Porous burner having a flame barrier

Abstract

A porous burner has a mixing space for premixing reducing agent and oxidizing agent, and an adjoining combustion space filled with a porous material. A flame barrier is arranged between the mixing space and the combustion space. The flame barrier is made from a porous material with a material porosity of less than 60%. This material has a density of at least 1300 kg/m 3 . The preferred use of a porous burner configured in this way lies in the combustion of hydrogen or hydrogen-rich gas.

1 . A porous burner comprising: 
 a mixing space for mixing reducing agent and oxidizing agent;    an adjoining combustion space filled with a first porous material; and    a flame barrier with holes being arranged between the mixing space and the combustion space, the flame barrier including a second porous material with a material porosity of less than 60%, the second porous material having a density of greater than 1300 kg/m 3 .    
     
     
         2 . The porous burner as recited in  claim 1  wherein the holes have a diameter of less than 0.8 mm and a sum of cross sections of the holes amounts to less than 5% of a surface area of the flame barrier.  
     
     
         3 . The porous burner as recited in  claim 2  wherein the holes have a diameter of 0.5 mm.  
     
     
         4 . The porous burner as recited in  claim 1  wherein the sum amounts to between 1% and 4% of the surface area.  
     
     
         5 . The porous burner as recited in  claim 1  wherein the second porous material has a density of between 1500 kg/m 3  and 2000 kg/m 3 .  
     
     
         6 . The porous burner as recited in  claim 5  wherein the second porous material has a density of 1750 kg/m 3 .  
     
     
         7 . The porous burner as recited in  claim 1  wherein the second porous material has a proportion by mass of fibrous constituents of less than 30%.  
     
     
         8 . The porous burner as recited in  claim 7  wherein the second porous material has a proportion by mass of fibrous constituents of less than 15%.  
     
     
         9 . The porous burner as recited in  claim 1  wherein the second porous material includes a mixture of Al 2 O 3  and SiO 2 .  
     
     
         10 . The porous burner as recited in  claim 9  wherein the mixture includes 80% Al 2 O 3  and 20% SiO 2  based on mass.  
     
     
         11 . The porous burner as recited in  claim 1  wherein the first and second porous materials are different.  
     
     
         12 . A method for burning comprising: 
 burning a mixture of an oxidizing agent and a reducing agent using the porous burner as recited in  claim 1 , the reducing agent containing at least 75% by volume of hydrogen.    
     
     
         13 . The method as recited in  claim 12  wherein the oxidizing agent is air.  
     
     
         14 . The method as recited in  claim 1  wherein the reducing agent includes more than 90% by volume of hydrogen.  
     
     
         15 . A method for burning comprising: 
 burning, in a fuel cell system, a mixture of air and hydrogen or hydrogen-rich gas using the porous burner as recited in  claim 1  with a hydrogen content of more than 90% by volume in a fuel cell system.    
     
     
         16 . The method as recited in  claim 15  wherein the porous burner burns exhaust gases from a fuel cell in the fuel cell system.