JPS6149490B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and device for operating a combined plant that combines a gas turbine and a steam turbine, and particularly relates to a system for controlling the emission of nitrogen oxides (hereinafter abbreviated as NOx) during shutdown and startup. reduce the amount,
Moreover, it relates to an improved version that does not require an auxiliary boiler.

Next, the starting and stopping operations of a combined plant in the prior art will be explained. As mentioned above, since a combined plant is equipped with a steam turbine and a gas turbine, the operation of starting and stopping the entire plant includes starting and stopping the steam turbine and starting and stopping the gas turbine.

In a conventional combined plant shutdown operation, the exhaust passage of the gas turbine is gradually switched from the waste heat recovery boiler to the bypass passage while the gas turbine is maintained at the rated output, and the exhaust gas is directly discharged into the atmosphere. In this way, when the exhaust gas of the gas turbine no longer passes through the waste heat recovery boiler, steam generation stops, and the output of the steam turbine decreases, leading to the steam turbine being stopped. After the steam turbine is stopped, the output of the gas turbine is reduced (for example, the load of the generator serving as a load on the gas turbine is reduced) and the gas turbine is stopped.

In addition, in the conventional technology, the startup operation of a combined plant is to perform a grand seal on the steam turbine using steam generated by the auxiliary boiler, and then to raise the vacuum in the condenser until the steam turbine can be driven. During this time, the output of the gas turbine is increased to its rated value while exhaust gas from the gas turbine is directly released into the atmosphere (without passing through the denitrification device of the waste heat recovery boiler).

The starting and stopping operations of the combined plant according to the conventional technology described above are shown in Figures 1 and 2.
This will be explained in detail with reference to the figures. In FIG. 1, a gas turbine power generation device 1 includes an air compressor 11
, a gas turbine 12 , and a generator 13 . 14 is a combustor. Exhaust gas discharged from the gas turbine 12 is led to the waste heat recovery boiler 2 through the duct 15, and after recovering the heat retained in the exhaust gas, is discharged to the atmosphere from the chimney 26. Moreover, the exhaust gas discharged from the gas turbine 12 can be released into the atmosphere through the bypass duct 18 by fully closing the inlet damper 16 of the waste heat recovery boiler 2 and fully opening the bypass damper 17.
In the waste heat recovery boiler 2, a superheater 21, an evaporator 22, a denitrification device 23 built into the evaporator, a drum 24, and a carbon saver 25 are installed from the upstream side of the gas turbine exhaust gas flowing therein. ing. In addition, the water supplied from the condenser 41 to the waste heat recovery boiler 2 is supplied to the steamer 22 heated by the energy saver 25, and then to the drum 2.
4, and after being superheated in the superheater 21, the steam is supplied to the steam turbine 33 as turbine driving steam.

The steam turbine power generation device 3 is a steam turbine 3
3, 33', a main steam pipe 31 that guides steam from the superheater 21 of the waste heat recovery boiler 2 to the steam turbines 33, 33', and a main steam pipe 31 that guides steam from the superheater 21 of the waste heat recovery boiler 2 to the steam turbines 33, 33'; a steam valve 32 for controlling the amount; a generator 34 driven by the steam turbines 33, 33'; and a steam turbine 33, 33'.
and a condenser 41 that condenses the steam worked by the steam. Then, the condensate in the condenser 41 is transferred to the water supply pipe 4
Condensate pump 42 and water supply pump 4 installed in 3
5 to the waste heat recovery boiler 2 through the water supply pipe 43.
is supplied to the economizer 25. Further, a feed water heater 44 is installed in the feed water pipe 43, and the feed water heater 44 supplies steam extracted from the steam turbine 33 to the energy saver 25 of the waste heat recovery boiler 2 by guiding it through an extraction pipe 46. The water supply is heated.

Further, from the main steam pipe 31 to the turbine bypass pipe 4
7 and the condenser 41 via the turbine bypass valve 48
A turbine bypass system leading to the steam turbine generator 3 is provided, so that excess steam flowing to the steam turbine generator 3 can be bypassed to the condenser 41 and discharged.

In addition, the steam turbines 33, 33' are connected to the main steam pipe 3.
1, a system for supplying sealing steam to the gland part via the gland seal steam piping 35 and the gland seal steam regulator 36 is provided, and is further operated at the time of starting and stopping the steam turbine to supply seal steam to the gland part of the steam turbine 33. Auxiliary boiler 5 that supplies
1. An auxiliary boiler generation trachea 52 and a steam pressure reducing valve 53 are provided.

