JP4098450B2 - Cold start method for waste heat recovery equipment of combined cycle power plant - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cold start method for exhaust heat recovery equipment of a combined cycle power plant, in which the condenser does not decrease below a certain vacuum level when the cold start is performed.
[0002]
[Prior art]
Recently, there is a so-called combined cycle power plant as a power generation facility for effective use of energy. This power plant mainly includes a power generator, a steam turbine and a gas turbine that drive the power generator, collects exhaust gas from the gas turbine, generates steam using residual heat of the exhaust gas, and generates steam. An exhaust heat recovery facility is provided that includes an exhaust heat recovery boiler that supplies air to the steam generator and a condenser that recovers and condenses the steam that has finished work in the steam turbine.
[0003]
FIG. 4 is a schematic configuration diagram showing exhaust heat recovery equipment of a combined cycle power plant.
[0004]
The exhaust heat recovery equipment recovers heat of exhaust gas EG from a gas turbine (not shown), and exhaust heat recovery boiler A that sends steam evaporated by the heat to high-pressure, intermediate-pressure and low-pressure steam turbines; A vacuum pump (not shown) that is always maintained at a vacuum level above a certain value, and is provided with a condenser B that cools and collects steam collected from the steam turbine during normal operation of the combined cycle power plant. High-pressure main steam pipe 1, medium-pressure main steam pipe 2, low-pressure main steam pipe 3, high-pressure main steam drain pipe 4, medium-pressure main steam drain pipe 5 and low-pressure main steam drain for sending steam from recovery boiler A to the steam turbine One end of each pipe 6 is connected, and the other end of each of the drain pipes 4, 5, 6 is connected to the condenser B.
[0005]
The exhaust heat recovery boiler A includes an exhaust gas duct C of an exhaust heat recovery boiler that recovers heat of exhaust gas from a gas turbine, a high-pressure steam drum 7 installed in the exhaust gas duct C of the exhaust heat recovery boiler, and an intermediate pressure steam. A drum 8 and a low-pressure steam drum 9 are provided. These steam drums are respectively connected to the high-pressure evaporator 10, the intermediate-pressure evaporator 11 and the low-pressure evaporator 12 inserted in the exhaust gas duct C of the exhaust heat recovery boiler, and the water stored in each steam drum corresponds to each. By circulating through the evaporator, heat exchange with the exhaust gas is achieved.
[0006]
Further, in the exhaust gas duct C of the exhaust heat recovery boiler, the steam generated in each of the steam drums 7, 8, 9 is superheated, and the high-pressure main steam pipe 1, the medium-pressure main steam pipe 2, and the low-pressure main steam pipe 3. A high-pressure superheater 13, an intermediate-pressure superheater 14, and a low-pressure superheater 15 that individually supply air to the high-pressure, intermediate-pressure, and low-pressure steam turbines are provided.
[0007]
On the other hand, the high-pressure main steam pipe 1, the medium-pressure main steam pipe 2 and the low-pressure main steam pipe 3 on the outlet side of the superheaters 13, 14 and 15 are respectively connected to the high-pressure superheater outlet valve 16, the medium-pressure superheater outlet valve 17 and the low-pressure superheater. A vessel outlet valve 18 is provided. Further, a high-pressure main steam stop valve 19, an intermediate-pressure main steam stop valve 20, and a low-pressure main steam stop valve 21 are arranged on the steam turbine side of the main steam pipes 1, 2, and 3, respectively. Further, the main steam drain pipes 4, 5 and 6 on the condenser B side are provided with a high pressure main steam drain valve 22, an intermediate pressure main steam drain valve 23 and a low pressure main steam drain valve 24, respectively.
[0008]
By the way, in the exhaust heat recovery facility of the combined cycle power plant having such a configuration, nitrogen (N ₂ ) enclosed in the steam drums 7, 8 and 9, main power before power generation operation and before re-operation after maintenance. It is necessary to cold start the exhaust heat recovery facility for the purpose of eliminating the air staying in the steam pipes 1, 2 and 3.
