JPS58202311A - Cooling system of steam turbine - Google Patents

Abstract

PURPOSE:To spread use of a low priced material, by cooling necessary parts with low temperature steam in order to effectively use an expensive heat resistant material for a turbine casing, rotor shaft, blade, etc. in a turbine plant of superhigh temperature and pressure steam. CONSTITUTION:An extraction line 32 is provided from the half way point of a bolier heater 23 in a cooling system of a steam turbine and connected to a superhigh temperature and pressure turbine 2, and a conduit 33, connecting a path between an exhaust line of the superhigh temperature and pressure turbine and the first stage reheater 3 to the turbine 2, is provided. Feed water 20 flows in through a boiler economizer 21 and evaporation pipe 22 to become steam and its temperature is gradually increased by the heater 23. Accordingly, extraction is performed from the heater 23 at temperature below exhaust temperature of the superhigh temperature and pressure turbine, and high pressure steam at low temperature can be obtained, then this steam flows in through the line 32 and is guided to the turbine 2, thus necessary parts are cooled. The steam, after this cooling, flows in through the conduit 33 and is mixed in exhaust of the superhigh temperature and pressure turbine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steam turbine plant, and more particularly to a steam turbine cooling system that generates cooling steam suitable for cooling steam turbine high-temperature structures.

In response to the unstable supply and rising prices of petroleum-based fuels, coal-fired power is becoming the mainstream for newly built thermal power plants. but,
Compared to oil-fired power, coal-fired power requires a large amount of power from auxiliary equipment such as coal pretreatment systems and exhaust gas treatment systems, and has the disadvantage of lower net power transmission efficiency. Consequently, efforts are being made to improve the efficiency of the steam Tachin plant by improving the steam conditions.

For example, in the United States, gngeneerin is
gAssessment of anAjvanced
pulverized -Coal power p
int (project 1403) is being performed.

Improving the steam conditions of the steam turbine, that is, increasing the temperature and pressure, is achieved by installing an ultra-high-temperature, high-pressure turbine in addition to the normal plant configuration. A typical plant configuration example of an ultra-high temperature, high pressure steam turbine plant will be explained with reference to FIG.

In a normal supercritical pressure steam plant, a boiler 1, a high pressure turbine 4, a reheater 3, an intermediate pressure turbine 6, a low pressure turbine 7, a generator 8, a condenser 9, a low pressure feed water heater 10, 11, 12,
13, 14, a deaerator 15, a water supply pump 16, and a high-pressure feed water heater 17, 18, and 19. By installing a 2ft ultra-high temperature and high pressure turbine, the water supply and the flow of water at once will be as follows.

The ultra high temperature and high pressure steam that comes out of the boiler 1t passes through the main steam pipe 21 and enters the ultra high temperature and high pressure turbine 2 to generate power.
It is used to heat the pressure feed water heater 19, but most of it is heated in the first stage reheater 3, and then enters the high pressure turbine 4 to generate power. The steam leaving the high pressure turbine 4 is heated in the second stage reheater 5 and then enters the intermediate pressure turbine 6 to generate power. The steam leaving the intermediate pressure turbine 6 enters the low pressure turbine 7 to generate power and becomes condensed water at the condensate ti9. Ultra high temperature high pressure turbine 2
, the high-pressure turbine, the intermediate-pressure turbine 6, and the low-pressure turbine 7 generate power, which drives a generator 8t to generate electric power. The feed water coming out of the condenser is sent to the low pressure feed water heater 10, 11゜12.1
3 and 14, the water is heated by oil and steam from medium-pressure and low-pressure turbines, degassed by a deaerator 15, and boosted to a predetermined pressure by a water supply pump 16.

The high-pressure feed water coming out of the feed water pump 16 is sent to a high-pressure feed water heater 17.
At 18.19, the water is further heated by the ultra-high pressure and bleed steam of the high pressure turbine and enters the boiler 1 as boiler feed water 20. In the boiler 1, water is supplied to the boiler 1 nomizer 21. It passes through the evaporation tube 22 and superheater 23 and becomes ultra-high temperature and high pressure steam.

In such an ultra-high-temperature, high-pressure steam turbine plant, the turbine casing, rotor shaft, blades, etc. of the ultra-high-temperature, high-pressure turbine 2 require heat-resistant and pressure-resistant strength in the rounded shape in an atmosphere of high-temperature, high-pressure steam.
F containing i and compounded with reinforcing element X such as Ma and Ti
E-based and Ni-based heat-resistant superalloys are being developed, and austecite stainless steel is also being put into practical use as a heat-resistant material.

