JPH0682003A - Full fired heat recovery combined cycle power plant - Google Patents

Abstract

PURPOSE:To prevent overheat from occurrence when the flow rates of condensed water and feed water have lowered. CONSTITUTION:With lowering of the load of a steam turbine, the flow rates of condensed water and feed water are lowered so that the feed water and the condensed water may be subjected to overheating. In that case, a condensed water temperature detector detects the temperature of the condensed water which has passed through a low pressure gas superheater 7 and a circulation pump 21 is driven based on the detected temperature and the condensed water which has passed through the low pressure gas superheater 7 incorporated into a condensed water communication pipeline 20 where the condensed water joins the condensed water of a supply pipe 41 and it is returned to the low pressure gas superheater 7. More specifically, the condensed water is circulated, which makes it possible to prevent the condensed water from being overheated even when the reduction of heat exchange quantity of the low pressure gas superheater is minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas re-combustion combined cycle power plant, particularly when the plant is in operation.
The present invention relates to a device suitable for preventing overheating (steaming) of feed water and condensate passing through a gas heater.

[0002]

2. Description of the Related Art FIG. 4 shows a part of a cycle configuration of a conventional exhaust gas re-combustion combined power plant mainly used in Europe. About 13 to 15% of O2 remains in the exhaust gas from the gas turbine 1, and the exhaust gas is introduced into the boiler wind box 4 as the steam generator 4 and the steam generating boiler 3 to be used as combustion air. Due to
Generates steam. Exhaust gas from the steam generating boiler 3 is 3
It has a high temperature of about 50 ° C., and heat is recovered through the high pressure gas heater 6 and the low pressure gas heater 7 connected in parallel (or series) with the high pressure feed water heater 19 and the low pressure feed water heater 15 of the steam turbine cycle. By doing 10
After being cooled to about 0 to 150 ° C., it is discharged into the atmosphere from the chimney 9 through the induced draft fan 8. on the other hand,
Condensed water from the condenser 10 is boosted by the condensate pump 11, passes through the gland steam condenser 12 and the deaerator water level adjusting valve 13 and enters the condensate distribution valve 14, and the distribution valve 14 bidirectionally. It is divided and flows out. In this case, one side is heated by the low-pressure feed water heater 15, and the other side is heated by the low-pressure gas heater 7.
After passing through the inside, it joins the condensate heated by the low-pressure feed water heater 15, and the combined condensate is guided to the deaerator 16. In the deaerator 16, dissolved oxygen and carbon dioxide gas in the condensate are removed in order to prevent the boiler and the like from being corroded, and the removed condensate flows out in two directions by the feed water distribution valve 18. In this case, on the one hand, the pressure and temperature are raised to the desired pressure by the high-pressure feed water heater 19, and on the other hand, after passing through the high-pressure gas heater 6, it joins the condensate that has passed through the high-pressure feed water heater 19 as described above. Then, the steam is generated by being guided to the steam generating boiler 3.

[0003]

In the prior art described above, the exhaust gas from the steam generating boiler 3 is heat-recovered by the feed water in the high-pressure gas heater 6 and the condensate is recovered in the low-pressure gas heater 7. By doing so, it has higher thermal efficiency than a general steam engine plant. However, in the exhaust gas re-combustion combined plant of the prior art, when the load of the steam turbine is lowered, the flow rate of the feed water flowing through the high pressure gas heater 6 and the flow rate of the condensate flowing through the low pressure gas heater 7 are also reduced. Since the decrease in the amount of heat exchange between the high-pressure gas heater 6 and the low-pressure gas heater 7 is small with respect to the decrease in the flow rate of the supplied water and the condensate, the high-pressure gas heater 6 superheats the supplied water and the low-pressure gas overheats. Bowl 7
There is a problem that the condensate is also overheated.

More specifically, the feed water flow rate and the condensate water flow rate are reduced when the load on the steam turbine decreases, and as shown in FIG. 5, the low / high pressure gas superheaters 7.6 and the low / high pressure feed water superheaters are shown. Both 15 and 16 decrease, and the heat exchange amount in the low / high pressure gas superheaters 7 and 6 also decreases as shown in FIG. However, as shown in FIGS. 5 and 6, the amount of decrease in the heat exchange amount is smaller than the amount of decrease in the feed water flow rate and the condensate flow rate. As a result, the condensate and feed water flowing through the low-pressure gas superheater 7 and the high-pressure gas superheater 6 are overheated, and as a result, the temperature of the condensate at the inlet of the deaerator 16 and the deaerator are reduced. It becomes difficult to secure the difference (ΔT) with the internal temperature to a desired value, and there is not only a problem that the degassing effect decreases, but also a problem that steaming occurs at the inlet of the deaerator 16 and the boiler economizer. There is. Further, when the feed water flow rate and the condensate flow rate are extremely reduced due to the reduction of the steam turbine load, the low / high pressure gas heaters 7 and 6 themselves are also overheated, and especially in the condensate system, the water level of the deaerator is high. When the water level is reached, the deaerator water level adjustment valve is temporarily closed to drastically reduce the condensate flow rate, which causes a problem that the low-pressure gas superheater 7 is abnormally overheated.

