JP4099177B2 - Heat exchange device with preheating function and preheating method thereof - Google Patents

Description

  The present invention relates to a heat exchange device used in a regenerative cycle gas turbine, and more particularly to a heat exchange device with a preheating function and a preheating method thereof.

  The regeneration cycle gas turbine exchanges heat between exhaust gas and compressed air with a heat exchanger (regenerator), and supplies the compressed air that has become high temperature by heat exchange to the combustor. Reduction can be achieved and the thermal efficiency of the entire gas turbine can be increased.

  However, since the heat exchanger is exposed to an exhaust gas of 500 ° C. or higher during operation and becomes normal temperature during operation stop, a large thermal stress acts repeatedly by repeated operation and stop. Thereby, damage such as fine cracks (cracks) occurred, and the life of the heat exchanger was shortened.

In addition, the reformer's compressed air preheater and process gas preheater attached to the fuel cell power plant have been improved to extend the life against repeated thermal stress caused by the temperature difference between the high temperature side fluid and the low temperature side fluid. However, no consideration is given to thermal stress applied to the heat exchanger (preheater) by repeated operation and stoppage.
JP-A-5-105402

  Therefore, the present invention provides a preheating function that reduces the load of thermal stress on the heat exchanger and extends the life of the heat exchanger by simply adding a simple structure to the heat exchanger of the regenerative cycle gas turbine. It is an object of the present invention to provide a heat exchange device with a heat exchanger and a preheating method thereof.

In order to achieve the above object, a heat exchange device having a preheating function according to the present invention includes a heat exchanger for exchanging heat between exhaust gas from a gas turbine and compressed air from a compressor, and the heat exchanger. An electric heater that preheats the heat exchanger while the operation is stopped and brings the heat exchanger close to the operating temperature when the operation is resumed , and the heater is near the exhaust gas inlet to the core in the heat exchanger It is attached to .

According to this configuration, the heat exchanger is heated by the heater while the operation of the heat exchanger is stopped. In other words, when the operation of the heat exchanger starts (when the operation of the gas turbine starts), the heat exchanger is heated by the heater. Since the temperature difference between the exhaust gas flowing into the heat exchanger and the heat exchanger is reduced, the heat load on the heat exchanger is reduced when the exhaust gas flows in, and the heat is heated. Stress is reduced. Thereby, lifetime improvement of a heat exchanger can be achieved. In addition, since a large heat load is applied to the vicinity of the exhaust gas inlet to the core in the heat exchanger and the thermal stress is concentrated when the exhaust gas flows in, the heat that causes damage can be obtained by heating the vicinity of the inlet with a heater. The load can be suppressed and the thermal stress can be reduced. Furthermore, since the heater is mounted not in the entire area from the inlet to the outlet of the heat exchanger but in the vicinity of the inlet, the heater can be easily attached and the cost can be reduced.

  In a preferred embodiment of the present invention, the heater is mounted on the outer periphery of the heat exchanger.

  According to this configuration, since the heater is positioned not on the inner peripheral side of the heat exchanger but on the outer peripheral side, the heater mounting work and the maintenance work are facilitated, and workability is improved.

  In a preferred embodiment of the present invention, there is further provided a controller for turning off and on the heater based on the timing of operation stop and operation start of the heat exchanger, respectively.

  According to this configuration, the heater on / off operation is automatically performed by the controller based on the operation stop timing and the operation start timing of the heat exchanger, so the field worker manually turns on / off the heater. Troublesome work becomes unnecessary. Moreover, an appropriate on / off operation can be performed without timing errors.

  In the preheating method of the heat exchanger with a preheating function according to the present invention, the heater is turned off and on in accordance with the timing of stopping and starting the operation of the heat exchanger in the heat exchange apparatus of the present invention.

  According to this configuration, since the heater is turned off and on in accordance with the timing of operation stop and operation start of the heat exchanger, the heater can be operated only while the gas turbine is stopped to efficiently preheat the heat exchanger. .

  According to the heat exchange device having the preheating function and the preheating method according to the present invention, the heat exchanger is already heated and warmed at the start of the operation of the heat exchanger, so when the exhaust gas flows into the heat exchanger, The heat load applied to the heat exchanger is reduced, and the thermal stress is reduced. Thereby, lifetime improvement of a heat exchanger can be achieved.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram showing a regeneration cycle gas turbine to which a heat exchange device with a preheating function according to the present invention is applied. The regeneration cycle gas turbine shown in FIG. 1 includes a gas turbine 1 and a heat exchange device 2 called a recuperator (regenerator) attached thereto.

  The gas turbine 1 includes a compressor 3 that sucks air from the outside to generate compressed air A, a combustor 4 that supplies fuel F to the compressed air A and burns it, and a combustion gas G from the combustor 4. It has a turbine 5 to be driven and drives, for example, a generator 7 as a load. In the case of the single shaft type, the compressor 3, the turbine 5, and the generator 7 are connected to the single rotating shaft 6.

