Method and apparatus for producing pure carbon monoxide and hydrogen

Abstract

A method and apparatus for producing pure carbon monoxide and hydrogen are proposed, which provide raw syngas by steam reforming of hydrocarbons, preferably methane or naphtha, and subsequent multi-stage post-treatment, purification and fractionation of the raw syngas to provide the target products, wherein the material streams obtained as by-products of the process chain are also advantageously utilized. This is achieved according to the invention by providing a recycle compressor, which is arranged to recycle the by-product stream with a plurality of parallel, independently operable compressor stages. This enables recycle streams of different sizes to be fed to the steam reforming unit. In an alternative embodiment, additional recycle streams can be generated, which allow the load on the cryogenic fractionation unit to be artificially increased, thus making the control of the distillation and separation steps contained therein simpler and the operation more stable.

Description

Field of the Invention

[0001] The present invention relates to a method and an apparatus for producing pure carbon monoxide and hydrogen by steam reforming of hydrocarbons, preferably methane or naphtha, to provide raw syngas and subsequent multistage post-treatment, purification and fractionation of the raw syngas to provide the target products, wherein material streams obtained as by-products of the process chain will also be advantageously utilized. Background Art

[0002] Hydrocarbons can react catalytically with steam to provide syngas, i.e., a mixture of hydrogen (H2) and carbon monoxide (CO). As explained in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, Electronic Release 1998, under the keyword "Gas Production", the so-called steam reforming is the most commonly used method for producing syngas, which can then be converted into other important commodity chemicals such as methanol or ammonia. Although different hydrocarbons can be converted, e.g., naphtha, liquefied gas or refinery gas, the steam reforming of methane-containing natural gas is dominant. Other important methods for syngas production are, for example, autothermal reforming (ATR) and partial, non-catalytic (POX) or catalytic oxidation of hydrocarbons.

[0003] After preheating to a temperature of above about 500 °C (e.g., up to 650 °C) in a heat exchanger or a flame heater, the hydrocarbon-steam mixture enters the reforming tubes of a steam reformer after being finally heated to about 800 °C to 950 °C and is converted therein over a reforming catalyst into carbon monoxide and hydrogen. Nickel-based reforming catalysts are common. Although higher hydrocarbons are completely converted into carbon monoxide and hydrogen, in the case of methane, partial conversion usually occurs. The composition of the product gas is determined by the reaction equilibrium; thus, the product gas contains not only carbon monoxide and hydrogen, but also carbon dioxide, unreacted methane and water vapor. For energy optimization or for feedstocks containing higher hydrocarbons, a so-called prereformer for pre-cracking the feedstock can be employed downstream of the preheater. The pre-cracked feedstock is then heated in another heater to the required reforming tube inlet temperature.

[0004] After leaving the reforming furnace, the hot syngas product gas is partially cooled in one or more heat exchangers in indirect heat exchange with process media to be heated. Then, the partially cooled syngas product gas undergoes further conditioning steps depending on the type of desired product or downstream process.

[0005] Further post-treatment of the partially cooled raw syngas produced generally also includes methods for removing further unwanted concomitants, for example by physical or chemical absorption or gas scrubbing. Thus, such methods can be used to safely remove unwanted acidic components (such as carbon dioxide (CO2) and hydrogen sulfide (H2S)) from the raw syngas produced by gasification or reforming of carbonaceous inputs, and also to remove further components (such as carbonyl sulfide (COS), hydrogen cyanide (HCN) or mercaptans (RSH)) from the desired syngas components hydrogen and carbon monoxide to trace levels. A known and frequently used method is the Rectisol process, which involves scrubbing the raw syngas with cold methanol as the absorbent and is also described generally in the above-mentioned literature. Other scrubbing methods employ other scrubbing or absorption media, such as N-methylpyrrolidone (NMP), secondary amines such as diethanolamine, tertiary amines such as methyldiethanolamine (MDEA), polyethylene glycol dialkyl ethers, such as polyethylene glycol dimethyl ether. The carbon dioxide removed in this way can be recycled in whole or in part to syngas production, for example steam reforming, for material utilization and to reduce the H2 / CO molar ratio. This is particularly desirable when carbon monoxide is one of the target products of the process. Equipment operating by this method is hereinafter generally referred to as a carbon dioxide removal unit. The specific process conditions to be employed here, the selection of which is familiar to the person skilled in the art, are hereinafter referred to as carbon dioxide removal conditions.

[0006] Multistage cryogenic gas fractionation (which is also known as a cold box due to the common arrangement of the individual separation stages in a housing insulated from the environment) can be used to remove methane and trace higher hydrocarbons and to separate carbon monoxide and hydrogen. This mainly uses liquid methane or liquid nitrogen to absorb the higher boiling gases, such as carbon monoxide. For example, it is possible to find in the reference book "Industrial Gases Processing", Chapter 5.2.3.6, "Cryogenic Separation Processes", edited by H.-W., WILEY-VCH, Weinheim (2008), detailed information on the methods used. Depending on the composition of the syngas, two different methods are used industrially to separate the raw syngas into H2 and CO components, namely the condensation process or methane scrubbing.

[0007] During condensation, a heat exchanger is used to cool the dry raw syngas to such an extent that the gas phase, i.e., raw hydrogen, can be removed from the CO / methane-rich liquid phase using a separator. The "refrigeration" required for cooling is provided by the raw hydrogen to be heated and the evaporating CO. The hydrogen still dissolved in the liquid phase is removed in a downstream hydrogen stripper. The CO / methane mixture from which H2 has been thus removed is split in a second column by cryogenic distillation to obtain pure CO as the top product and methane as the bottom product. A low-pressure waste gas is produced as a mixture of the top product from the hydrogen stripper and the bottom product from the CO / methane distillation column, which is suitable for use as fuel gas. The raw hydrogen can be further purified in a PSA unit. The condensation method is preferably used for splitting high-pressure syngas rich in CO with a low methane content, such as obtained by partial oxidation of hydrocarbons.

