WO2024170712A1 - A process for production of hydrogen gas - Google Patents

A process for production of hydrogen gas Download PDF

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Publication number
WO2024170712A1
WO2024170712A1 PCT/EP2024/053921 EP2024053921W WO2024170712A1 WO 2024170712 A1 WO2024170712 A1 WO 2024170712A1 EP 2024053921 W EP2024053921 W EP 2024053921W WO 2024170712 A1 WO2024170712 A1 WO 2024170712A1
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gas
reforming
reformer
hydrogen
air
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PCT/EP2024/053921
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French (fr)
Inventor
Sergio Panza
Marco MAZZAMUTO CARLUCCI
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Casale Sa
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Publication of WO2024170712A1 publication Critical patent/WO2024170712A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/32—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air
    • C01B3/34—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents
    • C01B3/38—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents using catalysts
    • C01B3/382—Multi-step processes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/025—Preparation or purification of gas mixtures for ammonia synthesis
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/02—Processes for making hydrogen or synthesis gas
    • C01B2203/0205—Processes for making hydrogen or synthesis gas containing a reforming step
    • C01B2203/0227—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step
    • C01B2203/0233—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step the reforming step being a steam reforming step
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/02—Processes for making hydrogen or synthesis gas
    • C01B2203/0205—Processes for making hydrogen or synthesis gas containing a reforming step
    • C01B2203/0227—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step
    • C01B2203/0244—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step the reforming step being an autothermal reforming step, e.g. secondary reforming processes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/02—Processes for making hydrogen or synthesis gas
    • C01B2203/0283—Processes for making hydrogen or synthesis gas containing a CO-shift step, i.e. a water gas shift step
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/042—Purification by adsorption on solids
    • C01B2203/043—Regenerative adsorption process in two or more beds, one for adsorption, the other for regeneration
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0465—Composition of the impurity
    • C01B2203/0475—Composition of the impurity the impurity being carbon dioxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/06—Integration with other chemical processes
    • C01B2203/068—Ammonia synthesis
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/08—Methods of heating or cooling
    • C01B2203/0805—Methods of heating the process for making hydrogen or synthesis gas
    • C01B2203/0811—Methods of heating the process for making hydrogen or synthesis gas by combustion of fuel
    • C01B2203/0816—Heating by flames
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/08—Methods of heating or cooling
    • C01B2203/0805—Methods of heating the process for making hydrogen or synthesis gas
    • C01B2203/0838—Methods of heating the process for making hydrogen or synthesis gas by heat exchange with exothermic reactions, other than by combustion of fuel
    • C01B2203/0844—Methods of heating the process for making hydrogen or synthesis gas by heat exchange with exothermic reactions, other than by combustion of fuel the non-combustive exothermic reaction being another reforming reaction as defined in groups C01B2203/02 - C01B2203/0294
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/08—Methods of heating or cooling
    • C01B2203/0872—Methods of cooling
    • C01B2203/0888—Methods of cooling by evaporation of a fluid
    • C01B2203/0894—Generation of steam

Definitions

  • the present invention concerns the field of production of a hydrogen-containing synthesis gas by steam reforming.
  • 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 and subsequent 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.
  • 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.
  • EP 3 583 067 B1 teaches to use a portion of the hydrogen gas after CO2 removal as a fuel for the primary reformer.
  • ATR autothermal reforming
  • ASU air separation unit
  • WO 2015/067436 discloses a process for producing ammonia synthesis gas and a method for revamping a front-end of an ammonia plant.
  • EP 3 363770 discloses a process for the synthesis of ammonia with low emissions wherein a CO2- depleted synthesis gas provides a fuel fraction for one or more furnaces.
  • 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.
  • a hydrogen-containing gas such as ammonia make-up gas
  • 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.
  • 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.
  • said second reforming section may include a secondary reformer running in parallel with the first reforming section.
  • said reforming section may include a gas-heated reformer.
  • said gas-heated reformer may use, as a heat source, the process gas effluent from the secondary reformer of the first reforming section.
  • said gas-heated reformer uses as heating source the process gas effluent from a secondary reformer or a partial oxidation reactor of the second reforming section.
  • the second reforming section uses a portion of the available hydrocarbon feed.
  • the hydrocarbon feed such as natural gas
  • the hydrocarbon feed 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.
  • synthesis gas hydrogen-containing process gas
  • 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.
  • 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.
  • 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 sequestrated 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.
  • 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.
  • 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.
  • 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.
  • the second portion of the feed is subject to a parallel process of steam reforming process which is performed in a second reforming section.
  • Said parallel reforming produces a reformed gas which, after a suitable processing, provides a fuel input for the fired furnace of said first reforming section.
  • the hydrogen-rich gas obtained from the parallel reforming may be partially or entirely sent as a fuel to the primary reforming furnace.
  • the hydrogen-rich gas is combusted to provide heat for the reforming process, replacing the conventional use of fossil fuel. If only a portion of said hydrogen- rich is sent to said furnace, the remainder gas may be sent to other fired equipment.
  • the second reforming section may include a gas heated reformer (GHR), a secondary reformer, a partial oxidation reactor or a combination thereof, such as a GHR followed by a secondary reformer or GHR followed by a partial oxidation reactor.
  • GHR gas heated reformer
  • the second reforming section may include a stand-alone reformer or a combination of multiple reformers such as two reformers.
  • At least a part of the reforming heat required by the second reforming section is recovered from the reformed gas produced in the first reforming section.
  • the hot reformed gas produced in the first reforming section, before the water-gas shift step is sent to the second reforming section where it is used as a heat source.
  • said hot effluent is sent to one side of a gas-heated reformer and the other side of said gas-heated reformer is traversed by the gas under reforming.
  • the second reforming section may include a gas-heated reformer having a first side and a second side.
  • the first side is traversed by the second portion of hydrocarbon feed mixed with steam which undergoes reforming, and the second side is traversed by the hot reformed gas taken from the first reforming section.
  • the gas-heated reformer is a shell-and-tube equipment, the first side is a tube side and the second side is a shell side.
  • the gas-heated reformer is followed by a secondary reformer which receives air or enriched air to produce a hydrogen rich stream.
  • the hot gas at the outlet of this second secondary reformer is preferably routed to a WHB and is not used as heating source for reforming.
  • the second reforming section includes a gas-heated reformer followed by a secondary reformer or by a partial oxidation (POX) reactor.
  • the secondary reformer or the POX reactor may receive an air feed or an enriched air feed.
