CN118215636A - Blue hydrogen production method and equipment - Google Patents

Abstract

The present application provides an apparatus and a method for producing a hydrogen-rich gas, the method comprising the steps of: steam reforming a hydrocarbon feed to synthesis gas; the synthesis gas is shifted and the shifted gas is directed to a hydrogen purification unit, the CO ₂ -rich off-gas from the hydrogen purification unit is subjected to carbon dioxide removal and the hydrogen-rich CO ₂ -lean off-gas is recycled to the process.

Description

Blue hydrogen production method and equipment

Technical Field

The present invention relates to an apparatus and a method for producing hydrogen from a hydrocarbon feed, and comprises: reforming, shift conversion, CO ₂ removal, and hydrogen purification. In particular, the present invention relates to an apparatus and a process for producing hydrogen from a hydrocarbon feed, wherein the hydrocarbon feed is reformed in a reforming unit to produce a synthesis gas, the synthesis gas is subjected to a shift conversion step, and the shifted gas is then treated in a hydrogen purification unit, such as a Pressure Swing Adsorption (PSA) unit, thereby withdrawing a hydrogen product and a CO ₂ -rich waste gas stream, and wherein CO ₂ is removed from the CO ₂ -rich waste gas stream, thereby producing a CO ₂ -lean stream, i.e. a CO ₂ -lean waste gas stream, which is fed to the reforming unit; for example, the CO ₂ -lean stream or a portion thereof is added as a feed and/or fuel to the reforming unit, or as fuel in a fired heater. The CO ₂ -lean stream, or a portion thereof, may also be added to the shift conversion step and/or the hydrogen purification unit. The CO ₂ -lean stream, or a portion thereof, may also be output, for example, external to the hydrogen purification unit, more specifically, external to the plant.

Background

With today's increasing demand and competitiveness of hydrogen production, great efforts are being made in developing optimized production of hydrogen plants with the aim of increasing overall energy efficiency and reducing capital costs. The need for more cost-effective hydrogen production has stimulated the development of technologies and catalysts for large-scale hydrogen production plants to benefit from economies of scale.

Recent innovations in hydrogen production technology and the development of new generation tip catalysts ensure high cost effectiveness of hydrogen production and high reliability of equipment, even in cases where single line capacity is large.

Applicant's WO 2020221642 A1 discloses an apparatus and method for producing hydrogen comprising autothermal reforming (ATR) for producing synthesis gas (syngas), water gas shift, CO ₂ removal of shift gas and hydrogen purification to produce hydrogen rich gas and an exhaust stream. The exhaust gas stream is recycled to, for example, an ATR, and the exhaust gas may be subjected to compression and membrane separation steps before this. When using a CO ₂ membrane separation unit, for example, in the exhaust gas stream, the permeate is a hydrogen-rich stream which is then sent to a hydrogen purification unit, such as a PSA unit, while the retentate is a hydrogen-lean stream which is recycled to the feed side of the ATR or to the feed side of the shift section.

It is desirable to improve this process for producing hydrogen.

WO 201687125 A1 discloses an incremental hydrogen production method of existing natural gas hydrogen production plants. Existing plants include steam reforming, water gas shift and hydrogen purification in a Pressure Swing Adsorption (PSA) unit to produce a first H ₂ stream and a PSA off-gas stream. PSA off-gas (first waste stream) is compressed, dried, and CO ₂ is removed from this stream in a low temperature CO ₂ separation unit. The remaining waste stream is produced and sent to a second PSA unit from which a second H ₂ stream is withdrawn, and a second PSA off-gas stream (second waste stream) that is sent as fuel gas to the steam reformer.

US2013156685 discloses a method for reducing the overall CO ₂ production of a hydrogen plant comprising recovering CO ₂ from the flue gas of a reformer (steam methane reformer, SMR). Three pre-reforming steps are performed to produce a hydrocarbon feed to the reformer. The residual stream from the PSA unit downstream of the reformer is sent to a CO ₂ separation unit from which an H2-rich stream, a CO ₂ stream, and a residual stream are produced. The residual stream is then recycled upstream of the reformer, or as fuel in the reformer. The citation does not mention at least: providing a reformer configuration other than a conventional SMR or ATR, providing a single pre-reformer (single stage pre-reforming), and providing at least one fired heater arranged to preheat the hydrocarbon feed before it is fed to the reformer.

It is also desirable to improve these methods and apparatus for producing hydrogen.

Summary of The Invention

It is therefore an object of the present invention to reduce the consumption of hydrocarbon feed and fuel in hydrogen plants and/or processes, thereby improving energy efficiency while increasing carbon dioxide capture and thus reducing CO ₂ emissions.

It is another object of the present invention to provide for better integration of CO ₂ removal in hydrogen manufacturing plants and/or processes.

The present invention addresses these and other objects.

