JPH1137401A - Method for operating exhaust heat recovery boiler and controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the output of a gas turbine from being lowered and a stopping exhaust heat recovery boiler from being broken owing to the backflow of hot air even when it is necessary to additionally start or forcedly cool the exhaust heat recovery boiler whose operation stops during the increase of load the boiler. SOLUTION: A plurality of exhaust heat recovery boilers 2 which have groups of heat transfer pipes for recovering the heat of exhaust gas exhausted from a gas turbine are arranged in parallel. When a stopping boiler 2 as well as an operating boiler 2 is additionally started or forcedly cooled, water supplied to the operating boiler 2 is temporarily heated by an economizer 15 and then the heated water is mixed again with water supplied to the inlet of the economizer 15 or an on/off valve of a steam line at the outlet of a steam drum 19 is controlled to open/close. Thus, the pressure of the drum 19 is raised higher than that during an ordinary operation to raise the gas temperature of outlet ducts 9 of the operating boiler 2 and a combined flow duct 10. Accordingly, the buoyancy of gas (chimney effect) due to the specific volume difference generated from the temperature difference between the atmospheric temperature of the top part of a chimney 11 and the gas temperature is increased, so that the pressure of the combined flow duct 10 is more negative than that of the ducts 9 in the vicinity of the duct 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating an exhaust heat recovery boiler and a control device therefor, and more particularly to a combined power generation system in which exhaust gas ducts at a plurality of exhaust heat recovery boiler outlets are joined to a merging duct. The present invention relates to an operation method of a waste heat recovery boiler applied to a plant and a control device thereof.

[0002]

2. Description of the Related Art In a power plant, various measures have been considered to respond to a rapidly changing power demand. For example, at present, when nuclear power generation is being used as a base load, intermediate load operation has become established even in large-scale boilers of thermal power plants, and operation accompanied by considerable load fluctuations has become routine. However, in this large boiler, a quick start is performed,
There is a limit in responding to a sudden load change, and a power plant that can respond more flexibly is desired.

In the case of a thermal power plant, even a state-of-the-art plant has a thermal efficiency of about 40%.
In view of the recent fuel situation, it is desired to obtain higher thermal efficiency. However, it is practically difficult to further improve the thermal efficiency of the present individual thermal power plants that basically have a single heat cycle, and a plant with higher thermal efficiency is demanded. A power generation method using a gas turbine has been put to practical use as one of the methods for achieving the demand. Gas turbines are used in fields where load fluctuations are particularly large because rapid startup and rapid load changes are possible. In the case of this gas turbine power plant, since a large amount of exhaust gas exiting the gas turbine is quite hot, an exhaust heat boiler (exhaust heat recovery boiler) having a heat transfer surface is installed in this gas flow, and thereby the heat is discharged. A high-efficiency combined cycle (combined cycle) plant for recovering and driving a steam turbine with the generated steam to further generate power has been proposed and put into practical use. With this high-efficiency combined cycle power plant, it is possible to realize a plant having a power generation end thermal efficiency of about 44%.

In addition, as shown in FIG. 11, in the case of a combined cycle power plant having a plurality of gas turbines and a plurality of exhaust heat recovery boilers into which the exhaust gas of each gas turbine is introduced as one unit, the combined power generation plant has a plurality of gas turbines according to the boiler load. Thus, the high thermal efficiency can be achieved while changing the number of operating gas turbines.

FIG. 9 shows an example of this combined cycle power plant. The configuration shown in FIG. 9 is a configuration commonly referred to as a multi-shaft plant, and includes a plurality of gas turbines 1 and the gas turbines 1.
And a steam turbine 3 driven by the steam discharged from each heat recovery steam generator 2. Among the steam discharged from each exhaust heat recovery boiler 2, the high-pressure steam HPS and the low-pressure steam LPS are respectively supplied to the high-pressure side and the low-pressure side of the steam turbine 3, and the generator 5 is driven by the steam turbine 3. You. The steam after working in the steam turbine 3 is condensed in the condenser 6 and is supplied again to the exhaust heat recovery boiler 2 by the condensate pump 7. A generator 5 coaxially provided by each gas turbine 1
Is driven.

The low-temperature exhaust gas discharged from each exhaust heat recovery boiler 2 is sent from the low-temperature duct 9 provided with each opening / closing damper 13 to one joining duct 10, and the combined exhaust gas is exhausted from the chimney 11 to the atmosphere. You.

FIG. 10 includes a large number of steam turbines 3 and gas turbines 1. One steam turbine 3 is disposed coaxially with one gas turbine 1, and exhaust gas from each gas turbine 1 is provided. This is a single-shaft type combined cycle power plant in which steam is generated by an exhaust heat recovery boiler 2 provided in each exhaust gas path by heat. The steam generated by each exhaust heat recovery boiler 2 is used to drive each steam turbine 3.

[0008] In the case shown in FIG.
The exhaust gas discharged from the air conditioner is connected to a merging duct 10 via a low-temperature duct 9 provided with an opening / closing damper 13, and is discharged from the chimney 11 to the atmosphere.

The exhaust gas duct 9 of each exhaust heat recovery boiler 2 of such a combined cycle power plant is connected via a merging duct 10.
It is connected to one chimney 11.

