Steam Generator

Abstract

A steam generator of a technical plant, in particular a power plant, comprising a heating gas passage enclosed by a gas-tight enclosing wall, wherein the heating gas passage has a number of heating surfaces through which a flow medium can flow, is to ensure especially reliable cleaning of the heating gas flowing off from the heating gas passage at an especially low design and production cost. To this end, provision is made according to the invention for at least one of the heating surfaces to be at least partly provided with a catalytic coating on its side facing the heating gas.

1 .- 10 . (canceled) 
     
     
         11 . A steam generator of a power plant, having a heating gas passage enclosed by a gas-tight enclosing wall, comprising:
 a plurality of heating surfaces through which a flow medium flows, wherein the heating surfaces are evaporator heating surfaces or economizer heating surfaces assigned to an economizer; and   a catalytic coating arranged on a face of at least one of the heating surfaces facing the heating gas.   
     
     
         12 . The steam generator as claimed in  claim 11 , wherein the coating applied to the respective heating surface catalyzes or brings about a conversion or decomposition of pollutants present in the heating gas. 
     
     
         13 . The steam generator as claimed in  claim 12 , wherein the coating applied to the respective heating surface catalyzes or brings about a conversion or decomposition of nitrogen oxides and/or carbon oxides. 
     
     
         14 . The steam generator as claimed in  claim 13 , further comprising an injection device for a reduction agent arranged such that during the operation of the steam generator the heating gas, decomposed following the injection with the reduction agent, flows over the respective catalytic coated heating surface. 
     
     
         15 . The steam generator as claimed in  claim 14 , wherein the reduction agent is a liquid containing ammonia. 
     
     
         16 . The steam generator as claimed in  claim 15 , wherein the catalytic surface coating is formed by nanoparticles applied to the base material of the respective heating surface, the catalytic surface coating material is selected from the group consisting of: titanium oxide, vanadium pentoxide, tungsten oxide, a zeolite material and combinations thereof. 
     
     
         17 . The steam generator as claimed in  claim 16 , wherein the respective catalytic coated heating surface is a wall heating surface integrated into the enclosing wall. 
     
     
         18 . The steam generator as claimed in  claim 17 , wherein the respective catalytic coated heating surface is a platen heating surface, arranged within or projecting into the heating gas passage. 
     
     
         19 . The steam generator as claimed in  claim 18 , wherein the respective catalytic coated heating surface is arranged in an area in which the heating gas flowing past has a temperature of between approximately 3000 C and 4000 C at rated load operation of the steam generator. 
     
     
         20 . The steam generator as claimed in  claim 19 , wherein the steam generator is a horizontal type steam generator. 
     
     
         21 . The steam generator as claimed in  claim 20 , wherein the horizontal type steam generator is a waste-heat steam generator with a horizontal gas passage through which the heating gas flows in an essentially horizontal direction. 
     
     
         22 . The steam generator as claimed in  claim 19 , wherein
 the steam generator is of the two-passage type with fossil fuel firing, with a first vertical gas passage through which the heating gas flows from bottom to top during operation, the heating gas end connected via a horizontal gas passage to a second vertical gas passage through which the heating gas flows from top to bottom,   the respective catalytic coated heating surface is a superheater heating surface, or an economizer heating surface, arranged in the area of the second vertical gas passage.   
     
     
         23 . The steam generator as claimed in  claim 22 , wherein the respective catalytic coated heating surface is part of an air preheater arranged at an outlet end in the heating gas passage.