Hydrogen production apparatus and process with improved cryogenic CO2 removal unit operation

Abstract

The present invention provides an apparatus and method for producing a hydrogen-rich gas, the method comprising the steps of: subjecting a hydrocarbon feed to steam reforming to produce a synthesis gas; shifting the synthesis gas and delivering the shifted gas to a hydrogen purification unit; cO2-rich waste gas from the hydrogen purification unit is subjected to carbon dioxide removal in a low-temperature CO2 removal section; and recirculating the CO2-depleted hydrogen-rich exhaust gas to the process. A drying unit is provided upstream of the CO2 removal section to add the regeneration gas produced in the plant and process.

Description

Technical Field

[0001] The present invention relates to an apparatus and method for producing hydrogen from a hydrocarbon feedstock, including reforming, shift conversion, purifying hydrogen in the case of generating waste gas, and removing CO2 from the waste gas at low temperature. Background Art

[0002] Low-temperature CO2 removal technology, especially the CO2 removal technology based on separating CO2 from the waste gas generated by the hydrogen purification unit of a hydrogen production apparatus and process in a cryogenic unit, requires the waste gas to be dried before being fed into the cryogenic unit. The hydrogen purification unit is usually a pressure swing adsorption unit (PSA unit), and its feedstock is the syngas (shifted syngas) after reforming and water gas shift. The PSA unit produces hydrogen products and PSA waste gas, and the PSA waste gas is usually used as fuel for the burner of a fired heater or the burner of an upstream reforming unit (usually a conventional steam methane reformer (SMR), also known as a tubular reformer or reforming furnace).

[0003] WO 2016187125 A1 discloses a process for incrementally producing hydrogen using an existing natural gas hydrogen production apparatus. The existing apparatus includes steam reforming, water gas shift, and hydrogen purification in a pressure swing adsorption (PSA) unit, thereby producing a first hydrogen stream and a PSA waste stream. The PSA waste gas (the first waste stream) is compressed, dried, and then CO2 is removed from the stream in a low-temperature CO2 separation unit. A remaining waste stream is generated and sent to a second PSA unit, from which a second H2 stream is extracted, as well as a second PSA waste stream (the second waste stream), which is sent as fuel gas to the steam reformer. The compressed first waste stream is dried in an adsorption bed dryer, which is regenerated by a nitrogen stream.

[0004] WO 0027505 A1 discloses a process for recovering CO2 and H2 from the PSA waste gas of a hydrogen production apparatus. First, the PSA waste gas is fed into an absorber, where a solvent is used to remove CO2. A CO2-rich solvent and a compressed waste gas rich in hydrogen are generated. The solvent that has absorbed CO2 is transported to a flash unit to recover the concentrated CO2 product. The regenerated solvent is then recycled to the absorber. The liquefaction unit receives the CO2 from the flash unit and liquefies it, while the compressed waste gas rich in hydrogen is directed to a second PSA unit.

[0005] US2009298957 A1 discloses a process for co-producing hydrogen and carbon dioxide from a hydrocarbon mixture, in which the residual PSA is treated to produce a carbon dioxide-rich fluid. The PSA off-gas is dried in a drying unit and then liquefied to produce CO2. The purge gas stream containing non-condensable compounds from the liquefaction process is then treated in a permeation module, thereby producing a hydrogen-rich permeate, which is recycled to the inlet of the PSA unit. A portion of this permeate is diverted to the drying unit for regenerating the dryer and then re-added to the non-diverted portion and recycled to the PSA unit. Summary of the Invention

[0006] There is a desire to provide an improved integrated scheme for hydrogen production equipment and processes, including cryogenic separation of CO2 from the off-gas withdrawn from the hydrogen purification unit of the process and equipment.

[0007] Accordingly, in a first aspect of the present invention, there is provided an apparatus (100) for producing a hydrogen product (8) from a hydrocarbon feed (1), the apparatus comprising:

[0008] - a reforming unit (110) arranged to receive the hydrocarbon feed (1, 2) and convert it into a synthesis gas stream (3);

[0009] - a shift section (115, 150) arranged to receive the synthesis gas stream (3) from the steam reforming unit (110) and shift it into a shifted synthesis gas stream (5);

[0010] - a hydrogen purification unit (125) arranged to receive the shifted synthesis gas stream (5) and separate it into a high-purity H2 stream as the hydrogen product (8) and a CO2-rich off-gas stream (9);

[0011] - a steam header arranged to receive steam generated by cooling at least any one of the synthesis gas stream (3) and the shifted synthesis gas stream (5);

[0012] - a CO2-rich off-gas recycle compressor (185) arranged to receive the CO2-rich off-gas stream (9) and compress it into a compressed CO2-rich off-gas stream (9');

[0013] - A drying unit (190) which is arranged to receive the compressed CO₂-rich waste gas stream (9') and provide a dried and compressed CO₂-rich waste gas stream (9"); the drying unit (190) is further arranged to receive a regeneration gas feed stream (19) and extract a regeneration gas product stream (19'); the drying unit (190) further comprises: a heat exchange unit which is arranged to preheat the regeneration gas feed stream (19) by indirectly cooling a heat exchange medium selected from any one of the following: steam (13") from the steam header, a synthesis gas stream (3), a shifted synthesis gas stream (5), and combinations thereof; and provide a cooled heat exchange medium, namely steam condensate (13''') or cooled syngas, namely cooled synthesis gas stream (3) or cooled shifted synthesis gas stream (5);

[0014] - A low-temperature CO₂ removal section (180) which is arranged to receive the dried and compressed CO₂-rich waste gas stream (9") to remove CO₂ from the CO₂-rich waste gas stream (9) or from the dried and compressed CO₂-rich waste gas stream (9"), and at least provide: a CO₂ product stream (11) and a CO₂-depleted waste gas stream (17, 17', 17").

[0015] Furthermore, according to a second aspect of the present invention (as described below), a method for producing a H₂-rich stream from a hydrocarbon feed using the apparatus described herein is provided.