FIG. 2 shows the shutdown and startup curves of the above-mentioned combined plant, and the prior art shutdown and startup method will be explained with reference to this diagram. First, when the plant is shut down, the output of the gas turbine power generation device 1 (Fig. ₁ ) is maintained at the rated value during the time period T1 (that is, the power generation that is the load of the gas turbine 12 of the gas turbine power generation device) is maintained at the rated output. (maintaining the output of the turbine 13 at the rated value and the load of the gas turbine 12 at the rated value), gradually opening the bypass damper 17, and gradually closing the inlet damper 16 of the waste heat recovery boiler 2. As shown in Figure 2, the amount of exhaust gas from the waste heat recovery boiler is reduced, and the amount of exhaust gas from the bypass duct is increased. Along with this, as shown in b, the amount of steam generated in the waste heat recovery boiler decreases and disappears. The output of the steam turbine decreases due to the decrease in the amount of generated steam, and the steam turbine stops due to the loss of generated steam. During the time period _T1 after the shutdown, the steam turbine 3 is powered by the auxiliary boiler 51.
The gas turbine is stopped while supplying sealing steam to the gland No. 3.

As mentioned above, the metal temperature of the steam turbine is maintained at a high temperature in order to supply steam to the auxiliary boiler 51. It is advantageous for the metal temperature of the steam turbine to be kept high when the steam turbine is stopped so that the next startup can be performed quickly and smoothly.

Furthermore, at the time of startup according to the prior art, the auxiliary boiler 51 is first started, and during the time period _T3 , while supplying ground seal steam from the auxiliary boiler 51 to the steam turbine, the condenser 41 is turned on as shown in e. Perform vacuum rise. On the other hand, in the time period _T4 , the gas turbine has the inlet damper 16 of the waste heat recovery boiler 2 fully open and the bypass damper 17 fully open, and the load on the gas turbine is increased to the rated load as shown in f. (In other words, the output of the generator 13 is increased to the rated value). After the gas turbine 12 carries the rated load, during the time period _T5 , the amount of gas to the waste heat recovery boiler 2 is increased while gradually closing the bypass damper 17 as shown in d, and the amount of gas flowing into the waste heat recovery boiler 2 is increased as shown in e. In addition to increasing the amount of steam generated by the waste heat recovery boiler 2, the load on the steam turbine generator 3 (i.e.,
(load of the generator 34) is increased.

However, according to this conventional stop-start method, during the gas turbine rated load with a large amount of NOx (time periods T ₁ and T ₅ ), the gas turbine exhaust gas is transferred to the denitrification device 23 built into the waste heat recovery boiler 2.
Since the NOx gas is bypassed and released into the atmosphere from the bypass duct 18, there is a drawback that the amount of NOx released into the atmosphere increases, and it cannot be operated in locations with strict circulation regulations. Furthermore, since it is necessary to install the auxiliary boiler 51, the equipment cost is high.

The purpose of the present invention is to prevent gas turbine exhaust gas from being released into the atmosphere during high load of the gas turbine with a large amount of NOx (time periods T ₁ and T ₅ in the example of Fig. 2).
Another object of the present invention is to provide a method and apparatus for operating a combined plant that can stop the steam turbine in a high metal temperature state when the plant is stopped without the need to install an auxiliary boiler.

A feature of the combined plant operating method according to the present invention is that the load on the gas turbine is reduced to a low load (50% % or less), and while maintaining this low load, part of the gas turbine exhaust gas is passed through the waste heat recovery boiler.

In addition, the combined plant operating device according to the present invention is characterized by the provision of a blow system with a capacity of 2 to 50% of the total amount of steam generated by the waste heat recovery boiler, which discharges the outlet steam of the waste heat recovery boiler to the blow tank. It is in.

An embodiment of the present invention will be described below with reference to a system diagram of a combined plant according to the present invention shown in FIG. 3 and a start/stop curve diagram shown in FIG. In the system shown in FIG. 3, the same reference numerals as those in FIG. 1 indicate components having the same functions, so a redundant explanation will be omitted. The difference from the configuration in FIG. 1 is that a steam blow pipe 61 is provided which branches from the outlet steam pipe (main steam pipe 31) of the waste heat recovery boiler 2 and connects to a blow tank 63.
This steam blowing pipe is provided with a pressure regulating valve 62, and by controlling the pressure regulating valve 62 with a pressure regulator 64, the steam pressure at the output port of the waste heat recovery boiler 2 is adjusted. According to the inventor's experiments, the capacity of the pressure regulating valve 62 is
In order to perform the operation described later with reference to the figure, it is appropriate that the waste heat recovery boiler 2 has a capacity of 2% or more of the rated steam amount. In addition, from the viewpoint of exhaust steam and economic efficiency of the equipment, a large capacity exceeding 50% is not necessary, and the purpose can be sufficiently achieved with 50% capacity. Note that the capacity of the pressure regulating valve in the prior art is 1% or less of the rated capacity of the waste heat recovery boiler. This is because the operation as described later with reference to FIG. 4 is not taken into account.