[0008] Hereinafter, a device operating by a cryogenic gas fractionation method is generally referred to as a cryogenic fractionation unit. The specific process conditions to be used herein, which are selected and familiar to those skilled in the art, are hereinafter referred to as cryogenic fractionation conditions.

[0009] For raw syngas from a steam reformer, which has a higher H2 / CO ratio and a higher residual methane content, methane scrubbing is more suitable for obtaining pure CO and raw hydrogen compared to the condensation method. In a first column, i.e., a so-called scrubbing column, most of the hydrogen is removed from the cooled raw syngas by scrubbing off other components. The solvent used is supercooled high-purity liquid methane, which is cooled by the evaporating CO to remove the heat of solution. In a downstream hydrogen stripper, the bottom product from the scrubbing column is removed from the still dissolved hydrogen. The CO / methane bottom product from the hydrogen stripper is split in a downstream CO / methane distillation column to obtain pure CO as the top product and methane as the bottom product. The CO purity at the top of the column is adjusted by the reflux ratio of supercooled pure CO. The excess methane is released at low pressure together with the top product from the hydrogen stripper and is used, for example, as fuel gas.

[0010] To avoid blocking the process stages contained in the cold box due to ice formation, the cold box is usually provided upstream with a dryer and / or an adsorber filled with a suitable adsorbent, such as based on molecular sieves, through which a certain proportion of water and other unwanted trace impurities can be removed.

[0011] The carbon monoxide discharged from the cold box can be provided to consumers as a pure product.

[0012] For the production of pure hydrogen, this is typically followed by the final step of processing the raw hydrogen stream in a pressure swing adsorption (PSA) unit, the basic characteristics of which are listed in the textbook "Gasification", C. Higman and M. van der Burgt, Chapter 8.2.3, "Adsorption systems", Gulf Professional Publishing (2003). Pressure swing adsorption uses molecular sieves as adsorbents in a series of vessels operating in a staggered cycle mode that alternates between an adsorption phase and different regeneration phases. Very high purity can be achieved with about 50 ppm of argon and less than 10 ppm of other impurities.

[0013] U.S. Patent Specification US 8 888 873 B2 discloses by way of example such syngas production and syngas aftertreatment, which includes the following method stages: syngas production - acid gas (CO2) removal - drying and adsorption of destructive components - cryogenic fractionation of the syngas in a cold box. Particular reference is made to Figure 1 and the description of the drawings. This discloses the use of one or more compressors to recycle the CO2-rich stream from the CO2 removal stage and / or the gas stream containing hydrogen, carbon monoxide and / or methane from the cryogenic fractionation to the syngas production stage, thereby allowing for better material utilization.

[0014] U.S. Patent Specification US 9 512 004 B2 likewise discloses a process chain of the type described. This document teaches the use of a recycle compressor to achieve the following different operating modes:

[0015] (a) In a first operating mode, at least part of the carbon dioxide removed from the syngas is mixed with a hydrocarbon-rich input (b),

[0016] (b) In a second operating mode, the residual gas removed in the pressure swing adsorption unit is at least partly mixed with the hydrogen-rich fraction upstream of the pressure swing adsorption unit using a recycle compressor.

[0017] The disadvantage here is that in each case, the recycle compressor can only be used for one of the described operating modes.

[0018] In order to cover a greater capacity range of syngas production equipment, recycle compressors are usually implemented in a multi-stage form, where compressor stages with multiple partial capacities are arranged in parallel. Thus, a configuration of a recycle compressor with, for example, three parallel compressor stages each having 50% of the nominal capacity allows for a capacity range between 50% and 150% and thus a very flexible operation of the syngas production equipment. However, one disadvantage is that, except for operation at 150% of the nominal capacity, one or even two of the parallel compressor stages remain unused, thus forming dead capital.

[0019] Therefore, there is still a need for methods for producing pure carbon monoxide and pure hydrogen that cover a wide range of different production capacities and at the same time achieve an optimal material utilization of the components present in the by-product stream. Summary of the Invention

[0020] Therefore, it is an object of the present invention to provide a method and an apparatus for producing pure carbon monoxide and hydrogen that do not exhibit the disadvantages of the prior art.

[0021] In a first aspect, this object is solved by a method having the features of claim 1 and an apparatus having the features of claim 10. Further embodiments of the present invention are apparent from the dependent claims of the respective categories.

[0022] Steam reforming conditions are known to those skilled in the art from the prior art (such as the documents discussed at the beginning). These are physicochemical conditions under which a measurable, preferably industrially relevant conversion of hydrocarbons into syngas products is achieved. These conditions and the necessary adjustments required for the respective operations will be based on routine experiments. Any specific reaction conditions disclosed herein can be used as a guide, but they should not be considered as limiting the scope of the present invention.

[0023] In the context of the present invention, the division or resolution / separation of a material stream should be understood to mean the generation of at least two sub-streams from an original material stream, where the resolution / separation is related to an intentional change in the material composition of the obtained sub-streams relative to the original material stream, for example by applying a thermal separation process to the original material stream. In contrast, the division of an original material stream is generally not related to a change in the material composition of the obtained sub-streams.

