Production of synthesis gas by steam methane reforming

Abstract

The present invention relates to a synthesis gas plant for producing synthesis gas, wherein the synthesis gas plant comprises a reforming section, which is arranged to receive the feed gas and provide a combined synthesis gas, wherein the reforming section comprises an electrically heated reforming reactor, a combustion reforming reactor and an optional third reforming reactor. The reforming section is arranged to output a combined synthesis gas. An optional post-processing unit downstream of the reforming section is arranged to receive the combined synthesis gas flow and provide a post-processed synthesis gas flow. A gas separation unit is arranged to separate the combined synthesis gas flow or the post-processed synthesis gas flow into a condensate, a product synthesis gas and an exhaust gas. At least a portion of the exhaust gas is recycled from the gas separation unit to the one or more burners. The present invention also relates to a method for producing synthesis gas from a feed gas containing hydrocarbons.

Description

Technical Field

[0001] The present invention relates to a synthesis gas plant and a method for producing synthesis gas by subjecting a feed gas comprising hydrocarbons to steam methane reforming. In particular, the present invention relates to a synthesis gas plant and a method for producing hydrogen, wherein the steam methane reforming is carried out in two parallel reforming reactors. Background of the Invention

[0003] Combustion reforming reactors for steam methane reforming, such as combustion steam methane reformers or combustion convection reformers, typically use large amounts of fuel to provide heat for the steam methane reforming reaction. In the case of a combustion steam methane reformer (SMR), the fuel is directly input to the combustion side of the SMR and burned to provide radiant heat to the tubes of the SMR, while excess heat in the flue gas on the combustion side of the SMR is typically used in the waste heat section of the SMR. In the case of a convection reformer or convection reforming reactor, the fuel is directed to a burner that produces a hot flue gas stream. The housing forms a convection channel or convection chamber that allows the flue gas from the burner to flow through the tubes of the convection reformer that contain the catalyst.

[0004] Steam reforming reactions are highly endothermic. High temperatures of over 800-850°C are usually required to achieve acceptable conversion of the methane in the feed. Typically, an SMR consists of a number of tubes placed in a furnace, which are filled with catalyst pellets. The tubes are typically 10-13 meters long and have an inner diameter of between 80 and 160 mm. Burners placed in the furnace provide the required heat for the reaction by burning fuel gas. Inner tube surface 80,000-90,000 kcal / h / m 2 It is not uncommon to find a maximum average heat flux of . Due to mechanical limitations, there is a general limit to the heat flux that can be obtained, so the capacity is increased by increasing the number of tubes and the furnace size. More details of SMR-type reforming reactors can be found in the art, for example, "Synthesis gas production for FT synthesis"; Chapter 4, p. 258-352, 2004. As used herein, the abbreviation "SMR" is intended to mean an externally fired tubular steam methane reformer as described above.

[0005] The fuel for these combustion processes is typically a mixture of exhaust gas from the process downstream of the reformer and input natural gas or other suitable hydrocarbon.

[0006] It is an object of the present invention to provide an alternative configuration of a synthesis gas plant for producing synthesis gas.

[0007] Another object of the present invention is to provide a system and method for producing synthesis gas by steam reforming, wherein the overall energy consumption is reduced compared to a system having a single fired reforming reactor, such as a tubular steam methane reformer or a convection reformer.

[0008] Another object of the invention is to provide an apparatus and a method wherein the capacity of an existing reforming section can be increased.Herein, the term "reforming section" is intended to denote the section of the apparatus where reforming of hydrocarbons takes place, ie a section comprising one or more reforming reactors.

[0009] Furthermore, it is an object of the present invention to provide a synthesis gas plant and a process in which carbon dioxide and other climate-damaging emissions, such as NO, are significantly reduced by minimizing the amount of hydrocarbons that provide heat for the reforming reaction. x or SO x total emissions. Summary of the invention

[0010] In the following, reference is made to embodiments of the present invention. However, it should be understood that the present invention is not limited to the specifically described embodiments. On the contrary, any combination of the following features and elements, whether or not related to different embodiments, may be considered to implement and practice the present invention.

[0011] One aspect of the present invention relates to a synthesis gas plant for producing synthesis gas, the synthesis gas plant comprising:

[0012] a reforming section arranged to receive a feed gas and to provide a combined synthesis gas, wherein the reforming section comprises:

[0013] - an electrically heated reforming reactor containing a first catalyst, said electrically heated reforming reactor being arranged to receive a first portion of said feed gas comprising hydrocarbons and to produce a first synthesis gas stream,

[0014] a combustion reforming reactor connected in parallel with the electrically heated reforming reactor, the combustion reforming reactor comprising one or more tubes containing a second catalyst, the combustion reforming reactor further comprising one or more burners for providing heat to the one or more tubes; the one or more tubes being arranged to receive a second portion of the feed gas comprising hydrocarbons and output a second synthesis gas stream, wherein the reforming section is arranged to output a combined synthesis gas stream comprising the first and / or second synthesis gas stream or a portion thereof,

[0015] - an optional post-treatment unit downstream of the reforming section, wherein the optional post-treatment unit is arranged to receive the combined synthesis gas stream and to provide a post-treated synthesis gas stream,

[0016] a gas separation unit arranged to separate said combined synthesis gas stream or said post-treated synthesis gas stream into at least a condensate, a product synthesis gas and an off-gas, and

[0017] - means for recirculating at least part of said exhaust gases from said gas separation unit to said one or more burners.

[0018] The synthesis gas plant of the present invention provides the concept of obtaining synergy between the operation of an electrically heated reforming reactor and a combustion reforming reactor. By placing an electrically heated reforming reactor in parallel with another reforming reactor, the two reforming reactors can use the same preheating and pretreatment system and the same product gas separation together. In addition, by allowing the partial reforming reaction to be carried out in the electrically heated reforming reactor, the input fuel to the combustion reforming reactor can be reduced / minimized. In addition, by recycling the exhaust gas from the gas separation unit back to one or more burners of the combustion reforming reactor, the use of hydrocarbons in the feed gas can be maximized on the process side, and the direct use of such hydrocarbons on the combustion side of the combustion reforming reactor can be minimized. Therefore, for a given output of the combined synthesis gas from the reforming section, the total consumption of hydrocarbons is minimized.

[0019] The synthesis gas plant can be balanced so that the operation of one or more burners is adjusted to be driven mainly or even completely by the heat provided by the combustion of recycled exhaust gas. A typical combustion reforming reactor uses a fuel feedstock for the burner, which is usually composed of part of the recycled exhaust gas and part of a dedicated fuel feedstock such as natural gas. The heat generated by the recycled exhaust gas and the dedicated fuel feedstock determines the outlet temperature of the synthesis gas produced in the combustion reforming reactor, and therefore determines the methane conversion rate. For example, the burner is driven by about 90% by volume of recycled exhaust gas and about 10% by volume of natural gas. Flow control of the fuel from the dedicated hydrocarbon feedstock allows active control of the burner because the flow can be increased or decreased to control the desired temperature. Alternatively, temperature control of the combustion section can be accomplished by using only a partial amount of recycled gas, where temperature control is achieved by adjusting the proportion of exhaust gas used as fuel feedstock, which means that some exhaust gas needs to be discharged or used elsewhere.

[0020] In the apparatus of the present invention, the use of an electrically heated reforming reactor in parallel with a combustion reforming reactor allows the temperature in the combustion reforming reactor to be controlled by the electrically heated reforming reactor, wherein the combustion reforming reactor operates with the entire amount of recycled exhaust gas, possibly with some additional fuel gas, such as natural gas. The outlet temperature of the combustion reforming reactor is then controlled by adjusting the split of the process gas entering the electrically heated reforming reactor relative to the combustion reformer, wherein the outlet temperature of the combustion reforming reactor is increased by reducing the flow to the combustion reforming reactor and increasing the flow to the electrically heated reforming reactor, and vice versa. Taking advantage of the fact that power control is much faster than gas flow control, by increasing or decreasing power input to provide a constant product output, the electrically heated reforming reactor will then balance the synthesis gas product from the unit. This allows the use of natural gas input to be minimized for combustion in the synthesis gas plant for heat supply, which in turn allows optimal use of the feed gas containing hydrocarbons input to the synthesis gas plant. This can still be combined with the use of a relatively small amount of supplementary gas containing hydrocarbons, which is also fed into one or more burners of the combustion reforming reactor to allow control of the burner load and accurate control of the temperature.

[0021] It should be noted that the combustion reforming reactor and the electrically heated reforming reactor in parallel will produce a larger amount of exhaust gas than operating the SMR alone at the same capacity. Since the electrically heated reforming reactor is heated without the use of fuel gas, no exhaust gas is recycled to the electrically heated reforming reactor. Therefore, all the exhaust gas can be recycled to the burner of the combustion reforming reactor. This means that the additional fuel input to the combustion reforming reactor (for example in the form of natural gas) can be reduced or eliminated. Compared with a reforming section with independent electrically heated reforming (in which the exhaust gas has no natural use but ends up as an unwanted by-product of the process), this produces a design advantage of the device of the present invention.

[0022] Additionally, by allowing a portion of the reforming reaction to occur within the electrically heated reforming reactor, the fuel input to the combustion reforming reactor can be reduced / minimized.

[0023] It should be noted that the condensate from the gas separation unit is typically primarily water, but it may also contain trace amounts of dissolved gases such as CO2, H2, etc. It should also be noted that the gas separation unit also potentially provides a by-product stream, such as a stream containing CO2 from a CO2 removal operation.