  • enriched air denotes air having an oxygen content which is higher than the natural oxygen content in the air.
  • the molar fraction of oxygen in the enriched air may be 22% or more.
  • the existing plant may include an air feed system which is originally designed to provide air for the secondary reformer of the first reforming section. Said air system can be revamped to provide an additional amount of air for the newly installed reformer or POX reactor 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 compression is installed.
  • the second portion of the hydrocarbon feed is mixed with steam and the mixture is introduced in a first side of a gas-heated reformer to generate a partially reformed gas.
  • the partially reformed gas is then processed in a subsequent reformer wherein a second reforming step is carried out in presence of air and steam.
  • Said subsequent reformer can be seen as arranged in series over the gas-heated reformer.
  • Output of the subsequent reformer is a reformed gas.
  • the so obtained reformed gas can be sent to a second side of the gas-heated reformer to provide heat for the first reforming step.
  • the reformed gas leaves the second side of the gas-heated reactor as a cooled stream.
  • the cooled stream is further processed to obtain a hydrogen-rich gas.
  • the hydrogen-rich gas is used as a fuel for the primary reformer.
  • said second reforming section includes a stand-alone secondary reformer and said reformer is fired with oxygen-enriched air or with ambient air.
  • Oxygen-enriched air may be provided by an air separation unit or vacuum pressure swing adsorption unit (VPSA).
  • the second reforming section may include one or more water-gas shift reactors.
  • the shift conversion 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.
  • the second reforming section has a shift section based on a single MTS shift reactor.
  • the second reforming section may adopt a configuration with more than one adiabatic shift converters.
  • the carbon dioxide purification is preferably carried out to sequestrate CO2 removed from the shifted gas. Cooling and/or heat recovery may be carried out between the shift conversion and the CO2 purification.
  • Output of the carbon dioxide purification is a hydrogen-rich stream and carbon dioxide stream. Carbon dioxide stream can be exported and used for instance for the production of urea.
  • the hydrogen-rich stream contains predominantly hydrogen.
  • 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 nitrogen introduced with combustion air.
  • 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 used.
  • 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.
  • natural gas is added to the fired furnace of the primary reformed and used as fuel together with the hydrogen-rich stream. Natural gas can then be added to the hydrogen in a molar concentration of 1 % to 5%.
  • 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.
  • the secondary reformer of the first reforming section is an air-fired (or air blown) equipment so that no air separation unit (ASU) is required.
  • ASU air separation unit
  • a carbon dioxide removal is performed on the gas produced in both the first reforming section and second reforming section. This can be done in separate CO2 removal unit or in the same unit according to various embodiments. For example, in case of revamping, an existing CO2 removal unit can be revamped to accommodate the gas produced in the new reforming section.
  • 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, and other chemical or physical removal system.
  • Another object of the invention is a method for revamping a front-end for production of hydrogen gas, according to the claims.
  • 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.
  • a reforming section comprising a primary reformer, which is a fired furnace operated with a hydrocarbon fuel, and an air-blown secondary reformer.
  • 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.
  • 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.
  • 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.
  • the revamping procedure may include the revamping or replacing of auxiliary equipment.
  • the related equipment may be revamped or additional equipment may be installed according to different embodiment.
  • 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 prior to the reformer section; 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.
  • a further aspect of the present invention concerns an ammonia plant wherein the reforming section (front end) for the production of ammonia make-up gas is operated by a single secondary reformer.
  • Said secondary reformer may be operated with air or enriched air, in order to balance the hydrogen to nitrogen ratio in the gas.
  • the gas is fed to a shift conversion section and finally to a CO2 removal section.
  • part of the gas is recycled as CO2-free fuel gas in the fuel gas system, while the balance gas is sent to an ammonia synthesis section (back end) to generate ammonia.
  • an exchanger reformer can be installed downstream of the secondary reformer.
  • Figs. 1 -5 disclose exemplary embodiments of a process or plant according to the invention. Items commons to the figures are denoted by the same numerals. The diagram in each of Figs. 1 to 5 may be regarded as a new plant or the result of a revamping procedure.
  • FIG. 6 illustrates an embodiment of an ammonia process according to a further aspect of the present invention.
  • First embodiment (Fig. 1 )
  • Fig. 1 illustrate the following main items:
  • Natural gas compressor 1 desulphurization unit 2; first mixed feed heat exchanger 3; primary reformer 4; secondary reformer 5; cooling and shift section 6;
  • CO2 removal section 7 second mixed feed heater 9; gas heated reformer (GHR) 10; additional shift section 13; additional CO2 removal section 72; gas coolers 11 , 12, 25.
  • GHR gas heated reformer
  • the reformers 4 and 5, the shift section 6 and CO2 removal section 7 are part of a first reforming section 80.
  • the GHR 10, the shift section 13 and the CO2 removal section 72 are part of a second reforming section 8.
  • a natural gas feed 15 after compression and desulphurization is split into a first portion 16 and a second portion 17.
  • the first portion 16 feeds the first reforming section 80 where a hydrogen-containing process gas 19 is produced.
  • the second portion 17 feeds the second reforming section 8 running in parallel to the first reforming section 80 producing a hydrogen-rich stream 22.
  • the stream 19 may be denoted as process gas whereas the stream 22 may be regarded as a fuel stream because, as explained below, said stream 22 represents a fuel stream for the primary reformer 4.
  • the first feed portion 16, after addition of steam 18, is preheated in the mixed feed heater 3.
  • the preheated feed of natural gas and steam is reformed in the primary reformer 4 and the effluent 43 of the primary reformer 4 is further converted in the secondary reformer 5 to generate a hot effluent 23.
  • the primary reformer 4 includes tubes filled with a catalyst.
  • the hot effluent 43 is contacted with air 40 to start combustion of the hydrocarbons still contained in the process gas, and the reforming reaction is performed over a suitable catalyst.
  • the second feed portion 17 is added with steam 20; the so obtained mixture 57 is preheated in the mixed feed heater 9 and reformed in the gas-heated reformer 10 to generate an effluent 21 of reformed gas.
  • the heat for reforming the mixture 57 is provided by the hot effluent 23 of the secondary reformer 5.
  • the gas-heated reformer 10 has a first side (reforming side) and a second side (hot side), which are in a heat exchange relationship but not in a direct communication.
  • the hot side is in communication with the outlet of the reformer 5 so that it is traversed by the hot effluent 23; the reforming side is traversed by the mixture 57, so that the effluent 23 transfers heat to the mixture 57 undergoing the reforming process.