[0024] The enrichment or depletion of a component in a mixture, fraction or material stream should be understood to mean a measure, operation or process step the result of which is an increase (enrichment) or decrease (depletion) in the mole fraction or mass fraction of the component.

[0025] The main part of a fraction, a material stream, etc. should be understood to mean a proportion that is greater in quantity than all other proportions considered separately for each of them. In particular, in the case of a binary mixture or when splitting a fraction into two parts, unless otherwise stated in special cases, this should be understood to mean a proportion greater than 50% by weight.

[0026] An indication that a material stream consists mainly of one component or a group of components should be understood to mean that the mole fraction or mass fraction of this component or group of components is greater in quantity than all other proportions of the other components or groups of components in the material stream considered separately for each of them. In particular, in the case of a binary mixture, this should be understood to mean a proportion greater than 50%. Unless otherwise stated in the specific case, this is based on the mass fraction.

[0027] An indication to supply a material stream directly to a specific method stage or a specific part of a device should be understood to mean introducing the material stream into this method stage or this part of the device without having previously passed through other method stages or parts of the device, except for pure transportation operations and the devices required therefor, such as pipes, valves, pumps, compressors, storage units.

[0028] Unless otherwise stated in individual cases, all pressures are expressed in absolute pressure units (abbreviated as bara) or gauge pressure units (abbreviated as barg).

[0029] The fluid connection between two regions of a device according to the invention should be understood to mean any type of connection that enables a fluid, such as an air stream, to flow from one of the two regions to the other, disregarding any intervening regions or components. In particular, a direct fluid connection should be understood to mean any type of connection that enables a fluid, such as an air stream, to flow directly from one of the two regions to the other, where there are no additional regions or components, except for pure transportation operations and the devices required therefor, such as pipes, valves, pumps, compressors, storage units. An example is a pipe that leads directly from one of the two regions to the other.

[0030] A device should be understood to mean something that enables or facilitates the achievement of an objective. In particular, a device for performing a specific method step should be understood to include all physical items that a person skilled in the art would consider necessary to be able to perform this method step. For example, a person skilled in the art would consider devices for introducing or discharging a material stream to include all conveying and transporting instruments, i.e., for example, pipelines, pumps, compressors, valves, which seem necessary or obvious to the said person skilled in the art for performing this method step based on their knowledge of the art.

[0031] An indication that two or more compressor stages are connected or arranged in parallel shall be understood to mean that the material flow compressed through and within one of these compressor stages does not additionally pass through and is not compressed within one of the other compressor stages, where the two or more compressor stages can operate independently of each other.

[0032] For the purposes of this specification, steam shall be understood to be synonymous with water vapor, unless stated to the contrary in an individual case.

[0033] The present invention is based on the following findings: In the prior art processes known hitherto for the production of pure carbon monoxide and hydrogen from hydrocarbons by steam reforming, difficulties arise in establishing different, in particular significantly different, production capacities. In addition, the material flows produced as by-product streams in the work-up of the raw synthesis gas have not hitherto been optimally utilized. Thus, the stream containing hydrogen and additional combustible components obtained as a by-product in the production of pure hydrogen by PSA has hitherto mainly been thermally utilized as fuel gas for the burners in the steam reforming unit. This also applies to the medium-pressure flash gas stream still containing a considerable proportion of hydrogen and carbon monoxide obtained in cryogenic gas fractionation. In addition, the control of the distillation and separation steps comprised in the cold box is complex when the upstream synthesis gas production plant is to operate at significantly different production capacities, in particular at a lower production capacity.

[0034] The difficulties enumerated are reduced or completely avoided with the present invention. The operation of feeding at least a part of one or more streams selected from the group comprising:

[0035] - the mainly carbon dioxide-containing stream,

[0036] - the methane-containing fractionation gas stream,

[0037] - the flash gas stream containing carbon monoxide and hydrogen,

[0038] into a compressor unit, discharging the compressed first recycle stream from the compressor unit and recycling it, for example, into a steam reforming unit improves the material utilization of components such as hydrogen, carbon oxides, in particular carbon monoxide or methane, present in the recycle stream.

[0039] In addition, the configuration of the method according to the invention or of a device having at least two compressor stages in parallel significantly increases the adjustable production capacity span. Thus, a recycle compressor configured with three compressor stages each having 50% of the nominal capacity allows a capacity range between 50% (partial load operation) and 150% (full load operation) and thus a very flexible operation of the synthesis gas production plant. In contrast, an embodiment of a recycle compressor with two compressor stages each having 50% of the nominal capacity develops a capacity range between 50% (partial load operation) and 100% (full load operation).

[0040] In order to advantageously utilize compressor stages that are not required in every case during partial load operation, the present invention provides for using these compressor stages to recycle one or more by-product streams generated during the post-treatment of raw synthesis gas to a drying unit arranged upstream of a cryogenic fractionation unit. This results in an artificial load on the cryogenic fractionation unit during partial load operation, thereby allowing for simpler control and more stable operation of the distillation and separation steps contained in the cold box. For this purpose, two or more compressor stages for different purposes are advantageously separated from each other in an airtight manner, so that there is no direct fluid connection between them by means of valves, blind flanges or similar devices being provided therebetween. Accordingly, the corresponding material streams remain separate to avoid unwanted mixing, which would lead to, for example, entrainment of carbon dioxide into the cryogenic fractionation unit, which would cause blockages therein by forming dry ice. Description of the Drawings

[0041] Figure 1 is a first example of a method / device for producing pure carbon monoxide and hydrogen according to the present invention.