[0024] The term "combustion reforming reactor" is intended to mean a reforming reactor in which fuel is burned to provide heat for the steam methane reforming reaction. It should also be noted that the term "reforming reactor" is intended to cover any suitable reactor in which steam methane reforming occurs. Thus, a "reforming reactor" includes a combustion steam methane reforming reactor, a convection reforming reactor, an electrically heated steam methane reforming reactor, an autothermal reforming reactor, a gas-heated steam methane reforming reactor, a bayonet reforming reactor, and the like.

[0025] Since the electrically heated reforming reactor is electrically heated, it incurs less overall energy consumption compared to a fired steam methane reforming reactor, since high temperature flue gases of the reforming reactor are avoided. Furthermore, if the electricity used to heat the electrically heated reforming reactor and possibly other units of the synthesis gas plant is provided by renewable energy, the overall consumption of hydrocarbons of the synthesis gas plant is minimized and CO2 emissions are also reduced accordingly.

[0026] Typically, the combined synthesis gas stream from the reforming section comprises the first and second synthesis gas streams. Therefore, the further processing of the combined synthesis gas from the reforming section is carried out for all the first and second synthesis gas streams combined. However, it is conceivable that the combined synthesis gas stream only comprises a part of the first and / or second synthesis gas streams, and the remaining part of the first and / or second synthesis gas streams is directed to other devices downstream of the reforming section. This can be, for example, the case where the synthesis gas plant is arranged to provide a product stream in the form of a hydrogen stream and another product stream in the form of a synthesis gas stream rich in CO.

[0027] In this context, the term "feed gas containing hydrocarbons" is intended to mean a gas having one or more hydrocarbons and possible other components. Therefore, in addition to a small amount of other gases, a feed gas containing hydrocarbons generally also contains hydrocarbon gases, such as CH4 and optionally also contains relatively small amounts of higher hydrocarbons. Higher hydrocarbons are components with two or more carbon atoms, such as ethane and propane. Examples of "hydrocarbon gases" can be natural gas, city gas, naphtha or a mixture of methane and higher hydrocarbons, biogas or LPG. Hydrocarbons can also be components with other atoms other than carbon and hydrogen, such as oxygenates. The term "feed gas containing hydrocarbons" refers to a feed gas containing hydrocarbon gases, wherein one or more hydrocarbons are mixed with steam, hydrogen and possible other components such as carbon monoxide, carbon dioxide and nitrogen and argon. Typically, the feed gas entering the reforming section has a predetermined ratio of hydrocarbon gases, steam and hydrogen, and may also have carbon dioxide.

[0028] Furthermore, the term "steam reforming" or "steam methane reforming reaction" refers to a reforming reaction that proceeds according to one or more of the following reactions:

[0029]

[0030]

[0031]

[0032] Reactions (i) and (ii) are steam methane reforming reactions, while reaction (iii) is a dry methane reforming reaction.

[0033] For higher hydrocarbons, i.e., C n H m , where n≥2, m≥4, formula (i) can be summarized as:

[0034] C n H m +nH2O→nCO+(n+m / 2)H2 (iv), where n≥2, m≥4

[0035] Typically, steam reforming is accompanied by a water-gas shift reaction (v):

[0036]

[0037] The terms "steam methane reforming" and "steam methane reforming reaction" are meant to cover reactions (i) and (ii), the term "steam reforming" is meant to cover reactions (i), (ii) and (iv), and the term "methanation" covers the reverse reaction of reaction (i). In most cases, all of these reactions (i)-(v) are at or near equilibrium at the outlet of the reforming reactor. The term "pre-reforming" is generally used to cover the catalytic conversion of higher hydrocarbons according to reaction (iv). Pre-reforming is generally accompanied by steam reforming and / or methanation of methane (depending on the gas composition and operating conditions) and the water gas shift reaction. Pre-reforming is generally carried out in an adiabatic reactor, but can also be carried out in a heated reactor.

[0038] The term "synthesis gas" refers to a gas comprising hydrogen, carbon monoxide and also carbon dioxide and small amounts of other gases such as argon, nitrogen, methane and the like.

[0039] Generally, before entering the reforming section, the feed gas will undergo desulfurization to remove sulfur therein, thereby avoiding catalyst deactivation in the reforming reactor of the reforming section.

[0040] In one embodiment, the synthesis gas plant further comprises a gas purification unit and / or a pre-reforming unit upstream of the reforming section. The gas purification unit is for example a desulfurization unit, such as a hydrodesulfurization unit.

[0041] In the pre-reformer, the hydrocarbon gas will be pre-reformed according to reaction (iv) with steam, and possibly hydrogen and / or other components such as carbon dioxide, in a temperature range of about 350-550° C. to convert higher hydrocarbons as the initial step of the process, which usually occurs downstream of the desulfurization step. This eliminates the risk of carbon formation from higher hydrocarbons on the catalyst in subsequent process steps. Optionally, carbon dioxide or other components can also be mixed with the gas leaving the pre-reforming step to form the feed gas.

[0042] Gas separation units include one or more of the following units: flash separation units, CO2 removal units, pressure swing adsorption units (PSA units), membranes and / or cryogenic separation units. Flash separation refers to phase separation units in which, at a given temperature, a stream is separated into a liquid phase and a gas phase that are close to or in thermodynamic phase equilibrium. CO2 removal refers to units that remove CO2 from process gases using processes such as chemical adsorption. In chemical adsorption, a gas containing CO2 is passed through a solvent that reacts with CO2 and binds CO2 in this way. Most chemical solvents are amines, divided into primary amines such as monoethanolamine (MEA) and diglycolamine (DGA), secondary amines such as diethanolamine (DEA) and diisopropanolamine (DIPA), or tertiary amines such as triethanolamine (TEA) and methyldiethanolamine (MDEA), but ammonia and liquid alkali metal carbonates such as K2CO3 and NaCO3 can also be used. Swing adsorption refers to units used for the adsorption of selected compounds. In this type of device, gas molecules establish a dynamic equilibrium between adsorption and desorption on the adsorption material. The adsorption of gas molecules can be caused by steric, kinetic or equilibrium effects. The exact mechanism will be determined by the adsorbent used, and the equilibrium saturation will depend on temperature and pressure. Typically, the adsorbent material is treated in a mixed gas until the heaviest compound is close to saturation, and then regeneration is required. Regeneration can be accomplished by changing the pressure or temperature. In practice, this means using a process with at least two units, first saturating the adsorbent at high pressure or low temperature in one unit, then switching the unit and now desorbing the adsorbed molecules from the same unit by reducing the pressure or increasing the temperature. When the unit is operated under pressure changes, it is called a pressure swing adsorption unit, and when the unit is operated under temperature changes, it is called a temperature swing adsorption unit. Pressure swing adsorption can produce hydrogen purity of 99.9% or more. Membrane refers to separation on at least partially solid barriers, such as polymers, in which the transmission of individual gas species occurs at different rates determined by their permeabilities. This allows the components in the membrane retentate to be enhanced or diluted. Cryogenic separation refers to the process of separating individual components from a gas mixture by controlling the temperature using the phase change of different species in the gas, which usually occurs at less than -150°C.

[0043] In a specific embodiment, the gas separation unit comprises a flash separation unit connected in series with a pressure swing adsorption unit. Thus, the condensate comprising mainly water is first separated in the flash separation unit and then the hydrogen product is purified in the pressure swing adsorption unit. In this embodiment, the pressure swing adsorption unit will also produce an exhaust gas comprising CO2, CO, CH4 and H2.

[0044] In another specific embodiment, the gas separation unit has a flash separation unit in series with the carbon removal unit, which is connected in series with the CO cold box. The condensate mainly containing water is thus first separated in the flash separation unit, and then the CO2 is removed in the CO2 removal unit. Finally, the product gas is separated into a product gas of substantially pure CO, a product gas of substantially pure H2, and an exhaust gas. In this case, the exhaust gas will contain CO, CH4 and H2.

[0045] By the configuration of the syngas plant, maximum utilization of all streams is achieved by returning the fuel-rich exhaust gas produced from the various embodiments of the gas separation unit to the one or more combustors.

[0046] In a particular embodiment of the apparatus of the invention, the apparatus comprises control means for adjusting the ratio of the first portion of the feed gas to the second portion of the feed gas so as to produce a selected outlet temperature in the second synthesis gas stream and a selected amount of waste gas from the gas separation unit. Preferably, the apparatus further comprises control means for adjusting the heating of the electrically heated reforming reactor to produce a constant output of the first synthesis gas stream.

[0047] In one embodiment, the electrically heated reforming reactor of the syngas plant comprises:

[0048] a pressure shell housing an electric heating unit arranged to heat said first catalyst, wherein said first catalyst comprises a catalytically active material operable to catalyze steam reforming of a first portion of the feed gas, wherein the pressure shell has a design pressure of 5 to 45 bar,

[0049] - a thermal insulation layer adjacent to at least a portion of the interior of the pressure vessel, and

[0050] - at least two conductors electrically connected to the electric heating unit and to a power source placed outside the pressure vessel,

[0051] Wherein the power source is sized to heat at least a portion of the first catalyst to a temperature of at least 500° C. by passing an electric current through the electric heating unit.

[0052] An important feature of an electrically heated reforming reactor is that energy is provided inside the reforming reactor, rather than by external heat sources such as heat conduction, convection and radiation (e.g., through catalyst tubes). In an electrically heated reforming reactor having an electric heating unit connected to a power source by a conductor, heat for the reforming reaction is provided by resistive heating. The hottest part of the electrically heated reforming reactor will be located within the pressure shell of the electrically heated reforming reactor. Preferably, the size of the power source and the electric heating unit within the pressure shell is designed so that at least a portion of the electric heating unit reaches a temperature of 850°C, preferably 900°C, more preferably 1000°C or even more preferably 1100°C.

