Process and system for producing one or more olefins

Abstract

The invention relates to a process (100, 200) for producing one or more olefins (103), in which one or more paraffins are reacted in one or more reaction steps (10) to obtain a product mixture (102), in which the one or more reaction steps (10) are carried out using heat of combustion, in which the product mixture (102) comprises one or more olefins, hydrogen and methane, in which the one or more olefins are reacted in one or more reaction steps (10). A tail gas (112) is formed using the product mixture (102) or a portion of the product mixture (102) in one or more separation steps (20, 21), where the tail gas (112) is substantially free of one or more olefins and comprises hydrogen and methane from the product mixture (102) or a portion of the product mixture (102), where the tail gas (112) or a portion of the tail gas (112) is permanently discharged from the process (100), where the tail gas (112) or the portion of the tail gas (112) is substantially free of one or more olefins and comprises hydrogen and methane from the product mixture (102) or the portion of the product mixture (102). The heat of combustion is provided using a fuel gas (111) wherein the molar ratio of hydrogen to methane in the tail gas (112) is at least as high as in the product mixture (102) and is lower in the fuel gas (111) in the tail gas (112), and wherein a flue gas (121) comprising carbon dioxide is formed during the provision of the heat of combustion and wherein the flue gas (121) or a portion of the flue gas (121) is subjected to carbon dioxide capture (30). The invention also relates to a corresponding system.

Description

[0001] The present invention relates to a process and system for producing one or more olefins. Background Art

[0002] Processes and systems for producing olefins, in particular olefins from alkanes, are known. Reference may be made, inter alia, to the articles “ethylene” and “propylene” in the Ullmann Encyclopedia of Industrial Chemistry (published online on April 15, 2009 and September 16, 2013).

[0003] The processes and systems for producing olefins can be highly selective, which means, for example, that more than 75 mol.% of the carbon in the feed used can end up in the desired product, while the carbon content in by-products such as methane is very low. The corresponding processes can be endothermic and non-oxidative, i.e., the energy can be supplied via a separate energy source. Heating can be done using electric current or burning fuel, although there are different variants for each method. The invention is not limited to a specific variant.

[0004] In addition to direct resistive heating of the catalyst itself or of the support to which the catalyst is applied (e.g. by coating), the resistive heating elements can also be used for heating by means of an electric current. It is also possible to electrically superheat the process gas, which then flows through the catalyst bed (if a catalyst is used) at an elevated temperature. In this case, an adiabatic reaction is carried out. It is also possible to provide several corresponding superheating steps and subsequent adiabatic catalyst beds in series.

[0005] In addition to direct heating, in which the heating medium (e.g. heating elements, heating sleeves or resistively heated catalyst supports) is in contact with the process gas or the reaction tube material through which the process gas flows, indirect electrical heating can also be used, as described in WO 2020 / 002326 A 1 and is already known from earlier publications.

[0006] This indirect electrical heating can be carried out using an electrical radiant heating element suitable for heating to the high temperatures required for the reaction, the heating element being arranged not in direct contact with the reaction tube. The heat transfer occurs mainly or entirely in the form of radiant heat.

[0007] Combustion heating can be carried out in a furnace or heat exchanger with a radiation zone, wherein burners of different numbers, positions and arrangements can be used in the combustion chamber, the burners can be operated with a variety of fuel gases, other combustible media can be added or not, and fuel gases or combustion air or other oxygen-containing gas mixtures for combustion can be heated or not. It is also possible to intermittently heat the catalyst bed by oxidation or use a fluidized bed reactor with a separate reaction chamber and combustion chamber. For example, in the convection zone, heat recovery can also be carried out. This heat recovery can be used, for example, for preheating raw materials, generating steam, steam heating, air preheating, etc.

[0008] Paraffins or other carbon-containing feedstocks used to produce olefins are also suitable for generating hydrogen during the reaction. This applies, for example, to paraffinic compounds having 2 to 4 carbon atoms, but also to a certain extent to long-chain hydrocarbons, such as methanol or ethanol.

[0009] In the product mixture of such a process, the so-called C1minus fraction contains relatively less methane and relatively more hydrogen. A typical example is 80 mol.% hydrogen and 20 mol.% methane. The C1minus fraction contains in particular compounds with one carbon atom, which may include carbon monoxide and carbon dioxide, the aforementioned methane, and lighter compounds (such as the aforementioned hydrogen).