Thus, in a first aspect, there is provided an apparatus (100) for producing an H ₂ -rich stream (8) from a hydrocarbon feed (1), the apparatus comprising:

-a reforming unit (110), the reforming unit (110) being arranged to receive a hydrocarbon feed (1, 2) and to convert it into a synthesis gas stream (3);

-a shift section (115, 150), said shift section (115, 150) suitably comprising a high or medium temperature shift unit (115), said shift section being arranged to receive the synthesis gas stream (3) from the steam reforming unit (110) and suitably shift it in a high or medium temperature shift step, thereby providing a shifted synthesis gas stream (5);

-a hydrogen purification unit (125) arranged to receive the shifted synthesis gas stream (5) and separate it into a high purity H ₂ stream as hydrogen product (8), and a CO ₂ rich waste gas stream (9);

-a CO ₂ removal section (180) for removing CO ₂ from a CO ₂ rich flue gas stream (9) to obtain a CO ₂ product stream (11) and a CO ₂ lean flue gas stream (17, 17', 17 "), wherein the apparatus is arranged to recycle the CO ₂ lean flue gas stream or a portion thereof (17, 17', 17") to at least the feed side of a reforming unit (110);

the apparatus further comprises:

-at least one fired heater arranged to preheat the hydrocarbon feed (1, 2) before the hydrocarbon feed (1, 2) is fed to the reforming unit (110) (e.g. ATR), and wherein the apparatus (100) is arranged to feed at least part of the CO ₂ -rich off-gas stream (9) from the hydrogen purification unit (125) or to feed at least part of the CO ₂ -lean off-gas stream (17, 17', 17 ") as fuel to the fired heater.

In a second aspect of the invention, there is also provided a process for producing an H ₂ -rich stream from a hydrocarbon feed using the apparatus defined herein, as further described below.

Further details of the invention are set forth below, in the accompanying drawings, aspects and in the dependent claims.

As used herein, the term "first aspect of the invention" refers to a device (system) according to the invention; the term "second aspect of the invention" refers to a method according to the invention.

As used herein, the term "comprising" also encompasses "comprising only", i.e. "consisting of.

As used herein, the term "suitably" means "optionally", i.e., optional embodiments.

As used herein, the term "at least a portion" means at least a portion, such as at least a portion of a given flow. Thus, the term "at least a portion" or "at least a portion" of a given flow refers to the entire flow or a portion thereof.

As used herein, the term "application" or simply "application" may be used interchangeably with the term "application" or simply "application".

Other definitions are provided in connection with one or more of the following embodiments.

In a specific embodiment, the apparatus is arranged to recycle said CO ₂ -lean exhaust stream, or a portion thereof, directly to at least the feed side of the reforming unit. In another specific embodiment, the apparatus is arranged to feed directly: at least a portion of the CO ₂ -rich exhaust stream or at least a portion of the CO ₂ -lean exhaust stream from the hydrogen purification unit is used as fuel for the fired heater.

As used herein, the term "directly" refers to an intermediate step or unit in which there is no change in the composition of the stream. For example, as shown in the figures, the apparatus 100 is arranged to recycle the CO ₂ lean exhaust stream 17, 17', 17″ or a portion thereof directly to at least the feed side of the reforming unit 110.

In one embodiment, the reforming unit is an autothermal reformer (ATR); a partial oxidation reformer (PO _x); a convection heating reformer, such as a Heat Exchanger Reformer (HER) or a Gas Heating Reformer (GHR); a Steam Methane Reformer (SMR), such as an electrically heated steam methane reformer (e-SMR); or a combination thereof, such as a combination of SMR and (HER), or a combination of SMR and ATR, or a combination of ATR and HER.

All of the above reforming units are well known in the art.

For example:

-in an autothermal reformer (ATR), the hydrocarbon feed is partially oxidized by oxygen and steam, followed by catalytic reforming; in autothermal reforming (ATR), the term Catalytic Partial Oxidation (CPO) is also contemplated herein, natural gas or other hydrocarbons being reacted with steam and an oxidant (air, oxygen enriched air or oxygen) in the presence of a nickel or noble metal based catalyst;

In the non-catalytic partial oxidation of natural gas (PO _X), solid feedstocks of light hydrocarbons, heavy hydrocarbons or coal (also called gasification) are reacted with an oxidizing agent (air, oxygen-enriched air or oxygen) and a reactor outlet temperature of up to 1400 ℃ is obtained;

a convection reformer may comprise one or more snap-in reforming tubes, such as an HTCR reformer, i.e. Bayonet reformers in which heat for reforming is transferred by convection and radiation;

The term SMR encompasses both traditional SMR and e-SMR; in a conventional SMR (also known as a tubular reformer), heat for reforming is transferred mainly by radiation in a radiant furnace; in an electrically heated steam methane reformer (e-SMR), an electrical resistance is used to generate the heat required for catalytic reforming. In particular, when using an e-SMR, power from green sources, such as power from wind, hydro and solar generation, may be utilized to further minimize the carbon dioxide footprint.

For more information on these reformers, details are provided herein by direct reference to applicant's patents and/or literature. For example, for tubular reforming and autothermal reforming, see generally "Tubular reforming and autothermal reforming ofnatural gas-an overview ofavailable processes", ibFuel Processing Technology 42 (1995) 85-107; for a description of HTCR, refer to EP 0535505; reference is made either to the description of HER, for example EP 2526045, or to the description of a combined ATR and HER process, for example EP 0983963. For a description of ATR and/or SMR (tubular reformer) for large scale hydrogen production, see for example article "Large-scale Hydrogen Production",Jens R.Rostrup-Nielsen and Thomas Rostrup-Nielsen",CATTECH,volume 6,pages 150–159(2002). for a description of the state of the art e-SMR, see for example WO 2019/228797 A1.

