Mixing of recycle gas with fuel gas to a burner

1. Burner for a catalytic reactor comprising:

a central oxidizer supply tube for providing oxidant flow to a combustion zone of the reactor with a stationary swirler element, having an internal portion and an external portion, an oxidant inlet and an oxidant nozzle tip;

an outer concentric fuel supply tube for providing fuel flow to the combustion zone with an inner side, an outer side, a fuel inlet and a fuel nozzle tip concentric with and proximate the oxidant nozzle tip; and

a recycle gas duct arranged within the fuel supply tube, the recycle gas duct being further arranged within a space between the central oxidizer supply tube and the outer concentric fuel supply tube, and wherein said recycle gas duct has an inlet and a recycle gas nozzle tip the recycle gas nozzle tip comprising an inner recycle gas nozzle tip and an outer recycle gas nozzle tip, wherein the inner recycle gas nozzle tip is between the oxidizer supply tube and the outer recycle gas nozzle tip, the recycle gas duct allowing recycle gas to flow in between the central oxidizer supply tube and the outer concentric fuel supply tube,

wherein the recycle gas duct is arranged so the inner recycle gas nozzle tip has a distance X from the outer side of the oxidizer supply tube, and the outer recycle gas nozzle tip has a distance Y from the inner side of the fuel supply tube, and

where X is large enough to provide fuel flow passage between the outer side of the oxidizer supply tube and the inner recycle gas nozzle tip and Y is large enough to provide fuel flow passage between the inner side of the fuel supply tube and the outer recycle gas nozzle tip,

and wherein the oxidant nozzle tip, the fuel nozzle tip, and the recycle gas nozzle tip are curved in direction toward the central axis of the burner such that the fluid ejected from the nozzles is directed toward the central axis of the burner,

and wherein said recycle gas duct is an annular duct comprising two concentric recycle gas tubes, an inner recycle gas tube with the inner recycle gas nozzle tip and an outer recycle gas tube with the outer recycle gas nozzle tip,

and wherein the recycle pas nozzle tip is upstream of the oxidant nozzle tip and the fuel nozzle tip, and the oxidant nozzle tip is upstream of the fuel nozzle tip.

2. Burner according to claim 1 , wherein the distance from the outer side of the oxidizer supply tube and the lower part of the inner recycle gas tube is at least X and the distance from the inner side of the fuel supply tube and the lower part of the outer recycle gas tube is at least Y.

3. Burner according to claim 1 , wherein X is at least 1 mm and Y is at least 1 mm.

4. Burner according to claim 1 , wherein the recycle gas nozzle tips are arranged in a distance L up-stream with relation to the fuel flow direction from the oxidant nozzle tip and the fuel nozzle tip.

5. Burner according to claim 4 , wherein the distance between the inner recycle gas nozzle tip and the outer recycle gas nozzle tip is Z, and the distance L is in the following range: 0<L<(X+Y+Z)×20.

6. Burner according to claim 4 , wherein the distance L is large enough to ensure partial mixing of the recycle gas and the fuel.

7. Burner according to claim 4 , wherein the distance L is large enough to achieve more than 90% mixture of the recycle gas with the fuel before the fuel and the recycle gas passes the fuel nozzle tip and reaches a combustion zone of the catalytic reactor.

8. Burner according to claim 1 , wherein the fuel is a gaseous hydrocarbon and the recycle gas is a recycle gas from a Fisher Tropsh synthesis.

9. A method for burning a fuel in a catalytic reactor comprising the steps of:

providing a first stream comprising oxidant to an oxidant inlet of a central oxidizer supply tube comprising an inner and an outer side;

providing a second stream comprising fuel to a fuel inlet of an outer fuel supply tube concentric to the oxidizer supply tube and comprising an inner and an outer side;

providing a third stream comprising recycle gas to a recycle gas inlet of a recycle gas duct arranged within the fuel supply tube;

flowing the first stream from the oxidant inlet, through the central oxidizer supply tube to an oxidant nozzle tip, inducing a swirl to the first stream by means of a stationary swirler element mounted in the central oxidizer supply tube and exiting the first stream from the oxidizer supply tube via the oxidant nozzle tip opening;

flowing the second stream from the fuel inlet, through the outer fuel supply tube and exiting the second stream from the outer fuel supply tube via a fuel outlet between the oxidant nozzle tip and a fuel nozzle tip of the outer fuel supply tube; and

flowing the third stream from the recycle gas inlet, through the recycle gas duct and exiting the third stream within the flow of the second stream at a recycle gas nozzle tip within the fuel nozzle tip and outside the oxidant nozzle tip,

wherein the recycle gas nozzle tip comprising an inner recycle gas nozzle tip and an outer recycle gas nozzle tip, wherein the inner recycle gas nozzle tip is between the oxidizer supply tube and the outer recycle gas nozzle tip,

wherein the recycle gas nozzle tip is upstream of the oxidant nozzle tip and the fuel nozzle tip, and the oxidant nozzle tip is upstream of the fuel nozzle tip, and

wherein the oxidant nozzle tip, the fuel nozzle tip, and the recycle gas nozzle tip are curved such that the first stream, the second stream, and the third stream are ejected from the nozzles in a direction toward the central axis of the burner.

10. A method according to claim 9 , wherein the third stream is partially mixed with the second stream before the partially mixed third and second stream flows through the fuel outlet and reaches a combustion zone of the catalytic reactor.

11. A method according to claim 9 , wherein the second stream is gaseous hydrocarbon and the third stream is a recycle gas from a Fisher Tropsh synthesis.

12. A method according to claim 9 , wherein the temperature of the second stream is within a critical metal dusting temperature range and the temperature of the third stream is outside a critical metal dusting temperature range.

13. A method according to claim 10 , wherein the third stream is sufficiently mixed with the second stream to avoid soot formation.

14. Use of a burner according to claim 1 for carrying out catalytic processes in a gas fueled reactor.