  The heat exchange device 2 includes a heat exchanger 21 that performs heat exchange between the exhaust gas EG from the turbine 5 and the compressed air A from the compressor 3, and a heater 22 that heats the heat exchanger 21. Yes. The heater 22 is controlled by the controller 8.

  The heat exchanger 21 and the compressor 3 are connected by an air introduction passage 11A, and the compressed air A from the compressor 3 is sent to the heat exchanger 21 through the air introduction passage 11A. The turbine 5 and the heat exchanger 21 are connected by an exhaust gas introduction passage 11B, and the exhaust gas EG from the turbine 5 is sent to the heat exchanger 21 via the exhaust gas introduction passage 11B. The heat exchanger 21 and the combustor 4 are connected to each other through an air outlet passage 11C. The compressed air A, which has been heated to the exhaust gas EG in the heat exchanger 21 and has reached a high temperature, passes through the air outlet passage 11C. To the combustor 4. On the other hand, the exhaust gas EG after heat exchange with the compressed air A is introduced into, for example, an exhaust heat boiler and used to generate steam, and then released into the atmosphere.

  FIG. 2 is an enlarged perspective view schematically showing the mounting state of the heater 22 to the heat exchanger 21. As shown in the figure, the heat exchanger 21 has an exhaust gas EG inflow opening 21a on the front side, an exhaust gas EG outflow opening 21b on the rear side, and a header tank for allowing compressed air A to flow into one of the side surfaces. 21c has a header tank 21d for allowing the compressed air A after heat exchange to flow out on the other side surface side. The heat exchanger 21 includes, for example, a rectangular parallelepiped core 60 indicated by a two-dot chain line, and an exhaust duct 21e for introducing exhaust gas that forms the inflow opening 21a on the front surface of the core 60, and the outflow opening 21b on the rear surface. The exhaust gas outlet outlet duct 21f to be formed is joined to the left and right side surfaces by header tanks 21c and 21d by welding.

  The core 60 of the heat exchanger 21 is a plate fin type heat exchanger in which a plurality of plates 61 and fins 62 are alternately stacked as shown in FIG. The front surface of the core body 60 is an exhaust gas EG inlet 63 and the rear surface is an exhaust gas EG outlet 64. A passage 65 of the exhaust gas EG is formed from the front surface to the rear surface direction, and from the right side to the left side. A passage 66 for compressed air A is formed. A rectangular column 67 is disposed at the end of the core 60 as a strength member.

  In the vicinity of the exhaust gas inlet 63 of the core 60 on the outer peripheral side of the heat exchanger 21 shown in FIG. 2, a long electric heater 22 such as a thin tube heater starts from the first terminal 23 a on the outer periphery of the heat exchanger 21. The second terminal 23b is mounted in multiple windings (the illustrated one is triple winding), and both terminals 23a and 23b are connected to a power source. The heater winding 22a of the first turn, the heater winding 22b of the second turn, and the heater winding 22c of the third turn forming the heater 22 are all fixed to the heat exchanger 21 by a plurality of fixtures 24. . The terminals 23a and 23b and the fixture 24 are all made of a heat resistant material. The heater 22 is connected to a power source via the switch 25 in FIG. 1, and the switch 25 is on / off controlled by the controller 8.

  Next, the operation of the heat exchange device with a preheating function according to the above configuration will be described with reference to FIG. First, in the regeneration cycle gas turbine, air is sucked from the atmosphere, and this air is compressed by the compressor 3. The compressed air A is sent to the heat exchanger 21 of the heat exchange device 2 via the air introduction passage 11A, and heat exchange with the exhaust gas EG from the turbine 5 sent via the exhaust gas introduction passage 11B. Thus, the compressed air A is heated. This compressed air A is sent to the combustor 4 through the air outlet passage 11C, mixed with the supplied fuel F, and burned to generate a high-temperature and high-pressure gas G. This gas G is sent to the turbine 5 to drive it and to drive a load such as a generator 7 connected to the turbine 5. The exhaust gas EG discharged from the turbine 5 is introduced into the heat exchanger 21 through the exhaust gas introduction passage 11B, and then released to the atmosphere through an exhaust heat boiler (not shown).

  In the regenerative cycle gas turbine operating as described above, in particular, when the gas turbine is started, the vicinity of the inlet 63 of the core 60 of the heat exchanger 21 is closer to the inlet 63 than the heat exchanger 21 that has not been sufficiently warmed. 3 is exposed to high-temperature exhaust gas EG flowing into the heat exchanger 21, the vicinity of the inlet 63 is suddenly heated and a large heat load is applied, and the plate 61 and the prism 67 shown in FIG. There is a possibility that damage such as fine cracks (cracks) due to thermal stress occurs in the welded portion between the container 11 and the header tanks 21c and 21d, and the life of the core 60, that is, the life of the heat exchanger 21 may be shortened. . Therefore, in the present invention, before the gas turbine 1 of FIG. 1 is started, the vicinity of the inflow opening 21a of the heat exchanger 21 is preheated and warmed by the heater 22 controlled by the controller 8.