In one embodiment, the catalyst in the reforming unit is a reforming catalyst, such as a nickel-based catalyst. In one embodiment, the catalyst in the water gas shift reaction (i.e., in the shift section) is any catalyst active for the water gas shift reaction. The two catalysts may be the same or different. Examples of reforming catalysts are noble metals on Ni/MgAl₂O₄、Ni/Al₂O₃、Ni/CaAl₂O₄、Ru/MgAl₂O₄、Rh/MgAl₂O₄、Ir/MgAl₂O₄、Mo₂C、Wo₂C、CeO₂、Ni/ZrO₂、Ni/MgAl₂O₃、Ni/CaAl₂O₃、Ru/MgAl₂O₃、or Rh/MgAl₂O₃、Al₂O₃ supports, but other catalysts suitable for reforming are also conceivable. The catalytically active material may be Ni, ru, rh, ir or a combination thereof, while the ceramic coating may be Al ₂O₃、ZrO₂、MgAl₂O_3、CaAl₂O₃ or a combination thereof, possibly mixed with oxides of Y, ti, la or Ce. The maximum temperature of the reactor may be between 850 and 1300 ℃. The pressure of the feed gas may be 15-180 bar, preferably about 25 bar. The steam reforming catalyst is also referred to as a steam methane reforming catalyst or a methane reforming catalyst.

In a particular embodiment, the reforming unit is an autothermal reformer (ATR). ATR allows the plant and process to operate at low steam to carbon ratios, thereby reducing plant size. For example, the steam to carbon ratio of the synthesis gas supplied from the ATR to the shift section is less than 2.0, preferably 0.3 to 1.0.

As used herein, the term "feed side" refers to the inlet side or simply inlet. For example, the feed side of a reforming unit (e.g., ATR) refers to the inlet side of the ATR.

As used herein, the term CO ₂ -product stream refers to a stream containing 95% by volume or more, e.g., 99.5% carbon dioxide.

The CO ₂ lean exhaust stream is meant to comprise, for example: 85mol% H ₂、7mol％CH₄, 7mol% CO and 1mol% N ₂ +Ar. Thus, the CO ₂ -lean exhaust stream is hydrogen-rich, i.e., has over 80mol% H ₂, and is substantially free of carbon dioxide.

In one embodiment, the apparatus (100) is devoid of a CO ₂ removal section upstream of the hydrogen purification unit (125), arranged to receive the shifted gas stream (5) from the shift section. The apparatus is thus arranged to supply said hydrogen purification unit (125) directly, i.e. to feed said shifted synthesis gas stream (5) directly to said hydrogen purification unit (125),

It has been found advantageous to perform recycling such that the CO ₂ lean exhaust gas having a high hydrogen content is fed back to the steam reforming unit while avoiding the use of CO ₂ removal between the reforming unit and the hydrogen purification unit. This results in more methane being converted to hydrogen and CO to CO ₂. Advantages of the apparatus and method further include: in the case of the same amount of hydrogen produced, hydrocarbon feed consumption (e.g., natural gas consumption) may be reduced while increasing CO ₂ capture and thus reducing CO ₂ emissions. Furthermore, compared to the shifted syngas stream, the CO ₂ removal is performed in a much smaller stream of process gas (CO ₂ rich waste gas stream).

The CO ₂ product stream from the CO ₂ removal step may be stored or used for other purposes to reduce CO ₂ emissions to the atmosphere.

An improvement of the process is thus obtained, in particular by better integration of the CO ₂ removal process, providing an excellent blue hydrogen production process whereby carbon dioxide is removed while producing a hydrogen product.

The term "blue hydrogen" refers to the production of hydrogen from hydrocarbon feedstocks such as natural gas, with the concomitant capture of carbon and its storage or utilization.

In one embodiment, the CO ₂ removal section (180) is selected from: an amine wash unit, or a CO ₂ membrane, i.e., a CO ₂ membrane separation unit, a CO ₂ -PSA, or a cryogenic separation unit.

In particular, when a CO ₂ membrane separation unit is used, the permeate is a hydrogen-rich stream which can then be sent to a hydrogen purification unit, such as a PSA unit, while the retentate is a hydrogen-lean stream which is recycled to the feed side of the ATR or the feed side of the shift section, or the feed side of the membrane separation, i.e., the inlet side.

The CO ₂ removal section may also be a Benfield process or plant comprising an absorber for performing the gas absorption step and a regenerator for performing the carbonate regeneration step. The CO ₂ removal section may also be in the form of CO ₂ -PSA, as is well known in the art.

In one embodiment, the apparatus (100) further comprises one pre-reformer unit (140) arranged upstream of the reforming unit (110), the pre-reformer unit (140) being arranged to pre-reform the hydrocarbon feed (1) before the hydrocarbon feed (1) is fed to the steam reforming unit (110), and wherein the apparatus (100) is arranged to feed at least a part of the CO ₂ -lean exhaust stream (17, 17') to the feed side of the pre-reformer unit (140); and/or

-The apparatus (100) is arranged to feed at least a portion of the CO ₂ -lean exhaust gas stream (17) to the feed side of the shift section; and/or

The apparatus is arranged to feed at least a portion of the CO ₂ -lean exhaust stream to the feed side of the hydrogen purification unit (125).

As used herein, the terms pre-reformer, pre-reformer unit and pre-reforming unit are used interchangeably.

In one embodiment, the pre-reformer unit is an adiabatic pre-reformer unit.

