JPH06294305A - Exhaust heat recovery boiler - Google Patents

Abstract

PURPOSE:To prevent generation of over heat stress on a reheater pipe side at the time of starting, in an exhaust heat recovery boiler provided with a reheater. CONSTITUTION:In an exhaust heat recovery boiler provided with a reheater, which is provided with a baffle plate 31 in order to allow no gas turbine exhaust gas to bypass the thermal transferring surface of an exhaust heat recovery boiler, the amount of fuel supplied into a gas turbine 2 is controlled in response to condition of a temperature distribution on the pipe wall surface of a reheater pipe side 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust heat recovery boiler with a reheater that produces steam by the exhaust gas from a gas turbine.

[0002]

2. Description of the Related Art In an exhaust heat recovery type combined power generation plant, as the gas temperature at the gas turbine inlet has recently become higher,
The exhaust gas temperature of the gas turbine also rises to around 600 ° C., and a reheat triple pressure steam cycle is being adopted to improve plant efficiency.

FIG. 5 shows an example of the construction of the reheat 3 pressure type exhaust heat recovery type combined cycle power generation plant. In the figure, reference numeral 1 is an air compressor. The air compressed by the air compressor 1 is supplied to a combustor 2, and the gas that has become high pressure and high temperature due to combustion of the fuel supplied to the combustor 2 It is introduced into the gas turbine 3. And the gas turbine 3
The high-temperature exhaust gas that has performed the work is introduced into the exhaust heat recovery boiler 4.

In the exhaust heat recovery boiler 4, the high-pressure second superheater 5, the reheater 6, the high-pressure first superheater 7, the high-pressure evaporator 8, and the intermediate-pressure superheater 9 are sequentially installed from the side where the high-temperature exhaust gas is introduced. , Low-pressure superheater 10, high-pressure second economizer 11, medium-pressure evaporator 12, medium-pressure economizer 13, high-pressure first economizer 14, low-pressure evaporator 12, medium-pressure economizer 13, high-pressure first A economizer 14, a low-pressure evaporator 15, and a low-pressure economizer 16 are provided, and the high-temperature exhaust gas introduced into the exhaust heat recovery boiler 4 is sequentially heat-exchanged with a heat exchanger such as the superheater. After that, it is released into the atmosphere from a chimney (not shown).

On the other hand, the condensate condensed in the condenser 17 is returned to the low pressure economizer 1 of the exhaust heat recovery boiler 4 by the condensate pump 18.
6 is supplied. The feed water supplied to the low-pressure economizer 16 is heated by heat exchange with the exhaust gas, and then a part of the water is supplied to the high-pressure feed pump 19, the high-pressure first economizer 14, the high-pressure second economizer 11, and the high-pressure evaporator. 8, the high-pressure first superheater 7 and the high-pressure second superheater 5 are sequentially heated to form high-temperature high-pressure superheated steam, which is supplied to the high-pressure steam turbine 20. Then, the steam that has worked in the high-pressure steam turbine 20 is introduced into the reheater 6.

Further, another part of the feed water heated by the low pressure economizer 16 is supplied to the intermediate pressure evaporator 12 via the intermediate pressure economizer 13 by the intermediate pressure feed pump 21, and the steam generated there is also generated. It is introduced into the reheater 6 through the medium pressure superheater 9.
Then, the steam reheated by the reheater 6 is introduced into the intermediate pressure steam turbine 22, and the steam that has worked in the hollow steam turbine 22 is supplied to the low pressure steam turbine 23.

A part of the feed water supplied to the low pressure economizer 16 and heated there by exchanging heat with the exhaust gas flows into the low pressure drum 24 of the low pressure evaporator 15 and is heated in the low pressure evaporator 15. , The steam generated there is low-pressure drum 2
4 and the low-pressure heater 10, and then supplied to the low-pressure steam turbine 23 together with the steam from the intermediate-pressure steam turbine 22.

The steam supplied to the low-pressure steam turbine 23 performs work there, and the high-pressure steam turbine 2
The exhaust gas, which rotates the generator 25 together with the zero and medium pressure steam turbines 22 and performs work in the low pressure steam turbine 23, flows into the condenser 17 and is condensed therein.

[0009]

By the way, when the steam turbine is started until the high-pressure main steam is introduced into the steam turbine, the steam generated in the low-pressure evaporator 15 passes through the low-pressure drum 24 and the low-pressure superheater 10. , Is returned to the condenser 17 through the low pressure bypass line 26. Further, the feed water, which has been pressurized by the medium pressure water supply pump 21 and then supplied to the medium pressure drum 27 of the medium pressure evaporator 12 through the medium pressure economizer 13, is heated in the medium pressure evaporator 12 to be vaporized there. The generated steam returns to the intermediate-pressure drum 27, then passes through the high-pressure first superheater 7, the high-pressure second superheater 5, and further returns to the condenser 17 through the high-pressure bypass line 30.

However, when the steam turbine is started, no steam flows in the reheater. For this reason, in the reheater 6, heat transfer outside the tube is dominant.

