A process for production of hydrogen gas

Abstract

A process for the production of a hydrogen-containing gas, such as ammonia make-up gas, wherein a first hydrocarbon feed is reformed in a main unit including a fired furnace for primary reforming, and a second hydrocarbon feed is reformed in a side unit to produce a hydrogen fuel for said fired furnace, the side unit including a pre-reformer followed by a secondary reformer.

Description

[0001] A process for production of hydrogen gas

[0002] DESCRIPTION

[0003] Field of application

[0004] The present invention concerns the field of production of a hydrogen-containing synthesis gas by steam reforming.

[0005] Prior art

[0006] A widespread technology for large scale industrial production of hydrogen is steam reforming of a suitable hydrocarbon source, such as natural gas. A known setup for steam reforming includes primary reforming followed by secondary reforming, wherein the primary reforming is performed in a fired furnace fueled by a portion of the natural gas feed, and the secondary reforming is performed in an air-fired catalytic secondary reformer. The so obtained synthesis gas, effluent from the secondary reformer, contains hydrogen and carbon oxides and is typically processed for purification including at least one or more steps of water- gas shift to convert carbon monoxide into carbon dioxide and carbon dioxide removal.

[0007] An application of noticeable interest is the production of ammonia make-up gas. The ammonia make-up gas is a gas suitable to feed an ammonia synthesis section and contains hydrogen and nitrogen in a suitable proportion around 3:1. The required amount of nitrogen may be provided by the air introduced into the secondary reformer or may be added separately when available. Many ammonia plants operate with a front-end for generation of the ammonia make-up gas based on the above-described combination of primary reforming followed by air-fired secondary reforming.

[0008] In recent years, the demand to reduce CO2 emissions has become increasingly stringent. The taxation on CO2 emissions is expected to increase dramatically in the coming years; consequently, there is a demand for new plants with low CO2 emissions as well as for an effective revamping procedure to reduce the emissions of existing front-ends based on primary reforming and secondary reforming.

[0009] In this context, efforts have been made to eliminate or reduce the considerable emission of the fuel-fired primary reformer. For example, EP 3 583 067 B1 teaches to use a portion of the hydrogen gas after CO2 removal as a fuel for the primary reformer. However, the known solutions are developed around primary reforming and oxygen-fired secondary reforming or autothermal reforming (ATR). This requires the provision of an air separation unit (ASU) which is expensive.

[0010] EP 4 279 446 discloses a plant and a process for producing hydrogen from hydrocarbons. WO 2015-067436 discloses a process for producing ammonia make-up gas and a method for revamping a front-end where such make-up gas is produced.

[0011] Summary of the invention

[0012] The invention aims to provide a novel solution to reduce the CO2 emissions of a steam reforming front-end for the production of a hydrogen-containing gas, such as ammonia make-up gas, based on primary reforming and conventional air-fired secondary reforming. The invention aims at a solution applicable to new plants as well as revamping of existing plants, without requiring the provision of expensive items such as air separation units.

[0013] The aim is reached with a process according to claim 1 . The invention combines a first reforming section, including a primary reformer and an air-fired secondary reformer, with a second reforming section running in parallel for the production of a hydrogen gas. The hydrogen gas produced in the second reforming section provides the fuel for the primary reformer of the first reforming section.

[0014] The feed mixture of the second reforming section includes a portion of the available hydrocarbon feed mixed with steam. The hydrocarbon feed, such as natural gas, is split into a first portion directed to the first reforming section, for the production of a hydrogen-containing process gas (synthesis gas), and a second portion directed to the second reforming section, for the internal production of hydrogen fuel.

[0015] The second reforming section includes a step of adiabatic pre-reforming of the feed mixture, followed by re-heating of the pre-reformed stream and subsequent reforming in a secondary reformer. Before pre-reforming, the feed mixture may be pre-heated.

[0016] The first reforming section and the second reforming section may share equipment such as equipment for desulphurization of the natural gas, feed of compressed air, or for purification of the hydrogen gas, for example for CO2 removal. Various embodiments may provide different degrees of integration between the two sections.

