JP2667699B2 - Single-shaft combined plant and start-up method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a single-shaft combined plant that supplies auxiliary steam to a steam turbine to start it, and in particular, avoids accidents due to a rise in temperature of the steam turbine at startup. The present invention relates to a single-shaft combined plant and a method for starting the same.

[Prior art] When starting a single-shaft combined plant in which a gas turbine, a steam turbine, and a generator are coaxially connected, conventionally, the gas turbine is rotated to some extent by an electric motor or a diesel engine, and air compression attached to the gas turbine is performed. The gas turbine is ignited after a required amount of air is supplied from the gas turbine to the gas turbine. However, when this starting method is adopted, an electric motor or the like for starting is required.

Therefore, in the prior art described in Japanese Patent Application Laid-Open No. 58-160502, the plant is started by rotating the steam turbine by introducing auxiliary steam into the steam turbine at the time of starting to rotate the gas turbine.

[Problems to be Solved by the Invention] In the prior art described in Japanese Patent Application Laid-Open No. 58-160502, the initial start-up of the plant is performed using auxiliary steam, and when the shaft rotation speed does not decrease after ignition of the gas turbine, the auxiliary steam is used. The supply to the steam turbine has been stopped. When the initial startup of the plant is performed using the auxiliary steam in this way, until the steam from the exhaust heat recovery device due to the exhaust heat of the gas turbine is sufficient to drive the steam turbine and is supplied to the steam turbine, The steam turbine will be idled by the gas turbine. However, when the steam turbine idles in this manner, the temperature inside the steam turbine may increase due to the stirring effect, particularly since the moving blade length of the last stage of the steam turbine is long, which may cause a dangerous operation state.

Furthermore, when the auxiliary steam is introduced into the steam turbine to perform the initial start-up of the plant, even if the auxiliary steam is simply introduced into the high-pressure turbine or the medium- and low-pressure turbines constituting the steam turbine, the steam piping of the plant equipment is Become complicated,
Further, there is a disadvantage that the strength design becomes difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a single-shaft combined plant that can suppress an increase in the internal temperature of a steam turbine when starting up the plant using auxiliary steam and that can easily design a piping.

Means for Solving the Problems The object is to provide a gas turbine, a steam turbine, and a generator coaxially connected by a connecting shaft, and an exhaust heat recovery device that recovers exhaust heat of the gas turbine to generate steam. With
The steam turbine includes a high-pressure turbine, a reheat type intermediate-pressure turbine to which steam discharged from the high-pressure turbine is heated by the exhaust heat recovery device, and a low-pressure to which exhaust steam of the medium-pressure turbine is supplied. A single-shaft combined plant comprising a turbine, when starting up the single-shaft combined plant, supplying auxiliary steam different from steam from the exhaust heat recovery device to the intermediate pressure turbine, The connection shaft is accelerated, and thereafter, the gas turbine is ignited, and the auxiliary steam to the intermediate pressure turbine is supplied to the high pressure turbine until steam from the exhaust heat recovery device due to exhaust heat of the gas turbine is supplied to the high pressure turbine. This is achieved by continuing the supply.

[Operation] At the time of starting the plant, the low-pressure turbine is cooled by the auxiliary steam until the steam for turbine driving is supplied from the exhaust heat recovery device, so that a dangerous operating state does not occur.

Further, since the steam turbine to be introduced at the time of starting the plant is a reheated medium-pressure turbine, it is not necessary to design piping and valves for high-pressure steam, and the configuration of the piping system is further simplified.

EXAMPLES Hereinafter, preferred examples of the present invention will be described with reference to the drawings.

FIG. 1 is a system configuration diagram of a single-shaft combined plant according to a first embodiment of the present invention. The gas turbine equipment 10, the reheat steam turbine 20, and the generator 25 are mechanically and directly connected uniaxially by the connecting shaft 9, and the steam generated in the exhaust heat recovery boiler 30 that recovers the exhaust gas heat from the gas turbine 10 is: The high-pressure steam pipe 51, the reheat steam pipe 55, and the low-pressure steam pipe 57 constitute the reheat-type steam turbine 20, a high-pressure turbine 21, a reheat-type intermediate-pressure turbine (hereinafter referred to as reheat turbine) 22, and a low-pressure turbine 23. To be supplied to Separately from this turbine drive steam supply system, the auxiliary steam header 70
Is connected to a reheat steam pipe 55 for introducing steam from the exhaust heat recovery boiler 30 to the reheat turbine 22 at an auxiliary steam pipe 71 having a steam shut-off valve 72. .

