JPH05209503A - Compound generating plant having steam drum - Google Patents

Abstract

PURPOSE:To simply and quickly carry out the initial pressure changeover operation at the time of start/stop of a gas turbine unit, enhance the speed of response to a load change demand and obviate the wasteful release of main steam energy by jointly communicating steam drums with a plurality of heat-exchangers. CONSTITUTION:In a compound generating plant, a compressor 2 and a generator 3 are connected to a gas turbine 1. The plant is provided with a plurality of heat- exchangers 4-6 in which steam is generated by exchanging heat with the exhaust gas of the gas turbine 1, a plurality of steam drums 12-14 for reserving steam, and a plurality of steam turbines 7-9 in which heated steam is used. In this case, the respective steam drums 7-9 are jointly communicated with the respective heat-exchangers 4-6. For instance, the steam sent from a high-pressure steam drum 12 through a high- pressure drum steam pipe 18 and that sent from a low-pressure steam drum 14 through a low-pressure drum steam pipe 20 are heated via the heat-exchanger 4 respectively, and are sent to the steam turbine side through respective high-pressure and low-pressure main steam pipes 21, 23. Thus, the initial pressure changeover operation at the time of start/stop of respective gas turbine units can be simply and quickly carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined cycle power plant having a steam drum of a type for recovering exhaust heat of a gas turbine, and more particularly to shortening a response time when a load changes accompanying start / stop of a gas turbine and steam. The present invention relates to a combined cycle power plant that contributes to reducing fluctuations in the water level of a drum.

[0002]

2. Description of the Related Art In an exhaust heat recovery type combined cycle power plant, a high temperature exhaust gas of a gas turbine is passed through an exhaust heat recovery boiler consisting of a heat transfer tube group of a heat exchanger to generate steam, and the generated steam is steam drum. The steam stored in the steam turbine is heated and the steam is introduced into the steam turbine. The technical contents of the conventional exhaust heat recovery type combined cycle power plant are, for example, Tohoku Electric Power Co., Inc. Higashi Niigata Thermal Power Station No. 3 series, 10
Details of the design and test operation of the 90 MW combined plant are reported in detail in Mitsubishi Heavy Industries Technical Report Vol. 22, No. 3 (1985-5).

As an example of the configuration of a combined cycle power plant according to the prior art, a multi-axis reheat type plant consisting of three gas turbines and one steam turbine, which is different from the multi-axis non-reheat type in this document, is shown in FIG. Shown in. In a conventional plant, a steam drum is provided for each heat exchanger of an exhaust heat recovery boiler that is attached to each gas turbine, and heat is exchanged with the exhaust gas of each gas turbine to increase the temperature and pressure. The operation of the gas turbine is performed by burning the natural gas with the compressed air from the compressor 2 and guiding the natural gas to the gas turbine 1. The gas temperature at the inlet of the gas turbine reaches nearly 1200 ° C and the exhaust gas temperature is approximately 600 ° C. The steam drum has a multi-pressure structure adapted to different introduced steam pressures such as high-pressure, medium-pressure, and low-pressure turbines constituting the steam turbine, and is designed to have a capacity determined by the heat capacity of the gas turbine exhaust gas and the limit value of the drum water level fluctuation. In this case, because of the triple pressure configuration, three steam drums are provided for each heat exchanger, for example, the heat exchanger 4 is provided with a high-pressure steam drum 50A, an intermediate-pressure steam drum 51A, and a low-pressure steam drum 52A. .. Each steam drum has
A circulating water pipe consisting of a descending water pipe and an evaporation pipe is attached to exchange heat with the exhaust gas, and water is circulated by natural circulation to heat and generate steam. The generated steam is stored in a steam drum for each steam pressure, heated through a heat exchanger, and sent to the steam turbine side through the main steam pipe. However,
The steam of the medium-pressure steam drum 51A is combined with the exhaust steam of the high-pressure steam turbine 7 of the reheat steam pipe 59, heated through a heat exchanger, and sent to the steam turbine side by the medium-pressure main steam pipe 22. Each main steam pipe from the heat exchanger 4 includes a high-pressure main steam mother pipe 24 for introducing steam into a high-pressure steam turbine 7, an intermediate-pressure steam turbine 8, and a low-pressure steam turbine 9, which constitute a steam turbine,
The headers of the medium pressure main steam main pipe 25 and the low pressure main steam main pipe 26 are connected to the main steam pipes from the other heat exchangers 5 and 6. Here, in the case of gas turbine start / stop, etc., the main steam isolation valve is closed while the main steam from each steam drum does not satisfy the temperature and pressure conditions of steam that can be ventilated to the steam turbine.
The flow is adjusted to the turbine bypass valve and released to the reheat steam pipe or condenser. For example, when the gas turbine 1 is additionally started up, when the gas turbine load reaches the rating to obtain sufficient heating by the exhaust gas and the steam pressure of the high-pressure steam drum 50A reaches the ventilation condition of the high-pressure main steam mother pipe 24, the high pressure is increased. The main steam isolation valve 27 is fully opened and the high pressure turbine bypass valve 53 is closed, and the high pressure main steam from the main steam pipes of the other second and third units is merged and the flow rate is adjusted by the turbine control valve 30 to control the pressure. To perform. The exhaust of the high-pressure steam turbine 7 is sent from the high-pressure turbine exhaust mother pipe 46 through the reheater inlet stop valve 36 and the reheat steam pipe 59 to the heat exchanger 4 for reheating and use. Condensed water in the condenser 11 is pressurized by the condensate pump 37 and sent to the heat exchanger 4 by the water supply pipe 60, heated and heated to supply water to each steam drum. In each steam drum, the feed water flow rate is adjusted by the feed water flow rate control valve to control the water level of the steam drum within the operation limit value.