[0010]

As described above, FIG.
In the combined cycle power plant shown in FIG. 10, a required number of boilers to be operated can be selected from a plurality of exhaust heat recovery boilers 2 arranged in parallel according to the boiler load.
At this time, when additionally starting or forcibly cooling the suspended heat recovery boiler 2 during operation, the exhaust gas duct connected to the exit of the suspended waste heat recovery boiler 2 before starting the gas turbine 1 during operation is stopped. It is necessary to open the damper 13 in 9. At this time, several hundred degrees of gas stagnating in the stopped exhaust heat recovery boiler 2 and the gas turbine 1 (in this combined cycle power plant, DSS, WSS (day and night start-up) (Halt, weekend start-up), and hot banking is performed, so that the temperature of the gas remaining in the exhaust heat recovery boiler 2 and the gas turbine 1 during stoppage is several hundred degrees. ), The exhaust gas from the exhaust heat recovery boiler 2 during operation is stopped via the merging duct 10 in order to prevent the air intake device and the like of the gas turbine 1 from burning. It is necessary to prevent backflow to 1.

In addition, the fact that the pressure in the merging duct 10 is higher than the pressure in the exhaust gas duct 9 at the exit of the exhaust heat recovery boiler 2 during the operation is stopped, especially when the plurality of exhaust heat recovery boilers 2
This can occur when operating a combined cycle power plant including. Also in this case, when the damper 13 in the exhaust gas duct 9 at the exit of the exhaust heat recovery boiler 2 during operation is opened, the hot air from the exhaust gas duct 9 at the exit of the exhaust heat recovery boiler 2 during operation flows through the merging duct 10. There is a possibility that the gas will flow back into the exhaust heat recovery boiler 2 that is stopped.

One of the measures against this problem is to design the merging duct 10 so that it always has a lower pressure than the surrounding exhaust gas duct 9. For this purpose, a large duct having a low pressure loss structure is used. It needs to be adopted. But,
In order to connect the merging duct 10 composed of a large duct structure to the chimney 11, it is necessary to provide a large duct connection opening at the base of the chimney 11, which causes a new problem of insufficient strength of the chimney.

Further, by utilizing the density difference between the gas in the chimney 11 and the surrounding atmosphere, which is one of the original functions of the chimney 11, the wind power (pressure difference) is increased, and the pressure in the junction duct 10 is reduced. It is also possible to make a negative pressure state from inside the duct 9 around it.

However, the passing wind (pressure difference) ΔP is expressed by the formula ΔP = (ρ ₀ −ρ) gH ρ ₀ : density of atmosphere, ρ: gas density in chimney 11, g: gravitational acceleration, H: chimney Since the height of the chimney 11 is proportional to the height H of the chimney 11 as represented by the height of the chimney 11, the height H of the chimney 11 may be increased more than necessary, ignoring construction costs and environmental regulations. It cannot be increased, and the wind power ΔP cannot be increased without limit by the height H of the chimney 11.

In addition, an induction draft fan is installed in the vicinity of the merging duct 10 so that the inside of the merging duct 10 is surrounded by the surrounding duct 9.
Although a negative pressure can be applied from the inside, installation of the induced draft fan in the merging duct 10 increases equipment costs and maintenance costs.

Further, instead of providing the merging duct 10, the flue gas duct 9 from each exhaust heat recovery boiler 2 is directly connected to the base of the chimney 11, and the merging portion of each flue gas duct 9 is provided in the base of the chimney 11. It is also possible to provide.

However, also in this case, since it is necessary to provide a plurality of openings for connecting the exhaust gas duct 9 at the base of the chimney 11,
Not only does the chimney 11 have insufficient strength, but it also becomes necessary to increase the length of each exhaust gas duct 9 to connect it to the chimney 11.

Since the above measures are not enough,
The most economical method is to reduce the pressure of the merging duct 10 from that of the surrounding exhaust gas duct 9 only before opening the damper 13 provided in the exhaust gas duct 9 of the exhaust heat recovery boiler 2 during shutdown. is there.

During the shutdown of the combined cycle power plant as shown in FIG. 9 or FIG. 10, only before the damper 13 of the exhaust heat recovery boiler 2 outlet duct 9 is opened, the merging duct 10 is subjected to a negative pressure from the surrounding exhaust gas duct 9. A conventional method for controlling the temperature of feed water will be described with reference to FIG. FIG. 7 illustrates a conventional water supply control method using the most downstream stage portion of one waste heat recovery boiler 2.

Water supplied from a water supply pump 17 provided in a water supply line 16 for water supplied to a economizer 15 installed in each exhaust heat recovery boiler 2 is heated by the economizer 15, and the exhaust heat recovery boiler is used. The water is sent from a steam drum 19 or a water supply line 24 disposed outside a casing serving as an exhaust gas passage to a boiler water supply pump 20 for supplying water to another pressure stage.
In order to prevent the water in the exhaust gas from condensing on the economizer 15 during operation of the exhaust heat recovery boiler 2 and corrode it, the outer surface temperature of the economizer 15 is maintained at a dew condensation temperature or higher. In addition, a water supply line 24 is provided from the upstream side of an on-off valve 23 provided in an outlet water supply line 22 of the economizer 15, and the water supply line 24 is provided at an inlet of the economizer 15 from an intermediate stage of the boiler water supply pump 20. The water supply temperature control valve 2 is connected to a circulation line 26 for merging with the line 16.
7 are installed.

The water supply line 2 on the outlet side of the economizer 15
Numeral 2 is connected to a steam drum 19 via an on-off valve 23, and a mixed fluid of steam and water from an evaporator 28 is supplied to the steam drum 19.

A thermometer 30 is provided in the water supply line 16 on the inlet side of the economizer 15 after the junction with the circulation line 26,
In addition, an economizer inlet temperature controller 31 for controlling the opening and closing of the feedwater temperature control valve 27 is provided, and a signal is input to the controller 31 from a thermosetting device 32 for setting the dew condensation prevention temperature of the economizer 15. You. Thus, the economizer 15
The economizer inlet temperature controller 31 adjusts the opening of the feedwater temperature control valve 27 in accordance with the deviation between the actually measured feedwater temperature from the thermometer 30 provided on the feedwater line 16 on the inlet side of the water heater and the set feedwater temperature from the temperature setter. The temperature of the feedwater supplied to the economizer 15 is controlled by controlling the feedwater circulation amount from the circulation line 26.

