JP2021006719A - Natural gas-fired combined cycle power generation method - Google Patents

Abstract

To provide a natural gas-fired combined cycle power generation system capable of suppressing generation of ice coating in a vaporizer.SOLUTION: A natural gas-fired combined cycle power generation system (1) includes a vaporizer (10), a cooler (20), a circulation flow passage (30), a pump (40), and a gas turbine-combined power generator (50). The vaporizer (10) has: an intermediate medium evaporation part (E1) which evaporates at least a part of the intermediate medium (M) by exchanging heat between an intermediate medium (M) which has a freezing point lower than a freezing point of water and water flown out of the cooler (20); and a liquefaction natural gas vaporization part (E2) which vaporizes at least a part of the liquefaction natural gas by heat exchanging between the intermediate medium (M) and the liquefaction natural gas.SELECTED DRAWING: Figure 1

Description

The present invention relates to a natural gas-fired combined cycle power generation method.

Conventionally, a natural gas-fired combined cycle power generation system is known in which cold heat recovered from liquefied natural gas in a vaporizer for vaporizing liquefied natural gas (LNG) is used to cool the air supplied to a gas turbine combined power generation device. There is.

For example, Patent Document 1 includes an LNG vaporizer, a gas turbine intake cooler, a gas turbine intake cooling water circulation system path, a gas turbine intake cooling water circulation pump, and a gas turbine power generation device. The equipment is disclosed. The LNG vaporizer includes a heat transfer tube for flowing LNG. In this LNG vaporizer, LNG is vaporized by exchanging heat between LNG flowing in the heat transfer tube and water in contact with the surface of the heat transfer tube. The gas turbine intake cooler cools the air by exchanging heat between the water (cooling water) flowing out from the LNG vaporizer and the air. The gas turbine intake cooling water circulation system path connects the LNG vaporizer and the gas turbine intake cooling system. Water flows through the LNG vaporizer and the gas turbine intake cooler in this order by circulating in the gas turbine intake cooling water circulation system path. The gas turbine intake cooling water circulation pump is provided in a portion of the gas turbine intake cooling water circulation system path on the downstream side of the gas turbine intake cooler. The gas turbine power generator includes a gas turbine compressor that compresses the air flowing out of the cooler, and a gas turbine that is driven by a mixed gas of the air discharged from the gas turbine compressor and the combustion gas of natural gas (NG). It has a generator, which is connected to a gas turbine. In this facility, the air supplied to the gas turbine compressor of the gas turbine power generator is cooled by the cold heat recovered from the LNG by the water in the LNG vaporizer.

Japanese Unexamined Patent Publication No. 06-21001

In the vaporizer of the LNG-fired combined cycle power generation facility described in Patent Document 1, icing may occur on the surface of the heat transfer tube through which LNG flows.

An object of the present invention is to provide a natural gas-fired combined cycle power generation system and a natural gas-fired combined cycle power generation method capable of suppressing the occurrence of icing in a vaporizer.

According to the present invention, cold heat recovered from the liquefied natural gas in a vaporizer for vaporizing the liquefied natural gas is supplied to a gas turbine and a gas turbine combined power generation device having a gas turbine generator connected to the gas turbine. A natural gas-fired combined cycle power generation method used for cooling air, in which the vaporization step of heating at least a part of the liquefied natural gas with water and the water in the vaporization step are described. A cooling step in which the air supplied to the gas turbine combined power generator is cooled in the cooler by the cold heat recovered from the liquefied natural gas, and a part of the natural gas obtained in the vaporization step and the water flowing out from the cooler. The natural gas is heated by exchanging heat in the heating unit, and in the vaporization step, water is recovered from the air by cooling the air in the cooling step in the vaporizer. By supplying the generated heat to an intermediate medium having a freezing point lower than the freezing point of water to evaporate at least a part of the intermediate medium, and by heating the liquefied natural gas with the intermediate medium, the liquefied natural gas Provided is a natural gas-fired combined cycle power generation method in which at least a part of water is vaporized and another part of water flowing out of the cooler is allowed to flow into the vaporizer without passing through the heating part. To do.

