JP2766375B2 - Control method of bypass damper for combined cycle power plant - Google Patents

Description

The present invention relates to a bypass damper control method for a combined cycle power plant having a bypass damper in an exhaust gas duct of a gas turbine.

(Prior Art) A combined cycle power plant includes a gas turbine 1 and a generator 2, a steam turbine 3 and a generator 4, and an exhaust heat recovery boiler (hereinafter referred to as HRSG) 5, as shown in FIG. The gas turbine 1 is connected to the HRSG 5 and the bypass stack 6 by an exhaust gas duct 8 having a bypass damper 7. The exhaust gas of the gas turbine 1 is guided to the HRSG 5, and the steam turbine 3 is generated by the steam generated there. It is configured to be driven.

In this type of combined cycle power plant, when the gas turbine 1 is operated independently, the bypass damper 7 is fixed to the side A in FIGS.
Exhaust gas leaving the gas turbine 1 is discharged from the bypass stack 6 to the atmosphere through an exhaust gas duct 8. During the combined operation, the damper 7 is fixed to the bypass stack 6 on the B side in FIGS. 1 and 2 so that the exhaust gas of the gas turbine 1
5, steam is generated, and the steam drives the steam turbine 3.

When the conventional combined cycle power plant shifts from the single operation state of the gas turbine 1 to the combined cycle operation, the damper opening θ of the bypass damper 7 is determined by the diverter type damper in FIG. 1 and FIG. As shown in the figure, an opening degree between 0 ° on the A side in the gas turbine alone operation state and 90 ° on the B side in the combined cycle operation, for example, 30 °, 45 °
At an angle of ゜, 65 °, the damper 7 is held at certain times t ₁ , t ₂ , t ₃ as shown in FIG.

Maintaining the opening degree and time of the damper 7 is necessary for the following reasons. In other words, (1) thermal stress relaxation of HRSG thick-walled parts (high-pressure steam drum, high-pressure steam header, etc.) (2) High, medium and low pressure steam drums are expected to stabilize the water level.

Conventionally, the holding times t ₁ , t ₂ , and t ₃ are the most severe conditions, that is, the HR at the maximum gas turbine exhaust gas temperature shown in FIG.
The set value when the SG5 was cold was used, and was not changed with respect to the exhaust gas temperature of the gas turbine 1 and the metal temperature of the HRSG5.

(Problems to be Solved by the Invention) As described above, in the conventional control method of the bypass damper of the combined cycle power plant, the HRSG5 is set under mild conditions, that is, when the exhaust gas temperature of the gas turbine 1 is low and the HRSG5 is hot. when migrating to combined cycle operation from turbine single operation (startup HRSG), retention time of the damper _{7 t 1, t 2, t} 3 is determined by the maximum temperature of FIG. 4, it will take the time unnecessarily At the same time, an unnecessary startup loss occurs.

An object of the present invention is to reduce the start-up time and thereby reduce the start-up loss by adjusting the opening holding time of the bypass damper in response to a moderate state with respect to the HRSG. A method for controlling a bypass damper of a plant is provided.

[Configuration of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention relates to a combined cycle power plant having a bypass damper for changing a course of an exhaust gas flow to an exhaust heat recovery boiler or a bypass stack in an exhaust gas duct of a gas turbine. In the bypass damper control method, the opening degree when the bypass damper is opened is set to a plurality of types, and the holding time at each opening degree is a function of the gas turbine exhaust gas temperature and the drum metal temperature of the exhaust heat recovery boiler or the gas turbine exhaust gas temperature. And a function of a drum pressure equivalent to a drum metal temperature of the exhaust heat recovery boiler, and the opening degree of the bypass damper is controlled in accordance with each holding time.

(Operation) In the present invention, when shifting from the gas turbine alone operation to the combined cycle operation, the opening control is performed by controlling the opening damping time of the bypass damper with respect to the HRSG in accordance with a severe condition and a gentle condition. Do.

Therefore, according to the control method of the present invention, when the HRSG is in a gradual state, it is possible to reduce the start-up time and the drive loss associated therewith, which were not possible with the conventional method.

(Example) Hereinafter, the present invention will be described with reference to an example shown in the drawings. The combined cycle power plant to which the bypass damper control method according to the present invention is applied is the same as the plant configuration shown in FIG.

That is, when the gas turbine 1 is operated alone, by fixing the bypass damper 7 to the side A in FIG. 1, the exhaust gas exiting the gas turbine 1 is discharged from the bypass stack 6 to the atmosphere through the exhaust gas duct 8, The generator 2 generates electric power.

During the combined operation, the exhaust gas of the gas turbine 1 flows into the HRSG 5 through the exhaust gas duct 8 to generate steam by fixing the bypass damper 7 to the bypass stack 6 on the B side in FIGS. 1 and 2. The steam drives the steam turbine 3 to generate electric power in the generator 4. The steam worked in the steam turbine 3 returns to the HRSG 5 through the condenser 9.

