JP2999119B2 - Gas turbine exhaust cooling system for a combined plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine in which exhaust gas from a gas turbine is guided to a boiler furnace, fuel is burned by residual oxygen in the exhaust gas, and a steam turbine is driven by steam generated by the combustion heat. The present invention relates to a gas turbine exhaust gas cooling device and a condensate / water supply system for a steam turbine / boiler applied to a steam turbine combined plant.

[0002]

2. Description of the Related Art FIG. 3 is a system diagram showing an example of a conventional combined plant. In the figure, (1) is a boiler, (2) is a gas turbine, (3) is a condenser, (4) is a deaerator, (5) is a chimney, (6),
(7) is a boiler exhaust gas cooling system, (8) is a gas turbine exhaust gas cooling system, (9) is a low-pressure feedwater heater, and (10) is a high-pressure feedwater heater. As described above, conventionally, the gas turbine exhaust gas cooling device (8) is installed in series with the boiler exhaust gas cooling device (7) in the high-pressure water supply system downstream of the deaerator (4).

[0003]

Conventionally, since a gas turbine exhaust gas cooling device (8) is installed in series with a boiler exhaust gas cooling device (7) in a high-pressure water supply system, heat absorption from these exhaust gases to the feedwater is performed. Large amount. Therefore, below a certain load, especially under partial load, the total amount of water supplied to the boiler (or the amount obtained by subtracting the minimum flow of the high pressure feed water heater)
Even though the exhaust gas flows into these exhaust gas cooling devices (7) and (8), the outlet feedwater temperature becomes too high. Therefore, it is necessary to flow extra water so as to suppress the outlet water supply temperature, and to recycle the surplus from the exhaust gas cooling device outlet to a condenser or the like. However, since the heat absorption amount of the feedwater is large as described above, the load at which the recirculation is to be started (recycling is required below the load) becomes high. Since the pressure of the high-pressure water supply system is about 200 atg even at the subcritical pressure and 300 atg or more at the supercritical pressure, it is not possible to release the control valve while constantly flushing it as a normal operation. Therefore, the recirculation starting load becomes the practical minimum load, and the operating range in the combined operation of the gas turbine is narrowed.

[0004]

In order to solve the above-mentioned conventional problems, the present inventor guides an exhaust gas of a gas turbine to a boiler furnace, burns fuel by residual oxygen in the exhaust gas, and generates a heat of combustion. in in generated steam turbine and gas turbine combined plant for driving a steam turbine by the steam, the normal composite operation of the steam turbine and gas turbine,
The present invention proposes a gas turbine exhaust cooling system for a combined plant, wherein exhaust gas of the gas turbine is cooled by condensing water from a condenser to a deaerator of the steam turbine.

[0005]

In the present invention, a steam turbine and a gas turbine
During normal combined operation of the gas turbine , the gas turbine exhaust is cooled not by the high-pressure feedwater downstream of the deaerator but by the condensate from the steam turbine condenser to the deaerator, so that the high-pressure feedwater The amount of heat absorbed from the exhaust of the turbine is reduced, which can significantly reduce the load that requires recirculation in the high pressure system, i.e. the minimum load on the plant.

[0006]

FIG. 1 is a system diagram showing a first embodiment of the present invention. In this embodiment, the gas turbine exhaust gas cooling device (8) is not connected to the high-pressure water supply system downstream of the deaerator (7), but to a low-pressure condensate system upstream of the deaerator (7) in series with the boiler exhaust gas cooling device (6). Installed upstream. By installing the gas turbine exhaust gas cooling device (8) in the low-pressure condensing system in this way, the amount of heat absorbed from the exhaust gas into the high-pressure water supply system is suppressed, and the recirculation starting load, that is, the plant minimum load is significantly reduced. Thus, operability can be improved.

FIG. 2 is a system diagram showing a second embodiment of the present invention. Also in this embodiment, the gas turbine exhaust gas cooling device (8) is connected to the low-pressure condensing system with the boiler exhaust gas cooling device (6).
It is installed in series but downstream of it. The operation and effect are the same as those of the first embodiment.

[0008]

According to the present invention, the amount of heat absorbed from the exhaust gas into the high-pressure water supply system is cooled by cooling the exhaust gas of the gas turbine not by the boiler feedwater downstream of the deaerator but by the low-pressure condensate upstream of the boiler. Can be greatly reduced, so that the recirculation start load of the high-pressure system and, consequently, the minimum load can be significantly reduced by 30 to 40% or more.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a first embodiment of the present invention.

FIG. 2 is a system diagram showing a second embodiment of the present invention.

FIG. 3 is a system diagram showing an example of a conventional combined plant.

[Explanation of symbols]

 (1) Boiler (2) Gas turbine (3) Condenser (4) Deaerator (5) Chimney (6), (7) Boiler exhaust gas cooling device (8) Gas turbine exhaust gas cooling device (9) Low pressure feed water heating (10) High pressure feed water heater

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F01K 23/10 F01K 11/00 F02C 6/18 F22B 33/18

Claims (1)

(57) [Claims] In a combined steam turbine and gas turbine plant, an exhaust gas of a gas turbine is guided to a boiler furnace, fuel is burned by residual oxygen in the exhaust gas, and a steam turbine is driven by steam generated by the combustion heat. Steam tank
A gas turbine exhaust cooling system for a combined plant, wherein exhaust gas of the gas turbine is cooled by condensing water from a condenser to a deaerator of the steam turbine during normal combined operation of the turbine and the gas turbine .