[0016] Further details of the present invention will be set forth in the following description, the drawings, the aspects, the embodiments, and the corresponding dependent claims.

[0017] As used herein, the term "the first aspect of the present invention" refers to the apparatus (system) according to the present invention; the term "the second aspect of the present invention" refers to the method according to the present invention.

[0018] As used herein, the term "comprising" also encompasses "consisting only of", i.e., "consisting of".

[0019] The article "a" or "an" used herein means "one or more", or "at least one" can be used interchangeably, i.e., it encompasses both the singular and plural forms. For example, the term "a reforming unit" means one or more reforming units. For example, the reforming unit is a combination of an autothermal reformer (ATR) described below and a heat exchange reformer (HER) described below. For example, the reforming unit is an ATR, for example an ATR with an upstream pre-reformer, and the same applies to the definitions below.

[0020] As used herein and as is well known in the art, the term "syngas" refers to "synthesis gas", i.e., a gas containing CO, CO₂, and H₂. This term may sometimes also be referred to as "process gas".

[0021] As used herein, the term "equipment / process" refers to equipment and / or process. "Equipment" shall be understood to refer to the equipment for producing hydrogen products and may be used interchangeably with the term "hydrogen equipment" or "hydrogen production equipment".

[0022] As used herein, the term "and / or", with respect to a particular embodiment, refers to any one of three options. The term "and / or" may be used interchangeably with the term "at least one of three options".

[0023] As used herein, the term "suitably" means "optionally", i.e., an optional embodiment.

[0024] As used herein, the term "the present invention" or simply "invention" may be used interchangeably with the term "the present application" or simply "application".

[0025] As used herein, the term "drying unit" is well known in the art and refers to a unit arranged upstream of the low-temperature CO2 removal section for removing water vapor from a gas (here, a compressed CO2-rich waste gas stream). The drying unit can use a variety of techniques to remove water vapor from the gas stream, including: adsorbing and retaining water molecules using materials such as silica gel or molecular sieves; absorbing using a desiccant that absorbs moisture. For example, the drying unit includes parallel desiccant beds, one of which is used for drying and the other for regeneration. During regeneration, hot dry gas is passed through the water-saturated desiccant bed, causing the adsorbed water to desorb and be removed with the gas. A specific embodiment of the drying unit is a temperature swing adsorption unit (TSA).

[0026] As used herein, the term "low-temperature CO2 removal section" is well known in the art and refers to the section for cooling a gas stream (here, a dried and compressed CO2-rich waste gas stream) to sub-zero temperatures to condense and separate CO2. A specific embodiment of the low-temperature CO2 removal section is a cryogenic separation unit. The cryogenic separation unit operates at extremely low temperatures, such as -50 to -80 °C, and high pressures, such as 20 to 70 bar. The extremely low temperature can condense CO2 from the gas stream, and the high pressure can keep CO2 in the condensed phase.

[0027] Other embodiments (non-cryogenic) of the low-temperature CO2 removal section include:

[0028] - A physical absorption unit, where CO2 is removed from the gas stream by dissolving it in a physical solvent, and in this unit, the solvent is regenerated by reducing the pressure and / or raising the temperature to release the absorbed CO2. Physical solvents include refrigerated methanol (Rectisol process) and refrigerated propylene carbonate (Selexol process);

[0029] - An adsorption unit, in which CO2 is removed by adsorbing CO2 onto the surface of an adsorbent solid material selected from any one of zeolite, activated carbon, and amino-functionalized materials. Then, the adsorbent solid material is regenerated by reducing the pressure and / or increasing the temperature, thereby releasing the adsorbed CO2. The adsorption unit is, for example, a temperature swing adsorption (TSA) unit or a pressure swing adsorption (PSA) unit, which can operate at a lower temperature but is not considered cryogenic.

[0030] For example, the low-temperature CO2 removal section is an amine scrubbing unit, or a CO2 membrane, i.e., a CO2 membrane separation unit, CO2-PSA, or cryogenic separation unit. In particular, when using a CO2 membrane separation unit, the permeate is a hydrogen-rich gas stream, which can then be transferred 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 reforming unit, or the feed side of the shift section, or the feed side of the membrane separation, i.e., the inlet side.

[0031] Other definitions will be provided in one or more of the following embodiments.

[0032] In one embodiment, the steam header is a low-pressure (LP) steam header or a high-pressure (HP) saturated steam header.

[0033] During the conversion of shift syngas to hydrogen, water in the shift syngas is typically removed as process condensate in a process condensate separator (PC separator) before the hydrogen purification step in the hydrogen purification unit.

[0034] In one embodiment, the apparatus further includes a low-pressure boiler (LP boiler) for generating steam by cooling at least any one of the synthesis gas stream (3) and the shift synthesis gas stream (5).

[0035] As is well known in the art, an LP boiler is a heat exchange unit, also known as a waste heat boiler (WHB), which operates at low pressure (i.e., approximately atmospheric pressure), and boiler feed water (BFW) is heated to below about 120 °C.

[0036] The present invention enables the shift synthesis gas to be cooled upstream of the PC separator:

[0037] - First, in one or more preheaters configured as boilers, i.e., LP boilers, using boiler feed water (BFW) from an external source, thereby generating steam (LP steam), which is supplied to the LP header;

[0038] - Secondly, in the air cooler, which is usually also referred to as the process gas air cooler, further downstream is a water cooler. The heat load and size of the process gas air cooler are significantly reduced. A high load (measured, for example, in Gcal / h) means high energy consumption and thus also high operating costs (OPEX). Therefore, the present invention can also reduce the size of the process gas air cooler, thereby reducing the floor area and lowering the capital expenditure (CAPEX).

[0039] In a hydrogen production plant, an LP boiler is not usually provided for cooling the shift syngas or any other process step. The present invention encompasses the provision of such an LP boiler as a new embodiment for generating LP steam for the drying unit. The LP boiler is suitably arranged upstream or downstream of the shift section, for example, immediately upstream of the air cooler.

