Method and apparatus for producing syngas

Abstract

The present invention provides a process and apparatus for producing syngas and hydrogen products from a hydrocarbon feed with improved carbon capture, the process comprising the steps of: reforming the hydrocarbon feed by pre-reforming and autothermal reforming (ATR) to obtain syngas; converting the synthesis gas in a conversion section; wherein a portion of the shifted syngas is recycled to the process flow, suitably to the pre-reforming. There is no need to preheat the hydrocarbon feed or the pre-reformed hydrocarbon feed using a flame heater.

Description

[0001] The present invention relates to a method and apparatus for producing synthesis gas (syngas) from a hydrocarbon feed, and optionally further producing hydrogen. The method and apparatus include pre-reforming, autothermal reforming, water gas shift to produce synthesis gas, and optionally CO2 removal and hydrogen purification to produce hydrogen. An embodiment of the present invention includes recycling the shifted synthesis gas into the hydrocarbon feed stream before pre-reforming.

[0002] WO 2022038089 of the applicant discloses an apparatus and method for producing hydrogen-rich gas and having improved carbon capture, wherein the method comprises the following steps: reforming a hydrocarbon feed by optional pre-reforming, autothermal reforming (ATR) instead of primary reforming, thereby obtaining synthesis gas; shifting the synthesis gas in a shift section including a high temperature shift step; removing CO2 upstream of a hydrogen purification unit, thereby producing a hydrogen-rich stream and an exhaust gas stream, wherein at least a portion of the exhaust gas stream is recycled to the method, thereby recycling to the ATR and optional pre-reforming, and / or recycling to the shift section. The apparatus is arranged to provide an inlet temperature of the hydrocarbon feed to the ATR of less than 600°C, such as 550°C or 500°C or lower, such as 300-400°C. By reducing the ATR inlet temperature, suitably 550°C or lower, such as 500°C or lower, such as 300-400°C, the heat required by the heater unit (e.g., a fired heater) for preheating hydrocarbons is significantly reduced, so that a smaller fired heater can be used, or the number of fired heaters is reduced. The use of a heater can also be completely eliminated by setting the ATR inlet temperature to 300-400°C.

[0003] The above temperatures are lower than the typical ATR inlet temperature of 600-700°C, which is generally considered to be ideal for reducing oxygen consumption in the ATR. However, it is desirable to be able to operate the ATR at an inlet temperature lower than the typical 600-700°C, but not lower than 420°C, such as not lower than 450°C, so as to be able to better maintain a combustion flame in the ATR to drive the partial oxidation reaction therein.

[0004] It would also be desirable to provide an alternative method and apparatus for the production of syngas, optionally further converted to a hydrogen product, which is based on an ATR and does not require a dedicated fired heater typically used to preheat the hydrocarbon feed to the temperature required for desulfurization, including prior hydrogenation of the hydrocarbon feed, and to preheat the hydrocarbon feed prior to pre-reforming or autothermal reforming. Fired heaters are bulky and costly devices that require a considerable floor space and involve significant direct carbon emissions due to the flue gases generated by the combustion of the fuel, typically natural gas. Therefore, designing and operating a method and apparatus without a fired heater can significantly reduce capital and operating expenditures and can significantly reduce carbon emissions, thereby significantly reducing the carbon footprint of the method and apparatus.

[0005] It would also be desirable to be able to provide greater heat integration in a process or apparatus for producing synthesis gas and optionally hydrogen product.

[0006] The present invention proposes solutions to the above-mentioned and other problems.

[0007] Thus, in a first aspect, the present invention is a method for producing synthesis gas from a hydrocarbon feed comprising the steps of:

[0008] i) pre-reforming a hydrocarbon feed to produce a pre-reformed hydrocarbon feed;

[0009] ii) autothermal reforming of the pre-reformed hydrocarbon feed to produce a crude synthesis gas;

[0010] iii) subjecting the raw synthesis gas to a water gas shift reaction to produce a shifted synthesis gas as the synthesis gas; and

[0011] The first part of the shifted synthesis gas is recycled by combining it with the hydrocarbon feed of step i); wherein the first part of the shifted synthesis gas being recycled is the shifted synthesis gas from which water has been removed in the water separation step.

[0012] The term “comprising” as used herein also covers “comprising only”, ie “consisting of”.

[0013] As used herein, the term "suitably" is used interchangeably with the term "optionally" to refer to specific embodiments of the invention.

[0014] As used herein, the term "synthesis gas" is used interchangeably with the term "syngas." As is well known in the art, synthesis gas is a gas containing carbon oxides (CO and CO2) and H2.

[0015] As used herein, the term "first aspect of the present invention" refers to a method according to the present invention; the term "second aspect of the present invention" refers to an apparatus, ie a process apparatus, according to the present invention.

[0016] As used herein, the terms "present invention" or "invention" may be used interchangeably with the terms "this application" or "application," respectively.

[0017] As used herein, the first portion of the shifted syngas that is recycled is also referred to as "shifted syngas recycle".

[0018] It will be appreciated that said first portion of the shifted synthesis gas that is recycled, i.e. the shifted synthesis gas recycle, is the portion taken directly from the water separation step. Hence, the shifted synthesis gas recycle is fed directly to the hydrocarbon feed of step i). The term "directly fed" means that there are no intermediate steps or units that substantially change the composition of the stream.

[0019] The first part of the shifted synthesis gas which is recycled has not yet been subjected to CO 2 removal and subsequent hydrogen enrichment.

[0020] The second section optionally performs CO2 removal and / or hydrogen enrichment, as will become clear from the embodiments below, or as shown in the accompanying drawings.

[0021] Thus, according to the present invention, and in contrast to the prior art, there is no recirculation of the shifted synthesis gas after the acid gas removal (CO2 removal) and / or hydrogen purification steps. The latter means the recirculation of a purer hydrogen stream produced after CO2 removal and hydrogen purification, for example in a pressure swing adsorption (PSA) unit. In the present invention, the first part of the shifted synthesis gas refers to the gas that has been cooled and then treated to remove water (drying) before CO2 removal and / or hydrogen purification; it therefore contains a considerable amount of H2 and CO2 in order to provide exothermic heat by methanation in the pre-reforming, which avoids any heat input required to preheat the pre-reformed hydrocarbon feed before feeding it to the autothermal reforming. According to the prior art, this preheating is carried out by means of a fired heater or a gas heated reformer. The latter is conventionally also used as a primary reforming step, which is essentially an endothermic step requiring heat to prepare the synthesis gas for the subsequent autothermal reforming.

[0022] In the present invention, the portion of the shifted syngas being recycled has a large amount of H2 and CO2, for example more than 70 vol.% H2 and more than 25 vol.% CO2, which enables an exothermic methanation reaction to occur on the pre-reforming catalyst used in the pre-reforming, CO2 + 4H2 = CH4 + 2H2O. Typically, pre-reforming or reforming is highly endothermic, wherein methane in the hydrocarbon feed is converted to carbon oxides (CO, CO2) and hydrogen in the presence of steam. Thus, typically the hydrocarbon feed gas has an inlet temperature of about 450°C into the pre-reforming step and an outlet temperature of about 420°C. The methanation reaction is a reverse reaction and is therefore exothermic. The exotherm in the pre-reforming enables the pre-reforming to be carried out at a lower temperature than normal, for example the inlet temperature can be about 420°C, while raising the temperature of the pre-reforming hydrocarbon feed to a level acceptable for subsequent autothermal reforming, for example the outlet temperature of the pre-reforming and hence the inlet temperature into the autothermal reforming can be 420°C or 450°C or higher, for example in the range of 450-480°C.

[0023] Operating the ATR feed inlet at 420 or 450°C or slightly higher temperatures (e.g., 460 or 470°C) can better maintain the combustion flame in the ATR, thereby driving the partial oxidation reaction therein, while providing reliable and stable equipment performance while saving costs by eliminating the flame heaters typically required to preheat the hydrocarbon feed prior to pre-reforming and / or prior to autothermal reforming.

[0024] Furthermore, according to the present invention, in step ii), the pre-reformed hydrocarbon feed is not preheated, for example by means of a fired heater, before being subjected to autothermal reforming.

[0025] The absence of a fired heater makes less than 3wt% of the carbon in the hydrocarbon feed, for example, less than 1wt% or 0wt% of the carbon, eventually exist in the form of CO2 in the flue gas. Therefore, in the method and apparatus according to the present invention, a fired heater is not provided. Therefore, there is no direct emission in the apparatus, for example, 0wt% of the carbon in the hydrocarbon feed eventually exists in the flue gas as CO2. The carbon in the hydrocarbon feed is appropriately taken out as a CO2 product by a CO2 removal step arranged in a downstream CO2 removal section (for example, an amine wash CO2 removal unit), as will be apparent from the following embodiments. In other words, by the present invention, the use of a fired heater, for example, to preheat the hydrocarbon feed is avoided, so no flue gas is generated, and therefore the fired heater does not generate carbon emissions. The hydrocarbon feed carbon is not emitted in the form of CO2, but is recovered as a CO2 product in the CO2 removal section. Therefore, the hydrocarbon feed or fuel of the apparatus does not generate carbon emissions. The CO2 product (also referred to herein as a CO2-rich stream) can be captured and / or utilized according to known techniques, such as carbon capture and utilization (CCU) or carbon capture and storage (CCS), or a combination of the two (CCUS).

