Method and apparatus for integrating ammonia decomposition into a steam methane reformer

Abstract

A method and apparatus for modifying an existing steam methane reformer (SMR) for ammonia decomposition is provided. In this embodiment, the existing SMR may include a pre-reformer, a desulfurization unit, a furnace (50), a waste heat recovery section, a water-gas shift reactor, a pressure swing adsorption (PSA) unit, the furnace (50) having a plurality of SMR tubes and a plurality of burners. In a particular embodiment, the method may include the steps of: preparing the existing SMR; taking the desulfurization unit offline so that fluid does not pass through the desulfurization unit during operation; taking the pre-reformer offline so that fluid does not pass through the pre-reformer during operation; and adding means for supplying a gaseous ammonia flow to the SMR tubes.

Description

Technical Field

[0001] The present invention relates to an apparatus and method for producing hydrogen using existing industrial units. More specifically, embodiments of the present invention relate to avoiding embrittlement of steel caused by nitrides in an existing steam methane reformer modified to produce hydrogen, particularly from an ammonia feed stream.

Background Art

[0002] In efforts to reduce the impact of carbon dioxide emissions, the importance of new energy carriers has been increasing. One of the major energy carriers is hydrogen, but its molecular size is small, it requires high pressure, and its boiling point is very low, making the transportation of elemental hydrogen difficult and costly.

[0003] Ammonia (NH3) has attracted attention in the literature because existing infrastructure (e.g., LPG infrastructure) can be used for storage and transportation. Therefore, the production of hydrogen using ammonia instead of natural gas to produce elemental hydrogen is predicted to be the future image of next-generation hydrogen production. Unfortunately, the construction of new industrial facilities is extremely costly and requires many years for design and manufacturing. Therefore, it is considered that it will take at least 10 years or more until new dedicated ammonia decomposition facilities can be operated. Until then, it is still desirable to proceed with the production of hydrogen in a more environmentally considerate manner, including decomposing ammonia gas using existing hydrogen production facilities.

[0004] Ammonia can be decomposed into hydrogen and nitrogen in the presence of a catalyst, at ambient pressure, and at a moderate temperature (450-600°C). Applying higher pressure during the NH3 decomposition reaction can be advantageous in order to conserve energy for hydrogen compression in the final stage (ammonia gas is easier to compress than hydrogen gas due to the smaller molecular size of hydrogen). However, high pressure is unfavorable for the decomposition reaction due to Le Chatelier's principle, so a higher temperature (approximately 700°C) is advantageous for achieving an economically viable conversion rate.

[0005] Unfortunately, ammonia is known to form nitrides in steel, especially at high temperatures, during the decomposition of NH3 into H2 and N2. This is because the ammonia decomposition reaction at high temperatures produces atomic nitrogen, which diffuses into the metallic material to form nitrides, thereby causing the steel to become brittle.

[0006] Because some steels also function as catalysts in the NH3 decomposition process, nitride formation in steel can occur on the steel surface and even at temperatures where only slight ammonia conversion rates are observed. In other words, while heating ammonia to temperatures above 400°C, the steel may already be at risk of embrittlement.

[0007] Currently, steam methane reformers (SMRs) operate at temperatures well above 700°C using hydrocarbon feedstocks such as natural gas, LPG, naphtha, and refinery off-gas. Figure 1 is a flow diagram of a typical SMR process. Natural gas 2 at approximately 30°C and recycled hydrogen 4 are mixed and heated to approximately 360°C in a heat exchanger 10 to form a high-temperature feed stream 12. Next, to remove sulfur from the high-temperature feed stream 12, it is introduced into a desulfurization unit 20 to form a clean high-temperature feed stream 22 with a significantly reduced sulfur content compared to the high-temperature feed stream 12. The clean high-temperature feed stream 22 is then mixed with process steam 24, heated in an SMR heat recovery section 30, and then introduced into a pre-reformer 40 to convert heavy hydrocarbons into methane and carbon oxides (CO, CO2) at relatively lower temperatures (typically 400-550°C). The low temperature of the pre-reformer 40 is used to prevent coke from accumulating on the walls and catalyst surface of the reformer 50.

[0008] A pre-reformer uses a highly active catalyst to partially complete the steam reforming reaction at a much lower temperature upstream of the main steam reformer. In addition to reducing coke formation, the use of a pre-reformer also has the advantage of allowing for a smaller conventional steam reformer, which is the most expensive piece of equipment in the plant.

[0009] Next, the pre-reformed flow 42 is reheated in the SMR heat recovery section 30, which uses heat from the exhaust gas of the primary SMR reaction, before being introduced into the reforming tube of the SMR furnace 50. After heating, it is sent to the steam methane reformer 50 for reforming to form the crude synthesis gas flow 52. Since the reforming reaction is an endothermic reaction, heat is added to the reaction by the combustion of fuel in the burner. The resulting crude synthesis gas flow 52 is then supplied to the high-temperature water-gas shift reactor 60, where CO reacts with H2O to convert CO to CO2 and produce additional hydrogen. The resulting high-temperature shift flow 62 is then introduced into the natural gas preheater 10 to preheat the natural gas, becoming the warm shift flow 64. In this embodiment, the warm shift flow 64 can have a temperature of approximately 322°C.

[0010] Meanwhile, boiler feedwater 72 is drawn from the boiler feedwater preparation system 70 and pressurized by a pump 80 to increase the boiler feedwater pressure to a downstream steam generation system (not shown). The pressurized boiler feedwater flow 82 (approximately 106°C, 60 barg) is then heated in a third heat exchanger 90 using heat from the hot shift flow 64 to produce a high-temperature boiler feedwater flow 92 of approximately 221°C and a lower-temperature shift gas flow 94. The high-temperature boiler feedwater flow 92 can be used to generate steam in a downstream steam generation system (not shown).

[0011] Natural gas typically contains nitrogen, but this molecular nitrogen does not cause serious nitride formation in steel. Therefore, existing SMRs are not designed to account for this unexpected situation.

[0012] The materials currently used in the raw material pretreatment and preheating sections of the SMR plant are carbon steel (CS), CrMo, and stainless steel (SS). In other words, all the materials used contain alloying elements that can easily form nitrides, such as iron and chromium. Furthermore, most of the process equipment in the synthesis gas production unit operates at temperatures far above 400°C. Therefore, simply switching the raw material from hydrocarbons to ammonia in existing hydrogen production facilities is not practical.

[0013] Process simulations of the ammonia decomposition reaction within the proposed pressure range, taking into account the above temperature constraints, showed that the ammonia conversion rate was in the range of 90% to 99.8%. The unconverted ammonia content was in the range of 0.1 to 5.0 mol%, which is below the threshold that would damage downstream equipment.