In view of the above circumstances, an object of the present invention is to provide an exhaust gas reburn type which can reliably prevent the condensate and the feed water from being overheated when the flow rates of the condensate and the feed water passing through the gas superheater decrease. To provide a combined cycle power plant.

[0006]

In the present invention, when the flow rates of condensate and feed water passing through the gas superheater decrease,
It has a reflux circulation device that takes in the condensate water and feed water that have passed through the gas superheater, and recirculates the taken in condensate water and feed water to the corresponding gas superheater.

[0007]

[Operation] When the steam turbine load decreases and the flow rates of the condensate water and the condensate water flowing to the respective gas superheaters also decrease, the temperatures of the condensate water and the condensate water passing through the gas superheater rise abnormally, and they tend to be overheated. . However, in that case, since the recirculation circulation device is provided as described above, since the condensate water and the feed water that have passed through the gas superheater are taken by the recirculation circulation device and recirculated to the respective gas superheaters, they pass through the gas superheaters. Therefore, the condensate and the feed water can be prevented from overheating even if the amount of heat exchange in the gas superheater is small.

[0008]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows a first embodiment of an exhaust gas re-combustion combined cycle power plant according to the present invention. In the embodiment shown in the figure, the exhaust gas discharged from the gas turbine 1 is guided to a boiler wind box 4 as a steam generator and reburned in the boiler together with the fuel charged in the boiler 3. Then, the exhaust gas from the boiler 3 passes through the boiler exhaust gas duct 5 and is subjected to heat recovery by the high pressure gas heater 6 by the feed water, and further is recovered by the low pressure gas heater 7 by the condensate to be lowered to about 100 to 150 ° C. After that, it is discharged to the atmosphere from the chimney 9 through the induced draft fan 8. On the other hand, the condensate from the condenser 10 is boosted by the condensate pump 11, and the gland steam condenser 12 and the deaerator water level adjusting valve 1
After entering the condensate water distribution valve 14, the water is distributed to the low pressure feed water heater 15 and the low pressure gas heater 7 by the condensate water distribution valve 14. At this time, the condensate distribution valve 14 has the low-pressure feed water heater 15
The distribution amount is adjusted and distributed so that the temperature of the condensate that has passed through and the temperature of the condensate that has passed through the low-pressure gas heater 7 are the same, but when the turbine load decreases, it is transferred to the low-pressure gas superheater 7 side. When the flow rate of condensate to be sent is increased and the turbine load is further reduced, the condensate flow rate to be sent to the low pressure feed water superheater 15 is cut to send the entire amount of condensate to the low pressure gas superheater 7, and the turbine load is further increased. When it is further lowered, it is opened again to send a small flow rate to the low pressure gas superheater 7 and the low pressure feed water superheater 15. The condensate that has passed through the low-pressure feed water heater 15 and the condensate that has passed through the low-pressure gas heater 7 are combined and then sent to the deaerator 16, and the deaerated by the deaerator 16 is supplied. The water supply from the deaerator 16 is pumped by the water supply pump 17 into the water supply distribution valve 18, and is distributed by the water supply distribution valve 18 to the high pressure water supply heater 19 and the high pressure gas heater 6. At this time, the feed water distribution valve 18 adjusts and distributes the distribution amount so that the temperature of the feed water passing through the high pressure feed water heater 19 and the temperature of the feed water passing through the high pressure gas heater 6 are the same. Further, the feed water that has passed through the high-pressure feed water heater 19 and the feed water that has passed through the high-pressure gas heater 6 are joined and then guided to the boiler 3.

