizer hydrazine in a secondary loop system of a high-temperature gas cooled reactor nuclear power plant, which only cancels a hydrazine adding point of an outlet main pipe of an existing condensate fine treatment device 3 in the secondary loop system of the high-temperature gas cooled reactor nuclear power plant without changing the type of a feed water treatment medicament and the original hydrazine dosing tank, adds the hydrazine adding point at an outlet of a high-pressure heater 9, and simultaneously uses a high-pressure dosing pump to only add hydrazine from one point of an outlet pipeline of the high-pressure heater 9, so that the flow accelerated corrosion rate of the feed water system can be reduced under the condition of not influencing the chemical deoxidization effect; meanwhile, a sampling point at the inlet of the steam generator 10 is added for monitoring the content of dissolved oxygen and hydrazine in the main feed water entering the steam generator 10, and controlling the amount of the hydrazine added to the feed water to ensure that the content of the dissolved oxygen in the main feed water entering the steam generator 10 is less than 3 mug/L.