[0014] While downstream equipment is unlikely to be negatively affected by these shortcomings, upstream equipment in an SMR reactor is more likely to be negatively affected because the supply flow is almost 100% ammonia.

[0015] Therefore, in this field of technology, there is a need to provide industrial equipment that can efficiently produce hydrogen from ammonia, particularly by modifying existing hydrogen production industrial equipment to produce hydrogen from ammonia supply gas while preventing or at least minimizing the problem of embrittlement during operation. [Overview of the Initiative] [Means for solving the problem]

[0016] The present invention relates to an apparatus and method that satisfies at least one of these needs. In a particular embodiment of the present invention, a method for producing hydrogen by ammonia decomposition in an existing steam methane reformer (SMR) is provided. The SMR may include a furnace and a pressure swing adsorption (PSA) unit, the furnace having a plurality of SMR tubes and a plurality of burners. The method for producing hydrogen may include the steps of: supplying a gas stream essentially composed of ammonia at a selected lowest temperature; introducing the gas stream into the SMR tubes of the furnace under conditions effective for catalytic decomposition of ammonia, thereby forming a crude stream containing hydrogen, nitrogen and unreacted ammonia; and introducing the crude stream into a PSA unit to produce a hydrogen product stream and a PSA off-gas.

[0017] In certain embodiments, this minimum temperature is a function of pressure. The ammonia temperature can be set to a temperature at which ammonia remains in a gaseous state (preferably with a 20°C margin) to avoid condensation at low temperatures. Higher pressures result in higher temperatures. In certain embodiments, 100°C, corresponding to about 65 bara, can be a suitable low-temperature option. Ammonia decomposition can be designed to this pressure, or even higher, but is typically carried out at lower pressures of about 55 bara. This means that 100°C is a safe minimum temperature for most applications.

[0018] In an optional embodiment of the hydrogen production method, Existing SMRs will be modified to further include ammonia storage containers and ammonia feed flow pumps; Step (a) further comprises: removing ammonia from an ammonia storage container; pumping the ammonia in an ammonia supply flow pump to a pressure of 25-60 bar(g); and then vaporizing the ammonia to obtain a gaseous flow; The existing SMR is modified to include an ammonia vaporizer, in which ammonia is vaporized to form a gas flow, and the gas flow in step (a) is connected to the existing SMR's feed flow piping or feed flow distribution system, the feed flow piping and feed flow distribution system being located immediately upstream of the SMR pipe; The existing SMR will be modified to include additional new equipment selected from the group consisting of ammonia vaporizers, ammonia exchangers, ammonia preheaters, ammonia pre-reactors, and combinations thereof, and this new equipment will be located upstream of the SMR tube and downstream of the ammonia feed flow pump; • The existing SMR includes an existing feed-flow superheating section located upstream of the SMR pipe, in which ammonia is vaporized; Ammonia is vaporized using heat supplied by electricity, steam, coarse flow, and / or exhaust gas flow; Ammonia is vaporized and preheated to below 450°C, preferably below 350°C, more preferably below 300°C; • Crude flow contains less than 5.0 mol% unreacted ammonia; Conditions effective for catalytic decomposition of ammonia include a pressure of 15-80 bar, preferably 20-60 bar, and a temperature of 600-850°C, preferably 650-750°C; and / or The gas flow in step (a) is supplied from a pressurized gaseous ammonia supply flow received from outside the existing SMR.

[0019] In another embodiment, a method is provided for modifying an existing steam methane reformer (SMR) for ammonia decomposition. In this embodiment, the existing SMR may include a pre-reformer, a desulfurization unit, a furnace, a waste heat recovery section, a water-gas shift reactor, a pressure swing adsorption (PSA) unit, and the furnace having a plurality of SMR tubes and a plurality of burners. In a particular embodiment, the method may include the steps of preparing the existing SMR; taking the desulfurization unit offline so that fluid does not pass through the desulfurization unit during operation; taking the pre-reformer offline so that fluid does not pass through the pre-reformer during operation; and adding means for supplying a gaseous ammonia flow to the SMR tubes.

[0020] In an optional embodiment of the method for modifying an existing SMR, The means for supplying a gaseous ammonia flow includes an ammonia storage container, an ammonia supply flow pump, and means for vaporizing the ammonia supplied from the ammonia storage container; The means for vaporizing ammonia further include new equipment selected from the group consisting of ammonia vaporizers, ammonia exchangers, ammonia preheaters, ammonia prereactors, and combinations thereof, the new equipment being located upstream of the SMR pipe and downstream of the ammonia supply flow pump; The means for vaporizing ammonia further includes an existing feed-flow superheating section located upstream of the SMR tube, the existing feed-flow superheating section being modified by treating the inner surface of the existing feed-flow superheating section to improve nitriding resistance; and / or The step of treating the inner surface of an existing supply flow superheating section includes a process selected from the group consisting of (1) applying a protective liner material mechanically bonded to the inner surface, (2) providing an aluminized layer to the inner surface, and (3) providing a diffusion barrier layer in combination with the aluminized layer, wherein the diffusion barrier layer is positioned between the inner surface and the aluminized layer.

[0021] In another embodiment, an apparatus for producing hydrogen by ammonia decomposition using a modified steam methane reformer (SMR) is provided. The apparatus can include means for supplying a pressurized gaseous ammonia stream to a plurality of reaction tubes; a furnace having the plurality of reaction tubes and a plurality of burners, the furnace being configured to catalytically decompose ammonia in the reaction tubes to produce a raw process gas and an exhaust gas; a plurality of waste heat recovery sections; and a pressure swing adsorption (PSA) unit disposed downstream of the furnace, the PSA unit being configured to receive the raw process gas or a gas obtained therefrom and produce a hydrogen product stream and a PSA off-gas.

