Methods for converting existing industrial units to produce hydrogen from ammonia

Abstract

The method may include providing an existing SMR, the SMR having been previously used to produce hydrogen from hydrocarbons, and increasing the nitridation resistance of an interior surface of equipment used in the existing SMR by adding a protective layer to the interior surface of the equipment, the equipment being selected from catalyst tubes, feed piping, feed preheaters, process gas heat exchangers, and combinations thereof. The hydrogen production facility may include a reformer configured to catalytically convert a feed stream to a product stream comprising hydrogen, means for providing a feed stream to the reformer from an ammonia source, the feed stream comprising at least 90% ammonia, and a plurality of catalyst tubes including a nitride protective layer on the interior surface of the catalyst tubes.

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for hydrogen production using existing industrial units, and more particularly, embodiments of the present invention relate to avoiding embrittlement of steel caused by nitriding. [Background technology]

[0002] New energy carriers are becoming increasingly important in efforts to reduce the impact of carbon dioxide emissions. One of the leading energy carriers is hydrogen. However, due to its small molecular size, high pressure conditions, and very low boiling point, transporting elemental hydrogen is difficult and costly.

[0003] Ammonia (NH3) has received some attention in the literature because existing infrastructure can be used for storage and transportation (e.g., LPG infrastructure). Therefore, hydrogen production using ammonia instead of natural gas to produce hydrogen is predicted to be the future for next-generation hydrogen production. Unfortunately, new industrial facilities are quite costly to build and require many years of design and production. Therefore, it may be at least a decade or more before any new dedicated ammonia cracking facilities are operational. In the meantime, it remains desirable to advance hydrogen production in a more environmentally friendly manner, which involves the decomposition of ammonia gas by using existing hydrogen production facilities.

[0004] Ammonia can be decomposed into hydrogen and nitrogen by thermal decomposition and / or in the presence of a catalyst at ambient pressure and moderate temperatures (450-600°C). To save energy in compressing hydrogen in the final stage, it may be advantageous to apply higher pressures for the NH decomposition reaction (compressing ammonia gas is easier than compressing hydrogen gas due to the small molecular size of hydrogen). However, at higher pressures, the decomposition reaction is not favored according to Le Chatelier's principle, so higher temperatures (around 700°C) are advantageous to achieve economical conversion rates.

[0005] Unfortunately, ammonia is known to cause nitride formation (nitriding) in steel, especially at high temperatures, during the decomposition process of NH3 into H2 and N2. This is because the ammonia decomposition reaction at high temperatures leads to the formation of atomic nitrogen, which diffuses into the metallic material to form nitrides, thereby causing embrittlement of the steel.

[0006] Since some steels also act as catalysts for the NH3 decomposition process, nitride formation in steel can occur already at its surface and at temperatures where only small ammonia conversion rates are observed, which means that steels can already be at risk of embrittlement during heating of ammonia above 400°C.

[0007] Current steam methane reformers (SMRs) operate at temperatures well above 700°C with hydrocarbon feedstocks such as natural gas, LPG, naphtha, refinery off-gas, etc. Natural gas generally contains nitrogen, but this molecular nitrogen does not undergo significant nitride formation in the steel from the process (tube) side because the partial pressure of nitrogen is not high enough and no catalyst exists to split the N2 into atomic nitrogen. Therefore, existing SMRs are not designed with this eventuality in mind.

