JP3774487B2 - Combined cycle power plant - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a combined cycle power plant in which, for example, steam generated in a waste incinerator is heated by an exhaust heat recovery boiler that uses exhaust heat of a gas turbine and then supplied to the steam turbine.
[0002]
[Prior art]
In general, power generation facilities that use waste incinerators are planned only to cover the in-house power of the incineration plant, and surplus steam other than the amount of steam used for power generation bypasses the steam turbine and is used as a condenser. It is being collected, and the energy that the garbage has is not necessarily effectively used.
[0003]
However, in order to respond to the tight power demand in recent years and to reduce carbon dioxide emissions, the entire amount of steam can be used for power generation as a large-scale distributed power source, or one step can be taken to achieve higher efficiency. Increasingly, a combined cycle plant having a turbine, a waste heat recovery boiler that uses the waste heat, and a steam turbine facility has been used.
[0004]
FIG. 8 is a schematic system diagram of a combined cycle power plant in which an exhaust heat recovery boiler that uses exhaust heat from a gas turbine is combined with a plant that generates power using steam generated in the waste incinerator 1, Steam generated in the incinerator 1 is supplied to the exhaust heat recovery boiler 2 and overheated there.
[0005]
That is, the exhaust gas duct 3 of the gas turbine 3 is connected to the exhaust heat recovery boiler 2, and the exhaust gas of the gas turbine 3 is supplied to the exhaust heat recovery boiler 2 through the exhaust gas duct 4 and the exhaust heat recovery is performed. A economizer 5, an evaporator 6, and a superheater 7 are provided in the boiler 2, and the main steam pipe 8 of the refuse incinerator 1 is connected to the superheater 7.
[0006]
Thus, the steam generated in the waste incinerator 1 is heated by exchanging heat with the exhaust gas from the gas turbine 3 in the superheater 7 and then passed through the main steam stop valve 9 and the steam control valve 10 to the steam turbine 11. Supplied. The steam supplied to the steam turbine 11 works there to operate the generator 12, while the steam that has worked in the steam turbine 11 is condensed in the condenser 13, and then the condensate pump 14 and the feed pipe 15. Is returned to the waste incinerator 1.
[0007]
A boiler water supply pipe 16 is branched from the downstream side of the condensate pump 14 to the water supply pipe 15, and the boiler water supply pipe 15 is connected to the economizer 5 through a boiler water supply pump 17. A steam drum 18 is connected to the economizer 5, and an evaporator 6 is connected to the steam drum 18, and feed water in the steam drum 18 is supplied to the evaporator 6 by a circulation pump 19. .
[0008]
Accordingly, a part of the water supplied to the water supply pipe 15 by the condensate pump 14 is preheated by the economizer 5 through the boiler water supply pipe 16 and then flows into the steam drum 18 and further heated by the evaporator 6. . The steam generated there is joined with the steam generated in the waste incinerator 1 in the main steam pipe 8.
[0009]
On the other hand, a turbine bypass system 20 is branched and led out from the upstream side of the main steam stop valve 9 to the main steam pipe 8 so that excess steam is discharged to the condenser 13 via the pressure reducing valve 21 and the temperature reducer 22. It is.
[0010]
By the way, in order to cooperate with peak power demand, the gas turbine power generation facility in the combined cycle plant that uses the above-mentioned waste incinerator is required to operate only during the day and stop at night. DSS (Daily Start Stop) operation rather than continuous operation Or, it is common to use WSS (Weekly Start Stop) operation.
[0011]
Further, the steam temperature of the waste incinerator is limited to about 150 to 330 ° C. as a safe range from the relationship between the exhaust gas temperature and the corrosion. Therefore, the steam turbine steam condition for waste power generation is generally set to about 200 to 300 ° C.
[0012]
In the above combined cycle plant using a waste incinerator, the steam from the waste incinerator (steam temperature of about 200 to 300 ° C.) is further combined with the steam generated from the exhaust heat recovery boiler that uses the exhaust heat of the gas turbine. After that, it is heated to about 400 to 500 ° C. with a superheater of an exhaust heat recovery boiler and led to a steam turbine for operation. However, at night, the gas turbine is stopped and steam from a waste incinerator (about 200 to 300 In order to operate the steam turbine at a temperature of about 0 ° C., it is necessary to guide and operate the two main steams having different steam conditions to the steam turbine through the same main steam system in day and night operations.