[0053] The synthesis gas plant of the present invention may advantageously comprise one or more compressors and / or pumps upstream of the reforming section. The compressor / pump is arranged to compress the feed to a pressure between 5 and 45 bar. The components of the feed, i.e. water / steam, hydrogen and hydrocarbon feed, may be compressed separately and fed separately to the reforming section or its reforming reactor.

[0054] The first catalyst may be a bed of catalyst particles, such as pellets, which are typically in the form of a catalytically active material supported on a high-area support, wherein the conductive structure is embedded in the bed of catalyst particles. Alternatively, the catalyst may be a catalytically active material supported on a macrostructure such as a monolith.

[0055] When the electrically heated reforming reactor includes an insulating layer adjacent to at least a portion of the interior of the pressure shell, appropriate thermal and electrical insulation is obtained between the electrically heated unit and the pressure shell. Typically, the insulating layer will be present over a large portion of the interior of the pressure shell to provide thermal insulation between the pressure shell and the electrically heated unit / first catalyst; however, channels in the insulating layer are required to provide connection of conductors between the electrically heated unit and the power source and to provide inlet / outlet for gas to enter / exit the electrically heated reforming reactor.

[0056] The presence of an insulating layer between the pressure shell and the electric heating unit helps to avoid overheating of the pressure shell and helps to reduce heat losses around the electrically heated reforming reactor. The temperature of the electric heating unit can reach about 1300°C, at least in certain parts thereof, but by using an insulating layer between the electric heating unit and the pressure shell, the temperature of the pressure shell can be maintained at a significantly lower temperature, such as 500°C or even 200°C. This is advantageous because conventional construction steels are not suitable for applications that withstand pressure at high temperatures (e.g., above 1000°C). In addition, the insulating layer between the pressure shell and the electric heating unit helps to control the current within the reforming reactor because the insulating layer is also electrically insulating. The insulating layer can be one or more layers of solid material, such as ceramics, inert materials, refractory materials or gas barriers or combinations thereof. Therefore, it is also conceivable that the purge gas or confined gas constitutes or forms part of the insulating layer.

[0057] Since the hottest part of the electrically heated reforming reactor during operation is the electrically heated unit surrounded by the insulation layer, the temperature of the pressure shell can be kept significantly lower than the maximum process temperature. This allows the pressure shell to have a relatively low design temperature, for example, the pressure shell is 700°C or 500°C or preferably 300°C or 200°C, while having a maximum process temperature of 800°C or 900°C or even 1100°C or even up to 1300°C.

[0058] Another advantage is that the lower design temperature compared to combustion SMRs means that in some cases the thickness of the pressure vessel can be reduced, saving costs.

[0059] It should be noted that the term "insulating material" is intended to mean a material having a thermal conductivity of about 10 W·m -1 ·K -1 Examples of thermal insulation materials are ceramics, refractory materials, alumina-based materials, zirconia-based materials, and the like.

[0060] In one embodiment, the synthesis gas device also includes a control system, which is arranged to control the power supply to ensure that the temperature of the gas leaving the electrically heated reforming reactor is within a predetermined range and / or to ensure that the conversion rate of hydrocarbons in the first part of the feed gas is within a predetermined range and / or to ensure that the dry molar concentration of methane is within a predetermined range and / or to ensure that the approaching equilibrium of the steam reforming reaction is within a predetermined range. Typically, the maximum temperature of the gas is between 500°C and 1000°C, for example, between 850°C and 1000°C, for example, about 950°C, but even higher temperatures, such as up to 1300°C, can be imagined. However, the maximum temperature of the gas leaving the electrically heated reforming reactor can be as low as 500°C, for example, when the electrically heated reforming reactor is a bayonet type. The bayonet tube reforming reactor has an inner tube coaxially arranged in an outer sleeve, and the first catalyst is located in an annular space between the outer sleeve and the inner tube. From the flow direction of the feed gas, the maximum temperature of the gas will be achieved at the most downstream portion close to the first catalyst.

[0061] The control of the power supply is the control of the electrical output of the power supply. The control of the power supply can be performed, for example, as the control of the voltage and / or current from the power supply, as the control of whether the power supply is turned on or off, or a combination thereof. The power provided to the electrically heated reforming reactor can be in the form of alternating current or direct current.

[0062] In one embodiment, the reforming section of the gas device also includes an autothermal reforming reactor located downstream of the electrically heated reforming reactor and the combustion reforming reactor. The autothermal reforming reactor contains a third catalyst and is arranged to receive the first and / or second synthesis gas or a portion thereof and provide a self-reforming synthesis gas flow, wherein the self-reforming synthesis gas flow is output from the reforming section as at least a portion of the combined gas flow. In addition to the first and / or second synthesis gas or a portion thereof input into the autothermal reforming reactor, the oxidant gas flow is an inlet. The oxidant gas flow contains oxygen and can be, for example, air or oxygen, or a mixture of more than 90% of which is oxygen, and the remainder is, for example, nitrogen, steam and / or argon. In one embodiment, since the temperature of the first synthesis gas leaving the electrically heated reforming reactor may be relatively high, for example, 900°C to 1050°C, the first synthesis gas can bypass the autothermal reforming reactor so that only the second synthesis gas from the combustion reforming reactor is input to the autothermal reforming reactor. In this case, the first synthesis gas and the self-reforming synthesis gas are combined into a combined synthesis gas output from the reforming section. Alternatively, the second synthesis gas can bypass the autothermal reforming reactor. Adding an autothermal reforming reactor to the reforming section of a synthesis gas plant allows to increase the overall output of the synthesis gas plant compared to a synthesis gas plant having an electrically heated reforming reactor and a fired reforming reactor.

[0063] In one embodiment, the reforming section of the synthesis gas device also includes a gas-heated steam methane reforming reactor located downstream of the electrically heated reforming reactor and the combustion reforming reactor. The gas-heated steam methane reforming reactor contains a fourth catalyst and is operable to receive a third portion of a feed gas containing hydrocarbons and utilizes at least a portion of the first and / or second synthesis gas streams as a heating medium for heat exchange within the gas-heated steam methane reforming reactor. The gas-heated steam methane reforming reactor is arranged to produce a third synthesis gas stream through a fourth catalyst and output the third synthesis gas stream from the reforming section as at least a portion of the combined synthesis gas. The total thermal efficiency of the synthesis gas device is improved by adding a gas-heated steam methane reforming reactor because the sensible heat of the first and second synthesis gas streams is used in the gas-heated steam methane reforming reactor. In addition, when the synthesis gas device includes a gas-heated steam methane reforming reactor, the total output of the synthesis gas device is increased compared to a synthesis gas device without an additional gas-heated steam methane reforming reactor.

[0064] In one embodiment, the reforming section of the synthesis gas device also includes a gas-heated steam methane reforming reactor in parallel with the electric heating reforming reactor and the combustion reforming reactor. The gas-heated steam methane reforming reactor contains a fourth catalyst and is operable to receive a third portion of a feed gas containing hydrocarbons and utilizes at least a portion of the self-reforming synthesis gas flow as a heating medium for heat exchange in the gas-heated steam methane reforming reactor. The gas-heated steam methane reforming reactor is arranged to produce a third synthesis gas flow and output the third synthesis gas flow from the reforming section as at least a portion of the combined synthesis gas. In this embodiment, the synthesis gas device includes a combustion reforming reactor in parallel with the electric heating reforming reactor upstream of the autothermal reforming reactor, and in parallel with the gas-heated steam methane reforming reactor. Since the temperature of the first synthesis gas leaving the electric heating reforming reactor may be relatively high, for example, 900°C to 1050°C, the first synthesis gas can bypass the autothermal reactor. Therefore, the first synthesis gas can be directly introduced into the gas-heated steam methane reforming reactor, and the second synthesis gas can be input into the autothermal reforming reactor. The mixture of the first synthesis gas, the second synthesis gas and the self-reforming synthesis gas is input to the steam methane reforming reactor heated by gas. The mixture provides heat for the steam reforming of the third part of the feed gas containing hydrocarbons. In one configuration, after the third part of the feed gas is reformed in the reforming reactor heated by gas, the mixture of the first synthesis gas, the second synthesis gas and the self-reforming synthesis gas is mixed with the third synthesis gas in the reforming reactor heated by gas. Therefore, the gas output from the steam methane reforming reactor heated by gas is a combined synthesis gas. Alternatively, the second synthesis gas is input to the autothermal reforming reactor, and the self-reforming synthesis gas is input to the steam methane reforming reactor heated by gas as a heating medium, and the steam methane reforming reactor heated by gas produces and outputs the third synthesis gas. The first synthesis gas can bypass both the autothermal reforming reactor and the gas-heated reactor, and merge with the third synthesis gas downstream of the steam methane reforming reactor heated by gas to form a combined synthesis gas stream. When the synthesis gas plant includes four reforming reactors, the total output of the synthesis gas plant increases.

[0065] A gas heated steam methane reforming reactor is arranged to provide heat for the endothermic steam methane reforming reaction using hot gas by heat exchange, typically on the tube walls. One example of a configuration of a heat exchange reformer has a plurality of parallel tubes that receive feed gas and are filled with catalyst. At the bottom of the reactor, product gas from the tubes filled with catalyst is mixed with hot synthesis gas from an upstream reforming unit, and the combined synthesis gas is heat exchanged with the tubes filled with catalyst. Other configurations of heat exchange reformers are also conceivable.