[0004]

In a combined cycle power plant using a plurality of gas turbines, the gas turbine efficiency greatly changes depending on the output, but it is always high by selecting the number of operating gas turbines that matches the plant output. Plant efficiency can be secured. To this end, it is necessary to enable a quick and easy switching operation of the number of operating gas turbines in terms of operation when responding to a plant load change request. However, at the time of starting / stopping the gas turbine unit, an initial pressure switching operation is required in which steam generated from the heat exchanger and steam drum of the unit is made equal to the main steam pressure of the preceding unit and ventilated. Since the operation procedure for this is complicated and the required time is long, the response speed to the load change request is limited, and during that time, the main steam is released by opening the turbine bypass valve, so the main steam energy is also wasted. It is being appreciated. Further, since the pressure and voids of the steam drum change when the unit load increases and the initial pressure is changed, the load change rate is limited to a low level in order to keep the fluctuation of the water level of the steam drum within the limit values.

A first object of the present invention is to improve the response speed to a load change request by simplifying the initial pressure switching operation at the time of starting / stopping the gas turbine unit and shortening the required time, and performing the switching operation. An object of the present invention is to provide a combined cycle power generation plant that does not needlessly release wasteful main steam energy by opening the turbine bypass valve between. A second object of the present invention is to provide a combined power generation plant capable of setting the load change rate of the plant higher than before by reducing fluctuations in the water level of the steam drum at the time of unit load increase and initial pressure switching. ..

[0006]

The object of the present invention is to allow a heat exchanger attached to a gas turbine unit composed of a plurality of plant units to exchange heat with exhaust gas of a gas turbine. This is achieved by sharing steam drums for storing the generated steam with each other and installing a single steam drum for each turbine having different ventilation pressures constituting the steam turbine.

The present invention can be applied to a combined power generation plant having a steam drum, regardless of reheat / non-reheat and multi-axis / single axis.

[0008]

The function of the present invention will be described.

Since the heat exchangers of the exhaust heat recovery boilers attached to the respective gas turbine units are integrated in common for the steam drums, the steam pressure generated at the time of starting (or stopping) the units is different from that of other units. Since it is always the same as the above, the initial pressure switching operation is unnecessary or the required time can be shortened significantly, and the amount of generated steam can be changed by following the increase (or decrease) in the output of the gas turbine. Therefore, the control system configuration and the start / stop operation of the steam turbine can be simplified. Further, since the capacity per steam drum is increased as compared with the conventional one, the pressure control stability against the main steam flow disturbance, the load following speed response, and the drum water level stability are also improved.

[0010]

EXAMPLES Examples of the present invention will be described below.