[0017] The invention is based on replacing the fossil fuel of the primary reformer with hydrogen gas produced on-site in the parallel reforming section. Substitution of fossil fuel with a hydrogen-based fuel allows to operate the steam reformer substantially carbon-free. The carbon dioxide generated in the process, including the parallel reforming section, can be captured and exported outside the process for a further use. Examples of a further use of the sequestrated carbon dioxide include the synthesis of urea and the synthesis of methanol or another process where the carbon dioxide is a source material. If not used in a process, the carbon dioxide can be sent to sequestration in suitable locations.

[0018] In the invention, a side unit (i.e. the second reforming section) converts a portion of the hydrocarbon feed (such as natural gas) into a hydrogen fuel, then this hydrogen fuel is used in the existing main unit to drastically reduce CO2 emissions. The invention can be applied to the reduction of CO2 emissions as such or in combination with increase of capacity. A very interesting application of the invention concerns the production of ammonia make-up gas and, consequently, the production of ammonia. Integration of production of ammonia and urea is also attractive because urea is produced from ammonia and carbon dioxide, thus the ammonia or a portion thereof may be used together with captured CO2 to produce urea.

[0019] A further aspect of the invention is a method for revamping an existing front end for the production of a hydrogen gas, particularly for the production of ammonia make-up gas, according to the claims.

[0020] Detailed description of the invention

[0021] The invention provides that a hydrocarbon feed, typically natural gas, is divided into a first portion and a second portion. The first portion of the hydrocarbon feed is converted into a reformed gas via a steam reforming process in a first reforming section including a primary reforming furnace and an air-blown secondary reformer. The so obtained reformed gas is further processed including at least water-gas shift and carbon dioxide removal to obtain a hydrogen-containing process gas, for example ammonia make-up gas comprising hydrogen and nitrogen suitable for the synthesis of ammonia.

[0022] The second portion of the feed is subject to a parallel steam reforming process which is performed in a second reforming section (“auxiliary section”). The so obtained hydrogen-containing gas, after a suitable processing, provides a fuel for the fired furnace of said first reforming section.

[0023] The hydrogen-rich gas produced in the second reforming section may be partially or entirely sent as a fuel to the primary reforming furnace. In the furnace, the hydrogen fuel replaces the conventional use of fossil fuel. If only a portion of said hydrogen fuel is sent to said furnace, the remainder gas may be sent to other fired equipment.

[0024] The second reforming section includes a pre-reformer of the feed mixture, a suitable reheater of the pre-reformed stream and a secondary reformer. Said secondary reformer may be fired with air, enriched air or pure oxygen according to different embodiments. In an embodiment, said secondary reformer of the second reforming section is blown with an air stream taken from the air feed of the main secondary reformer.

[0025] In an embodiment, the re-heating of said pre-reformed stream includes re-heating with heat recovered from the auxiliary secondary reformer. Accordingly, said reheater can be an indirect gas / gas heat exchanger having one side traversed by the pre-reformed stream (“cold” side) and the other side traversed by the hot effluent of said reformer (“hot” side).

[0026] The pre-heating of the feed mixture can also use heat recovered from the effluent of said auxiliary secondary reformer. In a preferred embodiment, the reformed gas effluent of said auxiliary secondary reformer is passed in sequence to a first gas / gas heat exchanger, to re-heat the pre-reformed stream, and then to a second gas / gas heat exchanger, to pre-heat the feed stream.

[0027] In some embodiments, the re-heating of the pre-reformed stream and / or the preheating of the feed mixture include(s) re-heating or pre-heating in a separate fired heater or using heat recovered from the main reforming section, for example by sending the corresponding stream (pre-reformed gas or feed mixture) to a coil mounted in the primary reformer of the main section. A fired heater for this purpose may be fired, preferably, with hydrogen fuel produced in the second reforming section.

[0028] Other options to pre-heat the feed mixture and / or to re-heat the pre-reformed stream include the use of an electrical heater or a start-up burner.

[0029] In accordance to the above, a re-heater of the pre-reformed gas may be any of: a separate heat exchanger, a separate fired furnace or separate heater, a coil inserted in the furnace of the main reforming section. A separate heater or furnace, when provided, may also be used for other services such as pre-heating of air.