In the vaporization step of this natural gas-fired combined cycle power generation method, the liquefied natural gas is vaporized in the vaporizer via an intermediate medium (propane or the like) having a freezing point lower than the freezing point of water. The generation of ice is suppressed.

A part of the water that has exchanged heat with the natural gas in the heating portion may be merged with the other portion of the water and flowed into the vaporizer.

As described above, according to the present invention, it is possible to provide a natural gas-fired combined cycle power generation system and a natural gas-fired combined cycle power generation method capable of suppressing the occurrence of icing in a vaporizer.

It is a figure which shows the outline of the structure of the natural gas-fired combined cycle power generation system of 1st Embodiment of this invention. It is an enlarged view around the vaporizer and the warmer of 1st Embodiment. It is a figure which shows the modification of the natural gas-fired combined cycle power generation system shown in FIG. It is a figure which shows the outline of the structure of the natural gas-fired combined cycle power generation system of the 2nd Embodiment of this invention. It is an enlarged view around the vaporizer and the warmer of 2nd Embodiment.

A preferred embodiment of the present invention will be described below with reference to the drawings.

(First Embodiment)
The natural gas-fired combined cycle power generation system 1 of the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. In the natural gas-fired combined cycle power generation system 1, the cold heat recovered from the liquefied natural gas via water in the vaporizer 10 for vaporizing the liquefied natural gas (LNG) is supplied to the gas turbine combined power generation device 50. It is a power generation system that generates power with the gas turbine combined power generation device 50 while being used for cooling. Specifically, the natural gas-fired combined cycle power generation system 1 includes a vaporizer 10, a cooler 20, a circulation flow path 30, a pump 40, and a gas turbine combined power generation device 50. The circulation flow path 30 connects the vaporizer 10 and the cooler 20 in this order.

The vaporizer 10 is an intermediate medium type vaporizer (IFV) that vaporizes liquefied natural gas by exchanging heat between water and liquefied natural gas via an intermediate medium (propane or the like) having a freezing point lower than the freezing point of water. is there. That is, in the vaporizer 10, the intermediate medium is heated by water instead of brine or the like, and the liquefied natural gas is heated by the intermediate medium. Details of the vaporizer 10 will be described later.

The cooler 20 cools the air by exchanging heat between the water flowing out from the vaporizer 10 and the air.

The pump 40 is provided in a portion of the circulation flow path 30 on the downstream side of the vaporizer 10. The pump 40 sends the water (cooling water) flowing out of the vaporizer 10 to the cooler 20. In the present embodiment, the pump 41 is also provided at a portion of the circulation flow path 30 on the downstream side of the cooler 20. The pump 41 sends the water (hot water) flowing out of the cooler 20 to the vaporizer 10. Further, a cold heat storage tank 42 having a function of storing cold heat may be provided at a portion of the circulation flow path 30 between the vaporizer 10 and the pump 40. Similarly, a thermal storage tank 43 having a function of storing thermal heat may be provided at a portion of the circulation flow path 30 between the cooler 20 and the pump 41. Further, a backup warmer 44 that heats water by a heat source (seawater or the like) may be provided at a portion of the circulation flow path 30 between the cooler 20 and the thermal storage tank 43.

The gas turbine combined power generation device 50 includes an air compressor 51, a gas turbine 52, an exhaust heat recovery boiler 53, a steam turbine 54, and a gas turbine generator 55. The air compressor 51 compresses the air flowing out of the cooler 20. The gas turbine 52 is driven by a mixed gas of compressed air discharged from the air compressor 51 and combustion gas generated by combustion of natural gas (NG). The exhaust heat recovery boiler 53 evaporates water by exchanging heat between the exhaust gas discharged from the gas turbine 52 and water. The steam turbine 54 is driven by the steam flowing out of the exhaust heat recovery boiler 53. The gas turbine generator 55 is connected to the gas turbine 52 and the steam turbine 54, and generates electric power by their rotation.