In the embodiment, the condensate that has passed through the low pressure gas superheater 7 and the feed water that has passed through the high pressure gas superheater 6 are respectively taken in and returned to the low pressure gas superheater 7 and the high pressure gas superheater 6. It has a reflux circulation device. The reflux circulation device is roughly classified into a condensate connecting pipe 20 that connects the inlet side and the outlet side of the low-pressure gas heater 7, and a water supply that connects the inlet side and the outlet side of the high-pressure gas heater 6. Connecting pipe 28, a reflux circulation mechanism (not shown) for condensate for returning condensate from the low pressure gas superheater 7 to the low pressure gas superheater 7, and feed water from the high pressure gas superheater 6 A high-pressure gas superheater 6 is provided with a reflux circulation mechanism for water supply. More specifically, the condensate connecting pipe 20 has one end connected to an intermediate position of the condensate supply pipe 41 connecting the condensate distribution valve 14 and the inlet side of the low-pressure gas heater 7, and the other end. Is connected to an intermediate position of the discharge pipe 42 that connects the outlet side of the low pressure gas heater 7 and the outlet side of the low pressure feed water heater 15.
In the reflux circulation mechanism for condensate, the temperature detector 25 is provided at a position near the low pressure gas heater 7 in the condensate discharge pipe 42,
A low flow rate detector 26 is provided at a position downstream of the temperature detector 25.
Is provided. A circulating pump 21, a condensate temperature adjusting valve 22, a circulating water temperature adjusting valve 23, a cooling device 24, and a circulating water temperature detector 27 are installed in the connecting pipe 20, respectively. When the flow rate of the condensed water passing through the low-pressure gas superheater 7 decreases due to the further decrease of the steam turbine load, the temperature of the reflux circulation means rises due to the overheating of the condensed water. When the temperature rises above the desired temperature, the temperature detector 25 detects the temperature and drives the circulation pump 21 to take in the condensate from the low-pressure gas superheater 7 into the connecting pipe 20 and to supply the condensate supply pipe 41. By circulating the condensate to the low pressure gas superheater 7,
The flow rate of condensed water passing through the low pressure gas superheater 7 is increased. In that case, if the temperature of the condensate that has passed through the connecting pipe 2 is high, it may be overheated even if it is sent to the low-pressure gas superheater 7. Therefore, the temperature of the condensate that has passed through the cooling device 24 is detected as the circulating water temperature. Is detected by the device 27, and the circulating water temperature adjusting valve 23 is throttled according to the detection, and the circulating condensate is cooled by the cooling device 24, so that the temperature difference between the circulating condensate and the supplied condensate is adjusted to be small. ing. Further, when the water level of the feed water in the deaerator 16 rises due to the extremely small amount of condensed water passing through, the deaerator water level adjusting valve 1
3 is closed and the condensate supplied from the condensate distribution valve 14 to the condensate supply pipe 41 is stopped, so that the condensate flow rate passing through the low-pressure gas superheater 7 decreases, but the condensate flow rate falls below the specified amount. In this case, the condensate low flow rate detector 26 detects this, thereby increasing the driving force of the circulation pump 21 and further opening the temperature adjusting valve 22 to circulate the condensate.

Further, one end of the water supply connecting pipe 28 is connected to an intermediate position of the water supply supply pipe 43 which connects the water supply distribution valve 18 and the inlet side of the high pressure gas heater 6, and the other end is heated by the high pressure gas. It is connected to an intermediate position of a feed water discharge pipe 44 that connects the outlet side of the vessel 6 and the outlet side of the high-pressure feed water heater 19.
The recirculation circulation mechanism for water supply is provided with a water supply temperature detector 33 at a position near the high pressure gas superheater 6 of the discharge pipe 44, and the communication pipe 28 has a circulation pump 29 similar to the recirculation circulation mechanism for condensate. , Supply water temperature adjusting valve 30, circulating water temperature adjusting valve 31,
A cooling device 32 and a temperature detector 34 are provided respectively.
When the flow rate of the feed water passing through the high-pressure gas superheater 6 decreases due to the further reduction of the turbine load, this recirculation circulation mechanism operates similarly to the condensate recirculation circulation mechanism, so that the high-pressure gas superheater 6 Since the water supply is cooled and circulated, the following description will be omitted. However, in this case, the circulation pump 29 and the temperature adjustment valve 30 are controlled based on the detection of the feed water temperature detector 33.