[0026] Flue gas from fired heaters is usually discharged at low pressure, so the energy and capital cost required to remove CO2 from low pressure flue gas is high. For example, the energy required to compress the flue gas and the energy required to regenerate CO2 in an amine scrubber CO2 removal unit are significantly higher, while these energies are less if CO2 is recovered from shift syngas. In addition, additional unit operations are required to cool and purify the flue gas, which increases capital expenditures. Impurities in flue gas are usually SO x and NO x , which are not suitable for use in amine wash type CO2 removal units. Therefore, in one embodiment, the present invention removes CO2 from the process gas itself, more specifically from the shifted syngas. Therefore, the present invention can also reduce capital expenditures to produce a high purity H2 stream, for example, with 99.9 vol.% H2 and 90% or more carbon capture efficiency.

[0027] In one embodiment, the first part of the shifted synthesis gas accounts for 15% or less, such as 10% or less, such as 2-8% of the volume flow of the shifted synthesis gas. In a specific embodiment, the shifted synthesis gas is taken from the medium-temperature or low-temperature shift stage of the water-gas shift step iii) and then cooled and dried, i.e. by directing the shifted synthesis gas to the cooling and the dehydration step, such as dehydration in a process condensate separator (PC-separator). The required recycle amount of the cooled and dried shifted synthesis gas is very small, such as only <15%. Therefore, this synthesis gas recycle is cost-effective because the pressure increase required in the recycle is only up to a few bars and only a small gas flow is involved. Therefore, the power of the shifted synthesis gas recycle compressor can be kept to a minimum.

[0028] Suitably, the hydrocarbon feed (also referred to herein as hydrocarbon feed gas) is natural gas.

[0029] In one embodiment, the method does not have a primary reforming step requiring heat input, and the primary reforming step is any one of steam methane reforming (SMR) and convective reforming. Therefore, the pre-reformed hydrocarbon feed is directly supplied to the autothermal pre-reforming step. The term "direct supply" means that there is no intermediate step or unit that substantially changes the composition of the stream. The method or apparatus does not include a primary reforming step (such as SMR) performed on the pre-reformed hydrocarbon feed before the autothermal reforming, and this primary reforming step requires heat input. Therefore, the method or apparatus does not include, i.e. lacks, a steam methane reforming unit (SMR) located upstream of the ATR. The primary reforming unit can also be a convective reforming unit, such as a gas-heated reforming unit, i.e., a heat exchange reformer (HER). Thus, the reforming section of the plant comprises an ATR and a pre-reforming unit, but no steam methane reforming (SMR) unit, i.e. the use of, for example, a conventional SMR (also commonly referred to as a radiant furnace or tubular reformer) or another primary reforming unit, such as a convection reforming unit (e.g. a heat exchange reformer (HER) arranged in series with the ATR, such as HER) is omitted. Thus, a reduction in plant size and an accompanying reduction in operating expenses is also achieved.

[0030] In another embodiment, the method or apparatus does not provide, ie does not exist, a subsequent reforming unit, such as a convective reforming unit, such as a HER arranged downstream of the ATR or in parallel with the ATR. Likewise, a reduction in the size of the apparatus and a reduction in operating costs are achieved.

[0031] In one embodiment, the method further comprises:

[0032] Prior to step i), the hydrocarbon feed is subjected to desulfurization, i.e. a desulfurization step; suitably, the desulfurization comprises hydrogenation and subsequent sulphur absorption; wherein step iii) comprises a high temperature shift (HTS) step for producing a first shifted synthesis gas, and optionally a subsequent medium temperature shift and / or low temperature shift step (MTS and / or LTS) step for producing a shifted synthesis gas; and wherein prior to desulfurization, the method further comprises: preheating the hydrocarbon feed by indirect heat exchange with the shifted synthesis gas from step iii), wherein the indirect heat exchange is achieved by cooling the first shifted synthesis gas (synthesis gas from the HTS step) in one or more heat exchangers; or by indirect heat exchange with superheated steam produced from heat recovery in step iii) (i.e. the water gas shift step), wherein the heat recovery comprises cooling a portion of the first shifted synthesis gas by directing the portion of the first shifted synthesis gas to a steam superheater, thereby producing the superheated steam.

[0033] Therefore, before the hydrocarbon feed is subjected to desulfurization, ie before the desulfurization step, the hydrocarbon feed is preheated by means other than a fired heater.

[0034] Typically, prior to desulfurization, more specifically prior to hydrogenation, preheating of the hydrocarbon feed is performed in a fired heater by passing the hydrocarbon feed gas through one or two preheating units (e.g., coils) arranged within the fired heater, thereby raising the temperature from about 100° C. to about 380° C. Hydrogenation is performed in a hydrogenation unit (hydrogenator), and subsequently, the hydrogenated hydrocarbon gas is directed to a sulfur absorption unit (sulfur absorber) for sulfur absorption, as is well known in the art. The desulfurized hydrocarbon feed thus leaves the sulfur absorber at a relatively low temperature, e.g., about 365° C.

[0035] It should be understood that for the purposes of this patent application, the terms "desulfurizing" and "desulfurization" can be used interchangeably.

[0036] According to the present invention, heat integration in the process or apparatus is provided by preheating the hydrocarbon feed using, for example, shifted synthesis gas from step iii) (i.e. water gas shift) rather than using a fired heater. The shifted gas, suitably first shifted synthesis gas taken from the high temperature shift (HTS) step thereof, is cooled by heat exchange with the hydrocarbon feed in a first feed heat exchanger and optionally a second feed heat exchanger (i.e. a first feed preheater and optionally a second feed preheater), thereby raising the temperature of the hydrocarbon feed gas at the hydrogenator inlet from about 100°C to about 380°C.

[0037] Preheating of the hydrocarbon feed can be achieved by indirect heat exchange with superheated steam generated from heat recovery in step iii) above (i.e. the water gas shift step), in addition to using fired heaters. Thus, instead of preheating the hydrocarbon feed downstream of the HTS, the shifted synthesis gas is used to generate more superheated steam, and this additional superheated steam heat duty is then used to preheat the hydrocarbon feed.

[0038] In a specific embodiment, after desulfurization of the hydrocarbon feed, the method includes further preheating the hydrocarbon feed by indirect heat exchange with superheated steam produced from heat recovery in step iii) (i.e., the water gas shift step), wherein the heat recovery includes cooling a portion of the first shifted synthesis gas by directing the portion to a steam superheater to produce the superheated steam.

[0039] Typically, the desulfurized hydrocarbon feed gas (typically 365° C.) is combined with steam (including directly added high temperature superheated steam) to raise the temperature of the desulfurized hydrocarbon feed gas to nearly 400° C. The superheated steam is generated in a steam superheater, typically an auxiliary boiler. The temperature of the desulfurized hydrocarbon feed gas is further raised to 450° C., which is the inlet temperature typically desired for pre-reforming, by preheating in one or more preheaters (e.g., coils) arranged in the fired heater.

[0040] According to this embodiment of the invention, further heat integration in the process or apparatus is achieved by indirectly preheating the desulfurized hydrocarbon feed using superheated steam instead of using a fired heater. Thus, a pre-reformer feed preheater is provided, i.e. a heat exchanger using superheated steam as a heat exchange medium. In the water gas shift step, the desulfurized hydrocarbon feed gas is preheated from about 365°C to about 420°C by superheated steam generated by heat recovery, for example at a temperature of 440°C.

[0041] Therefore, preheating of the desulfurized hydrocarbon feed is performed by means other than fired heaters.

[0042] Thus, in a particular embodiment step iii) comprises a high temperature shift (HTS) step for producing a first shifted synthesis gas and optionally a subsequent medium temperature shift step and / or a low temperature shift step (MTS and / or LTS) step for producing a shifted synthesis gas.

[0043] The outlet gas temperature of the HTS step is in the range of 450-500°C and is therefore suitable for indirect heat exchange to generate superheated steam in a steam superheater. Likewise, the need to use a fired heater or auxiliary boiler to provide such superheated steam is eliminated. Thus, further heat integration can be achieved without resorting to an external fuel source (e.g., using natural gas in a fired heater), while significantly reducing the carbon footprint of the process or equipment.

