Porous burner having a flame barrier
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.