JP6246659B2 - Leakage detection device and leak detection method for heat exchanger - Google Patents

Description

  Embodiments described herein relate generally to a heat exchanger leak detection device and a leak detection method.

  The fuel gas system in the gas turbine combined cycle power generation facility is provided with a fuel gas heater that raises the temperature of the fuel gas supplied to the gas turbine in order to increase the thermal efficiency of the gas turbine.

  An exhaust heat recovery boiler that recovers exhaust heat from the gas turbine is provided, and the exhaust heat recovery boiler is provided with a heated water pipe that circulates water for recovering the exhaust heat. The water supplied into the exhaust heat recovery boiler through the heating water pipe is warmed in the exhaust heat recovery boiler, and is discharged from the exhaust heat recovery boiler through the heating water pipe in the state of being heated water. Heat exchange between the heated water heated by the exhaust heat recovery boiler and the fuel gas supplied to the gas turbine is performed in the fuel gas heater, and the supply temperature of the fuel gas supplied to the gas turbine is increased. Can be warmed.

  Generally, a shell and tube type heat exchanger is used as a fuel gas heater. As a shell and tube type heat exchanger, the following two configurations are adopted. One configuration is a configuration in which a gas chamber filled with a gas for heat exchange is formed in the heat exchanger, and a heated water pipe for circulating heated water is arranged in the gas chamber. The other configuration is a configuration in which a warming water chamber filled with warming water is supplied to the heat exchanger, and a gas pipe for distributing gas is arranged in the warming water chamber.

  In the case of a shell-and-tube heat exchanger, if the tube (heated water pipe or gas pipe in the heat exchanger) in the heat exchanger is damaged and a leak due to tube leak occurs in the unlikely event, the fuel gas pipe There is a concern that mixing of warm water on the side or mixing of fuel gas on the warm water pipe side may occur.

  In the heat exchanger where the heated water piping is arranged in the gas chamber where the gas is filled in the heat exchanger, as a countermeasure when heated water is mixed into the fuel gas piping side, the part on the upstream side of the gas turbine of the fuel gas piping A method using a fuel gas scrubber provided in the factory is employed. The fuel gas scrubber is provided in the fuel gas pipe as a device for removing moisture, dust and the like contained in the fuel gas.

  When a tube leak occurs, the water level in the fuel gas scrubber is monitored by utilizing the fact that the warm water mixed in the fuel gas accumulates in the fuel gas scrubber. When the monitored water level reaches a preset water level, an alarm and protection interlock are performed.

However, in the heat exchanger in which the heated water pipe is arranged in the gas chamber, no countermeasure or detection function for the case where fuel gas is mixed into the heated water pipe side has been provided. Therefore, in the unlikely event, there has been a problem of an accident caused by mixing fuel gas into the heated water.
That is, there is a problem with respect to an accident that occurs when heated water is supplied into the exhaust heat recovery boiler in a state where fuel gas is mixed.

  In a heat exchanger where gas piping is arranged in the warming water chamber where the heat exchanger is filled with warming water, as a countermeasure when warming water enters the fuel gas piping side, a fuel gas scrubber provided in the fuel gas piping is used. The installed water level gauge is used to monitor the mixing of warm water into the fuel gas.

  In addition, in the heat exchanger in which gas piping is arranged in the warming water chamber, as a countermeasure when fuel gas is mixed into the warming water side, a configuration in which a gas reservoir is provided at the top of the container configured as a sealed container. Proposed. As what is equipped with this structure, the gas heating system (refer patent document 1), the gas leak detection system (refer patent document 2) of an airtight container type heat exchanger, etc. are proposed, for example.

In the gas heating system described in Patent Document 1, as shown in FIG. 2, a pot 50 configured as a sealed container is provided in the heating liquid circulation path 55, and a gas reservoir 51 is formed at the upper end of the pot 50. ing. A pinhole 52 formed as a fine hole is formed in the upper end portion of the gas reservoir portion 51, and gas detection means 53 is arranged such that a gas leaking from the pinhole 52 is arranged facing the upper portion of the pinhole 52. It is configured to detect with.
In addition, a case where the water level in the gas reservoir 51 is detected by the liquid level detection means 54 and the amount of gas leakage to the warm water is large is provided.