In the combined cycle power plant having the above-described configuration, in the related art, when the waste heat recovery boiler 2 that is stopped is additionally started, a part related to the operation can (the waste heat recovery boiler 2 during operation) shown in FIG. By reducing the output of the gas turbine 1 during operation and reducing the amount of exhaust gas as shown by the graph shown by the dotted line, the pressure of the merging duct 10 shown in FIG. In addition, the exhaust gas from the exhaust heat recovery boiler 2 during operation is prevented from flowing back to the stopped exhaust heat recovery boiler 2 and the gas turbine 1.

Here, when reducing the output of the gas turbine 1 during operation, it is necessary to reduce the amount of water supply circulation to the economizer 15 in the exhaust heat recovery boiler 2 downstream of the gas turbine 1. At this time, the damper 13 for opening and closing the exhaust gas duct 9 at the exit of the stopped exhaust heat recovery boiler 2 is connected to the merging duct 1
After the pressure in the gas turbine 1 becomes negative pressure than the pressure in the exhaust gas duct 9 in the peripheral portion, the gas turbine 1 is opened and the stopped gas turbine 1 is set to 1
Increase the output toward 00% output.

In a combined cycle power plant comprising a plurality of waste heat recovery boiler systems, it is necessary to additionally start the stopped waste heat recovery boiler 2 when the power demand increases and the amount of power generation needs to be increased. According to the conventional method for controlling the feedwater temperature in which the merging duct 10 shown in FIG. 7 is set to a negative pressure from the surrounding exhaust gas duct 9 in a situation where the amount of power generation needs to be increased, There is a problem that it is necessary to reduce the output, and it is not possible to immediately increase the output according to the demand of the power generation amount.

Therefore, an object of the present invention is to prevent the efficiency of a combined cycle power plant including a plurality of exhaust heat recovery boilers from being reduced during additional startup or forced cooling of the exhaust heat recovery boiler during shutdown. It is to be.

Another object of the present invention is to prevent the efficiency of a combined cycle power plant from being reduced due to a load drop of a gas turbine at the time of additional start-up or forced cooling of an exhaust heat recovery boiler during operation stoppage, and a complicated structure. An object of the present invention is to provide an exhaust heat recovery boiler that requires no driving operation and is easy to control.

Still another object of the present invention is to provide an exhaust heat recovery boiler whose operation is stopped when the load is increased, even when it is necessary to additionally start up or forcibly cool the exhaust heat recovery boiler, without reducing the output of the gas turbine and stopping the exhaust heat recovery. An object of the present invention is to provide an exhaust heat recovery boiler that does not damage the recovery boiler.

[0029]

The above object of the present invention is attained by the following constitution. That is, a heat transfer tube group (e.g., a economizer, an evaporator, and a superheater) for recovering heat of exhaust gas discharged from the gas turbine, a water supply system for supplying water to the heat transfer tube group, and recovering heat of the exhaust gas. A plurality of heat recovery steam generators having a steam system having a gas-liquid separation drum for supplying the generated steam to the demand side are arranged in parallel, and the exhaust gas ducts at the outlets of the respective heat recovery steam generators are merged into a merging duct. In the exhaust heat recovery boiler device connected to the chimney, in addition to the operating exhaust heat recovery boiler, the additional operation of the suspended exhaust heat recovery boiler or the forced exhaust cooling of the operating exhaust heat recovery boiler This is an operation method of the exhaust heat recovery boiler device in which the outlet gas temperature of at least one of the exhaust heat recovery boilers is increased from that in the normal operation.

In order to raise the outlet gas temperature of the exhaust heat recovery boiler from normal operation, there are the following methods. In a water supply system for supplying water to the heat transfer tube group, the water supplied to the heat transfer tube group is heated by a heat transfer tube group (for example, a economizer). A method of raising the feedwater temperature at the inlet of the heat transfer tube group (e.g., a economizer) by mixing the outlet feedwater again with the inlet water supply of the heat transfer tube group (e.g., a economizer). In the above-mentioned water supply system, a method of raising the exhaust gas heat recovery boiler outlet gas temperature by heating a heat transfer tube group inlet water supply temperature by a heater. In the exhaust heat recovery boiler in operation, the pressure in at least one gas-liquid separation drum of at least one exhaust heat recovery boiler is further increased from the normal operation state, so that the outlet gas temperature of the exhaust heat recovery boiler is increased. Method. A method combining the above methods.

In this way, when additionally starting or forcibly cooling the waste heat recovery boiler during operation stop, first, the temperature of the feed water at the inlet of at least one heat transfer tube group of the operating waste heat recovery boiler is raised, and After raising the outlet gas temperature of the exhaust heat recovery boiler during normal operation and setting the pressure in the merging duct to a negative pressure from the pressure in the exhaust gas duct around it, the By opening the damper provided in the exhaust gas duct and activating the gas turbine of the stopped exhaust heat recovery boiler, the high-temperature gas from the operating exhaust heat recovery boiler to the stopped exhaust heat recovery boiler joins the duct. It can be prevented from flowing backward through the.

Here, the above-mentioned "during normal operation" or "normal operation state" refers to a state or a state in which the stopped heat recovery steam generator starts operation and is operating in a stable state. An apparatus for actually implementing the above-described method is shown in FIGS.