The first embodiment is shown in FIG. FIG. 1 shows the configuration of a multi-axis reheat type combined power generation plant including three gas turbines and one steam turbine. In the first unit of the gas turbine, natural gas is burned by the compressed air from the compressor 2 to generate driving energy for the gas turbine 1, and the exhaust gas is guided to the heat exchanger 4 by a duct. Less than,
Regarding the gas turbine and the heat exchanger, the first unit will be mainly described, but the same applies to the other second and third units. In this embodiment, the steam turbine has a triple pressure structure including the high-pressure steam turbine 7, the medium-pressure steam turbine 8, and the low-pressure steam turbine 9. Therefore, the steam drums are the high-pressure steam drum 12, the medium-pressure steam drum 13, and the low-pressure steam drum 14. of,
A total of 3 units are installed. If there are multiple steam turbines, install as many steam drums as the number of steam turbines and the ventilation pressure of the turbines. Each high-pressure, medium-pressure, and low-pressure steam drum is equipped with a circulating water pipe consisting of a descending water pipe and an evaporation pipe for exchanging heat with exhaust gas. Although the high-pressure drum circulating water pipe 15 attached to the high-pressure steam drum 12 is omitted in FIG. 1 like each circulating water pipe is shown as a single pipe, it exits the drum and branches to the heat exchanger of each unit. It has a loop structure that serves as a downcomer pipe and as an evaporating pipe consisting of a large number of heat transfer pipes in the ascending portion, exits each heat exchanger, rejoins, and returns to the drum. The circulating water discharged from the steam drum is heated by a heat exchanger and becomes a two-phase flow consisting of a gas phase and a liquid phase in the evaporation pipe portion and contains voids of steam. Circulatingly heated. The two-phase flow entering the steam drum from the evaporation pipe is separated into steam and saturated water by the steam separator, and the generated steam is stored in the steam drum.

In the present invention, the capacity of the integrated steam drum is mainly determined by the heat capacity of the exhaust gas in which a plurality of gas turbine units are integrated. Therefore, the capacity of the integrated steam drum is larger than the capacity of the conventional steam drum installed in each unit. The stability of drum water level fluctuation is also improved. On the other hand, in the present invention, since the circulating water pipe is branched from the integrated steam drum to the heat exchanger of each unit, the circulating water pipe can be compared to the conventional plant in which the steam drum is attached to the heat exchanger of each unit. Although it becomes a little longer, thermal loss can be reduced without problems by passing the pipe through a heat-insulated exhaust duct, and increase in flow pressure loss can be suppressed to a non-problem level by slightly increasing the pipe diameter. Further, when the unit is stopped at a cold temperature, an extra heat loss can be prevented by closing the isolation valve (not shown in FIG. 1) of the circulating water pipe leading to the heat exchanger of this unit.