[0044] In one embodiment, step i) comprises recycling a portion of the pre-reformed hydrocarbon by combining it with the hydrocarbon feed.

[0045] In a specific embodiment, the method further comprises:

[0046] Prior to step i), the hydrocarbon feed is desulfurized and the pre-reformed hydrocarbon feed is combined with the desulfurized, preheated hydrocarbon feed.

[0047] These particular embodiments may be considered "short loop" in that a portion of the outlet gas from the pre-reformer is returned to the hydrocarbon feed to the pre-reformer.

[0048] Typically, as mentioned above, during the pre-reforming process, the inlet gas enters at a temperature of about 450°C, and after pre-reforming, the gas leaves the pre-reformer at a temperature of about 420°C. The pre-reformed gas is then preheated in the fired heater to the required inlet temperature for the ATR, typically 600-700°C. In addition, typically, the outlet gas from the pre-reformer does not undergo this "short cycle" either, as this would result in cooling of the inlet gas to the pre-reformer, and would also mean a greater heat load on the fired heater to further preheat the outlet gas from the pre-reformer for subsequent autothermal reforming.

[0049] In contrast, the present invention also intentionally provides a "short cycle" in the above-mentioned specific embodiment, i.e., a portion of the outlet gas of the pre-reformer is recycled back to the inlet of the pre-reformer, so that the hydrocarbon feed gas can now be further preheated when entering the pre-reformer, and the preheated hydrocarbon stream after desulfurization can be further preheated. Thus, further heat integration is achieved. Due to the exothermic heat generated during pre-reforming, the outlet temperature of the pre-reformed gas is higher than the inlet temperature, for example, the outlet gas temperature is about 450°C, while the inlet temperature is 420°C.

[0050] Suitably, the portion of pre-reformed hydrocarbon that is recycled represents 10-30%, such as 15-20%, of the volume flow of pre-reformed hydrocarbon.

[0051] In a specific embodiment, the portion of the pre-reformed hydrocarbon feed is recycled through an ejector, which receives the portion of the pre-reformed hydrocarbon feed as a driving fluid and pressurized steam as a motive fluid; and optionally, the portion of the pre-reformed hydrocarbon feed is combined with the hydrocarbon feed after mixing the first portion of the recycled shift synthesis gas (shift synthesis gas recycle) with the hydrocarbon feed, that is, the mixing point for the recycling of the pre-reformed hydrocarbon feed is located downstream of the shift synthesis gas recycle mixing point.

[0052] Using an ejector without moving parts is a simple and effortless solution to achieve mixing of the recirculating flow with pressurized steam for use.

[0053] In one embodiment, the method further comprises adding pressurized steam to the preheated hydrocarbon feed after desulfurization, suitably also after combining the first portion of the shift synthesis gas with the hydrocarbon feed. Thus, the mixing point of the pre-reformed hydrocarbon feed with the pressurized steam is located downstream of the mixing point of the shift synthesis gas recycle. Also suitably, the preheated hydrocarbon feed after desulfurization and the pressurized steam are combined before recycling a portion of the pre-reformed hydrocarbons. The pressurized steam is supplied, for example, at about 50 barg and about 430° C., so that the temperature of the stream fed to the pre-reformed is raised to the desired level, for example about 420° C. Suitably, the pressurized steam is the same stream as the high-pressure steam that is diverted off for use as an ejector.

[0054] The temperature of the shifted synthesis gas recycle is, for example, 350-370° C., thereby reducing the temperature of the preheated hydrocarbon feed after desulfurization to, for example, about 410° C. The recycle stream provided by the ejector is suitably about 450° C. and is added downstream of the shifted synthesis gas recycle mixing point, thereby being able to at least partially increase the temperature to the desired inlet temperature of the pre-reformer, for example 420° C.

[0055] In one embodiment, as previously described, the shifted syngas recycle is a cooled and dried shifted syngas. Thus, the first portion of the shifted syngas that is recycled (the shifted syngas recycle) is a shifted syngas from which moisture has been removed in a water separation step (suitably carried out in a process condensate separator), thereby producing a dry shifted syngas stream, i.e. a water-depleted shifted syngas stream. In the pre-reforming step, the presence of water in the shifted syngas recycle is detrimental to the desired methanation reaction CO2+4H2=CH4+2H2O.

[0056] The shifted synthesis gas recycle may then be compressed in a recycle compressor and heated in one or more heat exchangers using steam as a heat exchange medium to preheat the shifted synthesis gas recycle to, for example, 350-370°C as described above, and then mixed with the hydrocarbon feed entering the pre-reforming. For example, the shifted synthesis gas recycle is preheated by indirect heat exchange with steam (including, for example, superheated steam) produced in the process. A second portion of the shifted synthesis gas from the process condensate separator (PC separator) may be directed to a CO2 removal step, for example, at about 60°C. A first portion of the shifted synthesis gas from the PC separator is diverted to the shifted synthesis gas recycle, which may then also have a temperature of about 60°C. Again, the preheating of the shifted synthesis gas recycle raises the temperature to, for example, about 360°C, and then is combined with the optionally desulfurized hydrocarbon feed upstream of the pre-reformer.

[0057] Also suitably, the first part of the shifted synthesis gas that is recycled (shifted synthesis gas recycle) is the shifted synthesis gas from the MTS and / or LTS step in step iii), i.e. the water gas shift step. This shifted synthesis gas is the most hydrogen-rich synthesis gas from the shift step, for example comprising the aforementioned about 70 vol.% hydrogen and about 25 vol.% carbon dioxide, and is therefore advantageously used for recycling to the hydrocarbon feed gas, in particular to the pre-reforming step. The H2 and CO2 content in the shifted synthesis gas promotes the exothermic methanation reaction in the pre-reforming step. Therefore, the required amount of shifted synthesis gas recycle is very small, for example <10% of the flow rate, as further explained above. Therefore, in one embodiment, the first part of the shifted synthesis gas that is recycled has more than 70 vol.% H2 and more than 25 vol.% CO2.

[0058] In one embodiment, the method further comprises:

[0059] iv) subjecting a second portion of the shifted synthesis gas stream to CO2 removal to produce a CO2-depleted shifted synthesis gas; and optionally

[0060] v) hydrogen enriching the shifted synthesis gas or the CO2-depleted shifted synthesis gas in a hydrogen purification unit to produce a hydrogen product and an off-gas stream; and wherein the off-gas stream (e.g. a portion thereof) is not recycled to any of steps i) to iv).

[0061] Thus, a simple, energy efficient, low carbon footprint method for the production of hydrogen is provided, including hydrogen that can be used in the method, since at least the need for a fired heater (eg, to preheat the hydrocarbon feed) is eliminated compared to the prior art.

[0062] For example, in step iv), the CO2-depleted shifted synthesis gas stream is rich in hydrogen, for example, has 97 mol% or more H2 and less than 100 ppmv CO2, for example 50 ppmv or less. Therefore, a portion of this gas stream can be used as an H2 recycle stream to the hydrocarbon feed, thereby providing, for example, the hydrogen required for hydrogenation in the desulfurization step. For example, in step v), the hydrogen product has 99 mol% or more H2, for example 99.9 mol%, and no detectable CO2. A portion of the hydrogen product can also be used as an H2 recycle stream.

[0063] From the CO2 removal step, ie from the CO2 removal section, a CO2-rich stream is also withdrawn as CO2 product, for example containing 95 vol.% (mol %) or more, such as 99.5 vol.% carbon dioxide.

[0064] Furthermore, no off-gas stream is recycled to any of the process steps i) to iv). Thus, the off-gas from the hydrogen enrichment step v) (e.g. in a hydrogen purification unit (e.g. a PSA unit)) is not combined with the process gas. Thus, the off-gas stream is not combined with, for example, the hydrocarbon feed of step i), the pre-reformed hydrocarbon feed of step ii), the crude synthesis gas of step ii) or the shifted synthesis gas of step iii). Thus, a simpler process and plant layout is provided, thus also with lower capital and operating expenditures, since it is not necessary, for example, to provide an off-gas recirculation compressor and the accompanying piping, as well as means for heating the off-gas recirculation to the required temperature for any of the process steps.

[0065] In one embodiment, before the pre-reforming step or before the desulfurization, the hydrocarbon feed is supplied to a feed gas compressor, and:

[0066] - the recycle in step iii) comprises combining a first part of the shifted synthesis gas stream with a hydrocarbon feed and then supplying it to a feed gas compressor, i.e. combining the shifted synthesis gas recycle with the hydrocarbon feed and then supplying it to the feed gas compressor (in other words, the shifted synthesis gas recycle is brought to the suction inlet of the feed gas compressor).