Further, in the present invention, it is not necessary to join all the exhaust gas ducts at the outlet of each exhaust heat recovery boiler to the merging duct, and it is not necessary to connect the merging duct to only one chimney.

[0034]

According to the present invention, when the exhaust gas temperature in the exhaust gas duct at the outlet of the exhaust heat recovery boiler during operation rises more than during normal operation, that is, when the gas temperature in the junction duct rises more than during normal operation, The specific volume difference buoyancy (chimney effect) generated from the temperature difference between the atmospheric temperature and the gas temperature at the top of the chimney on the downstream side of the duct increases, and the pressure of the confluence duct is set to a negative pressure from the pressure in the exhaust gas duct near the surrounding area. Can be held. In addition, it is possible to prevent the exhaust gas from the exhaust heat recovery boiler that is operating from flowing back to the stopped exhaust heat recovery boiler.

[0035]

Embodiments of the present invention will be described below. FIG. 1 shows a feedwater control system diagram representing a part of one exhaust heat recovery boiler system in the combined cycle power plant shown in FIG. 9 or FIG.

Water supplied from a water supply pump 16 provided in a water supply passage supplied to each exhaust heat recovery boiler 2 is heated by a economizer 15 and disposed outside a flue constituting the exhaust heat recovery boiler 2. The steam is supplied from a steam drum 19 or a water supply line 24 to a boiler water supply pump 20 for supplying water to another pressure stage.
In order to prevent the water in the exhaust gas from condensing on the economizer 15 during operation of the exhaust heat recovery boiler 2 and corrode it, the outer surface temperature of the economizer 15 is maintained at a dew condensation temperature or higher. In addition, a water supply line 24 is provided from the upstream side of an on-off valve 23 provided in an outlet water supply line 22 of the economizer 15, and the water supply line 24 circulates to join a water supply line 16 at the inlet of the economizer 15. The circulation line 26 is connected to a feed water temperature control valve 27. In addition, economizer 1
The outlet water supply line 22 of 5 is connected to a steam drum 19 via an on-off valve 23, and a mixed fluid of steam and water from an evaporator 28 is supplied to the steam drum 19.

The merging duct 10 is provided with a pressure detector 40 for detecting the pressure of the merging duct 10. The pressure signal output from the pressure detector 40 is input to the pressure-temperature converter 41.

Further, a thermometer 30 is provided downstream of the junction of the water supply line 16 to the economizer 15 with the circulation line 26,
Further, an economizer inlet temperature controller 31 for controlling the opening and closing of the feedwater temperature control valve 27 is provided. The economizer inlet temperature controller 31 has an actually measured feedwater temperature from the thermometer 30 and a preset condensation of the economizer 15. The set temperature from the temperature setting device 32 for setting the prevention set temperature and the input from the pressure temperature converter 41 are made.

In this manner, the pressure signal of the part of the merging duct 10 obtained by the pressure detector 40 is converted into a corresponding temperature by the pressure-temperature converter 41, and then input to the economizer inlet temperature controller 31. The measured water supply temperature from the thermometer 30 provided in the water supply line 16 and the dew-prevention set temperature from the temperature setting device 32 (condensation occurs when the water supply temperature is 50 to 60 ° C.) are added, and the water is supplied to the inlet of the economizer. The temperature controller 31 controls the opening of the feedwater temperature control valve 27 and controls the amount of the economizer feedwater circulation from the circulation line 26.

Therefore, when the exhaust heat recovery boiler 2 during operation is additionally started or when forced cooling is performed, the amount of circulation of the water-saving unit water supply can be increased, and the temperature of the water-supply unit inlet water supply temperature is raised from that in the normal operation. As a result, the gas temperature at the exhaust heat recovery boiler outlet, that is, the gas temperature of the junction duct 10 is raised.

FIGS. 5 and 6 show the results of controlling the amount of water conveyed by the economizer when the exhaust heat recovery boiler 2 is started from the normal operation and stopped during the operation shown in FIG. FIG. 5 shows a relationship between the flow rate of the water-saving circulation of the economizer and the gas temperature in the junction duct, and FIG. 6 shows a relationship between the temperature in the junction duct and the pressure in the junction duct. As shown by point A in FIG. 6, the gas temperature in the merging duct during normal operation is 96 ° C. and the pressure in the merging duct is a positive pressure of 3 mmAq. As shown by B, the gas temperature in the merging duct is about 10 ° C.
By raising the pressure, the pressure in the merging duct becomes 4mmAq
The pressure is reduced to a degree, and a negative pressure of -1 mmAq can be maintained.

FIG. 8 is a solid line showing a time chart when the exhaust heat recovery boiler 2 which is in operation is additionally started when the exhaust heat recovery boiler 2 in operation is present. At the time of additional startup of the stopped heat recovery steam generator, first, the output of the operating gas turbine 1 becomes 1
While maintaining the pressure at 00%, the amount of circulation of the water-saving device of the exhaust heat recovery boiler 2 during operation is increased, and the temperature of the exhaust heat recovery boiler outlet gas (the temperature of the gas in the junction duct) is increased. The pressure in the surrounding exhaust gas duct 9 is set to a negative pressure. Next, the exhaust heat recovery boiler outlet exhaust gas duct 9 that is stopped
Is opened, and the stopped gas turbine 1 is started. As a result, the pressure of the merging duct 10 is reduced to a negative pressure without reducing the output of the operating gas turbine 1 in order to reduce the amount of exhaust gas of the operating gas turbine 1 as in the prior art shown by the dotted line in FIG. Can be held.

The present invention also relates to a merging duct 10 shown in FIG.
Not only the control by the pressure signal of the pressure detector 40 described above, but also the control by the detection signal of the gas temperature in the number of operating gas turbines, the exhaust heat recovery boiler outlet and / or the gas temperature in the merging duct.