[0008] Current materials applied in the feedstock pretreatment and preheating sections of SMR plants are carbon steel (CS), chromium-molybdenum low-alloy steel (CrMo), and stainless steel (SS). In short, the applied steels, especially iron, but also important alloying elements such as chromium, can easily form nitrides. Furthermore, most of the processing equipment in syngas generation units can be operated at temperatures well above 400°C. Therefore, simply switching the feedstock from hydrocarbons to ammonia for existing hydrogen production facilities is not feasible. Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, there is a need in the art to provide an industrial facility that can efficiently produce hydrogen from ammonia, particularly by retrofitting existing industrial hydrogen production facilities to produce hydrogen from ammonia feed gas, while preventing, delaying or at least minimizing embrittlement problems during operation. [Means for solving the problem]

[0010] The present invention relates to an apparatus and process that meets at least one of these needs. In some embodiments of the invention, a protective liner is applied to the common catalyst tube. In a second embodiment, the invention may include applying an aluminizing layer to the inner tube surface. In a third embodiment, which addresses nitridation resistance at very high temperatures (e.g., above about 700°C), a diffusion barrier is applied between the aluminizing layer and the tube material to limit diffusion between the aluminizing layer and the tube material. This diffusion barrier is preferably configured to inhibit or at least minimize interaction between the substrate (i.e., the aluminizing layer) and the environment. In a fourth embodiment, a weld overlay may be applied to the inner surface of the catalyst tube.

[0011] In one embodiment, a method of converting an existing steam methane reformer (SMR) to produce hydrogen via ammonia decomposition by adding a protective layer to the interior surfaces of equipment used in the SMR may include providing an existing SMR, the SMR having been previously used to produce hydrogen from a hydrocarbon feedstock; and enhancing the nitridation resistance of the interior surfaces of the equipment, wherein the equipment is selected from the group consisting of catalyst tubes, feed piping, feed preheaters, process gas heat exchangers, and combinations thereof.

[0012] In an optional embodiment of the method, the step of increasing the nitridation resistance comprises a process selected from the group consisting of applying a protective liner material mechanically bonded to the inner surface, applying an aluminizing layer to the inner surface, applying a diffusion barrier layer in conjunction with the aluminizing layer, the diffusion barrier layer being disposed between the inner surface and the aluminizing layer, and applying a weld overlay to the inner surface; The step of increasing nitridation resistance includes applying an aluminizing layer to the inner surface; the step of applying the aluminizing layer includes the steps of: introducing an aluminizing source powder through an inlet into an interior space bounded by an interior surface of the equipment, the interior surface of the equipment including a base metal; heating the equipment to transfer aluminum from the aluminizing source powder to the interior surface of the equipment and allowing the aluminum to diffuse into and react with elements in the base metal to form an aluminide layer; and removing the aluminizing source powder from the interior space; the step of applying an aluminizing layer includes the steps of depositing an aluminizing slurry layer on an inner surface of the equipment through an inlet, the inner surface of the equipment including a base metal; drying the slurry layer; heating the equipment to transfer aluminum from the aluminizing slurry to the inner surface of the equipment and to allow the aluminum to diffuse into and react with elements in the base metal to form an aluminide layer; and removing the remainder of the aluminizing slurry from the interior space; the step of increasing the nitridation resistance includes applying a diffusion barrier layer to an inner surface of the equipment and applying an aluminizing layer to the diffusion barrier layer, whereby the diffusion barrier layer is disposed between the inner surface of the equipment and the aluminizing layer; the diffusion barrier layer comprises a chromium-silicon barrier layer; the step of enhancing nitridation resistance includes applying a protective liner mechanically bonded to the interior surface; The protective liner material is selected from the group of alloys having a nickel content of more than 60%; The protective liner is bonded to the inner surface via only one end, thereby reducing potential damage during thermal expansion; The protective liner is bonded to the inner surface of the equipment via flanges or welding. the protective liner is configured to have a coefficient of thermal expansion substantially similar to that of the device; The step of enhancing nitridation resistance includes applying a protective weld overlay to the interior surface; The protective weld overlay is selected from the group of alloys having a nickel content of more than 60%, and / or The nitridation-resistant equipment may be new equipment or previously used in existing SMRs.

