Erosion shielding for a circulating fluidized bed boiler

Abstract

A method for shielding the inner surface above the shield refractory ( 4 ) of the furnace wall ( 3 ) of a circulating fluidized bed boiler from erosion caused by suspension flows, in which method a shield structure is formed on the inner surface of the boiler wall. At least a first zone ( 1 ) and a second zone ( 2 ) are formed in the shield structure, the erosion-resistance properties of which zones differ from each other. In addition the invention relates to a circulating fluidized bed boiler, which comprises a corresponding shield structure.

1 . A method for shielding the inner surface above the shield refractory of the furnace wall of a circulating fluidized bed boiler from erosion caused by suspension flows, in which method a shield structure is formed on the inner surface of the boiler wall,  
       wherein 
 at least a first zone and a second zone are formed in the shield structure, the erosion-resistance properties of which zones differ from each other.  
 
     
     
         2 . The method according to  claim 1 , wherein the shield structure is formed on the surface of the water pipe of the water wall of the boiler.  
     
     
         3 . The method according to  claim 1 , wherein the first zone is located at least partly above the second zone in the direction of the furnace wall.  
     
     
         4 . The method according to  claim 1 , wherein the first zone is less erosion-resistant than the second zone in operating conditions.  
     
     
         5 . The method according to  claim 1 , wherein the first zone and the second zone are formed of different materials.  
     
     
         6 . The method according to  claim 1 , wherein the first zone is formed of a first material and the second zone is formed by blending the first material.  
     
     
         7 . The method according to  claim 1 , wherein the second zone is formed of a first material and the first zone is formed by blending the first material.  
     
     
         8 . A circulating fluidized bed boiler, which comprises at least 
 a furnace,    a shield refractory arranged in the wall of the lower part of the furnace to shield the inner surface from the erosion caused by suspension flows, and    a shield structure, which is located at least partly above the shield refractory on the inner surface of the wall to shield the inner surface above the shield refractory from the erosion caused by suspension flows,    wherein    the shield structure comprises at least a first zone and a second zone, whose erosion-resistance properties differ from each other.    
     
     
         9 . The circulating fluidized bed boiler according to  claim 8 , wherein the shield structure is formed on the surface of the water pipe of the water wall of the boiler.  
     
     
         10 . The circulating fluidized bed boiler according to  claim 8 , wherein the first zone is located at least partly above the second zone in the direction of the furnace wall.  
     
     
         11 . The circulating fluidized bed boiler according to  claim 8 , wherein the first zone is less erosion-resistant than the second zone in operating conditions.  
     
     
         12 . The circulating fluidized bed boiler according to  claim 8 , wherein the first zone and the second zone are formed of different materials.  
     
     
         13 . The circulating fluidized bed boiler according to  claim 8 , wherein the first zone is formed of a first material and the second zone is formed by blending the first material.  
     
     
         14 . The circulating fluidized bed boiler according to  claim 8 , wherein the second zone is formed of a first material and the first zone is formed by blending the first material.