Next, the operation of the embodiment will be described. During normal operation, the condensate from the condenser 10 is boosted by the condensate pump 11, and the gland steam condenser 12 and the deaerator water level adjusting valve 1
3 enters the condensate distribution valve 14, and the condensate distribution valve 14 divides the condensate into the low-pressure gas superheater 7 side and the low-pressure feed water superheater 15 side. Therefore, since the condensate is sent to the low-pressure gas superheater 7, it is heated by exchanging heat with the exhaust gas from the boiler 3, and the heated condensate joins the condensate that has passed through the low-pressure feed water heater 15. , Sent to the deaerator 16. The feed water deaerated in the deaerator 16 is boosted by the feed water pump 17 and sent to the high pressure gas heater 6 side and the high pressure feed water heater 19 side by the feed water distribution valve 18. Therefore, since the feed water is sent to the high-pressure gas heater 7, it is heated by exchanging heat with the exhaust gas from the boiler 3, and the heated feed water joins the feed water that has passed through the high-pressure feed water heater 19, and the boiler 3 Is supplied to.

In the above operation, when the steam turbine load decreases, the flow rates of the condensate water and the supply water decrease according to the load. Compared with the decrease amount, the heat exchange amount of the high and low pressure gas heaters 6 and 7 High / low pressure gas heater 6 ・
Condensate and water passing through 7 may heat up. In this case, the condensate distribution valve 14 increases the flow rate of the condensate sent to the low-pressure gas heater 7 side, and the feed water distribution valve 18 increases the flow rate of the feed water sent to the high-pressure gas heater 6 side. And prevent the water supply from overheating. Then, when the steam turbine load further decreases, both the condensate water distribution valve 14 and the feed water distribution valve 18 cut the condensate water to the low pressure water supply superheater 15 side and cut the water supply to the high pressure water supply superheater 19 side. However, the condensate water and the feed water are prevented from overheating by increasing the flow rates of the condensate water and the feed water flowing through the low pressure gas superheater 7 and the high pressure gas superheater 6. After that, when the steam turbine load further decreases, the condensate flow rate and the feed water flow rate further decrease, and the temperature of the feed water and the condensate water passing through the high / low pressure gas superheaters 6 and 7 abnormally rises, resulting in overheating. Trying to be done. In that case, however, the condensate temperature detector 25 has a reflux circulation device, and the condensate temperature detector 25 detects the temperature of the condensate that has passed through the low-pressure gas superheater 7, and the circulation pump 21 is driven based on that temperature, so that the low-pressure gas Condensate that has passed through the superheater 7 is taken into the condensate connecting pipe 20, merges with the condensate in the supply pipe 41, and is returned to the low-pressure gas superheater 7.
Therefore, since the condensate that has passed through the low-pressure gas superheater 7 is recirculated by the reflux circulation device, the flow rate of the condensate that passes through the low-pressure gas superheater 7 increases, and the reduction amount of the heat exchange amount of the low-pressure gas superheater is small. Together, it is possible to prevent the condensate from overheating. Moreover, the temperature of the condensate passing through the connecting pipe 20 is detected by the circulating water temperature detector 27, the opening degree of the circulating water flow rate temperature adjusting valve 23 is adjusted based on the detection, and the condensate is cooled by the cooling device 24. Since the temperature is adjusted, the difference between the temperature of the circulating condensate and the temperature of the condensate to be combined can be minimized. Therefore, even if the temperature of the condensate that has passed through the low pressure gas superheater 7 rises, it is cooled by the cooling device 24, so that the condensate that passes through the low pressure gas superheater 7 can be reliably prevented from being overheated.

On the other hand, in the reflux circulation device, the feed water temperature detector 33 detects the temperature of the feed water that has passed through the high-pressure gas superheater 6, the circulating pump 29 is driven based on the temperature, and the feed water temperature adjusting valve 30 is also provided. Is opened, the feed water that has passed through the high pressure gas superheater 6 is taken into the water supply connecting pipe 28, merges with the feed water in the supply pipe 43, and is returned to the high pressure gas superheater 6. Therefore, the flow rate of the feed water passing through the high pressure gas superheater 6 is increased by the reflux of the feed water passing through the high pressure gas superheater 6, so that the condensate water is condensed even if the decrease amount of the heat exchange amount of the high pressure gas superheater 6 is small. As with the above, it is possible to prevent the water supply from overheating. Further, the temperature of the supply water passing through the connecting pipe 28 is detected by the circulating water temperature detector 34, the opening degree of the circulating estimated temperature adjusting valve 31 is adjusted based on the detection, and the cooling water is cooled by the cooling device 32. Therefore, the difference between the temperature of the circulating supply water and the temperature of the supply water to be joined can be minimized. Therefore, even if the temperature of the feed water that has passed through the high-pressure gas superheater 6 rises, it is cooled by the cooling device 24, so that overheating of the feed water can be reliably prevented. As a result, it is possible to prevent overheating of the condensate water and the feed water, and thus it is possible to easily secure a difference (ΔT) between the temperature of the condensate water at the inlet of the deaerator 16 and the temperature in the deaerator, and therefore the deaeration It is possible to prevent the degassing effect of the device 16 from decreasing and prevent steaming at the deaerator inlet and the economizer.