By providing a single pre-reformer unit, e.g. an adiabatic pre-reformer unit, a simpler apparatus and method is provided. The associated capital expenditure (CapEx) and operating expenditure (OpEx) of providing additional prereformers and accompanying heat exchange units is eliminated.

As used herein, the feed side of a shift section refers to the inlet side of a high or medium temperature shift unit, or the inlet side of any downstream shift unit in the shift section, e.g. the inlet side of a medium temperature shift unit arranged downstream of the high temperature shift unit.

Recycling the CO ₂ lean exhaust stream to, for example, an ATR has the advantage of reducing the flow to the pre-reformer and thereby reducing its size. More specifically, the recycle of the lean CO ₂ flue gas increases hydrogen recovery, thereby reducing feed consumption. Thus, the size of the upstream apparatus can be reduced.

Recycling the CO ₂ lean exhaust stream to the shift section has the advantage of reducing ATR and prereformer size. This recycling option is preferably combined with a second H ₂ purification step of the off-gas, suitably upstream of the CO ₂ removal section, to reduce the H ₂ partial pressure.

In one embodiment, the apparatus has, i.e., is free of, a steam methane reforming unit (SMR) upstream of the ATR. Thus, the reforming section, i.e. the reforming unit therein, comprises an ATR and optionally also a pre-reformer unit, but no Steam Methane Reforming (SMR) unit, i.e. the use of e.g. a conventional SMR (also commonly referred to as radiant furnace or tubular reformer) is omitted. Thus, in one embodiment, the reforming unit is an ATR, with a pre-reformer unit arranged upstream. The use of ATR in combination with a prereforming unit, i.e. as a stand-alone ATR system, is a simple and energy efficient solution in the reforming section.

This has significant advantages in terms of energy consumption and equipment size, since it is now possible to operate at steam-to-carbon molar ratios well below 1, among other things, thereby significantly reducing the amount of steam carried in the equipment/process, as further described above.

Suitably, the apparatus further comprises a hydrogenator unit and a sulphur absorption unit arranged upstream of said prereformer unit, wherein said apparatus is arranged to feed at least a portion of the CO ₂ lean waste gas stream to the feed side of the hydrogenator unit.

In one embodiment, the apparatus further comprises:

-a compressor, i.e. a CO ₂ -rich exhaust gas recirculation compressor, arranged for compressing the CO ₂ -rich exhaust gas stream (9), said compressor being adapted upstream of the CO ₂ removal section (180); and optionally a compressor adapted downstream of the CO ₂ removal section (180) for recycling the CO ₂ lean gas stream (17, 17') or a portion thereof to the feed side of the reforming unit (140), and/or to the feed side of the shift section, and/or to the feed side of the pre-reformer unit (140), and/or to the feed side of the hydrogen purification unit (125).

The present invention also reduces the power consumption of the CO ₂ rich exhaust gas recycle compressor by adding the CO ₂ lean exhaust gas back to the reforming section, e.g., the prereformer and/or ATR.

At least a portion of the compressed portion of the CO ₂ -lean exhaust stream is used in the process by being directly a part of the hydrocarbon feed or process gas that is treated in, for example, a pre-reformer, or ATR, or shift section.

Suitably, the high temperature shift unit comprises a promoted zinc-aluminium oxide based high temperature shift catalyst, preferably arranged within the HTS unit in the form of one or more catalyst beds, and preferably wherein the promoted zinc-aluminium oxide based HT shift catalyst has a Zn/Al molar ratio in its active form in the range of 0.5 to 1.0, and an alkali metal content in the range of 0.4 to 8.0wt% and a copper content in the range of 0-10% based on the weight of the oxidation catalyst.

In conventional hydrogen plants, standard use of iron-based high temperature shift catalysts requires a steam to carbon ratio of about 3.0 to avoid the formation of iron carbide.

(1)

The formation of iron carbide weakens the catalyst particles and may lead to catalyst disintegration and increased pressure drop. Iron carbide will catalyze the formation of Fischer-Tropsch byproducts

(2)

The fischer-tropsch reaction consumes hydrogen and thus reduces the efficiency of the shift section.

However, according to the invention, non-Fe catalysts are used, for example promoted zinc-aluminium oxide based catalysts. For example, the number of the cells to be processed,The SK-501Flex ^TM HT shift catalyst enables the reforming section and the high temperature shift section to operate at steam to carbon ratios as low as 0.3.

Thus, the apparatus and/or process of the present invention operating at steam to carbon ratios as low as 0.3 is in contrast to today's conventional hydrogen production plants based on reforming and/or shift sections operating at steam to carbon ratios of about 1.5 or above. In an advantageous embodiment of the process, the active form of the zinc-aluminum oxide based catalyst comprises a mixture of zinc aluminate spinel and zinc oxide in combination with an alkali metal selected from Na, K, rb, cs and mixtures thereof, and optionally Cu. As described above, the catalyst may have a Zn/Al molar ratio in the range of 0.5 to 1.0, an alkali metal content in the range of 0.4 to 8.0wt% and a copper content in the range of 0-10% based on the weight of the oxidation catalyst.

The high temperature shift catalyst used in accordance with the process of the present application is not limited by the stringent requirements on steam to carbon ratio, which allows the steam to carbon ratio of the shift section and the reforming section to be reduced.