[0013] In another embodiment, a method may include providing an existing hydrogen industrial unit, the hydrogen industrial unit having been previously used to produce hydrogen from a hydrocarbon feedstock, and increasing the nitridation resistance of an interior surface of equipment, the equipment having increased nitridation resistance being new equipment or previously used in the existing hydrogen industrial unit.

[0014] In an optional embodiment of the method, the equipment is selected from the group consisting of a feed preheater, a feed piping, a catalyst tube, a process gas heat exchanger, an outlet system, a process gas boiler, and combinations thereof; and / or The protective layer is applied to an apparatus configured to be in fluid communication with an ammonia feed gas at temperatures above 400°C.

[0015] In another embodiment, a hydrogen production facility is provided that may include a reformer configured to catalytically convert a feed stream to a product stream comprising hydrogen, the reformer having a plurality of catalytic tubes and a plurality of burners configured to provide heat to the catalytic tubes; and means for providing a feed stream to the reformer from an ammonia source, the feed stream comprising at least 90% ammonia, wherein the plurality of catalytic tubes include a nitride protective layer on an inner surface of the catalytic tubes.

[0016] In an optional embodiment of the device, the nitrided protective layer is selected from the group consisting of a protective liner material mechanically bonded to the inner surface, an aluminized layer applied to the inner surface, a diffusion barrier layer applied to the inner surface together with the aluminized layer, the diffusion barrier layer being disposed between the inner surface and the aluminized layer, and a weld overlay applied to the inner surface; The nitrided protective layer includes a diffusion barrier layer applied to the inner surface in combination with an aluminized layer; the diffusion barrier layer comprises a chromium-silicon barrier layer; The nitride protective layer includes applying a protective liner that is mechanically bonded to the inner surface; The protective liner material is selected from the group of alloys having a nickel content of more than 60%; The protective liner is bonded to the inner surface via only one end, thereby reducing potential damage during thermal expansion; The protective liner is bonded to the inner surface of the equipment via flanges or welding. the protective liner is configured to have a coefficient of thermal expansion substantially similar to that of the device; The nitrided protective layer includes a protective weld overlay applied to the inner surface. The protective weld overlay is selected from the group of alloys having a nickel content of more than 60%; The hydrogen production facility was previously used for catalytic cracking of hydrocarbons in the presence of steam to produce hydrogen; and / or The hydrogen production facility may also include additional equipment having a nitride protective layer, the additional equipment being selected from the group consisting of feed piping, feedstock preheaters, process gas heat exchangers, and combinations thereof.

[0017] The foregoing has outlined, rather broadly, the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the present invention which form the subject of the claims of the present invention will be described hereinafter. Those skilled in the art will appreciate that the conception and specific embodiments disclosed may readily be utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the present invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description when considered in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are provided for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.

[0018] These and other features, aspects, and advantages of the present invention will be better understood with regard to the following description, claims, and accompanying drawings, which should be noted, however, that the drawings illustrate only some embodiments of the invention and are therefore not to be considered as limiting the scope of the invention, since other equally effective embodiments may be recognized. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 shows one embodiment of a cross-section of a catalyst tube according to a first embodiment of the present invention having a welded or flanged liner. [Figure 2] FIG. 2 shows one embodiment of a catalyst tube cross section according to a second embodiment of the invention, having an aluminized layer without a diffusion barrier layer. [Figure 3] FIG. 3 shows one embodiment of a cross-sectional view of a catalyst tube according to a third embodiment of the present invention having an aluminized layer with a diffusion barrier layer between the aluminized layer and the base material. [Figure 4] 10 shows one embodiment of a cross-sectional view of a catalytic tube according to a fourth embodiment of the present invention having a weld overlay. DETAILED DESCRIPTION OF THE INVENTION

[0020] While the present invention will be described in connection with certain embodiments, it will be understood that it is not intended to limit the invention to those embodiments, but rather to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

[0021] As used herein, "aluminized layer" is intended to cover a diffusion layer comprising a mixture of iron aluminide and nickel aluminide (eg, FeAl, NiAl) with a preferred aluminum content of 25-40 wt. %.