  In the gas leak detection system described in Patent Document 2, a gas reservoir is formed in the upper part of the heat exchanger of the hermetic container, and a water level gauge is provided in the gas reservoir. By detecting the water level in the gas reservoir with a water level gauge, the amount of fuel gas leaked from the gas pipe and accumulated in the gas reservoir is detected.

JP 2012-202641 A JP 2005-134057 A

  In the configuration in which the gas reservoir is formed at the upper end of the hermetic container using the pot 50 or the heat exchanger that is a hermetic container as described in Patent Documents 1 and 2, gas easily accumulates in the gas reservoir. Therefore, it is necessary to arrange the sealed container in a vertically standing state. In addition, the inner surface shape of the upper end portion of the sealed container needs to be configured to have an inner surface shape in which the upper end side is tapered in order to make it easy for gas leaked from the gas piping to gather in the gas reservoir.

  For this reason, a gas reservoir that protrudes further upward is provided in a vertically standing sealed container, so that a place where this kind of sealed container is installed is restricted. In addition, a high degree of processing accuracy is required for manufacturing a sealed container having a protruding gas reservoir, and the manufacturing price of the sealed container increases.

  In the embodiment according to the present invention, the heating water pipe is provided in the gas chamber in which the gas is filled in the heat exchanger without using the heat exchanger or pot of the sealed container provided with the gas reservoir portion at the upper end as described above. Provided are a heat exchanger leak detection device and a leak detection method that can detect the mixing of fuel gas into a heated water pipe with a simple configuration and can be manufactured at a low cost.

  A heat exchanger leak detection apparatus according to an embodiment of the present invention is a heat exchanger leak detection apparatus in a gas turbine combined cycle power generation facility, and performs heat exchange with fuel gas in the heat exchanger. It is characterized by comprising a gas reservoir connected to a downstream portion of the heated water pipe, and a water level detector provided in the gas reservoir.

  Moreover, in the leak detection method of the heat exchanger which concerns on embodiment of this invention, it is a leak detection method using the leak detection apparatus of the heat exchanger which concerns on the said embodiment, Comprising: The said water level detector WHEREIN: In the said gas reservoir part And a step of detecting the occurrence of fuel gas leakage when the detected water level reaches a predetermined water level.

  According to the embodiment of the present invention, it is possible to prevent heated water mixed with fuel gas from being supplied into the exhaust heat recovery boiler, and an accident caused by supplying heated water mixed with fuel gas into the exhaust heat recovery boiler Can be prevented.

1 is a schematic system diagram showing a first embodiment. It is a schematic system diagram which shows a prior art example.

  The configuration of the heat exchanger in the gas turbine combined cycle power generation facility according to the embodiment of the present invention will be described with reference to FIG.

[Embodiment]
As shown in FIG. 1, the gas turbine combined cycle power generation facility 1 includes a fuel gas supply facility 2, a heat exchanger 4, a fuel gas scrubber 5, a gas turbine combustor 6, and a gas turbine 7.

The fuel gas that has flowed into the fuel gas pipe 3 a from the fuel gas supply facility 2 flows into the first gas chamber 30 a that is partitioned by the partition wall 32 in the heat exchanger 4. The fuel gas that has flowed into the first gas chamber 30a flows into the third gas chamber 30c through the opening 31a, and between the heated water flowing in the tube 18 piped in the third gas chamber 30c. Heat exchange takes place.
In addition, although the tube 18 is a part of structure of the heating water piping 9a-9c formed as a circulation path, the part distribute | arranged in the 3rd gas chamber 30c in the heat exchanger 4 is described as the tube 18. ing.