[0022] In an optional embodiment of the apparatus, · the means for supplying a pressurized gaseous ammonia stream to the plurality of reaction tubes includes an ammonia storage container and an ammonia pump; · the means for supplying a pressurized gaseous ammonia stream to the plurality of reaction tubes further includes an ammonia vaporizer, wherein the ammonia is vaporized in the ammonia vaporizer to form a pressurized gaseous ammonia stream, and the pressurized gaseous ammonia stream is connected to an existing SMR feed stream piping and / or a feed stream distribution system, which is disposed immediately upstream of the SMR tubes; · the means for supplying a pressurized gaseous ammonia stream to the plurality of reaction tubes further includes new equipment selected from the group consisting of an ammonia vaporizer, an ammonia exchanger, an ammonia preheater, an ammonia pre-reactor, and combinations thereof, the new equipment being disposed upstream of the SMR tubes and downstream of the ammonia feed stream pump; · the ammonia vaporizer is heated using electricity, steam, a raw stream, and / or an exhaust gas stream; · the ammonia vaporizer is configured to vaporize and preheat ammonia at a temperature less than 450°C, preferably less than 350°C, more preferably less than 300°C; · the apparatus further includes a waste heat recovery section, and the means for supplying a pressurized gaseous ammonia stream to the plurality of reaction tubes further includes heating the pressurized ammonia from the ammonia pump in the waste heat recovery section to form a pressurized gaseous ammonia stream. ·The furnace is configured to operate at a pressure of 15 - 80 bar, preferably 20 - 60 bar, more preferably 20 - 35 bar, and a temperature of 600 - 850 °C, preferably 650 - 750 °C; ·The means for supplying the pressurized gaseous ammonia stream to the plurality of reaction tubes includes pipes made of a nitridation-resistant material (Alloy 600 or 625 series, Ni-based metal or Ni content exceeding 30%) or pipes having a nitridation protection layer on the inner surface of the pipes; ·The nitridation protection layer is selected from the group consisting of a protective liner material mechanically bonded to the inner surface, an aluminized layer provided on the inner surface, a diffusion barrier layer combined with the aluminized layer provided on the inner surface, and a weld overlay provided on the inner surface, and the diffusion barrier layer is disposed between the inner surface and the aluminized layer; and / or ·The plurality of catalyst tubes includes a nitridation protection layer on the inner surface of the reaction tubes.

[0023] These and other features, aspects, and advantages of the present invention will be more deeply understood by reference to the following description, claims, and the accompanying drawings. However, it should be noted that the drawings merely illustrate some embodiments of the present invention, and thus the present invention may also admit other equally effective embodiments, and the drawings should not be regarded as limiting the scope of the present invention.

Brief Description of the Drawings

[0024] [Figure 1] Figure 1 shows an embodiment of a steam methane reformer facility according to an embodiment of the prior art. [Figure 2] Figure 2 is a simplified schematic diagram of an overall scheme for catalytic decomposition of ammonia to produce hydrogen according to an embodiment of the present invention. [Figure 3] Figure 3 shows an embodiment of the present invention. [Figure 4] Figure 4 shows the layout of equipment for an embodiment of the present invention. [Figure 5] Figure 5 shows another embodiment of the present invention. [Figure 6]Figure 6 shows another embodiment of the present invention. [Figure 7] Figure 7 shows another embodiment of the present invention. [Figure 8] Figure 8 shows another embodiment of the present invention. [Figure 9] Figure 9 shows another embodiment of the present invention. [Figure 10] Figure 10 shows another embodiment of the present invention. [Modes for carrying out the invention]

[0025] While the present invention is described in relation to several embodiments, it will be understood that these are not intended to limit the invention to these embodiments. Rather, they are intended to cover all alternative forms, modifications, and equivalents that may fall within the spirit and scope of the invention as defined by the appended claims.

[0026] Naturally, it will be understood that in developing such actual embodiments, many implementation-specific decisions will need to be made, differing from implementation to implementation, such as compliance with system-related and business-related constraints, in order to achieve the specific goals of the developers. Furthermore, it will be understood that while such development efforts may be complex and time-consuming, they are still routine tasks for those skilled in the art who benefit from this disclosure.

[0027] For the reasons stated above, decarbonization in NG-based H2 production is neither simple nor easy, but it is preferable to fully decarbonize and operate existing plants based on replacing fossil fuels with ammonia. Ammonia itself can be produced from various sources and can be easily transported worldwide by ship, pipeline, or truck. Ammonia does not contain carbon atoms. Therefore, using ammonia in SMRs achieves intrinsic and complete decarbonization of the process. However, replacing methane with NH3 is not easy and requires process modifications to ensure safe and reliable operation. The use of NH3 has several significant advantages compared to NG-based SMRs and newly constructed NH3 decomposition units: • CO2 emissions from the plant are reduced completely or partially. • Additional infrastructure for CCS (e.g., CC units, steam supply, CO2 storage, CO2 pipelines, tanks, CO2 vessels, isolation facilities, etc.) is not required at the hydrogen usage site. NH3 is already traded worldwide, and its manufacturing and transportation are well-known, therefore no additional legal regulations are required. • Because existing SMR assets can be utilized, investment costs can be reduced, and deployment can be faster compared to new greenfield plants. • In existing areas, existing infrastructure and connections to customers can be utilized. In emerging markets, H2 is typically used in new applications that do not normally require steam. When NH3 is used in SMRs, the lower heat load required for the NH3 decomposition reaction reduces the amount of steam produced as a byproduct. This is beneficial and improves the overall efficiency of the plant compared to plants designed for many steam deliveries. By mitigating typical challenges in SMRs, such as coking and metal dust corrosion, the operating range of the plant is extended.

[0028] In principle, methane and NH3 have several similarities and differences. Ammonia can be decomposed into N2 and H2 in an endothermic reaction (see the reaction equation below). The same is true for methane, but in this case the decomposition products are carbon and H2. The formation of solid carbon causes problems (clogging, fouling, handling of solids). Therefore, methane is usually converted by reforming reactions, i.e., reactions that include water as a reagent to suppress carbon formation. In this respect, NH3 decomposition is much easier and does not require the addition of water vapor. NH3 decomposition

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[0029] In an improved SMR process using a 100% NH3 feedstream, several process components become unnecessary, such as desulfurization, pre-reformers, water-gas shift sections, and condensate systems (see scheme).

[0030] This allows for bypassing the individual catalyst containers, eliminating the need for periodic monitoring and catalyst replacement, resulting in reduced OPEX and improved reliability. Furthermore, it reduces the overall pressure drop within the system.

[0031] On the other hand, this process may include several additional units for NH3 processing. Some non-limiting examples include an NH3 storage unit, a feed flow supply unit (pump + vaporizer), and an optional additional water washing unit downstream of the reactor.

[0032] The ammonia decomposition reaction requires far less heat per hydrogen molecule than the steam methane reforming reaction. When 100% ammonia is the raw material, process steam is unnecessary because it is not a problem due to excessively high temperatures or heat fluxes causing carbon formation in hydrocarbons, or because a lack of process steam is not an issue. This allows for further reductions in the required process heat, or enables the conversion of more ammonia into hydrogen, thereby increasing the hydrogen output of existing units.

[0033] In a standard steam reforming process, the addition of process steam generates significant waste heat on both the process and combustion sides, reducing the plant's thermal efficiency. The process steam is cooled and condensed in a synthesis gas cooling train to preheat the raw materials and other process flows.