Here, when the plant is started, the auxiliary steam header is used.
Steam from 70 is reheated through auxiliary steam piping 71
To drive the reheat turbine 22 by applying energy. Due to the rotation of the reheat turbine 22, the gas turbine 10 and the generator 25, which are coaxially coupled thereto, also start rotating at the same time, and the compressor constituting the gas turbine 10
12 sucks the atmosphere and sends compressed air for combustion to the combustor 15. In this way, the rotation speed of the connecting shaft 9 rotating in the steam turbine 20 reaches a predetermined rotation speed, and after the ignition condition in the combustor 15 is satisfied, the fuel flow control valve 14 is slightly opened. Fuel is sent to the combustor 15 and ignited. Thereafter, the rotational speed of the connecting shaft 9 is controlled by adjusting the fuel flow rate adjusting valve 14, and after reaching the rated rotational speed, the load of the gas turbine is increased.

After ignition of the gas turbine, high-temperature exhaust gas is
The exhaust heat is discharged from the exhaust heat recovery steam in the exhaust heat recovery boiler 30, and high-pressure steam and low-pressure steam are generated. Until it is ready, turbine bypass operation will be performed. That is, the high-pressure steam generated in the high-pressure drum 31 passes through the superheater 32, the high-pressure main steam pipe 51, the high-pressure bypass pipe 61 having the high-pressure turbine bypass valve 62, and the low-temperature reheat steam pipe 54, and the exhaust heat recovery boiler. The reheated steam is reheated by a reheater 33 provided in 30 and discharged to a condenser 40 via a reheated steam pipe 55 and a medium-pressure turbine bypass pipe 63. The low-pressure steam generated by the low-pressure drum 34 is also heated by the low-pressure superheater 35 and discharged to the condenser 40 via the low-pressure steam pipe 57 and the low-pressure turbine bypass pipe 65.

While the turbine bypass operation is carried out in this way, and the steam generated in the exhaust heat recovery boiler 30 is not introduced into the steam turbine 20, the steam turbine 20 is passively controlled by controlling the number of revolutions by supplying fuel to the gas turbine 10. When no steam is supplied to the steam turbine 20 at this time, the internal temperature of the low-pressure turbine 23 composed of long blades in particular rises due to the stirring effect, resulting in a dangerous operation state. It is expected that. Therefore, in the present embodiment, the auxiliary steam used to increase the rotation speed of the connecting shaft 9 before ignition of the gas turbine is continuously supplied to the low pressure turbine 23 through the reheat turbine 22 in an amount required for cooling the low pressure turbine 23. The temperature rise inside the turbine 23 is suppressed.

As the supply period of the auxiliary steam, the exhaust heat recovery boiler 30
It suffices until the steam generated in the above is vented to the steam turbine 20, which is shown in FIG. Here, the control of the amount of auxiliary steam shown in FIG. 2, that is, the increase in the rotation speed of the shaft system at the start of the start and the securing of the amount of steam for cooling the steam turbine after ignition of the gas turbine, etc., are performed by adjusting the amount of steam to the reheat turbine 22. The reheating steam amount adjustment valve 56, which is installed from the beginning, performs this purpose.

In the above-described start-up process, the high-pressure turbine 21 idles in order to introduce steam into the reheat turbine 22, but this is performed by connecting the high-pressure turbine exhaust side and the condenser 40 to the valve 60.
During the above operation, the valve 40 is opened, and the internal pressure of the high-pressure turbine is kept at the same vacuum as that of the condenser to suppress the temperature rise. This is the high pressure turbine 21
Since the blade length is short, sufficient cooling is possible by such measures.

During the initial startup of the plant, auxiliary steam is supplied to the high-pressure turbine.
Even if it is introduced into 21, the object of rotating the connecting shaft and further increasing the speed can be achieved. However, in the present embodiment, the auxiliary steam is introduced into the reheat turbine 22 instead of the high-pressure turbine for the following reason, and the initial startup of the plant is performed.

1) When the auxiliary steam for initial starting of the plant is introduced into the high-pressure turbine 21, the auxiliary steam that rotates the high-pressure turbine 21 is guided through the low-temperature reheat steam pipe to the reheater in the exhaust heat recovery boiler. However, since the exhaust gas from the gas turbine is not introduced into the exhaust heat recovery boiler at this stage, the steam passing through the reheat steam pipe is a low-temperature steam that has worked in the high pressure turbine. It cannot be ventilated. Therefore, the low-temperature steam is discharged to the condenser through the intermediate-pressure turbine bypass pipe. Therefore, it is necessary to supply cooling steam to the low-pressure turbine from another system, which complicates the system and also requires control of the turbine bypass system before the gas turbine is ignited. Would.

