Method and a system for producing one or more olefins

Abstract

The present invention relates to a method (100, 200) for producing one or more olefins (103), wherein one or more paraffins are reacted to obtain a product mixture (102) in one or more reaction steps (10), wherein the reaction step or steps (10) are carried out using heat of combustion, wherein the product mixture (102) contains the one or more olefins, hydrogen and methane, wherein an endgas (112) is formed using the product mixture (102) or a part thereof in one or more separation steps (20, 21), wherein the endgas (112) is substantially free of the one or more olefins and contains the hydrogen and methane from the product mixture (102) or a portion thereof, wherein the endgas (112) or a portion thereof is permanently discharged from the method (100), wherein the heat of combustion is provided using a fuel gas (111), wherein a molar ratio of hydrogen to methane in the endgas (112) is at least as high as in the product mixture (102) and is lower in the fuel gas (111) than in the endgas (112), wherein a flue gas (121) containing carbon dioxide is formed when the heat of combustion is provided, and wherein the flue gas (121) or a part thereof is subjected to carbon dioxide capture (30). The present invention also relates to a corresponding system.

Description

[0001] Description

[0002] Process and plant for producing one or more olefins

[0003] The invention relates to a process and a plant for producing one or more olefins.

[0004] background

[0005] Processes and plants for the production of olefins (alkenes), especially from paraffins (alkanes), are known. Among many others, reference is made to the articles "Ethylene" and "Propylene" in Ullmann's Encyclopedia of Industrial Chemistry, online publications of April 15, 2009, and September 16, 2013, respectively.

[0006] Processes and plants for producing olefins can be highly selective, meaning, for example, more than 75 mol% of the carbon from the feedstock can be converted into the desired product, with little carbon being converted into byproducts such as methane. Such processes can be endothermic and non-oxidative, meaning the energy can be supplied via a separate energy source. Electricity can be used, or a fuel can be burned for heating, with various variants being known for each of these. The present invention is not limited to any specific variant.

[0007] In addition to direct resistive heating of the catalyst itself or a support to which it is applied, for example, by a wash coating, resistive heating elements can also be used for heating with electrical current. Electrical superheating of the process gas can also be performed, which then flows through a catalyst bed at an elevated temperature (if a catalyst is used). This thus implements an adiabatic reaction. Several corresponding superheating steps, followed by adiabatic catalyst beds in series, can also be provided.

[0008] In addition to direct heating, in which the heating medium, for example a heating element, a heating sleeve or a resistively heated catalyst support, is in material contact with the process gas or in material contact with reaction tubes through which the process gas flows, indirect electrical heating can also be used, as explained, among other things, in WO 2020 / 002326 A1, but also already known from earlier publications.

[0009] Such indirect electrical heating can be achieved using electrical radiant heating elements suitable for heating to the high temperatures required for the aforementioned reactions. Such heating elements are arranged such that they are not in direct contact with the reaction tubes. Heat transfer occurs predominantly or exclusively in the form of radiant heat.

[0010] Heating by combustion can take place in a furnace or heat exchanger with a radiant zone, with burners of varying numbers, positions, and arrangements being used within a combustion chamber. These burners can be operated with a wide variety of fuel gases and with or without the addition of other combustible media, and with or without heating the fuel gas or the combustion air used for combustion or other oxygen-containing gas mixtures. Here, too, intermittent heating of a catalyst bed by oxidation or the use of a fluidized-bed reactor with separate reaction chamber and combustion chamber is possible. Heat recovery, for example, in a convection zone, is also possible. This heat recovery can be used, for example, for preheating starting materials, for steam generation, for steam heating, for air preheating, and the like.

[0011] Paraffins or other carbon-containing feedstocks used in the production of olefins can also be suitable for generating hydrogen during the conversion. This applies, for example, to paraffinic compounds with two to four carbon atoms, but possibly also to some extent to long-chain hydrocarbons such as methanol or ethanol.

[0012] A product mixture from such processes contains comparatively little methane and comparatively high levels of hydrogen in the so-called C-minus fraction. Typical values ​​here are, for example, 80 mol% hydrogen and 20 mol% methane. The C-minus fraction primarily comprises compounds with one carbon atom, possibly including carbon monoxide and carbon dioxide, the aforementioned methane, and lighter compounds such as the aforementioned hydrogen. Similar values ​​apply, for example, to so-called gas crackers, i.e., cracking furnaces designed for gaseous feedstocks in steam cracking processes, and propane dehydrogenation.

[0013] In principle, the aforementioned processes produce highly selective olefins and a C1-minus "energy stream" (named due to its typical use for combustion, i.e., energy recovery) with low carbon intensity. In the case of propane dehydrogenation, this stream may also contain, for example, small amounts of hydrocarbons with two carbon atoms. This stream is referred to below as tail gas. It typically comprises all or a significant portion, in particular more than 90% or 95%, of all components of the corresponding type from the product mixture of a corresponding process.

