Boiler and a superheater, as well as a method

Abstract

A boiler and a method in a boiler producing thermal energy, the method including: combustion or fuel and combustion air in the furnace of the boiler, delimited by walls; receiving of thermal energy by a steam superheater placed on the wall of the furnace and including at least one heat exchange surface, and supplying of gas or a gas mixture to the front of said heat exchange surface to form a barrier layer for protecting the heat exchange surface from flue gases developed in connection with the combustion. At least one supply device is provided in the superheater or in the direct vicinity of the superheater, to supply gas or a gas mixture to the front of said heat exchange surface to form a barrier layer to protect the heat exchange surface from the flue gases in the boiler.

1 . A boiler for producing thermal energy, the boiler comprising:
 a furnace limited by walls;   at least one steam superheater placed on a wall of the furnace and having at least one heat exchange surface for receiving thermal energy and;   at least one supply device for supplying gas or a gas mixture to the front of said heat exchange surface to form a barrier layer to protect the heat exchange surface from the flue gases in the boiler.   
     
     
         2 . The boiler according to  claim 1 , wherein, for receiving thermal energy, the superheater has a direct line of sight to the flame produced in connection with the combustion of fuel. 
     
     
         3 . The boiler according to  claim 1 , wherein the superheater is placed on a wall at the bottom of the furnace. 
     
     
         4 . The boiler according to  claim 1 , wherein the boiler further comprises:
 devices for supplying fuel to the furnace for combustion;   devices for supplying combustion gas to the furnace for combustion;   one or more flue gas ducts placed in the upper part of the furnace and discharging the flue gases formed during the combustion from the furnace.   
     
     
         5 . The boiler according to  claim 1 , wherein the boiler is a boiler based on fluidized bed combustion, a soda recovery boiler, or a boiler based on combustion on a grate. 
     
     
         6 . The boiler according to  claim 1 , wherein said supply device comprises an orifice, a pipe or a duct, or a nozzle, fitted in the superheater or in the direct vicinity of the superheater. 
     
     
         7 . The boiler according to  claim 1 , wherein the superheater comprises pipes connected to each other, inside which the steam flows. 
     
     
         8 . The boiler according to  claim 1 , wherein the boiler comprises a supply device matrix comprising several said supply devices provided to supply gas or a gas mixture to the front of said heat exchange surface, to form a uniform barrier layer. 
     
     
         9 . The boiler according to  claim 8 , wherein the supply device matrix comprises two or more rows, each having two or more supply devices. 
     
     
         10 . The boiler according to  claim 8 , wherein the supply device matrix is placed in the area limited by the superheater. 
     
     
         11 . The boiler according to  claim 10 , wherein the supply device matrix is further placed in the direct vicinity of the superheater. 
     
     
         12 . The boiler according to  claim 8 , wherein each supply device comprises a nozzle orifice, a pipe or a duct, or a nozzle, fitted in the superheater. 
     
     
         13 . A boiler superheater provided on the wall of a boiler for producing thermal energy, the wall delimiting the furnace of the boiler, and the superheater comprising at least one heat exchange surface for receiving thermal energy, wherein at least one supply device is provided in the superheater, for supplying gas or a gas mixture to the front of said heat exchange surface, to form a barrier layer to protect the heat exchange surface from flue gases in the boiler. 
     
     
         14 . The superheater according to  claim 13 , wherein a supply device matrix is provided in the area defined by the superheater, the matrix comprising several said supply devices provided to supply gas or a gas mixture to the front of said heat exchange surface, to form a uniform bather layer. 
     
     
         15 . The superheater according to  claim 14 , wherein each supply device comprises a nozzle orifice, a pipe or a duct, or a nozzle, fitted in the superheater. 
     
     
         16 . A method in a boiler producing thermal energy, the method comprising:
 combustion of fuel and combustion air in the furnace of the boiler, delimited by walls;   receiving of thermal energy by a steam superheater placed on a wall of the furnace and having at least one heat exchange surface; and   supplying of gas or a gas mixture to the front of the heat exchange surface, to form a barrier layer for protecting the heat exchange surface from flue gases developed in connection with the combustion.   
     
     
         17 . The method according to  claim 16 , wherein the gas or gas mixture is air or a corrosion inhibitor. 
     
     
         18 . The method according to  claim 16 , wherein the method further comprises:
 supplying of gas or gas mixture from several different locations into the area delimited by the superheater, to the front of said heat exchange surface, to form a uniform barrier layer.   
     
     
         19 . The method according to  claim 16 , wherein the method further comprises:
 supplying of gas or gas mixture to the barrier layer by using at least one gas supply device placed in the superheater or in the direct vicinity of the superheater, or by using a supply device matrix comprising several said supply devices and placed in the area delimited by the superheater.   
     
     
         20 . The method according to  claim 17 , wherein the corrosion inhibitor is sulphur dioxide or sulphide.