2) In general, the auxiliary steam pressure is of the order of 10-20 kg / cm ^2, high-pressure steam pressure is about 100 kg / cm ^2. For this reason, when the auxiliary steam is supplied, the design of the main steam system piping and valves at a high steam pressure is required to be 5 to 10 times larger due to the relationship of the specific volume.

In this regard, in the case of the present invention that employs an auxiliary steam supply system to the reheat turbine 22, since the steam introduced into the reheat turbine 22 flows into the low-pressure turbine 23 as it is, another independent cooling steam is particularly used. There is no need to introduce it, and both system and operation control will be simple and reliable.

On the other hand, since the reheat steam pressure is selected to be around 20 kg / cm ² , it is almost the same as the auxiliary steam pressure, and the reheat steam system piping and valves do not need particularly large ones. An economical plant can be provided.

From the above, it can be understood how effective the method of introducing the auxiliary steam into the reheat turbine when the reheat / single-shaft combined plant is started by the steam turbine.

FIG. 3 is a configuration diagram of a single-shaft combined plant according to a second embodiment of the present invention. In this embodiment, when introducing the auxiliary steam into the reheat turbine 22, the auxiliary steam pipe 71 is directly connected to the reheat turbine 22 independently of the reheat steam pipe 55 from the exhaust heat recovery boiler 30. When the rotation speed of the steam turbine is increased before ignition of the gas turbine, and when the steam for cooling the low-pressure turbine is supplied, the control of the amount of auxiliary steam is performed by the regulating valve 73 provided on the auxiliary steam pipe 71. According to this embodiment, the same effect as that of the first embodiment can be obtained.

FIG. 4 shows that when the steam generated from the low-pressure steam drum 34 of the exhaust heat recovery boiler 30 can be used as the cooling steam for the low-pressure turbine 23 at the time of starting the plant, the low-pressure steam is replaced with the cooling by the auxiliary steam. Steam from drum 34,
FIG. 4 is a control explanatory diagram of an embodiment in which the steam is introduced into the low-pressure steam turbine 23 via a low-pressure steam pipe 57 and a valve 58. As described above, when the steam from the low-pressure steam drum 34 can be used for cooling, the supply of the auxiliary steam is stopped and the steam from the low-pressure steam drum 34 is used, so the auxiliary steam supply time is reduced. And economical operation becomes possible. Of course, when the steam from the exhaust heat recovery boiler 30 is supplied to the reheat turbine 22 and the reheat turbine 22 is driven by the steam (in this case, the exhaust steam from the reheat turbine 22 is Turbine 23
And no additional steam for cooling is required. ) The supply of the auxiliary steam to the reheat turbine 22 may be stopped.
Needless to say.

FIG. 5 is a configuration diagram of a single-shaft combined plant according to a third embodiment of the present invention. In the present embodiment, an auxiliary steam pipe 71 connecting the reheat turbine 22 and the auxiliary steam header 70 is provided.
A steam temperature controller 74 is provided in the middle of the process. By providing the steam temperature adjusting device 74 in this manner, at the time of initial plant startup with the introduction of auxiliary steam, the plant shutdown time before startup (the shutdown time can be viewed as a function of the plant cooling temperature) or at startup. Auxiliary steam temperature according to the plant startup mode classified by the turbine metal temperature can be realized, and more effective turbine startup is possible.