[0010] Corresponding values ​​apply, for example, to so-called gas crackers, ie cracking furnaces designed for the dehydrogenation of gaseous feedstocks and propane in the steam cracking process.

[0011] Basically, the above process can produce highly selective olefins and C1minus "energy streams" (so named because the typical use is combustion, i.e. energy use) with low so-called carbon dioxide intensity. In the case of propane dehydrogenation, the stream may also contain, for example, a small amount of hydrocarbons with two carbon atoms. Hereinafter, the stream is referred to as tail gas. The stream usually includes all or most of, in particular, more than 90% or 95% of all components of the corresponding type of the product mixture from the corresponding process.

[0012] The term CO2 intensity relates to the amount of CO2 produced by the combustion of a gas, gas mixture or other fuel. For example, a methane stream without hydrogen (e.g. natural gas, assuming a 100% methane content for simplicity) has a CO2 intensity of about 0.2 tons of CO2 per hour per MW based on lower heating value. On the other hand, a tail gas of the type described (e.g. containing 80 mol.% hydrogen and 20 mol.% methane) has a CO2 intensity of only about 0.09 tons of CO2 per hour per MW based on lower heating value.

[0013] Typically, the corresponding tail gas is intended to be used directly for underfiring in a process or system for producing olefins. Simply put, if the energy consumption of any such process or system is assumed to be the same (in gigajoules per ton of value of product), the CO2 intensity of a process with hydrogen-rich tail gas underfiring is only 45% compared to a process with methane underfiring. This can be a decisive advantage. As shown above, highly selective processes for producing olefins generally have lower CO2 production, such as 0.4 tons of CO2 or even less per ton of value of product.

[0014] However, if the goal is to reduce direct carbon emissions ("scope 1" emissions) as much as possible (eg by 95%), corresponding processes may present difficulties. It is therefore an object of the present invention to provide an advantageous solution for such situations. Summary of the invention

[0015] Against this background, the present invention provides a process and a system for obtaining one or more olefins, which process and system have the characteristics described in the independent claims. Embodiments are subject matter of the dependent claims and of the following description.

[0016] As noted above, it can be seen that the above-described processes for producing olefins already have very low specific direct ("scope 1") carbon dioxide emissions. However, these emissions are particularly difficult to reduce completely.

[0017] Full electrification of the entire energy supply, including the reactors used, is not yet commercially available or may be cost prohibitive. In principle, underfiring with a hydrogen-rich combustion medium (about 99 mol.% to 100 mol.% hydrogen) could be suitable for reducing such emissions. A first option is to extract the hydrogen from the above-mentioned tail gas, in which the methane must then be captured. However, even if the process is highly energy-optimized, the hydrogen in the tail gas is often not sufficient to cover the energy requirements. For example, in a typical gas cracker, the hydrogen is sufficient to cover about 50% of the energy supply.

[0018] It is therefore reasonable to first try to optimize the energy use of the process, especially with the help of partial electrification. Finally, an additional supply of hydrogen is needed. In particular, the production of so-called "green" hydrogen by electrolysis of water using renewable energy sources can be considered. However, this option can be costly and energy-intensive. On the other hand, it is also possible to use "blue" hydrogen, for example hydrogen produced from the separation of carbon dioxide from flue gases (carbon capture) from methane reforming. However, this variant also leads to significant heat losses of the methane used and is more expensive.

[0019] Emissions can be reduced by separating CO2 from the flue gases of the combustion processes or equipment used in the olefin production process (cracking furnaces, fired heaters, boilers, catalyst regenerators, etc.), rather than reducing the CO2 content in the flue gases in advance. However, in the corresponding flue gases, the pressure / partial pressure of CO2 is very low, and the combustion of a high proportion of hydrogen further reduces the pressure / partial pressure of CO2.

[0020] The present invention now at least partially solves these problems by deliberately avoiding the combustion of hydrogen-rich tail gas, instead burning methane or hydrocarbon-rich fuels, and releasing the tail gas or hydrogen from the tail gas, in particular to the system boundary. At first glance this may seem counterintuitive, since avoiding all carbon dioxide formation would initially seem desirable, but this is precisely what the present invention does not propose.

[0021] Therefore, the solution proposed herein is completely opposite to the prior art solutions for producing a hydrogen-rich fuel gas stream.