[0030] In an interesting embodiment, the processing of the gas produced in the auxiliary reforming section includes that a hydrogen-rich gas obtained after CO2 removal is processed to separate nitrogen from hydrogen, thus increasing the purity of hydrogen. This step results in a stream of high-purity hydrogen, having a higher purity than the source stream subject to separation, and a nitrogen-rich stream which however still contains a significant amount of hydrogen and, accordingly, can still be used as a fuel. Preferably the so obtained high-purity hydrogen has a purity above 90% whereas the nitrogen-rich fuel may contain about 35-40% hydrogen. Said step of separation may be performed with membranes.

[0031] Both said fuel streams can be used in the first reforming section. This step can be appropriate when equipment in the reforming section require a hydrogen fuel of high purity, whereas other equipment can work well with the nitrogencontaining fuel.

[0032] The feed stream at the inlet of the pre-reformer has preferably a temperature of 350 to 550 °C, more preferably 400 to 500 °C, for example 440 °C or 450 °C. The re-heated gas, after pre-reforming and subsequent re-heating, has a temperature of preferably 600 to 680 °C, more preferably 620 to 650 °C, such as 630 °C or 640 °C.

[0033] In certain embodiments, the auxiliary secondary reformer receives enriched air. The term enriched air denotes air having an oxygen content which is higher than the natural content of oxygen in the air. For example, the molar fraction of oxygen in the enriched air may be 22% or greater. Oxygen-enriched air may be provided by an air separation unit or vacuum pressure swing adsorption unit (VPSA).

[0034] In case of revamping, the existing plant normally includes an air feed system which is originally designed to provide air for the main secondary reformer. Said air system can be revamped to provide an additional amount of air for the new secondary reformer of the second reforming section. Revamping the air system may include the provision of a booster compressor and / or the revamping of an existing air compressor. In some embodiment, a fully electric parallel compression is installed.

[0035] The second reforming section may include one or more water-gas shift reactors. The shift conversion of the second reforming section is preferably a medium temperature shift conversion carried out in the temperature range of 220 to 270 °C using a catalyst suitable to operate at a medium temperature, for example a copper-based catalyst. Particularly preferably, the second reforming section has a shift section based on a single MTS shift reactor. In alternative embodiments, the second reforming section may adopt a configuration with more than one adiabatic shift converters operating at different temperatures.

[0036] Cooling and / or heat recovery may be carried out between the shift conversion and the CO2 removal. Output of the carbon dioxide removal is a hydrogen-rich stream and carbon dioxide stream. Carbon dioxide stream can be exported and used for instance for the production of urea, or sent to a carbon capture, utilization and storage (CCUS) plant. The hydrogen-rich stream contains predominantly hydrogen. In preferred embodiments the hydrogen-rich stream contains at least 60% mol of hydrogen, preferably at least 65% mol or at least 70% mol. The balance may include predominantly nitrogen. In a preferred embodiment the concentration of hydrogen in said stream is 60% mol to 70% mol. The CO2 recovery may reach 90% to 95% or higher depending on the technique.

[0037] Carbon dioxide removal can be performed with known techniques such as pressure swing adsorption or with carbon dioxide washing unit operated with amine-based system, hot potassium carbonate-based system, methanol washing system, cryogenic separation system and other chemical or physical removal system. Preferably, under steady-state operation of the process the hydrogen-rich gas produced in the second reforming section provides at least 80%, preferably at least 90%, preferably 100% of the heat input of the fired furnace of the first reforming section.

[0038] In some embodiments, natural gas is added to the fired furnace of the primary reformer and used as fuel together with the hydrogen-rich stream. Natural gas can then be added to the hydrogen in a concentration of 1 % to 10 % and more preferably 1 % to 5%. When natural gas is used as fuel in the primary reformer together with hydrogen some carbon dioxide is generated from the combustion of methane however, the CO2 released into the environment is substantially lower than the CO2 generated when the steam converter is entirely operated with a natural gas fuel. Accordingly, the global CO2 emission of the plant and the OPEX are still limited over the prior art.

[0039] Another object of the invention is a method for revamping a front-end for production of hydrogen gas, according to the claims.