  The on / off automatic switching operation of the heater 22 will be specifically described. When the operation of the heat exchanger 21 shown in FIG. 1 is stopped (for example, when the operation of the gas turbine 1 is stopped at night), the heater 22 is automatically turned on under the control of the controller 8 in response to the stop instruction, and the next time ( For example, the heat exchanger 21 is heated to a heater 22 prior to the start of the gas turbine 1 so that the heat exchanger 21 is warmed to a certain temperature or more at the start of the gas turbine 1 (for example, the next morning when the operation of the gas turbine 1 is resumed). Preheat in advance.

  As shown in FIG. 4, the preliminary heating by the heater 22 is automatically performed by the control of the controller 8 (FIG. 1) in response to a stop command when the operation of the gas turbine 1 is stopped manually or automatically. The heater is turned on, and the heater 22 (FIG. 1) is continuously operated, for example, at night, as indicated by the symbol H. The next morning when the operation of the gas turbine 1 is resumed, the gas turbine 1 is started, and when the turbine rotation speed reaches, for example, 95% and the power supply is established, the heater is automatically turned off under the control of the controller 8 (FIG. 1). By doing so, when the gas turbine 1 is operated, the heat exchanger 21 in FIG. 1 is already warmed by the preheating, and the high-temperature exhaust gas EG flows into the core 60 of the heat exchanger 21 from the inlet 63. However, since the temperature difference between the inlet 63 and the exhaust gas EG is small, a large heat load is not applied to the inlet 63. As a result, since the load of thermal stress on the core 60 is reduced, the plate 61 and the prisms 67 of FIG. 3, which are strength members near the inflow port 63, the heat exchanger 21 and the header tanks 21c and 21d of FIG. It is possible to suppress the occurrence of damage such as fine cracks (cracks) due to thermal stress in the welded portion.

  Since the heater 22 is turned on and off automatically by the controller 8 during the operation stop and operation of the gas turbine 1, that is, based on the timing of operation stop and operation start of the heat exchanger 21, the gas turbine 1 Prior to the operation of the gas turbine 1, the on-site worker who is engaged in the operation operation 1 is freed from troublesome work such as going to work early in the morning and turning on the heater 22 manually. Further, since the heater 22 is automatically turned off and on in accordance with the operation stop timing and the operation start timing of the heat exchanger 21, respectively, an appropriate on / off operation can be performed without erroneous timing.

  Furthermore, since the heater 22 is mounted on the outer peripheral side, the heater 22 can be easily attached and maintained, and workability is improved.

  The heater 22 may be wound around the entire area from the inlet 63 to the outlet 64 of the core 60, but as shown in the drawing, the heater 22 is mounted only in the vicinity of the inlet 63 so that the heat exchanger 21 can be installed. There is a sufficient preheating effect for the core 60, and in addition to the mounting of the heater 22 on the outer peripheral side of the heat exchanger 21, the mounting operation of the heater 22 can be improved and the cost can be kept low.

1 is a system diagram showing a regeneration cycle gas turbine to which a heat exchange device with a preheating function according to the present invention is applied. FIG. It is a perspective view which shows the mounting state of the heater to a heat exchanger. It is a perspective view which shows the core of a heat exchanger. It is a time chart which shows the relationship between a gas turbine operation state and heater ON / OFF.

Explanation of symbols

1 Gas Turbine 2 Heat Exchanger 3 Compressor 4 Combustor 5 Turbine 21 Heat Exchanger 22 Heater 8 Controller 60 Core 63 Inlet A Compressed Air EG Exhaust Gas

Claims (4)

A heat exchanger for exchanging heat between the exhaust gas of the gas turbine and the compressed air from the compressor;
An electric heater that preheats the heat exchanger during operation stop of the heat exchanger and brings the heat exchanger close to the operating temperature when the operation is resumed ,
The heater is a heat exchange device with a preheating function, which is mounted in the vicinity of an exhaust gas inlet to the core in the heat exchanger.   The heat exchanger according to claim 1, wherein the heater is attached to the outer periphery of the heat exchanger and has a preheating function. 3. The heat exchanging apparatus with a preheating function according to claim 1, further comprising a controller for turning off and on the heater based on the timing of operation stop and operation start of the heat exchanger. A method of preheating a heat exchange apparatus according to claim 1 or 2,
A preheating method for a heat exchange device in which the heater is turned off and on in accordance with the operation stop timing and operation start timing of the heat exchanger, respectively.

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