[0040] The term "steam generated by cooling at least any one of the synthesis gas stream and the shift synthesis gas stream" means that the steam can also be generated at other locations in the plant / process. Thus, according to the present invention, LP steam can be generated in a hydrogen production plant and an LP steam header can be provided therefrom from which LP steam can be withdrawn. In the case of insufficient LP steam, steam from the HP saturated steam header, which is also provided in the plant / process, is used.

[0041] The steam header, i.e., the LP steam header or the HP saturated steam header, serves as a storage tank for supplying steam to the respective heating units (specifically, the heat exchange unit of the drying unit). It can be understood that sometimes an LP steam header is provided in the plant and LP steam can be obtained therefrom. If the LP steam is insufficient, HP steam from the steam drum (HP saturated steam header) is supplied to the LP steam header, thereby reducing the overall steam output of the plant. However, in some cases, the plant is not equipped with an LP steam header. Then, alternatively, LP steam can also be collected from the blow-down drum of the waste heat boiler (boiler), but the flow rate may be insufficient. Therefore, the LP steam in the LP header is optionally collected, for example, from a so-called condensate drum (also referred to as a blow-down drum herein), which is also arranged in the plant / process. A dedicated LP steam boiler (as described in the foregoing embodiment) can also be arranged at a certain position in the synthesis gas cooling pipeline (i.e., the upstream air cooler) to generate LP steam; for example, from the process gas waste heat boiler to the upstream air cooler.

[0042] Subsequently, the steam condensate generated in the heat exchange unit of the drying unit can be returned to the deaerator or the water purification unit of the plant / process.

[0043] Accordingly, a preferred embodiment of the present invention is to use the "hot" syngas from the upstream air cooler - since the heat will be wasted in the air cooler anyway. Another preferred embodiment is to use steam - first LP steam, and second HP saturated steam. Using steam is only valuable when the steam value is low or zero. The device / process enables flexible selection of the heat exchange medium in the heat exchange unit of the drying unit.

[0044] The integration provided by the present invention can, for example, reduce energy consumption and reduce the size of the process gas air cooler (i.e., the shift syngas air cooler), because, for example, a large part of the cooling of the shift syngas stream is actually carried out in the heat exchange unit that preheats the regeneration gas feed stream of the drying unit.

[0045] In one embodiment, the reforming unit is also arranged to extract a flue gas stream; and the low-pressure (LP) steam header or the high-pressure (HP) saturated steam header is arranged to receive the steam generated by cooling the flue gas stream.

[0046] For example, the flue gas is generated in a steam methane reformer (SMR) that is the reforming unit. For example, the flue gas is generated in a flame heater for preheating the hydrocarbon feed connected to the reforming unit (such as a flame heater connected to an autothermal reformer (ATR) that is the reforming unit).

[0047] In one embodiment, the heat exchange unit of the drying unit (190) is arranged to preheat the regeneration gas feed stream (19) by indirectly cooling the flue gas as the heat exchange medium.

[0048] This provides further integration, especially thermal integration, because heat is also recovered from the flue gas to generate steam, and is subsequently advantageously used in the heat exchange unit of the drying unit.

[0049] A hot drying gas stream is required to regenerate the water-saturated regeneration bed of the drying unit, which is suitably a temperature swing adsorption (TSA) unit. To generate the hot gas stream, the heat exchange unit (heater) is arranged, and steam, syngas or flue gas from the device / process is used to heat the drying stream, i.e., the regeneration gas feed stream. In addition, the drying gas stream or the hot drying gas stream of the device can also be used to regenerate the bed of the drying unit, which is obvious in one or more of the following embodiments.

[0050] In one embodiment, the low-temperature CO2 removal section (180) also provides a CO2 recycle stream (21); and the apparatus is also arranged to feed at least a portion of the CO2 recycle stream (21) to a location upstream of the CO2-rich flue gas recycle compressor (185) and downstream of the hydrogen purification unit (125); or to combine at least a portion of the CO2 recycle stream (21) with the shift synthesis gas stream (5) upstream of the hydrogen purification unit (125).

[0051] This enables further integration because the CO2 recycle stream can be used not only for the small amount of CO2-rich waste gas stream downstream of the hydrogen purification unit, but also for the main shift synthesis gas upstream of the hydrogen purification equipment.

[0052] The CO2 recycle stream (21) contains components that have not been removed from the CO2 product stream (11) and the CO2-depleted waste gas streams (17, 17', 17"). For example, the CO2 recycle stream (21) may still contain some CO2 and H2 that have not been extracted from the CO2 product stream and the CO2-depleted waste gas streams.

[0053] The CO2 product stream is a stream containing 95 vol% or more (e.g., 99.5 vol%) of carbon dioxide.

[0054] The CO2-depleted waste gas stream is rich in hydrogen, for example containing at least 50% H2 (vol% or mol%), and can thus be advantageously utilized in the apparatus and process. The CO2-depleted waste gas stream contains, for example: 85 mol% H2, 7 mol% CH4, 7 mol% CO, and 1 mol% N2+Ar. Thus, the CO2-depleted waste gas stream is rich in hydrogen and substantially free of carbon dioxide.

[0055] In one embodiment, the apparatus (100) is also arranged to recycle the CO2-depleted waste gas stream or a portion thereof (17, 17', 17") to the feed side of at least the reforming unit (110).

[0056] Thus, at least a portion of the compressed CO2-depleted waste gas stream is utilized in the process by becoming part of the hydrocarbon feed or process gas, for example being processed in a prereformer, or a reforming unit (such as an ATR) or a shift section. Thus, with the same hydrogen production, at least the consumption of hydrocarbon feed (such as natural gas) can be reduced while increasing the CO2 capture amount, and thus reducing CO2 emissions.

[0057] The term "at least sent to the feed side of the reforming unit" means that the CO2-depleted waste gas stream or a portion thereof (17, 17', 17") can also be recycled to the feed side of other units, such as a prereformer, or used as fuel for a fired heater, or recycled to the shift section, which will become apparent in one or more of the following embodiments.