[0022] While this disclosure focuses on protecting the catalyst tubes, the applicant recognizes that the inventive concept need not be limited to its application in catalyst tubes alone. If desired, it can also be used in some of the upstream equipment, such as feed heating coils, heat exchangers, and connecting piping. This is highly preferable when the application point is shifted further upstream in the process, for whatever reason, such as ammonia preheating and flue gas heat integration, and NH3 separation, which begins before entering the catalyst tubes due to certain catalytic effects of temperature and metal surfaces.

[0023] The formation of nitrides from elemental nickel has not been documented. The beneficial effects of using nickel in steel to reduce nitriding susceptibility include the low solubility and diffusivity of nitrogen in alloys with nickel contents up to 40 wt. However, some high-content nickel-based alloys are known to better resist the nitride formation and embrittlement discussed above. One such candidate is Alloy 600. Currently used high-temperature, high-creep-strength catalyst tube materials do not belong to these categories. Therefore, the challenge is to optimize the materials to select for the inner diameter surfaces of catalyst tubes potentially affected by nitriding. This can be done either by replacing them with tubes made of a different material or by coating / welding or lining the inner diameter surfaces of catalyst tubes with materials that have low nitriding embrittlement susceptibility.

[0024] The catalyst tubes must be able to withstand not only the internal processing conditions but also the external high-temperature flue gas atmosphere while providing sufficient creep strength, which is generally not possessed by highly nitridation-resistant materials. Therefore, some embodiments of the present invention focus on improving nitridation resistance inside the common catalyst tubes by making an appropriate selection of a resistant material. The resistant material can be a very thin layer applied to the material surface, a combination of layers, or a thicker lining or weld overlay. For more oxidizing atmospheres, the resistant material can also be selected in combination with an oxidizing process medium so that the material forms a protective oxide layer when exposed to a mixture of ammonia and an oxidizer.

[0025] In some embodiments, the liner material may be selected to be nickel or an alloy with a very high nickel content (nickel content similar to or higher than Alloy 600, i.e., Ni > 60%). FIG. 1 provides a cross-sectional view of a catalyst tube 1 having an outer wall 2 according to these embodiments. In the illustrated embodiment, the liner 10 may be flanged at the inlet or weld 12 to the inner wall 3 of the catalyst tube 1. In these embodiments, either the protective liner 10 may be attached to the inner wall 3 of the catalyst tube on only one side (the inlet) so that different thermal expansion coefficients of the materials do not lead to damage to the liner 10 or the catalyst tube itself, or the material composition of the liner 10 is selected so that its thermal expansion coefficient is substantially similar to that of the catalyst tube 1. The latter solution also allows the use of a material with non-optimal nitridation resistance but intended to replace it after reaching an appropriate lifespan. As used herein, "substantially similar" expansion coefficient means that the expansion coefficients are the same, ±5%, or close enough that the difference in thermal expansion does not cause production problems or safety issues.

[0026] 2 provides another embodiment of the present invention, which may include applying an aluminizing layer 15 on the interior wall 3 (e.g., the interior surface). Aluminum-containing alloys, with only a few percent aluminum, are known to be very susceptible to nitriding because, at very high aluminum contents, as in the case of such coatings, aluminum is a strong nitride former, and a protective oxide layer forms on its surface even in an atmosphere with a low oxygen partial pressure. The coating process may be, but is not limited to, aluminizing by pack cementation.

[0027] In some embodiments using pack cementation, a conversion layer with controlled thickness and high aluminide (eg, Ni3Al) content can be achieved.

[0028] The step of providing an aluminizing layer on an article having an internal cavity for protection against embrittlement may include introducing an aluminizing source powder into the internal cavity through an inlet, heating the article with the aluminizing source powder within the internal cavity so that aluminum is transported from the aluminizing source powder to an internal surface of the internal cavity, and then removing the aluminizing source powder from the internal cavity through the inlet.

