JPH04179833A - Gas turbine co-generation system - Google Patents

Abstract

PURPOSE:To ensure a required amount of steam with use of a reliable and inexpensive method, by increasing an amount of water being supplied to a feedwater heater at the time of increase in the required amount of steam, and supplying to a package boiler a pre-heated hot water corresponding to the increase of feedwater. CONSTITUTION:When a required amount of steam is increased and only an exhaust gas energy from a gas turbine 1 fails to sufficiently serve the purpose, a required amount of water which is larger than an ordinary amount of water fed to an evaporator 3 is fed to a feedwater heater 4 by a feedwater pump 8. And after heating in the feedwater heater 4, water extraction is performed in front of a feedwater control valve 5 to feed the water to a package boiler 7 and burn a fuel (f), thereby causing generation of steam. This ensures a necessary amount of steam by operation of a highly reliable package boiler with a relatively low facility expenditure.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention generates electricity using a gas turbine for driving a generator,
The present invention relates to a so-called gas turbine cogeneration system that recovers the energy of the exhaust gas as steam via a waste heat boiler or the like.

[Conventional technology]

In the gas turbine cogeneration system described above, hot water from the waste heat boiler's economizer or feed water preheater is supplied to the waste heat boiler's evaporator, where it is heated with the gas turbine's exhaust gas to generate steam. ing. However, in such a waste heat boiler, given the steam conditions, the amount of energy recovered by steam is uniquely determined, and there is a limit to improving the recovery rate.

Therefore, for customers who require more steam than the amount of steam obtained from the exhaust gas of the gas turbine, a reheating burner is installed in this waste heat boiler to provide reheating fuel according to the required amount of steam. It is used to raise the exhaust gas temperature of the gas turbine. Incidentally, the exhaust gas temperature of a gas turbine is normally around 500°C, but when additional firing is performed as mentioned above, the temperature inside the waste heat boiler reaches over 000°C, exposing the waste heat boiler to harsh temperatures. There is a problem of being exposed. Furthermore, reheating boilers are expensive and
There was also the problem that there was some concern about its reliability.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas turbine cogeneration system that is highly reliable and can secure a necessary amount of steam using a pan cage boiler whose equipment cost is relatively low.

[Means to solve the problem]

That is, the gas turbine cogeneration system of the present invention supplies water to the feed water preheater of the gas turbine waste heat boiler in an amount greater than the amount of water supplied to the evaporator, and also extracts hot water preheated by the feed water preheater. It is characterized by being supplied to a package boiler.

In the above-mentioned cogeneration system, the required amount of steam can be secured with a highly reliable puff cage boiler, and the water supplied to the package boiler is preheated by the waste heat boiler's feed water preheater. The amount of fuel will be reduced.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a system diagram of a gas turbine cogeneration system according to the present invention, in which a gas turbine 1 drives a generator 2. As shown in FIG. Air A and fuel F are supplied to this gas turbine 1 as shown by arrows. Also, a waste heat boiler 13 that recovers the exhaust gas energy of the gas turbine 1 as steam S, and a pan cage boiler 7 that generates steam S by reheating the fuel f.
have. In the figure, 14 is a chimney. Further, this waste heat boiler 13 includes a feed water preheater 4 that preheats the feed water W introduced by the feed water pump 8 to make it hot water, and a feed water preheater 4 that preheats the feed water W introduced by the feed water pump 8 to make it hot water, and a feed water preheater 4 that introduces the preheated hot water via the feed water control valve 5 to generate steam S. An evaporator 3 for generating .

Furthermore, in this system, the aforementioned eight water supply pumps supply water to the water supply preheater 4 in an amount greater than the amount of water supplied to the evaporator 3.

In addition, the hot water supply from the water supply preheater 4 is transferred to the evaporator 3.
A water supply regulating valve 6 is provided for extracting water before the water supply regulating valve 5 and supplying water to the package boiler 7.

The water supply pump 8 described above is driven by a motor 9, and this motor 9 is controlled by a control device 10 such as an inverter that receives a signal from a detector 11 provided before the water supply control valve 6. There is.