Thus, in the present invention, when the combined cycle power plant shifts from the gas turbine independent operation to the combined cycle operation, that is, when the bypass damper 7 in FIG.
The holding times t ₁ , t ₂ and t ₃ at a certain opening θ of the damper 7 shown in FIG. 3 and FIG. ₃ are set by a function of the gas turbine exhaust gas temperature and the drum metal temperature of the HRSG or the drum pressure equivalent thereto. The opening degree of the bypass damper 7 is controlled in accordance with the holding time.

The opening retention time t ₁ , t shown in FIG. 3 of the bypass damper 7
_The following equation (1) is used for setting t ₂ and t ₃ . That is, The holding times t ₁ , t ₂ , t ₃ are functions of the gas turbine exhaust gas temperature (T) and the drum pressure (P) which is equivalent to the HRSG high pressure steam drum metal temperature. In this embodiment, the holding time t ₂
Is a constant value, but there is no problem if it is set as a function of the exhaust gas temperature (T) and the drum pressure (P). In the present embodiment, the holding time t ₁ is a function of the third power of the exhaust gas temperature (T) and the first power of the drum pressure (P), but is not limited to this. FIG. 5 shows the relationship between the damper holding time (t ₁ , t ₂ , t ₃ ) and the HRSG high-pressure drum pressure (P) according to the above equation (1). However, in FIG. 5, the figures in parentheses indicate the gas turbine exhaust gas temperature.

In FIG. 5, a comparison of the startup time under the strictest conditions and the mildest conditions for HRSG5 is as follows.

(1) The most severe condition the gas turbine exhaust gas temperature T = 568 ℃ (80% load gas turbine) HRSG pressure drum pressure P = 0 ^atg (HRSG cold state) at this time t ₁ = 16.4 min t ₂ = 10 min t ₃ = 12.6 minutes _{t 1 + t 2 + t 3} = 39.0 min (2) the most mild conditions a gas turbine exhaust gas temperature T = 350 ° C. (gas turbine no load) HRSG pressure drum pressure P = 80 ^atg (HRSG HOT state) t ₁ at this time = 1.5 min t ₂ = 10 min t ₃ = 3.1 min _{t 1 + t 2 + t 3} = 14.6 min above calculation is a value calculated for the actual plant, up to 24 minutes closer Consequently, it is possible to shorten the start It is. These time setting functions calculate the thermal stress of the thick member of the HRSG5 and are determined so that the thermal stress is constant at all operating points.

Next, another embodiment of the bypass damper 7 used in the present invention will be described. The bypass damper 7 shown in FIGS. 1 and 2 is a diverter type damper. However, as shown in FIG. 6, the damper 7 of the present invention is a two-blade louver type damper.
7a or a multi-blade louver type damper 7b shown in FIG.

Further, the opening retention time of the damper in the present invention is t ₁ , t
_2, not limited to the three levels of t _3, the holding angle and frequency can be arbitrarily determined. Further, the setting of the holding time is supported by the above equation (1), but these functions are free. In this embodiment, the thermal state of the HRSG 5 is represented by the high-pressure steam drum pressure. However, the present invention is not limited to this. Any parameter that supports the thermal state of the HRSG 5, such as the drum temperature, the pipe temperature, and the pipe steam pressure, can be applied. .

〔The invention's effect〕

As described above, according to the present invention, the opening degree holding time at a certain angle when the bypass damper is opened is changed and set in accordance with the operation state of the HRSG, so that when the HRSG is loose, In addition, it is possible to reduce the startup time and the startup loss associated therewith, which cannot be achieved by the conventional method.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a combined cycle power plant that implements a combined cycle power plant bypass damper control method of the present invention, FIG. 2 is a schematic configuration diagram of a bypass damper for describing the present invention, and FIG. FIG. 4 is a characteristic diagram showing a relationship between a holding time and an opening degree of a damper used in the present invention. FIG. 4 is a characteristic diagram showing a relationship between a gas turbine load and a gas turbine exhaust gas temperature for explaining the present invention. FIG. 6 is a characteristic diagram showing the relationship between gas turbine exhaust gas temperature, HRSG high-pressure drum pressure and damper holding time for explaining the present invention. FIGS. 6 and 7 show another embodiment of a bypass damper used in the present invention. FIG. 1 ... gas turbine, 2,4 ... generator 3 ... steam turbine 5 ... waste heat recovery boiler (HRSG) 6 ... bypass stack, 7 ... bypass damper 8 ... exhaust gas duct, 9 ... condensate vessel

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-51-35835 (JP, A) JP-A-58-501866 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01K 23/10

Claims (1)

(57) [Claims] 1. A bypass damper control method for a combined cycle power plant having a bypass damper for changing the course of an exhaust gas flow to an exhaust heat recovery boiler or a bypass stack in an exhaust gas duct of a gas turbine, wherein an opening degree when the bypass damper is opened is determined. A function of a gas turbine exhaust gas temperature and a drum metal temperature of an exhaust heat recovery boiler or a function of a drum pressure equivalent to a gas turbine exhaust gas temperature and a drum metal temperature of an exhaust heat recovery boiler. And controlling the opening of the bypass damper in accordance with each holding time of the bypass damper.