  By performing heat exchange for supplying the heat of the heated water to the fuel gas via the tube 18, the fuel gas is heated to a predetermined temperature. Then, the fuel gas heated by heat exchange flows into the second gas chamber 30b through the opening 31b.

  The fuel gas flowing out from the second gas chamber 30b flows through the fuel gas pipe 3b into the fuel gas scrubber 5 that removes moisture in the fuel gas. The fuel gas scrubber 5 is disposed for the purpose of removing moisture and removing dust from the heated fuel gas.

  The fuel gas from which moisture has been removed by the fuel gas scrubber 5 is supplied to the gas turbine combustor 6 through the fuel gas pipe 3c. By being configured in this way, the fuel gas supplied to the gas turbine combustor 6 can be preheated to a predetermined temperature. Thereby, the combustion efficiency in the gas turbine combustor 6 can be increased. The combustion gas burned in the gas turbine combustor 6 can be supplied to the gas turbine 7 to drive the gas turbine 7.

  In order to use the exhaust heat generated in the gas turbine 7, an exhaust heat recovery boiler 8 is connected to the gas turbine 7. In the exhaust heat recovery boiler 8, a heated water pipe 9 c for flowing water heated by exhaust heat is provided. By flowing through the heated water pipe 9c, the water is heated to become heated water, and flows into the tube 18 in the heat exchanger 4 from the heated water pipe 9a.

  As the heated water heated in the exhaust heat recovery boiler 8 flows in the tube 18, the fuel gas flowing in the third gas chamber 30c can be heated. The warming water pipes 9a and 9b are provided with valves 21a and 21b that are normally open, respectively.

  The heated water that has undergone heat exchange in the heat exchanger 4 becomes low-temperature water and flows into the heated water pipe 9c through the heated water pipe 9b and into the exhaust heat recovery boiler 8. Below, the warmed water which came out of the heat exchanger 4 is called water. And water is heated again and becomes warm water. In this way, the heated water for heating the fuel gas is fed from the exhaust heat recovery boiler 8 to the heat exchanger 4 through the warm water piping 9a, exchanges heat with the fuel gas, and again the exhaust heat recovery boiler. The series of steps back to 8 will be repeated.

  An air vent pipe 13a is connected to the warming water pipe 9b, and air contained in the warming water pipe 9b can be extracted. That is, in the heat exchanger 4, when the fuel gas is mixed into the heated water, the mixed fuel gas can be collected by the air vent pipe 13a. The front end of the air vent pipe 13a is bent in a downward U-shape to prevent air in the atmosphere from flowing into the heated water pipe 9b through the air vent pipe 13a. The air vent pipe 13a is connected to a water level detection pipe 13b that constitutes a gas reservoir. The air vent pipe 13a is disposed as a bypass pipe that bypasses the gas reservoir of the water level detection pipe 13b, and the water level detection pipe 13b. Are arranged in parallel.

(Configuration of water level detector 11)
The water level detection pipe 13b is provided with a water level detector 11 for detecting the water level of the water flowing into the water level detection pipe 13b. The water level detection pipes 13b on the upstream side and the downstream side of the water level detector 11 are provided with normally open valves 20c and 20b. In addition, a valve 20a that is normally closed is provided at a site of the air vent pipe 13a disposed between the upstream connection portion and the downstream connection portion of the water level detection pipe 13b. That is, the valve 20a functions as a shut-off valve provided in the air vent pipe 13a configured as a bypass pipe, and the water flowing into the air vent pipe 13a from the heated water pipe 9b is used as a gas reservoir for the water level detecting pipe 13b side. Functions as a shut-off valve.

  By keeping the valve 20a in the closed state, the water that has flowed out of the heat exchanger 4 and branched to the air vent pipe 13a flows into the water level detection pipe 13b. In the water level detection pipe 13b, the water level exists up to a predetermined height due to the relationship between the water pressure of the water flowing in the heated water pipe 9b and the atmospheric pressure. However, when the fuel gas leaks to the tube 18 side in the heat exchanger 4, the heated water mixed with the fuel gas flows in the heated water pipe 9b.