FIG. 1 shows the evaporator 28 and the economizer 15 installed at the most downstream of the gas flow, but the evaporator or the economizer having a plurality of pressure stages installed upstream of the gas. The pressure in the junction duct may be controlled to be lower than the pressure in the surrounding exhaust gas duct by controlling the temperature of feed water or steam supplied to any one or a plurality of heat exchangers.

FIG. 2 shows another embodiment of the present invention.
FIG. 2 also shows a water supply control system diagram as a representative of the most downstream portion of one exhaust heat recovery boiler system in the combined cycle power plant shown in FIG. 9 or FIG. 10, similarly to the example of FIG. is there.

Water supplied from a water supply pump 17 provided in a water supply line 16 supplied to the exhaust heat recovery boiler 2 is supplied to the economizer 1.
5, a water supply line 2 from the outlet of the steam drum 19 or the economizer 15 disposed outside the casing of the exhaust heat recovery boiler 2 to the steam drum 19.
2 is provided with a water supply line 24 branching from the upstream side of the on-off valve 23 provided with the water supply pump 20 for supplying water to another pressure stage from the water supply line 24.

The outlet water supply line 22 of the economizer 15 is connected to a steam drum 19 via an on-off valve 23.
The steam drum 19 is supplied with a mixed fluid of steam and water from an evaporator 28. In the example shown in FIG. 2, a circulation line 26 connected from the water supply line 24 to the water supply line 16 at the inlet of the economizer 15 in FIG. 1 and a water supply temperature control valve 27 provided in the line 26 are not installed. Instead, a pressure control valve 44 is provided in the steam line 43 at the outlet of the steam drum 19, and the pressure control valve 44
Since a signal from a steam drum pressure detector 46 and a pressure setting device 47 for setting the drum pressure in a normal operation state is input to the control steam drum pressure controller 45, the opening and closing control of the control valve 44 is performed. Controls the pressure in the steam drum 19. The merging duct 10 is provided with a pressure detector 40 for detecting the pressure of the merging duct portion. A pressure signal output from the pressure detector 40 is input to a steam drum pressure controller 45.

In this way, the steam pressure in the steam drum 19 is controlled by the drum pressure controller 45 according to the signal of the pressure detector 40 in the junction duct 10. Steam drum 16
By increasing the pressure in the evaporator 28, the temperature of the saturated water and steam in the evaporator 28 increases, and as a result, the temperature of the gas passing through the evaporator 28 increases. Therefore, the gas temperature at the exhaust heat recovery boiler outlet, that is, the gas temperature in the merging duct 10 is higher than that during normal operation, so that the same effect as the example shown in FIG. 1 is obtained. The pressure in the junction duct 10 can be maintained at a negative pressure without lowering the gas turbine output in order to reduce the amount of exhaust gas.

The present invention also relates to a merging duct 10 shown in FIG.
Not only the control by the pressure signal of the pressure detector 40 described above, but also the control by the signal such as the number of operating gas turbines, the gas temperature in the exhaust heat recovery boiler outlet and / or the junction duct, etc. can be applied.

FIG. 2 shows a steam drum 19 connected to an evaporator 28 and a economizer 15 installed at the most downstream of the gas flow.
In addition, the pressure in the merging duct is controlled by controlling the pressure of a steam drum connected to any one of a plurality of evaporators or a plurality of heat exchangers or a plurality of heat exchangers installed at an upstream side of the exhaust heat recovery boiler 2. Control to make negative pressure may be performed.

The control valve 44 for controlling the pressure of the steam drum 19 is provided not only at the steam drum outlet but also at the steam turbine inlet and the superheater (not shown) outlet.
In the case of an exhaust heat recovery boiler 2 having a plurality of pressure stages, the pressure control can be applied to all or some of the pressure stages. It is also possible to apply

Also, as shown in FIG. 3, FIG.
Alternatively, a configuration using the embodiment shown in FIG. In addition,
FIG. 3 also shows the water supply control on behalf of the heat transfer can group at the lowest stage of one exhaust heat recovery boiler system in the combined cycle power plant shown in FIG. 9 or FIG. It shows a system diagram.

That is, in the exhaust heat recovery boiler water supply control system diagram of FIG. 3, the economizer 15, the water supply line 16, the water supply pump 1
7, steam drum 19, on-off valve 23, water supply line 24, circulation line 26, water supply temperature control valve 27, evaporator 28, thermometer 30, economizer inlet water supply temperature controller 31, temperature setting device 32, pressure temperature converter 41, pressure control valve 44, steam drum pressure controller 45, steam drum pressure detector 4
6 and a pressure setting device 47 are provided.

In the example shown in FIG. 3, the pressure in the merging duct 10 is detected by the pressure detector 40, and the detected pressure signal is input to the pressure-temperature converter 41 and the steam drum pressure controller 45. As a result, the economizer inlet feedwater temperature controller 31 controls the opening degree of the ecosystem feedwater temperature control valve 27, controls (increases) the economizer feedwater circulation amount from the circulation line 26, and raises the economizer inlet feedwater temperature. As a result, the gas temperature at the exhaust heat recovery boiler outlet, that is, the gas temperature of the junction duct 10 is raised. At the same time, the steam pressure in the steam drum 19 is controlled by the drum pressure controller 45 based on the output signal of the pressure detector 40 to increase the steam drum pressure, so that the saturated water and steam in the evaporator 28 are increased. By raising the temperature, the temperature of the gas passing through the evaporator 28 is raised.

