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

Abstract

A flue gas air preheating apparatus for combustion air in a boiler of a power plant. An air pipe is placed in a flue gas duct. An air guide sleeve is provided at an initial end of the air pipe at least partly inside the air pipe. The air guide sleeve is made of a poorly heat conductive material and is designed to diminish turbulence in air flow and has an inflow end and a second end placed inside the air pipe. The shaping of the second end is designed to diminish turbulence in the air flow. The air guide sleeve includes splits or notches that become wider towards the second end. A method and a corrosion shield.

1 - 13 . (canceled) 
     
     
         14 . 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.   
     
     
         15 . The flue gas air preheating apparatus according to  claim 14 , wherein the shaping of the second end that diminishes turbulence in the air flow is provided within a length less than ⅓ of the length of the air guide sleeve. 
     
     
         16 . The flue gas air preheating apparatus according to  claim 14 , wherein at the second end of the air guide sleeve, the wall of the air guide sleeve becomes thinner towards the second end. 
     
     
         17 . The flue gas air preheating apparatus according to  claim 14 , wherein the air guide sleeve is fitted to guide combustion air to be heated in contact with an inner surface of the air pipe at a distance from the initial end of the air pipe, the distance being at least three times a diameter of the air pipe. 
     
     
         18 . The flue gas air preheating apparatus according  claim 14 , wherein the air guide sleeve is made at least partly of a polymeric material. 
     
     
         19 . The flue gas air preheating apparatus according  claim 18 , wherein the air guide sleeve is made of polyphenyl sulphide. 
     
     
         20 . The flue gas air preheating apparatus according to  claim 14 , further comprising:
 a protective sleeve surrounding the air pipe at the initial end of the air pipe.   
     
     
         21 . The flue gas air preheating apparatus according to  claim 14 , further comprising:
 a thermal insulation layer surrounding the flue gas duct, wherein the air guide sleeve extends through the insulation layer and the air pipe does not extend through the insulation layer.   
     
     
         22 . 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. 
     
     
         23 . The air guide sleeve according to  claim 22 , wherein the shaping of the second end that diminishes turbulence in the air flow is provided within a length less than ⅓ of the length of the air guide sleeve. 
     
     
         24 . The air guide sleeve according to  claim 22 , wherein at the second end of the air guide sleeve, the wall of the air guide sleeve becomes thinner towards the second end.