The steam stored in the high-pressure steam drum 12 and the low-pressure steam drum 14 is heated through the heat exchanger 4 by the high-pressure drum steam pipe 18 and the low-pressure drum steam pipe 20, respectively. It is sent to the steam turbine side through the steam pipe 23. The steam in the medium-pressure steam drum 13 is heated through the heat exchanger and then combined with the exhaust gas of the high-pressure steam turbine 7 in the reheat steam pipe 47, heated again through the heat exchanger, and steamed in the medium-pressure main steam pipe 22. Send to the turbine side. Each main steam pipe from the heat exchanger 4 is a high-pressure main steam mother pipe 2 that introduces steam into a high-pressure steam turbine 7, an intermediate-pressure steam turbine 8, and a low-pressure steam turbine 9 that form a steam turbine.
4, headers of the medium-pressure main steam mother pipe 25 and the low-pressure main steam mother pipe 26 are connected to the main steam pipes from the other heat exchangers 5 and 6. When starting / stopping a gas turbine unit,
As long as the main steam from the heat exchanger of each unit does not satisfy the temperature and pressure conditions of steam that can be ventilated to the steam turbine, it is necessary to close the main steam isolation valve to prevent ventilation and prevent thermal problems. However, in the plant configuration of the present invention, since the steam pressures of the supply sources are the same due to the same steam drum, the time delay until reaching the ventilation condition is small. Therefore, as shown in FIG. 1, a steam bypass pipe, which is required in a conventional plant and which allows steam to escape to a reheat steam pipe or a condenser while adjusting the flow rate with a turbine bypass valve, is provided from each heat exchanger. Since it is not necessary to provide it in the main steam pipe, and a turbine bypass valve for load adjustment is provided in the main steam mother pipe, the turbine control system can be greatly simplified and the load control performance is also improved. Of course, with a greater emphasis on thermal problems, even if a steam bypass pipe for releasing steam from each main steam pipe to the reheat steam pipe or the condenser is provided as in the conventional plant piping configuration, the steam drum of the present invention is also provided. The configuration is possible without any problems. In the embodiment, for example, when the gas turbine 1 is additionally started, the high-pressure main steam isolation valve 27 is gradually adjusted according to the load change rate even if sufficient heating by exhaust gas cannot be obtained before the gas turbine load reaches the rated value. The steam pressure of the high-pressure main steam pipe 21 is made equal to the main steam condition of the preceding unit, and the steam is passed through the heat exchanger 4 at a steam flow rate that matches the heat energy of the exhaust gas. can do. When the ventilation condition of the high-pressure main steam mother pipe 24 is reached, the high-pressure main steam from the main steam pipes of the other second and third units is combined and the turbine control valve 30 controls the main steam flow rate. The exhaust of the high-pressure steam turbine 7 is sent from the high-pressure turbine exhaust mother pipe 46 through the reheater inlet stop valve 36 and the reheat steam pipe 47 to the heat exchanger 4 for reheating and use.
Similarly, when the steam pressure temperature of the intermediate pressure main steam pipe 22 is made equal to the main steam condition of the preceding unit, the intermediate pressure control valve 3 is made to join with the intermediate pressure main steam from the main steam pipes of the other second and third units.
The flow rate is controlled by 1. The exhaust of the medium-pressure steam turbine 8 merges with the low-pressure steam from the low-pressure main steam mother pipe 26 and is ventilated to the low-pressure steam turbine 9.

Condensed water in the condenser 11 is pressurized by the condensate pump 37, heated and heated by the low pressure feed water heater 38, and then fed to the low pressure steam drum 14. Further, the high-pressure water supply pump 39 and the medium-pressure water supply pump 40 respectively increase the pressure to heat and raise the temperature, and supply water to the high-pressure and medium-pressure steam drums. In each steam drum, the feed water flow rate is adjusted by the feed water flow rate control valve to control the water level of the steam drum within the operation limit value. According to the present invention, as in the embodiment shown in FIG. 1, it is possible to increase the capacity of the water supply pumps and reduce the number of the water supply pumps according to the integrated steam drum, but of course, as in the conventional plant,
There is no particular problem even if a water supply pump is installed for each heat exchanger of each unit and the water is heated by the heat exchanger.

The second embodiment is shown in FIG. FIG. 3 shows the configuration of a multi-shaft reheat type combined cycle power generation plant including four gas turbines and one steam turbine. In this embodiment, two heat exchangers of the gas turbine unit share the steam drum. in this case,
Since the steam turbine has a triple pressure configuration, three high pressure steam drums 12A, a medium pressure steam drum 13A, and a low pressure steam drum 14A are installed as steam drums shared by the heat exchangers of the first and second units. There is. Each high-pressure, medium-pressure, and low-pressure steam drum is equipped with a circulating water pipe consisting of a descending water pipe and an evaporation pipe for exchanging heat with exhaust gas.
It is similar to the embodiment. The circulating water pipes attached to each steam drum are abbreviated as single pipes, but
It is a loop structure that exits the drum and branches to the heat exchanger of each unit to become a descending water pipe, and at the rising part becomes an evaporation pipe consisting of a number of heat transfer pipes, exits each heat exchanger, rejoins and returns to the drum. This is also the same as in the first embodiment, and the principle of steam generation does not change. Hereinafter, the first and second units will be mainly described in relation to the gas turbine and the heat exchanger, but the same applies to the other third and fourth units.