[0022] For example, WO 2023 / 049570 A1 proposes to produce a hydrogen-rich fuel gas stream by reforming a hydrocarbon-containing feed and subjecting the resulting process gas to a water / gas shift and carbon dioxide separation. According to the embodiments cited therein, the remaining hydrogen-rich stream can advantageously be burned to provide thermal energy.

[0023] EP 3,249,027 A1 proposes a process for producing olefins by steam cracking using one or more tubular reactors. The tubular reactor or at least one of the multiple tubular reactors is heated using combustion heat generated by burning at least one fuel and electric heat generated by electrical energy. However, it is not proposed to discharge a hydrogen-rich stream from the process, but to burn the hydrogen-rich stream.

[0024] The present invention generally comprises the reaction of a paraffinic feed, which generally mainly comprises or only comprises hydrocarbons having 2 to 4 carbon atoms. For example, ethane, propane or liquefied petroleum gas (LPG) can be used. In order to obtain olefins, in particular ethylene and propylene, a product mixture comprising these olefins is formed. The product gas also comprises at least methane and hydrogen, wherein the molar ratio of hydrogen to methane is greater than 0.4, in particular greater than 1, further in particular greater than 2 or greater than 4. The energy demand of the process is at least partially met by underburned hydrocarbons or hydrogen or a mixture thereof.

[0025] Within the scope of the invention, a product fraction is subsequently discharged from the process and / or released at the system boundary; the product fraction mainly comprises compounds with one carbon atom and / or lighter compounds. This can be a tail gas or a fraction formed from the tail gas. The molar ratio of hydrogen to methane in the tail gas is at least as high as or higher than the molar ratio of hydrogen to methane in the product mixture. An energy flow, i.e. a fuel gas, is supplied to the process from the outside, i.e. from outside the system boundary, and is used to compensate for underfiring. The molar ratio of hydrogen to methane in the energy flow is lower than the molar ratio of hydrogen to methane in the tail gas and / or in the fraction formed from the tail gas. During underfiring, flue gases are formed, at least part of which is supplied to the carbon capture process.

[0026] The term "essentially" is to be understood here in particular as meaning that in addition to the indicated essential components, other components may be present in the protected composition, material stream, etc., provided that the basic properties of the protected composition are not significantly altered by these other components. For example, a product fraction comprising "essentially compounds with one carbon atom and / or lighter compounds" contains only very small amounts of hydrocarbons with two or more carbon atoms, in particular olefins, so that their release at the system boundary results in only very small losses of valuable products. In particular, the content of such higher hydrocarbons may be less than 1%, 0.1% or 0.01%. Percentages may refer to mole fractions, mass fractions or volume fractions.

[0027] In general, the present invention proposes a process for producing one or more olefins, wherein one or more paraffins are reacted in one or more reaction steps to obtain a product mixture, wherein one or more reaction steps are performed using heat of combustion, wherein the product mixture comprises one or more olefins, hydrogen and methane, wherein the product mixture or a portion of the product mixture is used in one or more separation steps to form a tail gas, wherein the tail gas is essentially free of one or more olefins and comprises hydrogen and methane from the product mixture or a portion of the product mixture, wherein the tail gas or a portion of the tail gas is permanently discharged from the process, wherein the heat of combustion is provided using a fuel gas, wherein the molar ratio of hydrogen to methane is at least as high in the tail gas as in the product mixture and lower in the fuel gas than in the tail gas, wherein a flue gas comprising carbon dioxide is formed during the provision of the heat of combustion, and wherein the flue gas or a portion of the flue gas is subjected to carbon dioxide capture.

[0028] The advantages of the process proposed here are in particular the simplified separation of carbon dioxide from the flue gas due to the higher partial pressure. The difficulties explained previously for achieving complete decarbonization using variants involving electrification and pure hydrogen combustion schemes currently appear to be difficult to overcome or impractical. Therefore, within the scope of the present invention, the removal of carbon dioxide from the flue gas is optimized. The present invention provides surprising synergistic effects.

[0029] The invention comprises the permanent discharge of tail gas or a part of the tail gas from the process. The term "permanent discharge from the process" refers to the discharge of tail gas or a part of the tail gas, in particular with the same hydrogen content as the tail gas, which is not burned in the process to produce heat, or only a small part, such as less than 10%, 5% or 1%. Instead, a fuel gas low in hydrogen or (essentially) free of hydrogen is burned. The tail gas or the corresponding part discharged permanently from the process is released in particular at the system boundary of the system used in the process and is not returned to the process itself or the corresponding system. In this way, the corresponding hydrogen does not "dilute" the flue gas, thereby not increasing the difficulty of carbon dioxide separation.