  • the gas-heated reformer 10 is a shell-and-tube apparatus, the hot side being the shell side (i.e. the space around the tubes) and the reforming side being the tube side (i.e. the inside of tubes, containing the reforming catalyst). Accordingly, the catalytic tubes are heated externally by the hot gas 23 traversing the shell side.
  • the effluent 23 is sent to the cooling and shift section 6 and subsequently to the CO2 removal section 7 for production of the hydrogen-containing process gas 19.
  • a CO2-rich stream 63 is removed from the gas in the CO2 removal section 7 and preferably captured for a further use.
  • Said hydrogen-containing process gas 19 in an interesting application is ammonia make-up gas, which means it contains a suitable amount of nitrogen introduced with the air 40, or added separately.
  • the effluent 21 of the reforming side of the gas heated reformer 10 is cooled in the heat exchangers (gas coolers) 11 , 12 and sent to the shift section 13 and carbon dioxide removal section 72 to obtain the hydrogen-rich fuel 22 sent to the primary reformer 4.
  • Said hydrogen-rich fuel 22 fires the burners of the primary reformer 4, providing the heat for reforming the mixed feed of natural gas 16 and steam 18.
  • the carbon dioxide removal section 72 may be separated from the carbon dioxide removal section 7 or the two sections 7, 72 may be part of a single section.
  • the reforming section 8 is arranged in parallel to the reforming section 80.
  • the reforming section 8 includes the heat exchanges 9, 11 , 12 and 25, the gas heated reformer 10 and the shift section 13.
  • the second portion 17 of the feed, which is processed in the reforming section 8, is entirely used for the production of the hydrogen fuel 22, whereas the hydrogen-containing process gas 19 is entirely produced by the reforming section 80.
  • the second reforming section 8 has its own shift section 13 to process the reformed gas from the gas heated reformer 10.
  • the shift section 13 may include a plurality of shift reactors, such as a high-temperature shift (HTS) reactor followed by a low-temperature shift (LTS) reactor, or a single shift reactor.
  • a single reactor may be, in certain embodiment, a medium-temperature shift (MTS) reactor with a suitable catalyst such as a copper-based catalyst and a shift temperature around 200 - 300 °C.
  • the MTS can be adiabatic or isothermal reactor.
  • the hydrogen fuel 22 satisfies the entire fuel input of the primary reformer 4 during steady-state operation. It follows that the primary reformer 4 does not need a hydrocarbon fuel during normal operation of the plant. A hydrocarbon fuel, such as a portion of the feed 15, may be provided temporarily to the primary reformer 4 during transients such as start-up or shut down when necessary.
  • the scheme of Fig. 1 may be applied to new plants or may be the result of a revamping procedure.
  • the revamping procedure may be performed on an existing plant including the first reforming section 80.
  • the revamping procedure may involve the addition of the reforming section 8 and re-direction of the effluent 23 to the gas-heated reformer 10.
  • the revamping does not require the installation of an air separation unit because the secondary reformer 5 continues to operate with air.
  • the revamping procedure may include that the natural gas compressor 1 and the HDS section 2 are revamped to process the increased feed.
  • the purification of the shifted gas 24 is performed in the CO2 removal section 72.
  • said CO2 removal section 72 is integrated with the CO2 removal section 7 of the process gas 19, for example the sections 7 and 72 are part of the same section.
  • the existing CO2 removal section 7, originally designed for the process gas produced in the first reforming section 80 is revamped to accommodate an additional CO2 removal capacity for the hydrogen gas produced in the newly-installed reforming section 8.
  • Fig. 2 discloses a variant of Fig. 1 wherein the second reforming section 8 includes a gas-heated rector 10 and an additional secondary reforming reactor 50.
  • said additional reactor 50 is a partial oxidation (POX) reactor.
  • a mixture of air 40 and steam 42 is sent partly to the secondary reformer 5 and partly to said additional reforming reactor 50, via line 61 .
  • the effluent of the secondary reforming reactor 50 provides the heat source for the gas-heated reactor 10, so that it is not required to redirect the effluent 23 of the secondary reformer 5, and said effluent 23 can be sent directly to the cooling and shift section 6.
  • the existing secondary reformer 5 in this embodiment is a steam reformer which is fed with air/steam mixture.
  • the air feed 40 after compression in the air compressor 41 is mixed with steam 42 and the air/steam mixture is sent partly to the existing secondary reformer 5 and partly to the additional secondary reforming reactor 50.
  • the natural gas feed 15 is split into a first portion 16 and a second portion 17.
  • the first portion 16 is processed in the reforming section 80 to produce the synthesis gas 19, which represents a process gas
  • the second portion 17 is processed in the parallel reforming section 8 to produce the hydrogen-rich fuel gas 22.
  • the mixture 57 is reformed in the reforming side of the gas-heated reactor 10.
  • the so obtained effluent 60 is reformed further in the reactor 50, in presence of the air/steam mixture from line 61 and pre-heated in the heat exchanger 28.
  • the gas/steam mixture 57 is partially reformed in the reactor 10 and conversion is completed in the subsequent reactor 50.
  • the hot reformed effluent 53 of the reactor 50 traverses the hot side of the gas heated reactor 10 to supply heat to the process of reforming of the mixture 57.
  • the gas-heated reactor 10 is preferably a shell-and-tube equipment wherein the hot side traversed by the effluent 53 is a shell side and the reforming side is a tube side.
  • the process gas 54 effluent from the hot side of the reactor 10 is cooled in the heat exchangers 11 and 12 and is treated in the shift section 13 and in the CO2 removal section 72 to produce the hydrogen-rich fuel 22.
  • the gas coolers 25, 26 and 27 are arranged to reduce the temperature of the shifted gas 24 and recover heat prior to the CO2 removal section 72.
  • the heat removed from the shifted gas may be used to produce steam for the steam reforming and/or for adjusting the steam to carbon ratio in the shift section 13.
  • Fig. 2 illustrates that the heat exchangers 27, 12 and 11 are connected to a steam network fed with pressurized water 100 as a cooling medium, to obtain steam 300 which is mixed partly with the feed 17 and partly with the reformed gas entering the shift section 13.
  • a revamping procedure to implement the scheme of Fig. 2 involves the addition of the new reforming section 8 including the gas-heated reactor 10 and the new secondary reforming reactor 50.
