Method and apparatus for achieving a high efficiency in an open gas-turbine (combi) process

Abstract

Method and apparatus for achieving high efficiency in an open gas-turbine process, in which a supercharger compresses air, which is burned together with a fuel in a first combustion chamber, which is followed by a first turbine, a second combustion chamber, a second turbine, and a preheating heat exchanger, in which primary bleed water vapor coming from the secondary process, or a mixture of the aforementioned water vapor and air coming from the supercharger are preheated. From the heat exchanger the combustion gases go to a waste-heat boiler, in which the secondary-process feed water is vaporized. The combustion gases are expanded in the second turbine to a pressure 0.5 bar lower than that of the surrounding atmospheric pressure. The remaining combustion gases are compressed by a combustion-gas supercharger to the surrounding atmospheric pressure. After the low-pressure turbine the water vapor is condensed in a condenser into water, which is compressed by a pump to a maximum pressure and is preheated and vaporized in the waste-heat boiler. After the waste-heat boiler the water vapor goes to a combined high/medium-pressure turbine, from which a secondary-process primary bleed is taken, which is injected into the gas-turbine process after the preheating heat exchange after the supercharger and/or at the latest to the start of the blades of the first turbine.

Description

FIELD OF INVENTION[0001]The invention relates to a method and apparatus for achieving a high efficiency in an open gas-turbine (combi) process.BACKGROUND OF INVENTION[0002]In existing gas-turbine combi processes, a supercharger compresses air, which is burned with fuel in a combustion chamber, which is followed by a turbine and a waste-heat boiler, in which water of the secondary-process circulation is vaporized. In the secondary-process circulation there is normally a vapor process, which, in the newest large plants, uses reheating of the water vapor. In the secondary process, after a low-pressure turbine, the water vapor condenses in a condenser into water, which is compressed by a pump to a maximum pressure, and preheated and vaporized in the waste-heat boiler. After the waste-heat boiler, the water vapor goes to the steam turbines of the process circulation.[0003]Using natural gas as the fuel, electricity is nowadays generally produced in a combined gas-turbine-steam power-plant...

AI Technical Summary

Benefits of technology

[0019]The 0.5 bar referred to in the claims is not an optimum point and expansion taking place to about 0.2 bar, shown in Table 1, will lead to a greater efficiency. Similarly, the water vapor arising in combustion in an open (or closed) gas-turbine process or STIG process condenses into liquid at atmospheric pressure. In the process according to the invention, the water vapor arising in combustion condenses into liquid at a pressure lower than atmospheric pressure, so that the energy loss is smaller.

Problems solved by technology

In existing combi processes incorporating two combustion chambers, a higher efficiency is not achieved.

The reason for this is not easy to determine, but closer investigation of the matter shows that the energy loss of the waste-heat boiler is great, because the exhaust temperature of the combustion gases after the second combustion chamber is high.

In addition, this US patent in question does not have a steam-turbine process.

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