[0009]
Conventionally, as a cold starting method of this exhaust heat recovery equipment, the superheater outlet valves 16, 17 and 18 and the main steam drain valves 22, 23 and 24 are simultaneously opened, and the residual gas is caused to flow into the condenser B. A vacuum pump (not shown) is used to pull out.
[0010]
[Problems to be solved by the invention]
However, in such a cold start method of exhaust heat recovery equipment, there is a problem that when nitrogen or air is intensively flowed into the condenser, an event occurs in which the vacuum degree of the condenser decreases suddenly. there were.
[0011]
The present invention has been made in view of the above circumstances, and restricts the flow rate of the gas flowing into the condenser at the time of cold start to prevent the condenser vacuum from being lowered below a certain value. An object of the present invention is to provide a cold start method for exhaust heat recovery equipment of a combined cycle power plant that can be used.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention recovers heat of the exhaust gas of a gas turbine by a plurality of superheaters provided in an exhaust gas duct, and the main steam output from each superheater is passed through each main steam pipe. The steam is supplied to each steam turbine, and the exhaust of each steam turbine is condensed by a common condenser, and the main steam train between the outlet of each superheater and the main steam stop valve provided in each main steam pipe is used. In a cold start method for exhaust heat recovery equipment of a combined cycle power plant, wherein a pipe is connected to the condenser via a main steam drain valve, the gas enclosed in the superheater and the main steam drain pipe is supplied to the condenser. When flowing into the water device, each main steam drain valve opens at an opening degree set so that the vacuum degree of the condenser does not decrease below a predetermined value, so that the open time zones do not overlap each other. Open time set for a long time It is to be controlled by timing.
[0015]
According to such a cold start method, since the restricted gas flows into the condenser, it is possible to prevent the vacuum degree of the condenser from being lowered to a certain value or less.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
An embodiment of the exhaust heat recovery facility of the combined cycle power plant to which the cold start method according to the present invention is applied will be described with reference to FIG.
[0018]
FIG. 1 is a timing diagram for explaining a first embodiment of a cold start method according to the present invention. When the exhaust heat recovery facility of FIG. 4 is cold-started, first, an open command is given to the high-pressure main steam drain valve 22 to fully open it for a predetermined time T, and the main nitrogen, sealed in the high-pressure steam drum 7 and the high-pressure superheater 13, The air staying in the steam pipe 1 is discharged to the condenser B.
[0019]
Next, when the first set time τ1 (τ1> T) has elapsed from the opening command timing of the drain valve 22, an opening command is given to the intermediate pressure main steam drain valve 23 to fully open it for a predetermined time T, and the intermediate pressure steam drum 8 and nitrogen sealed in the intermediate pressure superheater 14 and the air remaining in the main steam pipe 2 are exhausted to the condenser B.
[0020]
Thereafter, when the second set time τ2 (adjusted during the trial operation) has elapsed from the opening timing of the drain valve 22, the low-pressure main steam drain valve 24 is fully opened only for a predetermined time T and enclosed in the low-pressure steam drum 9 and the low-pressure superheater 15. The nitrogen and the air remaining in the main steam pipe 3 are exhausted to the condenser B. In this case, the first set time τ1 and the second set time τ2 are set so that the open time periods when the high pressure drain valve 22, the intermediate pressure drain valve 23, and the low pressure drain valve 24 are fully opened do not overlap with each other. Even when gas is exhausted to the condenser B in the time zone, the time is set such that the vacuum degree of the condenser B does not decrease below a certain value.
[0021]
FIG. 2 is a timing diagram for explaining a second embodiment of the cold start method according to the present invention. When the exhaust heat recovery facility of FIG. 4 is cold-started, first, an open command is given to the high-pressure main steam drain valve 22 to fully open it for a predetermined time T, and the main nitrogen, sealed in the high-pressure steam drum 7 and the high-pressure superheater 13, The air staying in the steam pipe 1 is exhausted to the condenser B.
[0022]
Next, when the third set time τ3 elapses from the closing timing of the drain valve 22, an open command is given to the intermediate pressure main steam drain valve 23 to fully open it for a predetermined time T, and the intermediate pressure steam drum 8 and the intermediate pressure superheater are set. The nitrogen encapsulated in 14 and the air remaining in the main steam pipe 2 are exhausted to the condenser B.