[0042] Figure 2 is a second example of a method / device for producing pure carbon monoxide and hydrogen according to the present invention. Detailed Description

[0043] A second aspect of the method according to the present invention is characterized in that at least a part of the compressed first recycle stream is recycled to the steam reforming unit, introduced therein and at least partially converted under steam reforming conditions. In this way, valuable products present in these streams, such as hydrogen, carbon oxides, in particular carbon monoxide or methane, are utilized materially. This results in a reduction in the supply of input stream hydrocarbons for the same production capacity of pure carbon monoxide and hydrogen, thereby generating savings.

[0044] A third aspect of the method according to the present invention is characterized in that at least a part of the mainly carbon dioxide-containing stream is supplied to a first compressor stage and compressed, and the compressed stream is recycled to the steam reforming unit, introduced therein and at least partially converted under steam reforming conditions. This enables the carbon dioxide present in the stream to be utilized materially, thereby reducing the supply of hydrocarbons in the input stream for the same production capacity of carbon monoxide and hydrogen. This is particularly important in the case of a mainly carbon dioxide-containing stream, since it cannot otherwise be used as a fuel gas, for example. In addition, the flexibility of the method is increased with respect to the ratio of the target products carbon monoxide and hydrogen produced: with a higher carbon dioxide recycle, proportionally more carbon monoxide is produced in the product.

[0045] A fourth aspect of the method according to the invention is characterized in that at least a part of the fractionation gas stream containing methane is supplied to the first compressor stage and compressed, and the compressed stream is recycled to the steam reforming unit, introduced therein and at least partially converted under steam reforming conditions. This aspect of the method according to the invention also results in a saving of the input stream hydrocarbon at the same production capacity of pure carbon monoxide and hydrogen.

[0046] A fifth aspect of the method according to the invention is characterized in that at least a part of the flash gas stream containing carbon monoxide and hydrogen is supplied to a second compressor stage and compressed, and the compressed stream is recycled to the drying unit and introduced therein, wherein the second compressor stage is not directly fluidly connected to the first compressor stage. This especially results in an artificial load on the cryogenic fractionation unit during partial load operation, thus allowing for simpler control and more stable operation of the distillation and separation steps comprised in the cold box. In contrast, the first parallel compressor stage can continue to be used for recycling the material stream to the steam reforming unit, thus resulting in the saving of the input stream hydrocarbon as described.

[0047] A sixth aspect of the method according to the invention is characterized in that at least a part of the pure carbon monoxide product gas stream is supplied to the second compressor stage and compressed, and the compressed stream is recycled to the drying unit and introduced therein, wherein the second compressor stage is not directly fluidly connected to the first compressor stage. This also especially results in an artificial load on the cryogenic fractionation unit during partial load operation, thus allowing for simpler control and more stable operation of the distillation and separation steps comprised in the cold box. In contrast, the first parallel compressor stage can continue to be used for recycling the material stream to the steam reforming unit, thus resulting in the saving of the input stream hydrocarbon as described. A partial, preferably time-limited consumption of the pure carbon monoxide product gas stream for said purpose is also advantageous for ensuring the operational stability of the cryogenic fractionation unit. This may be the case especially during an operational interruption or transition between different operational states, which results in a significant reduction of the input stream entering the cryogenic fractionation unit.

[0048] A seventh aspect of the method according to the invention is characterized in that at least a part of the PSA waste gas stream is supplied to the second compressor stage and compressed, and the compressed stream is recycled to the drying unit and introduced therein, wherein the second compressor stage is not directly fluidly connected to the first compressor stage. This also especially results in an artificial load on the cryogenic fractionation unit during partial load operation, thus allowing for simpler control and more stable operation of the distillation and separation steps comprised in the cold box, while the first parallel compressor stage can continue to be used for recycling the material stream to the steam reforming unit.

[0049] According to an eighth aspect of the method according to the invention, at least a part of the mainly carbon dioxide-containing stream and at least a part of the fractionated methane-containing gas stream are supplied to a first compressor stage and compressed, and the compressed stream is recycled to the steam reforming unit, introduced therein and at least partially converted under steam reforming conditions, and is characterized in that at least a part of the flash gas stream containing carbon monoxide and hydrogen, at least a part of the pure carbon monoxide product stream, and at least a part of the PSA waste gas stream are supplied to a second compressor stage and compressed, and the compressed stream is recycled to the drying unit and introduced therein, wherein the second compressor stage is not directly fluid-connected to the first compressor stage. This also results, in particular during partial load operation, in an artificial load on the cryogenic fractionation unit, thereby allowing for simpler control and more stable operation of the distillation and separation steps comprised in the cold box, while the first parallel compressor stage can continue to be used for recycling material streams to the steam reforming unit. The combinatorial diversity of the individual said material streams, which are sub-streams of the recycle streams leading on the one hand to the steam reforming unit and on the other hand to the cryogenic fractionation unit (which is possible in this embodiment), allows for a particularly fine compensation of changes between different load states of the production plant without subjecting the individual method stages to particularly high loads, since all the individual material streams entering or leaving them are used as recycle streams, thereby compromising the constant operation of these method stages.

[0050] According to a ninth aspect of the method according to the invention, at least a part of the hydrogen-rich gas stream is used to regenerate the drying medium arranged in the drying unit before it is passed to the pressure swing adsorption unit. This enables a high availability of the regenerated adsorption / drying medium in the drying unit. This is particularly applicable when the drying unit is configured with a plurality of individual groups operating in parallel, where at least one group is in the load mode at any given time and at least one additional group is in the regeneration mode at any given time.