The steam stored in the high-pressure steam drum 12A and the low-pressure steam drum 14A is heated by passing through the heat exchanger 4 and the heat exchanger 5, and the high-pressure main steam pipe 21A and the low-pressure main steam pipe 21A are heated.
Send to the steam turbine side at 23A. Also, the medium pressure steam drum 1
Similarly, the steam of 3A is heated through the heat exchanger, then combined with the exhaust of the high-pressure steam turbine 7 through the reheat steam pipe 59A, heated through the heat exchanger again, and sent to the steam turbine side through the intermediate-pressure main steam pipe 22A. .. The main steam pipes of respective pressures, which combine and send the heated steam from the heat exchanger 4 and the heat exchanger 5, respectively send steam to the high-pressure steam turbine 7, the intermediate-pressure steam turbine 8, and the low-pressure steam turbine 9 which constitute the steam turbine. The headers of the high-pressure main steam mother pipe 24, the medium-pressure main steam mother pipe 25, and the low-pressure main steam mother pipe 26 to be introduced are connected to the main steam pipes from the other heat exchangers 6 and 80. In this embodiment, since the steam drums are partially integrated, the pressure temperature state of the main steam is different between the unit groups that share the steam drums but have different gas turbine operating states. Therefore,
When starting / stopping the gas turbine, reheat steam while closing the main steam isolation valve and adjusting the flow rate with the turbine bypass valve while the main steam from each steam drum does not satisfy the temperature and pressure conditions that allow ventilation to the steam turbine. Release to a pipe or condenser. That is, in this embodiment, since the bypass pipe is connected to the main steam pipes from each heat exchanger group in the configuration of the turbine control system in the same manner as in the conventional case, in order to satisfy the temperature and pressure conditions of the vaporizable steam. The initial pressure switching operation of is similar to the switching operation of the conventional plant. Condensate of the condenser 11
The water pressure is increased by the condensate pump 37, and the water supply pipe 60A and the water supply pipe 6
It is sent to the heat exchanger 4 and the heat exchanger 6 by 0B, heated and heated to supply water to each steam drum. In each steam drum, the feed water flow rate is adjusted by the feed water flow rate control valve to control the water level of the steam drum within the operation limit value.

According to the second embodiment of the present invention, since the steam drums of a plurality of units are partially integrated, compared with the conventional plant, the main steam pipes, various valves, etc., especially the steam turbine. The number of surrounding pipes and equipment is small, and plant construction costs can be reduced. Also, in response to a load change request involving switching of the number of gas turbines, by properly selecting the start / stop unit, the initial pressure switching operation can be reduced, the required time can be shortened, and the load change performance can be improved.

FIG. 4 shows a response obtained by a simulation when the load is lowered accompanying the stop of one gas turbine in the combined cycle power plant according to the first embodiment of the present invention. This example involves switching the unit operating number from 3 to 2, and shows a change from 100% load to 67% load.
In the case of the conventional plant, the steam turbine load drops according to the change in the main steam flow rate determined by the load drop and stop of the first unit, and the plant load also drops at the same rate of change. On the other hand, in the case of the present invention, the turbine bypass valve is opened by the load control operation of the turbine control system to release unnecessary main steam, so that the steam turbine load drops quickly,
The settling time can also be greatly reduced from t2 of the conventional plant to t1. As a result, it can be seen that the response performance when the plant load drop request is improved.

FIG. 5 shows a response by simulation at the time of load increase accompanying the start-up of one gas turbine in the combined power plant according to the first embodiment of the present invention. This example involves switching the unit operating number of the gas turbine from two to three, and shows a change from 67% load to 100% load. In the case of the conventional plant, the initial pressure switching operation accompanying the start-up of the first unit is necessary, and the main steam is released by opening the turbine bypass valve until the unit load reaches the rating during that time, so the response speed to the load change request Are limited. After the ventilation conditions are satisfied, ventilation is started by closing the turbine bypass valve, the main steam flow rate increases, and the steam turbine load increases. Therefore, the plant load increases with the unit load and then becomes a constant output, and increases with the steam turbine load to the rated value. On the other hand, in the case of the present invention, the time required for the main steam from the startup unit heat exchanger to reach the ventilation condition is short and the initial pressure switching required time can be shortened, so the steam turbine load rises quickly. Therefore, it can be seen that the settling time can be greatly reduced from t2 of the conventional plant to t1 and the response performance when the plant load increase is requested can be improved.