[0029] Figure 3 provides a similar solution to that shown in Figure 2. However, in this embodiment, the very high temperatures (e.g., above about 700°C) may introduce diffusion processes between the base material 17 of the catalyst tube 1 and the aluminizing layer 15, which may affect the protective effect of the coating itself. Therefore, by modifying the aluminizing process, in addition to the aluminizing layer 15, another layer is placed between the aluminizing layer 15 and the tube material 17, acting as a diffusion barrier 20. This additional barrier layer may be, as a non-limiting example, a chromium-silicon barrier layer.

[0030] As shown in Figures 2 and 3, one solution of the present invention is a catalyst tube 1 including an outer wall 2, an inner wall 3, an aluminizing layer 15 that mirrors at least a portion of the inner wall, and a diffusion barrier 20 that mirrors at least a portion of the inner wall, the diffusion barrier 20 being between the inner wall 3 and the aluminizing layer 15.

[0031] Optionally, the catalyst tube according to the invention may exhibit one or more of the following properties: The diffusion barrier 20 conforms to the shape of the inner wall 3 and the shape of the aluminizing layer 15. The diffusion barrier 20 may be a chromium-silicon barrier layer disposed between the tube material 17 and the aluminizing layer 15.

[0032] Preferably, the diffusion barrier conforms to the shape of the inner wall of the tube. The diffusion barrier should be selected for its ability to withstand high temperature (700-1000°C) operating conditions.

[0033] FIG. 4 provides yet another embodiment in which nitridation resistance can be achieved by adding a resistance weld overlay 25 to the inner wall 3 of a component that comes into contact with ammonia and ammonia decomposition products. Some non-limiting examples can include catalytic tubes, piping, thermal coils, heat exchanger tubes, etc. This resistance material can include a nickel-based alloy with a minimum of 60% nickel, forming a barrier between the tubeside medium and the inner metal tube wall. This weld overlay is a type of cladding in which a high-nickel metal is added to the surface of the inner tube wall by melting a welding consumable and depositing it in one or more weld passes. In contrast to solid liner materials, the final closed surface of the weld overlay is created by overlapping a single weld bead onto the protective closed surface.

[0034] While the present 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. It is therefore 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 of, or consist essentially of disclosed elements, or may be practiced in the absence of elements that are not disclosed. Furthermore, sequential language, e.g., first and second, is to be understood in an illustrative sense, not a limiting sense. For example, one skilled in the art will recognize that several steps or devices may be combined into a single step / device.

[0035] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. The term about / approximately a particular value includes the particular value plus or minus 10% unless the context clearly dictates otherwise.

[0036] Optional or optional means that the subsequently described event or circumstance may or may not occur. The description includes cases where the event or circumstance occurs and cases where it does not occur.

[0037] 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 understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said ranges.

Claims

1. 1. A method of converting an existing steam methane reformer (SMR) to produce hydrogen via ammonia decomposition by adding a protective layer to the interior surfaces of the equipment used in the SMR, comprising: providing the existing SMR, the SMR having been previously used to produce hydrogen from a hydrocarbon feedstock; increasing the nitridation resistance of the interior surface of the device; wherein the equipment is selected from the group consisting of catalyst tubes, feed piping, feed preheaters, process gas heat exchangers, and combinations thereof.

2. 2. The method of claim 1, wherein the step of increasing the nitridation resistance comprises a process selected from the group consisting of applying a protective liner material mechanically bonded to the inner surface, applying an aluminizing layer to the inner surface, applying a diffusion barrier layer in conjunction with the aluminizing layer, the diffusion barrier layer being disposed between the inner surface and the aluminizing layer, and applying a weld overlay to the inner surface.

3. The method of claim 1 , wherein the step of increasing the nitridation resistance comprises applying an aluminizing layer to the interior surface.