As described above, the rise in the feedwater temperature of the economizer 15 and the rise in the temperature of the saturated water and steam in the evaporator 28 increase the temperature of the exhaust heat recovery boiler outlet gas, that is, the merging duct 1.
By raising the gas temperature in 0 from the time of normal operation, the gas temperature in the junction duct 10 can be made to be a negative pressure more than the pressure in the exhaust gas duct 9 in the peripheral part.

The present invention also relates to a merging duct 10 shown in FIG.
Not only the control by the pressure signal of the pressure detector 40 described above, but also the control by the signal such as the number of operating gas turbines, the gas temperature in the exhaust heat recovery boiler outlet and / or the junction duct, etc. can be applied.

In addition to the evaporator 28 and the economizer 15 installed at the most downstream of the gas flow shown in FIG. 3 and the steam drum 19 connected to the evaporator 28, the evaporator 28 is installed upstream of the exhaust heat recovery boiler 2. Negative pressure in the merging duct is achieved by controlling the feedwater temperature or steam temperature of any of the evaporators or economizers with multiple pressure stages or multiple heat transfer tube groups or the pressure of the steam drum connected to these heat transfer tube groups Control may be performed.

Further, as shown in FIG. 4, a feed water heater 48 is installed in the economizer feed water line 16, and the output signal of the pressure detector 40 in the junction duct 10 is sent to the heating temperature controller 49 of the feed water heater 48. An input configuration may be adopted. FIG. 4 shows, in addition to the heater 48 for feed water heating, the economizer 1
A feed water thermometer 30 provided in a feed line 16 to the 5 inlets,
Merging duct pressure detector 40 provided in merging duct 10
A pressure-temperature converter 41 for calculating a temperature corresponding to the pressure in the merging duct 10 detected by the pressure detector 40 based on a preset pressure-temperature relational expression; The economizer that controls the temperature of the water supply in the water supply line 16 by the heater 48 based on the temperature corresponding to the pressure in the merging duct 10 calculated by the above and the water supply temperature at the inlet of the heat transfer tube group detected by the water supply temperature measuring device 32. An inlet water temperature controller 31 is provided.

[0059]

According to the present invention, in a combined cycle (combined cycle) plant in which a plurality of canned heat recovery boilers are connected to one chimney, the merging duct is controlled by controlling the gas temperature at the exhaust heat recovery boiler outlet. The internal pressure can be maintained at a lower pressure than the pressure in the exhaust gas duct around it, and the additional shutdown of the gas turbine and the exhaust heat recovery boiler that are safely stopped without lowering the output of the gas turbine can be performed. it can. In addition, since the merging duct can be easily maintained at a negative pressure, the height of the chimney, which was conventionally required about 200 m, can be reduced to about 120 m, and the cross-sectional area of the merging duct can be further reduced. There is an advantage that equipment costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pressure control device in a merging duct of an exhaust heat recovery boiler according to the present invention.

FIG. 2 is a diagram showing a pressure control device in a merging duct of the exhaust heat recovery boiler according to the present invention.

FIG. 3 is a diagram showing a pressure control device in a merging duct of the exhaust heat recovery boiler according to the present invention.

FIG. 4 is a view showing a pressure control device in a merging duct of the exhaust heat recovery boiler according to the present invention.

FIG. 5 is a diagram illustrating a result obtained by the control device of FIG. 1;

FIG. 6 is a diagram illustrating a result obtained by the control device of FIG. 1;

FIG. 7 is a diagram showing a pressure control device in a merging duct of a conventional heat recovery steam generator.

FIG. 8 is a diagram for comparing and explaining results obtained by the control device of FIG. 1 and a control device of the related art.

FIG. 9 is a schematic configuration diagram of a multi-shaft combined cycle plant.

FIG. 10 is a schematic configuration diagram of a single-shaft combined cycle plant.

FIG. 11 is a diagram illustrating a relationship between a boiler load and a thermal efficiency of a combined cycle plant in which a plurality of gas turbines and an exhaust heat recovery boiler are arranged in parallel.

[Explanation of symbols]

2 Exhaust heat recovery boiler 9 Exhaust gas duct 10 Merging duct 11 Chimney 13 Damper 15 Energy saving device 16 Water supply line 17 Water supply pump 19 Steam drum 20 Boiler water supply pump 22 Outlet water supply line 23 Open / close valve 24 Water supply line 28 Evaporator 30 Thermometer 31 Section Coal appliance inlet feed water temperature controller 32 Temperature setter 40 Pressure detector 41 Pressure temperature converter 48 Feed water heater 49 Heating temperature controller

Claims (16)