By the way, the reheater 6 is composed of an upper pipe drawer, a lower pipe drawer, and a heat transfer pipe panel, and the gas turbine exhaust gas is provided on the heat transfer surface of the exhaust heat recovery boiler at the outer peripheral portion of each heat exchanger. Since the baffle plate 31 is provided in the gas flow region so as not to bypass, in the upper header, there is a temperature difference between the lower surface that directly contacts the exhaust gas and the upper surface where the temperature rises due to heat conduction from the lower surface, causing a downward convex. Try to transform into. Further, in the lower pipe draw, when the exhaust gas is directly contacted, a temperature difference occurs between the upper surface and the lower surface where the temperature rises due to heat conduction from the upper surface, and the upper surface tends to deform upward.

On the other hand, in the heat transfer tube group which constitutes the heat transfer tube, there is almost no difference in thermal expansion in the same heat transfer tube panel, so that the deformation of the upper tube draw and the lower tube draw is restrained by the heat transfer tube group. Therefore, if the exhaust gas temperature rises rapidly at startup, excessive compressive stress will be generated on the upper and lower lower surfaces, and excessive tensile stress will be generated on the lower and lower upper surfaces. Occurs.

FIG. 6 shows the relationship between the temperature of the exhaust heat recovery boiler inlet gas and the temperature difference between the upper and lower surfaces of the reheater pipe at the time of startup, taking the lower pipe as an example. That is, at the time of start-up, the exhaust heat recovery boiler inlet gas temperature rises as the gas turbine load increases, and after the gas temperature reaches its maximum, the temperature difference between the upper and lower surfaces of the reheater lower pipe is maximized, and the reheater The thermal stress generated in the lower header is also maximum. Then, when the temperature of the exhaust gas rises rapidly at the time of startup, the temperature difference between the lower parts of the reheater lower pipe becomes excessive, and excessive thermal stress is generated in the lower part of the reheater pipe.

Although FIG. 6 shows the relationship between the exhaust heat recovery boiler inlet gas temperature and the temperature difference between the upper and lower surfaces of the reheater lower pipe at startup, the exhaust heat recovery boiler inlet gas temperature and the reheater upper pipe are shown. The same applies to the relationship of the temperature difference between the upper and lower surfaces.

In view of the above, the present invention provides an exhaust heat recovery boiler equipped with a reheater, in which excessive heat stress is not generated in the reheater header when starting. With the goal.

[0016]

A first aspect of the present invention is an exhaust heat recovery boiler with a reheater provided with a baffle plate in a gas flow region so that a gas turbine exhaust gas does not bypass a heat transfer surface of the exhaust heat recovery boiler. The amount of fuel input to the gas turbine is controlled in accordance with the temperature distribution on the pipe wall of the reheater header.

The second aspect of the invention is characterized in that the flow rate of the steam for cooling the reheater supplied to the reheater is controlled in accordance with the temperature distribution on the pipe wall of the reheater header. And

[0018]

[Operation] When the temperature of the gas turbine exhaust gas rises sharply at startup and the temperature distribution on the wall surface of the reheater header changes and the temperature difference between the upper and lower surfaces exceeds a predetermined value, the gas turbine fuel input decreases. In this way, the steam flow rate for cooling the reheater supplied to the reheater is increased, and excessive heat stress is prevented from occurring in the reheater header.

[0019]

Embodiments of the present invention will be described below with reference to FIGS. In the figure, the same parts as those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a block diagram of an exhaust heat recovery combined cycle power plant with a double pressure type reheater, and FIG. 2 is FIG.
FIG. 3 is an enlarged view of the control device section of FIG.

By the way, on the upper surface of the reheater lower pipe header 32, a temperature detector 33 for measuring the metal temperature on the upper face of the pipe header.
and a temperature detector 33b for measuring the metal temperature of the lower surface of the lower pipe 32.
Is provided. The temperature detection signals detected by both the temperature detectors 33a and 33b are input to a comparator 34, respectively, where the temperature detection signals from both the temperature detectors 33a and 33b are compared, and the difference between them, that is, the lower pressure difference 3
The temperature difference between the upper and lower surfaces of 2 is output. The output from the comparator 34 is input to the function generator 35, and the output from the function generator 35 supplies a fuel to the combustor 2 of the gas turbine as a control signal via the calculator 36. Control valve 38 provided in the fuel supply line 37
Entered in.

However, when the temperature of the exhaust heat recovery boiler inlet gas rises at the time of starting the plant, since steam is not flowing in the reheater lower part header 32 at this time, the lower part of the lower part of the reheater lower inlet pipe temperature 32 The temperature difference between the upper and lower sides of the pipe header 32 becomes large.

When the temperature difference increases in this way, the output from the comparator 34 also increases. When this output, that is, the temperature difference between the upper and lower surfaces reaches the set temperature, control is performed via the function generator 35 and the calculator 36. A signal is applied to the control valve 38, the control valve 38 is controlled in the closing direction, the gas turbine fuel input amount is reduced, and the gas turbine fuel input amount is controlled so that the upper and lower surface temperature difference of the reheater lower pipe header is not excessive. Is controlled.