[0067] Thus, the need to provide a dedicated shifted syngas recycle compressor is eliminated. Furthermore, while a portion of the CO2-depleted shifted syngas stream or a portion of the hydrogen product (i.e. as H2 recycle) may be recycled to the hydrocarbon feed, when the shifted syngas recycle is brought to the feed gas compressor suction, such H2 recycle may not be required, thus representing a significant further advantage of this embodiment as the process and apparatus become simpler.

[0068] The first part of the shifted synthesis gas that is recycled is sent to the hydrocarbon feed before being supplied to the feed gas compressor, therefore, upstream of the feed gas compressor, only this feed compressor is required. If the first part of the shifted synthesis gas that is recycled is combined with the hydrocarbon feed that is directed to the pre-reforming (i.e. the pre-reformer inlet), a dedicated shifted synthesis gas recycle compressor is required.

[0069] When shifted syngas recycle is added to the inlet pre-reformer, H2 recycle may be provided. Therefore, in another embodiment, the method further comprises: prior to step i), desulfurizing the hydrocarbon feed, and said recycle in step iii) comprises combining a first portion of said shifted syngas with the desulfurized hydrocarbon feed; prior to said pre-reforming step or prior to said desulfurization, the hydrocarbon feed is supplied to a feed gas compressor, and the method further comprises recycling a portion of the CO2-depleted shifted syngas stream or a portion of the hydrogen product to the hydrocarbon feed, which is then supplied to the feed gas compressor.

[0070] Therefore, there is also no need to provide a dedicated hydrogen recirculation compressor. Furthermore, integration of process streams is thereby achieved without resorting to external sources, for example in the hydrogenator, to provide the required hydrogen. The energy efficiency of the method or the apparatus is increased; at the same time, the substantial costs (capital and operating expenditures) usually associated with providing such a recirculation compressor are eliminated.

[0071] Typically, hydrogen recycle is provided by a hydrogen recycle compressor which adds hydrogen product from, for example, a pressure swing adsorption unit (PSA unit) to a point downstream of the feed gas compressor and then preheats it to the hydrogenator inlet temperature, which is typically about 380° C. In contrast, hydrogen recycle can be added to the hydrocarbon feed upstream of the feed gas compressor, thereby again avoiding the need to provide such a hydrogen recycle compressor.

[0072] In one embodiment, the pre-reforming step i) is carried out in an adiabatic pre-reformer, wherein the inlet temperature of the hydrocarbon feed gas is in the range of 380-430°C, for example 420°C; and the autothermal reforming step ii) is carried out in an autothermal reformer (ATR), wherein the inlet temperature of the pre-reformed hydrocarbon feed is in the range of 420-480°C, for example 450°C, substantially corresponding to the temperature of the pre-reformed hydrocarbon feed leaving the pre-reformer.

[0073] It is to be understood that the term "substantially corresponds to the temperature of the pre-reformed hydrocarbon feed leaving the pre-reformer" means that the temperature is not necessarily exactly the same, but is within a range of, for example, 10° C. or less, such as less than 5° C. The pre-reformed hydrocarbon feed may be mixed with steam before entering the ATR, and thus the temperature is slightly reduced, such as the less than 5° C.

[0074] Thus, the pre-reformed hydrocarbon feed does not need to be preheated, such as by a fired heater, prior to being subjected to autothermal reforming.

[0075] Thus, the hydrocarbon feed is preheated by means other than a fired heater prior to desulfurization of the hydrocarbon feed, or after desulfurization of the hydrocarbon feed but prior to pre-reforming, or after pre-reforming but prior to autothermal reforming.

[0076] In addition to the benefits associated with eliminating fired heaters, including cost savings and, more importantly, significant reductions in carbon emissions, operating the ATR inlet at 420-480°C or 450-480°C can also provide reliable and stable equipment performance.

[0077] In one embodiment, the steam to carbon molar ratio (S / C ratio) in the pre-reforming step i) is 1.0 or less, such as 0.8 or less, such as 0.6 or less, such as 0.5.

[0078] It will be understood that the term "S / C ratio in the pre-reforming step i)" or "S / C ratio in the pre-reformer" refers to the molar ratio of steam to carbon, which is defined as the molar ratio of all steam added to the hydrocarbon feed (including any water in the recycled shifted synthesis gas) to all carbon in the hydrocarbons in the hydrocarbon feed gas.

[0079] For example, the pre-reforming step i) is carried out at an S / C ratio of 1.0 or lower, such as 0.8 or lower, such as 0.6 or lower, such as 0.5, and the hydrocarbon feed temperature in the pre-reforming step i), i.e. the inlet temperature of the pre-reformer is 380-430°C, such as 400-430°C.

[0080] Although it is known in the art (e.g. WO 2022038089 of the applicant) to operate the ATR at a low S / C ratio and low inlet temperature (below 600°C, e.g. 550°C or 500°C or lower, e.g. 300-400°C), a related benefit of now combining a low S / C value in the pre-reformer (e.g. 0.5) with a low inlet temperature of the pre-reformer (e.g. 400°C) is that, due to the reduced flow, the preheating requirement before the pre-reformer is further reduced, which can be easily met by heat integration and again no external heating source (e.g. use of natural gas in the fired heater) is required.

[0081] In the ATR, additional steam can be added, for example by feeding it into the ATR along with the oxygen stream, to produce a slightly higher S / C ratio in the ATR. For example, if the S / C ratio in the pre-reformer is 0.5, the S / C ratio in the ATR is 0.6 or higher.

[0082] In one embodiment, the method comprises preheating the hydrocarbon feed or pre-reformed hydrocarbon feed by electrical heating (i.e. in an electric heater) before carrying out the autothermal reforming step ii). Suitably, the electric heater is driven by electricity provided from a renewable energy source (e.g. solar, wind or hydroelectric), optionally provided by a thermonuclear energy source. This is advantageous during the start-up operation of the method or apparatus so that the required temperature of the ATR or other process unit can be reached.

[0083] Suitably, the ATR is operated at an inlet temperature of the pre-reformed hydrocarbon feed of 420°C or more, or 450°C or more, such as 450-480°C, and a pressure range of 35-45 barg. Also suitably, the steam-to-carbon ratio in the ATR is 0.5 or more, such as 0.6 or more, or such as 0.8 or more, but the steam-to-carbon ratio is not greater than 2.0. Operating the process or apparatus at these low steam-to-carbon ratios in the ATR can reduce energy consumption and reduce the size of the apparatus because less steam / water is carried through the apparatus.

[0084] The term "steam to carbon ratio in the ATR" (or alternatively expressed as S / C ratio or steam to carbon ratio) as used herein refers to the steam to carbon molar ratio in the ATR, defined as the molar ratio of all steam added to the hydrocarbon feed and the ATR (i.e., excluding any steam added to the downstream shift section) to all carbon in the hydrocarbons in the pre-reformed feed gas (pre-reformed hydrocarbon feed). More specifically, the steam to carbon ratio is defined as the ratio of all steam added to the reforming section upstream of the shift section (e.g., high temperature shift section) (i.e., steam that may have been added to the reforming section via feed gas, oxygen feed, by being added to the ATR) to the carbon in the hydrocarbons in the feed gas (hydrocarbon feed) entering the reforming section on a molar basis. Added steam includes only steam added to the ATR and upstream of the ATR.

[0085] The term "reforming section" refers to the section of the plant upstream of the water-gas shift section, including hydrogenators, sulfur absorbers, pre-reformers and ATRs. In addition, for the purposes of this application, the term "desulfurization section" includes hydrogenators and sulfur absorbers.

[0086] In another general embodiment of the first aspect, the present invention is a method for producing a hydrogen product from a hydrocarbon feed, comprising the steps of:

[0087] i) desulfurizing and pre-reforming a hydrocarbon feed to produce a pre-reformed hydrocarbon feed;

[0088] ii) autothermal reforming of the pre-reformed hydrocarbon feed to produce a crude synthesis gas;

[0089] iii) subjecting the raw synthesis gas stream to a water gas shift to produce a shifted synthesis gas, and dividing the shifted synthesis gas into a first portion and a second portion;

[0090] iv) removing CO2 from the second portion of the shifted synthesis gas to produce a CO2-depleted shifted synthesis gas;

[0091] v) enriching the shifted synthesis gas or the CO2-depleted shifted synthesis gas with hydrogen in a hydrogen purification unit to produce a hydrogen product and an off-gas stream;

[0092] in

[0093] Prior to the desulfurization and pre-reforming steps, a hydrocarbon feed is supplied to a feed gas compressor, and wherein the method further comprises:

[0094] - combining a first portion of the shifted synthesis gas with a hydrocarbon feed and then feeding it to a feed gas compressor; and / or

[0095] - Between said desulphurisation and pre-reforming steps, a first portion of the shifted synthesis gas is combined with a hydrocarbon feed.

[0096] Any of the above embodiments and their associated benefits may be combined with this general embodiment of the first aspect.