Again, the amount of steam carried in the plant and/or process is significantly reduced, thereby reducing plant size and energy consumption. More specifically, steam to carbon ratios less than 2.0 have several advantages. In general, decreasing the steam to carbon ratio results in a decrease in the feed and steam flow through the reforming section and downstream cooling and hydrogen purification sections. The low steam to carbon ratio in the reforming section and shift section also enables higher syngas throughput than the high steam to carbon ratio. The reduced mass flow through these sections means smaller equipment and tubing sizes. The reduction in mass flow also results in a reduction in the production of low temperature heat which is generally not available. This means that it is possible to reduce capital expenditure (Capex) and operating expenditure (OpEx).

Since the steam-to-carbon ratio requirements of the present process in the high temperature shift step are significantly reduced compared to known techniques, the present invention can reduce the steam-to-carbon ratio through the front end to, for example, 0.6 or as low as possible, depending on the possible shift scheme, as further explained below. The advantage of having a low steam to carbon ratio in the ATR and the overall process is that smaller equipment is required at the front end due to the lower total mass flow through the equipment.

It should be understood that the term "front end" refers to the reforming section. It should also be understood that the reforming section is a section of the apparatus that includes units up to and including a reforming unit, such as an ATR, or a pre-reformer unit and ATR, or a hydrogenator and sulfur absorber and a pre-reformer unit and ATR.

Preferably, the apparatus may further comprise an Air Separation Unit (ASU) arranged to receive the air stream and to generate an oxygen stream, which is then fed to the ATR via a conduit.

The apparatus preferably further comprises conduits for adding steam to the hydrocarbon feed, the oxygen-containing stream and the ATR, and optionally further comprises conduits for adding to the inlet of the reforming section (e.g. to the main hydrocarbon feed), and also conduits for adding to the inlet of the shift section (in particular the HTS unit), and/or conduits for adding to an additional shift unit downstream of the HTS unit, as will be described further below.

According to the invention, the plant further comprises at least one fired heater arranged to preheat the hydrocarbon feed (1, 2) prior to feeding the hydrocarbon feed to a reforming unit (110), such as an ATR, wherein the plant (100) is arranged to feed at least a part of the CO ₂ -rich waste gas stream (9) or at least a part of the CO ₂ -lean waste gas stream (17, 17') from the hydrogen purification unit (125) as fuel to the fired heater.

This enables low carbon emissions to be achieved from the flue gas produced by combustion of the fired heater. Separate fuel gases and/or hydrogen fuel gas are suitable for use in the fired heater along with the combustion air. The consumption of fuel gas (e.g., natural gas) normally used for combustion is significantly reduced or eliminated. The fired heater may be used, for example, for steam superheating or the like, in addition to preheating the hydrocarbon feed gas to the prereformer and, for example, the ATR.

Suitably, the CO ₂ -lean exhaust stream (17, 17 ") is mixed with a hydrocarbon feed (2) prior to being fed to a steam reforming unit (110), such as the feed side of an ATR; or the CO ₂ -lean exhaust stream (17, 17') is mixed with the hydrocarbon feed (1) before being fed to the feed side of the pre-reformer unit (140).

It should therefore be appreciated that the CO ₂ lean exhaust gas may be directed to, for example, the ATR and/or mixed with the hydrocarbon feed prior to entering the ATR. Also suitably, the CO ₂ -lean exhaust stream is mixed with the hydrocarbon feed before being fed to the feed side of the pre-reformer unit.

In another embodiment, the hydrogen purification unit is selected from a Pressure Swing Adsorption (PSA) unit, a hydrogen membrane, or a cryogenic separation unit.

In another embodiment, the apparatus is devoid of a second (additional) hydrogen purification unit, such as a second PSA unit, downstream of the CO ₂ removal section. Thus, it is not necessary to further enrich the CO ₂ -lean exhaust gas into a separate H ₂ product, as the CO ₂ -lean exhaust gas may already have the required specifications for recycling to at least the feed side of the reforming unit. Thus, the lean CO ₂ exhaust gas is directly recycled to at least the feed side of the reforming unit. In other words, according to this embodiment, the apparatus is arranged to recycle the CO ₂ -lean exhaust gas stream or a part thereof directly to the feed side of at least the reforming unit, i.e. a conduit is provided for recycling the CO ₂ -lean exhaust gas stream or a part thereof directly to the feed side of at least the reforming unit (110).

In another embodiment, the shift section includes one or more additional high temperature shift units in series.

In another embodiment, the shift section further comprises one or more additional shift units downstream of the high temperature shift unit. In a specific embodiment, the one or more additional shift units are one or more medium temperature shift units and/or one or more low temperature shift units.

Providing additional shift units or shift steps increases the flexibility of the apparatus and/or process when operating at low steam to carbon ratios. A low steam to carbon ratio may result in a sub-optimal shift conversion, meaning that in some embodiments, it may be advantageous to provide one or more additional shift steps. The one or more additional shift steps may include a Medium Temperature (MT) shift and/or a Low Temperature (LT) shift and/or a high temperature shift. In general, the more CO is converted in the shift step, the more H ₂ is obtained and the smaller the front end is required.

This can also be seen from the exothermic shift reaction:

as described above, steam may optionally be added before and after the high temperature shift step, for example before one or more subsequent MT or LT shift and/or HT shift steps, to maximize performance of the subsequent HT, MT and/or LT shift steps.

