To decrease replacement frequencies of a filter for preventing a steam cooling passage from being clogged with solids dropped from a main steam system pipe, in a recovering-type steam cooled gas turbine.
A gas turbine system is constituted of a gas turbine 1, a compressor 3 and a generator 4, steam extracted from a high-pressure turbine 6 is allowed to flow in moving blade and stationary blade cooling passage 21, 22 of the gas turbine 1 through a dust protective filter 10 and returned to a middle- pressure turbine 6-2 after cooling blades. Steam from an exhaust heat recovering boiler 5 is allowed to flow in a combustion cooling passage 23 through the dust protective filter 9 and allowed to flow in the middle-pressure turbine 6-2 after cooling the passage. The mesh range of the dust protective filters 9, 10 is in the range of 100 μm to 1000 μm, the meshes allow fine particles pass to flow but removes solids to be generated by dropping of scale of a main steam system, and therefore, clogging of the cooling passages 21 to 23 caused by solids is prevented, and replacement frequencies of the dust protective filter are decreased, and the long-time use is made possible.