[0097] In a second aspect, there is also provided an apparatus for producing synthesis gas from a hydrocarbon feed, comprising:

[0098] - a pre-reformer arranged to receive a hydrocarbon feed to produce a pre-reformed hydrocarbon feed;

[0099] - a feed gas compressor arranged upstream of the pre-reformer for directing the hydrocarbon feed to the pre-reformer;

[0100] - an autothermal reformer (ATR) arranged to receive a pre-reformed hydrocarbon feed and convert it into a crude synthesis gas;

[0101] a water-gas shift section (WGS section) arranged to receive the raw synthesis gas from the ATR and to shift it in at least one high temperature shift step (HTS step) so as to provide a shifted synthesis gas as said synthesis gas;

[0102] wherein the apparatus is devoid of a fired heater for preheating the hydrocarbon feed or preheating the pre-reformed hydrocarbon feed;

[0103] Wherein the apparatus is arranged for supplying a first portion of the shifted synthesis gas to a point upstream of the pre-reformer; that is, the apparatus is provided with a conduit for recycling a first portion of the shifted synthesis gas stream to a point upstream of the pre-reformer.

[0104] It will be appreciated that said first portion of shifted synthesis gas which is fed to the pre-reformer is also referred to as "shifted synthesis gas recycle".

[0105] In relation to the first aspect of the invention (the method), the shifted synthesis gas recycle is a portion taken directly from the water separation step (e.g. in a process condensate separator). Thus, the shifted synthesis gas recycle is fed directly to a point upstream of the pre-reformer. The term "directly fed", as already stated in the first aspect of the invention, means that there are no intermediate steps or units that substantially change the composition of the stream. It is also to be understood that "fed to" and "fed to" are used interchangeably.

[0106] In one embodiment according to the second aspect of the present invention, the device further comprises a desulfurization section, which suitably comprises a hydrogenator and a sulfur absorber, and the desulfurization section is arranged upstream of the pre-reformer for desulfurizing the hydrocarbon feed. Therefore, there is also provided a device for generating synthesis gas from a hydrocarbon feed, comprising:

[0107] - a pre-reformer arranged to receive a hydrocarbon feed to produce a pre-reformed hydrocarbon feed;

[0108] - a desulfurization section, comprising a hydrogenator and a sulfur absorber located upstream of the pre-reformer, for desulfurizing the hydrocarbon feed;

[0109] a feed gas compressor arranged upstream of the pre-reformer or upstream of the desulfurization section for directing the hydrocarbon feed to the pre-reformer or the desulfurization section;

[0110] - an autothermal reformer (ATR) arranged to receive a pre-reformed hydrocarbon feed and convert it into a crude synthesis gas;

[0111] a water-gas shift section (WGS section) arranged to receive the raw synthesis gas from the ATR and to shift it in at least one high temperature shift step (HTS step) so as to provide a shifted synthesis gas as said synthesis gas;

[0112] wherein the apparatus is devoid of a fired heater for preheating the hydrocarbon feed or preheating the pre-reformed hydrocarbon feed;

[0113] Wherein the apparatus is arranged to feed the first part of the shifted synthesis gas to a point upstream of the pre-reformer; that is, the apparatus is provided with a conduit for recycling the first part of the shifted synthesis gas stream to a point upstream of the pre-reformer.

[0114] Thus, according to a second aspect, the present invention is a synthesis gas production plant based on an ATR without a dedicated fired heater, which is usually used to preheat the hydrocarbon feed to the temperature required for the reforming stage (including the desulfurization stage, the pre-reformer and the ATR). The fired heater is a large and costly device, requiring a considerable floor space in the plant and involving a large amount of direct carbon emissions. The plant according to the present invention does not have a fired heater, which can reduce the associated carbon emissions and reduce costs (capital and operating expenses).

[0115] In one embodiment, the device further comprises:

[0116] a CO2 removal section arranged to receive a second portion of the shifted syngas from said WGS section and to separate a CO2-rich stream therefrom, thereby providing a CO2-depleted shifted syngas,

[0117] a hydrogen purification unit arranged to receive a second portion of said shifted synthesis gas or said CO2-depleted shifted synthesis gas from said CO2 removal section and separate it into a hydrogen product and an off-gas stream;

[0118] And wherein the apparatus is devoid of ducting and / or exhaust gas recirculation compressor for directing at least a portion of the exhaust gas flow to any of the desulfurization section, pre-reformer, ATR and WGS section.

[0119] Therefore, the second aspect of the present invention also provides an ATR-based hydrogen production plant, in which the exhaust gas is not recycled to the different process units in the plant. Therefore, the exhaust gas from the hydrogen purification unit (such as a PSA unit) is not mixed with the process gas sent to any upstream unit: the exhaust gas flow is not mixed with, for example, the hydrocarbon feed directed to the desulfurization section or the pre-reformer, or the pre-reformed hydrocarbon feed directed to the ATR, or the crude synthesis gas directed to the conversion section, or the conversion synthesis gas in the conversion section. Therefore, a simpler equipment layout is provided, and therefore also has lower capital and operating expenses, because there is no exhaust gas recirculation compressor and associated piping, and there is no device for heating the exhaust gas recirculation to the required temperature for any process step.

[0120] In one embodiment, the apparatus is arranged to supply a first portion of the shifted synthesis gas to the inlet of the pre-reformer, and the apparatus is further arranged to supply a portion of the CO2-depleted shifted synthesis gas or a portion of the hydrogen product to the hydrocarbon feed upstream of the feed gas compressor. Thus, the apparatus comprises a conduit for recycling the first portion of the shifted synthesis gas to the inlet of the pre-reformer; and the apparatus further comprises a conduit for supplying a portion of the CO2-depleted shifted synthesis gas or a portion of the hydrogen product to the hydrocarbon feed upstream of the feed gas compressor.

[0121] Thus, a dedicated hydrogen recycle compressor is eliminated.

[0122] In certain embodiments, the plant is devoid of a shifted synthesis gas recycle compressor and / or a hydrogen recycle compressor.

[0123] In an embodiment, the apparatus is arranged to feed (i.e. recycle) a first portion of the shifted synthesis gas into a hydrocarbon feed upstream of a feed gas compressor; and suitably, the apparatus does not require means such as a pipeline and / or a recycle compressor for feeding a portion of the CO2-depleted shifted synthesis gas or a portion of the hydrogen product into the hydrocarbon feed upstream of the feed gas compressor. Thus, the apparatus includes a pipeline for recycling the first portion of the shifted synthesis gas into the hydrocarbon feed upstream of the feed gas compressor.

[0124] By arranging the plant to feed a portion of the shifted synthesis gas into the hydrocarbon feed upstream of the feed gas compressor (in other words, to circulate the shifted synthesis gas to the suction of the feed gas compressor), no H2 recycle is required, for example by feeding a portion of the hydrogen product into the hydrocarbon feed, thereby providing a simpler plant layout.

[0125] Furthermore, there is no need to provide a dedicated shifted synthesis gas recycle compressor. As described in the first aspect of the invention, further integration of process streams is thereby provided, without resorting to external sources, such as providing the required hydrogen in the hydrogenator of the desulfurization section. The energy efficiency of the method or apparatus is improved; at the same time, the substantial costs (capital and operating expenditures) usually associated with providing such a recycle compressor are also eliminated.

[0126] In one embodiment, the WGS segment comprises:

[0127] - high temperature shift units (HTS units), as well as medium temperature shift units (MTS units) or low temperature shift units (LTS units);

[0128] - a downstream end comprising one or more heat exchangers for cooling the shifted synthesis gas taken from the MTS or LTS unit, and a process condensate separator (PC separator) for separating process condensate (water) from the shifted synthesis gas, thereby providing a cooled and dried shifted synthesis gas; and a device for diverting it, such as a joint or a connector, feeding a first part of the diverted shifted synthesis gas to the upstream of the pre-reformer, and optionally also feeding a second part of the diverted shifted synthesis gas to the CO2 removal section.

[0129] As a result, the shifted syngas has a higher content of H2 and CO2, for example more than 70 vol.% hydrogen and more than 25 vol.% carbon dioxide, which leads to a methanation reaction in the pre-reformer, which is an exothermic reaction, resulting in an increase in the temperature of the hydrocarbon feed throughout the pre-reformer. The first part of the shifted syngas is dry, so water has been removed, thereby promoting the methanation reaction in the pre-reformer. As mentioned in connection with the first aspect of the present invention, the presence of water in the shifted syngas recycle is detrimental to the desired methanation reaction CO2+4H2=CH4+2H2O, etc. in the pre-reformer.

[0130] The amount of shifted synthesis gas recycle required is small, for example less than 10% of the shifted synthesis gas volume flow, which is cost-effective because the required pressure increase is at most a few bars and only involves small gas flows, as described in connection with the first aspect of the invention.