The natural gas-fired combined cycle power generation system 1 may further have a warmer 60 provided at a portion of the circulation flow path 30 between the cooler 20 and the vaporizer 10.

Here, the vaporizer 10 and the warmer 60 will be described with reference to FIG.

The vaporizer 10 has an intermediate medium evaporation unit E1, a liquefied natural gas vaporization unit E2, an intermediate medium evaporation unit E1, a liquefied natural gas vaporization unit E2, and a shell 11 capable of accommodating the intermediate medium M.

The intermediate medium evaporation unit E1 evaporates at least a part of the intermediate medium M by exchanging heat between the liquid phase intermediate medium M and the water (warm water) flowing out of the cooler 20. In the present embodiment, the intermediate medium evaporation section E1 is composed of a heat transfer tube. The intermediate medium evaporation section E1 is arranged in the lower part of the shell 11 (the position in the shell 11 where the liquid phase is immersed in the intermediate medium M). That is, the intermediate medium M in contact with the intermediate medium evaporation section E1 is heated by the water flowing in the intermediate medium evaporation section E1.

The liquefied natural gas vaporization unit E2 vaporizes at least a part of the liquefied natural gas by exchanging heat between the liquefied natural gas and the intermediate medium M of the gas phase. In the present embodiment, the liquefied natural gas vaporization unit E2 is composed of a U-shaped heat transfer tube. The liquefied natural gas vaporization unit E2 is arranged in the upper part of the shell 11 (the region in the shell 11 above the surface of the intermediate medium M of the liquid phase). That is, the liquefied natural gas flowing in the liquefied natural gas vaporization unit E2 is heated by the intermediate medium M of the gas phase in contact with the surface of the liquefied natural gas vaporization unit E2.

An entrance chamber 12 and an exit chamber 13 partitioned from each other by a partition plate 14 are connected to the shell 11. The inlet chamber 12 is connected to one end of the liquefied natural gas vaporization unit E2 so that the inside of the entrance chamber 12 and the inside of the liquefied natural gas vaporization unit E2 communicate with each other. The outlet chamber 13 is connected to the other end of the liquefied natural gas vaporization unit E2 so that the inside of the outlet chamber 13 and the inside of the liquefied natural gas vaporization unit E2 communicate with each other. That is, at least a part of the liquefied natural gas that has flowed into the liquefied natural gas vaporization section E2 from the inlet chamber 12 is heated by the intermediate medium M of the gas phase in the process of passing through the liquefied natural gas vaporization section E2. And flows into the exit chamber 13.

Further, the water inlet chamber 15 and the water outlet chamber 16 are connected to the shell 11. The water inlet chamber 15 is connected to one side of the shell 11 so that the inside of the water inlet chamber 15 and the inside of the intermediate medium evaporation portion E1 communicate with each other. The water outlet chamber 16 is connected to the other side of the shell 11 so that the inside of the water outlet chamber 16 and the inside of the intermediate medium evaporation section E1 communicate with each other. That is, the water flowing into the intermediate medium evaporation section E1 from the water inlet chamber 15 recovers cold heat from the liquid phase intermediate medium M in the process of passing through the intermediate medium evaporation section E1 and circulates through the water outlet chamber 16. It flows out to the flow path 30.

The warmer 60 is provided in a portion of the circulation flow path 30 on the upstream side of the vaporizer 10. The warmer 60 heats the natural gas flowing out of the vaporizer 10. The warmer 60 has a heating unit E3 and a casing 61 for accommodating the heating unit E3.

The heating unit E3 heats the natural gas by exchanging heat between the natural gas flowing out from the liquefied natural gas vaporizing unit E2 and the water flowing out from the cooler 20. In the present embodiment, the heating portion E3 is composed of a heat transfer tube formed in a U shape.