[0030] For example, in an embodiment of the present invention, a portion of fuel gas or fuel gas can be obtained from a gas supply line (pipeline), and the tail gas or tail gas permanently discharged from the process can be returned to the gas supply line. In this way, the process proposed according to an embodiment of the present invention can capture more carbon dioxide than can be captured by fully internally utilizing hydrogen-rich tail gas. Therefore, a system according to an embodiment of the present invention is used to additionally remove carbon dioxide. At the same time, in a corresponding embodiment of the present invention, an output stream with a lower carbon dioxide intensity can be obtained, which can be used elsewhere. In addition to removing from the same pipeline and returning to the same pipeline or returning to the same pipeline from the same pipeline, it is also possible to remove from a source different from the place where the return occurs.

[0031] In the illustrated embodiment, a natural gas pipeline can be partially decarbonized using a device such as a steam cracker. A feedstock (e.g., methane-rich natural gas) having a CO2 intensity of 0.2 t / h CO2 / MW (calculated as lower heating value) is partially replaced with a tail gas having a CO2 intensity of 0.09 t / h CO2 / MW (calculated as lower heating value). Advantages can be achieved herein (e.g., by validating the process) because, in olefin production, CO2 is not actually released into the atmosphere due to CO2 capture.

[0032] In an embodiment of the present invention, the tail gas or a portion of the tail gas may be subjected to one or more tail gas separation steps to obtain a first tail gas fraction, which is rich in hydrogen and poor in methane compared to the tail gas, and a second tail gas fraction, which is poor in hydrogen and rich in methane compared to the tail gas. In this way, a pure hydrogen product may be provided, in particular, in the form of the first tail gas fraction.

[0033] By separating the methane and hydrogen (at least partially) in an appropriate design, an output stream with a lower CO2 intensity, down to zero CO2 intensity (hydrogen), can be generated. Thus, as long as more than 60% or especially more than 95% of the CO2 is captured from the flue gas, the exported hydrogen will only result in very low direct CO2 emissions ("blue" hydrogen).

[0034] In any case, the first tail gas fraction or a portion of the first tail gas fraction can be discharged permanently from the process, but it is also possible to use the first tail gas fraction or a portion of the first tail gas fraction independently of the fuel gas to provide further combustion heat. Since pure hydrogen combustion is preferred, no carbon dioxide separation is carried out in the resulting off-gas. However, due to the corresponding methane content, the second tail gas fraction or a portion of the second tail gas fraction can be used for "conventional" combustion with subsequent carbon dioxide capture.

[0035] In an embodiment of the invention, one or more tail gas separation steps may include one or more membrane separation steps and / or one or more adsorption separation steps. These may be carried out directly in the separation section or in a separate unit for treating the tail gas. Separation may include compression and cryogenic separation, as well as (vacuum) pressure swing adsorption, membrane processes or a combination of the above processes, as is well known to those skilled in the art.

[0036] As mentioned before, in embodiments of the invention, during carbon dioxide capture, more than 60% or 95% of the carbon dioxide contained in the flue gas or the portion of the flue gas subjected to carbon dioxide capture is captured. This brings about the advantages mentioned above.

[0037] In embodiments of the invention, carbon dioxide capture may be performed using one or more adsorption liquids, which are also known in principle. For example, amines and alkaline cleaning agents may be used alone or in any combination. Alternatively, simple compression and condensation may be provided (in the case of an oxyfuel furnace explained below).

[0038] In embodiments of the invention, the fuel gas or part of the fuel gas can be combusted using an oxygen-enriched oxidant gas. Thus, the oxidant in such a furnace can be enriched with oxygen, or even (almost) entirely oxygen (so-called oxygen-enriched furnaces). In this case, carbon capture from these furnaces becomes particularly easy, since the flue gases consist almost entirely of hydrogen and carbon dioxide.

[0039] If possible, the reaction steps can also be carried out using heat provided by electricity. This reduces the need to import fossil fuels.