[0131] In one embodiment, the pre-reformer is equipped with an ejector for recycling a portion of the pre-reformed hydrocarbon feed (i.e. the stream leaving the pre-reformer) to the hydrocarbon feed (i.e. the stream introduced into the pre-reformer). The ejector is arranged to receive the recycle, i.e. a portion of the pre-reformed hydrocarbon feed, as a driving fluid, and to receive pressurized steam as a motive fluid. As described in connection with the first aspect of the invention, providing an ejector without moving parts is a simple and uncomplicated solution to achieve mixing of the recycled pre-reformed stream with the pressurized steam. The pressurized steam is supplied, for example, at about 50 barg and about 430°C.

[0132] In one embodiment, the apparatus does not have a primary reformer located upstream of the ATR that requires heat input, the primary reformer being any one of a steam methane reformer (SMR) and / or a convection reforming unit (e.g., a heat exchange reformer (HER)). In another embodiment, the apparatus does not have a reformer located downstream of the ATR or arranged in parallel with the ATR that requires heat input, such as a convection reformer, such as a heat exchange reformer (HER). Therefore, a reduction in the size of the apparatus is also achieved.

[0133] According to another general embodiment of the second aspect of the present invention, there is also provided an apparatus for producing synthesis gas from a hydrocarbon feed, comprising:

[0134] - a pre-reformer arranged to receive a hydrocarbon feed to produce a pre-reformed hydrocarbon feed;

[0135] - a feed gas compressor arranged upstream of the pre-reformer for directing the hydrocarbon feed to the pre-reformer;

[0136] - an autothermal reformer (ATR) arranged to receive a pre-reformed hydrocarbon feed and convert it into a crude synthesis gas;

[0137] a water-gas shift section (WGS section) arranged to receive raw synthesis gas from the ATR and to shift it in at least one high temperature shift step (HTS step) so as to provide a shifted synthesis gas as said synthesis gas; and a downstream section comprising a process condensate separator (PC separator) for separating process condensate (water) from the shifted synthesis gas;

[0138] wherein the apparatus is arranged for feeding a first portion of the shifted synthesis gas from the PC separator to a point upstream of a pre-reformer; i.e. the apparatus is provided with a conduit for recycling a first portion of the shifted synthesis gas stream to a point upstream of a pre-reformer.

[0139] Suitably also, a heat exchanger for cooling the shifted synthesis gas withdrawn from the MTS or LTS unit is provided upstream of the PC separator.

[0140] Any embodiment and associated benefits of the first aspect of the invention (the method) may be used with any embodiment of the second aspect of the invention (the apparatus).

[0141] According to any one of the first or second aspects of the present invention, further details of the present invention are as follows.

[0142] Suitably, a plurality of pre-reformers are arranged upstream of the ATR.For example, the apparatus may comprise two or more adiabatic pre-reformers arranged in series with an interstage preheater (ie a preheater between the pre-reformers).

[0143] In the pre-reformer, all higher hydrocarbons can be converted to carbon oxides and methane, but the pre-reformer is also beneficial for light hydrocarbons. Providing a pre-reformer, and thus a pre-reforming step, may have various advantages, including reducing the required O2 consumption in the ATR. In addition, the pre-reformer can provide effective sulfur protection, so that the feed gas entering the ATR and downstream systems is almost sulfur-free.

[0144] It should be understood that according to the first aspect of the present invention, the term "process gas" refers to any gas stream treated in a hydrogenator and a sulfur absorber, or in a pre-reformer, whereby the process gas is a hydrocarbon feed; or any gas stream treated in an ATR, whereby the process gas is a pre-reformed hydrocarbon feed or a crude synthesis gas; or any gas stream treated in a shift section, whereby the process gas is a shifted synthesis gas or synthesis gas; optionally any gas stream treated in a carbon dioxide removal section, whereby the process gas is a CO2-depleted shifted synthesis gas; or optionally any gas stream treated in a hydrogen purification unit.

[0145] Suitably, the high temperature shift (HTS) unit comprises a promoted zinc alumina based high temperature shift catalyst, preferably arranged in the form of one or more catalyst beds within the HTS unit, and preferably wherein the promoted zinc alumina based HTS catalyst in its active form comprises, based on the weight of the oxidation catalyst, a Zn / Al molar ratio in the range of 0.5 to 1.0 and an alkali metal content in the range of 0.4 to 8.0 wt. % and a copper content in the range of 0-10%, such as disclosed in the applicant's US2019 / 0039886A1.

[0146] Standard use of iron-based high temperature shift catalysts in conventional hydrogen plants requires a steam to carbon ratio of approximately 3.0 to avoid the formation of iron carbide.

[0147] (1)

[0148] The formation of iron carbides weakens the catalyst particles and can lead to catalyst disintegration and increased pressure drop.

[0149] Iron carbide will catalyze the formation of byproducts in the Fischer-Tropsch reaction

[0150] (2)

[0151] The Fischer-Tropsch reaction consumes hydrogen, thereby reducing the efficiency of the shift stage.

[0152] In an advantageous embodiment of the process, the catalyst based on zinc aluminum oxide in active form comprises a mixture of zinc aluminum spinel and zinc oxide, in combination with an alkali metal selected from the group consisting of Na, K, Rb, Cs and mixtures thereof, and optionally in combination with Cu. As mentioned above, the catalyst has 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 8.0% by weight, and a copper content in the range of 0-10%, based on the weight of the oxidic catalyst.

[0153] The high temperature shift catalyst used in the present process is not limited by strict steam to carbon ratio requirements (such as the above ratio of about 3.0 to avoid the formation of iron carbide), which allows for lower steam / carbon ratios in the shift and reforming stages.

[0154] The amount of steam carried in the equipment and / or method is significantly reduced, thereby reducing the equipment scale and energy consumption. More specifically, the steam / carbon ratio in the ATR is less than 2.0, but is 0.4 or 0.6 or even higher, such as 0.8, which has several advantages. Generally reducing the steam / carbon ratio will result in a reduction in the feed and steam flow through the reforming section and the downstream cooling and hydrogen purification section. In the reforming section and the conversion section, the low steam / carbon ratio also makes the production (throughput) of synthesis gas higher than that at a high steam / carbon ratio. The reduced mass flow through these sections means a reduction in equipment and pipeline size. The reduced mass flow will also result in a reduction in the generation of low-temperature heat (calories), which is usually unavailable. This means that there is a potential for reduction in both capital expenditures and operating expenses.

[0155] Since the process of the present invention requires a significantly lower steam / carbon ratio in the high temperature shift step than in the known art, the present invention can reduce the steam / carbon ratio through the front end to, for example, 0.4 or 0.6 or 0.8. An advantage of the low steam / carbon ratio of the ATR and shift section is that smaller equipment size is required at the front end, as the total mass flow through the equipment is reduced, as described above.

[0156] It will be understood that the term "front end" refers to the reforming section.

[0157] Suitably, the apparatus further comprises an air separation unit (ASU) arranged to receive an air stream and produce an oxygen stream which is then fed to the ATR via a conduit. Preferably, the oxygen-containing gas stream comprises steam which is added to the ATR. Examples of oxidant-containing streams are: oxygen; a mixture of oxygen and steam; a mixture of oxygen, steam and argon and oxygen-enriched air.

[0158] The syngas temperature at the outlet of the ATR is between 900 and 1100° C., or between 950 and 1100° C., and typically between 1000 and 1075° C. This hot effluent syngas (raw syngas) removed from the ATR contains carbon monoxide, hydrogen, carbon dioxide, steam, residual methane, and various other components including nitrogen and argon.

[0159] The carbon feed for the ATR is mixed with oxygen and additional steam in the ATR and a combination of at least two types of reactions occurs. The two reactions are combustion and steam reforming.

[0160] Burning Zone:

[0161] (3)

[0162] (4)

[0163] Thermal and Catalytic Zones:

[0164] (5)

[0165] (6)

[0166] The combustion of methane to form carbon monoxide and water (reaction (4)) is a highly exothermic process. When all the oxygen has been converted, an excess of methane may be present at the combustion zone outlet.

[0167] The hot zone is the part of the combustion chamber where further conversion of hydrocarbons takes place by homogeneous gas phase reactions, mainly reactions (5) and (6). The endothermic steam reforming of methane (5) consumes most of the heat generated in the combustion zone.

[0168] The combustion chamber may be followed by a fixed catalyst bed, the catalytic zone, in which the final hydrocarbon conversion takes place by heterogeneous catalysis. At the outlet of the catalytic zone, the synthesis gas is preferably close to the equilibrium state of reactions (5) and (6).

[0169] In one embodiment, the process does not involve additional steam addition between the reforming step and the high temperature shift step.