[0066] In one embodiment, the post-processing unit is a post-conversion unit with an inlet that allows heated CO2 to be added to the combined synthesis gas upstream of the post-conversion unit; the post-processing unit contains a fifth catalyst that has the activity of catalyzing steam methane reforming, methanation, and reverse water gas shift reactions. The post-conversion unit is, for example, an adiabatic post-conversion unit or a gas-heated heat exchange reactor. The post-processed synthesis gas stream is a synthesis gas stream with a H2 / CO ratio lower than the H2 / CO ratio of the combined synthesis gas. By adding heated CO2 in a separate reactor downstream of the reforming section and performing steam methane reforming / methanation and reverse water gas shift reactions, the CO production of the process can be increased and / or the H2 / CO ratio can be adjusted. The H2 / CO ratio of the post-processed synthesis gas stream is, for example, lower than 1.8, lower than 1.5, or even lower than 1.0. The temperature of the added heated CO2 can be, for example, a temperature of about 300°C, 400°C, or even about 500°C or higher.

[0067] In one embodiment, the post-treatment unit is a water-gas shift unit arranged to perform a water-gas shift reaction (reaction (v) above). In this embodiment, the post-treated synthesis gas is a water-gas shift synthesis gas stream, such as a hydrogen-rich synthesis gas or a hydrogen stream. The water-gas shift unit can be a single water-gas shift unit, such as a medium-temperature water-gas shift unit, or a combination of two or more water-gas shift units, such as a combination of a high-temperature water-gas shift unit and a low-temperature water-gas shift unit.

[0068] In one embodiment, the combustion reforming reactor is a steam methane reforming reactor.The steam methane reforming reactor is, for example, a side-fired, top-fired, bottom-fired, or platform-fired SMR.

[0069] In one embodiment, the fired reforming reactor is a convective reforming reactor, wherein flue gas from one or more burners is used as a heat exchange medium with the convective reforming reactor.

[0070] The tubes of the convective reforming reactor can be configured such that the tubes containing the second catalyst are enclosed in a shell. The tubes containing the second catalyst receive sensible heat from the flue gas outside the tubes by convection. One or more burners produce a flue gas flow with sensible heat. The shell forms a convection channel or convection chamber that allows the flue gas to leave the burner and flow through the tubes containing the second catalyst. The outer surface of the tube containing the second catalyst is preferably provided with fins or nails to increase its surface area exposed to the flue gas. As used herein, the flue gas from the burner section typically has a temperature above 700°C, for example between 700°C and 1200°C.

[0071] In one embodiment, the electric heating unit comprises a macrostructure of conductive material, wherein the macrostructure carries a ceramic coating and the ceramic coating carries a catalytically active material. Therefore, during operation of the synthesis gas plant, an electric current passes through the macrostructure and heats the macrostructure and the catalytically active material carried thereon. The close proximity between the catalytically active material and the macrostructure enables the catalytically active material to be effectively heated by heat conduction from the solid material of the macrostructure heated by electrical resistance. Under given operating conditions, the amount and composition of the catalytically active material can be adjusted according to the steam reforming reaction. Under given operating conditions, the surface area of ​​the macrostructure, the proportion of the macrostructure coated with the ceramic coating, the type and structure of the ceramic coating, and the amount and composition of the catalytically active material can be adjusted according to the steam reforming reaction.

[0072] The term "conductive" means a resistivity of 10 at 20°C. -4 Up to 10 -8 Ω·m. Thus, the conductive material is, for example, a metal such as copper, silver, aluminum, chromium, iron, nickel, or a metal alloy. Furthermore, the term "electrically insulating" means a material having a resistivity higher than 10 Ω·m at 20°C, for example 10 9 Up to 10 25 Ω·m material.

[0073] As used herein, the term "electric heating unit comprising a macro-catalyst" is not meant to be limited to a reforming reactor having a single macrostructure. Rather, the term is intended to encompass macrostructures having a ceramic coating and a catalytically active material, as well as arrays of such macrostructures having a ceramic coating and a catalytic material.

[0074] The term "macrostructure loaded with a ceramic coating" is intended to mean that the macrostructure is coated with a ceramic coating at at least a portion of the surface of the macrostructure. Thus, the term does not mean that all surfaces of the macrostructure are covered with a ceramic coating; in particular, there is no coating at least on the portion of the macrostructure that is electrically connected to the conductor and thus to the power source. The coating is a ceramic material with pores in its structure that allows the catalytically active material to be loaded on and inside the coating and has the same function as a catalytic support. Advantageously, the catalytically active material comprises catalytically active particles having a size ranging from about 5 nm to about 250 nm.

[0075] As used herein, the term "macrostructure" is intended to mean a structure that is large enough to be visible to the naked eye without the need for a magnifying device. The dimensions of the macrostructure are typically in the range of centimeters or even meters. It is advantageous to have the dimensions of the macrostructure correspond at least partially to the internal dimensions of the pressure vessel, thereby saving space for insulation and conductors.

[0076] Ceramic coatings with or without catalytically active materials can be added directly to metal surfaces by washcoating. Washcoating of metal surfaces is a well-known process; described, for example, in Cybulski, A. and Moulijn, JA, Structured catalysts and reactors, Marcel Dekker, Inc, New York, 1998, Chapter 3, and references therein. The ceramic coating can be added to the surface of the macrostructure and subsequently the catalytically active material can be added; alternatively, the ceramic coating containing the catalytically active material is added to the macrostructure.

[0077] Preferably, the macrostructure is manufactured by extruding a mixture of powdered metal particles and a binder into an extruded structure and then sintering the extruded structure, thereby providing a material with a high geometric surface area per unit volume. In order to form a chemical bond between the ceramic coating and the macrostructure, a ceramic coating that may contain a catalytic material is provided on the macrostructure before the second sintering in an oxidizing atmosphere. Alternatively, the catalytically active material may be impregnated onto the ceramic coating after the second sintering. When a chemical bond is formed between the ceramic coating and the macrostructure, a particularly high thermal conductivity between the electrically heated macrostructure and the catalytically active material supported by the ceramic coating is possible, providing close and almost direct contact between the heat source and the catalytically active material of the macrostructure. Since the distance between the heat source and the catalytically active material is very close, heat transfer is effective, so that the macrostructure can be heated very effectively. Therefore, in terms of gas processing per reforming reactor volume, a compact reforming reactor is possible, and therefore the reforming reactor that accommodates the macrostructure can be compact. The reforming reactor of the present invention does not require a furnace and this significantly reduces the size of the electrically heated reforming reactor.

[0078] Preferably, the macrostructure comprises Fe, Ni, Cu, Co, Cr, Al, Si or an alloy thereof. Such alloys may contain other elements, such as Mn, Y, Zr, C, Co, Mo or a combination thereof. Preferably, the catalytically active material is a particle having a size of 5 nm to 250 nm. The catalytically active material may, for example, comprise nickel, ruthenium, rhodium, iridium, platinum, cobalt or a combination thereof. Thus, a possible catalytically active material is a combination of nickel and rhodium and another combination of nickel and iridium. The ceramic coating may, for example, be an oxide comprising Al, Zr, Mg, Ce and / or Ca. Exemplary coatings are calcium aluminate or magnesium aluminum spinel. Such a ceramic coating may contain additional elements, such as La, Y, Ti, K or a combination thereof. Preferably, the conductor is made of a different material from the macrostructure. The conductor may be, for example, iron, nickel, aluminum, copper, silver or an alloy thereof. The ceramic coating is an electrically insulating material, the thickness of which is typically around 100 μm, for example 10-500 μm. Additionally, a sixth catalyst may be placed within the pressure shell and in channels within the macrostructure, around the macrostructure, or upstream and / or downstream of the macrostructure to support the catalytic function of the macrostructure.

[0079] In one embodiment, the first, second, third, fourth, fifth and / or sixth catalyst is a catalyst suitable for steam reforming reaction, pre-reforming reaction, methanation and / or water gas shift reaction. Examples of relevant such catalysts are Ni / MgAl2O4, Ni / CaAl2O4, Ni / Al2O3, Fe2O3 / Cr2O3 / MgO and Cu / Zn / Al2O3. In one embodiment, the first, second, third, fourth, fifth and / or sixth catalyst is a steam reforming catalyst. Examples of steam reforming catalysts are Ni / MgAl2O4, Ni / Al2O3, Ni / CaAl2O4, Ru / MgAl2O4, Rh / MgAl2O4, Ir / MgAl2O4, Mo2C, Wo2C, CeO2, precious metals on Al2O3 carriers, but other catalysts suitable for reforming are also conceivable.