[0040] In an embodiment of the present invention, the fuel gas may be a methane-rich gas or gas mixture. For example, it may be fossil methane, such as natural gas, wherein the carbon dioxide formed may be almost completely (e.g., 95%) removed from the flue gas, as described above. Such emission reductions may be accounted for in the olefin product and / or hydrogen-rich outlet stream.

[0041] Biogas supplementation can also be provided. Since the carbon in the biogas is almost completely removed from the flue gas during the carbon capture process, "negative" direct carbon dioxide emissions are generated ("biological carbon dioxide" is captured). These negative emissions can be accounted for in the olefin product and / or the hydrogen-rich outlet stream. The feedstock can also be of fossil, recycled or biogenic origin. The prerequisite is that the feedstock generates a high hydrogen / methane ratio during the reaction.

[0042] The resulting hydrogen-rich stream can have a low pressure if used directly for underfiring. Alternatively, it can have a high pressure if the stream is fed to any hydrogen value chain and / or pipeline. Therefore, the specifications can vary greatly from typical tail gas to 99.9999 mol.% hydrogen.

[0043] A system for producing one or more olefins is designed to: convert one or more paraffins in one or more reaction steps to obtain a product mixture; use combustion heat to carry out the reaction steps; form a product mixture so that the product mixture contains one or more olefins, hydrogen and methane; use the product mixture or a portion of the product mixture in one or more separation steps to form a tail gas; form a tail gas so that the tail gas is essentially free of one or more olefins and contains hydrogen and methane from the product mixture or a portion of the product mixture; permanently discharge the tail gas or a portion of the tail gas from the system; and use a fuel gas to provide combustion heat, wherein the molar ratio of hydrogen to methane in the tail gas is at least as high as in the product mixture and lower in the fuel gas than in the tail gas, wherein a flue gas containing carbon dioxide is formed during the provision of the combustion heat, and wherein the flue gas or a portion of the flue gas is subjected to carbon dioxide capture.

[0044] For further features and advantages of the corresponding system and embodiments of the corresponding system, reference is made to the above description of the process according to the invention and its embodiments, as these descriptions apply equally here.

[0045] The same applies to a system designed for carrying out a process according to any embodiment of the invention.

[0046] Before describing the embodiments of the present invention with reference to the accompanying drawings, some other aspects of the present invention and some other aspects of the embodiments not according to the present invention, which can be used in any combination with the above and below-described embodiments, will be briefly explained.

[0047] In embodiments of the present invention, the separation of methane and hydrogen in the gas cracker can also be used to export methane for purposes including direct export to a pipeline, hydrogen production, methane pyrolysis, synthesis gas production, other processes for producing valuable products, or use in power systems.

[0048] Even if hydrogen and methane are not exported, it makes sense to separate methane and hydrogen in the gas cracker. This separation enables different processes to be underfired with hydrogen or methane. This means that only the CO2 from the methane underfire process needs to be captured.

[0049] Separation of hydrogen and methane can also be performed in combination using appropriately customized furnace designs; and various "hybrid" system designs are contemplated depending on the implementation. Examples include hydrogen furnaces that combine hydrogen combustion with a methane furnace (and optional carbon dioxide capture), hydrogen furnaces that combine hydrogen combustion with a methane oxygen-enriched furnace (and optional carbon dioxide capture), and hydrogen furnaces that combine hydrogen combustion with an electric furnace and export methane to the value chain.

[0050] Even without CO2 capture, biogas can be imported. In this way, energy exports with low CO2 intensity are also possible (but not a negative CO2 balance). BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Embodiments of the present invention are described below by way of example only and with reference to the accompanying drawings, in which:

[0052] Figure 1 A system according to an embodiment of the present invention is shown, and

[0053] Figure 2 A system according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0054] The embodiments described below are only used to help the reader understand the protected and previously discussed features. They are only representative embodiments and are not intended to be exhaustive and / or limit the features of the present invention. It should be understood that the advantages, embodiments, embodiments, functions, features, structures and / or other aspects described above and below should not be regarded as limitations on the scope of the present invention defined in the claims or limitations on the equivalents of the claims, and other embodiments may be adopted and changes may be made without departing from the scope of the present invention defined in the claims.

[0055] Different embodiments of the present invention may include, have, consist of, or consist essentially of other useful combinations of the described elements, components, features, parts, steps, means, etc., even if such combinations are not specifically described herein. In addition, the present disclosure may cover other inventions that are not currently claimed but may be claimed in the future, especially if they are included in the scope of the independent claims.

