Gas turbine device and method for operating gas turbine device

A gas turbine device comprising:

• a combustor casing to which compressed air from a gas turbine compressor is guided;
• a combustor provided in the combustor casing and including a gas nozzle for injecting a gaseous fuel and an oil nozzle for ejecting an oil fuel;
• a first purge-air line configured to supply first air derived from bleed air from the combustor casing to the oil nozzle;
• and
• a second purge-air line configured to supply second air compressed by an external compressor different from the gas turbine compressor to the oil nozzle,
• wherein the gas turbine device is configured to selectively supply either the first air from the first purge-air line or the second air from the second purge-air line to the oil nozzle as purge air,
• wherein the gas turbine device further comprises a bleed-air line configured to supply the bleed air from the combustor casing as cooling air to a stationary member of the gas turbine device, and
• wherein the first purge-air line branches from the bleed-air line.

A method for operating a gas turbine device including a combustor casing to which compressed air from a gas turbine compressor is guided, a combustor provided in the combustor casing and including a gas nozzle for injecting a gaseous fuel and an oil nozzle for ejecting an oil fuel, a first purge-air line configured to supply first air derived from bleed air from the combustor casing to the oil nozzle, and a second purge-air line configured to supply second air compressed by an external compressor different from the gas turbine compressor to the oil nozzle, the method comprising:

• a step of selectively supplying either the first air from the first purge-air line or the second air from the second purge-air line to the oil nozzle as purge air,
• wherein when switching from an oil firing operation of the gas turbine device in which the oil fuel injected from the oil nozzle is combusted to a gas firing operation of the gas turbine device in which the gaseous fuel injected from the gas nozzle is combusted, the second air from the second purge-air line is supplied to the oil nozzle as the purge air, and
• wherein during the gas firing operation after the switching from the oil firing operation to the gas firing operation of the gas turbine device, the supply of the second air from the second purge-air line to the oil nozzle is stopped and the supply of the first air from the first purge-air line to the oil nozzle is started.