[0034] In the case of a 100% ammonia feedstock, reducing and minimizing process steam is desirable to maximize thermal efficiency and the ratio of hydrogen products to ammonia feedflow. As a result, far less waste heat can be utilized on the process side of the unit, which is insufficient for preheating and vaporizing the ammonia feedstock.

[0035] At the same time, because less heat is required for the decomposition of ammonia, less waste heat is contained in the exhaust gas, making it usable only at lower temperatures.

[0036] A flow chart for H2 production based purely on NH3 is shown in Figure 1. Ammonia is stored in a suitable storage container 1, preferably as a cooling fluid at -33°C and atmospheric pressure, or at high pressure and ambient temperature. The liquid NH3 feed stream enters the SMR system against the system pressure (5-40 bar) by a liquid pump 3, bypassing any pre-treatment units 20, 40 (hydrogenation, H2S adsorption, pre-reforming) that may be present there, and is preheated in NH3 preheating sections 10, 30, where the NH3 is vaporized and heated to suitable inlet conditions of 300-650°C. If the calorific value of the waste gas from the PSA is insufficient to heat the reaction, a portion of the NH3 stream can be used as fuel 45 for the SMR furnace 50. Furthermore, a portion of the H2 or synthesis gas stream can also be used as fuel to eliminate bottlenecks in existing heat exchangers. Preheating can be performed using the high-temperature stream in the waste heat recovery sections 10, 30, 90. For example, exhaust gas 54 can supply thermal energy to the waste heat recovery section 30. This feature is not shown in the drawings to avoid further complexity, but the present invention is not limited to what is explicitly shown in the drawings.

[0037] The preheated NH3 feed stream 43 is sent to the SMR reactor 50, a reactor configuration including numerous tubular reactors placed in a heating furnace. These tubes can be packed with standard reforming catalysts, such as Al2O3-supported Ni-based catalysts. In certain embodiments, the catalyst can be replaced with a more active catalyst system, particularly to eliminate bottlenecks. Inside the SMR tubes, the NH3 feed stream is converted into a product mixture at a temperature of 500–900°C. The gas mixture 53 contains N2 and H2, as well as trace amounts of unconverted NH3 (e.g., up to approximately 5 vol%). The heat required for this reaction is supplied indirectly from combustion in the firebox through the SMR tube walls. The high-temperature gas mixture 53 is cooled by evaporation of water in a continuous heat exchanger 10 and process gas boiler 90. This generates steam as a byproduct. Steam generation can be controlled by adjusting the load on the SMR firebox. For this purpose, it may be necessary to burn additional NH3.

[0038] In the illustrated embodiment, the gas mixture 53 bypasses the existing water-gas shift reactor 60 and is cooled in a series of waste heat recovery sections. After cooling, condensate 96 is removed from the cooled gas mixture 95, and the resulting dry gas mixture 101 is then sent to a water scrub tower. The water scrub tower is configured to remove unreacted ammonia gas from the dry gas mixture by using pressurized water 84 (preferably supplied from boiler feedwater 70). In one embodiment, the processing section 102 can be a dedicated container added to an existing SMR system.

[0039] In one embodiment, the processing section may include a scrubbing tower located in an existing synthesis gas cooling section between the BFW preheater outlet and the PSA inlet, i.e., below the dew point of the process gas 101, preferably between the final cooler and the PSA inlet. High-pressure boiler feedwater 84 from an existing unit 70 is preferably used for water addition.

[0040] The treatment section can be designed so that the inlet ammonia content is in the range of 0.2 to 5 mol%. Since ammonia is highly soluble in water, the water scrubbing tower can be designed to reduce the residual ammonia concentration in the feedstream to the PSA to less than 100 ppm, preferably less than 20 ppm, and to supply a mixture of hydrogen and nitrogen to the existing PSA.

[0041] The generated gas 103 is sent to a pressure swing adsorption (PSA), where H2 is purified to a purity typically exceeding 99.5%. The residual gas stream (off-gas) contains H2, N2, and NH3. The scrub tower outflow stream 104 is taken out of the water scrub tower. In an optional embodiment, at least a portion 88 can be mixed with the exhaust gas 54 from the SMR reactor 50.

[0042] In embodiments not shown, an off-gas stream from the PSA can be supplied to the burner of the SMR to provide the heat necessary for the NH3 decomposition reaction. The presence of a mixture of H2 and NH3 as combustible components is beneficial because the rapid combustion of H2 and the slower combustion of NH3 balance each other, allowing for the use of modern burners. In certain embodiments, at least 14% H2 is present in the off-gas. The literature states that 7-10% H2 is sufficient to allow smooth co-combustion of NH3 and H2. This also allows for the additional combustion of NH3 as fuel without being hindered by the problem of the slower combustion of NH3.

[0043] In another embodiment not shown, the off-gas can be sent back to the SMR reaction tube to more completely convert residual ammonia while also recovering additional residual hydrogen.

[0044] As described in the background technology section, ammonia can cause embrittlement problems in systems, particularly at high temperatures. Specific embodiments of the present invention seek to minimize these problems by utilizing advantageous connection points with existing SMR equipment, which allows for a reduction in CAPEX during modification procedures.

[0045] Figure 3 shows a simplified schematic diagram of one embodiment of the present invention. Ammonia 22 is drawn from an ammonia supply source 1, pressurized (preferably to a pressure of 5 to 40 bar) in an ammonia pump 3, and then heated in a waste heat recovery section 30 to form preheated ammonia 42. As described above, the preheated ammonia is sent to the reaction tubes of the SMR using a supply header 47, and the ammonia gas 42 is distributed to all the relevant reaction tubes. Those skilled in the art will understand that a second header can also be used to distribute the preheated ammonia 42 to multiple burners in the SMR. This feature is not shown in the drawings to avoid over-illustrating.

[0046] In certain embodiments, the supply header is positioned directly above the multiple pipes, preferably within 10 meters.

[0047] After the catalytic conversion of ammonia, the resulting mixed gas 53 is recovered from the reaction tube and then sent out for further processing. Figure 2 shows a non-limiting example of further processing.

[0048] The exhaust gas 54 (i.e., combustion products) can be retransmitted from the combustion chamber to a waste heat recovery section 30 (i.e., a series of heat exchangers), where the heat is used for preheating and superheating various flows (e.g., combustion air, fuel, and feed flows). Untreated exhaust gas, which may contain NOx, can optionally be sent to an exhaust gas treatment section 5 to form treated exhaust gas. In certain embodiments, the treatment section 5 may include a DeNOx unit and / or a selective catalytic reformer (SCR). Ammonia 99 can be used in both the DeNOx unit and the SCR.