[0040] The front-end, to which the revamping procedure is applied, includes a reforming section comprising a primary reformer, which is a fired furnace operated with a hydrocarbon fuel, and an air-blown secondary reformer.

[0041] The revamping procedure includes the installation of a new reforming section, arranged to operate in parallel to the existing reforming section and arranged to produce a hydrogen-rich gas.

[0042] A portion of the available hydrocarbon fuel is directed to said new reforming section and the hydrogen-rich gas produced in the new reforming section is sent to the fired furnace of the existing primary reformer, to replace in part or in full the hydrocarbon fuel of said furnace.

[0043] The new reforming section, which is added in the revamping process, may be realized according to the various embodiments described above in connection with the second reforming section.

[0044] The revamping procedure may include the revamping or replacing of auxiliary equipment. In a typical case, the capacity in terms of hydrocarbon feed and air delivered to the plant will have to be increased. The related equipment may be revamped or additional equipment may be installed according to different embodiment.

[0045] The revamping procedure for example may include the installation or the upgrading of one or more of the following units: a compressor arranged to deliver a hydrocarbon feed to the reforming section; an air compressor arranged to deliver air to the secondary reformer; a hydrodesulfurization reactor arranged to desulphurize the hydrocarbon feed; an electric supply unit configured to supply electric power to said compressor and / or to said air compressor so that said compressor and / or said air compressor can be operated in fully electric mode.

[0046] The revamping of existing equipment may include replacing one or more parts thereof. For example, revamping an existing compressor, such as hydrocarbon feed compressor or an air compressor, may include the provision of new internals, e.g. a new rotor and / or a new diffuser. Revamping a reactor may also include the provision of new internals to enhance the reaction. In some embodiments the revamping may include the addition of items, such as adding a booster before or after an existing compressor.

[0047] A revamping according to the invention is of particular interest because a conventional natural gas-based front-end can be modernized to drastically reduce the CO2 emissions. This advantage is achieved by installing a side unit in parallel to the existing front-end, which means the modifications to the existing front-end are comparatively small and the revamping procedure is made easier.

[0048] Description of the figures

[0049] Figs. 1 -4 illustrate embodiments of the invention. Fig. 1 illustrates an embodiment with a first reforming section 100 (“main reforming section”) and a second reforming section (“auxiliary reforming section” or “side reforming section”) 200.

[0050] The main section 100 includes: natural gas compressor 101 ; heater 102; desulphurization stage 103; feed heating stage 104; primary reforming furnace 105; secondary reformer 106; cooling / shift stage 107; carbon dioxide removal stage 108; air compressor 109; air heater 110.

[0051] The auxiliary section 200 includes: feed pre-heater 201 ; pre-reformer 202; reheater 203; secondary reformer 204; first cooling stage 205 (“hot recovery train”); shift stage 206; second cooling stage 207 (“cold recovery train”).

[0052] A natural gas feed 10, after compression, preheating and desulphurization, is split into a first stream 11 feeding the main section 100 and a second stream 12 feeding the auxiliary section 200.

[0053] In the main section 100, the feed 11 is mixed with steam and converted via steam reforming into a hydrogen-containing product gas 13. The steam reforming performed in the main section 100 is conventional and includes a primary reforming in the fired furnace 105 followed by secondary reforming 106 wherein the partially reformed gas mixes with air supplied by the compressor 109; the mixture ignites and passes through a catalyst to complete the reforming reaction. The reformed gas is subject to shift and carbon dioxide removal to obtain the product gas 13.

[0054] The air stream delivered by the compressor 109 is mixed with steam; the so obtained mixture is heated in the air heater 110; a portion 15 of the mixture is sent to the main secondary reformer 106 and another portion 16 is sent to the auxiliary secondary reformer 204.

[0055] In an interesting embodiment, the product gas 13 is a make-up gas for the synthesis of ammonia, thus containing hydrogen and nitrogen in a molar ratio of about 3:1. The necessary amount of nitrogen may be introduced with the air stream entering the secondary reformer 106 or may be added separately, if needed.

