JPH11270347A - Gas turbine combined power generation device using LNG - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system to carry out totally highly efficient power generation in a gas turbine generating set using LNG as fuel. SOLUTION: This generating set boosts LNG by a booster pump 2, heats it by exhaust gas 22 of a waste heat boiler 9 and bleed air 34 of a steam turbine 8 and recovers energy by an expansion turbine 5. In the meantime, a turbine blade is cooled down by a cooling piping 14 of LNG and high temperature working gas can be supplied to a gas turbine 6. Consequently, it is possible to improve overall power generating efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a gas turbine combined power generation device using LNG (liquefied natural gas). BACKGROUND ART A gas turbine combined power generation device is a power generation device that recovers heat of an exhaust gas of a gas turbine by an exhaust heat boiler and generates power with high efficiency in combination with a steam turbine.

[0002]

2. Description of the Related Art Since LNG is liquefied at -162 ° C. under normal pressure, it is liquefied, transported by tanker, and stored in an LNG tank. Conventionally, in a gas turbine power generator using LNG as a fuel, LNG is heated and vaporized using a large amount of seawater, or is heated and vaporized by a heat source obtained by burning a part of LNG. , And is generally used as a fuel for gas turbines. Further, in order to effectively use the cold heat of LNG, there is a technique of utilizing the cold heat of a cryogenic air separation device or of using it as a cooling source of compressed air. Further, there is a plant provided with a low-boiling point turbine that effectively uses cold heat in a combined cycle, and a technique of recovering energy by an expansion turbine by increasing the pressure of LNG.

For example, Japanese Patent Application Laid-Open No. 56-81207 discloses an LNG cold-heat power generation system including a gas turbine, a steam turbine, and a boiler that generates steam by exhausting a gas turbine in a system including a low-boiling medium turbine. , LNG is heated using a low-boiling medium, intake air of a gas turbine, and the like.
Japanese Patent Application Laid-Open No. 52-9744 discloses a pressurizing pump for pumping LNG from a storage tank and pressurizing the same, a heat exchanger for heating the pressurized liquefied gas, and a high-pressure and high-temperature natural gas heated by the heat exchanger. 1 shows an expansion turbine and a natural gas combustion boiler using natural gas discharged from the expansion turbine as a heat source.

Further, Japanese Patent Application Laid-Open No. 2-275022 describes a technique for recovering gas energy from a gas pressure source such as vaporized LNG using an expansion turbine.

[0005]

Conventionally, in a combined power generation apparatus using LNG as fuel and combining a gas turbine and a steam turbine, a large amount of seawater or air is used to wastefully discharge the cold energy of LNG. Was. As a technique for avoiding this, there is a technique of adding an expensive device such as a low boiling point turbine to recover cold heat, or a technique of pressurizing LNG to a high pressure to raise the temperature to recover it with an expansion turbine.

According to the present invention, LNG is pressurized to a high pressure, the high-pressure LNG is heated and vaporized using low-temperature exhaust gas (120 to 180 ° C.) of a waste heat boiler, and the temperature is raised using steam. It is an object of the present invention to provide a system that collects energy by using the system and generates power efficiently with high efficiency.
Another object of the present invention is to efficiently cool the blades of a gas turbine and improve the thermal efficiency of the gas turbine.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and the technical means thereof is LNG.
In a gas turbine power generation system using as fuel, a booster pump that boosts LNG to high pressure LNG, a heat exchanger that heats high pressure LNG with exhaust gas from a waste heat boiler and steam turbine extraction, and operates the heated high pressure LNG A gas turbine combined power generation device using LNG, comprising: an expansion turbine that recovers electric power as a fluid.

In this power generation device, by providing a cooling path for using a part of the high-pressure LNG for cooling the gas turbine blades, the cold heat is effectively used for cooling, and the vaporized natural gas is discharged into the gas turbine. The fuel is combusted by the residual air in the gas turbine and energy is recovered. According to the present invention, by generating and generating power by expanding and vaporizing with an expansion turbine using high-pressure and high-temperature LNG, the effective energy of the LNG can be efficiently recovered as electric power, and the power generation efficiency of the entire system can be improved. Further, the low-temperature waste heat of the waste heat boiler exhaust gas can be effectively used.