[0014] The term carbon dioxide intensity correlates with the amount of carbon dioxide formed during the combustion of a gas, gas mixture, or other fuel. For example, a hydrogen-free methane stream (e.g., natural gas, simplified to a 100% methane content) has a carbon dioxide intensity of approximately 0.2 tons per hour of carbon dioxide per megawatt, based on the lower calorific value. A tail gas of the type described above, with, for example, 80 mol% hydrogen and 20 mol% methane, has a carbon dioxide intensity of only approximately 0.09 tons per hour of carbon dioxide per megawatt, based on the lower calorific value.

[0015] Typically, the corresponding tail gases are used directly for underfiring in the process or plant for producing olefins. Assuming, in simplified terms, identical energy consumption for any process or plant of this type (in gigajoules per ton of value products), the carbon dioxide intensity of a process underfired with hydrogen-rich tail gas is only 45% compared to a process underfired with methane. This can be a decisive advantage. As shown above, highly selective processes for producing olefins typically have low carbon dioxide production, which can be, for example, 0.4 tonnes of carbon dioxide per ton of value products or even less. However, if the aim is to decarbonise direct emissions (“Scope 1” emissions) as extensively as possible (e.g., by 95%), difficulties may arise in corresponding processes.The present invention therefore aims to provide advantageous solutions for such cases.

[0016] Disclosure of the invention

[0017] Against this background, the present invention proposes a process and a plant for obtaining one or more olefins having the features of the independent patent claims. Further embodiments are the subject of the dependent claims and the following description.

[0018] As already indicated above, it can be seen that the processes for producing olefins described above already have extremely low specific direct (“Scope 1”) carbon dioxide emissions, but these emissions are particularly difficult to reduce completely.

[0019] Full electrification of the entire energy supply, including the reactors used, is not yet commercially available or could prove to be complex. Underfiring with a very hydrogen-rich combustion medium (approximately 99 to 100 mol% hydrogen) would, in principle, be suitable for reducing such emissions. The hydrogen from the aforementioned tail gas, from which the methane content would have to be separated, would be the first option. However, the hydrogen from the tail gas is generally insufficient to cover the energy demand, even if the process is highly energy-optimized. In a typical gas cracker, for example, the hydrogen is sufficient for approximately 50% of the energy supply.

[0020] Plausibly, an energy optimization of the process would first be attempted, particularly with the partial aid of electrification. Finally, an additional supply of hydrogen would be necessary. In particular, so-called "green" hydrogen from water electrolysis powered by renewably generated electricity is a suitable option. However, this option can be very costly and energy-intensive. Alternatively, "blue" hydrogen could also be used, e.g., from methane reforming with carbon capture. This option, however, also involves significant heat losses of the methane used and is costly.

[0021] Instead of an a priori reduction of the carbon dioxide content in the flue gas, emissions can also be reduced by separating carbon dioxide from the flue gas of combustion processes or equipment used in olefin production processes (cracking furnaces, fired heaters, boilers, catalyst regenerators, etc.). However, in such flue gas, the carbon dioxide is present at a very low pressure or partial pressure, which is further reduced by the high proportion of hydrogen combustion.

[0022] The present invention now solves these problems at least partially by deliberately omitting the combustion of the hydrogen-rich tail gas, instead burning methane or a hydrocarbon-rich fuel, and releasing the tail gas or hydrogen from it, particularly at the plant boundary. This seems counterintuitive at first glance, since avoiding all carbon dioxide formation initially seems desirable, which is precisely not what the present invention proposes.

[0023] The solution proposed here is therefore diametrically opposed to state-of-the-art solutions in which hydrogen-rich fuel gas streams are generated.

[0024] For example, WO 2023 / 049570 A1 proposes the production of a hydrogen-rich fuel gas stream by reforming a hydrocarbon-containing feedstock, and subjecting the resulting process gas to a water-gas shift and carbon dioxide separation. According to the disclosure, the remaining hydrogen-rich stream can advantageously be combusted to provide thermal energy.

[0025] 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 tubular reactors, is heated using both combustion heat generated by burning at least one fuel and electroheat generated by means of electrical energy. However, it is not proposed to discharge a hydrogen-rich stream from the process and not to burn it. The invention typically involves the conversion of a paraffinic feedstock, which typically predominantly or exclusively contains hydrocarbons with two to four carbon atoms. For example, ethane, propane, or liquefied petroleum gas (LPG) can be used.To obtain olefins, in particular ethylene and propylene, a product mixture containing these olefins is formed. The product gas also contains at least methane and hydrogen, with a molar ratio of hydrogen to methane of more than 0.4, in particular more than 1, and more particularly more than 2 or more than 4. The energy requirement of the process is at least partially covered by underfiring a hydrocarbon or hydrogen, or a mixture thereof.