  The fuel gas mixed in the warm water flows into the air vent pipe 13a from the warm water pipe 9b and lowers the water level in the water level detection pipe 13b. However, the water level in the water level detection pipe 13b decreases. Is detected by the water level detector 11, it can be detected that the fuel gas is mixed into the heated water in the heat exchanger 4.

(Effects of water level detector 11)
When the water level detector 11 detects that the fuel gas is mixed into the warm water (water in the warm water pipe 9b), it is determined that the fuel gas leaks in the heat exchanger 4. be able to.

  That is, when a control device (not shown) that receives a detection signal from the water level detector 11 determines that fuel gas is leaking in the heat exchanger 4 due to a drop in the water level, the valves 21a and 21b are closed. Can be valved.

  Thereby, the outflow diffusion of the fuel gas to the heated water pipe 9b can be prevented. And it can prevent that the warm water (water in the warm water piping 9b) in the state where fuel gas was mixed is introduced into the exhaust heat recovery boiler 8. In addition, when a control device (not shown) determines that fuel gas is mixed into the warm water (water in the warm water pipe 9b) based on the detection signal from the water level detector 11, the control for disabling the start of the gas turbine 7 is performed. It can be performed.

That is, when the control device (not shown) determines that fuel gas is mixed into the warm water (water in the warm water pipe 9b) based on the detection signal from the water level detector 11 while the gas turbine 7 is stopped, the gas turbine 7 Can be controlled so that it can not be started. When the gas turbine 7 is in operation, when a control device (not shown) determines that fuel gas is mixed into the warm water (water in the warm water pipe 9b), control is performed to safely stop the gas turbine 7. Can do. At the same time, it is possible to perform control to close the valves 21a and 21b in the heated water pipes 9a and 9b provided on the inlet side and the outlet side of the heat exchanger 4.
Thereby, the gas turbine combined cycle power generation facility 1 can be stopped safely.

(Configuration of drain pipe 14a)
The heat exchanger 4 is connected to a drain pipe 14a for draining water accumulated in the heat exchanger 4, and the drain pipe 14a is connected to a drain pipe 14a for detecting the water level in the heat exchanger 4. A water level detection pipe 14b piped in parallel is connected. And the water level detector 10 which detects the water level in the heat exchanger 4 is provided in the water level detection pipe | tube 14b.

  The water level detection pipes 14b on the upstream side and downstream side of the water level detector 10 are provided with normally open valves 22b and 22c. Further, a valve 22a that is normally closed is provided at a portion of the drain pipe 14a that connects the water level detection pipe 14b.

  When moisture is accumulated in the heat exchanger 4, the accumulated water flows in the drain pipe 14a and is discharged to the outside. By closing the valve 22a provided in the drain pipe 14a, the water flowing into the drain pipe 14a from the heat exchanger 4 flows through the water level detection pipe 14b branched from the drain pipe 14a and is discharged to the outside. Become.

(Effects of water level detector 10)
The water level detector 10 provided in the water level detection tube 14b can detect the water level in the water level detection tube 14b. Then, it is possible to detect whether water has accumulated in the heat exchanger 4 by detecting the water level in the water level detection pipe 14b.

  That is, in the heat exchanger 4, when pipe leakage occurs from the tube 18 side to the fuel gas side, warm water accumulates in the heat exchanger 4, and the drain pipe 14 a connected to the lower part of the heat exchanger 4 Leaked warm water will accumulate. And it will be discharged | emitted outside via the drain pipe 14a. By detecting the amount of water discharged to the outside through the drain pipe 14a by the water level detector 10 attached to the water level detection pipe 14b, it is possible to detect that the heated water is leaking into the heat exchanger 4. .

(Configuration of fuel gas scrubber 5)
A water level detection pipe 15 is connected to the fuel gas scrubber 5 in order to detect the amount of water accumulated in the fuel gas scrubber 5 by removing water in the fuel gas scrubber 5. The water level detection pipe 15 functions as an indicator arranged in the fuel gas scrubber 5, and the water level detection pipe 15 is provided with a water level detector 12 in order to detect the water level.
In addition, valves 23 a and 23 b that are normally open are provided at portions of the water level detection pipe 15 upstream and downstream of the water level detector 12.