[0058] Thus, in one embodiment, the apparatus (100) further comprises at least one fired heater arranged to preheat the hydrocarbon feed (1, 2) before it is supplied to the reforming unit (110), and the apparatus (100) is arranged to supply at least a portion of the CO2-rich waste gas stream (9) from the hydrogen purification unit (125), or at least a portion of the CO2-depleted waste gas stream (17, 17', 17") as a fuel feed to the fired heater.

[0059] Since a portion of the CO2-depleted waste gas is also used as fuel for the fired heater, the flue gas generated by the fired heater, and thus the carbon emissions of the entire apparatus / process, are lower. It will be understood that flue gas is typically generated by the combustion in the fired heater. Separate fuel gas and / or hydrogen fuel gas and combustion air are suitably used in the fired heater. The consumption of fuel gas (such as natural gas) typically used for combustion is significantly reduced or eliminated. In addition to preheating the hydrocarbon feed gas entering the prereformer and reforming unit, the fired heater can also be used, for example, to superheat steam.

[0060] In one embodiment, the apparatus (100) further comprises at least one prereformer unit (140) arranged upstream of the reforming unit (110), the prereformer unit (140) being arranged to prereform the hydrocarbon feed (1) before it is supplied to the reforming unit (110).

[0061] As used herein, the terms prereformer, prereformer unit, and prereforming unit are used interchangeably.

[0062] In one embodiment, the prereformer unit is an adiabatic prereformer unit.

[0063] By providing a single prereformer unit (such as an adiabatic prereformer unit), the apparatus and process can be simplified. There is no need to additionally arrange a prereformer and its associated heat exchange units, thus saving related capital and operating costs.

[0064] In the pre-reforming unit, all higher hydrocarbons can be converted to carbon oxides and methane, but the pre-reforming unit is also beneficial for light hydrocarbons. Arranging the pre-reforming unit, and thus the reforming step, can have many advantages, including reducing the oxygen consumption required by the downstream autothermal reformer (ATR) and allowing a higher inlet temperature for the ATR, since the cracking risk due to preheating is minimized. In addition, the pre-reforming unit can provide efficient sulfur protection, making the feed gas entering the ATR and the downstream system almost sulfur-free. The pre-reforming step can be carried out at a temperature of 300 to 650 °C, for example 390 - 480 °C.

[0065] In one embodiment, the reforming unit is an autothermal reformer (ATR); a partial oxidation reformer (PO x ) ; a convective heating reformer, such as a heat exchange 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.

[0066] All of the above reforming units are well known in the art.

[0067] For example:

[0068] - In an autothermal reformer (ATR), the hydrocarbon feed undergoes partial oxidation with oxygen and steam and then catalytic reforming; in autothermal reforming (ATR), the term catalytic partial oxidation (CPO) is also included herein, where natural gas or other hydrocarbons react with steam and an oxidant (air, oxygen-enriched air or oxygen) in the presence of a nickel- or noble metal-based catalyst;

[0069] - In the non-catalytic partial oxidation (POX) (also known as gasification) of natural gas, light hydrocarbons, heavy hydrocarbons or solid feedstocks such as coal, it reacts with an oxidant (air, oxygen-enriched air or oxygen), and the outlet temperature of the reactor can be as high as 1400 °C;

[0070] - A convective heating reformer may contain one or more bayonet reforming tubes, such as an HTCR reformer, i.e., a Topsøe bayonet reformer, where the heat for reforming is transferred by convection and radiation;

[0071] - The term SMR encompasses traditional SMR and e-SMR; in traditional SMR (also known as tubular reformer), the heat required for reforming is mainly transferred by radiation in a radiant furnace; in an electrically heated steam methane reformer (e-SMR), electrical resistance is used to generate the heat required for catalytic reforming. Specifically, when using e-SMR, electricity from green energy sources such as wind, water, and solar power can be utilized, thereby further reducing the CO2 footprint.

[0072] For more information on these reformers, detailed descriptions are provided in this article by directly citing the applicant's patents and / or literature. For example, regarding tubular reforming and autothermal reforming, an overview has been given in "Tubular reforming and autothermal reforming of natural gas – an overview of available processes", Ib Fuel Processing Technology 42 (1995) 85 - 107; for the description of HTCR, see EP0535505; for the description of HER, see, for example, EP 2526045; for the process description of the combination of ATR and HER, see, for example, EP 0983963. For the description of ATR and / or SMR (tubular reformer) for large-scale hydrogen production, please refer to, for example, the article: "Large-scale Hydrogen Production", Jens R. Rostrup-Nielsen and Thomas Rostrup-Nielsen", CATTECH, volume 6, pages 150–159 (2002). For the description of the relatively new technology e-SMR, please refer to, for example, WO 2019 / 228797 A1.

[0073] 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., 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 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, noble metals on an Al2O3 support, but other catalysts suitable for reforming may also be used. The catalytically active material may be Ni, Ru, Rh, Ir or a combination thereof, and the ceramic coating may be Al2O3, ZrO2, MgAl2O3, CaAl2O3 or a combination thereof, and may be mixed with oxides of Y, Ti, La or Ce. The maximum temperature of the reactor can be between 850 - 1300 °C. The pressure of the feed gas can be 15 - 180 bar, preferably about 25 bar. The steam reforming catalyst is also known as the steam methane reforming catalyst or the methane reforming catalyst.

[0074] In a specific embodiment, the reforming unit is an autothermal reformer (ATR). The ATR is capable of operating the device / process at a lower steam / carbon ratio, thereby significantly reducing the size of the device. For example, the steam / carbon ratio of the syngas fed from the ATR to the shift section is less than 2.0, preferably 0.3 - 1.0.

[0075] Also suitably, the device (100) is arranged to feed at least a portion of the CO2-depleted waste gas stream (17, 17') to the feed side of the prereforming unit (140); and / or

[0076] - The device (100) is arranged to feed at least a portion of the CO2-depleted waste gas stream (17) to the feed side of the shift section; and / or

[0077] The device is arranged to feed at least a portion of the CO2-depleted waste gas stream to the feed side of the hydrogen purification unit (125).