[0049] Lines 25 and 35 represent suitable connection points that conform to specific embodiments of the present invention. Both connection points 25 and 35 allow bypassing most existing units (e.g., the desulfurization unit 20 and the pre-reformer 40), thereby significantly reducing potential embrittlement issues.

[0050] The first connection point 25 can be located upstream of the first or second superheater coil, which is part of the waste heat recovery section 30. The second connection point 35 can be located at the same position as the supply flow cross header 47, or just upstream of it. Using any of these connection points largely eliminates the need to modify piping or equipment with appropriate surface treatment.

[0051] In additional embodiments, the pressure and temperature within the reaction tube can be selected such that the ammonia content in the mixed gas 53 downstream of the reaction tube is less than 2.5 mol%, thereby significantly reducing the risk of nitride formation and embrittlement problems in downstream equipment. The appropriate pressure can be 15-40 bar(a), preferably 20-35 bar(a), while the appropriate temperature can be 600-850°C, preferably 650-750°C.

[0052] Based on the above, in certain embodiments of the present invention, additional equipment such as an ammonia holding container or tank and an ammonia supply flow pump may be included to modify an existing SMR. This is particularly true when the ammonia supply flow can be supplied at sufficient pressure and in vaporized form. When connection point 35 is used, it is preferable to heat the ammonia flow at a point between the ammonia pump and the supply header 47.

[0053] Figure 4 shows a schematic diagram of additional equipment that may be included in the modified SMR facility. This embodiment may include an ammonia holding container 710, an ammonia feed flow pump 3, an ammonia preheater 715, an ammonia exchanger 725, an ammonia vaporizer 730, and a pre-reactor 740.

[0054] The ammonia vaporizer 730 and preheater 715 can be heated by electric heating, steam heating, or by heating by the process flow downstream of an existing process gas boiler, or by heating by the exhaust gas flow downstream of an existing exhaust gas boiler. The temperature range of the high-temperature medium in the preheating / vaporization step can be less than 400°C, preferably less than 300°C. The ammonia exchanger 730 and / or pre-reactor 740 can be arranged as shown in Figure 4.

[0055] In the illustrated embodiment, a first portion of liquid ammonia 702 is introduced into an ammonia holding container 710 and then sent to a DeNox unit via line 714. A second portion of liquid ammonia 704 is compressed by an ammonia supply flow pump 3. After compression, the compressed liquid ammonia can be connected to a modified SMR plant via line 713 from connection point 25, or to connection point 35. Since connection point 25 is upstream of an existing heater, the pressurized liquid ammonia 713 does not separate the heating means from the ammonia preheater 715, ammonia exchanger 725, or ammonia vaporizer 730.

[0056] In certain embodiments where connection point 35 is desired (e.g., immediately upstream of the SMR tube), compressed liquid ammonia 712 can be heated in ammonia preheater 715 and ammonia exchanger 725, then vaporized in ammonia vaporizer 730, and subsequently converted by a pre-reaction in ammonia pre-reactor 740. The resulting pre-reacted ammonia stream 742 is used to supply preheating energy in ammonia exchanger 725 and then sent to connection point 35 via line 744.

[0057] Notwithstanding the foregoing, those skilled in the art will recognize that the equipment shown in Figure 4 is not essential in certain embodiments of the present invention. Specifically, if ammonia is supplied in a pressurized vapor state, all additional equipment can be omitted. This means that the pressurization and vaporization process steps are performed outside the battery limits of the existing unit.

[0058] In certain embodiments, a nitride protective layer can be provided on specific parts of the equipment. The nitride protective layer can be selected from the group consisting of a protective liner material mechanically bonded to the inner surface, an aluminized layer provided on the inner surface, a diffusion barrier layer combined with the aluminized layer provided on the inner surface, and a welded overlay provided on the inner surface, the diffusion barrier layer being positioned between the inner surface and the aluminized layer. A more detailed description of acceptable nitride protective layers is found in concurrently pending U.S. Patent Application No. 17 / 896,026, filed on 25 August 2022, which is incorporated herein by reference in its entirety.

[0059] Ammonia degradation in existing SMRs presents several challenges: 1) Because the calorific value of ammonia (18.6 MJ / kg) is lower than that of natural gas (42-55 MJ / kg), the ratio of fuel to air flow in the furnace increases significantly at a given load; 2) Existing heat exchangers may not have the necessary heat exchange surface area; 3) As reported in various studies, temperatures exceeding 500°C are required for catalytic NH3 decomposition (Wang et al., Ammonia as hydrogen carrier for transportation; investigation of the ammonia exhaust gas fuel reforming, p. 9908). Therefore, it is desirable to reach this T at the inlet of the reformer / decomposition unit. Switching from steam methane reforming to NH3 decomposition involves a decrease in load and temperature, which can overturn thermal integration and make it difficult to reach this T threshold; 4) Undesirable nitride formation becomes more pronounced at temperatures above 600°C. At high temperatures inside the SMR reformer (typically above 850°C at the outlet), nitriding can become a significant problem; 5) If the layout of existing equipment is not optimized, ammonia may be consumed in excess; 6) There are differences between SMRs optimized for H2 and water vapor generation and NH3 decomposition systems that can actually operate completely without water vapor.

[0060] The above problems can be overcome by various alternative embodiments of the present invention. For example, in one embodiment where the decomposition T is 800°C, a portion of the H2 products can be used as fuel (H2 fuel conversion), thereby meeting the original design flow rates of the furnace and exhaust gas system and improving compatibility with existing heat exchangers (problems 1 and 2).

[0061] However, since it is difficult to reach a temperature of at least 500°C T at the inlet of the decomposition unit, H2 fuel conversion alone is insufficient. To overcome this problem, one or more additional heat exchangers can be added. In certain embodiments, a first heat exchanger is installed upstream of the PSA on the converted H2 to vaporize ammonia using low-grade heat (approximately 140°C) while simultaneously using liquid ammonia as a low-temperature cooling medium for cooling the final untreated H2. This low-grade heat is conventionally considered waste heat from SMRs (Problem 3).

[0062] Optionally, a second heat exchanger can be installed in one of the SMR steam systems, either immediately downstream of the existing boiler or downstream of the steam superheater. This second heat exchanger optimizes heat integration to the SMR without interfering with the main process, resulting in a reduction in overall NH3 consumption (Problem 5).