[0013]
However, in this case, when the operation is switched from daytime to nighttime, the gas turbine is stopped at night, so that the main steam temperature of the steam turbine is about 400 to 500 ° C to about 200 to 300 ° C. Since the temperature changes instantaneously (about 1 to 2 minutes), the gas turbine must be stopped after the load on the gas turbine and the exhaust heat recovery boiler is reduced according to the allowable change rate of the steam turbine inlet temperature. Therefore, the time required for the stop is as long as about 50 to 70 minutes. In addition, when the gas turbine emergency stopped, the steam turbine was once stopped and restarted.
[0014]
On the other hand, the amount of steam from the waste incinerator varies instantaneously due to changes in the amount of waste input and changes in the quality of the waste, so the fluctuating steam amount does not flow into the steam turbine and bypasses the steam turbine to bypass the condenser. Often collected. In addition, the amount of waste incineration and waste heat generated at the time of planning the power plant using the waste incinerator will surely increase in the future, and the amount of steam from the waste incinerator will also increase.
[0015]
However, since the steam turbine inflow steam amount is determined at the time of planning, the increased steam amount is recovered by bypassing it to the condenser.
[0016]
[Problems to be solved by the invention]
As described above, a combined cycle power plant that uses a waste incinerator may sell a small amount of surplus power to an electric power company from the viewpoint of operation, or sell all of it like a wholesale electricity business. It must function as equipment, and respond to DSS and WSS operations, so that it is necessary to reduce the life reduction due to thermal fatigue of equipment caused by repeated start / stop operations. In addition, despite the fact that this power plant is installed from the viewpoint of effective use and increased efficiency of unused energy, the amount of steam increases due to instantaneous changes in the amount of waste steam, future waste incineration, and waste heat generation. There is a problem that cannot be used effectively.
[0017]
On the other hand, as a method of operation, when a steam turbine is conventionally operated and the gas turbine is started later, the gas turbine reaches 100% load in about 8 to 15 minutes, and is thus overheated by the exhaust heat recovery boiler. The main steam temperature rises rapidly. Furthermore, if the gas turbine trips during plant operation, the exhaust heat disappears, so the main steam temperature from the exhaust heat recovery boiler drops sharply and exceeds the steam turbine temperature change allowable value. Therefore, there is a problem that the steam turbine must be stopped and restarted once.
[0018]
In addition, when operating DSS and WSS, in the steam turbine, two types of main steam with different steam conditions are supplied to the steam turbine on the same line during daytime and nighttime operation. Action is required. Moreover, since it is adjacent to the waste incineration plant, it is necessary to make the equipment arrangement as compact as possible.
[0019]
In view of these points, the present invention can effectively use surplus steam even when the amount of steam fluctuates, can continue the operation of the steam turbine even during the above operation, and can be combined in a compact arrangement. The purpose is to obtain a cycle power plant.
[0020]
[Means for Solving the Problems]
A first aspect of the invention is a combined cycle power plant in which steam generated by a steam generator is heated by an exhaust heat recovery boiler that uses exhaust heat of a gas turbine and then supplied to the steam turbine. The inlet nozzle part is divided into a high temperature steam inlet nozzle part and a low temperature steam inlet nozzle part, and the main steam system is branched into two systems connected to the high temperature steam inlet nozzle part and the low temperature steam inlet nozzle part, respectively. A switching valve for supplying steam to either one of the two systems corresponding to the steam temperature is provided in both systems.
[0021]
The second invention is characterized in that air is extracted from an intermediate stage of the superheater of the exhaust heat recovery boiler and the extracted air is supplied to an intermediate stage of the steam turbine.
[0022]
Further, the third invention is characterized in that a part of the steam generated by the steam generator is supplied to the intermediate stage of the steam turbine through the decompressor.
[0023]
According to a fourth aspect of the present invention, a pre-pressure control device is provided that changes the pressure set value of the steam turbine inlet steam pressure in accordance with the steam generator generated steam amount and the opening of the steam control valve.