Further, the water level in the deaerator 16 rises due to the extreme decrease in the steam turbine load, and the deaerator water level adjusting valve 13 closes, so that the flow rate of the condensate on the low pressure gas superheater 7 side is regulated. When the flow rate falls below the amount, the low flow rate detector 26 detects the flow rate of the condensate that has passed through the superheater 7, the circulation pump 21 is driven based on the detection, and the opening degree of the temperature adjustment valve is adjusted. Circulate the condensate again. Therefore, even if the amount of condensed water decreases due to the closing of the deaerator water level adjustment valve 13, the condensed water is circulated, so that the low pressure gas superheater 7 can be prevented from overheating. When the deaerator water level adjustment valve 13 is closed, the deaerator 16 will not be supplied with water, but the water whose level has risen is passed through the deaerator 16, the water supply pump 17, and the water supply distribution valve 18 to the high pressure gas superheater. Since it is sent to 6, the feed water passing through the high pressure gas superheater 6 will not be overheated.

FIG. 2 shows a second embodiment of an exhaust gas reburn type combined cycle power plant according to the present invention.
This embodiment differs from the first embodiment in that a condenser 10 is used instead of the circulating water cooling device of the reflux circulation device, and the circulating water is cooled by the condenser 10. is there. More specifically, this reflux circulation device is a connection pipe 20 that guides the condensed water from the low-pressure gas superheater 7 to the condenser 10.
And the condensate cooled by the condenser 10 to the condensate supply pipe 4
1 to the circulating water return pipe 36. A temperature detector 25 is provided at a position near the low-pressure gas superheater 7 in the condensate discharge pipe 42, a circulating water flow rate detector 35 is provided at an intermediate position of the connecting pipe 20, and a position on the downstream side thereof is provided. A temperature control valve 22 is provided in the. Further, the circulating pump 21 is provided at an intermediate position of the circulating water return pipe 36, and the circulating water flow rate adjusting valve 37 is provided on the downstream side thereof. A low flow rate detector 26 is provided on the downstream side of a confluent portion of the condensate discharge pipe 42 with the connecting pipe 20.
When the steam turbine load further decreases and the flow rate of the condensate decreases, the temperature of the condensate passing through the low-pressure gas superheater 7 rises, which is detected by the temperature detector 25. The condensate that has passed through the low-pressure gas superheater 7 is guided to the condenser 10 by adjusting the opening degree of the temperature control valve 22 based on the condensate 10, and is cooled by heat exchange in the condenser 10, while the circulation pump is used. 21 is driven, the cooled condensed water from the condenser 10 is circulated.
Through the low pressure gas superheater 7. At that time, the circulating water flow rate detector 35 detects the flow rate of the condensed water passing through the connecting pipe 20,
By adjusting the opening degree of the circulating water flow rate control valve 37 based on the detection, the amount of condensed water passing through the connecting pipe 20 and the amount of condensed water passing through the circulating water return pipe 36 become the same. I have to. Further, it has a connecting pipe 28 that guides the feed water from the high-pressure gas superheater 6 to the condenser 10, and a circulating water return pipe 39 that guides the condensate cooled by the condenser 10 to the feed water supply pipe 43. . Further, a temperature detector 33 is provided at a position near the high-pressure gas superheater 6 in the feed water discharge pipe 44, and a circulating water flow rate detector 38 and a temperature adjusting valve 30 are provided at intermediate positions of the communication pipe 28 to circulate. A circulating pump 29 and a circulating water flow rate adjusting valve 40 are provided in the middle of the water return pipe 39, respectively. When the steam turbine load is further reduced and the flow rate of the feed water is reduced to raise the temperature of the feed water passing through the high pressure gas superheater 6, the temperature detector 33 detects it and the temperature control valve is detected based on the detection. By adjusting the opening degree of 30, the feed water that has passed through the high-pressure gas superheater 6 is guided to the condenser 10 and cooled by heat exchange in the condenser 10, while the circulation pump 29 is driven. Thereby, the condensed condensate from the condenser 10 is guided to the high-pressure gas superheater 6 through the circulating water return pipe 39, at that time.
The flow rate of the supply water passing through the connecting pipe 28 is determined by the circulating water flow rate detector 3
8 detects the circulating water flow rate adjusting valve 40 based on the detection.
The amount of water supply passing through the connecting pipe 28 and the amount of condensate water passing through the circulating water return pipe 39 are adjusted to be the same by adjusting the opening degree.