[Effects of the Invention] According to the present invention, the auxiliary steam flows from the intermediate-pressure turbine to the low-pressure turbine even after the initial startup of the plant to cool the low-pressure turbine, so that an abnormal operation state due to an increase in the temperature of the low-pressure turbine can be avoided. Safe plant startup with auxiliary steam can be realized. Moreover, since the auxiliary steam is supplied to the reheat turbine to start the plant, the piping system is simplified, and it is not necessary to increase the strength of the auxiliary steam pipes and valves, so that reliability is improved and cost is reduced. Has an effect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a single-shaft combined plant according to a first embodiment of the present invention, FIGS. 2 (a) and 2 (b) are explanatory diagrams according to an embodiment of auxiliary steam supply control, and FIG. Second of the invention
4 (a) and 4 (b) are explanatory diagrams of another embodiment of the auxiliary steam supply control, and FIG. 5 is a single-shaft type combined plant according to a third embodiment of the present invention. It is a block diagram of a combined plant. 10 ... Gas turbine equipment, 11 ... Gas turbine, 12 ...
Compressor, 13 ... Fuel pipe, 14 ... Fuel flow control valve, 15 ...
… Combustor, 20… Reheat steam turbine equipment, 21… High pressure turbine, 22… Reheat turbine, 23… Low pressure turbine,
25 ... generator, 30 ... waste heat recovery boiler, 31 ... high pressure drum, 32 ... superheater, 33 ... reheater, 34 ... low pressure drum,
35 …… Low pressure super heater, 40 …… Condenser, 51 …… High pressure steam pipe,
52 …… High-pressure steam control valve, 53 …… Reheat steam check valve, 54…
… Low-temperature reheat steam pipe, 55 …… Reheat steam pipe, 56 …… Reheat steam flow control valve, 57 …… Low pressure steam pipe, 59 …… Ventilator steam pipe, 60 …… Ventilator valve, 61 …… High pressure turbine Bypass pipe, 62… High pressure turbine bypass valve, 63… Medium pressure turbine bypass pipe, 64 …… Medium pressure turbine bypass valve, 65…
… Low-pressure turbine bypass pipe, 66… low-pressure turbine bypass valve, 70… auxiliary steam header, 71… auxiliary steam pipe, 72
…… Auxiliary steam shut-off valve, 73 …… Auxiliary steam amount adjustment valve, 74 ……
Steam temperature controller.

Claims (6)

(57) [Claims] 1. A gas turbine, a steam turbine, and a generator coaxially connected by a connecting shaft, and an exhaust heat recovery device that recovers exhaust heat of the gas turbine to generate steam, wherein the steam turbine is A high-pressure turbine, a reheat type intermediate-pressure turbine to which steam discharged from the high-pressure turbine is heated by the exhaust heat recovery device, and a low-pressure turbine to which exhaust steam of the intermediate-pressure turbine is supplied. In the single-shaft combined plant, the auxiliary steam, which is different from the steam from the exhaust heat recovery device, is supplied to the intermediate-pressure turbine to raise the connecting shaft of the single-shaft combined plant. The gas turbine is then ignited, and the medium-pressure turbine is ignited until steam from the exhaust heat recovery device due to exhaust heat of the gas turbine is supplied to the steam turbine. Single-shaft combined plant startup method characterized by continuing the supply of auxiliary steam to the bottle. 2. The auxiliary steam is supplied to the intermediate-pressure turbine using a path for supplying turbine driving steam to the intermediate-pressure turbine, and the amount of the auxiliary steam is adjusted by a steam control valve of the intermediate-pressure turbine. Activating a single-shaft combined plant. 3. The auxiliary steam is supplied to the intermediate-pressure turbine through an auxiliary-steam path separate from a path for supplying turbine driving steam to the intermediate-pressure turbine. A method for starting a single-shaft combined plant, wherein an auxiliary steam amount is adjusted by an adjusting valve provided. 4. The single-shaft type according to claim 1, wherein the temperature of the auxiliary steam is adjusted according to at least one of a plant shutdown time before starting the plant and a metal temperature of the steam turbine. How to start a combined plant. 5. A gas turbine, a steam turbine, and a generator coaxially connected by a connecting shaft, and an exhaust heat recovery device that recovers exhaust heat of the gas turbine to generate steam, wherein the steam turbine is A high-pressure turbine, a reheat type intermediate-pressure turbine to which steam discharged from the high-pressure turbine is heated by the exhaust heat recovery device, and a low-pressure turbine to which exhaust steam of the intermediate-pressure turbine is supplied. In the single-shaft combined plant consisting of, the auxiliary heat different from the steam from the exhaust heat recovery device is supplied to the intermediate pressure turbine to rotate the connection shaft that is stopped, and the exhaust heat recovery is performed after the gas turbine ignition. A single-shaft combined fuel supply system comprising an auxiliary steam supply device for maintaining the supply of the auxiliary steam to the medium-pressure turbine until steam from a device is supplied to the high-pressure turbine. Runt. 6. A steam turbine including a high-pressure turbine, a reheat-type intermediate-pressure turbine, and a low-pressure turbine into which exhaust steam of the reheat-type medium-pressure turbine is introduced, and a connection shaft coaxial with the steam turbine. Gas turbine and generator, a waste heat recovery device including a steam path for recovering waste heat of the gas turbine to generate steam and returning the steam to the high pressure turbine and the reheated medium pressure turbine, and a plant A single-shaft combined plant, comprising: an auxiliary steam supply device for supplying, to the reheat medium-pressure turbine, auxiliary steam other than steam from the exhaust heat recovery device to the reheat turbine at startup. .