4. The step of applying the aluminizing layer comprises: introducing an aluminizing source powder through an inlet into an interior space bounded by the interior surface of the equipment, the interior surface of the equipment comprising a base metal; heating the equipment to transfer aluminum from the aluminizing source powder to the interior surface of the equipment and allowing the aluminum to diffuse into and react with elements in the base metal to form an aluminide-rich layer; removing the aluminizing source powder from the interior space; The method of claim 3, comprising:

5. The step of applying the aluminizing layer comprises: depositing an aluminizing slurry layer on the interior surface of the equipment through an inlet, the interior surface of the equipment comprising a base metal; drying the slurry layer; heating the equipment to transfer aluminum from the aluminizing slurry to the interior surface of the equipment and allowing the aluminum to diffuse into and react with elements in the base metal to form an aluminide-rich layer; removing the remainder of the aluminizing slurry from the interior space; The method of claim 3, comprising:

6. 2. The method of claim 1, wherein the step of increasing the nitridation resistance comprises applying a diffusion barrier layer to the interior surface of the equipment and applying an aluminizing layer to the diffusion barrier layer, whereby the diffusion barrier layer is disposed between the interior surface of the equipment and the aluminizing layer.

7. The method of claim 6, wherein the diffusion barrier layer comprises a chromium-silicon barrier layer.

8. The method of claim 1 , wherein the step of increasing the nitridation resistance comprises applying a protective liner mechanically bonded to the interior surface.

9. The method of claim 8 , wherein the protective liner material is selected from a group of alloys having a nickel content greater than 60%.

10. The method of claim 8 , wherein the protective liner is bonded to the interior surface via only one end, thereby reducing potential damage during thermal expansion.

11. a reformer configured to catalytically convert a feed stream into a product stream comprising hydrogen, the reformer having a plurality of catalytic tubes and a plurality of burners configured to provide heat to the catalytic tubes; means for providing said feed stream to said reformer from an ammonia source, said feed stream comprising at least 90% ammonia; a reformer configured to catalytically convert a feed stream into a product stream comprising hydrogen, the reformer having a plurality of catalytic tubes and a plurality of burners configured to provide heat to the catalytic tubes; means for providing said feed stream to said reformer from an ammonia source, said feed stream comprising at least 90% ammonia; wherein the plurality of catalyst tubes include a nitride protective layer on an inner surface of the catalyst tubes.

12. 12. The hydrogen production facility according to claim 11, wherein the nitride protective layer is selected from the group consisting of a protective liner material mechanically bonded to the inner surface, an aluminizing layer applied to the inner surface, a diffusion barrier layer applied to the inner surface together with the aluminizing layer, the diffusion barrier layer being disposed between the inner surface and the aluminizing layer, and a weld overlay applied to the inner surface.

13. The hydrogen production facility of claim 11 , wherein the nitride protective layer comprises a diffusion barrier layer applied to the interior surface in combination with an aluminizing layer.

14. The hydrogen production facility of claim 13 , wherein the diffusion barrier layer comprises a chromium-silicon barrier layer.

15. The hydrogen production facility of claim 11 , wherein the nitride protective layer comprises applying a protective liner mechanically bonded to the interior surface.

16. The hydrogen production facility of claim 15 , wherein the protective liner material is selected from a group of alloys having a nickel content greater than 60%.

17. The hydrogen production facility of claim 15 , wherein the protective liner is bonded to the interior surface via only one end, thereby reducing potential damage during thermal expansion.

18. The hydrogen production facility of claim 15 , wherein the protective liner is coupled to the interior surface of the equipment via a flange or a weld.

19. The hydrogen production facility of claim 15 , wherein the protective liner is configured to have a coefficient of thermal expansion substantially similar to that of the equipment.

20. The hydrogen production facility of claim 11 , wherein the nitride protective layer comprises a protective weld overlay applied to the interior surface.

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