JPS6015874B2 - Air extraction system for condenser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air extraction system for a condenser in a boiling water (8WR) nuclear power plant. The present invention relates to an air extraction system operating system that enables reduced operation.

The air extraction system of a normal boiling water nuclear power plant consists of a mechanical vacuum pump and a steam ejector type air extraction device, and the vacuum level of the condenser at plant start-up is increased by the procedure shown in Figure 1. Implemented by That is, B in Fig. 1 corresponds to 61 HgVac, which is the ultimate vacuum limit of a mechanical vacuum pump.
After that, the main air extractor is switched to and the vacuum is raised to a predetermined condenser vacuum degree D point. The main air extractor uses steam as its driving source, but immediately after switching from the mechanical vacuum pump, the steam pressure generated in the reactor is low and the steam cannot be used as the driving steam for the main air extractor. In-house steam from the plant is used. After that, the steam pressure generated in the Yoko furnace is kept at a constant pressure (approximately 20
When k9/ reaches (point C in Figure 1), the system is switched to the main steam system, driving steam is supplied, and operation is continued. The main air extractor is rated at 735 Hg assuming high vacuum during normal operation.
Since it is designed with the goal of securing a vacuum of about Vae, it has a two-stage steam ejector structure, and its operation inevitably consumes a large amount of driving steam. Therefore, using the main air extractor during low vacuum operation (between B and C in Figure 1) immediately after switching from a mechanical vacuum pump requires the supply of a large amount of driving steam as in normal operation, and This had the disadvantage of increasing the capacity of the boiler equipment. FIG. 2 shows an improvement plan of the prior art used to improve these drawbacks. That is, in the improvement plan shown in Figure 2,
This method provides a dedicated start-up air extractor that is used between the operation of the mechanical vacuum pump and the operation of the main air extractor. The startup air extractor has a structure that allows it to operate with a small amount of driving steam in the low vacuum operating range. However, even in this method, even if the consumption of driving steam is reduced in the low vacuum operating range, there are drawbacks such as not only the need for an additional start-up air extractor but also the expansion of the installation space. An object of the present invention is to eliminate the drawbacks of the prior art described above by configuring a system in which only the second stage steam ejector of a main air extractor consisting of two stage steam ejectors is operated in a low vacuum operating range. Provides an air extraction system.

The maximum vacuum possible with a single stage steam ejector is about 70 HgVac. Therefore, the main air extractor, which needs to ensure a high degree of vacuum, is composed of a two-stage steam ejector. FIG. 3 shows an example of pressure distribution in the first and second stage steam ejectors of the main air extractor.

That is, in the first stage steam ejector, Hg on the suction vacuum 735 side
The pressure distribution is designed to be approximately 635 HgVac from Vac, and the pressure distribution in the second stage steam ejector is from 635 HgVac to the main air extractor outlet back pressure. Therefore, condenser vacuum (main air extractor suction vacuum) 635 side Hg
Vac level, vacuum can be secured by operating only the second stage steam ejector without using the first stage steam ejector.

FIG. 4 shows the system configuration around the steam ejector when a conventional starting air extractor is installed.

That is, in the conventional type, there is one set of the normally used first stage steam ejector IA and the second stage steam ejector 2A for the main air extractor, and a spare first stage steam ejector in addition to the normally used one in case trouble occurs with the normally used steam ejector. IB, second stage steam ejector 28
One set is provided.

Furthermore, a set of steam ejectors, a first stage steam ejector 3 and a second stage steam ejector 4, is also provided in the startup air extractor. Here, the startup air extractor is also equipped with a two-stage steam ejector, so that the condenser vacuum can be reduced to 700 mHgV when the plant is stopped other than when the plant is started.
This is because it is possible to cope with an operation case in which the temperature is maintained at a temperature higher than c. The main air extractor is connected to the main steam supply system 8 through driving steam source valves 5, 6, and 7, each of which is provided one for each set of steam ejectors, for supplying driving steam to the steam ejectors. On the other hand, the startup air extractor is connected to the in-house steam supply system 10, and each supply system 8, 10 is provided with a system source valve 9, 11 to switch between the main air extractor and the startup air extractor. is possible. FIG. 5 shows the system configuration around the steam ejector when starting operation is performed from outside the second stage steam ejector without providing the starting air extractor according to the present invention.

In other words, only one set of regular first stage steam ejector IA and second stage steam ejector 2A for the main air extractor outside the steam exhaust and one set of spare first stage steam ejector IB and second stage steam ejector 2B are used. It is configured. Independent drive steam source valves 5A, 58, 6A, and 6B are provided at the inlet of each steam ejector, and by switching these source valves, as shown in FIG. 6, the second stage steam is activated during startup operation. Ejector 2A, 2B
It is possible to operate the first stage steam ejectors IA, IB and the second stage steam ejectors 2A, 2B during regular operation. According to the embodiment of the present invention, there is no need to install a starting air extractor unlike the secondary technology, and the amount of driving steam consumed during starting operation is limited to the operation of the second stage steam ejectors 2A and 2B. It is almost the same as when operating with an extractor.

Furthermore, since a starting air extractor is not required, the configuration of the driving steam supply system becomes extremely simple, which greatly contributes to simplifying the operating procedures and reducing the equipment space.

According to the present invention, it is possible to operate with low consumption of driving steam by operating only the second stage steam ejector of the main air extractor during startup operation, without installing a startup air extractor exclusively for startup operation. Become.

In addition, since a startup air extractor is not required, the system configuration and operation are simplified, and equipment space can be reduced.

[Brief explanation of drawings]

Figures 1 and 2 are condenser vacuum characteristic diagrams at startup of a conventional plant, Figure 3 is a pressure distribution diagram of the main air extractor steam ejector, Figure 4 is a system diagram of the conventional air extraction system, and FIG. 5 is a system diagram of the air extraction system of the present invention, and FIG. 6 is a condenser vacuum characteristic diagram at the time of plant start-up of the present invention. IA... Main air extractor 1st stage steam ejector (regular use), IB... Main air extractor 1st stage steam ejector (
2A...Main air extractor 2nd stage steam ejector (regular use), 2B...Main air extractor 2nd stage steam ejector (spare), 3... Startup air extractor first stage steam ejector, 4... Startup air extractor second stage steam ejector, 5... Regular steam ejector drive steam source valve for main air extractor, 6... Main Spare steam ejector drive steam source valve for air extractor, 7... Steam ejector drive steam source valve for startup air extractor, 8... Main steam supply system, 9... Main steam supply system source valve , 10... Station steam supply V supply system, 1 1... Station steam supply V supply system main valve. Game fungus 2 countries 3 causes Figure 4 〆J figure Gyo cause

Claims (1)

[Claims] 1. In a two-stage steam ejector type air extractor of a condenser air extraction system of a power generation plant, a steam system for supplying steam to the steam ejector is provided so that only the first stage steam ejector can be operated independently. This is an air extraction system for a condenser.