  • a natural gas booster 30 and/or an air booster 31 may be installed, if the existing compressors do not provide adequate spare capacity.
  • the revamping procedure may also include any of: addition of a desulphurization unit or upgrade of the existing section 2; upgrade of the existing carbon dioxide removal section 7; addition of the new carbon dioxide removal section 72.
  • the compression of natural gas and/or the compression of air is performed, at least partially, in electric mode. This can be done by adding an electric booster to the existing natural gas compressor 1 and/or to the existing air compressor 41 , or by replacing one or both said compressors 1 , 41 with a fully electric compressor.
  • Fig. 3 discloses an embodiment wherein the second reforming section 8 includes a gas-heated reformer 65 and a secondary reformer 58, and the gas-heated reformer 65 is heated by the effluent of the reformer 5.
  • the effluent 23 of the secondary reformer 5 is sent to the hot side (e.g. shell side) of the gas-heated reformer 65 to supply reforming heat for the mixed feed 57.
  • Said mixed feed 57 includes the second portion 17 of natural gas and steam 20.
  • the effluent 66 of the hot side of the reformer 65 is sent to the cooling and shift section 6 and to the CO2 removal section 7 to generate the makeup gas 19.
  • the secondary reformer 5 is a steam reformer which is fed with air 40 and steam 42.
  • the second portion of hydrocarbon 17 after addition of steam 20 is preheated in the exchanger 9 and reformed in the reforming side (e.g. tube side) of the gas heated reactor 65.
  • the effluent 67 of the reforming side of the gas heated reactor 65 is further reformed in the secondary reformer 58 with air and steam introduced via line 44 to generate a reformed gas 68.
  • the reformed gas 68 after suitable cooling in the heat exchangers 11 and 12 and shift conversion 13 is purified in the CO2 removal section 72 to obtain the hydrogen-rich fuel 22.
  • Fig. 4 illustrates an embodiment wherein the second reforming section 8 is based on a stand-alone secondary reformer 158 fired with oxygen-enriched air.
  • the mixture of natural gas 17 and steam 20 is reformed in the secondary reformer 58 in presence of a mixture of oxygen-enriched air 67 and steam 142.
  • the oxygen-enriched air 67 is produced by a vacuum pressure swing adsorption (VPSA) unit 71.
  • the additional air feed for the VPSA unit 71 is provided by a booster 70.
  • the VPSA unit 71 may be replaced by an air separation unit if cost is acceptable.
  • Fig. 5 illustrates an embodiment similar to Fig. 4, wherein the stand-alone secondary reformer 158 is fed with air and no air enrichment is provided. The additional air feed is provided by a booster 31. The feed gas 170 fed to the secondary reformer 158 is taken downstream the primary reformer 4.
  • Fig. 6 discloses a front-end for production of ammonia make-up gas 19.
  • a hydrocarbon source such as natural gas 15 is compressed, cleaned in desulphurization unit 2 and added with steam 18.
  • the so obtained mixture 16 is heated in a gas heater 8 and sent to a primary reformer 4.
  • the partially reformed effluent 43 of the primary reformer 4 is sent to a secondary reformer 5 to completion of the reforming process.
  • the secondary reformer 5 is blown with an oxygen-containing stream 40.
  • Said stream 40 may be air or oxygen-enriched air.
  • the oxygen-enriched air may be provided by a VPSA unit or air separation unit (ASU).
  • the effluent of the secondary reformer 5 is sent to a cooling and shift section 6 and to a CO2 removal section 7 where carbon dioxide 63 is removed from the process gas.
  • a portion of the hydrogen-rich gas obtained after CO2 removal is sent as fuel stream 22 to the primary reformer 4.
  • the balance provides the makeup gas 19.
  • Temperature of the hot effluent 23 955 °C.
  • Temperature of the reformed gas 66 790 °C.

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Abstract

A process for the production of a hydrogen-containing gas, such as ammonia make-up gas (19), from a hydrocarbon feed (15), the process comprising reforming of a first portion of a hydrocarbon feed, which is performed in a first reforming section (80) including a fired furnace (4) for primary reforming, and a parallel steam reforming process (10) of a second portion (17) of said hydrocarbon feed, which is performed in a second reforming section (8), to generate a hydrogen-rich fuel (22) for said fired furnace.

Description

A process for production of hydrogen gas
DESCRIPTION
Field of application
The present invention concerns the field of production of a hydrogen-containing synthesis gas by steam reforming.
Prior art
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 and subsequent 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.
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.
In recent years, the demand to reduce CO2 emissions has become increasingly stringent. Several legislations worldwide impose a fee on every ton of CO2 emitted into the atmosphere and this is likely to progressively increase in the upcoming years. 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.
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.
WO 2015/067436 discloses a process for producing ammonia synthesis gas and a method for revamping a front-end of an ammonia plant. EP 3 363770 discloses a process for the synthesis of ammonia with low emissions wherein a CO2- depleted synthesis gas provides a fuel fraction for one or more furnaces.
Summary of the invention
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.
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.
In certain embodiments, said second reforming section may include a secondary reformer running in parallel with the first reforming section. In certain embodiments, said reforming section may include a gas-heated reformer. According to some embodiments, said gas-heated reformer may use, as a heat source, the process gas effluent from the secondary reformer of the first reforming section. In another embodiment said gas-heated reformer uses as heating source the process gas effluent from a secondary reformer or a partial oxidation reactor of the second reforming section.
The second reforming section uses a portion of the available hydrocarbon feed. Typically, 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.
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.
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 sequestrated 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.
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.
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.
Detailed description of the invention
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.
The second portion of the feed is subject to a parallel process of steam reforming process which is performed in a second reforming section. Said parallel reforming produces a reformed gas which, after a suitable processing, provides a fuel input for the fired furnace of said first reforming section.
The hydrogen-rich gas obtained from the parallel reforming may be partially or entirely sent as a fuel to the primary reforming furnace. In the furnace, the hydrogen-rich gas is combusted to provide heat for the reforming process, replacing the conventional use of fossil fuel. If only a portion of said hydrogen- rich is sent to said furnace, the remainder gas may be sent to other fired equipment.
The second reforming section may include a gas heated reformer (GHR), a secondary reformer, a partial oxidation reactor or a combination thereof, such as a GHR followed by a secondary reformer or GHR followed by a partial oxidation reactor. The second reforming section may include a stand-alone reformer or a combination of multiple reformers such as two reformers.