(Description of water level detectors 10-12)
As a structure of the water level detectors 10-12, it can be set as the structure using the float which moves to an up-down direction with a water level, for example. By detecting the movement of the float due to the water level by an electric means, a magnetic means, or the like, the information on the detected water level can be transmitted to a control device (not shown). When the water level detected by the water level detectors 10 to 12 reaches a predetermined water level set in advance for each detector or when the water level is reduced from the preset water level, leakage of heated water or fuel gas to the heated water side Leakage can be detected.

(Effect of this embodiment)
As described above, in the embodiment of the present invention, the water level of the air vent pipe 13a is detected by the air vent pipe 13a, the water level detection pipe 13b, and the water level detector 11 connected to the heated water pipe 9b of the heat exchanger 4.

  As in the prior art, in order to detect the fuel gas itself, it is necessary to make it easy to collect the gas, and the upper end direction for collecting the gas has a tapered shape. Therefore, the installation location must be restricted. However, in the embodiment of the present invention, since the fuel gas leakage is detected by the change in the water level of the water level detection pipe, the shape does not protrude in the height direction. Therefore, it is possible to detect the state in which the fuel gas is mixed on the heated water side with a simple configuration.

  And when the leakage of fuel gas is detected, when the gas turbine combined cycle power generation facility 1 is stopped, the start of the gas turbine 7 can be disabled. In addition, during operation, the gas turbine 7 can be safely stopped or a function for safely lowering the load on the gas turbine 7 can be provided, so that the fuel to the heated water side in the heat exchanger 4 can be provided. Accidents that may occur due to gas leakage can be prevented.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, combinations, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Gas turbine combined cycle power generation equipment, 3a-3c ... Fuel gas piping, 4 ... Heat exchanger, 5 ... Fuel gas scrubber, 6 ... Gas turbine combustor, 7 ... Gas turbine, 8 ... Waste heat recovery boiler, 9a-9c DESCRIPTION OF SYMBOLS ... Warm water piping, 10-12 ... Water level detector, 13a ... Air vent pipe, 18 ... Tube, 30a-30c ... Gas chamber, 50 ... Pot, 51 ... Gas reservoir part, 52 ... Pinhole, 53 ... Gas detection means.

Claims (6)

A leak detector for a heat exchanger in a gas turbine combined cycle power generation facility,
A gas reservoir connected to a downstream portion of a heated water pipe for exchanging heat with fuel gas in the heat exchanger;
A water level detector provided in the gas reservoir,
A leakage detector for a heat exchanger, comprising: A bypass pipe that bypasses the gas reservoir is provided in parallel with the gas reservoir,
The leak detection device for a heat exchanger according to claim 1, wherein a closing valve for flowing warm water to the bypass pipe is provided on the gas reservoir side. A leak detection method using the heat exchanger leak detection device according to claim 1 or 2,
Detecting the water level in the gas reservoir by the water level detector;
Detecting that leakage of fuel gas occurs when the detected water level reaches a predetermined water level,
A leak detection method for a heat exchanger, comprising:   4. The gas turbine according to claim 3, wherein when the gas turbine of the gas turbine combined cycle power generation facility is stopped and it is detected that the fuel gas has leaked, the gas turbine cannot be started. Detection method for heat exchangers in Japan.   4. The gas turbine according to claim 3, wherein when the gas turbine of the gas turbine combined cycle power generation facility detects that the fuel gas has leaked during operation, the gas turbine is safely stopped. 5. Heat exchanger leak detection method.   When the gas turbine of the gas turbine combined cycle power generation facility detects that the fuel gas has leaked during operation, the heated water shut-off valves provided before and after the heat exchanger are closed. The method for detecting leakage of a heat exchanger according to claim 3.

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