[0063] Using H2 as the primary fuel is more difficult than burning natural gas, but it is generally well understood, given some experience using it as a PSA off-gas fuel in SMRs. In contrast to NH3 combustion, which is difficult due to its low flame velocity, H2 combustion burns much faster than natural gas or NH3, so this is not a problem with H2 combustion.

[0064] In another embodiment where the decomposition T is 600°C, a similar configuration has proven advantageous: limited H2 fueling allows for adaptation to existing heat exchanger configurations, thereby reducing the load and space velocity of the NH3 decomposition unit; and by adding heat exchangers to the crude H2 upstream of the PSA and to the steam system, ammonia consumption can be reduced by 5-10% (Problem 5) while still reaching the required 500°C decomposition unit inlet T (Problem 3).

[0065] In this embodiment, H2 is co-fired with NH3 (approximately 50:50 at LHV), producing a fuel mixture with more manageable combustion characteristics than the combustion of pure H2 or pure NH3. Furthermore, this low decomposition T significantly reduces the risk of material degradation due to nitriding (Problem 4).

[0066] Finally, an advantage of these aforementioned embodiments is that the volumetric flow rate of the process line is lower than that of SMRs. When green ammonia is used and an existing plant is connected to an H2 pipeline, the production of green H2 can be increased beyond what is possible with steam methane reforming, and the overall carbon intensity of H2 on the pipeline can be improved by reducing the production of another SMR on the same pipeline.

[0067] Case 1a, the baseline case for SMR, is shown in Figure 5. Process natural gas 100 is preheated in heat exchanger 150, desulfurized in 151, mixed with steam 103, and then heated to approximately 650°C in reformer feedstream preheater 152. The steam methane reforming reaction takes place in the catalyst-filled tube of reformer 153 at an outlet reforming temperature of 850-900°C. The high-temperature synthesis gas is used to evaporate steam in process gas boilers 154 / 169 and then sent to water-gas shift reactor 155. The shifted synthesis gas 107 is used to preheat natural gas in 156 / 150 and then cooled to approximately 110°C in boiler feedwater heaters 157 / 168. The synthesis gas 109 is then cooled by an air cooler and a final cooler in a heat exchanger 158, and then sent to a PSA from which a high-purity (99.9%) H2 stream 111 is recovered.

[0068] The PSA off-gas 112, consisting of CO2, H2, and unreacted CO and CH4, is sent to the burner of the reformer 162, where it is mixed and burned with natural gas fuel 113 and high-temperature combustion air 116. Part of the heat generated in the furnace is used in the endothermic reforming reaction in 153. The residual heat in the exhaust gas 117 is then used sequentially for heating the reformer feedstream in 163 / 152, superheating the steam in 164 / 170, heating the combustion air in 165 / 161, generating steam in the exhaust gas boiler in 166 / 169, and preheating the combustion air in 167 / 160.

[0069] In this particular SMR, for simplification, a common steam system for the process gas and exhaust gas is considered. Boiler feedwater 123 is preheated by the shift synthesis gas at 168, vaporized by the process gas 105 and exhaust gas 119 in the boiler 169, and superheated by the shift synthesis gas 108 at 170. The required amount of steam 127 is then mixed with the process natural gas 102, and the remaining steam 126 is released as a byproduct.

[0070] In Case 1b shown in Figure 6, NH3 is used as process feedstock 200 and fuel 211. The desulfurization unit 151 and water-gas shift reactor 155 are no longer needed and are therefore bypassed. The small amount of steam generated can be used as process steam 225 / 202 to reduce the risk of corrosion due to nitriding downstream of the process. The arrangement of the remaining heat exchangers is the same as in Case 1a.

[0071] The amount of H2 generated is consistent with the standard case for the SMR, and the amount of water vapor generated is also similar to the standard case, but here almost all of the generated water vapor is released. However, compatibility with existing SMRs is very low (see Table 1). Since the LHV of NH3 as fuel is lower than that of NG, the molar flow rate of NH3 is considerably higher, and as a result, the combustion air flow rate and exhaust gas volumetric flow rate at the reformer outlet increased by 2.5 times and 2.4 times, respectively. The required heat exchange area is more than twice as large for heat exchangers E-F1 "Reformer feedflow heater", E-F4 "Hot air combustion heater", E-F5 "Exhaust gas boiler", and E-F6 "Cold air combustion heater" (Table 1).

[0072] In another embodiment of Case 1c, the same configuration as in Figure 6 is maintained, but the decomposition temperature is lowered to 800°C and the high-temperature combustion air temperature is raised to 480°C in an attempt to reduce the amount of NH3 required as fuel. The increase in combustion air temperature significantly reduces the amount of water vapor released compared to Case 1b, and the water vapor release flow rate is similar to that of the reference case. The molar flow rate of NH3 fuel, the volumetric flow rate of the exhaust gas, and the mass flow rate of the combustion air are significantly lower compared to Case 1b, but are still too high compared to the reference case. The required heat exchange area is suitable for the E-F5 "exhaust gas boiler," but E-F1 and E-F6 are still below the standard, and suitability for E-F4 is worsened.

[0073] In case 1d (see Figure 7), the same configuration as in cases 1b and 1c is maintained, but a portion of the H2 product 326 is diverted for use as fuel. The combustion air and exhaust gas flow rates closely match those of the SMR reference case. Here, the high-temperature combustion air temperature can be lowered, and as a result, E-F4 better conforms to the reference case. However, at exhaust gas temperatures lower than those of the SMR, E-F3 falls below the standard, and E-F1 also falls below the standard despite a decrease in the decomposition unit inlet T. In Figure 7, a portion of the refined H2 product recovered from the PSA can preferably be fed as fuel.

[0074] Alternatively, a similar "H2 fuelization" effect can be achieved by removing a portion of the crude H2 upstream of the PSA, or by modifying the PSA to reduce the amount of H2 recovered so that the required amount of H2 for fuel is included in the PSA off-gas 310. Table 1 shows the molar flow rate of H2 delivered to the fuel (excluding the molar flow rate of H2 already present in the PSA off-gas) corresponding to the configuration shown in Figure 7. Table 1 also includes the "H2 fuel ratio" ηH2f to consider alternative configurations where the contribution of H2 to the fuel is upstream of the PSA or via the PSA off-gas. ηH2f is defined as follows:

number

[0075] In Case 1e (see Figure 8), a new heat exchanger 457 and an additional NH3 heater 450 are added to the crude H2 upstream of the PSA. This is because the heat that was previously considered waste heat in the SMR can now be used here to vaporize process NH3. This further improves heat integration, increases steam release, and improves the E-F3 conformance to the baseline case. The downside is that E-F1 is still below baseline despite the low decomposition unit inlet T of 400°C. At decomposition unit inlet T below 500°C, the rate of the decomposition reaction in the initial part of the reforming tube may be insufficient, in which case it can be effectively used as a heat exchanger section rather than a reactor.