[0056] In the auxiliary section 200, the feed 12 is added with steam; the so obtained mixture 120 of natural gas and steam is pre-heated in the heat exchanger 201 and subject to adiabatic pre-reforming in the stage 202. As a result of the endothermic reaction of pre-reforming, the gas is cooled. Typically, the temperature of the gas may drop by 30 to 100 °C. To reach a suitable temperature for the secondary reformer, the pre-reformed gas 20 is re-heated in the exchanger 203 before entering the auxiliary secondary reformer 204.

[0057] Said auxiliary secondary reformer 204 is fired by the air / steam mixture in line 16 and operates similarly to the secondary reformer 106 described previously. In the shown embodiment, the hot effluent 21 of said reformer auxiliary secondary 204 is the heat source of the heat exchangers 203 and 201 . The effluent 21 traversed the hot side of the re-heater 203, where heat is transferred to the pre-reformed gas 20, and then the hot side of the feed preheater 201 , where heat is transferred to the feed mixture of natural gas 12 and steam.

[0058] After passage through said exchangers 203 and 201 , the reformed gas 22 is further cooled in the cooling stage 205. Said stage 205 may include several heat exchangers in sequence (“hot train”) and may produce medium or high-pressure steam with heat removed from the gas 22. Medium-pressure steam may have a pressure of around 20 to 30 bar, for example 27 bar and 420 °C. High pressure steam may be saturated steam at a pressure of around 90-110 bar. Particularly, said stage 205 may produce the steam added to natural gas lines 11 and 12, to the air stream 14 and / or to the reformed gas sent to the shift stage 206. High- pressure steam may be superheated in existing primary reformer coils and added to plant HPS network.

[0059] After cooling, the reformed gas 23 is mixed with steam (which, as above may be produced in the cooling stage 205) and fed to the shift stage 206, which is preferably a medium-temperature shift stage. The effluent gas 24 of the shift stage 206 is further cooled in the cooling stage (“cold train”) 207. Due to the lower temperature, this stage 207 may pre-heat a water steam for subsequent evaporation in the stage 205 and / or may provide other services requiring low- grade heat such as reboiling of a MDEA solution used for CO2 removal in stage 108.

[0060] The cooled gas 25 is sent to the CO2 removal stage 108 of the main reforming section 100, obtaining a stream of CO2-depleted gas 26, which contains predominantly hydrogen and nitrogen. Said stream 26 is processed in a membrane-based hydrogen recovery unit (HRU) stage 208 to obtain a hydrogen stream 27 of high purity and a nitrogen-containing stream 28. For example the stream 27 contains 92% hydrogen; the stream 28 contains 37% hydrogen, the rest being mostly nitrogen.

[0061] Both streams 27, 28 are used to fuel the furnace 105, thus reducing or fully replacing the use of natural gas. The use of the nitrogen-containing fuel 28 may require specific burners or, in case of revamping, the replacing of existing burners. As the combustion of fuel streams 27, 28 produces virtually no CO2, the carbon emissions of said furnace are greatly reduced. The carbon dioxide stream withdrawn from the stage 108 may be captured or used in a process (such as synthesis of urea) to further reduce or eliminate emissions of CO2 in atmosphere. Hence the invention may result in the production of “blue” hydrogen wherein most or all of the CO2 generated in the process is captured and little or no emission of CO2 in atmosphere is generated.

[0062] It is highly preferred to use the CO2 removal stage 108 for processing the gas streams of both sections 100 and 200; in a variant however a separate CO2 removal stage for each section 100, 200 may be provided. Preferably the CO2 removal stage 108 includes one or more CO2 absorption towers where CO2 is absorbed using MDEA solution. In an exemplary embodiment, natural gas fuel is mixed with medium-pressure steam at a steam / carbon ratio of 3.1 and the mixture is preheated to 510 °C. After pre-reforming, the gas has a temperature of 450 °C and is re-heated to 650 °C. The secondary reformer 204 operates at around 925 °C. the reformed gas is fed to the shift section with steam / gas ratio of 0.42.

[0063] The fuel streams 27, 28 may provide the fuel input to the furnace 105 in part or entirely. A small amount of natural gas may be used as trim fuel or during transients, such as start-up, when the fuel streams 27, 28 are not available.

