Method for supplying combustion air to a flue gas air preheater, a preheating apparatus, and an air guide sleeve

A flue gas air preheating apparatus for combustion air in a boiler of a power plant, the flue gas air preheating apparatus comprising:

• an air pipe placed in a flue gas duct;
• and
• an air guide sleeve provided at an initial end of the air pipe at least partly inside the air pipe, the air guide sleeve being made of a poorly heat conductive material and having an inflow end and a second end placed inside the air pipe, wherein a shaping of the second end is designed to diminish turbulence in an air flow such that a portion of a wall of the air guide sleeve on a surface area limited by an outer circumference of the air pipe decreases towards the second end such that the second end of the air guide sleeve comprises splits or notches that become wider towards the second end.

An air guide sleeve for an air pipe in a flue gas air preheater for combustion air in a boiler of a power plant, the air guide sleeve being made of a poorly heat conductive material and arranged to be fitted inside an air pipe, having an inflow end and a second end arranged to be placed inside the air pipe, and arranged to guide combustion air to be heated into the air pipe, at a distance from a wall of the flue gas duct, wherein a shaping of the second end is designed to diminish turbulence in an air flow such that a portion of a wall of the air guide sleeve on a surface area limited by an outer circumference of the air pipe decreases towards the second end such that the second end of the air guide sleeve comprises splits or notches which become wider towards the second end.