[0051] In a further aspect, the device according to the invention is characterized in that the device comprises means enabling at least a part of the compressed first recycle stream to be recycled to the steam reforming unit and introduced therein. The advantages of this aspect of the device according to the invention correspond to the advantages of the second aspect of the method according to the invention.

[0052] In a further aspect, the device according to the invention is characterized in that the device comprises means enabling at least a part of the mainly carbon dioxide-containing stream to be supplied to a first compressor stage and compressed, and the compressed stream to be recycled to the steam reforming unit and introduced therein. The advantages of this aspect of the device according to the invention correspond to the advantages of the third aspect of the method according to the invention.

[0053] In another aspect, the device according to the invention is characterized in that the device comprises means enabling at least a portion of the fractionation gas stream containing methane to be supplied to the first compressor stage and compressed, and the compressed stream to be recycled to and introduced into the steam reforming unit. The advantages of this aspect of the device according to the invention correspond to the advantages of the fourth aspect of the method according to the invention.

[0054] In another aspect, the device according to the invention is characterized in that the device comprises means enabling at least a portion of the flash gas stream containing carbon monoxide and hydrogen to be supplied to a second compressor stage and compressed, and the compressed stream to be recycled to and introduced into the drying unit, wherein the second compressor stage is not in direct fluid connection with the first compressor stage. The advantages of this aspect of the device according to the invention correspond to the advantages of the fifth aspect of the method according to the invention.

[0055] In another aspect, the device according to the invention is characterized in that the device comprises means enabling at least a portion of the pure carbon monoxide product gas stream to be supplied to the second compressor stage and compressed, and the compressed stream to be recycled to and introduced into the drying unit, wherein the second compressor stage is not in direct fluid connection with the first compressor stage. The advantages of this aspect of the device according to the invention correspond to the advantages of the sixth aspect of the method according to the invention.

[0056] In another aspect, the device according to the invention is characterized in that the device comprises means enabling at least a portion of the PSA waste gas stream to be supplied to the second compressor stage and compressed, and the compressed stream to be recycled to and introduced into the drying unit, wherein the second compressor stage is not in direct fluid connection with the first compressor stage. The advantages of this aspect of the device according to the invention correspond to the advantages of the seventh aspect of the method according to the invention.

[0057] In another aspect, the device according to the invention is characterized in that the device comprises means enabling at least a portion of the stream mainly containing carbon dioxide and at least a portion of the fractionation gas stream containing methane to be supplied to the first compressor stage and compressed, and the compressed stream to be recycled to and introduced into the steam reforming unit, and at least a portion of the flash gas stream containing carbon monoxide and hydrogen and at least a portion of the pure carbon monoxide product gas stream and at least a portion of the PSA waste gas stream to be supplied to the second compressor stage and compressed, and the compressed stream to be recycled to and introduced into the drying unit, wherein the second compressor stage is not in direct fluid connection with the first compressor stage. The advantages of this aspect of the device according to the invention correspond to the advantages of the eighth aspect of the method according to the invention.

[0058] Working Examples

[0059] Other developments, advantages and possible uses of the present invention can also be derived from the following description of working examples and the drawings. All features described and / or depicted, either alone or in any combination, form the present invention, regardless of how they are combined in the claims or in the reverse references therein.

[0060] In these figures:

[0061] Figure 1 is a first example of a method / device for producing pure carbon monoxide and hydrogen according to the present invention,

[0062] Figure 2 is a second example of a method / device for producing pure carbon monoxide and hydrogen according to the present invention.

[0063] In Figure 1 In the embodiment of the present invention of the method / device for producing pure carbon monoxide and hydrogen shown, an input stream containing hydrocarbons, preferably methane or naphtha, is supplied via conduit 11 to a steam reforming unit 10 and introduced into the steam reforming unit together with a steam stream supplied via conduit 14. A sub-stream of the hydrocarbon-containing input stream is transferred as fuel gas via conduits 12 and 13 to a burner (not shown) of the steam reforming unit and burned therein together with an air stream supplied via conduit 15 to heat the reforming tubes filled with reforming catalyst arranged in the steam reforming unit.

[0064] The steam reforming unit at least partially converts the hydrocarbons present in the input stream with steam under steam reforming conditions in the reforming tubes filled with reforming catalyst, thereby obtaining a raw synthesis gas stream containing carbon monoxide, hydrogen, water, carbon dioxide and methane. The synthesis gas stream is discharged from the steam reforming unit via conduit 16 and introduced into a carbon dioxide removal unit 20. This can be configured according to methods known per se for carbon dioxide removal, such as using physical or chemical absorption or gas scrubbing. A known and frequently used method is the Rectisol method, which includes scrubbing the raw synthesis gas with cryogenic methanol as an absorbent and is also generally described in the above-mentioned literature. Other scrubbing methods employ other scrubbing or absorption media, such as N-methylpyrrolidone (NMP), secondary amines such as diethanolamine, tertiary amines such as methyldiethanolamine (MDEA), polyethylene glycol dialkyl ethers, such as polyethylene glycol dimethyl ether. Since the input stream supplied to the steam reforming unit is usually already desulfurized, the carbon dioxide removal unit can be configured / optimized to remove CO2.

[0065] The carbon dioxide - lean synthesis gas stream is discharged from the carbon dioxide removal unit via conduit 21 and introduced into the drying unit 30. The stream mainly containing carbon dioxide is discharged from the carbon dioxide removal unit via conduit 22 and recycled to the inlet of the steam reforming unit via conduit 23, two - stage compressor units 60a, 60b, and conduits 61 and 11.