[0024]
Further, the fifth invention is characterized in that a gas turbine, a generator, and a steam turbine are arranged on one axis, and the gas turbine and the generator, and the generator and the steam turbine are respectively connected via an automatic fitting / removing device. And
[0025]
[Action]
In the first aspect of the invention, even when the main steam temperature during the day and night is different, the operation is continued without stopping the steam turbine by selectively switching the main steam system and the main steam inlet nozzle portion corresponding to the temperature. be able to.
[0026]
Moreover, 2nd invention can supply the extraction air from the intermediate | middle stage of a superheater to the intermediate | middle stage of a steam turbine at the time of a gas turbine starting and a stop. Accordingly, in this case as well, continuous operation can be performed without tripping the steam turbine.
[0027]
In the third aspect of the invention, when the steam generated by the steam generator exceeds the maximum penetration amount of the steam turbine, the surplus steam is supplied to the intermediate stage of the steam turbine. Therefore, the steam from the steam generator can be used effectively.
[0028]
Further, in the fourth invention, the set value of the pre-pressure control of the steam turbine is changed according to the amount of steam from the steam generator. Therefore, even when the steam generated by the steam generator increases, the generated steam can be effectively used without being discharged to the condenser by the turbine bypass.
[0029]
Further, by configuring as in the fifth aspect of the invention, it is possible to save the installation space.
[0030]
Embodiment
Hereinafter, embodiments of the present invention will be described with reference to FIGS. In the figure, the same parts as those in FIG. 8 are denoted by the same reference numerals and detailed description thereof is omitted.
[0031]
In FIG. 1, a main steam pipe 8 that guides steam generated in the waste incinerator 1 to the steam turbine 11 is branched into two steam pipes 25a and 25b on the downstream side of the superheater 7 of the exhaust heat recovery boiler 2, The ends of the steam pipes 25a and 25b are connected to the main steam inlet nozzle portion of the steam turbine 11 which is divided into two.
[0032]
That is, the main steam inlet nozzle portion of the steam turbine 11 includes a high temperature steam inlet nozzle portion 26a that does not need to be throttled as much as possible even when the steam temperature is high, and a low temperature steam inlet nozzle portion that can introduce low temperature steam. The steam pipe 25a is connected to the high temperature steam inlet nozzle part 26a, and the steam pipe 25b is connected to the low temperature steam inlet nozzle part 26b. The steam pipes 25a and 25b are provided with switching valves 27a and 27b, main steam stop valves 9a and 9b, and steam control valves 10a and 10b, respectively.
[0033]
Therefore, in daytime operation, the switching valve 27 a is opened and the switching valve 27 b is closed, and the main steam generated in the waste incinerator 1 is the exhaust heat recovery boiler 2 that uses the exhaust gas generated by the operation of the gas turbine 3. After the temperature is increased, the steam is introduced into the steam turbine 11 from the high temperature steam inlet nozzle portion 26a through the main steam stop valve 9a and the steam control valve 10a.
[0034]
On the other hand, in the nighttime operation, the gas turbine 3 and the exhaust heat recovery boiler 2 that uses the exhaust gas are stopped, so that the temperature of the steam emitted from the exhaust heat recovery boiler 2 is low. Therefore, the switching valves 27a and 27b are switched, the switching valve 27a is closed, the switching valve 27b is opened, and the low-temperature main steam passes through the switching valve 27b, the main steam stop valve 9b, and the steam control valve 10b, and then the low-temperature steam. It is introduced into the steam turbine 11 from the inlet nozzle portion 26b.
[0035]
Therefore, even when switching from daytime operation to nighttime operation, it is possible to cope with a sudden change in the steam turbine inlet temperature without the need to operate the steam control valve significantly. Therefore, even when the gas turbine 3 is in an emergency stop, the operation of the steam turbine 11 can be continued by operating the switching valves 27a and 27b. That is, the two types of main steam at daytime and nighttime can be introduced into the steam turbine through two main steam lines for daytime and nighttime corresponding to the respective volume flow rates.
[0036]
In addition, in this case, even when the exhaust heat recovery boiler 2 is stopped at night, such as in winter, the steam generated in the waste incinerator 1 circulates therethrough, so that the exhaust heat recovery boiler 2 can be prevented from freezing. .