Next, with reference to FIGS. 4 and 5, a method for stopping and starting the combined plant shown in FIG. 3 will be explained using a hot start as an example. First, when stopping, in time period _T1 in FIG. 4, as shown in c, the output of the gas turbine 1 starts decreasing (load decreasing), and the load of the steam turbine generator 3 is also decreased. In this case, if the gas turbine and steam turbine are stopped at the same time, the gas turbine exhaust gas temperature will also drop due to the load drop on the gas turbine.
Along with this, the temperature of the steam generated in the waste heat recovery boiler also decreases, so the temperature of the incoming steam when the steam turbine is stopped becomes low, and since the steam turbine is stopped with the metal temperature low, there is a drawback that it is not easy to start the next time.
Therefore, in order to keep the metal temperature of the steam turbine as high as possible when the steam turbine is stopped, the following methods are used as a stopping method:
As shown in FIG. 4b, when the main steam temperature is high, the steam turbine is stopped and excess steam generated from the waste heat recovery boiler 2 is discharged to the condenser 41 through the turbine bypass pipe 47 and the bypass valve 48.

Furthermore, during the time period T ₂ , the load is maintained at a low load with low NOx emissions as shown in Figure 4c (as shown in Figure 5, the combustion temperature is low at low loads, so the NOx amount is low). ), bypass tamper 1
7 is set to an opening close to fully open, and the inlet damper 16 of the waste heat recovery boiler 2 is fully opened, so that most of the exhaust gas amount of the gas turbine 12 bypasses the waste heat recovery boiler 2 and is released into the atmosphere. . (In addition,
Even when the bypass damper 17 is set close to fully open and the inlet damper 16 is fully opened as described above, the pressure loss on the waste heat recovery boiler 2 side is larger than on the bypass duct 18 side, so as shown in FIG. As shown in FIG. 4a, most of the exhaust gas from the gas turbine 12 flows to the bypass duct 18 side, and as shown in FIG. 4b, the main steam temperature is also maintained at a certain level. ) As a result, the amount of steam generated by the waste heat recovery boiler 2 decreases, so the steam generated by the waste heat recovery boiler 2 is blown into the blow tank 63 by adjusting the main steam pressure with the pressure regulating valve 62, and the steam generated by the waste heat recovery boiler 2 is blown into the blow tank 63. Valve 48 is fully closed. Thereafter, the vacuum break valve 49 of the condenser 41 is opened, and when the pressure inside the condenser reaches atmospheric pressure, the steam turbine ₃
3 and 33' are stopped, and the load on the gas turbine 12 is reduced.

Next, startup will be explained. First, before starting the turbine and before applying a load to the steam turbine (T ₄ ,
T ₅ time period and the first half of T ₆ time period)
The bypass damper 17 is set close to fully open, and the inlet damper 16 is set fully open to allow part of the exhaust gas from the gas turbine to flow into the waste heat recovery boiler 2, as shown in FIG. 4d. After starting the gas turbine, the fourth
As shown in Figure f, the gas turbine load is started to increase (that is, the output of the generator 13 is increased) at a time of _T4 , and the load is maintained at a constant low load (50% or less of the rated value). While this load is maintained, the steam generated by the waste heat recovery boiler 2 supplies sealing steam to the glands of the steam turbines 33 and 33',
As shown in FIG. 4e, the degree of vacuum in the condenser 41 is increased. The steam generated in the waste heat recovery boiler 2 cannot be blown into the condenser 41 via the steam turbine bypass valve 48 until the vacuum in the condenser 41 rises.
Blow to 3 (Figure 4e). After _the vacuum rises, when the main steam temperature almost matches the steam turbine metal temperature, the load on the gas turbine 12 increases (that is, the output of the generator 13 increases) and the load on the steam turbine generator 3 is increased during the time period T7. Increase the load by having the robot carry the load.

According to the stop-start method of the above-described embodiment, the metal temperature when the steam turbine is stopped is somewhat lower than that of the conventional method (no auxiliary boiler is provided, and the steam is generated by the gas turbine exhaust at a load of 50% or less). (This results in a slightly lower temperature due to the generation of It is possible to eliminate installation restrictions, and since the steam generated by the waste heat recovery boiler can be used as sealing steam at startup, there is no need for a conventional auxiliary boiler, and the additional equipment is small-scale. Therefore, economicization is achieved.

In the above embodiment, when the plant is stopped or started, the bypass damper is nearly fully open, the inlet damper is fully open, and most of the exhaust gas from the gas turbine is discharged from the bypass duct. When the bypass exhaust flow rate is increased in this way, the blow tank 63
etc. can be reduced. However, as an embodiment different from the above, if the capacities of the steam blow pipe 61, pressure regulating valve 62, and blow tank 63 are increased, the bypass damper 17 is fully closed and the inlet damper 16 is fully open, and the entire amount of gas turbine exhaust gas is converted into waste heat. It is also possible to eliminate the amount of NOx released into the atmosphere from the bypass duct 18 by passing it through the recovery boiler 2, thereby further reducing the amount of NOx released into the atmosphere.

