BURNER FOR A REMFORMING REACTOR

Abstract

Burner for a reforming reactor including an oxidizer pipe arranged coaxially within a process gas annular channel, wherein the nozzle has a trumpet-like shape and the lip of the nozzle has a wave or sinusoidal profile.

Claims

1-13. (canceled)

14. A burner for reforming a process gas, the burner comprising: an oxidizer pipe arranged coaxially within a process gas annular channel, according to a vertical axis of the burner; wherein said oxidizer pipe extends further relative to an end section of the process gas annular channel, and the oxidizer pipe is a cylindrical pipe with an end nozzle which widens out to form a tip larger than the pipe, thus having a trumpet-like shape; wherein said end nozzle of the oxidizer pipe has a lip with a wave profile having a periodic sequence of crests and troughs according to said axis, said wave profile having higher and lower parts referred to vertical elevation.

15. The burner according to claim 14, wherein, relative to a plane of reference perpendicular to said axial direction of the burner, the peak amplitude of the wave profile of the lip is 0.004 to 0.06 relative to a diameter of the oxidizer pipe.

16. The burner according to claim 14, wherein the number of waves of the lip is 0.016/mm to 0.144/mm, relative to a diameter of the oxidizer pipe.

17. The burner according to claim 14, wherein the wave profile of the lip is represented mathematically by a periodic function such as any of: a sine function; a polynomial function which is symmetrically or anti-symmetrically repeated; a symmetric or antisymmetric repetition of a shape; or combinations thereof.

18. The burner according to claim 14, wherein the lip has a sinusoidal profile.

19. The burner according to claim 18, wherein the sinusoidal profile has an amplitude of 1 mm to 6 mm and a period of 4 to 24 waves.

20. The burner according to claim 14, including a swirler (8) located in the oxidizer pipe upstream the nozzle.

21. The burner according to claim 14, wherein at least the nozzle of the oxidizer pipe is made with 3D printing, preferably by additive manufacturing.

22. A reactor for reforming a gas feed, the reactor comprising: a combustion chamber; the burner according to claim 14; wherein the burner is installed above the combustion chamber so that the oxidizer pipe and the process gas annular channel are arranged vertically, and said oxidizer pipe extends below an end section of the process gas annular channel, thus extending into the combustion chamber.

23. The reactor according to claim 22, adapted for secondary reforming of a process gas produced after primary reforming with steam of a hydrocarbon feedstock.

24. A process for reforming a hydrocarbon feedstock to produce a hydrogen-containing gas, the process comprising: primary reforming the feedstock in the presence of steam, obtaining a primary reforming effluent, and secondary reforming of said effluent in the presence of an oxidizer, wherein the secondary reforming is performed in the reactor according to claim 22.

25. The process according to claim 24, wherein a diffusion flame is formed at the tip of the oxidizer pipe where the oxidizer meets the process gas.

26. The process according to claim 24, wherein the oxidizer is any of air, oxygen-enriched air or oxygen.

Description

DESCRIPTION OF THE FIGURES

[0039] The invention is now elucidated with the help of the figures where:

[0040] FIG. 1 is a schematic section of a secondary reformer equipped with a burner according to the invention.

[0041] FIG. 2 illustrates the nozzle of the oxidizer pipe of the burner.

[0042] FIG. 3 illustrates further the profile of the nozzle.

[0043] FIG. 1 illustrates the following main features: [0044] 1 Burner [0045] 2 Combustion chamber [0046] 3 Catalyst for secondary reforming [0047] 4 Oxidizer pipe [0048] 5 Process gas annular channel [0049] 6 Gas distributor [0050] 7 Gas inlet pipe [0051] 8 Swirler [0052] 9 End section of the annular channel 5 [0053] 10 Nozzle of the oxidizer pipe 4 [0054] 11 Combustion flame (diffusion flame) [0055] 12 Process gas stream [0056] 13 Oxidizer stream [0057] 14 Wall of the upper portion of the combustion chamber 2.