[0080] Another aspect of the present invention relates to a method for producing synthesis gas in a synthesis gas plant including a reforming section. The reforming section includes an electrically heated reforming reactor containing a first catalyst, and a combustion reforming reactor connected in parallel with the electrically heated reforming reactor. The combustion reforming reactor includes one or more tubes containing a second catalyst. The combustion reforming reactor also includes one or more burners arranged to provide heat for the steam methane reforming reaction in the one or more tubes. The method comprises the following steps:

[0081] - introducing a first portion of a feed gas comprising hydrocarbons into an electrically heated reforming reactor and subjecting it to steam methane reforming to provide a first synthesis gas stream,

[0082] - introducing a second portion of the feed gas comprising hydrocarbons into a combustion reforming reactor and subjecting it to steam methane reforming to provide a second synthesis gas stream,

[0083] - supplying fuel gas to one or more burners to provide heat for the steam methane reforming reaction in one or more tubes of the combustion reforming reactor,

[0084] - outputting from the reforming section a combined synthesis gas stream comprising the first and / or second synthesis gas stream or a portion thereof,

[0085] - optionally, post-treating the combined synthesis gas stream in a post-treating unit downstream of the electrically heated reforming reactor and the fired reforming reactor to provide a post-treated synthesis gas stream,

[0086] - separation of the combined synthesis gas stream or the post-treated synthesis gas stream into condensate, product synthesis gas and off-gas in a gas separation unit downstream of the water-gas shift unit, and

[0087] - Recirculating at least part of the exhaust gas from the gas separation unit as fuel gas to the burner or burners.

[0088] The advantages of the method and its embodiments correspond to the advantages of the synthesis gas plant and its embodiments, and are therefore not described in further detail here.

[0089] However, it should be noted that the first, second and optional third parts of the feed gas containing hydrocarbons can be the first, second and optional third parts of a single feed gas stream containing hydrocarbons, wherein the single feed gas stream is divided into streams that may be fed to the first, second and optional third reforming reactors together with steam. In this case, the composition of the first, second and optional third parts of the feed gas is substantially the same. However, before they are fed into respective reforming reactors, additional gases, such as oxidant gas and / or steam, can be added to the first, second and optional third parts of the feed gas.

[0090] In one embodiment, the first part of the feed gas is about 5-20% by volume of the feed gas. In the case where the reforming section includes an electrically heated reforming reactor and a combustion reforming reactor and there is no other reforming reactor, the first part of the feed gas entering the electrically heated reforming reactor is advantageously about 10-20% by volume of the feed gas, such as about 15% by volume, and the second part of the feed gas entering the combustion reforming reactor is therefore about 80-90% by volume of the feed gas, such as about 85% by volume. In the case where the synthesis gas plant is a hydrogen production device and the gas separation unit is a PSA unit, these relative amounts of the first and second parts of the feed gas are advantageous. In an alternative embodiment, such as in a synthesis gas plant with a cold box, the first part is 40 to 60% by volume of the feed gas, and the second part is 60 to 40% by volume of the feed gas. It should be noted that after being divided into the first and second parts of the feed gas, additional gas, such as steam, can be added to the first and / or second parts of the feed gas. The percentage of the feed gas that becomes its first and second parts refers to the percentage when the feed gas is divided into the first and second parts.

[0091] In one embodiment, wherein the reforming stage comprises a gas heated steam methane reforming reactor, the first portion of the feed gas is about 5-10% by volume of the feed gas, the second portion of the feed gas is about 80-90% by volume of the feed gas, and the third portion of the feed gas is about 5-10% by volume of the feed gas. The ratio of the first portion of the feed gas to the second portion of the feed gas may advantageously be selected in such a way that the exhaust gas generated in the downstream gas separation system does not exceed the fuel requirement of the fired reforming reactor.

[0092] In a specific embodiment of the process of the present invention, the process is controlled by adjusting the ratio of the first portion of the feed gas to the second portion of the feed gas to produce a selected outlet temperature and a selected amount of waste gas from the gas separation unit in the second synthesis gas stream. Preferably, the process is further controlled by adjusting the heating of the electrically heated reforming reactor to produce a constant output of the first synthesis gas stream.

[0093] Furthermore, it should be noted that the order in which the process steps are written is not necessarily the order in which the process steps occur, as two or more steps may occur simultaneously or the order may differ from that described above.

[0094] BRIEF DESCRIPTION OF THE DRAWINGS

[0095] Figure 1 A hydrogen production plant according to one embodiment of the present invention is shown, wherein the reforming section comprises a steam methane reforming reactor and an electrically heated reforming reactor;

[0096] Figure 2A hydrogen production plant according to one embodiment of the present invention is shown, wherein the reforming section includes a steam methane reforming reactor, an electrically heated reforming reactor, and a gas-heated steam methane reforming reactor;

[0097] Figure 3 A synthesis gas plant according to an embodiment of the present invention is shown, wherein the reforming section comprises four reforming reactors; and

[0098] Figure 4 A synthesis gas plant according to one embodiment of the invention is shown, wherein the reforming section comprises a steam methane reforming reactor, an electrically heated reforming reactor and an autothermal reforming reactor. DETAILED DESCRIPTION OF THE INVENTION

[0100] Figure 1 A synthesis gas plant 100 according to one embodiment of the present invention is shown. The synthesis gas plant 100 is a hydrogen production plant comprising a reforming section 110 having an electrically heated reforming reactor 108 containing a first catalyst and a combustion steam reforming reactor 104 containing a second catalyst. The combustion reforming reactor is a side-fired tubular steam methane reforming reactor 104. Thus, the side-fired tubular steam methane reforming reactor 104 comprises a plurality of tubes 107 containing a second catalyst and a plurality of burners 103 arranged to heat the tubes 107. For clarity, Figure 2 Only one tube 107 is shown in FIG. Fuel is supplied to the burner 103 and burned to provide heat to the tube 107. Hot flue gas from the burner 103 is directed to the preheating section 105 of the steam methane reforming reactor 104 and used to preheat the feed gas and steam. The electrically heated reforming reactor 108 and the side-fired steam reforming reactor 104 are arranged in parallel. The electrically heated reforming reactor 108 and the side-fired steam reforming reactor 104 are configured to receive a first portion 25a and a second portion 25b of the feed gas 25, and produce a first synthesis gas 30a and a second synthesis gas 30b, respectively.

[0101] During operation of the hydrogen plant 100, a feed gas 21 containing hydrocarbons undergoes feed purification in the desulfurization unit 101 and becomes a sweetened gas 22. The feed gas 21 containing hydrocarbons is, for example, natural gas or city gas. The sweetened gas 22 is preheated in the preheating section 105 of the steam methane reformer 104 and steam 23 is added to produce a gas stream 24. The gas stream 24 is directed to a pre-reforming unit 102 containing a steam reforming catalyst. Typically, the pre-reforming unit 102 is an adiabatic pre-reforming unit in which higher hydrocarbons react so that the pre-reforming gas 25 leaving the pre-reforming unit does not contain or contains very little higher hydrocarbons. The pre-reforming gas 25 is divided into a first portion 25a of the feed gas to the electrically heated reforming reactor 108 and a second portion 25b of the feed gas to the steam methane reformer 104. The first catalyst in the electrically heated reforming reactor 108 and the second catalyst in the steam methane reformer 104 are steam methane reforming catalysts arranged to catalyze the steam methane reforming reaction in the electrically heated reforming reactor 108 and the steam methane reformer 104. The first part 25a and the second part 25b of the feed gas 25 are therefore subjected to steam methane reforming in the electrically heated reforming reactor 108 and the steam methane reformer 104, respectively, and the first synthesis gas stream 30a and the second synthesis gas stream 30b leave the electrically heated reforming reactor 108 and the steam methane reformer 104, respectively, and are combined into a combined synthesis gas stream 30 leaving the reforming section 110. The combined synthesis gas stream 30 is cooled in the heat exchanger 111 into a cooled combined synthesis gas stream 30'. The cooled combined synthesis gas stream 30' enters the post-treatment unit 112, i.e., the water-gas shift unit, and the water-gas shift synthesis gas 32 leaves the water-gas shift unit 112. The water-gas shift synthesis gas 32 is cooled in the second heat exchanger 113 to a cooled water-gas shift synthesis gas 32', which enters a gas separation unit 114. The gas separation unit 114 comprises a flash separation unit 115 and a downstream PSA unit 116. The cooled water-gas shift synthesis gas 32' thus enters the flash separation unit 115, which is arranged to separate the cooled water-gas shift synthesis gas 32' into water 27 and a dry synthesis gas 34. The dry synthesis gas 34 enters the PSA unit 116, which is arranged to separate the dry synthesis gas 34 into a product synthesis gas 40 in the form of a substantially pure hydrogen stream and an off-gas 45. The off-gas 45 is recycled as fuel to the burner 103 of the steam methane reformer 104. The off-gas 45 is combined with a small amount of natural gas 46 to form a fuel gas 47, which is sent to the burner 103 of the steam methane reformer 104. The fuel gas 47 is burned in the burner 103, thereby heating the tubes 107 with the second catalyst. In the preheating section 105, the flue gas from the burner 103 provides heat for preheating the feed gas and is discharged from the preheating section 105 as flue gas 48. The heat exchange fluid 20, such as water, is used for heat exchange in the heat exchanger 111, and the heated heat exchange fluid, such as steam, is output as stream 20'.

[0102] It should be noted that the syngas plant 100 typically includes other devices, such as compressors, heat exchangers, etc.; however, Figure 1 Such other devices are not shown.

[0103] Figure 2 A synthesis gas plant 200 according to one embodiment of the present invention is shown, wherein the reforming section 210 includes a steam methane reforming reactor, an electrically heated reforming reactor, and a gas heated steam methane reforming reactor. The synthesis gas plant 200 is a hydrogen production plant, which includes a reforming section 210, which has an electrically heated reforming reactor 208 containing a first catalyst, a combustion steam reforming reactor 204 containing a second catalyst, and a gas heated steam methane reforming reactor 206 containing a fourth catalyst. The combustion reforming reactor 204 is a side-fired tubular steam methane reforming reactor 204. Therefore, the side-fired tubular steam methane reforming reactor 204 includes a plurality of tubes 207 containing a second catalyst and a plurality of burners 203 arranged to heat the tubes 207. For clarity, Figure 2 Only one tube 207 is shown in FIG. Fuel is supplied to the burner 203 and burned to provide heat to the tube 207. Hot flue gas from the burner 203 is directed to the preheating section 205 of the steam methane reforming reactor 204 and used to preheat the feed gas and steam. The electrically heated reforming reactor 208 and the side-fired steam reforming reactor 204 are arranged in parallel. The electrically heated reforming reactor 208 and the side-fired steam reforming reactor 204 are arranged to receive the first part 25a and the second part 25b of the feed gas 25, respectively, and produce the first synthesis gas 30a and the second synthesis gas 30b, respectively.