[0056] Explanations related to the apparatus, device, arrangement, system, etc. according to the embodiments of the present invention may also apply to the methods, processes, procedures, etc. according to the embodiments of the present invention, and vice versa. Elements, process steps, etc. that are the same, have the same effect, correspond to each other in function, are structurally the same, or have comparable structures may be represented by the same reference numerals.

[0057] exist Figure 1 A process according to an embodiment of the present invention is shown in , and generally indicated at 100 .

[0058] Figure 1 The process shown in comprises one or more reaction steps 10, to which a reaction feed 101 is supplied, the composition of which depends on the design of the reaction step 10 and in particular comprises one or more paraffins. The reaction feed 101 is reacted to obtain a product mixture 102, wherein one or more of the processes explained in detail above can be used.

[0059] The reaction step 10 is carried out using the combustion heat provided by the combustion of the methane-containing fuel gas 111. Figure 1 In the embodiment of the process 100 shown, the fuel gas 111 is available from the pipeline 110. During combustion, flue gas 121 is formed, which is subjected to carbon dioxide removal 30. The separated carbon dioxide is referenced here as 122, while the flue gas from which carbon dioxide has been removed is referenced as 123.

[0060] The product mixture 102 comprising one or more olefins, hydrogen and methane is now subjected to one or more separation steps 20, wherein one or more product fractions 103 and a tail gas fraction 112 are formed, wherein the one or more product fractions 103 essentially contain the one or more olefins and the tail gas fraction 112 is essentially free of the one or more olefins and contains at least a portion of the hydrogen and methane from the product mixture.

[0061] An embodiment of the present invention is characterized in that the molar ratio of hydrogen to methane in the tail gas fraction 112 is at least as high as or higher than the molar ratio of hydrogen to methane in the product mixture 102, and the molar ratio of hydrogen to methane in the fuel gas 111 is lower than the molar ratio of hydrogen to methane in the tail gas fraction 112.

[0062] The tail gas 112 is permanently exhausted from the process 100. More specifically, the fuel gas 111 is removed from the gas supply line 110 and the tail gas 112 is returned to the gas supply line 110.

[0063] exist Figure 2 A process according to an embodiment of the present invention is shown in , and generally indicated at 200 .

[0064] like Figure 2 As shown, the tail gas 112 is subjected to a tail gas separation step 21 to obtain a first tail gas fraction 113 and a second tail gas fraction 114, the first tail gas fraction 113 being rich in hydrogen and poor in methane compared to the tail gas 112, and the second tail gas fraction 114 being poor in hydrogen and rich in methane compared to the tail gas 112. The first tail gas fraction 113 or a portion of the first tail gas fraction 113 can be permanently discharged from the process 200, but can also be used for other purposes as described above. The purpose of the second tail gas fraction 114 is also explained.

[0065] For the production of pure hydrogen as a “low-carbon” energy carrier, a very simple example is given below comparing “dedicated” variants for the production of blue hydrogen, such as using autothermal reforming (ATR) and CO2 capture from synthesis gas (Table 1), and a variant using a cracker and CO2 capture according to an embodiment of the invention (Table 2).

[0066] Table 1

[0067] Hydrogen produced MW 100.000 ATR loss <![CDATA[MW H2 / MW CH4]]> 0.750 Methane feed MW 133.333 carbon dioxide <![CDATA[(t / h) / MW CH4]]> 0.197 carbon dioxide t / h 26.311 carbon dioxide <![CDATA[(t / h) / MW H2]]> 0.263

[0068] Table 2

[0069] Hydrogen from crackers MW 100.000 Reduced furnace efficiency <![CDATA[MW H2 / MW CH4]]> 0.979 Methane displacement to furnace MW 102.151 Additional methane for CO2 capture MW 18 Total methane feed MW 120 carbon dioxide <![CDATA[(t / h) / MW CH4]]> 0.197 carbon dioxide t / h 23.710 Total energy of amine scrubbing GJ / tCO2 2.73 carbon dioxide <![CDATA[(t / h) / MW H2]]> 0.237

[0070] According to the "dedicated" variant for the production of blue hydrogen of Table 1, about 133 MW of methane (75% efficiency) is required to produce 100 MW of hydrogen, or 125 MW of methane (80% efficiency) in the best case. A corresponding amount of CO2 must be removed by CO2 capture. The additional small energy gain in the form of exported steam is not taken into account here.