[0037]
In the above embodiment, the main steam pipe is branched downstream of the exhaust heat recovery boiler 2, but may be branched upstream of the exhaust heat recovery boiler 2, as shown in FIG. In this case, steam can be directly introduced into the steam turbine 11 without going through the exhaust heat recovery boiler 2 having a large pressure loss during nighttime operation, and the efficiency can be improved accordingly.
[0038]
FIG. 3 is a view showing still another embodiment of the present invention, and an exhaust heat recovery boiler outlet valve 42 is provided in the main steam pipe 8 for supplying steam from the superheater 7 of the exhaust heat recovery boiler 2 to the steam turbine 11. In addition, the intermediate stage of the superheater 7 and the intermediate stage of the steam turbine 11 are connected by a mixed pressure system 43, and the mixed pressure system 43 is provided with an exhaust heat recovery boiler middle stage outlet valve 44 and a pressure reducing valve 45. It has been.
[0039]
By the way, when the gas turbine 3 is stopped during the normal operation as described above, the exhaust heat of the gas turbine 3 is lost, so that the steam turbine inlet temperature drops rapidly, and the steam turbine temperature change rate is reduced. Therefore, the steam turbine 11 is not preferable because it generates a great amount of thermal stress.
[0040]
Therefore, in the present embodiment, when the gas turbine 3 trips during normal operation, the exhaust heat recovery boiler outlet valve 42 is closed and the exhaust heat recovery boiler middle stage outlet valve 44 is opened. Thus, the steam from the waste incinerator 1 is introduced from the intermediate stage of the superheater 7 into the intermediate stage of the steam turbine 11 via the pressure reducing valve 45. Therefore, the steam turbine 11 can be rotationally driven by the steam supplied to the intermediate stage, and the operation can be continued.
[0041]
FIG. 4 is a view showing still another embodiment of the present invention, in which a mixed pressure steam pipe 46 is branched out from the middle of the main steam pipe 8 for introducing steam from the waste incinerator 1 to the exhaust heat recovery boiler 2. The mixed pressure steam pipe 46 is connected to an intermediate stage of the steam turbine 11 through a control valve 47, a mixed pressure steam stop valve 48, and a mixed pressure steam control valve 49. A pressure detector 50 is provided on the upstream side of the control valve 47, and the control valve 47 is controlled by a vapor pressure signal generated in the refuse incinerator 1 detected by the pressure detector 50. It is like that.
[0042]
Thus, when the amount of steam at the inlet of the steam turbine 11 exceeds the maximum stagnation amount of the steam turbine and the main steam pressure rises, this is detected by the pressure detector 50 and the control valve 47 is opened. Therefore, surplus steam is introduced into the steam turbine 11 through the mixed pressure steam stop valve 48 and the mixed pressure steam control valve 49, and the surplus steam is utilized.
[0043]
Further, when the gas turbine is stopped from the normal operation, the main steam stop valve 9 is closed, and the steam turbine is operated by switching to supplying the steam from the mixed pressure steam system, that is, the mixed pressure steam pipe 46 to the intermediate stage of the steam turbine. Can continue.
[0044]
FIG. 5 is a diagram showing still another embodiment of the present invention, and adjusts the pre-pressure of the steam turbine 11 in order to cope with the case where the amount of steam from the waste incinerator 1 increases beyond the planned value of the steam turbine. A pre-pressure control device 51 is provided.
[0045]
In other words, the main steam pipe 8 that introduces the steam heated by the exhaust heat recovery boiler 2 into the steam turbine 11 is provided with a flow rate detector 52 and a pressure detector 53 that detect the flow rate of the main steam, and the steam adjustment. The valve 10 is provided with an opening degree detector 54. The detection signals from the flow rate detector 52 and the opening degree detector 54 are respectively input to the function generator 55 of the pre-pressure control device 51, where the amount of steam flowing into the steam turbine 11 and the opening degree of the steam control valve 10 are detected. Accordingly, the set value of the pre-pressure of the steam turbine is changed as shown in FIG. 6, and the pre-pressure of the steam turbine is controlled by the set value and the pressure detected by the pressure detector 53.
[0046]
Therefore, when the steam from the waste incinerator 1 increases and the steam control valve 10 of the steam turbine 11 reaches the specified opening, the set value of the steam turbine pre-pressure control is increased, and the condenser bypass 13 is sent from the turbine bypass system. The amount of steam that escapes is limited. Therefore, effective utilization of steam from the waste incinerator is achieved.
