Steam boiler comprising a radiation element

Abstract

A steam boiler has at least one water and/or steam conveying element and at least one radiation element, which is an un-cooled element, arranged in the flow of hot flue gases, such that it is convectively heated by the flue gases. The radiation element is located at a pre-determined distance from the at least one water and/or steam conveying element, wherein the pre-determined distance is arranged such that the flow of hot flue gases between the radiation element and the water and/or steam conveying element is unhindered, and such that the water and/or steam conveying element is heated by heat radiation from the radiation element.

1 . A steam boiler comprising:
 at least one water and/or steam conveying element heated by the hot flue gases in the boiler; and   at least one radiation element, the at least one radiation element being an un-cooled element arranged in the flow of hot flue gases such that it is convectively heated by the flue gases, wherein the radiation element is located at a pre-determined distance from said at least one water and/or steam conveying element, the pre-determined distance being arranged such that the flow of hot flue gases between the at least one radiation element and the at least one water and/or steam conveying element is unhindered, and such that the at least one water and/or steam conveying element is heated by heat radiation from said at least one radiation element.   
     
     
         2 . The steam boiler according to  claim 1 , wherein said at least one radiation element is arranged such that the flow of the hot flue gases can pass said at least one radiation element essentially without changing flow direction. 
     
     
         3 . The steam boiler according to  claim 1 , wherein the at least one radiation element is arranged in the flow of flue gases such that the entire at least one radiation element is exposed to the flow of flue gases. 
     
     
         4 . The steam boiler according to  claim 1 , wherein the at least one water and/or steam conveying element is at least one steam conveying superheater tube. 
     
     
         5 . The steam boiler according to  claim 1 , wherein the surface area of the at least one radiation element is at least 3 percent of the area of said at least one water and/or steam conveying element that is directly exposed to the flue gases. 
     
     
         6 . The steam boiler according to  claim 1 , wherein the radiation element extends essentially parallel to the flow direction of the flue gases. 
     
     
         7 . The steam boiler according to  claim 1 , wherein said radiation element is a sheet having two side surfaces and a circumferential edge, wherein the at least one radiation element is arranged such that a normal to one of its side surfaces is perpendicular to the flow direction of the hot flue gases and such that an edge portion of the sheet faces the flow of hot flue gases. 
     
     
         8 . The steam boiler according to  claim 1 , wherein said at least one radiation element is a corrugated sheet. 
     
     
         9 . The steam boiler according to  claim 1 , wherein the at least one radiation element is an elongated rod element, wherein the at least one radiation element is arranged such that its radial axis R is perpendicular to the flow direction of the flue gases. 
     
     
         10 . The steam boiler according to  claim 9 , wherein the at least one radiation element has a circular cross section. 
     
     
         11 . The steam boiler according to  claim 1 , wherein the at least one radiation element is formed by an alloy which is based on Fe or Ni and contains Al and which, when subjected to heat in an oxygen-containing atmosphere, forms a protective alumina layer on the outer surface thereof. 
     
     
         12 . The steam boiler according to  claim 1 , wherein the at least one radiation element is flexibly attached to an un-cooled surface of the boiler. 
     
     
         13 . The steam boiler according to  claim 1 , wherein the at least one radiation element is flexibly attached to the boiler such that at least one end of the radiation element is free to expand or contract. 
     
     
         14 . The steam boiler according to  claim 1 , wherein the at least one radiation element is arranged such that it flexibly hangs from the at least one water and/or steam conveying element. 
     
     
         15 . The steam boiler according to  claim 14 , wherein the at least one radiation element includes hooks or rings for hanging the at least one radiation element on the at least one water and/or steam conveying element. 
     
     
         16 . The steam boiler according to  claim 5 , wherein the surface area of the at least one radiation element is at least 10 percent of the area of the at least one water and/or steam conveying element that is directly exposed to the flue gases. 
     
     
         17 . The steam boiler according to  claim 9 , wherein the at least one radiation element has a rectangular cross-section.