[Claims] 1. A heat transfer tube group for recovering heat of exhaust gas discharged from a gas turbine, a water supply system for supplying water to the heat transfer tube group, and a steam generated by recovering heat of the exhaust gas on a demand side. Heat recovery boiler with a plurality of exhaust heat recovery boilers equipped with a steam system having a gas-liquid separation drum for supplying to the stack, and an exhaust gas duct at each exhaust heat recovery boiler outlet joined to a merging duct and connected to a chimney In addition to the waste heat recovery boiler in operation, at the time of additionally starting or forcibly cooling the waste heat recovery boiler in operation, at least one of the waste heat recovery boilers in operation is operated. A method of operating the exhaust heat recovery boiler device, wherein the temperature of the outlet gas is increased from that in the normal operation. 2. In the water supply system, the supply water supplied to the heat transfer tube group is heated by the heat transfer tube group once, and the outlet supply water of the heat transfer tube group is mixed again with the heat transfer tube group inlet supply water to thereby provide the heat transfer tube group. The method for operating an exhaust heat recovery boiler device according to claim 1, wherein the temperature of the exhaust heat recovery boiler outlet gas is increased by increasing the feedwater temperature at the inlet of the heat transfer tube group from that during normal operation. 3. The exhaust gas heat recovery boiler outlet gas temperature is raised from that during normal operation by heating a heat transfer tube group inlet feed water temperature by a heater in the water supply system. Method of operating the waste heat recovery boiler device. 4. When additionally starting up or forcibly cooling a waste heat recovery boiler that has been shut down, first, the water supply temperature at the inlet of the heat transfer tube group of at least one waste heat recovery boiler of the operating waste heat recovery boiler is determined. After raising the temperature of the outlet gas of the exhaust heat recovery boiler during the operation from that in the normal operation, and setting the pressure in the merging duct to be lower than the pressure in the exhaust gas duct around it, the exhaust heat 2. The exhaust heat recovery boiler operating method according to claim 1, wherein a damper provided in the exhaust gas duct on the recovery boiler outlet side is opened to start the gas turbine of the stopped exhaust heat recovery boiler. 5. In addition to the waste heat recovery boiler in operation, at the time of additionally starting or forcibly cooling the waste heat recovery boiler in operation, at least one of the waste heat recovery boilers in operation is used.
The exhaust gas temperature at the exhaust heat recovery boiler outlet is raised from that in normal operation by increasing the pressure in at least one gas-liquid separation drum of the two exhaust heat recovery boilers from the pressure in a normal operation state. An operation method of the exhaust heat recovery boiler device according to 1. 6. When additionally starting up or forcibly cooling a waste heat recovery boiler that has been stopped, first, at least one gas-liquid of at least one waste heat recovery boiler among the operating waste heat recovery boilers. After increasing the pressure of the separation drum, increasing the outlet gas temperature of the exhaust heat recovery boiler during the operation from that during the normal operation, and setting the pressure in the merging duct to be a negative pressure from the pressure in the exhaust gas duct in the surrounding area, 6. The exhaust heat recovery boiler operating method according to claim 5, wherein a damper provided in the exhaust gas duct on the exit side of the exhaust heat recovery boiler that is stopped is opened to start the gas turbine. 7. When the exhaust heat recovery boiler during operation is additionally started or forcibly cooled, water supplied to the heat transfer tube group is heated by the heat transfer tube group in the water supply system, and Mixing the outlet feed water of the heat tube group with the inlet feed water of the heat transfer tube group again, and normalizing the pressure in at least one gas-liquid separation drum of at least one waste heat recovery boiler among the operating waste heat recovery boilers. 2. The operating method of an exhaust heat recovery boiler device according to claim 1, wherein the exhaust gas temperature at the exhaust heat recovery boiler outlet is further raised from that in the normal operation by further increasing the operating state. 8. When the exhaust heat recovery boiler during operation is additionally started up or forcibly cooled, first, the outlet gas temperature of at least one exhaust heat recovery boiler in one operating waste heat recovery boiler. After the normal operation, the pressure in the merging duct is set to a negative pressure than the pressure in the surrounding exhaust gas duct, and then the damper provided in the exhaust gas duct on the exit side of the exhaust heat recovery boiler that is stopped is opened. The method for operating an exhaust heat recovery boiler according to claim 7, wherein the gas turbine is started. 9. A heat transfer tube group for collecting heat of exhaust gas discharged from a gas turbine, a water supply system for supplying water to the heat transfer tube group, and a steam generated by collecting heat of the exhaust gas on a demand side. A plurality of exhaust heat recovery boilers equipped with a steam system for supplying heat to the exhaust heat recovery boilers are connected in parallel to the exhaust heat ducts at the outlets of the exhaust heat recovery boilers. In the water supply system to at least one heat transfer tube group of the boiler, a water supply line at the heat transfer tube group outlet,
A branch line that branches from the water supply line and connects to a water supply line to the heat transfer tube group inlet, an on-off valve for opening and closing the water supply line provided in the branch line, and a branch of the water supply line to the heat transfer tube group inlet A feedwater temperature measuring device provided in the water supply line downstream from the junction with the line, a merging duct pressure detector provided in the merging duct, and the merging duct pressure based on a preset pressure-temperature relational expression. A pressure-temperature converter for calculating a temperature corresponding to the pressure in the merging duct detected by the detector, and a temperature corresponding to the pressure in the merging duct calculated by the pressure-temperature converter and detected by the feedwater temperature measuring device An exhaust heat recovery boiler control device, further comprising a heat transfer tube group inlet temperature controller for controlling the opening and closing of an on-off valve provided in the branch line based on the heat transfer tube group inlet feed water temperature. 10. A detector for the number of operating gas turbines, an exhaust heat recovery boiler outlet, and / or a gas temperature in a merging duct, instead of or in addition to the merging duct pressure detector provided in the merging duct. The branch line is based on a preset relational expression between the detected value and the temperature, and based on the temperature corresponding to the detected value of these detectors and the heat transfer tube group inlet feed water temperature detected by the feed water temperature measuring device. 10. The exhaust heat recovery boiler control device according to claim 9, further comprising a heat transfer tube group inlet temperature controller for performing opening / closing control of the opening / closing valve provided in the apparatus. 