Further, since the cooling capability of the gas turbine blades can be improved, the temperature of the combustion gas introduced into the gas turbine can be increased, and the effect of improving the thermal efficiency of the gas turbine can be obtained.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an LN according to an embodiment of the present invention.
4 is a flow sheet of a gas turbine combined power generation device using G as fuel. LNG (−162 ° C.) guided from the LNG storage tank 1 to the boosting pump 2 is pressurized by the boosting pump 2 to 30 to 100 kg / cm ² G. The pressurized LNG is heated by the exhaust gas 22 of the boiler 9 in the vaporizer 3 and vaporized, and is heated to about 100 ° C. The exhaust gas 22 is a part of the exhaust gas 21 of the waste heat boiler 9
The flow is divided by Conventionally, thermal energy that has been released into the atmosphere from the chimney 11 as the exhaust gas 21 is recovered by the vaporizer 3.

Thereafter, the natural gas is heated by the heater 4 to about 200 ° C. by bleed air 34 from the intermediate stage of the steam turbine 8. The natural gas 16 exiting the heater 4 is decompressed to 10 kg / cm ² by the expansion turbine 5, and at this time, energy is recovered as electric power. The natural gas 17 discharged from the outlet of the expansion turbine 5 has a temperature of around 100 ° C. The natural gas 17 is mixed with the compressed air generated by the air compressor 7 in a combustor (not shown), burns, and supplied to the gas turbine 6 as a high-temperature gas. The air compressor 7 takes in outside air from the air inlet 13 and
Compress to cm ² . When the natural gas is operated at the same air ratio as the conventional gas turbine 6, the temperature of the combustion gas introduced into the gas turbine rises, causing a problem of damaging the turbine blades. Therefore, part of the LNG at the outlet of the booster pump 2 is used for cooling the turbine blades through the cooling pipe 14. The amount is adjusted by the control valve 15. The cooling effect of the gas turbine blades can be enhanced by cooling with the low-temperature LNG, and even if the gas turbine is operated by generating high-temperature combustion gas, it is possible to prevent the turbine blades from being melted and damaged.

[0012] The turbine blade cooling by LNG is used for the first (or first and second) stage having a high temperature among the third to fourth stages of the gas turbine blades, and the LNG whose blades have been cooled is combusted downstream of the gas turbine. I do. Cooling of the third and fourth stage blades uses air as in the conventional case. The exhaust gas 18 of the gas turbine is supplied to the waste heat boiler 9. The waste heat boiler 9 heats the feed water 31 to generate steam 32, and the steam 32 drives the steam turbine 8 and is discharged as exhaust 33. The exhaust gas 33 is cooled by a condenser (not shown) and circulated to the water supply 31. Medium-pressure steam is extracted from the intermediate stage of the steam turbine 8, and the natural gas is heated by the heater 4 as bleed air 34, and the exhaust gas 35 exiting the heater 4 passes through the vaporizer 3 and exits the vaporizer 3. The exhaust gas 23 is discharged into the atmosphere from the chimney 11 together with the exhaust gas 22 from the waste heat boiler.

The gas turbine and the steam turbine are provided with a generator 1
2 to generate electric power.

[0014]

According to the present invention, LNG is pressurized, heated by the energy of the exhaust gas of the waste heat boiler and the steam turbine bleed, and the energy is recovered by the expansion turbine. Since high-temperature working gas can be supplied to the gas turbine by performing effective blade cooling, an excellent effect that the entire power generation efficiency can be improved is achieved.

[Brief description of the drawings]

FIG. 1 is a flow sheet of a power generator according to the present invention.

[Explanation of symbols]

 1 Liquefied Natural Gas Storage Tank 2 Boost Pump 3 Vaporizer 4 Heater 5 Expansion Turbine 6 Gas Turbine 7 Air Compressor 8 Steam Turbine 9 Waste Heat Boiler 10 Damper 11 Chimney 12 Generator 13 Air Inlet 14 Cooling Pipe 15 Control Valve 16 Natural Gas 17 Natural gas 18 Gas turbine exhaust gas 21 Exhaust gas 22 Waste heat boiler exhaust gas 23 Exhaust gas 31 Water supply 32 Steam 33 Exhaust 34 Extraction 35 Exhaust

Claims (2)

[Claims] 1. A gas turbine power generator using LNG as fuel, comprising: a booster pump for boosting LNG to high pressure LNG; a heat exchange device for heating the high pressure LNG with exhaust gas from a waste heat boiler and steam turbine extraction. A gas turbine combined power generation device using LNG, comprising: an expansion turbine that recovers power using the high-pressure LNG as a working fluid. 2. The gas turbine combined power generation device using LNG according to claim 1, wherein a cooling path is provided for using a part of the high-pressure LNG for cooling the gas turbine blades.