JPS627904A - Electric power plant system - Google Patents

Abstract

PURPOSE:To avoid using highly moist steam which is a factor in pipe corrosion, so as to enable economical carbon steel to be used by building a system in order to use reheated steam drawn out immediately from the way-out of a reheater as a source of heated steam supply of a water supply heater. CONSTITUTION:In the case of a reheating-type atomic power plant, highly moist steam which makes work in a high pressure turbin 2, is made free from moisture through a moisture separator 3, then reheated by the first-step and the second-step reheaters 12a, 12b, and flows into a low pressure turbine 4. Then, the air drawn out of the high pressure turbine 2 is supplied as heating steam 14b for a high pressure water supply heater 11b, and so is super-heated steam in the way-out of the second-step reheater 12b as heating steam 14a for a high pressure water supply heater 11a. Similarly, the air drawn out of a low pressure turbine 4 is supplied as heating steam 13a-13d for low pressure water supply heaters 9a-9d. Factors in pipe corrosion are excluded by the above mechanism, and carbon steel can be used for piping and the cost of equipment can be reduced.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a power generation plant system, and particularly relates to a power generation plant system.

The present invention relates to a feed water heating system rIItvc that avoids the cause of wall thinning and has a low equipment cost in a nuclear power plant system equipped with a moisture separation heater.

[Background of the invention]

Conventional BWR nuclear power plant systems are standard non-reheat plants equipped with only a moisture separator, and this configuration is shown in FIG. That is, in a non-reheating plant, as shown in Figure 3, steam from a nuclear reactor 1 that generates steam flows into a high-pressure turbine 2, and by doing work in the high-pressure turbine 2, the moisture in the steam is removed. Exhausted with increasing minutes. The high-humidity steam exhausted from the high-pressure turbine 2 flows into the moisture separator 3, where the moisture is separated, and the steam with high retained energy flows into the low-pressure turbine 4, where it sequentially performs work. At the same time, it is exhausted to the condenser 5. The turbine exhaust gas that has flowed into the condenser 5 is condensed and becomes condensate, and the condensate pump 6Vc
It then flows through an air extractor 7 and a gland steam condenser 8 to a low-pressure feedwater heating device 9. Low pressure feed water heating device H9a~9
It is composed of a four-stage feedwater heater (d), and is pressurized by the condensate drain from the low-pressure feedwater heating device, and then by the reactor feedwater pump 1O, and is pumped to the high-pressure feedwater heating device fiiel 1.

The high-pressure feedwater heating device 11σ11a is composed of a two-stage feedwater heater of 1 lb, and the feedwater heated to the final feedwater temperature by the high-pressure feedwater heating device is supplied to the nuclear reactor 1 to form a plant cycle.

Heating of condensate and feedwater in the high-pressure and low-pressure feedwater heaters is performed by extracted steam from the high-pressure and low-pressure turbines, and these conditions are shown in the i-s diagram in Figure 4 in comparison with a thermal power plant system. .

The major difference in the bleed steam conditions for feedwater heaters is that in thermal power plants, all bleed air except for the lowest pressure membrane bleed air is superheated steam, whereas in non-reheat nuclear power plants, all bleed air is wet steam. That's true.

In other words, the fact that all the oil is wet steam is the main cause of thinning on the side of the feedwater heater shell and in the bleed pipe between the turbine and the feedwater heater, which is why carbon steel can be used in thermal power plants. However, nuclear power plants are forced to use high-grade materials such as low-alloy steel or stainless steel, leading to extremely high equipment costs.

[Purpose of the invention]

An object of the present invention is to provide a feed water heating device that avoids the use of steam with high humidity, which is a cause of wall thinning, allows the use of economical carbon steel materials, and greatly reduces equipment costs. It is in.

[Summary of the invention]

At nuclear power plants, a large number of thinnings have occurred in equipment and piping made of carbon steel, and a detailed investigation of the location of the thinning and the operating environment revealed that it was an erosion/corrosion phenomenon in a corrosive environment. became clear. That is, various investigations and studies have revealed that the cause of thinning is a complex relationship between corrosion factors and erosion factors.

Figure 5 shows the influence of humidity among the factors that cause wall thinning, and shows the actual results of wall thinning in steam piping with low humidity up to drain pipes with humidity of 100. be. When the humidity level is 1.5 coefficient or lower, there is no case of thinning, but when the humidity level is about 2 mm or higher, thinning occurs almost uniformly.

Further, even at the same humidity level, there are cases where the thickness loss is large or small, and this difference occurs due to the relationship with operating temperature, flow rate, and other factors.

Figure 6 shows the effect of temperature, and experience has shown that wall thinning is greatest when the operating temperature is around 1501Z', and rarely occurs below 50C and above 230C. ing.