[0064] Fig. 2 illustrates a variant wherein the secondary reformer 204 is fired with a stream 30 of oxygen or enriched air produced by an air separation unit 209. The air stream 14 delivered by the compressor 109 is sent entirely to the reformer 106.

[0065] Fig. 3 illustrates another embodiment wherein the preheating of the feed 120 and the re-heating of the pre-reformed gas 20 are performed by a fired heater 210. Particularly, a coil 211 of said heater 210 is connected to the line of the mixture 120 and operates as feed heater, whereas another coil 213 is connected to the line of the effluent 20 and operates as re-heater.

[0066] In an interesting embodiment, said fired heater 210 uses a portion of the hydrogen fuel produced in the same section 200; for example, in Fig. 3 the hydrogen fuel 27 is split into a first portion 31 sent to the furnace 105 and a second portion 32 sent to said heater 210. Said fired heater may also use a portion of the natural gas.

[0067] The fired heater 210 may provide additional services such as natural gas preheating.

[0068] In another embodiment (not shown) the preheating of the feed mixture 120 and / or reheating of the pre-reformed gas 20 may be performed in a heat exchange coil mounted in the furnace 105. In another embodiment electrical heaters may be used.

[0069] The variant of Fig. 2 may be applied also to the embodiment of Fig. 3.

[0070] Fig. 4 illustrates the same diagram as in Fig. 1 but focussing on a revamping procedure of the section 100. Fig. 4 illustrates the provision of a natural gas compressor 150, new HDS section 151 , air compressor 152 and new CO2 absorber 153. The compressors 150 and 152 are preferably electric.

[0071] The new compressor 150 and new HDS section 151 may be required to process the additional amount of natural gas required by the auxiliary reforming section 200. The new air compressor 152 is necessary when the existing compressor 109 does not provide a sufficient spare capacity to feed also the new reformer

[0072] 204. For similar reasons, the CO2 separation section may be revamped by installing the new unit 153, to cope with the increased duty of processing the stream 25.

[0073] The above-described new units may be required particularly when it is desired to maintain the same capacity of the main section 100 in terms of output gas 13.

[0074] Clearly, also the scheme of Fig. 3 may be the result of a revamping. In such case, the revamping includes the provision of the fired heater 210. In alternative embodiments, the revamping may include modification of the furnace 105 to install one or more coil for heating the feed 120 and / or re-heating the gas 20.