In a preferred embodiment, at least a part of the reforming heat required by the second reforming section is recovered from the reformed gas produced in the first reforming section. For example, in an embodiment, the hot reformed gas produced in the first reforming section, before the water-gas shift step, is sent to the second reforming section where it is used as a heat source. In an embodiment, said hot effluent is sent to one side of a gas-heated reformer and the other side of said gas-heated reformer is traversed by the gas under reforming.
More specifically, the second reforming section may include a gas-heated reformer having a first side and a second side. The first side is traversed by the second portion of hydrocarbon feed mixed with steam which undergoes reforming, and the second side is traversed by the hot reformed gas taken from the first reforming section. Typically, the gas-heated reformer is a shell-and-tube equipment, the first side is a tube side and the second side is a shell side. In a preferred embodiment, the gas-heated reformer is followed by a secondary reformer which receives air or enriched air to produce a hydrogen rich stream. The hot gas at the outlet of this second secondary reformer is preferably routed to a WHB and is not used as heating source for reforming.
In certain embodiments, the second reforming section includes a gas-heated reformer followed by a secondary reformer or by a partial oxidation (POX) reactor. The secondary reformer or the POX reactor may receive an air feed or an enriched air feed. The term enriched air denotes air having an oxygen content which is higher than the natural oxygen content in the air. For example, the molar fraction of oxygen in the enriched air may be 22% or more. In case of revamping, the existing plant may include an air feed system which is originally designed to provide air for the secondary reformer of the first reforming section. Said air system can be revamped to provide an additional amount of air for the newly installed reformer or POX reactor 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 compression is installed.
In a preferred embodiment, the second portion of the hydrocarbon feed is mixed with steam and the mixture is introduced in a first side of a gas-heated reformer to generate a partially reformed gas. The partially reformed gas is then processed in a subsequent reformer wherein a second reforming step is carried out in presence of air and steam. Said subsequent reformer can be seen as arranged in series over the gas-heated reformer. Output of the subsequent reformer is a reformed gas. The so obtained reformed gas can be sent to a second side of the gas-heated reformer to provide heat for the first reforming step. The reformed gas leaves the second side of the gas-heated reactor as a cooled stream. The cooled stream is further processed to obtain a hydrogen-rich gas. The hydrogen-rich gas is used as a fuel for the primary reformer.
In another embodiment, said second reforming section includes a stand-alone secondary reformer and said reformer is fired with oxygen-enriched air or with ambient air. Oxygen-enriched air may be provided by an air separation unit or vacuum pressure swing adsorption unit (VPSA).
The second reforming section may include one or more water-gas shift reactors. The shift conversion 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. The carbon dioxide purification is preferably carried out to sequestrate CO2 removed from the shifted gas. Cooling and/or heat recovery may be carried out between the shift conversion and the CO2 purification. Output of the carbon dioxide purification is a hydrogen-rich stream and carbon dioxide stream. Carbon dioxide stream can be exported and used for instance for the production of urea. 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 nitrogen introduced with combustion air. 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 used.
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.
In some embodiments, natural gas is added to the fired furnace of the primary reformed and used as fuel together with the hydrogen-rich stream. Natural gas can then be added to the hydrogen in a molar concentration of 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.
The secondary reformer of the first reforming section is an air-fired (or air blown) equipment so that no air separation unit (ASU) is required.
A carbon dioxide removal is performed on the gas produced in both the first reforming section and second reforming section. This can be done in separate CO2 removal unit or in the same unit according to various embodiments. For example, in case of revamping, an existing CO2 removal unit can be revamped to accommodate the gas produced in the new reforming section. 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, and other chemical or physical removal system.
Another object of the invention is a method for revamping a front-end for production of hydrogen gas, according to the claims.
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.
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.
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.
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.
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. 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 prior to the reformer section; 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.
A further aspect of the present invention, particularly for new grass-root ammonia plants, concerns an ammonia plant wherein the reforming section (front end) for the production of ammonia make-up gas is operated by a single secondary reformer. Said secondary reformer may be operated with air or enriched air, in order to balance the hydrogen to nitrogen ratio in the gas. After the secondary reformer the gas is fed to a shift conversion section and finally to a CO2 removal section. At the outlet of said CO2 removal section, part of the gas is recycled as CO2-free fuel gas in the fuel gas system, while the balance gas is sent to an ammonia synthesis section (back end) to generate ammonia. In an embodiment, an exchanger reformer can be installed downstream of the secondary reformer.
Description of the figures
Figs. 1 -5 disclose exemplary embodiments of a process or plant according to the invention. Items commons to the figures are denoted by the same numerals. The diagram in each of Figs. 1 to 5 may be regarded as a new plant or the result of a revamping procedure.
Fig. 6 illustrates an embodiment of an ammonia process according to a further aspect of the present invention. First embodiment (Fig. 1 )
Fig. 1 illustrate the following main items:
Natural gas compressor 1 ; desulphurization unit 2; first mixed feed heat exchanger 3; primary reformer 4; secondary reformer 5; cooling and shift section 6;
CO2 removal section 7; second mixed feed heater 9; gas heated reformer (GHR) 10; additional shift section 13; additional CO2 removal section 72; gas coolers 11 , 12, 25.
The reformers 4 and 5, the shift section 6 and CO2 removal section 7 are part of a first reforming section 80. The GHR 10, the shift section 13 and the CO2 removal section 72 are part of a second reforming section 8.
A natural gas feed 15 after compression and desulphurization is split into a first portion 16 and a second portion 17. The first portion 16 feeds the first reforming section 80 where a hydrogen-containing process gas 19 is produced. The second portion 17 feeds the second reforming section 8 running in parallel to the first reforming section 80 producing a hydrogen-rich stream 22. The stream 19 may be denoted as process gas whereas the stream 22 may be regarded as a fuel stream because, as explained below, said stream 22 represents a fuel stream for the primary reformer 4. The first feed portion 16, after addition of steam 18, is preheated in the mixed feed heater 3. The preheated feed of natural gas and steam is reformed in the primary reformer 4 and the effluent 43 of the primary reformer 4 is further converted in the secondary reformer 5 to generate a hot effluent 23. Typically, the primary reformer 4 includes tubes filled with a catalyst. In the secondary reformer 5, the hot effluent 43 is contacted with air 40 to start combustion of the hydrocarbons still contained in the process gas, and the reforming reaction is performed over a suitable catalyst.