Having two or more high temperature shift steps in series (e.g., a high temperature shift step comprising two or more shift reactors in series, e.g., with cooling and/or steam addition therebetween) may be advantageous because it may increase shift conversion at high temperatures, which may reduce the required shift catalyst volume, and thus may reduce Capex. In addition, the high temperature reduces the formation of methanol, a typical shift step byproduct.

Preferably, the MT and LT shift steps can be performed over a promoted copper/zinc/alumina catalyst. For example, the low temperature shift catalyst type may be LK-821-2, which is characterized by high activity, high strength, and high sulfur toxicity resistance. A top layer of special catalyst may be installed to trap chlorine that may be present in the gas and prevent droplets from reaching the shift catalyst.

The MT shift step may be carried out at a temperature of 190-360 ℃.

The LT shift step may be performed at a temperature of from T _dew +15 to 290 c, for example from 200 to 280 c. For example, the low temperature shift inlet temperature is T _dew +15-250deg.C, such as 190-210 deg.C.

Reducing the steam/carbon ratio results in a decrease in the dew point of the process gas, which means that the inlet temperature of the MT and/or LT shift step can be reduced. A lower inlet temperature may mean less CO evolution from the shift reactor, which is also advantageous for the plant and/or process.

In a second aspect of the invention, there is also provided a process for producing a hydrogen product (8) from a hydrocarbon feed (1, 2), the process comprising the steps of:

Providing an apparatus (100) according to any one of the preceding embodiments of the first aspect of the invention;

Supplying a hydrocarbon feed (2) to a reforming unit (110), such as an ATR, and converting it into a synthesis gas stream (3);

the synthesis gas stream (3) from the reforming unit (110) is supplied to a shift section, suitably a high or medium temperature shift step (115), and is shifted in a shift step (115) to provide a shifted synthesis gas stream (5);

The shifted gas stream (5) from the shift section is supplied to a hydrogen purification unit (125) and separated into a high purity H ₂ stream as the hydrogen product (8) and a CO ₂ rich off-gas stream (9); and

The method further comprises the steps of:

-optionally providing a step for compressing said CO ₂ -rich offgas stream (9), i.e. a compression step of CO ₂ -rich offgas; and a CO ₂ removal step in a CO ₂ removal section (180), thereby providing a step for removing CO ₂ from the thus optionally compressed CO ₂ rich waste gas stream (9) to obtain a CO ₂ rich waste gas stream as CO ₂ product stream (11) and CO ₂ lean waste gas stream (17, 17', 17 "), said optional step for compressing said CO ₂ rich waste gas stream (9) being performed prior to said CO ₂ removal section (180), and

-Feeding the CO ₂ -lean exhaust stream or a portion thereof (17, 17') to the feed side of the reforming unit (110), and/or the feed side of the shift section, and/or the feed side of the hydrogen purification unit (125), and/or the feed side of an optional pre-reformer unit (140) arranged upstream of the reforming unit (110), and/or as fuel for at least one fired heater arranged to preheat the hydrocarbon feed (1, 2) prior to feeding it to the reforming unit (110), optionally via a further compression step.

As described above in connection with the first aspect of the invention, the apparatus and/or process of the invention may be operated at steam to carbon ratios as low as 0.3, the low steam to carbon ratios in the reforming and shift sections (i.e. optionally including any steam added to the shift section) being able to achieve higher syngas throughput than high steam to carbon ratios.

In another embodiment according to the second aspect of the application, the temperature in the high temperature shift step is in the range of 300-600 ℃, such as 360-470 ℃, or such as 345-550 ℃. This means that according to the process of the application, a high temperature shift reaction can be performed on a feed having a much lower steam to carbon ratio than is possible with the known process. For example, the high temperature shift inlet temperature may be 300-400 ℃, such as 350-380 ℃.

For example, when operating with an ATR, the carbon feed to the ATR is mixed with oxygen and additional steam in the ATR and a combination of at least two reactions occurs. These two reactions are combustion and steam reforming.

Combustion zone:

(3)

(4)

Hot zone and catalytic zone:

(5)

(6)

The combustion of methane to form carbon monoxide and water (reaction (4)) is a highly exothermic process. After the oxygen has been fully converted, excess methane may be present at the exit of the combustion zone.

The hot zone is the part of the combustion chamber where the hydrocarbons are further converted by a homogeneous gas phase reaction, mainly reactions (5) and (6). The endothermic steam reforming of methane (5) consumes most of the heat generated in the combustion zone.

The combustion chamber may be followed by a fixed catalyst bed, i.e. a catalytic zone, wherein the final hydrocarbon conversion takes place by heterogeneous catalytic reactions. At the outlet of the catalytic zone, the synthesis gas preferably approaches the equilibrium of reactions (5) and (6).

By means of the present invention, it is possible to operate the apparatus and/or the method without adding additional steam between the reforming step and the high temperature shift step.

Suitably, the space velocity in the ATR is low, for example less than 20000Nm ³C/m³/h, preferably less than 12000Nm ³C/m³/h, most preferably less than 7000Nm ³C/m³/h. Space velocity is defined as the volumetric flow of carbon per unit volume of catalyst and is therefore independent of the conversion in the catalyst zone.

Any embodiment of the first aspect (apparatus) of the invention may be used in combination with any embodiment of the second aspect (method) of the invention and vice versa. Any of the associated benefits of the embodiments according to the first aspect of the present invention may be used in combination with the embodiments according to the second aspect of the present invention.