[0104] During operation of the hydrogen plant 200, a feed gas 21 containing hydrocarbons undergoes feed purification in a desulfurization unit 201 and becomes a sweetened gas 22. The feed gas 21 containing hydrocarbons is, for example, natural gas or city gas. The sweetened gas 22 is preheated in a preheating section 205 of a steam methane reformer 204 and steam 23 is added to produce a gas stream 24. The gas stream 24 is directed to a pre-reforming unit 202 containing a steam reforming catalyst. Typically, the pre-reforming unit 202 is an adiabatic pre-reforming unit in which higher hydrocarbons react so that the pre-reforming gas 25 leaving the pre-reforming unit does not contain or contains very little higher hydrocarbons. The pre-reforming gas 25 is divided into a first portion 25a of the gas leading to an electrically heated reforming reactor 208, a second portion 25b of the feed gas leading to the steam methane reformer 204, and a third portion 25c of the feed gas leading to a gas-heated steam methane reforming reactor 206. The first catalyst in the electrically heated reforming reactor 208, the second catalyst in the steam methane reformer 204, and the fourth catalyst in the gas heated steam methane reforming reactor 206 are steam methane reforming catalysts arranged to catalyze the steam methane reforming reactions in the electrically heated reforming reactor 208, the steam methane reformer 204, and the gas heated steam methane reforming reactor 206. The first feed gas 25a, the second feed gas 25b, and the third feed gas 25c thus undergo steam methane reforming in the electrically heated reforming reactor 208, the steam methane reformer 204, and the gas steam methane reforming reactor 206, respectively. The electrically heated reforming reactor 208 produces a first synthesis gas 30a, and the steam methane reformer 204 produces a second synthesis gas 30b. The first syngas 30a and the second syngas 30b are combined into a syngas stream 30, which is introduced into the gas-heated steam methane reforming reactor 206 to provide heat for the steam methane reforming reaction of the third feed gas 25c entering the gas-heated steam methane reforming reactor from the other side.

[0105] The third synthesis gas stream 30 is discharged from the gas heated steam methane reforming reactor 206 as a combined synthesis gas stream 30 and thence from the reforming section 210. The combined synthesis gas stream 30 is cooled in the heat exchanger 211 to a cooled combined synthesis gas stream 30'. The cooled combined synthesis gas stream 30' enters the post-treatment unit 212, i.e. the water gas shift unit, and the water gas shift synthesis gas 32 leaves the water gas shift unit 212. The water gas shift synthesis gas 32 is cooled in the second heat exchanger 213 to a cooled water gas shift synthesis gas 32', which enters the gas separation unit 214. The gas separation unit 214 comprises a flash separation unit 215 and a downstream PSA unit 216. The cooled water gas shift synthesis gas 32' therefore enters the flash separation unit 215, which is arranged to separate the cooled water gas shift synthesis gas 32' into water 27 and dry synthesis gas 34. The dry syngas 34 enters the PSA unit 216 which is arranged to separate the dry syngas 34 into a product syngas 40 in the form of a substantially pure hydrogen stream and an off-gas 45. The off-gas 45 is recycled as fuel to the burner 203 of the steam methane reformer 204. The off-gas 45 is combined with a small amount of natural gas 46 to form a fuel gas 47 which is sent to the burner 203 of the steam methane reformer 204. The fuel gas 47 is burned in the burner 203, thereby heating the tubes 207 with the second catalyst. In the preheating section 205, the flue gas from the burner 203 provides heat for preheating the feed gas and is discharged from the preheating section 205 as flue gas 48. The heat exchange fluid 20, such as water, is used for heat exchange in the heat exchanger 211 and the heated heat exchange fluid, such as steam, is output as stream 20'.

[0106] It should be noted that the syngas plant 200 typically includes other devices, such as compressors, heat exchangers, etc.; however, Figure 2 Such other devices are not shown.

[0107] Figure 3 A synthesis gas plant 300 according to one embodiment of the present invention is shown, wherein the reforming section comprises four reforming reactors, namely an electrically heated reforming reactor 308 containing a first catalyst and a combustion steam reforming reactor 304 containing a second catalyst in parallel therewith. An autothermal reactor 309 containing a third catalyst is located downstream of the electrically heated reforming reactor 308 and the combustion steam reforming reactor 304, and the reforming section 310 further comprises a gas heated reactor 306 containing a fourth catalyst.

[0108] The combustion reforming reactor 304 is a side-fired tubular steam methane reforming reactor 304. Thus, the side-fired tubular steam methane reforming reactor 304 includes a plurality of tubes 307 containing a second catalyst and a plurality of burners 303 arranged to heat the tubes 307. For clarity, Figure 3Only one tube is shown in FIG. 307. Fuel is supplied to the burner 303 and burned to provide heat to the tube 307. The hot flue gas from the burner 303 is directed to the preheating section 305 of the steam methane reforming reactor 304 and used to preheat the feed gas and steam. The electric heating reforming reactor 308 and the side-fired steam reforming reactor 304 are arranged in parallel. The electric heating reforming reactor 308 and the side-fired steam reforming reactor 304 are arranged to receive the first part 25a and the second part 25b of the feed gas 25, respectively, and produce the first synthesis gas 30a and the second synthesis gas 30b, respectively.

[0109] During operation of the synthesis gas plant 300, a feed gas 21 containing hydrocarbons undergoes feed purification in a desulfurization unit 301 and becomes a sweetened gas 22. The feed gas 21 containing hydrocarbons is, for example, natural gas or city gas. The sweetened gas 22 is preheated in a preheating section 305 of a steam methane reforming reactor 304 and steam 23 is added to produce a gas stream 24. The gas stream 24 is directed to a pre-reforming unit 302 containing a steam reforming catalyst. Typically, the pre-reforming unit 302 is an adiabatic pre-reforming unit in which higher hydrocarbons react so that the pre-reforming gas 25 leaving the pre-reforming unit does not contain or contains very little higher hydrocarbons. The pre-reforming gas 25 is divided into a first portion 25a of the feed gas to the electrically heated reforming reactor 308, a second portion 25b of the feed gas to the steam methane reformer 304, and a third portion 25c of the feed gas to the gas-heated steam methane reforming reactor 306.

[0110] The first catalyst in the electrically heated reforming reactor 308, the second catalyst in the steam methane reformer 304, the third catalyst in the autothermal reformer 309 and the fourth catalyst in the gas heated steam methane reforming reactor 306 are steam methane reforming catalysts, which are arranged to catalyze the steam methane reforming reactions in the electrically heated reforming reactor 308, the steam methane reformer 304, the autothermal reformer 309 and the gas heated steam methane reforming reactor 306.

[0111] The first part 25a, the second part 25b and the third part 25c of the feed gas are thus subjected to steam methane reforming in the electrically heated reforming reactor 308, the steam methane reforming reactor 304 and the gas heated steam methane reforming reactor 306, respectively. The electrically heated reforming reactor 308 produces a first synthesis gas 30a and the steam methane reforming reactor 304 produces a second synthesis gas 30b. The first synthesis gas 30a and the second synthesis gas 30b are combined into a synthesis gas stream 31, which is introduced into the autothermal reforming reactor 309. A stream 26 of an oxidant gas, such as oxygen or air, also enters the autothermal reforming reactor 309. The self-reforming gas stream 27 leaves the autothermal reformer 309 and enters the gas heated steam methane reforming reactor 306 to provide heat for the steam methane reforming reaction of the third part 25c of the feed gas 25 entering the gas heated steam methane reforming reactor 306 from the other side.

[0112] Synthesis gas stream 30 exits the gas heated steam methane reforming reactor 306 and thence exits the reforming section 310 as combined synthesis gas stream 30. The combined synthesis gas stream 30 is cooled in heat exchanger 313 to form a cooled combined synthesis gas stream 30'.

[0113] The cooled combined synthesis gas stream 30' enters a gas separation unit 314. The gas separation unit 314 comprises a flash separation unit 315 and a downstream PSA unit 316. Thus, the cooled water-gas shift synthesis gas 32' enters the flash separation unit 315, which is arranged to separate the cooled water-gas shift synthesis gas 32' into water 27 and a dry synthesis gas 34. The dry synthesis gas 34 enters the PSA unit 316, which is arranged to separate the dry synthesis gas 34 into a product synthesis gas 40 in the form of a stream of hydrogen and carbon monoxide, and an exhaust gas 45. The exhaust gas 45 is recycled as fuel to the burner 303 of the steam methane reforming reactor 304. The exhaust gas 45 is combined with a small amount of natural gas 46 to form a fuel gas 47, which is sent to the burner 303 of the steam methane reforming reactor 304. The fuel gas 47 is burned in the burner 303, thereby heating the tubes 307 with the second catalyst. In preheating section 305, flue gas from burner 303 provides heat for preheating the feed gas and is exhausted from preheating section 305 as flue gas 48. Heat exchange fluid 20, such as water, is used for heat exchange in heat exchanger 311 and heated heat exchange fluid, such as steam, is output as stream 20'.