The second feed portion 17 is added with steam 20; the so obtained mixture 57 is preheated in the mixed feed heater 9 and reformed in the gas-heated reformer 10 to generate an effluent 21 of reformed gas.
The heat for reforming the mixture 57 is provided by the hot effluent 23 of the secondary reformer 5. The gas-heated reformer 10 has a first side (reforming side) and a second side (hot side), which are in a heat exchange relationship but not in a direct communication. The hot side is in communication with the outlet of the reformer 5 so that it is traversed by the hot effluent 23; the reforming side is traversed by the mixture 57, so that the effluent 23 transfers heat to the mixture 57 undergoing the reforming process. Preferably the gas-heated reformer 10 is a shell-and-tube apparatus, the hot side being the shell side (i.e. the space around the tubes) and the reforming side being the tube side (i.e. the inside of tubes, containing the reforming catalyst). Accordingly, the catalytic tubes are heated externally by the hot gas 23 traversing the shell side.
After a passage through the hot side of the gas-heated reformer 10, the effluent 23 is sent to the cooling and shift section 6 and subsequently to the CO2 removal section 7 for production of the hydrogen-containing process gas 19. A CO2-rich stream 63 is removed from the gas in the CO2 removal section 7 and preferably captured for a further use.
Said hydrogen-containing process gas 19, in an interesting application, is ammonia make-up gas, which means it contains a suitable amount of nitrogen introduced with the air 40, or added separately.
The effluent 21 of the reforming side of the gas heated reformer 10 is cooled in the heat exchangers (gas coolers) 11 , 12 and sent to the shift section 13 and carbon dioxide removal section 72 to obtain the hydrogen-rich fuel 22 sent to the primary reformer 4. Said hydrogen-rich fuel 22 fires the burners of the primary reformer 4, providing the heat for reforming the mixed feed of natural gas 16 and steam 18.
The carbon dioxide removal section 72 may be separated from the carbon dioxide removal section 7 or the two sections 7, 72 may be part of a single section.
The reforming section 8 is arranged in parallel to the reforming section 80. The reforming section 8 includes the heat exchanges 9, 11 , 12 and 25, the gas heated reformer 10 and the shift section 13. The second portion 17 of the feed, which is processed in the reforming section 8, is entirely used for the production of the hydrogen fuel 22, whereas the hydrogen-containing process gas 19 is entirely produced by the reforming section 80.
The second reforming section 8 has its own shift section 13 to process the reformed gas from the gas heated reformer 10. The shift section 13 may include a plurality of shift reactors, such as a high-temperature shift (HTS) reactor followed by a low-temperature shift (LTS) reactor, or a single shift reactor. A single reactor may be, in certain embodiment, a medium-temperature shift (MTS) reactor with a suitable catalyst such as a copper-based catalyst and a shift temperature around 200 - 300 °C. The MTS can be adiabatic or isothermal reactor.
Preferably, the hydrogen fuel 22 satisfies the entire fuel input of the primary reformer 4 during steady-state operation. It follows that the primary reformer 4 does not need a hydrocarbon fuel during normal operation of the plant. A hydrocarbon fuel, such as a portion of the feed 15, may be provided temporarily to the primary reformer 4 during transients such as start-up or shut down when necessary.
The scheme of Fig. 1 may be applied to new plants or may be the result of a revamping procedure. The revamping procedure may be performed on an existing plant including the first reforming section 80. The revamping procedure may involve the addition of the reforming section 8 and re-direction of the effluent 23 to the gas-heated reformer 10.
Notably, the revamping does not require the installation of an air separation unit because the secondary reformer 5 continues to operate with air.
If it is desired to maintain the same capacity in terms of output gas 19, the amount of natural gas 15 must be increased because a portion of the gas feed is diverted to the new reforming section 8. When necessary, the revamping procedure may include that the natural gas compressor 1 and the HDS section 2 are revamped to process the increased feed.
The purification of the shifted gas 24 is performed in the CO2 removal section 72. In some embodiments, said CO2 removal section 72 is integrated with the CO2 removal section 7 of the process gas 19, for example the sections 7 and 72 are part of the same section. For example, in an embodiment of the revamping procedure, the existing CO2 removal section 7, originally designed for the process gas produced in the first reforming section 80, is revamped to accommodate an additional CO2 removal capacity for the hydrogen gas produced in the newly-installed reforming section 8.
Second embodiment (Fig. 2)
Fig. 2 discloses a variant of Fig. 1 wherein the second reforming section 8 includes a gas-heated rector 10 and an additional secondary reforming reactor 50. For example, said additional reactor 50 is a partial oxidation (POX) reactor. A mixture of air 40 and steam 42 is sent partly to the secondary reformer 5 and partly to said additional reforming reactor 50, via line 61 . In this embodiment, the effluent of the secondary reforming reactor 50 provides the heat source for the gas-heated reactor 10, so that it is not required to redirect the effluent 23 of the secondary reformer 5, and said effluent 23 can be sent directly to the cooling and shift section 6.
The existing secondary reformer 5 in this embodiment is a steam reformer which is fed with air/steam mixture. The air feed 40 after compression in the air compressor 41 is mixed with steam 42 and the air/steam mixture is sent partly to the existing secondary reformer 5 and partly to the additional secondary reforming reactor 50.
Similar to Fig. 1 , the natural gas feed 15 is split into a first portion 16 and a second portion 17. The first portion 16 is processed in the reforming section 80 to produce the synthesis gas 19, which represents a process gas, and the second portion 17 is processed in the parallel reforming section 8 to produce the hydrogen-rich fuel gas 22.
The mixture 57 is reformed in the reforming side of the gas-heated reactor 10. The so obtained effluent 60 is reformed further in the reactor 50, in presence of the air/steam mixture from line 61 and pre-heated in the heat exchanger 28. The gas/steam mixture 57 is partially reformed in the reactor 10 and conversion is completed in the subsequent reactor 50.
The hot reformed effluent 53 of the reactor 50 traverses the hot side of the gas heated reactor 10 to supply heat to the process of reforming of the mixture 57. As above described with reference to Fig. 1 , the gas-heated reactor 10 is preferably a shell-and-tube equipment wherein the hot side traversed by the effluent 53 is a shell side and the reforming side is a tube side.
The process gas 54 effluent from the hot side of the reactor 10 is cooled in the heat exchangers 11 and 12 and is treated in the shift section 13 and in the CO2 removal section 72 to produce the hydrogen-rich fuel 22.
