JPS60152991A - Purifier for condensate from steam turbine plant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention is directed to the prevention and treatment of corrosion products mainly composed of iron oxides generated on the inner surface of condensate system equipment and piping in a nuclear power plant, for example. Some of the substances are removed by the condensate purification system, but the rest flows into the reactor and is activated by neutron irradiation in the reactor core, where these pipes are destroyed by the reactor water that circulates within the reactor system. It migrates and adheres to the inner surfaces of equipment, and the amount of adhesion increases over time, increasing the radiation dose rate of the plant and increasing the exposure dose of conventional workers during periodic inspections.

For this reason, in order to suppress the inflow of corrosion products generated in the condensate system into the reactor, many boiling water nuclear power plants have conventionally installed a condensate demineralizer downstream of the main condenser. ing. However, in conventional boiling water nuclear power plant systems, high-temperature, high-pressure steam generated in the nuclear reactor is sent to the steam turbine through the main steam pipe, drives the turbine, and then is condensed in the main condenser. After dissolved air is extracted by an air extractor, it is sent through a condensate pipe to a condensate demineralizer whose purification section is filled with ion exchange resin.
Corrosion products mainly composed of iron oxides generated upstream are removed. The purified condensate is then pumped into a high pressure condensate pump.
The water is heated and pressurized again through the feedwater heater and feedwater pump, and then returned to the reactor.

On the other hand, more than 90% of the corrosion products that flow into the nuclear reactor are
This occurs upstream of the condensate purification system.
This has been revealed through actual machine testing. The main source of corrosion products generated upstream of the post-water purification system is the main condenser and condensate pipes made of carbon steel, and the structure is such that the generated corrosion products are removed by the condensate purification system. has been done. However, in actual covered water purification systems,
The removal rate of corrosion products is only about 50 to 70 inches,
The remaining 30-50 inches of corrosion products flow into the reactor.

For this reason, many attempts have been made to improve the removal rate in plants that employ condensate desalters in their condensate purification systems, but these efforts have resulted in an increase in secondary waste and a reduction in operator operating time. As a result, there is a need for a condensate purification system that generates less waste and is highly efficient in removing corrosion products.

[Purpose of the invention]

The purpose of the present invention is to suppress the generation of corrosion products, reduce the load on the condensate purification system, efficiently remove the generated corrosion products, and suppress the amount of waste generated for waste treatment. The present invention provides a condensate purification device for a steam turbine plant that reduces the load on the system.

[Summary of the Invention] The condensate purification device of the present invention for a hot steam turbine plant has an oxygen injection mechanism that supplies the oxygen concentration in the system water in the main condenser hotwell to a constant concentration, and It is characterized by having a high gradient electromagnetic filter and a condensate demineralizer connected in series as a condensate purification device downstream of the vessel.

Embodiments of the Invention] Hereinafter, a case where the present invention is applied to a steam turbine system in a nuclear power plant shown in the drawings will be described. In the drawing, high-temperature, high-pressure steam generated in a nuclear reactor 1 is sent to a turbine 3 through a main steam pipe 2, drives the turbine 3, is condensed in a main condenser 4, and is sent to a condenser pipe 6.
The water is sent to the condensate demineralizer 8 by the low-pressure condensate pump 7, then heated and pressurized again through the high-pressure condensate pump 9, feed water heater 10, and feed water pump 11, and then returned to the reactor 1.

Corrosion products mainly composed of iron oxides generated upstream of the post-water system are removed from the condensate demineralizer 8 filled with ion exchange resin.
However, the removal rate of corrosion products in the conventional condensate demineralizer 8 is only about 50 to 70%, and the remaining 30%
~50% of the corrosion products enter the reactor.

Therefore, in the present invention, since oxygen is extracted from the water condensed in the main condenser 4 in the air extractor 5, the concentration of dissolved oxygen becomes extremely low. It is set up. The injection nozzle 14 is provided underwater in the hot well 12 of the main condenser 4. This injection nozzle 14 dissolves oxygen sent from an oxygen supply source 17 such as an oxygen cylinder through an oxygen flow rate adjustment valve 15 into the condensate taken from the discharge side of the low-pressure condensate pump 7, It is connected to an oxygen dissolution tank 16 that can continuously supply high concentration dissolved oxygen water.

The dissolved oxygen concentration in the water in the hot well 12 of the main condenser 4 is controlled by an oxygen concentration control mechanism 13. The dissolved oxygen concentration in the water in the hot well 12 is measured by a dissolved oxygen concentration measuring device 18, and the output signal of this measuring device 18 is sent to a control circuit 19, which sends a signal to the oxygen flow rate regulating valve 15 to control the oxygen supply amount. Control the dissolved oxygen concentration in condensate to an appropriate range, for example 80 to 15 Qppb.
maintained within the range.