Therefore, according to this embodiment, the condenser 10
Since the condensate water and the feed water that have passed through the high / low pressure gas superheaters 6 and 7 are cooled by utilizing the above, the same effect as that of the first embodiment described above can be obtained, and in addition, the first embodiment Compared with the example, it is not necessary to use a dedicated cooling system, so that the cost can be reduced accordingly.

FIG. 3 shows still another embodiment of the exhaust gas re-combustion combined cycle power plant according to the present invention. In the above embodiments, the high / low pressure gas superheaters 6 and 7 are used.
The heat exchange rate of the low pressure gas superheater 7 is higher than that of the high pressure gas superheater 6 in the present embodiment. Applied to. That is, in this embodiment, on the low pressure gas superheater 7 side, as in the embodiment shown in FIG. 2, the connecting pipe 20, the temperature detector 25, the condensate temperature adjusting valve 22, the circulating water return pipe 3 are provided.
6, the circulation pump 21, the circulating water flow rate detector 35, the circulating water flow rate adjusting valve 37, and the condensate low flow rate detector 36 are provided to constitute a reflux circulation device. In that case, the upstream side of the circulating water return pipe 36 is connected to the discharge side of the condensate pump 11, and a part of the condensate discharged from the pump 11 is supplied to the deaerator water level adjusting valve 13 and the condensate distribution valve. It is possible to prevent the condensate water passing through the low pressure gas superheater 7 from being overheated by forcibly guiding it to the low pressure gas superheater 7 regardless of the number 14.

Generally, when the heat exchange rate of the low pressure gas superheater 7 is higher than that of the high pressure gas superheater, the low pressure gas superheater 7
Condensate passing through the side may be overheated, but overheating can be prevented by always forcing the condensate to the low-pressure gas superheater 7 as in the above-described embodiment. Moreover, since it is sufficient to provide the reflux circulation device only on the low-pressure gas superheater side, the number of parts can be greatly reduced. Incidentally, in the above-mentioned embodiments, in each case, the example in which the reflux circulation device is used when the turbine load is low is shown, but in the present invention,
The present invention is not limited to this, and can be sufficiently applied even when the steam engine plant is in a start-up operation or a no-load operation, and the condensate and feed water flow rates are low. Of course.

[0019]

As described above, according to the first aspect of the present invention, even if the feed water amount and the condensate amount passing through the gas superheater decrease due to the reduction of the load, the feed water passing through the gas superheater and Since the amount of water supply and the amount of condensate water are increased by circulating the condensate water, it is possible to reliably prevent the water supply and the condensate water from being overheated by the gas superheater. According to claim 2, since the reflux circulation device is configured to have the water supply connection pipe, the condensate connection pipe, and the circulation circulation means, the same effect as that of claim 1 can be obtained, and according to claim 3, In addition to the effect of claim 2, since the feed water and the condensate that have passed through the gas superheater are cooled and circulated,
Achieving overheat prevention of water supply and condensate without fail and preventing the degassing effect from decreasing, and also preventing steaming at the deaerator inlet and economizer, there is a practically useful effect. According to claim 4, in addition to the effect of claim 3, since the flow rate of the circulating water is adjusted by the flow rate adjusting means, even if the condensate from the condenser is no longer supplied to the gas superheater, the gas superheat It has the effect of not overheating the vessel. According to claim 5, by using the condenser, it is possible to surely achieve the prevention of overheating of the water supply and the condensate, and there is the same effect as in claim 3, and moreover, by using the condenser. The use of a dedicated cooling device is also unnecessary. According to claim 6, in addition to the effect of claim 5, the condensate is overheated even if the condensate passing through the gas superheater is drastically reduced. Since this can be prevented, the same effect as in claim 4 can be obtained. According to claim 7, when the heat exchange rate on the low-pressure gas superheater side is high, only by providing the reflux circulation device on the low-pressure gas superheater side,
Since overheat can be prevented, there is also an effect that the configuration can be simplified.

[Brief description of drawings]

FIG. 1 is a piping diagram showing a first embodiment of an exhaust gas re-combustion combined cycle power plant according to the present invention.

FIG. 2 is a piping diagram showing another embodiment of the present invention.