An inlet chamber 62 and an outlet chamber 63 partitioned by a partition plate 64 are connected to the casing 61 via a flange 65. The configuration of the entrance chamber 62 and the exit chamber 63 is the same as the configuration of the entrance chamber 12 and the exit chamber 13 connected to the shell 11. The natural gas flowing out of the outlet chamber 13 of the vaporizer 10 flows into the inlet chamber 62, is heated by the water in the casing 61 in the process of passing through the heating unit E3, and flows into the outlet chamber 63. The flange 65 is detachably connected to the casing 61. That is, the heating portion E3, the inlet chamber 62, the outlet chamber 63, and the partition plate 64 can be removed from the casing 61.

As shown in FIG. 1, the natural gas-fired combined cycle power generation system 1 has a heat quantity adjusting flow path 31. The heat quantity adjusting flow path 31 is connected to the circulation flow path 30 and bypasses the warmer 60. Therefore, the water that has flowed out of the cooler 20 and then passed through the warmer 60 and the water that has passed through the heat quantity adjusting flow path 31 flow into the intermediate medium evaporation section E1.

As described above, in the natural gas-fired combined cycle power generation system 1 of the present embodiment, heat exchange between water and liquefied natural gas is performed via an intermediate medium (propane or the like) having a freezing point lower than that of water. Therefore, the occurrence of icing in the intermediate medium evaporation section E1 is suppressed as compared with the case where water and liquefied natural gas directly exchange heat. Further, in order to prevent icing trouble, it is not necessary to use expensive brine water (ethylene glycol water or the like) as a cooling medium.

Further, a warmer 60 for heating the natural gas with the water flowing out from the cooler 20 is provided on the upstream side of the vaporizer 10. Therefore, the natural gas is heated with a simple structure as compared with the case where the natural gas flowing out from the liquefied natural gas vaporization unit E2 is heated by a heating medium different from the water flowing out from the cooler 20.

Further, in the warmer 60, the heating portion E3, the inlet chamber 62, the outlet chamber 63 and the partition plate 64 can be removed from the casing 61. Therefore, cleaning (cleaning) of the heating portion E3 and the casing 61 becomes easy.

Further, as shown in FIG. 3, the natural gas-fired combined cycle power generation system 1 may further include a cooler bypass flow path 32 and a cold heat recovery unit 45. The cooler bypass flow path 32 is connected to the circulation flow path 30 and bypasses the cooler 20. The cold heat recovery unit 45 recovers the cold heat of the water flowing out from the vaporizer 10. Examples of the cold heat recovery unit 45 include a cooling device for cooling a room or a cable pit. In this aspect, the surplus cold heat required for cooling the air in the cooler 20 is effectively recovered by the cold heat recovery unit 45.

(Second Embodiment)
Next, the natural gas-fired combined cycle power generation system 1 of the second embodiment of the present invention will be described with reference to FIGS. 4 and 5. In the second embodiment, only the parts different from the first embodiment will be described, and the description of the same structure, action and effect as in the first embodiment will be omitted.

The natural gas-fired combined cycle power generation system 1 of the present embodiment further includes a direct expansion turbine 80, an expansion turbine generator 90, a heating section bypass flow path 33, and an additional heating section E4.

The direct expansion turbine 80 is driven by the natural gas flowing out from the heating unit E3. The expansion turbine generator 90 is directly connected to the expansion turbine 80.

The heating section bypass flow path 33 is connected to the circulation flow path 30 and bypasses the heating section E3.