Therefore, it is possible to prevent excessive thermal stress from being generated in the reheater lower pipe header 32.

In the above embodiment, the control is performed by the temperature difference between the upper and lower surfaces of the lower pipe contact, but it may be controlled by the temperature difference between the upper and lower surfaces of the upper pipe contact.

FIG. 3 shows changes in the temperature difference between the inlet gas of the exhaust heat recovery boiler and the temperature difference between the upper and lower surfaces of the reheater lower pipe.

FIG. 4 is a view showing another embodiment of the present invention. An auxiliary steam supply line 41 is connected to the reheater 6 and a steam supply conduit 40 is provided in the auxiliary steam supply line 41. By controlling the control valve 42, the auxiliary steam flow rate for cooling the reheater supplied from the exhaust heat recovery boiler (not shown) of the other shaft is controlled. Then, as in the first embodiment, the steam control valve 42 has the reheater lower part header 3
The opening / closing control is performed according to the temperature difference between the upper and lower surfaces of the two.

However, when the temperature of the exhaust heat recovery boiler inlet gas rises and the temperature difference between the upper and lower surfaces of the reheater lower header 32 exceeds the set value, the output signal from the function generator 35 causes the calculator 36 to operate. A control signal is applied to the control valve 42 through the control valve 42, and the control valve 42 is controlled in the opening direction.

Therefore, the auxiliary steam for cooling the reheater is started to be supplied to the reheater 6 from the exhaust heat recovery boiler of the other shaft, and the supply of the auxiliary steam causes an excessive temperature difference between the upper and lower surfaces of the reheater lower pipe. It is controlled not to become.

In this embodiment as well, the control valve 42 may be controlled by the temperature difference between the upper and lower surfaces of the upper pipe assembly. In the above embodiment, the auxiliary steam for cooling the reheater is supplied to the reheater from the exhaust heat recovery boiler of the other shaft.However, the auxiliary steam for cooling the reheater is appropriately supplied from the auxiliary steam header. The steam may be supplied to the reheater.

[0031]

As described above, in the present invention, the temperature difference between the upper and lower surfaces of the reheater pipe header is controlled so as not to be excessive, so that the thermal stress of the reheater pipe header can be suppressed to a low level. It is possible to extend the service life of the pipe. further,
In the case of controlling the gas injection amount of the gas turbine, the gas turbine load increase rate can be increased to the limit within the range where the thermal stress of the reheater header is not excessive, so that the start-up time of the plant can be shortened. . Further, in the case of controlling the auxiliary steam for cooling to the reheater, it is possible to start up without limiting the gas turbine load increase rate due to the thermal stress of the reheater header. Therefore, a quick start of the plant can be realized. In addition, the flow rate of the steam for cooling the reheater can be minimized, and the efficiency of the entire plant can be prevented from being lowered.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an exhaust heat recovery combined cycle power generation plant of the present invention.

FIG. 2 is an enlarged view showing a control device portion shown in FIG.

FIG. 3 is an explanatory diagram showing the relationship between the exhaust heat recovery boiler inlet gas temperature and the temperature difference between the upper and lower surfaces of the reheater lower pipe at startup.

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional exhaust heat recovery type combined cycle power generation plant.

FIG. 6 is an explanatory diagram showing the relationship between the exhaust heat recovery boiler inlet gas temperature at startup and the temperature difference between the upper and lower surfaces of the lower reheater pipe in the conventional apparatus.

[Explanation of symbols]

 1 Air Compressor 2 Combustor 3 Gas Turbine 4 Exhaust Heat Recovery Boiler 6 Reheater 17 Condenser 20 High Pressure Steam Turbine 22 Medium Pressure Steam Turbine 23 Low Pressure Steam Turbine 26 Low Pressure Bypass Line 28 Medium Pressure Bypass Line 30 High Pressure Bypass Line 31 Baffle plate 32 Reheater lower heading 33a, 33b Temperature detector 34 Comparator 35 Function generator 36 Operator 37 Gas turbine fuel supply line 38, 42 Control valve 41 Auxiliary steam supply line

Claims (2)

[Claims] 1. In an exhaust heat recovery boiler with a reheater in which a baffle plate is provided in a gas flow region so that a gas turbine exhaust gas does not bypass a heat transfer surface of an exhaust heat recovery boiler, a pipe wall surface of a reheater header is provided. An exhaust heat recovery boiler characterized in that the amount of fuel input to the gas turbine is controlled in accordance with the state of temperature distribution. 2. An exhaust heat recovery boiler with a reheater, wherein a baffle plate is provided in the gas flow region so that the gas turbine exhaust gas does not bypass the heat transfer surface of the exhaust heat recovery boiler. The exhaust heat recovery boiler is characterized in that the flow rate of steam for cooling the reheater supplied to the reheater is controlled in accordance with the temperature distribution state.