[0078] As used herein, the term "feed side" refers to the inlet side or simply the inlet. For example, the feed side of the reforming unit (such as the ATR) refers to the inlet side of the ATR. For example, the feed side of the shift section refers to the inlet side of the high-temperature or medium-temperature shift unit, or the inlet side of any downstream shift unit downstream of the shift section, such as a medium-temperature shift unit arranged downstream of the high-temperature shift unit.

[0079] The CO2-depleted offgas is recycled to the ATR etc., and the advantage is that the flow rate to the prereformer can be reduced, thereby reducing its size. More specifically, recycling the CO2-depleted offgas can increase the hydrogen recovery rate, thereby reducing the feed consumption. Therefore, the size of the upstream equipment can also be reduced.

[0080] The advantage of recycling the CO2-depleted offgas stream to the shift section is that the sizes of the ATR and the prereformer can be reduced.

[0081] Suitably, there is no (i.e., there does not exist) a steam methane reforming unit (SMR) upstream of the ATR in this equipment. Therefore, the reforming section, i.e., the reforming unit, includes the ATR, and optionally includes a prereforming unit, but does not have a steam methane reforming (SMR) unit, that is, the use of, for example, a conventional SMR (usually also called a radiant furnace or a tubular reformer) is omitted. Therefore, in one embodiment, the reforming unit is the ATR, and a prereforming unit is arranged upstream thereof. The combination of the ATR and the prereforming unit (i.e., a stand-alone ATR) is a simple and energy-saving solution for the reforming section.

[0082] This has significant advantages in terms of energy consumption and equipment scale, because now, among other things, it is possible to operate at a steam / carbon molar ratio far lower than 1, thereby significantly reducing the amount of steam carried in the equipment / process, as also described above.

[0083] Suitably, the equipment further includes a hydrogenation unit and a sulfur absorption unit arranged upstream of the at least one prereforming unit, wherein the equipment is arranged to supply at least a part of the CO2-depleted offgas stream to the feed side of the hydrogenation unit.

[0084] Suitably, the shift section includes a high-temperature or medium-temperature shift unit. For example, the shift section includes one or more additional shift units downstream of the high-temperature shift (HTS) unit. In a specific embodiment, the one or more additional shift units are one or more medium-temperature shift (MTS) units and / or one or more low-temperature shift (LTS) units.

[0085] When operating at a low steam / carbon ratio, providing additional shift units or shift steps can improve the flexibility of the equipment and / or the process. A low steam / carbon ratio may result in a shift conversion rate lower than the optimum value, which means that in some embodiments, providing one or more additional shift steps may be advantageous. One or more additional shift steps may include medium-temperature (MT) shift and / or low-temperature (LT) shift and / or high-temperature shift. Generally speaking, the more CO is converted in the shift step, the more H2 is obtained and the less front end is required.

[0086] Steam can be optionally 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 the performance of the subsequent HT, MT and / or LT shift steps.

[0087] It may be advantageous to employ 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., cooling and / or steam addition may be effected between the shift reactors), since the shift conversion can be increased at high temperature, which may reduce the amount of shift catalyst required and thus may reduce the capital expenditure. Additionally, high temperature can also reduce the formation of methanol, a typical by-product of the shift step.

[0088] In one embodiment, the reforming unit (110) comprises an autothermal reformer (ATR), and the apparatus (100) further comprises an air separation unit (ASU) (145) which is arranged to receive an air stream (14) and produce a N2-rich stream (19) and an O2-rich stream (15); and the regeneration gas feed stream (19) is at least a portion of the N2-rich stream.

[0089] Further integration is thus achieved. The ASU is typically used in conjunction with the ATR since the ATR utilizes the O2-rich stream produced in the ASU. Thus, the N2-rich stream produced in the ASU can now be advantageously used as the regeneration gas for the drying unit.

[0090] In one embodiment, the regeneration gas feed stream (19) is selected from:

[0091] - at least a portion of any of the following streams: the CO2 product stream (11), the CO2-depleted waste gas stream (17, 17', 17''), the CO2 recycle stream (21), and the dried and compressed CO2-rich waste gas stream (9'');

[0092] - at least a portion of the hydrogen product (8).

[0093] Typically, air is used as the regeneration gas in a drying unit (e.g., a temperature swing adsorption (TSA) unit). The present invention provides a solution that is superior to air as the regeneration gas. It has been found that air has drawbacks as it mixes oxygen with hydrocarbons and does not have a synergistic effect with the hydrogen production equipment / process. In contrast, by using, for example, the CO2 product stream (11), the CO2-depleted waste gas stream (17, 17', 17''), the CO2 recycle stream (21), the dried and compressed CO2-rich waste gas stream (9''), or the hydrogen product (8), not only are the drawbacks associated with the mixing of oxygen and hydrocarbons (e.g., CH4) eliminated, but also a synergistic integration with the equipment / process is provided as these resulting gas streams can further function as the regeneration gas.

[0094] The regeneration gas is typically a cold and dry gas. It needs to be heated with hot syngas or steam to dry the used bed. Hot gases are more capable of absorbing moisture than cold gases. Subsequently, the humid hot gas is cooled to condense the moisture, and the cooled gas is recycled to the heat exchange unit of the drying unit.

[0095] Thus, in one embodiment, the apparatus further comprises:

[0096] - a cooler arranged to receive the regeneration gas outlet stream (19') to condense its moisture and provide a dried regeneration gas outlet stream;

[0097] - a recycle regeneration gas compressor arranged to receive the regeneration gas outlet stream (19') or the dried regeneration gas outlet stream and compress it into a compressed regeneration gas outlet stream or a compressed and dried regeneration gas outlet stream and recycle it to:

[0098] the inlet of the drying unit (190), for example, by combining with the regeneration gas feed (19); or

[0099] the inlet of the hydrogen purification unit (125), for example, the inlet of the PSA unit; or

[0100] the inlet of the CO2-rich waste gas recycle compressor (185).