[0066] In the drying unit, a certain proportion of water and other unwanted trace impurities (such as remaining trace amounts of CO2) are removed from the carbon dioxide - lean synthesis gas stream by adsorption on a molecular - sieve - based adsorbent, because these would cause ice / dry - ice formation during subsequent cryogenic fractionation, thus clogging the equipment there. This provides a dried synthesis gas stream, which is discharged from the drying unit via conduit 31 and introduced into the multi - stage cryogenic fractionation unit 40, which is configured as a methane wash in this embodiment. The said equipment / method stage is housed in a common housing filled with insulating material, i.e., a so - called cold box.

[0067] In the cryogenic fractionation unit, the first tower, i.e., the so - called wash tower, removes most of the hydrogen from the cooled raw synthesis gas by washing out other components. This provides a hydrogen - rich gas stream, which is discharged via conduit 41. The solvent used is super - cooled high - purity liquid methane, which is cooled by evaporating CO to remove the heat of solution. In the downstream hydrogen stripper, the still - dissolved hydrogen is removed from the bottom product of the wash tower to obtain a flashed gas stream containing carbon monoxide and hydrogen as the top product, which is discharged via conduit 43. The CO / methane bottom product from the hydrogen stripper is split in the downstream CO / methane distillation tower to obtain a pure carbon monoxide product gas stream as the top product, which is discharged from the process via conduit 46 and sent for storage, treatment, or further processing (not shown). The methane obtained as the bottom product from the CO / methane distillation tower is discharged from the cryogenic fractionation unit as a fractionated gas stream containing methane via conduit 44 and recycled to the inlet of the steam reforming unit via conduits 22 and 23, two - stage compressor units 60a, 60b, and conduits 61 and 11.

[0068] The hydrogen - rich gas stream is discharged from the cryogenic fractionation unit via conduit 41 and introduced into the pressure swing adsorption unit 50. Prior to this, the hydrogen - rich gas stream is used to regenerate the adsorbent used in the drying unit.

[0069] The pressure swing adsorption unit provides a pure hydrogen product gas stream which is discharged from the process via conduit 51 and sent for storage, treatment or further processing (not shown). A PSA waste gas stream is also obtained which still contains combustible components such as methane. Said stream is discharged from the pressure swing adsorption unit via conduit 52 and can be sent for subsequent storage, treatment or further processing. Due to its calorific value, in this embodiment it is used as a fuel gas stream and is supplied as another fuel gas stream to the burner (not shown) of the steam reforming unit via conduits 52 and 13.

[0070] According to the invention, one or more or all of the following material streams:

[0071] - a stream mainly containing carbon dioxide, conduit 22

[0072] - a fractionation gas stream containing methane, conduit 44,

[0073] - a flash gas stream containing carbon monoxide and hydrogen, conduit 43,

[0074] are introduced into a compressor unit which in this embodiment comprises two parallel compressor stages 60a, 60b, wherein at least a part of the one or more streams is introduced into one or two of the compressor stages. This enables different load states / capacities of the method / equipment to be achieved. Thus, the recycle compressor is configured as a compressor unit with two parallel compressor stages each having a nominal capacity of 50%, allowing a capacity range between 50% (partial load operation) and 100% (full load operation) and thus a very flexible operation of the syngas production plant.

[0075] In this way, a compressed first recycle stream is obtained which is discharged from the compressor unit via conduit 61 and, in Figure 1 the exemplary embodiment shown, at least partly, preferably mainly, most preferably completely, is recycled via conduits 61 and 11 to the steam reforming unit and introduced therein. This improves the material utilization of components such as hydrogen, carbon oxides or methane present in the recycle stream. According to the methods of the prior art, these components would mainly be thermally utilized, for example as another fuel gas or heating gas for the burner of the steam reforming unit.

[0076] It is possible to Figure 1The exemplary embodiments are modified such that in each case at least a portion of the fractionated methane-containing gas stream, conduit 44 and / or at least a portion of the flashed gas stream containing carbon monoxide and hydrogen, conduit 43, is supplied via conduit 13 as additional fuel gas or heating gas via a connecting conduit (not shown) to the burner of the steam reforming unit. This further increases the flexibility of the method during a specific operating state / load state or during the transition between two different operating states, where then it is temporarily accepted that components such as hydrogen, carbon oxides or methane present in the recycle stream are also or mainly thermally utilized rather than materially utilized.

[0077] In Figure 2 Another inventive embodiment of the method / device for producing pure carbon monoxide and hydrogen as shown therein, the compressor unit also includes two compressor stages 60a, 60b in parallel. However, these two compressor stages are now flow-separated from each other by suitable cut-off means (such as Figure 2 the shut-off valve as shown therein) and thus are not directly fluidly connected to each other. Compressor stage 60a is supplied via conduits 22 and 23 with the mainly carbon dioxide-containing stream from the carbon dioxide removal unit and via conduits 44 and 23 with the fractionated methane-containing gas stream, and the streams are also compressed therein, as in the case of Figure 1 the working example of

[0078] Components such as hydrogen, carbon oxides or methane present in these recycle streams are thus continued to be materially utilized to increase the yield of the target components pure carbon monoxide and hydrogen.

[0079] In contrast, compressor stage 60b is supplied via conduit 43 with at least a portion of the flashed gas stream containing carbon monoxide and hydrogen and / or via conduits 45 and 43 with at least a portion of the pure carbon monoxide product stream and / or via conduits 53 and 43 with at least a portion of the PSA waste gas stream. In principle, any alternative or additive combination of the above three streams is possible. Advantageously, especially during partial load operation, the compressor stage that is not required in each case is used to recycle one or more of the above material streams to the drying unit arranged upstream of the low-temperature fractionation unit. This results in an artificial load on the low-temperature fractionation unit during partial load operation, thereby allowing for simpler control and more stable operation of the distillation and separation steps contained in the cold box. For this purpose, two or more compressor stages for different purposes are advantageously hermetically separated from each other, so that there is no direct fluid connection between them by means of valves, blind flanges or similar devices being provided between them. Thus, the corresponding material streams remain separated to avoid unwanted mixing, which would lead to, for example, entrainment of carbon dioxide into the low-temperature fractionation unit, which would cause blockages therein by forming dry ice.

