HYDROGEN PRODUCTION FACILITY HAVING EQUIPMENT WITH A NITRIDATION PROTECTIVE LAYER

Abstract

A hydrogen production facility having equipment with a nitridation protective layer is provided. The hydrogen production facility can include a reformer configured to catalytically convert a feed stream into a product stream comprising hydrogen, the reformer having a plurality of catalyst tubes and a plurality of burners configured to provide heat to the catalyst tubes; means for providing the feed stream to the reformer from an ammonia source, wherein the feed stream comprises at least 90% of ammonia, wherein the plurality of catalyst tubes comprise a nitridation protective layer on an inner surface of the catalyst tubes.

Claims

1. A hydrogen production facility comprising: a reformer configured to catalytically convert a feed stream into a product stream comprising hydrogen, the reformer having a plurality of catalyst tubes and a plurality of burners configured to provide heat to the catalyst tubes; and means for providing the feed stream to the reformer from an ammonia source, wherein the feed stream comprises at least 90% of ammonia a reformer configured to catalytically convert a feed stream into a product stream comprising hydrogen, the reformer having a plurality of catalyst tubes and a plurality of burners configured to provide heat to the catalyst tubes; and means for providing the feed stream to the reformer from an ammonia source, wherein the feed stream comprises at least 90% of ammonia, wherein the plurality of catalyst tubes comprise a nitridation protective layer on an inner surface of the catalyst tubes.

2. The hydrogen production facility as claimed in claim 1, wherein the nitridation protective layer is selected from the group consisting of a protective liner material that is mechanically coupled to the inner surface, an aluminization layer applied to the inner surface, a diffusion barrier layer in conjunction with the aluminization layer applied to the inner surface, wherein the diffusion barrier layer is disposed between the inner surface and the aluminization layer, and a weld-overlay applied to the inner surface.

3. The hydrogen production facility as claimed in claim 1, wherein the nitridation protective layer comprises the diffusion barrier layer in conjunction with the aluminization layer applied to the inner surface.

4. The hydrogen production facility as claimed in claim 3, wherein the diffusion barrier layer comprises a chrome-silicon barrier layer.

5. The hydrogen production facility as claimed in claim 1, wherein the nitridation protective layer comprises applying a protective liner that is mechanically coupled to the inner surface.

6. The hydrogen production facility as claimed in claim 5, wherein the protective liner material is selected from a group of alloys having a nickel content in excess of 60%.

7. The hydrogen production facility as claimed in claim 5, wherein the protective liner is coupled to the inner surface via at only one end thereby reducing potential damage during thermal expansion.

8. The hydrogen production facility as claimed in claim 5, wherein the protective liner is coupled to the inner surface of the equipment via a flange or welding.

9. The hydrogen production facility as claimed in claim 5, wherein the protective liner is configured to have a substantially similar thermal expansion coefficient to that of the piece of equipment.

10. The hydrogen production facility as claimed in claim 1, wherein the nitridation protective layer comprises a protective weld-overlay applied to the inner surface

11. The hydrogen production facility as claimed in claim 10, wherein the protective weld-overlay is selected from a group of alloys having a nickel content in excess of 60%.

12. The hydrogen production facility as claimed in claim 1, wherein the hydrogen production facility was formerly used to catalytically crack hydrocarbons in the presence of steam to produce hydrogen.

13. The hydrogen production facility as claimed in claim 1, further comprising additional equipment having the nitridation protective layer, wherein the additional equipment is selected from the group consisting of feed piping, a feed preheater, process gas heat exchangers, and combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it can admit to other equally effective embodiments.

[0047] FIG. 1 shows an embodiment of a cross-sectional view of a catalyst tube in conformance with a first embodiment of the present invention having a welded or flanged liner.

[0048] FIG. 2 shows an embodiment of a cross-sectional view of a catalyst tube in conformance with a second embodiment of the present invention having an aluminization layer without a diffusion barrier layer.

[0049] FIG. 3 shows an embodiment of a cross-sectional view of a catalyst tube in conformance with a third embodiment of the present invention having an aluminization layer with a diffusion barrier layer between the aluminization layer and the base material.

[0050] FIG. 4 shows an embodiment of a cross-sectional view of a catalyst tube in conformance with a fourth embodiment of the present invention having a weld-overlay.

DETAILED DESCRIPTION

[0051] While the invention will be described in connection with several embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all the alternatives, modifications and equivalence as may be included within the spirit and scope of the invention defined by the appended claims.

[0052] As used herein, aluminization layer is intended to cover a diffusion layer that includes a mixture of iron and nickel aluminides (e.g., FeAl, NiAl) with a preferred aluminum content of between 25-40 wt %.

[0053] While the current disclosure focuses on the protection of catalyst tubes, Applicants note that the inventive idea does not need to be restricted to its application in catalyst tubes only. It can also be used in some of the upstream equipment, if needed, for example in the feed superheating coils, heat exchangers, and connecting piping. This will be highly preferable, if the tie-in point is shifted further upstream in the process, for whatever reason, e.g., preheating of ammonia and heat integration of the flue gas and splitting of NH.sub.3 starting prior to entering the catalyst tubes due to temperature and a certain catalytic effect of metallic surfaces.