FIG. 6 shows another example of the configuration of an apparatus for carrying out the method of the present invention. In this embodiment, a blow tank connection pipe 65 is provided which branches from the downstream side of the bypass valve 48 of the steam turbine bypass pipe 47 and is connected to the blow tank 63, and a switching valve 66 is provided in the pipe. A switching valve 410 is also installed downstream from the branch point of the pipe 65.

In this embodiment, the switching valve 66 is fully opened, the switching valve 410 is fully closed, and the waste heat recovery boiler 2 is
The generated steam is blown into the blow tank 63 via the turbine bypass valve 48. This embodiment can also achieve the same effects as the previous embodiment.

As described above, the stop/start method of the present invention is as follows:
After the steam turbine is stopped and before the steam turbine is started, the load on the gas turbine is maintained at a low load (50% or less of the rated value), and a portion of the gas turbine exhaust gas is guided to the waste heat recovery boiler. Therefore, the amount of waste gas in the exhaust gas when the gas turbine is under low load is
The amount of NOx is released into the atmosphere because it decreases due to the air-fuel ratio (see Figure 5) and because some of the exhaust gas is discharged through the denitrification device and the amount of NOx becomes extremely small. The amount of NOx can be significantly reduced. These technical characteristics have practical value, especially in combined plants where startup and shutdown are frequent. Furthermore, if the method according to the present invention is implemented, the seal steam for the steam turbine can be supplied from the waste heat recovery boiler, which eliminates the need for an auxiliary boiler for generating seal steam, which was previously required, which greatly contributes to reducing equipment costs. It is.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a general combined plant, Fig. 2 is a stop/start curve diagram of a conventional combined plant, Fig. 3 is a system diagram of a combined plant showing an embodiment of the present invention, and Fig. 4 is a system diagram of a conventional combined plant. A stop-start curve diagram of the combined plant of the invention, Figure 5 is a relationship diagram between gas turbine load and NOx emissions,
FIG. 6 is a system diagram of a combined plant showing another embodiment of the present invention. 1... Gas turbine power generation device, 2... Waste heat recovery boiler, 3... Steam turbine power generation device, 16...
Inlet damper, 17... Bypass damper, 18...
Bypass duct, 21... Superheater, 22... Evaporator, 23... Denitrification device, 24... Drum, 25...
... Economizer, 26 ... Chimney, 31 ... Main steam pipe, 3
2...Steam valve, 33...Steam turbine, 34...
Generator, 35...Gland seal steam piping, 36
... Grand seal steam regulator, 41 ... Condenser, 42 ... Condensate pump, 43 ... Water supply piping, 4
4... Water supply heater, 45... Water supply pump, 47...
...Steam turbine bypass piping, 61...Steam blow pipe, 62...Pressure regulating valve, 63...Blow tank, 64...Pressure regulator.

Claims (1)

[Scope of Claims] 1. A gas turbine, a waste heat recovery boiler that generates steam from the exhaust gas of the gas turbine, a denitrification device that is incorporated into the waste heat recovery boiler and removes nitrogen oxides, and the waste heat recovery In a combined plant that combines a steam turbine driven by steam generated by a boiler, at least a certain period before starting the steam turbine when starting the plant, and a certain period after stopping the steam turbine when stopping the plant. A method for operating a combined plant, the method comprising: maintaining the load of the gas turbine at 50% or less of the rated value during any one of the periods, and passing a portion of the gas turbine exhaust gas through a waste heat recovery boiler during the holding period. . 2. A gas turbine, and a waste heat recovery boiler that generates steam from the exhaust gas of the gas turbine and incorporates a denitrification device for reducing nitrogen oxide emissions;
A combined plant comprising a steam turbine driven by the steam generated by the waste heat recovery boiler, which has a capacity of 2 to 50% of the total amount of steam generated by the waste heat recovery boiler, and A combined plant operating device characterized by being provided with a steam blow system for discharging steam emitted from a recovery boiler into a blow tank. 3. A patent characterized in that the blowing system for discharging the steam emitted from the waste heat recovery boiler into the blow tank is equipped with a pressure adjustment device that adjusts the pressure of the steam emitted from the waste heat recovery boiler. A combined plant operating device according to claim 2. 4. The blow system that discharges the steam emitted from the waste heat recovery boiler to the blow tank is branched from the steam turbine bypass piping that leads the steam emitted from the waste heat recovery boiler to the condenser, and the blow system discharges the steam emitted from the waste heat recovery boiler to the blow tank. 3. The combined plant operating device according to claim 2, wherein the system is configured to guide steam emitted from the recovery boiler to the blow tank via the steam turbine bypass piping.