[0101] The regeneration gas outlet stream is a wet gas stream. Thus, this stream is cooled to condense the moisture, and the cooled gas (with the moisture removed at this time) is recompressed and recycled back to the equipment / process. For example, when hydrogen is used as the regeneration gas, it is recycled back to the inlet of the hydrogen purification unit (preferably the PSA unit) after water removal; or, when CO2 is used, it is recycled back to the CO2-rich waste gas recycle compressor; or, the dried outlet regeneration gas is recycled back into the drying unit inlet.

[0102] In one embodiment, the cryogenic CO2 removal section (180) is a cryogenic separation unit including a cryogenic compressor; the apparatus further includes a superheated steam header and a steam turbine for powering the cryogenic compressor, and the steam turbine is arranged to receive a portion of the steam from the superheated steam header to provide the power.

[0103] It should be understood that the term "cryogenic compressor" means "one or more cryogenic compressors".

[0104] Thereby, further integration is achieved. Generally, the surplus heat load is output in the form of low-value or worthless steam, that is, the output steam is usually of low value or worthless, and thus is an undesirable by-product in the hydrogen production apparatus / process. Utilizing this steam (superheated steam) to provide the required power for the compressor in the cryogenic CO2 removal section saves the power cost and reduces the associated operating expenses of the apparatus / process.

[0105] In one embodiment, the drying unit (190) is a temperature swing adsorption (TSA) unit, suitably a single TSA unit including two adsorption beds; and / or the hydrogen purification unit (125) is a pressure swing adsorption (PSA) unit, suitably a single PSA unit.

[0106] Both TSA and PSA are well-known techniques in the art. In TSA, the adsorbent is regenerated by heating. In PSA, the adsorbent is regenerated by reducing the pressure.

[0107] In the present application, the heat used in TSA is provided by the above heat exchange unit (heater), which utilizes the steam, syngas or flue gas generated in the apparatus / process to preheat the regeneration gas, thereby achieving a high degree of integration of the apparatus / process.

[0108] In one embodiment, the apparatus is arranged to directly recycle the CO2-depleted waste gas stream (17, 17', 17”) or a portion thereof to at least the feed side of the reforming unit (110), that is, a pipeline is provided for directly recycling the CO2-depleted waste gas stream or a portion thereof (17, 17', 17”) to at least the feed side of the reforming unit (110).

[0109] Therefore, the apparatus (100) suitably does not have a second hydrogen purification unit, such as a second PSA unit, located downstream of the CO2 removal section (180).

[0110] In one embodiment, the apparatus (100) is arranged to feed the reformed synthesis gas stream (5) directly into the hydrogen purification unit (125). Accordingly, a CO2 removal unit, which is typically arranged downstream of the hydrogen purification unit and is used to remove CO2 from the main process gas stream (i.e., the reformed synthesis gas stream), is omitted. Thus, CO2 removal is only carried out in the small amount of CO2-rich exhaust gas discharged from the hydrogen purification unit.

[0111] As used herein, the term "directly" means that there are no intermediate steps or units that change the stream composition. For example, as shown in the drawings, the apparatus 100 is arranged to directly recycle the CO2-depleted exhaust gas stream or a portion thereof (17, 17', 17") to at least the feed side of the reforming unit 110. Also as shown in the drawings, the apparatus (100) is arranged to feed the reformed synthesis gas stream (5) directly into the hydrogen purification unit (125).

[0112] It should be understood that the CO2-depleted exhaust gas stream or a portion thereof (17, 17', 17") can also be directly recycled to the feed side of other units, such as the pre-reformer (140), or used as fuel for a fired heater, or recycled to the reforming section (115, 150).

[0113] Thereby, a simpler apparatus / process is provided because the number of steps or units required in the apparatus / process is reduced.

[0114] In addition, the reformed synthesis gas is typically supplied to a CO2 removal unit upstream of the hydrogen purification unit. This CO2 removal unit is also typically an amine scrubbing unit and thus is also provided with a CO2 reboiler that utilizes the heat (heat load) of the produced synthesis gas (e.g., reformed synthesis gas). Since the CO2 removal unit is omitted upstream of the hydrogen purification unit, the present invention also has the advantage of not requiring a CO2 reboiler. Without a CO2 reboiler, there can be more heat load in the apparatus / process for preheating purposes. As described above, the regeneration gas is preheated indirectly, for example, using LP steam generated by a boiler provided for cooling the synthesis gas or any other hot gas stream in the apparatus / process.

[0115] In a second aspect of the present invention, there is also provided a method for producing a hydrogen product (8) from a hydrocarbon feed (1, 2), the method comprising the following steps:

[0116] - providing an apparatus (100) according to any of the preceding embodiments;

[0117] - feeding a hydrocarbon feed (2) to a reforming unit (110) and converting it into a synthesis gas stream (3);

[0118] - Supply the syngas stream (3) from the reforming unit (110) to the shift section (115, 150) and subject it to a shift in a shift step, which is suitably a high temperature or medium temperature shift step (115), to provide a shifted syngas stream (5);

[0119] - Feed the shifted gas stream (5) from the shift section to a hydrogen purification unit (125) and separate it into a high purity H2 stream as the hydrogen product (8) and a CO2-rich waste gas stream (9);

[0120] The method further includes:

[0121] - Compress the CO2-rich waste gas stream (9) into a compressed CO2-rich waste gas stream (9');

[0122] - Dry the compressed CO2-rich waste gas stream (9') in a drying unit (190) with the addition of a regeneration gas feed stream (19) to provide a dried and compressed CO2-rich waste gas stream (9”) and a regeneration gas product stream (19');

[0123] - Preheat the regeneration gas feed stream (19) by indirectly cooling a heat exchange medium selected from any one of: steam (13”) from a steam header, such as steam from an LP steam header or steam from an HP saturated steam header; the syngas stream (3); the shifted syngas stream (5); optionally the flue gas stream generated in the reforming unit (110); and combinations thereof; to provide a cooled heat exchange medium, namely steam condensate (13”'), cooled syngas, or optionally cooled flue gas stream;

[0124] - Feed the dried and compressed CO2-rich waste gas stream (9”) to a CO2 removal step in a low temperature CO2 removal section (180) to provide a CO2 product stream (11), a CO2-depleted waste gas stream (17, 17', 17”), and an optional CO2 recycle stream (21).