However, these heat-resistant materials are expensive and generally have poor workability and weldability in proportion to high-temperature strength, resulting in an increase in plant costs.

Therefore, in order to minimize the use of expensive heat-resistant materials, cooling with low-temperature steam was considered. FIG. 2 is a diagram showing a typical example of the ultra-high-temperature and high-pressure turbine 2. The ultra-high-temperature and high-pressure turbine includes a main steam pipe 21, an exhaust pipe 22, a rotor shaft 25, a high-pressure casing 26, a low-pressure casing 27, a nozzle box 28, and a cooling steam Discharge pipe 23, turbine nozzle blade row 29
, packet blade row 30, main steam pipe cooling passage 31. It is composed of a balance hole 24. High-temperature, high-pressure steam generated in boiler l is introduced into main steam pipe 21 and nozzle box 28, passes through turbine nozzle blade row 29 and packet blade row AOT, moves turbine rotor shaft 25, reduces temperature and pressure, and is exhausted. The pipe 22 is discharged to the outside of the turbine. If an expensive heat-resistant material is used for the high-pressure casing 26, the amount of violet used will be enormous, so it is generally considered that a space is provided between the high-pressure casing 26 and the low-pressure casing 270 to cool the exhaust steam tUt, which is relatively low temperature. . Although this limits the use of expensive refractory materials, the exhaust steam may not be sufficiently cold and may not be sufficiently cooled. In particular, extremely high temperature and high pressure steam flows in the main steam pipe 21, and it is necessary to flow steam with sufficient cooling capacity in the main steam pipe cooling passage.

9. Because the pressure of the steam after depreciation decreases, it cannot be returned to the turbine exhaust and cannot be used for high-pressure turbines. There is also the disadvantage that it decreases.

The purpose of the present invention is to provide a steam turbine for ultra-high-temperature, high-pressure steam turbine plants that effectively uses expensive heat-resistant materials, expands the use of less expensive conventional materials, and minimizes deterioration in plant efficiency. Our mission is to provide cooling systems.

The conditions for the cooling steam of an ultra-high-temperature, high-pressure turbine are ultra-high temperatures.
The exhaust pressure of the pressure turbine is high, and it is necessary to maintain an allowable temperature difference due to thermal stress. In order to satisfy this condition, the present invention focuses on the use of steam in the middle of the boiler superheater, which has a pressure equal to or higher than that of the main steam, and has a lower temperature, or steam generated in a separately installed superheater. Construct a lineage and mourn. These cooling steams are not superheated, there is no heat loss, they are superheated during cooling, and the pressure after cooling is high enough that they can be mixed into the ultra-high temperature and high pressure turbine exhaust compared to when there is no cooling. This makes it possible to minimize the drop in efficiency.

Hereinafter, a steam turbine cooling system which is an embodiment of the present invention will be explained with reference to FIG.

The difference between Fig. 3 and the typical plant configuration example of the ultra-high temperature and high pressure steam turbine plant shown in Fig. 1 is that the boiler superheating tm23
A pipe line 33 connects the bleed air line 32 to a point in the middle of , connects the bleed line to the ultra high temperature and high pressure turbine 2, and connects the ultra high temperature and high pressure turbine exhaust, the 111th stage reheater 3, and the ultra high temperature and high pressure turbine. This is because we have established the following. The feed water 20 passes through the boiler economizer 21° and the evaporation tube 22, where it becomes steam and is superheated 1.
i) The 28th shaft is gradually closed. In addition, since the superheater 23 has a bleed-off property at a temperature below the ultra-1N16m high-pressure turbine exhaust temperature, it is possible to obtain high-pressure steam at low temperature, and this steam is passed through the bleed line 32. ′
All four necessary parts are cooled to the ultra-high temperature and high pressure turbine through the

By cooling, the temperature of the cooling steam is raised and a sufficient pressure f higher than the exhaust steam pressure can be maintained, so the pipe 33 ,,
The steam after O cooling is mixed into the ultra-high temperature and high pressure turbine exhaust through the pipe 33t.

According to the invention, a cut fit can be obtained by installing steam suitable for cooling an ultra-high-temperature, high-pressure turbine by installing a pipe line with a lower temperature than the main steam without installing special equipment. be.

Another embodiment of the invention is shown in Figure tR4. The difference between Fig. 4 and Fig. 3 is that the exhaust gas of the ultra-high temperature and high pressure turbine 2 and the
A control valve 36t is installed in the middle of the steam pipe 33 connecting between the stage reheater 3 and the ultra-high-temperature/high-pressure turbine cooling steam exhaust hole, and the ultra-high-temperature/high-pressure turbine cooled structure temperature measuring device 34 is used to measure the temperature of the ultra-high-temperature/high-pressure turbine cooled structure. The temperature of the cooling structure is sequentially measured and the signal is given to the control device 35, which controls the control valve 36 ([-
It is to drive.