[0047]
FIG. 7 is a diagram showing an arrangement relationship of the gas turbine 3, the generator 12 and the steam turbine 11 in the plant as described above, and the gas turbine 3, the generator 12 and the steam turbine 11 are arranged on the same axis. The gas turbine 3 and the generator 12 are connected by an automatic fitting / removing device 56, and the generator 12 and the steam turbine 11 are connected by an automatic fitting / removing device 57. In this case, as shown in FIG. 1 and the like, the installation space can be narrowed and the installation space can be saved as compared with the case where the gas turbine 3 and the steam turbine 11 are separated from each other. .
[0048]
【The invention's effect】
Since the present invention is configured as described above, it can sufficiently cope with changes in waste quality and quantity, and steam generated by a steam generator such as a waste incinerator can be effectively used as energy. Moreover, the change in steam temperature at the inlet of the steam turbine can be alleviated even when the operation of the day and night is changed or when the gas turbine is stopped, and the steam turbine operation can be continued. Moreover, when it installs on one axis | shaft, labor saving of an installation space can also be achieved.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a combined cycle power plant of the present invention.
FIG. 2 is a diagram showing another embodiment of FIG. 1;
FIG. 3 is a diagram showing another embodiment of the present invention.
FIG. 4 is a diagram showing another embodiment of FIG. 3;
FIG. 5 is a view showing still another embodiment of the present invention.
FIG. 6 is an explanatory diagram of changing a pressure set value of the pre-pressure control device.
FIG. 7 is a diagram showing an example of the arrangement of gas turbines and the like.
FIG. 8 is a schematic system diagram of a conventional combined cycle power plant using a waste incinerator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Waste incinerator 2 Waste heat recovery boiler 3 Gas turbine 7 Superheater 8 Main steam pipes 9, 9a, 9b Main steam stop valves 10, 10a, 10b Steam control valve 13 Condenser 20 Turbine bypass system 26a High temperature steam inlet nozzle part 26b Low temperature steam inlet nozzle part 27a, 27b Switching valve 44 Exhaust heat recovery boiler middle stage outlet valve 46 Mixed pressure steam pipe 47 Control valve 51 Pre-pressure control device 55 Function generators 56, 57 Automatic fitting / removing device

Claims (6)

  In a combined cycle power plant in which steam generated by a steam generator is heated by an exhaust heat recovery boiler that uses exhaust heat from the gas turbine and then supplied to the steam turbine, the main steam inlet nozzle of the steam turbine is connected to the high-temperature steam. The main steam system is divided into two systems connected to the high temperature steam inlet nozzle unit and the low temperature steam inlet nozzle unit, respectively, and the steam temperature is divided into the two systems. A combined cycle power plant characterized in that a switching valve for supplying steam to one of the two systems is provided.   The combined cycle power plant according to claim 1, wherein the main steam system connected to the low temperature steam inlet nozzle section is branched upstream of the exhaust heat recovery boiler.   In a combined cycle power plant in which steam generated by a steam generator is heated by an exhaust heat recovery boiler that uses exhaust heat of the gas turbine and then supplied to the steam turbine, an intermediate stage of the superheater of the exhaust heat recovery boiler A combined cycle power plant characterized in that the extracted air is supplied to the middle stage of the steam turbine.   Part of the steam generated by the steam generator in a combined cycle power plant where the steam generated by the steam generator is heated by an exhaust heat recovery boiler that uses the exhaust heat of the gas turbine and then supplied to the steam turbine. The combined cycle power plant is characterized in that is supplied to the middle stage of the steam turbine through a decompressor.   In a combined cycle power plant where the steam generated by the steam generator is heated by an exhaust heat recovery boiler that uses the exhaust heat of the gas turbine and then supplied to the steam turbine, the steam generator generated steam volume and the steam control valve A combined cycle power plant comprising a pre-pressure control device that changes a pressure setting value of a steam turbine inlet steam pressure corresponding to an opening degree.   The gas turbine, the generator, and the steam turbine are arranged on one axis, and the gas turbine and the generator, and the generator and the steam turbine are connected to each other via an automatic fitting / removing device, respectively. The combined cycle power plant according to any one of 5.

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