[0076] In Case 1f (see Figure 9), an additional heat exchanger 571 / 552 is added, using part of the steam generator 529 to further vaporize and preheat the raw material NH3. Although steam emissions are reduced, heat integration is significantly improved. The amount of H2 required as fuel is lower compared to Case 1e, and overall NH3 consumption is reduced. The decomposition unit inlet temperature T exceeds the threshold of 500°C, and none of the heat exchangers fall below the standard, thus satisfying compliance with the standard case.

[0077] Furthermore, if an increase in H2 generation capacity beyond the original SMR is desired, the heat exchanger bottleneck will be located at E-F1. However, the load on E-F1 can be reduced accordingly by simply increasing the load on the new heat exchanger 571 of the steam system.

[0078] Figure 10 shows another similar configuration. In an SMR, the chimney exhaust gas (flow 122 in Figure 5) must be kept above the dew point of sulfuric acid to prevent corrosion, resulting in the exhaust gas being discharged at approximately 140°C T. When NH3 is used as the raw material and fuel, this constraint does not apply, and a heat exchanger 668 / 651 can be installed to utilize this low-grade heat in the exhaust gas to vaporize the NH3 feed stream. The advantage of this is that the amount of steam released is not reduced, although it does not offer the flexibility provided by the heat exchanger in the steam system. In such cases, if the crude H2609 and exhaust gas 623 are at equivalent temperature levels, the heat exchanger / NH3 vaporizers 658 / 650 and 668 / 651 can be integrated into a single unit.

[0079] One major uncertainty in decomposing NH3 using existing SMRs is the achievable exhaust gas temperature at the decomposition unit outlet (the so-called "bridge wall temperature"). This can affect the thermal integration of the entire process and is primarily governed by the overall heat transfer within the furnace and SMR tubes. Cases 1g and 1h use the same configuration as case 1f, but with bridge wall temperatures varying by -50°C and +50°C, respectively. As shown in Table 1, these variations can be easily compensated for by adjusting the proportion of H2 products used as fuel, leaving the remaining key process parameters and required heat exchange area unaffected. Thus, this H2 fuel configuration provides robust control parameters to ensure that process parameters remain within acceptable limits.

[0080] Undesirable nitride formation becomes more pronounced at temperatures above 600°C. At decomposition temperatures of 800°C, nitriding becomes a significant problem, potentially requiring costly mitigation measures (such as those described above). Furthermore, higher decomposition temperatures mean a greater load on the reformer / decomposition unit, thus increasing overall NH3 consumption.

[0081] In Case 2b (see Table 2), the configuration shown in Figure 9 is reproduced, using H2 as fuel, adding heat exchangers 558 / 550 to the crude H2, and adding 571 / 552 to the steam system to vaporize and preheat the raw material NH3. However, the decomposition T is 600°C. Compared to Case 1f, more NH3 is required as fuel, but the required proportion of H2 products sent to the fuel is significantly reduced, resulting in a reduction in overall NH3 consumption. Here again, this flexible configuration allows the requirements for process parameters (decomposition unit inlet T > 500°C) and heat exchanger area to be met despite a significantly lower decomposition T compared to the SMR. Similarly, in Cases 2c and 2d, where the bridge wall temperature is changed by -50°C and +50°C, respectively, it is shown that the changes and uncertainties in bridge wall temperature can be easily compensated for by adjusting the amount of H2 products used as fuel.

[0082] [Table 1]

[0083] [Table 2]

[0084] In this specification, “immediately upstream of the SMR pipe” is intended to encompass a location where the supply flow distribution system is directly above the multiple pipes, or up to 10 m above based on the length of the pigtail connecting the distribution system (manifold) to the SMR pipe.

[0085] While the present invention has been described in conjunction with specific embodiments, it will be obvious to those skilled in the art, based on the foregoing description, that alternative, modified, and variant forms are obvious. Therefore, the present invention is intended to encompass all such alternative, modified, and variant forms that fall within the spirit and broad scope of the appended claims. The present invention may be implemented appropriately incorporating, consisting of, or essentially consisting of the disclosed elements, without any undisclosed elements. Furthermore, terms indicating order, such as "first" and "second," should be understood as illustrative rather than restrictive. For example, those skilled in the art will recognize that certain steps or apparatus can be integrated into a single step / apparatus.

[0086] The singular forms "a," "an," and "the" refer to multiple objects unless the context clearly indicates otherwise. The term "about / approximately" in relation to a specific value includes ±10% of that value unless the context clearly indicates otherwise.

[0087] "Optional" or "optionally" means that the event or situation described thereafter may or may not occur. This description includes both instances where the event or situation occurs and instances where it does not.

[0088] In this specification, a range may be expressed as "about" one specific value and / or "about" another specific value. Where such a range is expressed, another embodiment should be understood to include one specific value and / or another specific value, as well as all combinations within the said range.

Claims

1. A method for producing hydrogen by ammonia decomposition in an existing steam methane reformer (SMR), wherein the SMR includes a furnace (50) and a pressure swing adsorption (PSA) unit, and the furnace (50) has a plurality of SMR tubes and a plurality of burners, and the method is (a) A step of supplying a gas stream (43) which is essentially made up of ammonia at a temperature of at least 100°C; (b) The step of introducing the gas flow (43) into the SMR tube of the furnace (50) under conditions effective for catalytic cracking of the ammonia, thereby forming a crude flow (53) containing hydrogen, nitrogen and unreacted ammonia; and (c) A step of introducing the crude flow (53) into the PSA unit to generate a hydrogen product flow and a PSA off-gas; A method that includes this.

2. The method according to claim 1, wherein the existing SMR is modified to further include an ammonia storage container (1) and an ammonia supply flow pump (3).

3. The method according to claim 2, further comprising step (a) extracting ammonia from the ammonia storage container; pumping the ammonia in the ammonia supply flow pump (3) to a pressure of 25 to 60 bar (g); and then vaporizing (30) the ammonia to produce the gas flow (43).

4. The method according to claim 3, wherein the existing SMR is modified to further include an ammonia vaporizer (30), the ammonia is vaporized in the ammonia vaporizer to form a gas flow, the gas flow in step (a) is connected to a supply flow piping or supply flow distribution system (45) of the existing SMR, and the supply flow piping and supply flow distribution system are located immediately upstream of the SMR pipe.