According to the present invention, the amount of cooling steam can be sequentially controlled by 6J, and the thermal stress of the structure to be cooled can be minimized by Δ.

In the embodiment shown in FIG. 5, the steam for cooling the ultra-high temperature and high pressure turbine 2 is not obtained from the middle of the superheater 23, but is separated from the boiler water supply system by 37'fr of cooling steam supply water, and is installed in the boiler by a cooling steam generation system. 3B, and ultra-high temperature and high pressure steam is supplied to the turbine 1' through a cooling steam supply pipe 39. In this embodiment, the cooling steam generation system 38' is provided in the main steam generation boiler, but this does not have a limited meaning, and if there is another effective heat source, that heat source can be widely used. It is.

According to the present invention, when there is an excessive heat source in a boiler or the like, cooling steam can be generated by using the heat source, and heat can be effectively utilized.

The difference between the embodiment shown in FIG. 6 and the embodiment shown in FIG. 5 is that a control valve 42 is provided in the cooling steam water supply system 37, and the temperature signal from the ultra-high temperature ^-pressure turbine cooled structure temperature measurement device 40 is The control device 41 is configured to drive the control valve 42.

According to the present invention, since the amount of cooling steam can be sequentially controlled, it is possible to reduce the amount of cooling steam and to minimize the occurrence of thermal stress in the structures to be cooled in the ultra-high temperature and high pressure turbine.

FIG. 7 shows an embodiment of the present invention in an ultra-high-temperature, high-pressure turbine.The structure differs from the ordinary ultra-4B vertical high-pressure turbine shown in FIG. 2 in that the outer casing 26 and the inner casing 27f: The turbine exhaust is isolated from the space formed by the outer casing 26 and the inner casing, and the cooling steam is introduced into this space through the cooling steam supply pipe 43. It is applicable in Since the cooling steam is at a low temperature and has a higher pressure than the turbine exhaust, the turbine exhaust does not flow into the cooling steam side, and the steam after cooling can mix with the turbine exhaust.

According to the present invention, it is possible to effectively cool the internal structure of a steam turbine, and even by using relatively low-grade heat-resistant steel, sufficient reliability can be obtained in terms of strength. Since it is possible to generate and use steam at an appropriate temperature in advance, there is less deterioration in plant efficiency compared to cooling steam obtained by lowering the temperature of the main steam. 5
7 effects.

[Brief explanation of the drawing]

Figure j11 is a system diagram showing a typical example of an ultra-high-temperature, high-pressure steam turbine plant, Figure 2 is a sectional view of an ultra-high-temperature, high-pressure turbine, and Figure 3 is a steam turbine system diagram that is an embodiment of the present invention. FIG. 6 is a steam turbine according to another embodiment of the present invention, and FIG. 6 is a sectional view of a steam turbine section to which the present invention is applied.

Claims (1)

[Claims] 1. In a steam turbine plant consisting of a boiler, a steam turbine, a condenser, a feedwater pump, a feedwater heater, etc.,
A steam turbine cooling system characterized in that steam flowing through a steam system branched from the middle of a superheater in a boiler is used to cool components inside the steam turbine. 2. Permitted Claims Claim 1: A steam turbine cooling system characterized in that a control valve tf& is installed in a steam system branched from the middle of a superheater, and the control valve is controlled by the temperature of a cooled structure inside the steam turbine. 3. According to claim 1, a space independent from the turbine exhaust is formed between the outer casing and the inner casing of the steam turbine, cooling steam is passed through the space, and the cooled steam is mixed with the turbine exhaust. A steam turbine cooling system characterized by: 4. In a steam turbine plant consisting of a boiler, steam turbine, condenser, feed water pump, feed water heater, etc.
The cooling steam system, which is multi-branched from the boiler feed water system, is guided to the feed water t boiler to produce superheated steam, whose superheated steam temperature is lower than the superheated steam in the main system, and the low temperature superheated steam is transferred to the internal structure of the steam turbine. A steam turbine cooling system characterized by its use in cooling. 5. Patent a) In Section 4 of ICms, a control valve is provided in the cooling steam system separated from the boiler feed water system, and the control valve t
- A steam turbine cooling system characterized in that the system is controlled by the temperature of a cooled structure inside the steam turbine.