Therefore, in order to prevent thinning, it is effective to adopt a system configuration that can effectively avoid these factors.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows a 7-stem configuration in which a reheater is provided in the non-reheating nuclear power generation plan (K) shown in FIG. 3 to create a steam-heating nuclear power plant.

That is, work is done in the high-pressure turbine 2, and after the moisture is separated from the high-humidity steam in the moisture separator 3, it is further passed through the first-stage reheater 12a and second-stage reheater 12bg. It is reheated and flows to the low pressure turbine 4. In a normal nuclear power plant, the humidity of the inlet steam of the moisture separator 3 is 12 degrees, and the outlet steam is humid steam with a humidity of about 2 degrees.
2a and 220t)', and the second stage reheater 12b produces heated steam of about 268C.

On the other hand, heating steam 14b for the high-pressure feedwater heater 11b is supplied from the oil air of the high-pressure turbine 2, and then to the high-pressure feedwater heater 11a.
The superheated steam at the outlet of the second stage reheater 12b is supplied to the heated steam 14au for use. In addition, low pressure water heaters 98 to 9d
Heating steam 13a to 13d for use is supplied from the bleed air of the low pressure turbine 4.

FIG. 2 shows an i-s diagram of a turbine in a reheating nuclear power plant according to an embodiment of the present invention in comparison with a non-reheating nuclear power plant.

That is, as shown in Fig. 2, in a non-reheat nuclear power plant, all of the extracted air from the turbine is wet steam, and the highest humidity is at the final extraction point connected to the low-pressure feedwater heater 9a. 13 (y=13 in the figure).

In addition, in the case of a reheat nuclear power plant, both the KFI and the bleed air connected to the low-pressure feedwater heaters 9c and 9d are superheated steam), and the highest humidity is in the high-pressure feedwater heater 1.
1a. 12 channels of moisture separator inlet steam (
13 of the non-reheat nuclear power plant (y = 12%) in the figure.
There is not much difference from Q (138 in the figure). However, as in the present invention shown in FIG. 1, heating steam for the high-pressure feed water heater 11a is VC-directed from the inlet (point A) of the moisture separator 30 to the outlet (point B) of the second stage reheater 12b. Therefore, in the case of the reheat type, the highest humidity is the heating steam 14b for the high-pressure feed water heater 11b, and the humidity is 10 inches (y-10 inches in the figure) v
It can be reduced to c.

- The humidity and temperature of the steam have a major influence on the occurrence of thinning, and the humidity is 1.5 or more, and the temperature is 60C to 2.
Figure 5 shows that thinning phenomenon tends to occur in the 30C range.
It is shown in Figure 6. The range where this thinning is likely to occur is the second
In the figure, this is the range surrounded by diagonal lines (■■■■).

In other words, in the past, there was little awareness of the problem with the thinning phenomenon, and there was insufficient understanding of the thinning phenomenon.
The moisture separation type and the processing capacity of the reheater were made as small as possible, and although the difference was not substantial, there was a slight advantage in thermal efficiency, so even in reheating nuclear power plants, feed water heaters were used. Heating steam for 11a is supplied from point A of the moisture separation mold inlet. In contrast, the present invention provides a feed water heater ll
The purpose is to set the extraction point of heated steam for A to point B at the outlet of the reheater 12. As a result, although wet steam was conventionally supplied, according to the present invention, superheated steam can be used, and the cause of thinning can be eliminated.

〔Effect of the invention〕

According to the present invention, construction costs can be significantly reduced, and the same thinning phenomenon as in the feed water heater occurs in the piping that supplies heated steam to the feed water heater, making it possible to use carbon steel and reducing equipment costs. It becomes possible.

[Brief explanation of drawings]

Figure 1 is a nuclear power plant system diagram that is an embodiment of the present invention, Figure 2 is an i-s diagram of a nuclear power plant that is an embodiment of the present invention, and Figure 3 is a conventional nuclear power plant system. Figure 4 shows the i-
The s-diagram, FIG. 5 is a diagram showing the influence of thinning due to steam humidity, and FIG. 6 is a diagram showing the influence of thinning due to steam temperature. DESCRIPTION OF SYMBOLS 1...Nuclear reactor, 2...High pressure turbine, 3...Moisture separation type, 4...Low pressure turbine, 5...Condenser, 6...
...Condensate pump, 7.Air extractor, 8.Gland steam condenser, 9.Low pressure feed water heating device, 10..
Reactor feed water pump, 11... High pressure water pump, 12a
, 12b... reheater.

Claims (1)

[Claims] 1. Power generation equipped with a moisture separator for separating moisture in steam at the high-pressure turbine outlet and a reheater for heating the steam after moisture separation to a superheating range. A power generation plant system, characterized in that the system is configured such that reheated steam immediately after the outlet of the reheater serves as a heating steam supply source for the feedwater heating device.