[0079] It is also possible to further Figure 2The exemplary embodiments are modified such that in each case at least a portion of the fractionation gas stream containing methane, at least a portion of the flash gas stream containing carbon monoxide and hydrogen in conduit 44, and / or at least a portion of the PSA waste gas stream is supplied via conduit 13 as additional fuel gas or heating gas to the burner of the steam reforming unit via a connecting conduit (not shown). This further increases the flexibility of the method during specific operating states / load states or during transitions between two different operating states, where it is then temporarily accepted that components present in the recycle stream such as hydrogen, carbon oxides especially carbon monoxide or methane are also or mainly thermally utilized rather than materially utilized.

[0080] Depending on the required production capacity of the plant, it is possible to switch between them by closing the conduit paths of conduits 53 and 62 via suitable shut-off devices (not shown). Figure 1 and Figure 2 the two working examples shown. Additionally, the flow separation between the two compressor stages 60a, 60b can optionally be aborted by opening the valves shown. Among the advantages of the method / corresponding plant according to the invention is also the option of such switching between different working examples / operating modes with low plant complexity.

[0081] List of reference numerals

[0082]

[10] Steam reforming unit

[0083]

[11] -

[16] Conduits

[0084]

[20] Carbon dioxide removal unit

[0085]

[21] -

[23] Conduits

[0086]

[30] Drying unit

[0087]

[31] Conduits

[0088]

[40] Cryogenic fractionation unit

[0089]

[41] -

[46] Conduits

[0090]

[50] Pressure swing adsorption unit

[0091]

[51] -

[53] Conduits

[0092] [60a], [60b] Compressor stages

[0093]

[61] -

[62] Conduits

Claims

1. A method for producing pure carbon monoxide and hydrogen from a gaseous or vapor input stream containing hydrocarbons, the method comprising the following steps: (a) Introduce a hydrocarbon-containing input stream and a steam stream into a steam reforming unit, and at least partially convert the hydrocarbons present in the input stream with steam under steam reforming conditions to provide a raw synthesis gas stream containing carbon monoxide, hydrogen, water, carbon dioxide, and methane. (b) Discharge the raw synthesis gas stream from the steam reforming unit and introduce it into a carbon dioxide removal unit. (c) Split the raw synthesis gas stream into a carbon dioxide-rich stream and a carbon dioxide-lean synthesis gas stream under carbon dioxide removal conditions in the carbon dioxide removal unit, and discharge these two streams from the carbon dioxide removal unit. (d) Introduce the carbon dioxide-lean synthesis gas stream into a drying unit and discharge a water-lean dried synthesis gas stream from the drying unit. (e) Introduce the dried synthesis gas stream into a cryogenic fractionation unit and multi-stage split the dried synthesis gas stream into a pure carbon monoxide product gas stream, a hydrogen-rich gas stream, a fractionation gas stream containing methane, and a flash gas stream containing carbon monoxide and hydrogen under cryogenic fractionation conditions, and discharge these gas streams obtained from the multi-stage split from the cryogenic fractionation unit. (f) Supply the hydrogen-rich gas stream to a pressure swing adsorption unit (PSA), and split the hydrogen-rich gas stream into a pure hydrogen product gas stream and a PSA waste gas stream in the pressure swing adsorption unit, and discharge these two streams from the pressure swing adsorption unit. (g) At least a portion of one or more streams selected from the group consisting of: - the carbon dioxide-rich stream, - the fractionation gas stream containing methane, - the flash gas stream containing carbon monoxide and hydrogen, is supplied to a compressor unit including at least two parallel compressor stages, wherein at least a portion of the one or more streams is introduced into one or more of these compressor stages. (h) Discharge a compressed first recycle stream from the compressor unit. wherein the compressor stages are used to recycle one or more by-product streams generated during the post-treatment of the raw synthesis gas to a drying unit arranged upstream of the cryogenic fractionation unit, and the compressor stages for different purposes are hermetically separated from each other.

2. The method according to claim 1, characterized in that, Recycle at least a portion of the compressed first recycle stream to the steam reforming unit, introduce it therein and at least partially convert it under steam reforming conditions.

3. The method according to claim 1 or 2, characterized in that, Supply at least a portion of the carbon dioxide-rich stream to the first compressor stage and compress it, and recycle the compressed stream to the steam reforming unit, introduce it therein and at least partially convert it under steam reforming conditions.

4. The method according to claim 1 or 2, characterized in that, Supply at least a portion of the fractionation gas stream containing methane to the first compressor stage and compress it, and recycle the compressed stream to the steam reforming unit, introduce it therein and at least partially convert it under steam reforming conditions.

5. The method according to claim 1 or 2, characterized in that, Supply at least a portion of the flash gas stream containing carbon monoxide and hydrogen to the second compressor stage and compress it, and recycle the compressed stream to the drying unit and introduce it therein, wherein the second compressor stage is not directly fluidly connected to the first compressor stage.

6. The method according to claim 1 or 2, characterized in that, Supply at least a portion of the pure carbon monoxide product gas stream to the second compressor stage and compress it, and recycle the compressed stream to the drying unit and introduce it therein, wherein the second compressor stage is not directly fluidly connected to the first compressor stage.