[0125] It should be understood that any embodiment and related benefits of the first aspect (apparatus) of the present invention can be used in combination with the second aspect (method) of the present invention, and vice versa. Brief Description of the Drawings

[0127] The sole drawing (Figure) shows the layout of an ATR-based hydrogen production process and apparatus according to an embodiment of the present invention. Detailed Description

[0129] The attached drawing (figure) shows a hydrogen production device 100, in which a hydrocarbon feed 1 (i.e., the main hydrocarbon feed 1, such as natural gas) is transported to a reforming section, which includes a pre-reforming unit 140 and a reforming unit 110 (illustrated here as an autothermal reformer). The reforming section may also include a hydrogenator and a sulfur absorber unit (not shown in the figure) located upstream of the pre-reforming unit 140. The hydrocarbon stream 1 is mixed with steam 13. The resulting hydrocarbon feed 2 is transported to the ATR 110, and the oxygen-rich stream 15 and steam 13 are also transported to the ATR 110. The oxygen-rich stream 15 is generated by an air separation unit (ASU) 145, and air 14 is transported to the ASU. The ASU 145 also generates a nitrogen-rich stream 19, which, in this embodiment of the present invention, is used as the regeneration gas feed stream for the drying unit 190 of the device 100. In the ATR 110, the hydrocarbon feed 2 is converted into a synthesis gas stream 3, which is then transported to the shift section 115, 150. The shift section includes, for example, a high-temperature shift (HTS) unit 115, and additional or supplementary steam 13' may also be added upstream. The shift section may also include additional shift units, such as a low-temperature shift (LTS) unit 150. It should be understood that the shift section may include any one of, or a combination of, HTS, MTS, and LTS. Additional or supplementary steam 13' may also be added downstream of the HTS unit 115 but upstream of the low-temperature shift unit 150. Then, the shifted gas stream 5 is fed from the shift section into (e.g., directly fed as shown here) a hydrogen purification unit 125 (e.g., a PSA unit), from which a high-purity H2 stream is generated as the hydrogen product 8, and a waste gas stream 9 rich in CO2 is produced.

[0130] A CO2-rich waste gas recycle compressor 185 is arranged to receive the CO2-rich waste gas stream 9 and compress it into a compressed CO2-rich waste gas stream 9'. A drying unit 190 (e.g., a TSA unit) is arranged downstream to receive the compressed CO2-rich waste gas stream 9' and provide a dried and compressed CO2-rich waste gas stream 9”. The drying unit 190 is also arranged to receive a regeneration gas feed stream 19 (shown here as a nitrogen-rich stream 19) and extract a regeneration gas discharge stream 19'. The regeneration gas feed stream 19 may also be at least a part of the CO2 product stream 11, or at least a part of the CO2-depleted waste gas streams 17, 17', 17”, or an optional part of the CO2 recycle stream 21; or at least a part of the hydrogen product 8.

[0131] A heat exchange unit (heater, not shown in the figure) is arranged in the drying unit 190 to preheat the regenerated gas feed stream 19 by indirectly cooling the heat exchange medium, and the heat exchange medium shown here is steam 13” (not shown in the figure) from a steam header (for example, the low-pressure (LP) steam header or the HP saturated steam header of the device 100). The cooled heat exchange medium is generated and extracted as steam condensate 13”. The low-temperature CO2 removal section 180 (for example, a cryogenic unit) is arranged to receive the dried and compressed CO2-rich waste gas stream 9” to remove CO2, thereby providing: a CO2 product stream 11, a CO2-depleted waste gas stream 17, 17', 17” and a CO2 recycle stream 21.

[0132] The device 100 is also arranged to recycle (for example, directly recycle) the CO2-depleted waste gas stream or a part thereof 17, 17', 17” to the feed side of the prereformer 140, the feed side of the reforming unit (here the ATR 110) or the shift section (not shown). The device 100 may also include at least one flame heater (not shown), which is arranged to preheat the hydrocarbon feeds 1, 2 before they are fed to the reforming unit 110. Thus, the CO2-depleted waste gas streams 17, 17', 17” can be used as fuel for the flame heater.

Claims

1. An apparatus (100) for producing a hydrogen product (8) from a hydrocarbon feed (1), the apparatus comprising: - A reforming unit (110) arranged to receive a hydrocarbon feed (1, 2) and convert it into a synthesis gas stream (3); - A shift section (115, 150) arranged to receive the synthesis gas stream (3) from the steam reforming unit (110) and shift it into 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 H2 stream as the hydrogen product (8) and a CO2-rich waste gas stream (9); - A steam header arranged to receive steam generated by cooling at least any one of the synthesis gas stream (3) and the shifted synthesis gas stream (5); - A CO2-rich waste gas recycle compressor (185) arranged to receive the CO2-rich waste gas stream (9) and compress it into a compressed CO2-rich waste gas stream (9'); - A drying unit (190) arranged to receive the compressed CO2-rich waste gas stream (9') and provide a dried and compressed CO2-rich waste gas stream (9"); the drying unit (190) is also arranged to receive a regeneration gas feed stream (19) and extract a regeneration gas discharge stream (19'); the drying unit (190) also includes: a heat exchange unit arranged to preheat the regeneration gas feed stream (19) by indirectly cooling a heat exchange medium selected from any one of the following: steam (13") from the steam header, the synthesis gas stream (3), the shifted synthesis gas stream (5), and combinations thereof; and provide a cooled heat exchange medium, i.e., steam condensate (13"') or cooled syngas, such as the cooled synthesis gas stream (3) or the cooled shifted synthesis gas stream (5); - A cryogenic CO2 removal section (180) arranged to receive the dried and compressed CO2-rich waste gas stream (9") to remove CO2 from the CO2-rich waste gas stream (9) or from the dried and compressed CO2-rich waste gas stream (9") and at least provide: a CO2 product stream (11) and a CO2-depleted waste gas stream (17, 17', 17"); 2. The apparatus according to claim 1, wherein the steam header is a low-pressure (LP) steam header or a high-pressure (HP) saturated steam header.