On the other hand, a high gradient electromagnetic filter 2 is installed downstream of the low pressure condensate pump 7.
0 is set. For example, the high gradient electromagnetic filter 20 has an applied magnetic field strength of 5 KG and a water line flow velocity of 300 to 600 r11/).
(The high gradient electromagnetic filter 20 is made to pass the entire flow of condensate.
A bypass piping 21 is provided in preparation for maintenance or failure of the high gradient electromagnetic filter 20, and a conventional condensate demineralizer 8 is provided in series downstream of the high gradient electromagnetic filter 20.

In the condensate purification device according to the present invention configured as described above, the oxygen concentration control mechanism 13 is adjusted to the operating width of the steam turbine 3.
Through the control operation, the dissolved oxygen concentration in the condensate is adjusted to an appropriate range. Most of the corrosion products generated in the condensate system are from the main condenser and condensate piping, which are mainly composed of carbon steel.

-1 Many studies have revealed that corrosion of carbon steel is highly dependent on dissolved oxygen concentration. The current concentration of dissolved oxygen in the water in the hot well 12 of the main condenser 4 is:
It is around 20 pI)b, and maintaining a higher concentration of dissolved oxygen in the water in the hot well of the main condenser is effective in suppressing corrosion. In tests using actual equipment, the effect of suppressing the generation of corrosion products by 30% or more was obtained.

-1 When the concentration of dissolved oxygen in the water in the main condenser hotwell 12 increases, the composition of the crystalline form of iron oxide, which accounts for most of the corrosion products in the condensate, changes as shown in Table 1 below. This was confirmed through tests using actual equipment.

Table 1 This change in the composition of the crystal form results in the removal of iron oxides by the high gradient electromagnetic filter and condensate demineralizer described below. It is well known that high-gradient electromagnetic filters generally have extremely good removal efficiency for ferromagnetic iron oxides. It also shows considerable removal efficiency even for paramagnetic iron oxides. Table 2 shows the results obtained using an actual machine regarding the removal efficiency of each crystal form of iron oxide by the high gradient electromagnetic filter. Table 2 also includes the results from the condensate demineralizer. It can be understood from these Tables 1 and 2 that the condensate purification apparatus according to the present invention has a great effect of removing corrosion products as shown in Table 3.

Table 2 Table 3 In the conventional condensate demineralizer 8 single-equipment condensate purification system, the condensate demineralizer requires backwashing and regeneration steps depending on the amount of corrosion products loaded. In order to improve the removal rate of corrosion products, the frequency of these steps must be increased. Therefore, the amount of waste liquid generated in the backwashing and regeneration processes increases, increasing the load on the waste treatment system. On the other hand, the amount of waste liquid generated from the high gradient electromagnetic filter used in the present invention is very small compared to the amount generated from the condensate demineralizer. Therefore, in the condensate purification apparatus according to the present invention, the amount is reduced to approximately 50% of that of the conventional system.

Although the embodiment shown in the drawings has been described with reference to its application to a condensate system of a nuclear power plant, it can also be applied to a steam turbine plant in which the nuclear reactor 1 in the drawings is used as a steam generator such as a boiler. .

【Effect of the invention〕

As described above, in the present invention, a mechanism is provided to control the oxygen concentration in the system water in the main condenser hotwell to a constant concentration, and a high gradient electromagnetic filter and a water demineralizer are connected in series to the condensate system. By providing this, it is possible to have a great effect on reducing corrosion products and reducing the amount of waste liquid generated.

[Brief explanation of the drawing]

The drawing is a system diagram showing an embodiment of a condensate purification device for a steam turbine plant according to the present invention. 1...Steam generator (nuclear reactor) 3...Steam turbine 4...Main condenser 8...Condensate demineralizer 10...Feed water heater ・, 12...Hot well 13 ... Dissolved oxygen control mechanism 14 ... Injection nozzle 15 ... Oxygen flow rate adjustment valve 16 ... Oxygen dissolution tank 17 ... Oxygen supply source
18...Dissolved oxygen concentration measuring equipment 9...Control circuit 2
0... High gradient electromagnetic filter 21... Bypass pipe

Claims (3)

[Claims] (1) In the condensate system of a steam turbine plant, a dissolved oxygen concentration control mechanism is installed to control the dissolved oxygen concentration in the system water in the hot well of the main condenser to a constant concentration, and a A condensate purification device for a steam turbine plant, characterized in that a gradient electromagnetic filter and a condensate demineralizer are installed in series. (2) The dissolved oxygen concentration control mechanism is equipped with an oxygen dissolving tank to which a portion of the condensate is introduced and an oxygen supply source that supplies oxygen into the dissolving tank. The steam turbine plant according to claim 1, characterized in that the supply amount is controlled and the high concentration dissolved oxygen water in the oxygen dissolving tank is injected into the main condenser hot well. Condensate purification equipment. (3) The condensate purification device for a steam turbine plant according to claim 1, wherein the steam turbine plant is equipment within a nuclear power plant.