FIG. 3 is a piping diagram showing still another embodiment of the present invention.

FIG. 4 is a piping diagram showing a conventional example.

FIG. 5 is an explanatory diagram showing the relationship between the load of the steam turbine and the feed water / condensate flow rate.

FIG. 6 is an explanatory diagram showing a relationship between a steam turbine load and a gas superheater exchange heat quantity.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Gas turbine, 3, 4 ... Steam generator, 6 ... High pressure gas superheater, 7 ... Low pressure gas superheater, 10 ... Condenser, 20 ... Condensate connecting pipe, 21 ... Circulation pump, 22 ... Condenser Water temperature control valve, 23 ... Circulating water flow rate temperature control valve, 24 ... Cooling device, 2
5 ... Condensate temperature detector, 26 ... Condensate low flow rate detector, 27 ...
Circulating water temperature detector, 28 ... Connection pipe for water supply, 29 ... Circulating water pump, 30 ... Water supply temperature adjusting valve, 31 ... Circulating water temperature adjusting valve, 32 ... Cooling device, 33 ... Water supply temperature detector, 34 ...
Circulating water temperature detector, 35 ... Circulating water flow rate detector, 36 ... Circulating water return pipe, 37 ... Circulating water flow rate adjusting valve, 38 ... Circulating water flow rate detector, 39 ... Circulating water return pipe, 40 ... Circulating water flow rate adjustment A valve, 41 ... Condensate supply pipe, 42 ... Condensate discharge pipe, 43 ... Water supply pipe, 44 ... Water discharge pipe.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiro Kawauchi 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory

Claims (7)