The gas coolers 25, 26 and 27 are arranged to reduce the temperature of the shifted gas 24 and recover heat prior to the CO2 removal section 72. The heat removed from the shifted gas may be used to produce steam for the steam reforming and/or for adjusting the steam to carbon ratio in the shift section 13. For example, Fig. 2 illustrates that the heat exchangers 27, 12 and 11 are connected to a steam network fed with pressurized water 100 as a cooling medium, to obtain steam 300 which is mixed partly with the feed 17 and partly with the reformed gas entering the shift section 13.
A revamping procedure to implement the scheme of Fig. 2 involves the addition of the new reforming section 8 including the gas-heated reactor 10 and the new secondary reforming reactor 50. In order to cope with the increased amount of natural gas and air for the newly-added reforming section 8, a natural gas booster 30 and/or an air booster 31 may be installed, if the existing compressors do not provide adequate spare capacity. The revamping procedure may also include any of: addition of a desulphurization unit or upgrade of the existing section 2; upgrade of the existing carbon dioxide removal section 7; addition of the new carbon dioxide removal section 72.
In an interesting application, the compression of natural gas and/or the compression of air is performed, at least partially, in electric mode. This can be done by adding an electric booster to the existing natural gas compressor 1 and/or to the existing air compressor 41 , or by replacing one or both said compressors 1 , 41 with a fully electric compressor.
Third embodiment (Fig. 3)
Fig. 3 discloses an embodiment wherein the second reforming section 8 includes a gas-heated reformer 65 and a secondary reformer 58, and the gas-heated reformer 65 is heated by the effluent of the reformer 5.
The effluent 23 of the secondary reformer 5 is sent to the hot side (e.g. shell side) of the gas-heated reformer 65 to supply reforming heat for the mixed feed 57. Said mixed feed 57 includes the second portion 17 of natural gas and steam 20.
The effluent 66 of the hot side of the reformer 65 is sent to the cooling and shift section 6 and to the CO2 removal section 7 to generate the makeup gas 19. The secondary reformer 5 is a steam reformer which is fed with air 40 and steam 42.
The second portion of hydrocarbon 17 after addition of steam 20 is preheated in the exchanger 9 and reformed in the reforming side (e.g. tube side) of the gas heated reactor 65. The effluent 67 of the reforming side of the gas heated reactor 65 is further reformed in the secondary reformer 58 with air and steam introduced via line 44 to generate a reformed gas 68. The reformed gas 68 after suitable cooling in the heat exchangers 11 and 12 and shift conversion 13 is purified in the CO2 removal section 72 to obtain the hydrogen-rich fuel 22.
Fourth embodiment (Fig. 4)
Fig. 4 illustrates an embodiment wherein the second reforming section 8 is based on a stand-alone secondary reformer 158 fired with oxygen-enriched air.
The mixture of natural gas 17 and steam 20 is reformed in the secondary reformer 58 in presence of a mixture of oxygen-enriched air 67 and steam 142. The oxygen-enriched air 67 is produced by a vacuum pressure swing adsorption (VPSA) unit 71. The additional air feed for the VPSA unit 71 is provided by a booster 70. Optionally the VPSA unit 71 may be replaced by an air separation unit if cost is acceptable.
Fifth embodiment (Fig. 5)
Fig. 5 illustrates an embodiment similar to Fig. 4, wherein the stand-alone secondary reformer 158 is fed with air and no air enrichment is provided. The additional air feed is provided by a booster 31. The feed gas 170 fed to the secondary reformer 158 is taken downstream the primary reformer 4.
Fig. 6
Fig. 6 discloses a front-end for production of ammonia make-up gas 19. A hydrocarbon source such as natural gas 15 is compressed, cleaned in desulphurization unit 2 and added with steam 18. The so obtained mixture 16 is heated in a gas heater 8 and sent to a primary reformer 4. The partially reformed effluent 43 of the primary reformer 4 is sent to a secondary reformer 5 to completion of the reforming process.
The secondary reformer 5 is blown with an oxygen-containing stream 40. Said stream 40 may be air or oxygen-enriched air. The oxygen-enriched air may be provided by a VPSA unit or air separation unit (ASU).
The effluent of the secondary reformer 5 is sent to a cooling and shift section 6 and to a CO2 removal section 7 where carbon dioxide 63 is removed from the process gas. A portion of the hydrogen-rich gas obtained after CO2 removal is sent as fuel stream 22 to the primary reformer 4. The balance provides the makeup gas 19.
Example
A numerical example is given with reference to Fig. 3.
Steam to carbon ratio in the reforming section 8 is about 2.95.
Flow rate, composition and temperature of the hydrogen-rich fuel 22 supplied to primary reformer: 4393 kmol/h, 59.5%mol H2, 37.5%mol N2, 37.5%mol N2, 1.6%mol CH4, 50 °C.
Flow rate and temperature of the effluent 67 of the GHR 65: 4334 kmol/h and 633
Flow rate, composition and temperature of the reformed gas 68: 7450 kmol/h, 1 ,4%dry CH4 content, 860 °C.
CO2 emitted from the primary reformer 4: 9.6 t/h.
Total CO2 sequestrated in the CO2 removal sections 7 and 72: 117 t/h.
Temperature of the hot effluent 23: 955 °C. Temperature of the reformed gas 66: 790 °C.

Claims

1 ) A process for the production of a hydrogen-containing synthesis gas (19) comprising: a) providing a hydrocarbon feed (15), such as natural gas; b) a first portion (16) of said hydrocarbon feed is converted with a steam reforming process in a first reforming section (80) into a reformed gas (23) and said reformed gas (23) is further processed including at least steps of water-gas shift (6) and carbon dioxide removal (7), to obtain said synthesis gas (19); c) wherein the reforming process of step b) includes a primary reforming in a fired furnace (4) and a subsequent secondary reforming (5), the effluent of the secondary reforming being a hot reformed gas (23); the process further including: d) a second portion (17) of said hydrocarbon feed is subject to a parallel steam reforming process (10), which is performed in a second reforming section (8) and in parallel to the reforming process of step b), obtaining a reformed gas (21 ); e) the reformed gas (21 ) obtained from the parallel steam reforming (10) of step d) is further processed, including at least water-gas shift (13) and carbon dioxide removal (72), to obtain a hydrogen-rich gas (22); f) the hydrogen-rich gas (22) obtained at step e) is at least partially or preferably entirely sent as a fuel to the fired furnace (4) of said primary reforming of step c).