[0114] It should be noted that the syngas plant 300 typically includes other devices, such as compressors, heat exchangers, etc.; however, Figure 3 Such other devices are not shown.

[0115] Figure 4A synthesis gas plant according to one embodiment of the invention is shown, wherein the reforming section comprises a steam methane reforming reactor, an electrically heated reforming reactor and an autothermal reforming reactor.

[0116] Figure 4 A synthesis gas plant 400 according to one embodiment of the present invention is shown, wherein the reforming section comprises four reforming reactors, namely an electrically heated reforming reactor 408 containing a first catalyst, and a combustion steam reforming reactor 404 containing a second catalyst in series therewith. An autothermal reactor 409 containing a third catalyst is located downstream of the electrically heated reforming reactor 408 and the combustion steam reforming reactor 404.

[0117] The combustion reforming reactor 404 is a side-fired tubular steam methane reforming reactor 404. Thus, the side-fired tubular steam methane reforming reactor 404 includes a plurality of tubes 407 containing a second catalyst and a plurality of burners 403 arranged to heat the tubes 407. For clarity, Figure 4 Only one tube 407 is shown in FIG. 4. Fuel is supplied to the burner 403 and burned to provide heat to the tube 407. The hot flue gas from the burner 403 is directed to the preheating section 405 of the steam methane reforming reactor 404 and used to preheat the feed gas and steam. The electrically heated reforming reactor 408 and the side-fired steam reforming reactor 404 are arranged in parallel. The electrically heated reforming reactor 408 and the side-fired steam reforming reactor 404 are arranged to receive the first part 25a and the second part 25b of the feed gas 25, respectively, and produce the first synthesis gas 30a and the second synthesis gas 30b, respectively.

[0118] During operation of the synthesis gas plant 400, a feed gas 21 containing hydrocarbons undergoes feed purification in a desulfurization unit 401 and becomes a sweetened gas 22. The feed gas 21 containing hydrocarbons is, for example, natural gas or city gas. The sweetened gas 22 is preheated in a preheating section 405 of a steam methane reforming reactor 404 and steam 23 is added to produce a gas stream 24. The gas stream 24 is directed to a pre-reforming unit 402 containing a steam reforming catalyst. Typically, the pre-reforming unit 402 is an adiabatic pre-reforming unit, in which higher hydrocarbons react so that the pre-reforming gas 25 leaving the pre-reforming unit does not contain or contains very small amounts of higher hydrocarbons. The pre-reforming gas 25 is divided into a first portion 25a of the feed gas 25 leading to an electrically heated reforming reactor 408 and a second portion 25b of the feed gas 25 leading to the steam methane reforming reactor 404.

[0119] The first catalyst in the electrically heated reforming reactor 408, the second catalyst in the steam methane reforming reactor 404 and the third catalyst in the autothermal reformer 409 are steam methane reforming catalysts arranged to catalyze the steam methane reforming reactions in the electrically heated reforming reactor 408, the steam methane reforming reactor 404 and the autothermal reformer 409.

[0120] The first portion 25a and the second portion 25c of the feed gas 25 are thus subjected to steam methane reforming in the electrically heated reforming reactor 408 and the steam methane reforming reactor 404, respectively. The electrically heated reforming reactor 408 produces a first synthesis gas 30a and the steam methane reforming reactor 404 produces a second synthesis gas 30b. The first synthesis gas 30a and the second synthesis gas 30b are combined into a synthesis gas stream 31, which is introduced into the autothermal reforming reactor 409. A stream 26 of an oxidant gas, such as oxygen or air, also enters the autothermal reforming reactor 409. The self-reforming gas stream 30 leaves the autothermal reformer 409. The self-reforming gas stream 30 is a combined synthesis gas stream 30 leaving the reforming section 410. The combined synthesis gas stream 30 is cooled in the heat exchanger 413 to a cooled combined synthesis gas stream 30'.

[0121] The cooled combined synthesis gas stream 30' enters a gas separation unit 414. The gas separation unit 414 comprises a flash separation unit 415 and a downstream PSA unit 416. The cooled water-gas shift synthesis gas 32' thus enters the flash separation unit 415, which is arranged to separate the cooled water-gas shift synthesis gas 32' into water 27 and a dry synthesis gas 34. The dry synthesis gas 34 enters the PSA unit 416, which is arranged to separate the dry synthesis gas 34 into a product synthesis gas 40 in the form of a hydrogen and carbon monoxide stream, and an off-gas 45. The off-gas 45 is recycled as fuel to the burner 403 of the steam methane reforming reactor 404. This off-gas 45 is combined with a small amount of natural gas 46 to form a fuel gas 47, which is sent to the burner 403 of the steam methane reforming reactor 404. The fuel gas 47 is burned in the burner 403, thereby heating the tubes 407 with the second catalyst. In preheating section 405, flue gas from burner 403 provides heat for preheating the feed gas and is exhausted from preheating section 405 as flue gas 48. Heat exchange fluid 20, such as water, is used for heat exchange in heat exchanger 411 and heated heat exchange fluid, such as steam, is output as stream 20'.

[0122] It should be noted that the syngas plant 400 typically includes other devices, such as compressors, heat exchangers, etc.; however, Figure 4 Such other devices are not shown.

[0123] Embodiment 1:

[0124] Table 1 shows the Figure 1An example of a hydrogen plant 100 is shown, indicating the gas composition at relevant points in the hydrogen plant. This example illustrates how the electrically heated reforming reactor 108, i.e. the first reformer, is integrated with the combustion reforming reactor 104. In the given case, 12% of the feed to the reforming section is sent to the electrically heated reforming reactor, while the remaining 88% is sent to the combustion reforming reactor. After post-treatment in the water-gas shift unit 112 and product purification in the gas separation unit 114, 104193 Nm 3 / h hydrogen. The product purification in the PSA 116 of the gas separation unit 114 produces an off-gas 45 which in this case provides the major portion of the load for the combustion reforming reactor 104 .

[0125] Table 1

[0126]

[0127] Embodiment 2:

[0128] A comparative example is shown in Table 2, which is a more conventional hydrogen production plant using only a single reforming reactor in the form of a fired steam methane reformer. Figure 1 Comparing the case of the hydrogen production plant 100 shown in Table 1 with the case of a more conventional hydrogen production plant shown in Table 2, it can be seen that, as shown by the 40658 Nm in the flow "entering the pre-reformer" and "input fuel", 3 / h combined CH4 feed, both plants use the same amount of natural gas. However, compared to the 100000 Nm 3 / h compared to 104193Nm in Table 1 3 / h of hydrogen product. Thus, by the present invention, a higher hydrogen yield can be obtained from a given amount of natural gas, because less natural gas is used for heating. In the case where the electricity to drive the electrically heated reforming reactor comes from a sustainable source or excess steam from a self-produced hydrogen plant, the present invention achieves a hydrogen production route with less CO2 emissions. This can be seen from the carbon in the fuel, which is 0.40 mol CO2 / mol H2 in the example of Table 1, but 0.42 mol CO2 / mol H2 in the example of Table 2.

[0129] Table 2

[0130]

[0131]

[0132] The advantage of the embodiment of Example 1 over the embodiment of Example 2 is not simply a result of using two reformers in parallel compared to one reactor. Thus, with two parallel fired steam methane reformers, the hydrogen production yield from a given amount of natural gas is as low or even lower than in the embodiment of Example 2 because two parallel fired reformers will require at least the same amount of fuel, and possibly a higher amount of fuel, to heat the reformers compared to a single fired reformer.

Claims

1. A synthesis gas device for producing synthesis gas, the synthesis gas device comprising: a reforming section arranged to receive a feed gas comprising hydrocarbons and to provide a combined synthesis gas, wherein the reforming section comprises: - an electrically heated reforming reactor containing a first catalyst, said electrically heated reforming reactor being arranged to receive a first portion of said feed gas comprising hydrocarbons and to produce a first synthesis gas stream, a combustion reforming reactor connected in parallel with the electrically heated reforming reactor, the combustion reforming reactor comprising one or more tubes containing a second catalyst, the combustion reforming reactor further comprising one or more burners for providing heat to the one or more tubes; the one or more tubes being arranged to receive a second portion of the feed gas comprising hydrocarbons and output a second synthesis gas stream, wherein the reforming section is arranged to output a combined synthesis gas stream comprising the first and / or second synthesis gas stream or a portion thereof, a gas separation unit arranged to separate said combined synthesis gas stream into at least condensate, product synthesis gas and off-gas, and - means for recycling at least a portion of said exhaust gases from said gas separation unit to said one or more burners, wherein the outlet temperature of the combustion reformer reactor is controlled by adjusting the split of the first portion of the feed gas entering the electrically heated reformer reactor relative to the second portion of the feed gas entering the combustion reformer, wherein the outlet temperature of the combustion reformer reactor is increased by reducing the flow of the second portion of the feed gas to the combustion reformer reactor and increasing the flow of the first portion of the feed gas to the electrically heated reformer reactor, or vice versa, and the first synthesis gas flow is balanced by increasing or decreasing the power input to the electrically heated reformer reactor to provide a constant combined synthesis gas flow output; wherein the electrically heated reformer reactor comprises: a pressure shell housing an electric heating unit arranged to heat said first catalyst, wherein said first catalyst comprises a catalytically active material operable to catalyze steam reforming of said first portion of said feed gas, wherein said pressure shell has a design pressure of 5 to 45 bar, - a thermal insulation layer adjacent to at least a portion of the interior of the pressure vessel, and - at least two conductors electrically connected to the electric heating unit and to a power source placed outside the pressure vessel, wherein the power source is sized to heat at least a portion of the first catalyst to a temperature of at least 500° C. by passing an electric current through the electric heating unit; and The electric heating unit comprises a macroscopic structure of a conductive material, the macroscopic structure carries a ceramic coating and the ceramic coating carries the catalytically active material.