3. The apparatus according to claim 2, wherein the reforming unit is further arranged to extract a flue gas stream; and wherein the low-pressure (LP) steam header or the high-pressure (HP) saturated steam header is arranged to receive steam generated by cooling the flue gas stream.

4. The apparatus according to claim 3, wherein the heat exchange unit of the drying unit (190) is arranged to preheat the regenerated gas feed stream (19) by indirectly cooling the flue gas as the heat exchange medium.

5. The apparatus according to any one of claims 1-4, wherein the low-temperature CO2 removal section (180) further provides a CO2 recycle stream (21); and the apparatus is further arranged to feed at least a portion of the CO2 recycle stream (21) to a location upstream of the CO2-rich offgas recycle compressor (185) and downstream of the hydrogen purification unit (125); or to combine at least a portion of the CO2 recycle stream (21) with the shift synthesis gas stream (5) upstream of the hydrogen purification unit (125).

6. The apparatus according to any one of claims 1-5, wherein the apparatus (100) is further arranged to recycle the CO2-depleted offgas stream or a portion thereof (17, 17', 17”) to at least the feed side of the reforming unit (110).

7. The apparatus according to any one of claims 1-6, further comprising at least one fired heater arranged to preheat the hydrocarbon feed (1, 2) before it is supplied to the reforming unit (110), and wherein the apparatus (100) is arranged to feed at least a portion of the CO2-rich offgas stream (9) from the hydrogen purification unit (125), or at least a portion of the CO2-depleted offgas stream (17, 17', 17”) as fuel to the fired heater.

8. The apparatus according to any one of claims 1-7, wherein - The device (100) further includes at least one prereforming unit (140) arranged upstream of the reforming unit (110), and the prereforming unit (140) is arranged to prereform the hydrocarbon feed (1) before it is supplied to the reforming unit (110).

9. The device according to any one of claims 1-8, wherein the reforming unit (110) includes an autothermal reformer (ATR), and the device (100) further includes an air separation unit (ASU) (145), the air separation unit being arranged to receive an air stream (14) and generate a nitrogen-rich stream (19) and an oxygen-rich stream (15); and the regenerating gas feed stream (19) is at least a part of the nitrogen-rich stream.

10. The device according to any one of claims 1-9, wherein the regenerating gas feed stream (19) is selected from: - At least a part of any one of the following streams: a CO2 product stream (11), a CO2-depleted waste gas stream (17, 17', 17''), a CO2 recycle stream (21), and a dried and compressed CO2-rich waste gas stream (9''); - At least a part of the hydrogen product (8).

11. The device according to any one of claims 1-10, wherein the device (100) further includes: - A cooler arranged to receive the regeneration gas discharge stream (19') to condense its moisture and provide a dried regeneration gas discharge stream; - A recycle regeneration gas compressor arranged to receive the regeneration gas discharge stream (19') or the dried regeneration gas discharge stream and compress it into a compressed regeneration gas discharge stream or a compressed and dried regeneration gas discharge stream and recycle it to: The inlet of the drying unit (190); or The inlet of the hydrogen purification unit (125); or The inlet of the CO2-rich waste gas recycle compressor (185).

12. The device according to any one of claims 1-11, wherein the low-temperature CO2 removal section (180) is a cryogenic separation unit including a cryogenic compressor; the device further includes a superheated steam header and a steam turbine for supplying power to the cryogenic compressor, and the steam turbine is arranged to receive a part of the steam from the superheated steam header to supply the power.

13. The device according to any one of claims 1-12, wherein the drying unit (190) is a temperature swing adsorption (TSA) unit; and / or the hydrogen purification unit (125) is a pressure swing adsorption (PSA) unit.

14. The device according to any one of claims 6-13, wherein the device (100) is arranged to directly recycle the CO2-depleted waste gas stream (17, 17', 17'') or a part thereof to at least the feed side of the reforming unit (110).

15. The apparatus according to any one of claims 1 - 14, wherein the apparatus (100) is arranged to feed the transformed synthesis gas stream (5) directly to the hydrogen purification unit (125).

16. A method for producing a hydrogen product (8) from a hydrocarbon feed (1, 2), the method comprising the steps of: - Provide the device (100) according to any one of the preceding claims; - Supply the hydrocarbon feed (2) to the reforming unit (110) and convert it into a synthesis gas stream (3); - Supply the syngas stream (3) from the reforming unit (110) to the shift section (115, 150) and subject it to a shift in a shift step, which is suitably a high-temperature or medium-temperature shift step (115), to provide a shifted syngas stream (5); - Feed the shifted gas stream (5) from the shift section to a hydrogen purification unit (125) and separate it into a high-purity H2 stream as the hydrogen product (8) and a CO2-rich waste gas stream (9); The method further comprises: - Compress the CO2-rich waste gas stream (9) into a compressed CO2-rich waste gas stream (9'); - Dry the compressed CO2-rich waste gas stream (9') in a drying unit (190) in the presence of a regeneration gas feed stream (19) to provide a dried and compressed CO2-rich waste gas stream (9”) and a regeneration gas product stream (19'); - Preheat the regeneration gas feed stream (19) by indirectly cooling a heat transfer medium selected from any one of: steam (13”) from a steam header, such as steam from an LP steam header or steam from an HP saturated steam header; the syngas stream (3); the shifted syngas stream (5); optionally the flue gas stream generated in the reforming unit (110); and combinations thereof; to provide a cooled heat transfer medium, namely steam condensate (13”'), cooled syngas, or optionally a cooled flue gas stream; - Feed the dried and compressed CO2-rich waste gas stream (9”) to a CO2 removal step in a low-temperature CO2 removal section (180) to provide a CO2 product stream (11), a CO2-depleted waste gas stream (17, 17', 17”), and optionally a CO2 recycle stream (21).

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