2) A process according to claim 1 , wherein at least part of the reforming heat for the parallel steam reforming process of step d) is recovered from the hot reformed gas (23) obtained after the secondary reforming (5) of step c).
3) A process according to claim 2, wherein said second portion of hydrocarbon feed (17) is reformed with steam (20) in a gas-heated reformer (10), wherein the gas-heated reformer (10) is heated by the hot reformed gas (23) of said step c).
4) A process according to claim 3, wherein said gas heated reformer (10) has a first side and a second side, wherein the first side is traversed by the mixture (57) of hydrocarbon feed (17) and steam (20) to be reformed, and the second side is traversed by said hot reformed gas (23), so that heat is transferred from said hot reformed gas (23) to said gas mixture (57) and said hot reformed gas (23) leaving the second side of the gas-heated reformer is sent to the further processing for the production of the hydrogen-containing synthesis gas (19).
5) A process according to claim 1 wherein: the second reforming section (8) includes a gas-heated reformer (10) and an additional reactor (50), which is a secondary reformer or a partial oxidation reactor; said second portion of the hydrocarbon feed (17) is mixed with steam (20) and the resulting mixture is introduced in a first side of said gas-heated reformer (10) of the second reforming section (8), where a first reforming step is performed and the feed is partially reformed; the partially reformed gas (60) obtained from said gas-heated reformer (10) is fed to said additional reactor (50) where a second reforming step is performed in the presence of air and steam and a reformed gas is obtained (53); the reformed gas (53) obtained after said second reforming step (50) is sent to a second side of said gas-heated reformer (10) to provide heat for the first reforming step; the cooled reformed gas (54) leaving the second side of the gas-heated reformer (10) is further processed to obtain said hydrogen-rich gas (22).
6) A process according to claim 5 wherein the further processing of said cooled reformed gas (54) includes a shift conversion (13) and a carbon dioxide purification (72).
7) A process according to claim 1 wherein said second reforming section includes a stand-alone secondary reformer (158) fired with oxygen-enriched air or with ambient air.
8) A process according to any of the previous claims wherein under steady-state operation of the process, said hydrogen-rich gas (22) provides at least 80%, preferably at least 90%, preferably 100% of the heat input of said fired furnace of the primary reformer (4).
9) A process according to any of the previous claims wherein the secondary reforming (5) of step c), which is part of the process gas production process, is an air-fired secondary reforming, said air-fired secondary reforming being not supplied with oxygen or oxygen-enriched air.
10) A process according to any of the previous claims wherein the carbon dioxide removed during the production of the hydrogen-containing process gas (19) and/or the carbon dioxide removed during the production of said hydrogen- rich fuel gas (22) are removed in a single apparatus, preferably wherein said apparatus operates with a pressure-swing adsorption (PSA) process.
11 ) A process according to any of the previous claims, including sequestration of the carbon dioxide (63) removed during the production of the process gas (19) and/or during the production of the hydrogen-rich fuel gas (22).
12) A process according to any of the previous claims wherein the shift conversion (13) performed at step e) includes a medium-temperature shift performed at a temperature of 200 °C to 300 °C preferably over a copperbased catalyst.
13) A process according to any of the previous claims wherein heat removed from the gas in the second reforming section (8) is used for the production of steam (300), and said steam is mixed with the second portion (17) of the feed and/or said steam is used to adjust a steam to carbon ratio in a shift reactor of the second reforming section.
14) A process according to any of the previous claims wherein the hydrogencontaining synthesis gas (19) produced in the first reforming section (80) is ammonia make-up gas, comprising hydrogen and nitrogen in a suitable proportion for the synthesis of ammonia.
15) 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 (80) comprising at least a primary reformer (4), which is a fired furnace, and an air-blown secondary reformer (5), said fired furnace being fired with a hydrocarbon fuel; the revamping procedure includes: installation of a new reforming section (8), arranged to operate in parallel to said existing reforming section (80), the new reforming section (8) being arranged to produce a hydrogen-rich gas (22); installation of a line arranged to feed a portion (17) of the available hydrocarbon process to said new reforming section (8); installation of a line arranged to send the hydrogen-rich gas (22) produced in the new reforming section (8) to said fired furnace of the existing primary reformer (4), to replace in part or in full the hydrocarbon fuel of said furnace.
16) A method according to claim 15, wherein the new reforming section (8) includes a gas heated reformer (10) and the method includes installation of a line arranged to take a hot reformed gas effluent from the first reforming section, before water-gas shift and removal of carbon dioxide, and arranged to send said hot gas to said gas-heated reformer (10) for use as a source of reforming heat.
17) A method according to claim 15 wherein the new reforming section includes any of: a stand-alone gas-heated reformer; a stand-alone secondary reformer; a gas-heated reformer and a partial oxidation reactor (50); a gas- heated reformer and a secondary reformer.
18) A method according to any of claims 15 to 17 wherein the new reforming section includes an air-blown secondary 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.
19) A method according to any of claims 15 to 18, 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, installing a booster in addition to an existing hydrocarbon feed compressor, revamping a hydrodesulfurization reactor (2) arranged to desulphurize the hydrocarbon feed (15) prior to a reformer section (8, 80), providing a partially or fully electric compression of an air feed and/or of a hydrocarbon feed.
PCT/EP2024/053921 2023-02-16 2024-02-15 A process for production of hydrogen gas WO2024170712A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015067436A1 (en) 2013-11-08 2015-05-14 Casale Sa Process for producing ammonia synthesis gas and a method for revamping a front-end of an ammonia plant
EP3363770A1 (en) 2017-02-15 2018-08-22 Casale Sa Process for the synthesis of ammonia with low emissions of co2 in atmosphere
WO2023089293A1 (en) * 2021-11-17 2023-05-25 Johnson Matthey Public Limited Company Method for retrofitting a hydrogen production unit

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015067436A1 (en) 2013-11-08 2015-05-14 Casale Sa Process for producing ammonia synthesis gas and a method for revamping a front-end of an ammonia plant
EP3363770A1 (en) 2017-02-15 2018-08-22 Casale Sa Process for the synthesis of ammonia with low emissions of co2 in atmosphere
EP3583067B1 (en) 2017-02-15 2021-09-08 Casale SA Process for the synthesis of ammonia with low emissions of co2 in atmosphere
WO2023089293A1 (en) * 2021-11-17 2023-05-25 Johnson Matthey Public Limited Company Method for retrofitting a hydrogen production unit

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