[0170] Autothermal reforming (ATR) is widely described in the art and in the open literature, for example in "Studies in Surface Science and Catalysis", Vol. 152 (2004); Andre Steynberg and Mark Dry, eds., Chapter 4; and in "Tubular reforming and autothermal reforming of natural gas - an overview of available processes", 1b An overview is also provided in Fuel Processing Technology 42 (1995) 85-107.

[0171] The apparatus preferably also comprises a conduit for adding steam to the hydrocarbon feed, the oxygen-containing gas stream and the ATR, and optionally also comprises a conduit for adding steam to the inlet of the reforming section (e.g. the hydrocarbon feed), and a conduit for adding steam to the inlet of the shift section (in particular the inlet of the HTS unit), and / or a conduit for adding steam to an additional shift unit downstream of the HTS unit, as will be further described below.

[0172] According to the present invention, the conversion section may further comprise one or more additional conversion units downstream of the HTS unit, wherein the one or more additional conversion units are one or more medium temperature conversion (MTS) units and / or one or more low temperature conversion (LTS) units (150), wherein the device is arranged to provide an LTS inlet temperature below 250°C, for example 190-250°C.

[0173] Providing additional shift units or shift steps increases the flexibility of the apparatus and / or method. 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 converted in the shift step, the more H2 is obtained and the smaller the front end required.

[0174] This can also be seen from the exothermic shift reaction:

[0175] 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 the performance of said subsequent HT, MT and / or LT shift steps.

[0176] Connecting 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 possible cooling and / or steam addition in between) may be advantageous because it may provide higher shift conversions at high temperatures, thereby potentially reducing the required volume of shift catalyst and thus potentially reducing capital expenditures. In addition, high temperatures reduce the formation of methanol, a typical shift step by-product.

[0177] Preferably, the MT and LT shift steps can be carried out over a promoted copper / zinc / alumina catalyst. For example, the low temperature shift catalyst type can be LK-821-2, which is characterized by high activity, high strength and high tolerance to sulfur poisoning. A top layer of special catalyst can be installed to capture chlorine that may be present in the gas and prevent droplets from contacting the shift catalyst.

[0178] The MT shift step may be performed at a temperature of 190 to 360°C.

[0179] The LT transformation step can be performed at T 露点 The temperature range of the low temperature shift is 15 to 290°C, for example 200 to 280°C. For example, the inlet temperature of the low temperature shift is T 露点 Add 15 to 250°C, for example 190 to 210°C.

[0180] Lowering the steam / carbon ratio reduces the dew point of the process gas, which means that the inlet temperature to the MT and / or LT shift step can be reduced. Lower inlet temperatures mean lower CO slippage at the shift reactor outlet, which is also advantageous for the apparatus and / or process.

[0181] It is well known that MT / LT shift catalysts tend to produce methanol as a by-product. The formation of this by-product can be reduced by increasing the steam / carbon ratio. The CO2 scrubbing that may be performed after the MT / LT shift requires heat to regenerate the CO2 absorbing solution. This heat is usually provided by the process gas as sensible heat, but this is not always sufficient. Usually, a make-up heat duty is provided by an additional steam fired reboiler. Optionally, the addition of steam to the process gas can replace this additional steam driven reboiler while ensuring a reduction in by-product formation in the MT / LT shift section.

[0182] The apparatus may further comprise a methanol removal section arranged between the shift section and the CO2 removal section, the methanol removal section being arranged to separate a methanol-rich stream from the shifted synthesis gas stream. Methanol formed by the MT / LT shift catalyst may optionally be removed from the synthesis gas by water washing, which is arranged upstream of the CO2 removal step or carried out in the CO2 product stream.

[0183] The hydrogen purification unit is selected from a pressure swing adsorption (PSA) unit, a hydrogen membrane or a cryogenic separation device, preferably a PSA.

[0184] The CO2 removal section is selected from an amine wash unit, or a CO2 membrane, ie a CO2 membrane separation unit, or an acryogenic separation unit, preferably an amine wash unit.

[0185] In one embodiment, the amine scrubbing unit comprises a CO2 absorber and a CO2 stripper as well as a high-pressure flash tank and a low-pressure flash tank, thereby separating a CO2-rich stream containing more than 99 vol.% CO2, such as 99.5 vol.% CO2 or 99.8 vol.% CO2, a H2-rich stream containing 98 vol.% hydrogen, and a high-pressure flash gas containing about 60 vol.% CO2 and 40 vol.% H2. In the amine scrubbing unit, in the first high-pressure flash step through the high-pressure tank, most of the impurities are released into the gas phase as high-pressure flash gas together with some CO2. In the low-pressure flash step through the low-pressure flash tank, the main CO2 is released as a CO2-rich stream as the final product.

[0186] The CO2 in the CO2 removal step is preferably captured and used for other purposes to reduce the emission of CO2 into the atmosphere. For example, the separated CO2 can be sequestered in geological formations or used as an industrial gas for various purposes. Thus, the carbon in the hydrocarbon feed is captured as CO2.

[0187] The attached single figure shows a schematic diagram of a method or apparatus for producing synthesis gas and hydrogen based on ATR according to an embodiment of the present invention.

[0188] The figure shows a method or apparatus 100 for producing a hydrogen product 23 from a hydrocarbon feed 1, which includes a desulfurization section including a hydrogenator 10 and a sulfur absorber 12. The method or apparatus also includes a pre-reformer 14, an autothermal reformer (ATR) 16, a water gas shift section (WGS section) 18, a CO2 removal section 20 and a hydrogen purification unit 22. A hydrocarbon feed 1 (e.g. natural gas) is fed to a reforming section including a desulfurization section (hydrogenator 10, sulfur absorber 12), a pre-reformer 14 and an ATR 16. The hydrocarbon feed 1 is combined with a hydrogen recycle 23', which is part of the hydrogen product 23 from a hydrogen purification unit 22 arranged downstream, and then directed to the hydrogenator 10 and the sulfur absorber 12 by a feed gas compressor (not shown). The WGS section 18 includes a high temperature shift unit (HTS unit) and a medium or low temperature shift unit (MTS or LTS unit). These shift units are not shown in the figure. Prior to desulfurization in units 10 and 12, the process may comprise preheating (not shown) the hydrocarbon feed 1, in particular the first shifted synthesis gas from the HTS unit, by indirect heat exchange (i.e. by cooling) with a shifted synthesis gas in a downstream WGS section 18. The desulfurized hydrocarbon feed 5 is then suitably further preheated (not shown) by indirect heat exchange, by means of superheated steam generated from heat recovery in the WGS section 18, in particular the shifted synthesis gas from the HTS unit.

[0189] The hydrocarbon feed 5 is combined with a shifted synthesis gas recycle stream 17'. The shifted synthesis gas recycle stream is a first part of the shifted synthesis gas 17 from the WGS section 18, which has been cooled and dried. In the WGS section 18, for example (not shown) an HTS unit and an LTS unit, and a downstream section for cooling the shifted synthesis gas taken from the LTS unit, and for subsequent separation of process condensate (water), thereby providing a cooled and dried shifted synthesis gas 17. The cooling and drying are carried out in one or more heat exchangers (suitably also air coolers) and a process condensate separator (not shown). From the synthesis gas 17, a first part 17' is diverted as a shifted synthesis gas recycle stream, and a second part is directed to the CO2 removal section 20.

[0190] The shifted synthesis gas recycle 17' may also be combined with the hydrocarbon feed 1 upstream of the feed gas compressor (not shown); in this case, the hydrogen recycle 23' may not be needed. After adding steam 9 and a recycle stream 7' ("short cycle"), the latter being part of the pre-reformed hydrocarbon feed 7, the hydrocarbon feed is directed to the pre-reformer 14 and then to the ATR 16. No preheating of the pre-reformed stream 7 is performed before the ATR 16; in particular, no fired heater is provided to preheat the pre-reformed hydrocarbon feed 7 or any hydrocarbon feed stream 1, 3, 5 upstream of the pre-reformer 14. The pre-reformed hydrocarbon feed 7 is then directed to the ATR 16 together with some steam 9'. The ATR 16 is operated with the addition of an oxygen-containing gas stream 11, for example supplied by an air separation unit (not shown). In the ATR 16, the pre-reformed hydrocarbon feed 7 is converted into a crude synthesis gas (crude synthesis gas) 15, which is then sent to the WGS section 18. From the shifted synthesis gas stream 17 produced from the WGS section 18, a small portion 17' is recycled to the pre-reformer 14, as described above. A second portion of the shifted synthesis gas 17 is subsequently sent to the CO2 removal section 20, as described above. The CO2 removal section separates a CO2-rich stream 19, thereby providing a CO2-depleted synthesis gas 21, which is then fed to a hydrogen purification unit 22, from which a hydrogen product stream 23 and an off-gas stream 25 are produced. Although part of the hydrogen can be recycled as stream 23', the off-gas stream 23 or a portion thereof is not recycled. The CO2-rich stream 19 can be captured and / or utilized according to known techniques, such as carbon capture and utilization (CCU) or carbon capture and storage (CCS) techniques, or a combination thereof (CCUS).

