JPS60125705A - Combined cycle power plant - Google Patents

Abstract

PURPOSE:To flow steam of a temperature corresponding to the temperature of the casing of a steam turbine by providing a high pressure superheater bypass pipe which bypasses an inlet and an outlet of a high pressure superheater through a steam flow quantity adjusting valve. CONSTITUTION:The high-pressure superheater bypass pipe 35 having a steam flow quantity adjusting valve 34 is provided from this side of the high pressure superheater 19 of a generated steam pipe 18 of a high pressure steam drum 16, and is joined with a high pressure main steam pipe 22 at the outlet of the heater 19. The flow quantity of high temperature steam passing through the heater 19 and that of low temperature steam bypassed through the heater 19 are adjusted and mixed by means of the adjusting valve 34, and it is possible to feed steam to the steam turbine 4 by mating the temperature of steam in the rear of the joined point of the bypass pipe 35 and the steam pipe 22 with the temperature of the casing of the steam turbine 4. As a result, the temperature difference between the temperature of the steam turbine and the temperature of steam at the time of starting the turbine 4 and at the time of the load variation of the gas turbine 2 is reduced thereby to reduce the generation of thermal stress of the casing and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a combined cycle power plant that generates driving steam for a steam turbine using exhaust gas from a gas turbine.

[Technical background of the invention and its problems]

FIG. 1 is a system diagram of a conventional combined cycle power generation plant, which includes an air compressor 1, a gas turbine 2, a gas turbine generator 3, a steam turbine 4, a steam turbine generator 5, and the like.

Air introduced into the air compressor 1 via the air supply pipe 6 is not compressed and enters the combustor 7, where it is mixed with fuel supplied from the fuel supply pipe 9 via the fuel control valve 8 and combusted. The combustion gas generated in the combustor 7 enters the gas turbine 2 via the connecting pipe 10, expands there, performs work, becomes exhaust gas, and is sent to the exhaust heat recovery boiler 12 via the exhaust gas pipe 11.

The exhaust gas sent to the exhaust heat recovery boiler 12 is extracted by a condensate pump 13, heats water fed through a water supply pipe 14 to generate steam, and is then released into the atmosphere through a chimney 15. The exhaust heat recovery boiler 12 has two steam drums, a high-pressure steam drum 16 and a low-pressure steam drum 17, and the high-pressure steam generated in the high-pressure steam drum 16 is sent to a high-pressure super heater 191 via a high-pressure drum generation steam pipe 18.
=Feed high pressure steam stop valve 20 and high pressure steam control valve 21
Air is sent to the steam turbine 4 via a high-pressure main steam pipe 22 having a In addition, the low pressure steam generated in the low pressure steam drum 17 is passed through the low pressure super heater 23 to the low pressure main steam stop valve 2.
4 and a low pressure main steam pipe 26 having a low pressure steam control valve 25
In the steam turbine 4, the high-pressure main steam and low-pressure main steam pass through each stage, expand, perform predetermined work, and then are discharged to the condenser 27.

This exhaust steam is condensed into condensate in the condenser 27, and then extracted by the condensate pump 13 and sent to the exhaust heat recovery boiler 12.

In such a combined cycle power generation plant, the gas turbine 2 is operated before the steam turbine 4, and the steam turbine 4 is driven by the steam generated by the exhaust gas of the gas turbine 2. This is a dependent relationship, and the temperature of the steam generated in the exhaust heat recovery boiler 12 is determined by the exhaust gas temperature of the gas turbine, and this exhaust gas temperature is characterized by being influenced by the load of the gas turbine. Therefore, when the steam turbine is started or when the load on the gas turbine changes, the steam turbine 4 is forced to operate quite harshly. That is, even when the steam turbine 4 is in a cold state, as shown in FIG.
A high-pressure bypass pipe 2 equipped with a high-pressure bypass valve 28 between
9 and a low-pressure bypass pipe 31 having a low-pressure bypass valve 30, and the temperature of the high-pressure main steam is maintained at a high temperature. In such a case, when grand steam is supplied to the turbine via the turbine grand steam pipe 33 branched from the high-pressure main steam pipe 22 and having the turbine ground steam supply valve 3L, the rotor and casing of the steam turbine 4 are Due to the steam, it heats up rapidly and generates large thermal stress. Furthermore, when high-temperature steam is vented to the cold steam turbine 4 through the high-pressure main steam stop valve 20 and the high-pressure steam control valve 21, the casing is rapidly heated and large thermal stress is also generated. Furthermore, even when the steam turbine 4 is in operation, the temperature of the steam flowing into the steam turbine 4 changes greatly as the load on the gas turbine 2 changes, and gauging of the steam turbine 4 has a relatively large heat capacity, so the temperature of the casing and the steam This creates a temperature difference that causes the casing to heat up or cool down rapidly, resulting in large thermal stresses that can cause cracks in the components of the casing.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide a combined cycle power generation plant that can flow steam at a temperature corresponding to the casing temperature at the time of startup or operation of the steam turbine to the steam turbine. .

[Summary of the invention]

In order to achieve the above object, the present invention is characterized by providing a high-pressure superheater bypass pipe that bypasses the inlet and outlet of the high-pressure superheater via a steam flow rate regulating valve.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. In FIG. 2, the same parts as those shown in FIG. 1 are designated by the same reference numerals, and the explanation thereof will be omitted.

As shown in FIG. 2, the present invention provides a high-pressure superheater bypass pipe 3 having a steam flow rate regulating valve 34 from the generating steam pipe 18 of the high-pressure steam drum 16 before the high-pressure superheater 19.
5 is provided to join the high pressure main steam pipe 22 at the outlet of the high pressure super heater 19.

The present invention is configured as described above, and the steam flow rate adjustment valve 34 adjusts and mixes the flow rate of high temperature steam that has passed through the high pressure superheater 19 and the flow rate of low temperature steam that is obtained by bypassing the high pressure superheater. As a result, the steam temperature after the confluence of the high-pressure superheater bypass pipe 35 and the high-pressure main steam pipe 22 can be made to match the casing temperature of the steam turbine 4 and can be supplied to the steam turbine 4, and the steam turbine 4 can be started. By reducing the temperature difference between the casing temperature of the steam turbine and the steam temperature when the load of the gas turbine 2 changes, the generation of thermal stress in components such as the casing can be significantly reduced.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to supply steam at a temperature suitable for the casing temperature of the steam turbine, and therefore it is possible to prevent cranking due to excessive thermal stress in the casing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional combined cycle power generation plant, and FIG. 2 is a block diagram showing an embodiment of the present invention. 2... Gas turbine, 4... Steam turbine, 12...
...Exhaust heat recovery boiler, 19...High pressure super heater, 34...Steam flow rate adjustment valve, 35...High pressure super heater bypass pipe. Agent: Patent attorney Noriyuki Chika (one idiot)

Claims (1)

[Claims] In a combined cycle power generation plant in which exhaust gas from a gas turbine is sent to an exhaust heat recovery boiler, feed water is heated to generate high-pressure steam, and this high-pressure steam is sent to a steam turbine through a high-pressure super heater in the exhaust heat recovery boiler described in iii. A combined cycle power generation plant, characterized in that a high-pressure superheater bypass pipe is provided that bypasses the inlet and outlet of the high-pressure superheater via a steam flow rate regulating valve.