FIG. 6 shows a simulation response of the water level of the steam drum when the main steam flow disturbance is input in the combined cycle power plant according to the first embodiment of the present invention. In this example, the response of the pressure and water level of the steam drum is observed by inputting the main steam flow disturbance that rapidly increases the gas turbine load and the steam turbine load of the starting unit. According to the plant response of the present invention, since the steam drum capacity is increased as compared with the conventional plant, the pressure fluctuation is small and therefore the fluctuation of the drum water level is also small, and the drum stability is further improved.

[0021]

According to the present invention, since the steam drums of a plurality of units are integrated, it is possible to significantly reduce the initial pressure switching operation in response to a load change request involving switching of the number of gas turbines. Time can be shortened and load change performance can be improved. Further, since the capacity of the integrated steam drum is larger than the capacity of the steam drum installed in each conventional unit, the water level fluctuation of the steam drum is reduced and the water level stability is further improved. Further, compared to the conventional plant, the number of main steam pipes, various valves such as pipes around the steam turbine, and the number of devices are small, and the plant construction cost can be reduced.

[Brief description of drawings]

FIG. 1 is a system diagram of a combined cycle power generation plant in which a steam drum is shared by a heat exchanger in a first embodiment of the present invention.

FIG. 2 is a system diagram of a multi-axis reheat type combined cycle power plant according to a conventional technique.

FIG. 3 is a system diagram of an integrated power plant in which a steam drum is partially integrated according to a second embodiment of the present invention.

FIG. 4 is a response characteristic diagram at the time of load drop accompanying the stop of one gas turbine in the combined cycle power plant according to the first embodiment of the present invention.

FIG. 5 is a response characteristic diagram at the time of load increase accompanying the startup of one gas turbine in the combined cycle power plant according to the first embodiment of the present invention.

FIG. 6 is a response characteristic diagram of the steam drum water level when the main steam flow disturbance is input in the combined cycle power plant according to the first embodiment of the present invention.

[Explanation of symbols]

1 ... Gas turbine, 2 ... Compressor, 3 ... Generator, 4, 5,
6 ... Heat exchanger, 7 ... High pressure steam turbine, 8 ... Medium pressure steam turbine, 9 ... Low pressure steam turbine, 10 ... Generator, 11 ...
Condenser, 12, 12A, 12B ... High-pressure steam drum, 1
3,13A, 13B ... Medium pressure steam drum, 14,14A, 1
4B ... Low pressure steam drum.

Claims (6)

[Claims] 1. A plurality of gas turbines, a plurality of heat exchangers for exchanging heat with exhaust gas of the gas turbine to generate steam, a steam drum for storing the generated steam, and heating the stored steam for use. In the combined power generation plant including the steam turbine, the combined power generation plant is characterized in that the steam drum is shared by the plurality of heat exchangers. 2. The steam drum of claim 1, wherein the plurality of heat exchangers share the same steam drum, and steam drums having steam pressures corresponding to different introduced steam pressures differ depending on turbines constituting the steam turbine. , A combined power plant with equal number of steam turbines. 3. The heat exchanger according to claim 1, wherein the entire heat exchanger is divided into a plurality of heat exchanger groups, and a steam drum shared by the heat exchangers is installed. The steam of the steam drum is introduced through the heat exchanger. A combined cycle power plant configured to lead to a main steam pipe mother pipe connected to each turbine with different steam pressure. 4. The high-pressure steam turbine exhaust steam as claimed in claim 1, which is obtained by adding steam from an intermediate-pressure steam drum to steam heated through the heat exchanger and heating the steam again through the heat exchanger. A combined cycle power plant with a reheat plant that uses the generated steam as the steam introduced into the medium-pressure turbine. 5. The steam according to claim 2, wherein the steam of the steam drum is passed through the heat exchanger, the steam is guided to a main steam pipe mother pipe to be introduced steam of the steam turbine, and the steam is bypassed from the turbine. Therefore, a combined cycle power plant is provided with a bypass pipe branching from the main steam pipe mother pipe. 6. The water supply pipe according to claim 1, wherein a water supply pipe for branching water is provided for each of the steam drums having different steam pressures, and a water supply pump for increasing the supply water in accordance with the steam pressure and a water supply for raising the temperature. A combined cycle power plant having a configuration in which a heater is added to the water supply pipe.