2. The synthesis gas plant according to claim 1, wherein the synthesis gas plant further comprises: - a post-treatment unit downstream of the reforming section, wherein the post-treatment unit is arranged to receive the combined synthesis gas stream and to provide a post-treated synthesis gas stream; and The post-treated synthesis gas stream is separated by a gas separation unit into at least a condensate, a product synthesis gas and an off-gas, wherein at least a portion of the off-gas is recycled to the one or more combustors.

3. The synthesis gas device according to claim 1 or 2, wherein the reforming section further comprises an autothermal reforming reactor located downstream of the electrically heated reforming reactor and the combustion reforming reactor, wherein the autothermal reforming reactor comprises a third catalyst and is arranged to receive the first and / or second synthesis gas or a portion thereof and provide a self-reformed synthesis gas flow, wherein the self-reformed synthesis gas is output from the reforming section as at least a portion of the combined gas flow.

4. A synthesis gas device according to claim 1 or 2, wherein the reforming section also includes a gas-heated steam methane reforming reactor connected in parallel with the electrically heated reforming reactor and the combustion reforming reactor, wherein the gas-heated steam methane reforming reactor includes a fourth catalyst and is operable to receive a third portion of a feed gas containing hydrocarbons and utilize at least a portion of the first and / or second synthesis gas streams as a heating medium for heat exchange within the gas-heated steam methane reforming reactor, and the gas-heated steam methane reforming reactor is arranged to produce a third synthesis gas stream and output the third synthesis gas stream from the reforming section as at least a portion of the combined synthesis gas stream.

5. The synthesis gas device according to claim 3, wherein the reforming section further comprises a gas-heated steam methane reforming reactor connected in parallel with the electrically heated reforming reactor, the combustion reforming reactor and the autothermal reforming reactor, wherein the gas-heated steam methane reforming reactor comprises a fourth catalyst and is operable to receive a third portion of a feed gas containing hydrocarbons and utilize at least a portion of the self-reformed synthesis gas flow as a heating medium for heat exchange within the gas-heated steam methane reforming reactor, and the gas-heated steam methane reforming reactor is arranged to produce a third synthesis gas flow and output the third synthesis gas flow from the reforming section as at least a portion of the combined synthesis gas.

6. A synthesis gas plant according to claim 1 or 2, wherein the post-treatment unit is a post-conversion unit, the post-conversion unit having an inlet allowing heated CO2 to be added to the combined synthesis gas flow upstream of the post-conversion unit and accommodating a fifth catalyst, the fifth catalyst having activity in catalyzing steam methane reforming, methanation and reverse water gas shift.

7. The synthesis gas plant according to claim 1 or 2, wherein the post-treatment unit is a water-gas shift unit arranged to perform a water-gas shift reaction.

8. The synthesis gas plant according to claim 1 or 2, wherein the combustion reforming reactor is a steam methane reforming reactor.

9. The synthesis gas plant according to claim 1 or 2, wherein the combustion reforming reactor is a convection reforming reactor, wherein the flue gas from the one or more burners is used as a heat exchange medium within the convection reforming reactor.

10. A method for producing synthesis gas in a synthesis gas plant, the synthesis gas plant comprising a reforming section, the reforming section comprising an electrically heated reforming reactor containing a first catalyst, a combustion reforming reactor connected in parallel with the electrically heated reforming reactor, the combustion reforming reactor comprising one or more tubes containing a second catalyst, the combustion reforming reactor further comprising one or more burners arranged to provide heat for a steam methane reforming reaction in the one or more tubes, the method comprising the following steps: - introducing a first portion of a feed gas comprising hydrocarbons into said electrically heated reforming reactor and subjecting it to steam methane reforming to provide a first synthesis gas stream, - introducing a second portion of the feed gas comprising hydrocarbons into said combustion reforming reactor and subjecting it to steam methane reforming to provide a second synthesis gas stream, - supplying fuel gas to the one or more burners to provide heat for the steam methane reforming reaction within the one or more tubes of the combustion reforming reactor, - outputting from said reforming section a combined synthesis gas stream comprising said first and / or second synthesis gas stream or a portion thereof, - separating the combined synthesis gas stream into condensate, product synthesis gas and waste gas in a gas separation unit, and - recirculating at least a portion of the exhaust gas from the gas separation unit to the one or more burners as fuel gas; wherein the outlet temperature of the combustion reformer reactor is controlled by adjusting the split between the first portion of the feed gas entering the electrically heated reformer reactor and the second portion of the feed gas entering the combustion reformer, wherein the outlet temperature of the combustion reformer reactor is increased by reducing the flow of the second portion of the feed gas to the combustion reformer reactor and increasing the flow of the first portion of the feed gas to the electrically heated reformer reactor, and vice versa, and the first synthesis gas flow is balanced by increasing or decreasing the power input to the electrically heated reformer reactor to provide a constant combined synthesis gas flow output; and, wherein the electrically heated reformer reactor includes a pressure shell containing an electric heating unit, the electric heating unit being arranged to heat the first catalyst, wherein the first catalyst includes a catalytically active material operable to catalyze steam reforming of the first portion of the feed gas, wherein the pressure shell has a design pressure of 5 to 45 bar, - a thermal insulation layer adjacent to at least a portion of the interior of the pressure vessel, and - at least two conductors electrically connected to the electric heating unit and to a power source placed outside the pressure vessel, The method further comprises the following steps: - pressurizing said first portion of the feed gas to a pressure of 5 to 45 bar upstream of said electrically heated reforming reactor, - passing an electric current through the electric heating unit, thereby heating at least a portion of the first catalyst to a temperature of at least 500° C.; and The electric heating unit comprises a macroscopic structure of a conductive material, the macroscopic structure carries a ceramic coating and the ceramic coating carries the catalytically active material.

11. The method according to claim 10, wherein the method further comprises the following steps: - post-treating the combined synthesis gas stream in a post-treating unit downstream of the electrically heated reforming reactor and the combustion reforming reactor to provide a post-treated synthesis gas stream, - separating the post-treated synthesis gas stream into condensate, product synthesis gas and waste gas in a gas separation unit downstream of the post-treatment unit, and - Recirculating at least part of the exhaust gases to the one or more burners as fuel gas.

12. The method according to claim 10 or 11, wherein the reforming section further comprises an autothermal reforming reactor located downstream of the electrically heated reforming reactor and the combustion reforming reactor, wherein the method further comprises the following steps: - introducing the first and / or second synthesis gas or a portion thereof into the autothermal reforming reactor, - introducing an oxidant gas into said autothermal reforming reactor, - generating a self-reforming synthesis gas stream over a third catalyst in said autothermal reforming reactor, and - exporting the self-reformed synthesis gas from the reforming section as a combined gas stream.

13. The method according to claim 10 or 11, wherein the reforming section further comprises a gas-heated steam methane reforming reactor connected in parallel with the electrically heated reforming reactor and the combustion reforming reactor, wherein the gas-heated steam methane reforming reactor comprises a fourth catalyst, and the method further comprises the following steps: - introducing a third portion of a feed gas comprising hydrocarbons into said gas heated steam methane reforming reactor, - utilizing at least part of said first and / or second synthesis gas stream as a heating medium for heat exchange in said gas heated steam methane reforming reactor, - producing a third synthesis gas stream over a fourth catalyst in a gas heated steam methane reforming reactor, and - outputting the third synthesis gas stream from the reforming section as at least a part of the combined synthesis gas.

14. The method according to claim 12, wherein the reforming section further comprises a gas-heated steam methane reforming reactor connected in parallel with the electrically heated reforming reactor, the combustion reforming reactor and the autothermal reforming reactor, wherein the gas-heated steam methane reforming reactor comprises a fourth catalyst, and the method further comprises the following steps: - introducing a third portion of a feed gas comprising hydrocarbons into said gas heated steam methane reforming reactor, - utilizing at least part of said self-reforming synthesis gas stream as a heating medium for heat exchange in said gas-heated steam methane reforming reactor, - producing a third synthesis gas stream over a fourth catalyst in a gas heated steam methane reforming reactor, and - outputting the third synthesis gas stream from the reforming section as at least a part of the combined synthesis gas.

15. The method according to claim 10 or 11, wherein the post-treatment unit is a post-conversion unit accommodating a fifth catalyst for catalyzing steam methane reforming, methanation and reverse water gas shift reactions.

16. The method according to claim 10 or 11, wherein the post-treatment unit is a water-gas shift unit arranged to perform a water-gas shift reaction.

17. The method of claim 10 or 11, wherein the first portion of the feed gas is 5-20% by volume of the feed gas.

18. The method of claim 13, wherein the first portion of the feed gas is 5-10% by volume of the feed gas, and the third portion of the feed gas is 5-10% by volume of the feed gas.

19. The method of claim 14, wherein the first portion of the feed gas is 5-10% by volume of the feed gas, and the third portion of the feed gas is 5-10% by volume of the feed gas.

20. The method of claim 17, wherein the first portion of the feed gas is 5-10% by volume of the feed gas, and the third portion of the feed gas is 5-10% by volume of the feed gas.

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