11. A heat transfer tube group for collecting heat of exhaust gas discharged from a gas turbine, a water supply system for supplying water to the heat transfer tube group, and a steam generated by collecting heat of the exhaust gas on a demand side. Heat recovery boilers equipped with a steam system having a steam drum for gas-liquid separation to be supplied to a stack, and exhaust heat ducts at the outlet of each heat recovery boiler are merged with a merging duct and connected to a chimney In a recovery boiler device, a steam system for measuring pressure in at least one steam drum is provided in a steam system for recovering heat of exhaust gas of each exhaust heat recovery boiler and supplying steam generated to a demand side. A steam line provided at the outlet of the steam drum, an on-off valve for opening and closing the steam line provided on the steam line, a merging duct pressure detector provided on the merging duct, and detection by the merging duct pressure detector. I A steam drum pressure controller for controlling the opening and closing of an on-off valve provided in the steam line based on the pressure in the junction duct and the steam drum pressure detected by the steam drum pressure gauge is provided. Exhaust heat recovery boiler control unit. 12. A detector for the number of operating gas turbines, an exhaust heat recovery boiler outlet, and / or a gas temperature in the junction duct, instead of or in addition to the junction duct pressure detector provided in the junction duct. The steam based on the pressure corresponding to the detected values of these detectors and the steam drum pressure detected by the steam drum pressure measuring device based on a preset relational expression between the detected values and the pressure. The control device for an exhaust heat recovery boiler according to claim 11, further comprising a steam drum pressure controller for performing opening / closing control of an on-off valve provided on the line. 13. A heat transfer tube group for recovering heat of exhaust gas discharged from a gas turbine, a water supply system for supplying water to the heat transfer tube group, and a steam generated by recovering heat of the exhaust gas on a demand side. Heat recovery boilers equipped with a steam system having a steam drum for gas-liquid separation to be supplied to a stack, and exhaust heat ducts at the outlet of each heat recovery boiler are merged with a merging duct and connected to a chimney In the recovery boiler device, a water supply system to at least one heat transfer tube group of each exhaust heat recovery boiler includes a water supply line at an outlet of the heat transfer tube group, and a water supply line branched from the water supply line to an inlet of the heat transfer tube group. A branch line connected to the branch line, a water supply line opening / closing valve provided in the branch line, a water supply temperature measuring device provided in a water supply line to the heat transfer tube group inlet, and a merging duct pressure provided in a merging duct. Detector and A pressure-temperature converter that calculates a temperature corresponding to the pressure in the merging duct detected by the merging duct pressure detector based on the set pressure-temperature relational expression, and a merging calculated by the pressure-temperature converter. A heat transfer tube group inlet temperature controller for performing opening / closing control of an open / close valve provided in the branch line based on a temperature corresponding to the pressure in the duct and a heat transfer tube group inlet feed water temperature detected by the feed water temperature measuring device; A steam system for measuring the pressure in at least one steam drum; a steam system for measuring the pressure in at least one steam drum; A steam line provided at the drum outlet,
An on-off valve for opening and closing the steam line provided in the steam line, a merging duct pressure detector provided in the merging duct,
A steam drum pressure controller for controlling the opening and closing of an on-off valve provided in the steam line based on the pressure in the joining duct detected by the merging duct pressure sensor and the steam drum pressure detected by the steam drum pressure measuring device. A control device for an exhaust heat recovery boiler, comprising: 14. A detector for the number of operating gas turbines, an exhaust heat recovery boiler outlet, and / or a gas temperature in a merging duct, instead of or in addition to the merging duct pressure detector provided in the merging duct. The branch line is based on a preset relational expression between the detected value and the temperature, and based on the temperature corresponding to the detected value of these detectors and the heat transfer tube group inlet feed water temperature detected by the feed water temperature measuring device. A heat transfer tube group inlet temperature controller for controlling the opening and closing of the open / close valve provided in the gas turbine is further provided. Further, a gas turbine operating number, an exhaust heat recovery boiler outlet and / or a gas temperature detected by a detector of a merging duct, and Based on the set relational expression between the detected value and the pressure, the pressure corresponding to the detected value of these detectors and the steam drum detected by the pressure measuring device in the steam drum are used. 14. The control device for an exhaust heat recovery boiler according to claim 13, further comprising a steam drum pressure controller for controlling the opening and closing of an on-off valve provided in the steam line based on the pressure in the steam. 15. A heat transfer tube group for collecting heat of exhaust gas discharged from a gas turbine, a water supply system for supplying water to the heat transfer tube group, and a steam generated by collecting heat of the exhaust gas on a demand side. A plurality of exhaust heat recovery boilers equipped with a steam system to be supplied to the exhaust heat recovery boiler unit connected in parallel with the exhaust gas duct at the outlet of each exhaust heat recovery boiler, and connected to the stack In a water supply system to the heat transfer tube group of the boiler, a heater for heating water supply arranged in a water supply line to at least one heat transfer tube group inlet, and a water supply temperature measuring device provided in a water supply line to the heat transfer tube group inlet And a merging duct pressure detector provided in the merging duct, and calculating a temperature corresponding to the pressure in the merging duct detected by the merging duct pressure detector based on a preset pressure-temperature relational expression. Pressure temperature conversion And controlling the feedwater temperature in the feedwater line by the heater based on the temperature corresponding to the pressure in the merging duct calculated by the pressure / temperature converter and the feedwater temperature at the inlet of the heat transfer tube group detected by the feedwater temperature measuring device. A control device for an exhaust heat recovery boiler, comprising a heat transfer tube group inlet temperature controller. 16. The number of operating gas turbines, the exhaust heat recovery boiler outlet and / or the inside of the merging duct, instead of the merging duct pressure detector provided in the merging duct or in addition to the merging duct pressure detector provided in the merging duct. A gas temperature detector is provided, and based on a preset relational expression between the detected value and the temperature, the temperature corresponding to the detected value of these detectors and the water supply temperature at the inlet of the heat transfer tube group detected by the water supply temperature measuring device are determined. The control apparatus for an exhaust heat recovery boiler according to claim 15, further comprising a heat transfer tube group inlet temperature controller for controlling a feed water temperature in a feed water line by the heater.