JPH0427703A - Control method of by-pass damper in combined cycle power generating plant - Google Patents

Abstract

PURPOSE:To shorten start-up time and reduce start-up loss by changing the opening holding time of a by-pass damper at a certain opening angle at the time of opening this by-pass damper according to the operated state of an HRSG to set the opening holding time. CONSTITUTION:The holding time of a by-pass damper 7 at a certain opening angle theta at the time of shifting from the gas turbine single operation to the combined cycle operation in a combined cycle power generating plant, that is, at the time of opening the by-pass damper 7 into a B-side position from an A-side position, is set by a function of gas turbine exhaust gas temperature and HRSG drum metal temperature or equivalent drum pressure. The by-pass damper 7 is then controlled in its opening according to its holding time. Start-up time can be shortened and start-up loss can be reduced by thus adjusting the opening holding time of the by-pass damper 7 to an HRSC correspondingly to the time when the HRSC is in the moderately operated state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a bypass damper control method for a combined cycle power plant having a bypass damper in the exhaust gas duct of a gas turbine.

(Prior Art) As shown in FIG. 1, a combined cycle power plant includes a gas turbine 1, a generator 2, and a steam turbine 3.
It is equipped with a generator 4 and an exhaust heat recovery boiler (hereinafter referred to as HR3G) 5, and the gas turbine 1, HR5G5, and bypass stack 6 are connected by an exhaust gas duct 8 having a bypass damper 7. The exhaust gas from the gas turbine 1 is guided to the HR5G5, and the steam generated there drives the steam turbine 3.

In this type of combined cycle power plant,
When the gas turbine 1 is operating independently, by fixing the bypass damper 7 to the A side in FIGS. 1 and 2, the exhaust gas leaving the gas turbine 1 passes through the exhaust gas duct 8 and exits from the bypass stack 6 to the atmosphere. released. Also, during combined operation, by fixing the damper 7 to the pie bus stack 6 side on the B side in FIGS. 1 and 2, the exhaust gas from the cast turbine 1 passes through the exhaust gas duct 8 to the HR5G
5 and generates steam, which drives the steam turbine 3.

Therefore, in a conventional combined cycle power plant, when the gas turbine 1 shifts from an independent operation state to a combined cycle operation, the damper opening degree θ of the bypass damper 7 is changed as shown in FIGS. As shown in the figure, there is a certain opening between 0° on the A side in the gas turbine independent operation state and 90° on the B side in the combined cycle operation, for example 30'.
, 45'65°, the damper 7 will be held at tx+t2+tJ for a certain time as shown in FIG.

Maintaining the opening degree and time of the damper 7 is necessary for the following reasons. In other words, (2) thermal stress relaxation of HR3G's thick-walled parts (high-pressure steam tram, high-pressure steam header, etc.), and (2) stabilization of high-, medium-, and low-pressure steam drum water levels are expected.

Conventionally, this retention time t□, t2. tll uses the set value under the most severe conditions, that is, when the gas turbine exhaust gas temperature is at its highest and the HR8G5 is completely cold, as shown in Fig. 4, and the wandering gas temperature of the gas turbine 1 and the HR8
It was not changed with respect to the metal temperature of G5.

(Problem II to be Solved by the Invention) As described above, in the conventional bypass damper control method of a combined cycle power plant, the condition is mild with respect to HR5G5, that is, the exhaust gas temperature of the gas turbine 1 is low and the HR3G5 is hot. When transitioning from gas turbine independent operation to combined cycle operation (HR
5G activation), damper 7 holding time t, 12.1
□ is determined by the maximum temperature shown in Figure 4, which means that it takes more time than necessary, and at the same time causes more start-up loss than necessary.

The purpose of the present invention is to provide a combined cycle power generation system that shortens the startup time and reduces the startup loss associated with it by adjusting the opening holding time of the bypass damper in response to the slow state relative to HR3G. A method for controlling a bypass damper in a plant is provided.

[Structure of the invention]

(Means for Solving the Problems) A method for controlling a bypass damper in a combined cycle power generation plant according to the present invention is a combined cycle power generation plant having a bypass damper in an exhaust gas duct of a gas turbine that changes the course of an exhaust gas flow to an exhaust heat recovery boiler or a bypass stack. In a plant, the bypass damper is opened at a plurality of opening degrees, and the holding time at each opening degree is a function of the gas turbine exhaust gas temperature, the drum metal temperature of the exhaust heat recovery boiler, or the equivalent drum pressure. The opening degree is controlled in accordance with each holding time.

(Function) In the present invention, when the gas turbine shifts from single operation to combined cycle operation, the opening of the bypass damper is controlled by the opening holding time that changes depending on whether the conditions are severe or gentle for HR3G. Do this.

Therefore, according to the control method of the present invention, it is possible to shorten the start-up time and reduce the driving loss associated with it, which was not possible with the conventional method, when the condition is moderate relative to HR8G.