[Claims] 1. A gas turbine, a steam generator for injecting fuel into exhaust gas from the gas turbine to reburn it, and a steam turbine driven by steam from the steam generator,
Condensate and feedwater that passes through a gas superheater in an exhaust gas recombustion combined cycle power plant that has a gas heater that circulates condensate and feedwater, respectively, and that heats condensate and feedwater by exhaust gas from a steam generator. When the flow rate of the exhaust gas decreases, the exhaust gas reheat type combined with the condensate water and the feed water that have passed through the gas superheater, and the recirculation circulation device that returns the condensate water and the supplied water to the corresponding gas superheater. Cycle power plant. 2. A gas turbine, a steam generator for injecting fuel into exhaust gas from the gas turbine to reburn the steam, and a steam turbine driven by steam from the steam generator.
Condensate and feedwater that have passed through a gas superheater in an exhaust gas re-combustion combined cycle power plant that has a gas heater that circulates condensate and feedwater, respectively, and that heats condensate and feedwater by exhaust gas from a steam generator. Having a reflux circulation device that takes in and recirculates the condensate water and the feed water that have been taken in to the corresponding gas superheater.
When the flow rate of feed water and condensate connecting the gas superheater between the inlet side and the outlet side and the flow rate of the feed water and condensate passing through the gas superheater decrease, the water supply and return from the gas superheater An exhaust gas re-combustion combined cycle power plant, comprising a reflux circulation mechanism that takes in water through the respective corresponding connecting pipes and returns it to the gas generator. 3. A gas turbine, a steam generator for injecting fuel into exhaust gas from the gas turbine to reburn the gas, and a steam turbine driven by steam from the steam generator.
Condensate and feedwater that have passed through a gas superheater in an exhaust gas re-combustion combined cycle power plant that has a gas heater that circulates condensate and feedwater, respectively, and that heats condensate and feedwater by exhaust gas from a steam generator. Has a reflux circulation device that recycles the condensate water and the feed water that have been taken in to the gas superheater, and the reflux circulation device includes a water supply connecting pipe and a condensate water that connect the inlet side and the outlet side of the gas superheater. When the flow rate of feed water and condensate passing through the connecting pipe and the gas superheater decreases, the feedwater and condensate from the gas superheater are taken in through the corresponding connecting pipes and returned to the gas generator. And a recirculation mechanism, wherein the recirculation mechanism has water supply and condensate water passing through respective connecting pipes, and temperature adjusting means for cooling and controlling the water supply and condensate water passing through each connecting pipe. Con India cycle power plant. 4. A gas turbine, a steam generator for injecting fuel into exhaust gas from the gas turbine to reburn it, and a steam turbine driven by steam from the steam generator,
Condensate and feedwater that have passed through a gas superheater in an exhaust gas re-combustion combined cycle power plant that has a gas heater that circulates condensate and feedwater, respectively, and that heats condensate and feedwater by exhaust gas from a steam generator. Has a reflux circulation device that recycles the condensate water and the feed water that have been taken in to the gas superheater, and the reflux circulation device includes a water supply connecting pipe and a condensate water that connect the inlet side and the outlet side of the gas superheater. When the flow rate of feed water and condensate passing through the connecting pipe and the gas superheater decreases, the feedwater and condensate from the gas superheater are taken in through the corresponding connecting pipes and returned to the gas generator. The reflux circulation mechanism comprises a temperature adjusting means for cooling and controlling the feed water and the condensate passing through the respective connecting pipes, and a point at which the flow rate of the condensate passing through the gas superheater further falls below a specified amount. so Repowering-shaft combined cycle power plant, characterized in that it comprises a flow rate adjusting means for adjusting the flow rate of the circulating water passing through the condensate for connecting pipe. 5. A gas turbine, a steam generator for injecting fuel into exhaust gas from the gas turbine to reburn the steam, and a steam turbine driven by steam from the steam generator,
Condensate and feedwater that have passed through a gas superheater in an exhaust gas re-combustion combined cycle power plant that has a gas heater that circulates condensate and feedwater, respectively, and that heats condensate and feedwater by exhaust gas from a steam generator. Has a recirculation circulation device that recycles the condensate water and the condensate water that have been captured to the gas superheater, and the recirculation circulation device guides the water supply and the condensate water that have passed through the gas superheater to the condenser, respectively. Pipe and condensate connecting pipe, circulating water return pipes that respectively guide the cooling water from the condenser to the inlet side of the gas superheater, and when the flow rate of feed water and condensate passing through the gas superheater decreases, The water supply and the condensate from the superheater are guided to the condenser via the respective corresponding connecting pipes to be cooled, and the cooling water from the condenser is superheated to the gas via the respective circulating water return pipes. Guide and contact each one Water and repowering-shaft combined cycle power plant, characterized in that it comprises a means for the same flow rate and cooling water through the condenser and circulating water return pipe through. 6. A gas turbine, a steam generator for injecting fuel into exhaust gas from the gas turbine to reburn the gas, and a steam turbine driven by steam from the steam generator,
Condensate and feedwater that have passed through a gas superheater in an exhaust gas re-combustion combined cycle power plant that has a gas heater that circulates condensate and feedwater, respectively, and that heats condensate and feedwater by exhaust gas from a steam generator. Has a recirculation circulation device that recycles the condensate water and the condensate water that have been captured to the gas superheater, and the recirculation circulation device guides the water supply and the condensate water that have passed through the gas superheater to the condenser, respectively. Pipe and condensate connecting pipe, circulating water return pipes that respectively guide the cooling water from the condenser to the inlet side of the gas superheater, and when the flow rate of feed water and condensate passing through the gas superheater decreases, The water supply and the condensate from the superheater are guided to the condenser via the respective corresponding connecting pipes to be cooled, and the cooling water from the condenser is superheated to the gas via the respective circulating water return pipes. Guide and contact each one A means for making the feed water and condensate through the circulating water return pipe and the cooling water through the circulating water return pipe have the same flow rate, and at the time when the flow rate of the condensate water passing through the gas superheater further falls below the specified amount, the condensate connecting pipe An exhaust gas re-combustion combined cycle power plant, comprising: a flow rate adjusting means for adjusting a flow rate of circulating water passing through the exhaust gas. 7. A gas turbine, a steam generator for injecting fuel into exhaust gas from the gas turbine to recombust, and a steam turbine driven by steam from the steam generator,
A low-pressure gas superheater for circulating the condensate to superheat the condensate;
In an exhaust gas re-combustion combined cycle power plant having a high-pressure gas heater that circulates feed water to heat the feed water, and a deaerator water level adjustment valve that adjusts the water level of the deaerator on the downstream side of the condenser, The gas superheater has a recirculation circulation device that takes in condensate and recirculates the condensate that has been taken in to the gas superheater. The recirculation circulation device is a connecting pipe that guides the condensate from the low-pressure gas superheater to the condenser. And a circulating water return pipe whose one end is connected between the condenser and the deaerator water level adjusting valve and the other end is connected to the inlet side of the low pressure gas superheater, and the condensate that passes through the low pressure gas superheater. When the flow rate decreases, the condensate that has passed through the low-pressure gas superheater is guided to the condenser via a connecting pipe to cool it, and the cooling water from the condenser is forced to gas superheat through the circulating water return pipe. Exhaust reburning type converter characterized in that Command cycle power plant.