7. The method according to claim 1 or 2, characterized in that, At least a portion of the PSA waste gas stream is supplied to the second compressor stage and compressed, and the compressed stream is recycled to and introduced into the drying unit, wherein the second compressor stage is not directly fluidly connected to the first compressor stage.

8. The method according to claim 1 or 2, characterized in that, At least a portion of the mainly carbon dioxide-containing stream and at least a portion of the methane-containing fractionation gas stream are supplied to the first compressor stage and compressed, and the compressed stream is recycled to the steam reforming unit, introduced therein and at least partially converted under steam reforming conditions, and is characterized in that at least a portion of the flash gas stream containing carbon monoxide and hydrogen, at least a portion of the pure carbon monoxide product gas stream, and at least a portion of the PSA waste gas stream are supplied to the second compressor stage and compressed, and the compressed stream is recycled to and introduced into the drying unit, wherein the second compressor stage is not directly fluidly connected to the first compressor stage.

9. The method according to claim 1 or 2, characterized in that, At least a portion of the hydrogen-rich gas stream is used to regenerate the drying medium arranged in the drying unit before being transferred to the pressure swing adsorption unit.

10. An apparatus for producing pure carbon monoxide and hydrogen from a gaseous or vapor input stream containing hydrocarbons, the apparatus comprising the following components and parts of the apparatus: (a) A steam reforming unit for introducing the hydrocarbon-containing input stream and a steam stream into a device in the steam reforming unit, (b) A device for discharging a raw synthesis gas stream from the steam reforming unit, a carbon dioxide removal unit and a device for introducing the raw synthesis gas stream into the carbon dioxide removal unit, (c) means for discharging a carbon dioxide-rich stream and a carbon dioxide-lean synthesis gas stream from the carbon dioxide removal unit, (d) a drying unit, means for introducing the carbon dioxide-lean synthesis gas stream into the drying unit, means for discharging a water-lean dried synthesis gas stream from the drying unit, (e) a cryogenic fractionation unit comprising a plurality of separation stages, means for introducing the dried synthesis gas stream into the cryogenic fractionation unit, means for discharging a pure carbon monoxide product stream, a hydrogen-rich gas stream, a fractionation gas stream containing methane, and a flash gas stream containing carbon monoxide and hydrogen from the cryogenic fractionation unit, (f) a pressure swing adsorption unit (PSA), means for supplying the hydrogen-rich gas stream to the pressure swing adsorption unit, means for discharging a pure hydrogen product stream and a PSA waste gas stream from the pressure swing adsorption unit, (g) a compressor unit comprising at least two parallel compressor stages, means for supplying at least a part of one or more streams selected from the group consisting of: - the carbon dioxide-rich stream, - the fractionation gas stream containing methane, - the flash gas stream containing carbon monoxide and hydrogen, to the compressor unit, wherein the means for supplying is configured such that at least a part of the one or more streams can be introduced into one or more of these compressor stages, (h) means for discharging a compressed first recycle stream from the compressor unit, wherein the compressor stages are used to recycle one or more by-product streams generated during the post-treatment of the raw synthesis gas to a drying unit arranged upstream of the cryogenic fractionation unit, and the compressor stages for different purposes are hermetically separated from each other.

11. The apparatus according to claim 10, characterized in that The apparatus includes means enabling at least a portion of the compressed first recycle stream to be recycled to and introduced into the steam reforming unit.

12. The apparatus according to claim 10 or 11, characterized in that The apparatus includes means enabling at least a portion of the mainly carbon dioxide-containing stream to be supplied to the first compressor stage and compressed, and the compressed stream to be recycled to and introduced into the steam reforming unit.

13. The apparatus according to claim 10 or 11, characterized in that The apparatus includes means enabling at least a portion of the methane-containing fractionation gas stream to be supplied to the first compressor stage and compressed, and the compressed stream to be recycled to and introduced into the steam reforming unit.

14. The apparatus according to claim 10 or 11, characterized in that The apparatus includes means enabling at least a portion of the flash gas stream containing carbon monoxide and hydrogen to be supplied to the second compressor stage and compressed, and the compressed stream to be recycled to and introduced into the drying unit, wherein the second compressor stage is not directly fluidly connected to the first compressor stage.

15. The apparatus according to claim 10 or 11, characterized in that The apparatus includes means enabling at least a portion of the pure carbon monoxide product gas stream to be supplied to the second compressor stage and compressed, and the compressed stream to be recycled to and introduced into the drying unit, wherein the second compressor stage is not directly fluidly connected to the first compressor stage.

16. The apparatus according to claim 10 or 11, characterized in that The apparatus includes means enabling at least a portion of the PSA waste gas stream to be supplied to the second compressor stage and compressed, and the compressed stream to be recycled to and introduced into the drying unit, wherein the second compressor stage is not directly fluidly connected to the first compressor stage.

17. The device according to claim 10 or 11, characterized in that, The device comprises the following means which enable at least a part of the mainly carbon dioxide-containing stream and at least a part of the fractionation gas stream containing methane to be supplied to a first compressor stage and compressed, and the compressed stream to be recycled to and introduced into the steam reforming unit, and at least a part of the flash gas stream containing carbon monoxide and hydrogen, at least a part of the pure carbon monoxide product stream and at least a part of the PSA waste gas stream to be supplied to a second compressor stage and compressed, and the compressed stream to be recycled to and introduced into the drying unit, wherein the second compressor stage is not in direct fluid connection with the first compressor stage.

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