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

That is, when the gas turbine 1 is operating independently, by fixing the bypass damper 7 to the A side in FIG. 1, the exhaust gas leaving the gas turbine 1 passes through the exhaust gas duct 8 and is discharged from the bypass stack 6 to the atmosphere. A generator 2 generates electric power.

Also, during combined operation, bypass damper 7 is
By fixing it to the bypass stack 6 side on the B side in FIG. The generator 4 is made to generate electric power. The steam worked by the steam turbine 3 passes through the condenser 9 and returns to the HR5G5.

Therefore, in the present invention, FIGS. 2 and 2 show the transition from the gas turbine independent operation to the combined cycle operation in a combined cycle power plant, that is, when the bypass damper 7 in FIG. 1 is opened from the A side position to the B side position. The holding time t>+jz+ at a certain opening degree θ of the damper 7 shown in FIG. The opening degree is controlled in accordance with the holding time.

The opening holding time tie of the bypass damper 7 shown in FIG.
When setting tel'tl, the following formula is adopted. Namely.

The holding time t□1t21t,1 is a function of the gas turbine exhaust gas temperature (T) and the drum pressure (P), which is equivalent to the HR8G high pressure steam drum metal temperature. In this example, the holding time t2 was set to a constant value, but the exhaust gas temperature (T
) and drum pressure (P) without any problem. Further, in this embodiment, the holding time t is the third power of the exhaust gas temperature (T).

As a function of one modulo of the drum pressure (P), but not limited thereto. Furthermore, damper holding time (t□, t2.tt) and HR3G high pressure drum pressure (P) according to the above ω formula
The relationship between the two is shown in FIG.

However, in Fig. S, the numbers in parentheses indicate the gas turbine exhaust gas temperature.

In FIG. 5, the start-up time is compared between the strictest condition and the mildest condition for HR3G5, and the results are as follows.

■Most severe conditions Gas turbine exhaust gas temperature T = 568°C (at 80% load of gas turbine) HR8G high pressure drum pressure P = Oatg (HRS G At this time t = 16.4 minutes and 2 = 10 minutes t = 12.6 min t 1+ t 2+ t , = 3 LO min (2) Mildest condition (cold state) Gas turbine exhaust gas temperature T = 350°C (at gas turbine no load) HR3GX pressure tram pressure P = 80a” (HR5G HOT state) This When t □ = 1.5 minutes t 2 = 10 minutes, = 3.1 minutes t □ + t 2 + t , = 14.6 minutes The above calculation is a value calculated for an actual plant, and from this result, the maximum 24
It is possible to shorten the startup by close to 1 minute. Further, these time setting functions are determined by calculating the thermal stress of the thick-walled member of HRSG5 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, the damper 7 of the present invention is a two-blade louver type damper 7 as shown in FIG.
8 may be used, and a multi-blade louver type damper 7b shown in FIG. 7 may be used in the same manner.

In addition, the damper opening holding time in the present invention is tl,
It is not limited to the three stages of tel t, but the holding angle and number of times can be arbitrarily determined. Furthermore, although the retention time was supported by the above equation 0, these functions are free. In addition, although the thermal state of HRS G5 was represented by the high pressure steam drum pressure in this example, it is not limited to this, but any parameter that supports the thermal state of HR5G5 can be used, such as drum temperature, piping temperature, and piping steam pressure. can also be applied.

〔Effect of the invention〕

As described above, according to the present invention, by changing and setting the opening holding time at a certain angle when opening the bypass damper, the HR5G
It is possible to shorten the start-up time and reduce the start-up loss associated with it, which could not be achieved with the conventional method, when the start-up time is gentle.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a combined cycle power generation plant that implements the bypass damper control method for a combined cycle power generation plant of the present invention, FIG. 2 is a schematic configuration diagram of a bypass damper for explaining the present invention, and FIG. FIG. 4 is a characteristic diagram showing the relationship between the holding time and opening degree of the damper used in the present invention. FIG. 4 is a characteristic diagram showing the relationship between gas turbine load and 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, HR8G high pressure drum pressure, and damper holding time to explain the present invention, and FIGS. 6 and 7 show other embodiments of the bypass damper used in the present invention. FIG. 1... Gas turbine 2.4... Generator 3...
Steam turbine 5...Exhaust heat recovery boiler (! (RSG)) 6...Bypass stack 7...Bypass damper 8...Exhaust gas duct 9...Condenser agent Patent attorney Nori Chika
You HR5G 7 r (Ipe λ Geshibe chart chart chart (degC)

Claims (1)

[Claims] In a combined cycle power plant that has a bypass damper in the exhaust gas duct of a gas turbine that changes the course of the exhaust gas flow to an exhaust heat recovery boiler or a bypass stack, there are multiple opening degrees when opening the bypass damper, and each opening degree is different. A combination characterized in that the holding time is set as a function of the gas turbine exhaust gas temperature, the drum metal temperature of the exhaust heat recovery boiler, or the drum pressure equivalent thereto, and the opening degree is controlled in accordance with each holding time. Bypass damper control method for cycle power plant.