Claims

CLAIMS1 ) A process for production of a hydrogen-containing synthesis gas comprising: a) providing a hydrocarbon feed (10), such as natural gas; b) a first portion (11 ) of said hydrocarbon feed is converted with a steam reforming process in a first reforming section (100) into a reformed gas and said reformed gas is further processed including at least steps of water-gas shift and carbon dioxide removal, to obtain said synthesis gas; c) the reforming of step b) includes a primary reforming in a fired furnace (105) and a subsequent secondary reforming (106); d) a second portion (12) of said hydrocarbon feed is subject to a parallel steam reforming process, which is performed in a second auxiliary reforming section (200) separately from the first reforming section (100), obtaining a reformed gas; e) the reformed gas obtained in step d) is further processed, including at least water-gas shift and carbon dioxide removal, to obtain a hydrogen-rich gas (26); f) the hydrogen-rich gas (26) obtained at step e) is partially or entirely sent as a fuel to the fired furnace (105) of said first reforming section (100); wherein the parallel reforming process of step d) includes: mixing said second portion of hydrocarbon feed (12) with steam, obtaining a feed stream (120) of the second reforming section; a pre-reforming step of said feed stream, which is performed adiabatically in a pre-reformer (202), obtaining a pre-reformed gas (20); a re-heating of said pre-reformed gas (20), obtaining a re-heated pre-reformed gas; a secondary reforming step of said re-heated gas, which is performed in a secondary reformer (204) of said second reforming section (200).2) A process according to claim 1 wherein said re-heating step of pre-reformed gas (20) includes re-heating in a first gas / gas indirect heat exchanger (203) by recovering heat from the reformer gas effluent (21 ) of said secondary reformer (204) of the second reforming section.3) A process according to claim 1 or 2 wherein said feed stream (120) of the second reforming section (200), before entering the pre-reformer, is heated in a second gas / gas indirect heat exchanger (201 ) by recovering heat from the reformed gas effluent of the secondary reformer of the second reforming section.4) A process according to claims 1 , 2 and 3 wherein the reformed gas effluent (21 ) of the secondary reformer (204) of the second reforming section is passed in sequence through said first gas / gas heat exchanger (203), to reheat the pre-reformed stream (20), and then through said second gas / gas heat exchanger (201 ), to pre-heat said feed stream (120).5) A process according to any of the previous claims wherein at least one step of re-heating the pre-reformed gas (20) and / or pre-heating the feed stream (120) is performed in a separate fired furnace (210) or in said fired furnace of step c).6) A process according to claim 5 wherein said separate fired furnace (210) uses a hydrogen-containing fuel stream (32) produced in the second reforming section.7) A process according to any of the previous claims wherein said step e) of processing the reformed gas includes that a hydrogen-rich gas obtained afterCO2 removal is processed to separate nitrogen from hydrogen, thus increasing the purity of hydrogen, obtaining a stream of hydrogen-rich fuel and a stream of nitrogen-rich fuel, and both said fuel streams are used in the first reforming section.8) A process according to claim 7 wherein said separation of nitrogen from hydrogen is performed in a membrane-based hydrogen recovery unit.9) A process according to any of the previous claims wherein said feed stream at the inlet of the pre-reformer has a temperature of 350 to 550 °C, preferably 400 to 500 °C.10) A process according to any of the previous claims wherein said re-heated stream has a temperature after re-heating of 600 to 680 °C, preferably 620 to 650 °C.11 )A process according to any of the previous claims wherein the hydrogencontaining synthesis gas produced in the first reforming section (100) is a make-up gas suitable for the synthesis of ammonia.12) A method for revamping a front-end for the production of hydrogen-containing gas, such as ammonia make-up gas, wherein: the existing front-end, to which the revamping procedure is applied, includes a reforming section comprising at least a primary reformer, which is a fired furnace, and an air-blown secondary reformer, said fired furnace being fired with a hydrocarbon fuel; the revamping procedure includes: installation of a new auxiliary reforming section, arranged to operate in parallel to said existing reforming section, the new reforming section being arranged to produce a hydrogen-rich gas;installation of a line arranged to send a portion of the available hydrocarbon feed to said new reforming section; installation of a line arranged to send the hydrogen-rich gas produced in the new reforming section to said fired furnace of the existing primary reformer, to replace in part or in full the hydrocarbon fuel of said furnace, wherein the new auxiliary reforming section includes: a pre-reformer (202) arranged to perform adiabatic pre-reforming of the hydrocarbon feed sent to said new reforming section, to obtain a pre-reformed gas; a re-heater (203, 213) of said pre-reformed gas (20); a secondary reformer (204) arranged to provide secondary reforming of the re-heated gas, said newly-installed secondary reformer being fired with any of air, oxygen or oxygen-enriched air.13) A method according to claim 12 wherein the said newly-installed secondary reformer is an air-blown reformer and the method includes that an air supply line, originally provided to feed air to the secondary reformer of the existing reforming section, is revamped to provide an air feed for the secondary reformer of the newly-installed reforming section.14) A method according to claim 12 or 13 wherein said re-heater of pre-reformed gas is a heat exchanger arranged to recover heat from a hot effluent of said newly-installed secondary reformer, or a separate furnace.15) A method according to any of claims 12 to 14, further including the provision of a membrane-based hydrogen recovery unit arranged to separate a hydrogen-containing stream, which is produced in the new reforming section, into a hydrogen-rich fuel and a nitrogen-rich fuel.16) A method according to any of claims 12 to 15, further including one or more of the following: revamping an existing hydrocarbon feed compressor, installing a booster in addition to an existing hydrocarbon feed compressor, revamping an existing air compressor arranged to feed air to a secondary reformer, revamping a hydrodesulfurization reactor arranged to desulphurize the hydrocarbon feed, providing a partially or fully electric compression of an air feed and / or of a hydrocarbon feed.

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