The additional heating unit E4 is provided in the heating unit bypass flow path 33. The additional heating unit E4 heats the natural gas by exchanging heat between the water flowing through the heating unit bypass flow path 33 and the natural gas directly flowing out of the expansion turbine 80. The additional heating portion E4 is composed of a heat transfer tube formed in a U shape. In the present embodiment, the additional heating unit E4 is housed in the casing 61. In other words, the casing 61 of the present embodiment has a shape capable of accommodating the heating portion E3 and the additional heating portion E4 together. An inlet chamber 72 and an outlet chamber 73 partitioned from each other by a partition plate 74 are further connected to the casing 61 via a flange 75. The inlet chamber 72 and the outlet chamber 73 communicate with the inside of the additional heating unit E4. The natural gas flowing out of the direct expansion turbine 80 flows into the inlet chamber 72, and then is heated by the water flowing into the casing 61 through the heating section bypass flow path 33 in the process of passing through the additional heating section E4. It flows into the exit chamber 73. The additional heating unit E4 can also be removed from the casing 61 together with the inlet chamber 72, the outlet chamber 73, and the partition plate 74. Therefore, cleaning (cleaning) of the additional heating unit E4 becomes easy.

Further, in the present embodiment, the energy of the natural gas flowing out from the heating unit E3 is recovered as electric power in the expansion turbine generator 90, so that the amount of power generation of the entire system increases.

Further, the temperature of the natural gas lowered by passing directly through the expansion turbine 80 by the water flowing out from the cooler 20 is raised instead of the dedicated heating medium for heating the natural gas flowing out from the expansion turbine 80 directly. Can be done. Specifically, although the temperature of the natural gas is lowered by directly passing through the expansion turbine 80, a part of the heat of the water flowing out from the cooler 20 is added instead of being input to the heating unit E3. Since the gas is introduced into the additional heating unit E4 through the warm portion bypass flow path 33, the natural gas flowing out directly from the expansion turbine 80 is effectively heated. Since the water has a sufficient amount of heat even after the natural gas is heated in the additional heating unit E4, the intermediate medium M is effectively heated in the intermediate medium evaporation unit E1 by the water.

It should be noted that the embodiments disclosed this time are exemplary in all respects and are not considered to be restrictive. The scope of the present invention is shown by the scope of claims rather than the description of the above-described embodiment, and further includes all modifications within the meaning and scope equivalent to the scope of claims.

For example, the heating unit E3 and the additional heating unit E4 may be housed in different casings. Also in this case, it is preferable that the water flowing out from the additional heating unit E4 is supplied to the intermediate medium evaporation unit E1.

1 Natural gas-fired combined cycle power generation system 10 Vaporizer 20 Cooler 30 Circulation flow path 32 Cooler bypass flow path 33 Heater bypass flow path 40 Pump 45 Cold heat recovery unit 50 Gas turbine Combined power generation device 52 Gas turbine 54 Steam turbine 55 Gas Turbine Generator 60 Heater 70 Heater 80 Expansion Turbine E1 Intermediate Medium Evaporator E2 Liquefied Natural Gas Vaporizer E3 Heater E4 Additional Heater M Intermediate Medium

Claims (2)

The cold heat recovered from the liquefied natural gas in the vaporizer for vaporizing the liquefied natural gas is used to cool the air supplied to the gas turbine and the gas turbine combined power generator having the gas turbine generator connected to the gas turbine. It is a natural gas-fired combined cycle power generation method to be used.
A vaporization step of vaporizing at least a part of the liquefied natural gas by heating the liquefied natural gas with water.
A cooling step in which the air supplied to the gas turbine combined power generator is cooled in the cooler by the cold heat recovered from the liquefied natural gas in the vaporization step.
A step of heating the natural gas by exchanging heat between the natural gas obtained in the vaporization step and a part of the water flowing out of the cooler in a heating section is provided.
In the vaporization step, at least of the intermediate medium is supplied to an intermediate medium having a freezing point lower than the freezing point of water in the vaporizer by supplying the heat recovered from the air by cooling the air in the cooling step. A part of the liquefied natural gas is vaporized and at least a part of the liquefied natural gas is vaporized by heating the liquefied natural gas with the intermediate medium.
A natural gas-fired combined cycle power generation method in which another part of water flowing out of the cooler is allowed to flow into the vaporizer without passing through the heating part. The natural gas-fired combined cycle power generation method according to claim 1, wherein a part of the water that has exchanged heat with the natural gas in the heating portion is merged with the other portion of the water and flows into the vaporizer.

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