PURPOSE: To improve energy efficiency by operating a gas turbine while burning gas for combustion at a high temperature, thereby driving a generator etc., and mixing exhaust gas in a gas turbine with atmosphere while carrying out drying step in painting, etc.

CONSTITUTION: Air is boosted by an air compressor 1a and introduced into a combustion furnace. On the other hand, fuel butane (liquid) is evaporated by the steam generated from an evaporator 2, and fed to the combustion furnace 1b. The butane and the air are burnt in the combustion furnace 1b, and fed to a gas turbine 1c as a high temperature gas 1j. The rotational energy generated in the gas turbine 1c causes the rotation of a generator 1d to obtain electricity. The high temperature gas introduced into the gas turbine 1c is recovered as a hot gas 5 in the exhaust gas. Air is intaken by an air blower 3, mixed with the hot gas 5 in the exhaust gas by a mixing device 5, and fed to a drying device in the next step as a drying gas 6.