5. The method according to claim 3, wherein the existing SMR is modified to further include new equipment selected from the group consisting of ammonia vaporizers (30, 730), ammonia exchangers (725), ammonia preheaters (715), ammonia prereactors (740), and combinations thereof, the new equipment being located upstream of the SMR tube and downstream of the ammonia supply flow pump.

6. The method according to claim 3, wherein the existing SMR includes an existing feed-flow superheating section located upstream of the SMR tube, and the ammonia is vaporized in the existing feed-flow superheating section.

7. The method according to claim 3, wherein the ammonia is vaporized using heat supplied by electricity, steam, the crude flow (53), and / or the exhaust gas flow (54).

8. The method according to claim 3, wherein the ammonia is vaporized and preheated to less than 450°C, preferably less than 350°C, more preferably less than 300°C.

9. The method according to any one of claims 1 to 8, wherein the crude flow (53) contains less than 5.0 mol% unreacted ammonia.

10. The method according to any one of claims 1 to 9, wherein the conditions effective for catalytic decomposition of the ammonia include a pressure of 15 to 80 bar, preferably 20 to 60 bar, and a temperature of 600 to 850°C, preferably 650 to 750°C.

11. The method according to any one of claims 1 to 10, wherein the gas flow in step (a) is supplied from a pressurized gaseous ammonia supply flow received from outside the existing SMR.

12. A method for modifying an existing steam methane reformer (SMR) for ammonia decomposition, wherein the existing SMR includes a pre-reformer (20), a desulfurization unit (40), a furnace (50), waste heat recovery sections (10, 30, 90), a water-gas shift reactor (60), and a pressure swing adsorption (PSA) unit, and the furnace (50) has a plurality of SMR tubes and a plurality of burners, and the method is (a) the step of preparing the existing SMR; (b) Taking the desulfurization unit (40) offline so that the fluid does not pass through the desulfurization during operation; (c) The step of taking the pre-reformer (20) offline so that the fluid does not pass through the pre-reformer during operation; and (d) Adding means for supplying a gaseous ammonia flow (1, 3, 43, 45) to the SMR tube; Methods that include...

13. The method according to claim 12, wherein the means for supplying the gaseous ammonia flow includes an ammonia storage container (1), an ammonia supply flow pump (3), and means (10, 30) for vaporizing the ammonia supplied from the ammonia storage container.

14. The method according to claim 13, wherein the means for vaporizing the ammonia further includes new equipment selected from the group consisting of ammonia vaporizers (30, 730), ammonia exchangers (725), ammonia preheaters (715), ammonia prereactors (740), and combinations thereof, the new equipment being located upstream of the SMR pipe and downstream of the ammonia supply flow pump (3).

15. The method according to claim 13, wherein the means for vaporizing the ammonia further includes an existing feed-flow superheating section (30) located upstream of the SMR tube, and the existing feed-flow superheating section is modified by treating the inner surface of the existing feed-flow superheating section to improve nitriding resistance.

16. The method according to claim 13, wherein the step of treating the inner surface of the existing supply flow superheating section includes a process selected from the group consisting of (1) applying a mechanically bonded protective liner material to the inner surface, (2) providing an aluminized layer to the inner surface, and (3) providing a diffusion barrier layer in combination with the aluminized layer, wherein the diffusion barrier layer is positioned between the inner surface and the aluminized layer.

17. An apparatus for producing hydrogen by ammonia decomposition using a modified steam methane reformer (SMR), Means for supplying pressurized gaseous ammonia streams (1, 3, 43, 45) to multiple reaction tubes; A furnace (50) having a plurality of reaction tubes and a plurality of burners, configured to catalytically decompose ammonia in the reaction tubes to produce crude process gas (53) and exhaust gas; Multiple waste heat recovery sections; and A pressure swing adsorption (PSA) unit located downstream of the furnace (50), the PSA unit configured to receive the crude process gas (53) or a gas obtained therefrom, and to generate a hydrogen product stream and a PSA off-gas; A device including a device.

18. The apparatus according to claim 17, wherein the means for supplying a pressurized gaseous ammonia stream to a plurality of reaction tubes includes an ammonia storage container (1) and an ammonia pump (3).

19. The apparatus according to claim 18, wherein the means for supplying the pressurized gaseous ammonia stream to a plurality of reaction tubes further includes an ammonia vaporizer (10, 30, 730), in which ammonia is vaporized in the ammonia vaporizer to form the pressurized gaseous ammonia stream (43), the pressurized gaseous ammonia stream is connected to the existing SMR supply flow piping and / or supply flow distribution system (45), and the supply flow piping and / or supply flow distribution system is located immediately upstream of the SMR tube.

20. The apparatus according to claim 18, wherein the means for supplying the pressurized gaseous ammonia flow to a plurality of reaction tubes further includes new equipment selected from the group consisting of ammonia vaporizers (10, 30, 730), ammonia exchangers (725), ammonia preheaters (715), ammonia pre-reactors (740), and combinations thereof, the new equipment being arranged upstream of the SMR tube and downstream of the ammonia supply flow pump.

21. The apparatus according to claim 18, wherein the ammonia vaporizer (10, 30, 730) is heated using electricity, steam, coarse flow (53), and / or exhaust gas flow.

22. The apparatus according to claim 18, wherein the ammonia vaporizer (10, 30, 730) is configured to vaporize and preheat ammonia at a temperature of less than 450°C, preferably less than 350°C, and more preferably less than 300°C.

23. The apparatus according to claim 18, further comprising a waste heat recovery section (10, 30, 90), wherein means for supplying the pressurized gaseous ammonia stream to a plurality of reaction tubes further comprises heating pressurized ammonia from the ammonia pump in the waste heat recovery section to form the pressurized gaseous ammonia stream.

24. The apparatus according to claim 17, wherein the furnace (50) is configured to operate at a pressure of 15 to 80 bar, preferably 20 to 60 bar, more preferably 20 to 35 bar, and at a temperature of 600 to 850°C, preferably 650 to 750°C.

25. The apparatus according to claim 17, wherein the means for supplying the pressurized gaseous ammonia stream to a plurality of reaction tubes includes piping containing a nitridation-resistant material and / or piping having a nitridation protective layer on the inner surface of the piping.

26. The apparatus according to claim 25, wherein the nitride protective layer is selected from the group consisting of a protective liner material mechanically bonded to the inner surface, an aluminized layer provided on the inner surface, a diffusion barrier layer combined with the aluminized layer provided on the inner surface, and a welded overlay provided on the inner surface, and the diffusion barrier layer is disposed between the inner surface and the aluminized layer.

27. The apparatus according to claim 17, wherein a plurality of catalyst tubes include a nitride protective layer on the inner surface of the reaction tube.

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