[0054] Formation of nitrides from elemental nickel is not documented in literature. The beneficial effects of reducing the nitridation susceptibility using nickel in steels include lower solubility of nitrogen and lower diffusion rates of nitrogen in alloys with nickel content up to 40 wt. %. However, some high content nickel base alloys are known to better withstand nitride formation and embrittlement as the aforementioned. One such candidate is Alloy 600. The currently used high-temperature, high-creep-strength catalyst tube material does not belong to these materials. Hence, the task is to optimize the material for the selection for the inner diameter surface of the catalyst tubes that are potentially affected by nitridationeither by replacing them with tubes made from another material or to coat/weld-overlay or line the inner diameter surface of the catalyst tube with a material having a lower nitridation embrittlement susceptibility.

[0055] Catalyst tubes have to be resistant not only against the inner process conditions but also against the outer high temperature flue gas atmosphere while providing sufficient creep strength, which materials with high nitridation resistance typically do not possess. Therefore, certain embodiments of the present invention concentrate on improving the nitridation resistance on the inside of the common catalyst tubes by applying an appropriate selection of a resistant material. The resistant material can be a very thin layer applied on the material surface, a combination of layers, or a thicker lining or weld-overlay. The resistant material can also be chosen in combination with an oxidizing process medium in such a manner that, due to a more oxidizing atmosphere, the material forms a protective oxide layer upon exposure to the ammonia and oxidizing agent mixture.

[0056] In certain embodiments, the liner material can be selected to be nickel or an alloy with a very high nickel content (Nickel content similar or higher than in alloy 600, i.e. Ni>60%). FIG. 1 provides a cross sectional view of a catalyst tube 1 having an outer wall 2 in accordance with these embodiments. In the embodiment shown, the liner 10 can be flanged to the inlet or welded 12 to the inner wall 3 of the catalyst tube 1. In these embodiments, either the protective liner 10 can be attached to the inner wall 3 of the catalyst tube only at one side (inlet), so that the different thermal expansion coefficients of the materials will not lead to damage of the liner 10 or the catalyst tube itself, or the material composition of the liner 10 is chosen such, that its thermal expansion coefficient is substantially similar to that of the catalyst tube 1. The latter solution would also allow the use of a material with non-optimal resistance against nitridation, but with the intention to replace it after reaching an appropriate lifetime. As used herein, an expansion coefficient that is substantially similar means that the expansion coefficients are the same+/?5%, or close enough that differences in thermal expansion do not cause problems in production or result in safety issues.

[0057] FIG. 2 provides another embodiment of the invention, which can include application of an aluminization layer 15 on the inner wall 3 (e.g., inner surface). Although an aluminum-containing alloy with only some percent aluminum is known to be very susceptible to nitridation because aluminum is a strong nitride former, at very high aluminum content, as it is the case in such a coating, a protective oxide layer will form at the surface, even in atmospheres with low oxygen partial pressure. The coating process could be, but is not limited to, aluminization by pack cementation.

[0058] In certain embodiments using pack cementation, a conversion layer with high aluminide (e.g., Ni.sub.3Al) content with a controlled thickness can be achieved.

[0059] The steps for providing the aluminization layer to an article having an internal cavity for protection against embrittlement can include introducing an aluminization source powder into the internal cavity through an inlet; heating the article with the aluminization source powder in the internal cavity to cause aluminum to transport from the aluminization source powder to the internal surface of the internal cavity; and thereafter removing the aluminization source powder from the internal cavity through the inlet.

[0060] FIG. 3 provides a similar solution to that shown in FIG. 2; however, in this embodiment, very high temperatures (e.g. above about 700? C.) might introduce diffusion processes between the base material 17 of the catalyst tube 1 and the aluminization layer 15, which might affect the protective effect of the coating itself. Therefore, in addition to the aluminization layer 15, by modification of the aluminization process, another layer is disposed between the aluminization layer 15 and the tube material 17 and works as a diffusion barrier 20. This additional barrier layer can be, as a non-limiting example, a chrome-silicon barrier layer.

[0061] As illustrated in FIGS. 2 and 3, one solution of the present invention is a catalyst tube 1 comprising: an external wall 2, an internal wall 3, an aluminization layer 15 mirroring at least a portion of the internal wall, a diffusion barrier 20 mirroring at least a portion of the internal wall, wherein the diffusion barrier 20 is between the internal wall 3 and the aluminization layer 15.

[0062] As the case may be, the catalyst tube according to the present invention can exhibit one or more of the following characteristics: the diffusion barrier 20 matches the shape of the internal wall 3 and the shape of the aluminization layer 15; the diffusion barrier 20 can be a chrome-silicon barrier layer disposed between the tube material 17 and the aluminization layer 15.

[0063] Preferably, the diffusion barrier fits the shape of the internal wall of the tube. The diffusion barrier must be selected as a function of its ability to withstand operating conditions at high temperature (700 to 1000? C.)

[0064] FIG. 4 provides yet another embodiment, in which resistance to nitridation can be achieved by adding a resistant weld-overlay 25 to the inner wall 3 of components in contact with ammonia and ammonia-cracking products. A few non-limiting examples can include catalyst tubes, piping, heat coil, heat exchanger tube, etc. . . . . This resistant material can include a nickel-base alloy with a minimum 60% nickel, and forms a barrier between the tube side medium and the internal metallic tube wall. This weld-overlay is a type of cladding, where the high nickel metal is added to the surface of the inner tube wall by melting a weld consumable and depositing it in one or more welding passes. Contrary to a solid liner material, the final closed surface of a weld-overlay is built up by overlapping single weld beads into a closed, protective surface

[0065] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, language referring to order, such as first and second, should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps or devices can be combined into a single step/device.

[0066] The singular forms a, an, and the include plural referents, unless the context clearly dictates otherwise. The terms about/approximately a particular value include that particular value plus or minus 10%, unless the context clearly dictates otherwise.

[0067] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0068] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.