[0071] The integrated variant according to the embodiment of the invention and Table 2 also causes additional energy consumption via carbon dioxide capture, but this energy consumption is lower, about 120MW methane per 100MW hydrogen. This does not take into account that the process significantly simplifies the separation of carbon dioxide from the flue gas (due to the higher partial pressure). In addition, the energy required for separating methane and hydrogen is not taken into account, which, however, is fully electrifiable and is also necessary for the variant shown in Table 1.

[0072] In summary, it can be concluded that according to the variant of the invention, at the same hydrogen yield, at least 10% less thermal energy is required, 10% less carbon dioxide is produced and, moreover, no "dedicated" process (system for the production of blue hydrogen) is required. This is offset by flue gas washing of the steam cracker and separation of methane and hydrogen (which, as mentioned above, is also necessary for other systems). However, this investment pays off both for olefin decarbonization and for a "low-carbon" energy stream. Another positive aspect is that the variant according to the invention causes fewer difficulties during combustion with regard to the formation of nitrogen oxides.

Claims

1. A process (100, 200) for producing one or more olefins (103), wherein: One or more paraffins are reacted in one or more reaction steps (10) to obtain a product mixture (102), wherein the reaction step (10) is performed using heat of combustion, wherein the product mixture (102) comprises the one or more olefins, hydrogen and methane, wherein the product mixture (102) or a portion of the product mixture (102) is used in one or more separation steps (20, 21) to form a tail gas (112), wherein the tail gas (112) is substantially free of the one or more olefins and comprises methane from the product mixture (102) or a portion of the product mixture (102). The hydrogen and the methane, wherein the tail gas (112) or a portion of the tail gas (112) is permanently discharged from the process (100), wherein the heat of combustion is provided using a fuel gas (111), wherein the molar ratio of hydrogen to methane in the tail gas (112) is at least as high as in the product mixture (102) and is lower in the fuel gas (111) than in the tail gas (112), wherein a flue gas (121) containing carbon dioxide is formed during the provision of the heat of combustion, and wherein the flue gas (121) or a portion of the flue gas (121) is subjected to carbon dioxide capture (30).

2. The process (100) according to claim 1, wherein: The fuel gas (111) or a portion of the fuel gas (111) is removed from the gas supply line (110) and the tail gas (112) or a portion of the tail gas (112) permanently discharged from the process is returned to the gas supply line (110).

3. The process (200) of claim 1, wherein: The tail gas (112) or a portion of the tail gas (112) is subjected to one or more tail gas separation steps (21) to obtain a first tail gas fraction (113) and a second tail gas fraction (114), wherein the first tail gas fraction (113) is rich in hydrogen and poor in methane compared to the tail gas (112), and the second tail gas fraction (114) is poor in hydrogen and rich in methane compared to the tail gas (112).

4. The process (200) according to claim 3, wherein: The first tail gas fraction (113) or a portion of the first tail gas fraction (113) is permanently discharged from the process (200).

5. The process (200) of claim 3, wherein: The first tail gas fraction (113) or a portion of the first tail gas fraction (113) is used independently of the fuel gas (111) to provide additional combustion heat.

6. The process (200) according to any one of claims 3 to 5, wherein: The fuel gas (111) contains the second tail gas fraction (114) or a portion of the second tail gas fraction (114).

7. The process (200) according to any one of claims 3 to 6, wherein: The one or more tail gas separation steps (112) include one or more membrane separation steps and / or one or more adsorption separation steps.

8. The process (100, 200) according to any one of the preceding claims, wherein: During the carbon dioxide capture (30), more than 60% of the carbon dioxide contained in the flue gas (121) or a portion of the flue gas (121) subjected to the carbon dioxide capture (30) is captured.

9. The process (100, 200) according to any one of the preceding claims, wherein: The carbon dioxide capture (30) is performed using one or more adsorption liquids.

10. The process (100, 200) according to any one of the preceding claims, wherein: The fuel gas (111) or a portion of the fuel gas (111) is combusted using an oxygen-rich oxidant gas.

11. The process (100, 200) according to any one of the preceding claims, wherein: The one or more reaction steps (10) are also carried out using heat provided by electricity.

12. The process (100, 200) according to any one of the preceding claims, wherein: The fuel gas is a methane-rich gas or a gas mixture.

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