The advantages of the application include:

In the case of the same amount of hydrogen produced, the consumption of hydrocarbon feed (for example natural gas) can be reduced, while increasing the CO ₂ capture, thus reducing CO ₂ emissions;

Since part of the lean CO ₂ exhaust gas is also used as fuel for the fired heater, the carbon emissions of the flue gas produced by the fired heater are low;

by adding the CO ₂ lean exhaust gas back to the reforming unit, the power consumption of the CO ₂ rich exhaust gas recirculation compressor for compressing the CO ₂ rich exhaust gas stream is reduced.

Brief description of the drawings

The only figure (fig. 1) shows the layout of an ATR-based hydrogen production process and apparatus according to an embodiment of the invention.

Detailed Description

Fig. 1 shows an apparatus 100 wherein a hydrocarbon feed 1, i.e. a main hydrocarbon feed 1, e.g. natural gas, is fed to a reforming section comprising a pre-reforming unit 140 and a reforming unit, here shown as an autothermal reformer 110. The reforming section may also include a hydrogenator and sulfur absorber unit (not shown) upstream of the pre-reforming unit 140. Hydrocarbon vapor 1 is mixed with vapor 13. The resulting hydrocarbon feed 2 is fed to the ATR110, as are oxygen 15 and steam 13. The oxygen stream 15 is produced by an Air Separation Unit (ASU) 145, with air 14 being fed to the air separation unit 145. In ATR110, hydrocarbon feed 2 is converted to synthesis gas stream 3, which is then sent to shift sections 115, 150.

The shift section includes, for example, a High Temperature Shift (HTS) unit 115, wherein additional or extra steam 13' may also be added upstream. Additional shift units, such as a Low Temperature Shift (LTS) unit 150, may also be included in the shift section. It should be appreciated that the shift section may include any one of HTS, MTS, and LTS, or a combination thereof. Additional or extra steam 13' may also be added downstream of HTS unit 115 but upstream of cryogenic shift unit 150. The shifted gas stream 5 is then fed (e.g., directly fed) from the shift section to a hydrogen purification unit 125, such as a PSA unit, which produces a high purity H ₂ stream as hydrogen product 8 and a CO ₂ rich off-gas stream 9. The CO ₂ -rich exhaust gas recycle stream 9 is directed via a recycle compressor (not shown) to the CO ₂ removal section 180, producing a CO ₂ product stream 11 from the CO ₂ removal section 180, and a CO ₂ -lean exhaust gas stream 17, 17', 17". The apparatus 100 is arranged to recycle the CO ₂ -lean exhaust stream 17, 17', 17", or a portion thereof, for example directly to the feed side of the pre-reformer 140, or the feed side of the reforming unit (here ATR 110), or the shift section (not shown). The apparatus 100 further comprises at least one fired heater (not shown) arranged to preheat the hydrocarbon feed 1,2 before it is fed to the pre-reforming unit 140 or the reforming unit 110, the apparatus (100) being arranged to feed at least a part of the CO ₂ rich exhaust gas stream 9 or at least a part of the CO ₂ lean exhaust gas stream 17, 17', 17 "from the hydrogen purification unit 125 as fuel (e.g. direct feed) to the fired heater.

Examples

In the method and apparatus 100 for removing carbon dioxide from a CO ₂ -rich syngas 5, after removal of CO ₂ in the CO ₂ removal section 180, a CO ₂ lean flue gas 17 and a CO ₂ product stream 11 are produced. The composition of the CO ₂ lean exhaust gas may be as follows: 85mol% of hydrogen, 7mol% of methane, 7mol% of CO and 1mol% of nitrogen and argon. The lean CO ₂ exhaust 17 is directly recycled back to the reforming unit 110, here specifically exemplified as an ATR, which further has an upstream pre-reformer unit 140. This results in more reforming of methane into hydrogen and conversion of CO to CO ₂ in the shift units 115, 150. Benefits of doing so include: in the case of the same amount of hydrogen produced, consumption of hydrocarbon feed (e.g., natural gas) can be reduced while increasing the amount of CO ₂ captured, thereby reducing CO ₂ emissions. A portion of the lean CO ₂ exhaust gas is also used as fuel for the fired heater. This results in lower carbon emissions from the flue gas produced in the fired heater. Furthermore, by adding the CO ₂ lean exhaust gas back to the reforming unit 110, here ATR, the power consumption of a compressor arranged for compressing said CO ₂ rich exhaust gas stream 9, i.e. a CO ₂ rich exhaust gas recirculation compressor (not shown in the figures) is reduced.

Claims (11)

1. An apparatus (100) for producing a hydrogen product (8) from a hydrocarbon feed (1), the apparatus comprising:

-a reforming unit (110), the reforming unit (110) being arranged to receive a hydrocarbon feed (1, 2) and to convert it into a synthesis gas stream (3);

-a shift section (115, 150) arranged to receive and shift the synthesis gas stream (3) from the steam reforming unit (110) to provide a shifted synthesis gas stream (5);

-a hydrogen purification unit (125) arranged to receive the shifted synthesis gas stream (5) and separate it into a high purity H ₂ stream as hydrogen product (8), and a CO ₂ rich waste gas stream (9);

-a CO ₂ removal section (180) for removing CO ₂ from a CO ₂ rich flue gas stream (9) to obtain a CO ₂ product stream (11) and a CO ₂ lean flue gas stream (17, 17', 17 "), wherein the apparatus is arranged to recycle the CO ₂ lean flue gas stream or a portion thereof (17, 17', 17") to at least the feed side of a reforming unit (110);

Wherein the apparatus further comprises:

-at least one fired heater arranged to preheat the hydrocarbon feed (1, 2) before the hydrocarbon feed (1, 2) is fed to the reforming unit (110), and wherein the apparatus (100) is arranged to feed at least a portion of the CO ₂ -rich waste gas stream (9) or at least a portion of the CO ₂ -lean waste gas stream (17, 17', 17 ") from the hydrogen purification unit (125) as fuel to the fired heater.