[0058] FIG. 1 illustrates a reactor R fitted with the burner 1. The reactor receives the process gas 12 and the oxidizer 13. With the help of the burner 1, the process gas and the oxidizer 12 are contacted in the combustion chamber 2, so that the combustion brings the gas to a suitable temperature for the subsequent catalytic reaction in the catalyst zone 3.

[0059] The process gas 12 may be the effluent of a primary reformer, e.g. a fired furnace. The process gas 12 may result from the steam reforming of a hydrocarbon, such as methane. The oxidizer 13 may be air, enriched air or oxygen provided by an air separation unit.

[0060] The process gas 12 and the oxidizer stream 13 reach the combustion chamber 2 via the vertical pipe 4 and the annular channel 5 around said pipe 4. The pipe 4 and channel 5 are separated so that the oxidizer and gas cannot mix within the burner 1 and before they enter the combustion chamber 2.

[0061] At the end section 9, the process gas 12 enters the upper zone of the combustion chamber 2. Preferably said upper zone has a conical wall, diverging towards the underlying catalyst bed, as shown.

[0062] When exiting the channel 5, the gas 12 may potentially meet the oxidizer 13. The pipe 4 extends below the end section 9 (i.e. within the combustion chamber 2) so that the oxidizer nozzle 10 is actually below the end section 9. Here, a diffusion flame 11 is formed. A recirculation flow is also created, but the location of the nozzle 10 avoids a back-flame in the channel 5.

[0063] The oxidizer stream exiting the pipe 4 has a swirling motion caused by the swirler 8. The nozzle 10 widens out radially towards the wall 14 thus forming a trumpet-like tip 15 (FIG. 2), from which the swirled flow projects radially to mix with the gas. Accordingly, the outlet end section of the nozzle 10 is larger (i.e. lies on a larger diameter) than the diameter of the pipe 4.

[0064] Still referring to FIG. 2, the lip 16 of the pipe 4 has a sinusoidal profile with a number of waves 17, each wave 17 having a crest 18 and a trough 19 in the direction of the axis A-A, which is the vertical direction as the pipe 4 is vertically mounted in the reformer R above the combustion chamber 2.

[0065] FIG. 3 illustrates the sinusoidal profile of the lip 16 relative to a reference plane 20. Said plane 20 denotes the position of a planar lip (circumferential lip) according to the prior art. The figure illustrates the deviation of the inventive sinusoidal lip 16 from the conventional planar lip according to the vertical coordinate Z (positive upward). Particularly, FIG. 3 illustrates that the crests 18 are located above the plane 20 at a Z-coordinate +d whereas the troughs 19 are located below the plane 20 at a Z-coordinate-d. The crests 18 may be regarded as highs of the lip 16, whereas the troughs 19 are lows.

[0066] FIG. 3 illustrates also the diameter D of the pipe 4, which may be a reference for determining the number and/or amplitude of waves 17 according to some embodiments. Said diameter D is the inner diameter of the cylindrical part of the pipe 4, before the trumpet-like end.

[0067] Each wave 17 in the lip 16 may be regarded to include a positive cycle above the reference plane 20 and a negative cycle below said plane.

[0068] The crests 18 are slightly more distant from the flame 11 (which is responsible for the thermal stress, mainly by radiation); the toughs 19 are slightly closer to the flame but take the advantage of better cooling due to higher velocity of the flow. In summary, the sinusoidal lip 16 is less stressed than a planar lip under the same conditions.

[0069] The figures illustrate that the wave profile of the lip 16 lies in a cylindrical surface parallel to the vertical axis A-A of the burner 1. The wave profile is arranged vertically according to the reference direction Z.

[0070] A CFD calculation has revealed a reduction of the maximum temperature of the lip around 10 C. and a maximum thermal stress reduced to about 40% to 70% of the original value.

[0071] The figures illustrate a sinusoidal lip 16 but more in general other periodic profiles may be used within the scope of the invention.