Claims

1. A method for producing synthesis gas from a hydrocarbon feed, comprising the following steps: i) pre-reforming a hydrocarbon feed to produce a pre-reformed hydrocarbon feed; ii) autothermal reforming of the pre-reformed hydrocarbon feed to produce a crude synthesis gas; iii) subjecting the raw synthesis gas to water gas shift to produce shifted synthesis gas as the synthesis gas, and recycling a first portion of the shifted synthesis gas by combining it with the hydrocarbon feed of step i); wherein the first portion of the shifted synthesis gas to be recycled is the shifted synthesis gas from which moisture has been removed in the water separation step.

2. A method according to claim 1, wherein in step iii), the first portion of the shifted synthesis gas accounts for 15% or less, such as 10% or less, such as 2-8% of the volume flow of the shifted synthesis gas.

3. The method according to any one of claims 1-2, wherein the method does not have a primary reforming step requiring heat input, the primary reforming step being any one of steam methane reforming (SMR) and convection reforming.

4. The method according to any one of claims 1 to 3, wherein the method further comprises: Prior to step i), the hydrocarbon feed is desulfurized; wherein step iii) comprises a high temperature shift (HTS) step for producing a first shifted synthesis gas, and optionally a subsequent medium temperature and / or low temperature shift step (MTS and / or LTS) step for producing a shifted synthesis gas; And wherein, before desulfurization, the method further comprises: preheating the hydrocarbon feed by indirect heat exchange with the shifted synthesis gas from step iii), wherein the indirect heat exchange is achieved by cooling the first shifted synthesis gas in one or more heat exchangers; or by indirect heat exchange with the superheated steam generated from heat recovery in step iii), wherein the heat recovery comprises cooling a portion of the first shifted synthesis gas by directing the portion of the first shifted synthesis gas to a steam superheater, thereby generating the superheated steam.

5. The method according to claim 4, wherein after desulfurizing the hydrocarbon feed, the method comprises: The hydrocarbon feed is further preheated by indirect heat exchange with superheated steam generated from heat recovery in step iii), wherein said heat recovery comprises cooling a portion of the first shifted synthesis gas by directing it to a steam superheater to generate said superheated steam.

6. The process according to any one of claims 1 to 5, wherein step i) comprises recycling part of the pre-reformed hydrocarbon feed by combining it with the hydrocarbon feed.

7. The method according to claim 6, wherein the method further comprises: Prior to step i), the hydrocarbon feed is desulfurized and the pre-reformed hydrocarbon feed is combined with the desulfurized, preheated hydrocarbon feed.

8. A method according to any one of claims 1 to 7, wherein the first portion of the shifted synthesis gas that is recycled has more than 70 vol.% H2 and more than 25 vol.% CO2.

9. The method according to any one of claims 1 to 8, further comprising: iv) subjecting a second portion of the shifted syngas to CO2 removal to produce a CO2-depleted shifted syngas; and optionally v) enriching the shifted synthesis gas stream or the CO2-depleted shifted synthesis gas with hydrogen in a hydrogen purification unit to produce a hydrogen product and an off-gas stream; and wherein the off-gas stream is not recycled to any of steps i) to iv).

10. The process according to any one of claims 1 to 9, wherein before the pre-reforming step or before the desulfurization, a hydrocarbon feed is supplied to a feed gas compressor, and: Wherein said recycling in step iii) comprises combining a first portion of said shifted synthesis gas stream with a hydrocarbon feed and then supplying it to a feed gas compressor.

11. The method according to any one of claims 1 to 9, wherein the method further comprises: Prior to step i), the hydrocarbon feed is desulfurized, wherein the recycling in step iii) comprises combining a first portion of the shifted synthesis gas with the desulfurized hydrocarbon feed; wherein the hydrocarbon feed is supplied to a feed gas compressor prior to the pre-reforming step or the desulfurization, and The method further comprises recycling a portion of the CO2-depleted shifted synthesis gas stream or a portion of the hydrogen product to the hydrocarbon feed, which is then supplied to the feed gas compressor.

12. The process according to claim 11, wherein the pre-reforming step i) is carried out in an adiabatic pre-reformer, wherein the inlet temperature of the hydrocarbon feed gas is in the range of 380-430°C; and the autothermal reforming step ii) is carried out in an autothermal reformer (ATR), wherein the inlet temperature of the pre-reformed hydrocarbon feed is in the range of 420-480°C, substantially corresponding to the temperature of the pre-reformed hydrocarbon feed leaving the pre-reformer.

13. The process according to any one of claims 1 to 12, wherein the steam to carbon molar ratio (S / C ratio) in the pre-reforming step i) is 1.0 or less, such as 0.8 or less, such as 0.6 or less, such as 0.

5.

14. The process according to any one of claims 1 to 13, comprising preheating the hydrocarbon feed or the pre-reformed hydrocarbon feed by electrical heating before carrying out the autothermal reforming step ii).

15. A method for producing a hydrogen product from a hydrocarbon feed comprising the steps of: i) desulfurizing and pre-reforming a hydrocarbon feed to produce a pre-reformed hydrocarbon feed; ii) autothermal reforming of the pre-reformed hydrocarbon feed to produce a crude synthesis gas; iii) subjecting the raw synthesis gas stream to a water gas shift to produce a shifted synthesis gas, and dividing the shifted synthesis gas into a first portion and a second portion; iv) removing CO2 from the second portion of the shifted synthesis gas to produce a CO2-depleted shifted synthesis gas; v) enriching the shifted synthesis gas or the CO2-depleted shifted synthesis gas with hydrogen in a hydrogen purification unit to produce a hydrogen product and an off-gas stream; in Prior to the desulfurization and pre-reforming steps, a hydrocarbon feed is supplied to a feed gas compressor, and wherein the method further comprises: - combining a first portion of the shifted synthesis gas with a hydrocarbon feed and then feeding it to a feed gas compressor; and / or - Between said desulphurisation and pre-reforming steps, a first portion of the shifted synthesis gas is combined with a hydrocarbon feed.

16. An apparatus for producing synthesis gas from a hydrocarbon feed, comprising: - a pre-reformer arranged to receive a hydrocarbon feed to produce a pre-reformed hydrocarbon feed; - a feed gas compressor arranged upstream of the pre-reformer for directing the hydrocarbon feed to the pre-reformer; - an autothermal reformer (ATR) arranged to receive a pre-reformed hydrocarbon feed and convert it into a crude synthesis gas; a water-gas shift section (WGS section) arranged to receive the raw synthesis gas from the ATR and to shift it in at least one high temperature shift step (HTS step) so as to provide a shifted synthesis gas as said synthesis gas; wherein the apparatus is devoid of a fired heater for preheating the hydrocarbon feed or preheating the pre-reformed hydrocarbon feed; Therein the apparatus is arranged for feeding a first portion of the shifted synthesis gas to a point upstream of the pre-reformer.

17. The apparatus of claim 16, further comprising: a CO2 removal section arranged to receive a second portion of the shifted syngas from said WGS section and to separate a CO2-rich stream therefrom, thereby providing a CO2-depleted shifted syngas; a hydrogen purification unit arranged to receive a second portion of said shifted synthesis gas or said CO2-depleted shifted synthesis gas from said CO2 removal section and to separate it into a hydrogen product and an off-gas stream; And wherein the apparatus is devoid of ducting and / or exhaust gas recirculation compressor for directing at least a portion of the exhaust gas flow to any of the desulfurization section, pre-reformer, ATR and WGS section.

18. An apparatus according to claim 17, wherein the apparatus is arranged to feed a first portion of the shifted synthesis gas to the inlet of the pre-reformer, and the apparatus is further arranged to feed a portion of the CO2-depleted shifted synthesis gas or a portion of the hydrogen product to the hydrocarbon feed upstream of the feed gas compressor.

19. Apparatus according to any one of claims 16 to 17 arranged to feed a first portion of the shifted synthesis gas to the hydrocarbon feed upstream of a feed gas compressor.

20. The apparatus according to any one of claims 16 to 19, wherein WGS segments include: - a high temperature shift unit (HTS unit), as well as a medium temperature shift unit (MTS unit) and / or a low temperature shift unit (LTS unit); a downstream section comprising one or more heat exchangers for cooling the shifted synthesis gas taken from the MTS and / or LTS unit, and a process condensate separator (PC separator) for separating process condensate from the shifted synthesis gas, thereby providing a cooled and dried shifted synthesis gas; and means for splitting it: feeding a first portion of the shifted synthesis gas upstream of the pre-reformer and optionally also feeding a second portion of the shifted synthesis gas to the CO2 removal section.

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