2. The apparatus of claim 1, wherein:

-said shift section (115, 150) comprises a high or medium temperature shift unit (115).

3. The apparatus according to any one of claims 1-2, wherein the reforming unit is an autothermal reformer (ATR); a partial oxidation reformer (PO _x); a convection heating reformer, such as a Heat Exchanger Reformer (HER) or a Gas Heating Reformer (GHR); a Steam Methane Reformer (SMR), such as an electrically heated steam methane reformer (e-SMR); or a combination thereof, such as a combination of SMR and (HER), or a combination of SMR and ATR, or a combination of ATR and HER.

4. A plant according to any one of claims 1-3, wherein the plant is arranged to provide the shifted synthesis gas stream (5) directly to the hydrogen purification unit (125).

5. The apparatus according to any one of claims 1-4, wherein the CO ₂ removal section (180) is selected from: an amine wash unit, or a CO ₂ membrane, i.e., a CO ₂ membrane separation unit, a CO ₂ -PSA, or a cryogenic separation unit.

6. The apparatus of any one of claims 1-5, wherein

-The apparatus (100) further comprises a pre-reformer unit (140) arranged upstream of the reforming unit (110), the pre-reformer unit (140) being arranged to pre-reform (110) the hydrocarbon feed (1) before the hydrocarbon feed (1) is fed to the reforming unit (110), and wherein the apparatus (100) is arranged to feed at least a portion (17, 17') of the CO ₂ -lean exhaust stream to the feed side of the pre-reformer unit (140); and/or

-The apparatus (100) is arranged to feed at least a portion (17) of the CO ₂ -lean exhaust stream to the feed side of the shift section; and/or

-The apparatus is arranged to feed at least a portion of the CO ₂ lean exhaust stream to the feed side of a hydrogen purification unit (125).

7. The apparatus of any of claims 1-6, further comprising:

-a compressor, i.e. a CO ₂ -rich exhaust gas recirculation compressor, arranged for compressing the CO ₂ -rich exhaust gas stream (9), said compressor being adapted upstream of the CO ₂ removal section (180); and an optional compressor adapted downstream of the CO ₂ removal section (180) for recycling the CO ₂ lean gas stream (17, 17') or a portion thereof to the feed side of the reforming unit (140), and/or to the feed side of the shift section, and/or to the feed side of the pre-reformer unit (140), and/or to the feed side of the hydrogen purification unit (125).

8. The apparatus according to any of claims 6-7, wherein the reforming unit (110) is an ATR, upstream of which a pre-reformer unit (140) is arranged.

9. The apparatus (100) according to any one of claims 1-8, wherein the hydrogen purification unit (125) is selected from a Pressure Swing Adsorption (PSA) unit, a hydrogen membrane or a cryogenic separation unit.

10. The apparatus according to any one of claims 1-9, wherein the apparatus is arranged to recycle the CO ₂ -lean exhaust stream (17, 17') or a portion thereof directly to at least the feed side of a reforming unit (110).

11. A process for producing a hydrogen product (8) from a hydrocarbon feed (1, 2), the process comprising the steps of:

-providing a device (100) according to any one of the preceding claims;

supplying a hydrocarbon feed (2) to a reforming unit and converting it into a synthesis gas stream (3);

The synthesis gas stream (3) from the reforming unit (110) is supplied to a shift section and is shifted in a shift step, suitably a high or medium temperature shift step (115), thereby providing a shifted synthesis gas stream (5);

The shifted gas stream (5) from the shift section is supplied to a hydrogen purification unit (125) and separated into a high purity H ₂ stream as hydrogen product (8) and a CO ₂ rich off-gas stream (9); and is also provided with

The method further comprises the steps of:

Optionally providing a step for compressing said CO ₂ -rich offgas stream (9), i.e. a compression step of CO ₂ -rich offgas; and a CO ₂ removal step in a CO ₂ removal section (180), thereby providing a step for removing CO ₂ from the CO ₂ rich waste gas stream (9) thus optionally compressed, to obtain a CO ₂ rich waste gas stream and a CO ₂ lean waste gas stream (17, 17', 17 ") as CO ₂ product stream (11), said optional step for compressing said CO ₂ rich waste gas stream (9) being performed prior to said CO ₂ removal section (180), and

-Feeding the CO ₂ -lean exhaust stream or a portion thereof (17, 17') to the feed side of the reforming unit (110), and/or the feed side of the shift section, and/or the feed side of the hydrogen purification unit (125), and/or the feed side of an optional pre-reformer unit (140) arranged upstream of the reforming unit (110), and/or as fuel for at least one fired heater arranged to preheat the hydrocarbon feed (1, 2) prior to feeding it to the reforming unit (110), optionally via a further compression step.