[0023]
Thereafter, when the fourth set time τ4 has elapsed from the closing timing of the drain valve 23, the low-pressure main steam drain valve 24 is fully opened for a predetermined time T, and nitrogen and main steam sealed in the low-pressure steam drum 9 and the low-pressure superheater 15 are opened. The air staying in the pipe 3 is exhausted to the condenser B. In this case, the third set time τ3 and the fourth set time τ4 are set so that the open time periods in which the high pressure drain valve 22, the intermediate pressure drain valve 23 and the low pressure drain valve 24 are fully opened do not overlap with each other. Even when gas is exhausted to the condenser B in the time zone, the time is set such that the vacuum degree of the condenser B does not decrease below a certain value.
[0024]
FIG. 3 is a timing chart for explaining a third embodiment of the cold start method according to the present invention. When the exhaust heat recovery equipment is cold-started, the drain valves 22, 23 and 24 are simultaneously opened and closed after the outflow of nitrogen and air by the condenser B is completed. In this case, each drain valve is controlled to an opening degree so that the vacuum degree of the condenser B does not decrease below a certain value by the gas exhausted to the condenser B even if it is opened simultaneously.
[0025]
Note that the drain valves 22 to 24 are not necessarily opened all at once, and may be opened arbitrarily. In short, it is only necessary that the vacuum degree of the condenser does not drop below a certain value with all drain valves open.
[0026]
【The invention's effect】
As described above, according to the present invention, the combined cycle power generation that can prevent the vacuum degree of the condenser from decreasing to a certain value or less by restricting the flow rate of the gas flowing into the condenser at the cold start. A cold start method for the exhaust heat recovery equipment of the plant can be provided.
[Brief description of the drawings]
FIG. 1 is a timing diagram for explaining a first embodiment of a cold start method according to the present invention;
FIG. 2 is a timing diagram for explaining a second embodiment of a cold start method according to the present invention;
FIG. 3 is a timing diagram for explaining a third embodiment of a cold start method according to the present invention;
FIG. 4 is a diagram showing an exhaust heat recovery facility of a combined cycle power plant.
[Explanation of symbols]
A ... Waste heat recovery boiler B ... Condenser C ... Exhaust heat recovery boiler exhaust gas duct 1 ... High pressure main steam pipe 2 ... Medium pressure main steam pipe 3 ... Low pressure main steam pipe 4 ... High pressure main steam drain pipe 5 ... Medium pressure Main steam drain pipe 6 ... Low pressure main steam drain pipe 7 ... High pressure steam drum 8 ... Medium pressure steam drum 9 ... Low pressure steam drum 10 ... High pressure evaporator 11 ... Medium pressure evaporator 12 ... Low pressure evaporator 13 ... High pressure superheater 14 ... Medium pressure superheater 15 ... Low pressure superheater 16 ... High pressure superheater outlet valve 17 ... Medium pressure superheater outlet valve 18 ... Low pressure superheater outlet valve 19 ... High pressure main steam stop valve 20 ... Medium pressure main steam stop valve 21 ... Low pressure main Steam stop valve 22 ... High pressure main steam drain valve 23 ... Medium pressure main steam drain valve 24 ... Low pressure main steam drain valve

Claims (1)

The exhaust gas of the gas turbine is heat recovered by a plurality of superheaters provided in the exhaust gas duct, and main steam output from each superheater is supplied to each steam turbine via the respective main steam pipes. The main steam drain pipe is connected to the main steam drain valve between the outlet of each superheater and the main steam stop valve provided in each main steam pipe. In the cold start method of the exhaust heat recovery equipment of the combined cycle power plant that is connected through
When the gas sealed in the superheater and the main steam drain pipe flows into the condenser, each main steam drain valve has a flow rate at which the degree of vacuum of the condenser does not decrease below a predetermined value. set to open in the opening, a cold start process of the exhaust heat recovery system of the combined cycle power plant, characterized in that it is controlled by the opening timing set in such time as not to overlap the open time zone to each other in.

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