Next, the operation of the cogeneration system having the above configuration will be explained.

Normally, in the waste heat boiler 13 as shown in FIG. 1, the difference between the gas temperature at the boiler evaporation start point and the steam temperature on the exhaust gas temperature drop line is the smallest from an economic point of view, and this temperature difference Δt is called a pinch temperature difference. This is because when the steam conditions are given, the exhaust gas temperature at the point where the pinch temperature difference Δt is given is determined [Tgz (pinch temperature) in FIG. 2].

Therefore, in a normal case, the outlet gas temperature of the waste heat boiler 13 having the feed water preheater 4 is indicated by Tgs in the figure, and the energy of the temperature difference between the gas inlet temperature TgI and the outlet gas temperature Tgs is recovered. Become.

On the other hand, if the required amount of steam increases and cannot be met by the exhaust gas energy from the gas turbine 1 alone, the water supply pump 8 shown in FIG. After being supplied to the feed water preheater 4 and preheated by the feed water preheater 4, water is extracted before the feed water adjustment valve 5 and is supplied to the package boiler 7. Then, by burning the fuel f in the puff cage boiler 7 to generate steam, a predetermined amount of steam is ensured as a whole.

In this case, the outlet gas temperature of the waste heat boiler 13 is Tg',
Therefore, from T g + to T8. Since the energy corresponding to the temperature difference up to 2000 can be recovered, the required amount of steam can be secured with the highly reliable package boiler 7.

Here, when the fuel f is being burned in the pan cage boiler 7, the feed water adjustment valve 6 at the inlet of the pan cage boiler 7 may be opened or closed due to fluctuations in the steam load, and at this time, the water supply is adjusted. As a result, the pressure within the discharge side system of the water supply pump 8 may fluctuate, so it is necessary to maintain the pressure within the system constant. Therefore, in this embodiment, the rotation speed of the motor 9 of the water supply pump 8 is controlled to a constant pressure by a signal from the detector 11 via a control device 10 such as an inverter.

Also, the evaporator 3 of the package boiler 7 or the waste heat boiler 13. When the load on each of the feed water preheaters 4 changes, the resistance curve of the pipe line changes to each rotation speed N A, N as shown by the pressure and water supply amount in Fig. 3 by opening and closing each water supply control valve 5.
I on the performance curve of the water pump 8 with m, N c
A, I! , or l.

becomes. Therefore, if the corresponding rotational speed Na, Nm, or N of the water supply pump 8 is selected, the operating point of the water supply pump 8 will move between A, B, and C depending on the load of the steam S.

〔Effect of the invention〕

As described above, according to the gas turbine cogeneration system of the present invention, the amount of water supplied to the feed water preheater is increased when the required amount of steam increases, and the hot water preheated by the feed water preheater of the increased water supply is used to improve reliability. Since it is supplied to a high puff cage boiler where it is converted into steam, the required amount of steam can be secured. Moreover, more energy from the gas turbine's exhaust gas can be recovered than with conventional systems, and thermal efficiency can be improved, giving the advantage of killing two birds with one stone.

In other words, a pancage boiler requires lower equipment costs than a conventional reheating boiler, and has the advantage that the amount of fuel used in the package boiler can be reduced by the amount of preheated feed water that is introduced.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a gas turbine cogeneration system according to the present invention, Fig. 2 is a diagram showing the relationship between temperature and enthalpy to explain the operation of the gas turbine cogeneration system according to the present invention, and Fig. 3 is a water pump It is a drawing which shows the pump performance curve which shows the relationship between the pressure and water supply amount at each rotation speed. 1... Gas turbine, 2... Generator, 3... Evaporator, 4... Feed water preheater, 7... Puff cage boiler, 8... Water feed pump, S... Steam, W...Water supply. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] A gas turbine cogeneration system in which water is supplied to a feed water preheater of a gas turbine waste heat boiler in an amount greater than the amount of water supplied to the evaporator, and hot water preheated by the feed water preheater is extracted and supplied to the package boiler. system.