[0026] Within the scope of the present invention, a product fraction is now carried out from the process or discharged at the plant boundary, which product fraction essentially comprises compounds with one carbon atom and / or lighter compounds. This can be a tail gas or a fraction formed therefrom. A molar ratio of hydrogen to methane in this tail gas is at least as high as or higher than the molar ratio of hydrogen to methane in the product mixture. An energy stream, i.e. a fuel gas, is fed to the process externally, or from outside the plant boundary, and serves to supplement the underfiring. The molar ratio of hydrogen to methane in this energy stream is lower than that of the tail gas or a fraction formed therefrom. During underfiring, a flue gas is formed, which is at least partially fed to a carbon capture process.

[0027] The statement "essentially" should be understood here in particular to mean that in addition to the components stated as mandatory, further components may be present in a claimed composition, a material stream, etc., provided that the essential characteristics of the claimed composition are not significantly changed by these additional components. For example, a product fraction comprising "essentially compounds with one carbon atom and / or lighter compounds" contains hydrocarbons with two or more carbon atoms, in particular olefins, only in very small quantities, so that their release at the plant boundary results in only very small losses of valuable products. In particular, this may involve less than 1%, 0.1% or 0.01% of such higher hydrocarbons. The percentages can refer to molar, quantitative or volume fractions.

[0028] Overall, the present invention proposes a process for producing one or more olefins, wherein one or more paraffins are reacted to obtain a product mixture in one or more reaction steps, wherein the reaction step(s) are carried out using heat of combustion, wherein the product mixture contains the one or more olefins, hydrogen and methane, wherein a tail gas is formed using the product mixture or a part thereof in one or more separation steps, wherein the tail gas is substantially free of the one or more olefins and contains the hydrogen and the methane from the product mixture or a part thereof, wherein the tail gas or a part thereof is permanently discharged from the process, wherein the heat of combustion is provided using a fuel gas,wherein a 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 heat of combustion, and wherein the flue gas or a part thereof is subjected to carbon dioxide separation.

[0029] The advantages of the process proposed here are, in particular, that the separation of carbon dioxide from the flue gas is simplified due to the higher partial pressure. The previously discussed difficulty of complete decarbonization using the electrification and pure hydrogen firing variants currently appears insurmountable or unrealistic. Accordingly, the present invention optimizes carbon dioxide removal from the flue gas. The present invention provides surprising synergistic effects.

[0030] The present invention comprises the tail gas or a portion thereof being permanently discharged from the process. “Permanently discharged from the process” means that the tail gas or its discharged portion, which in particular has the same hydrogen content as the tail gas, is not combusted in the heat recovery process, or only a small portion of it, for example less than 10%, 5%, or 1%, is combusted. Instead, a low-hydrogen or (essentially) hydrogen-free fuel gas is combusted. A tail gas or a corresponding portion permanently discharged from the process is discharged, in particular, at a plant boundary of a plant used in the process and is not returned to the process itself or a corresponding plant. In this way, corresponding hydrogen does not “dilute” the flue gas and thus cannot complicate carbon dioxide separation.

[0031] For example, in embodiments of the present invention, the fuel gas or a portion thereof can be withdrawn from a gas supply line (pipeline), and the tail gas or the portion thereof permanently discharged from the process can be fed back into the gas supply line. In this way, the process proposed according to embodiments of the present invention can separate a larger amount of carbon dioxide than would be possible with complete internal utilization of the hydrogen-enriched tail gas. A plant according to one embodiment of the present invention thus serves for additional carbon dioxide removal. At the same time, in corresponding embodiments of the invention, an export stream with a lower carbon dioxide intensity is available, which can be made available for use elsewhere.In addition to withdrawal and return from or into the same pipeline, withdrawal may also be provided from a source that is different from a sink into which the return takes place.

[0032] In the illustrated example, a facility such as a steam cracker can, in a sense, be used to partially decarbonize a gas pipeline: The feedstock with a carbon intensity of 0.2 tons per hour of carbon dioxide per megawatt, based on the lower calorific value, such as methane-rich natural gas, is partially replaced by tail gas with a carbon intensity of, for example, 0.09 tons per hour of carbon dioxide per megawatt, based on the lower calorific value. Advantages can be achieved here (e.g., through certification processes), since carbon dioxide is actually not released into the atmosphere during olefin production due to carbon capture.

[0033] In embodiments of the present invention, the tail gas or a portion thereof can be subjected to one or more tail gas separation steps to obtain a first tail gas fraction that is enriched in hydrogen and depleted in methane compared to the tail gas, and a second tail gas fraction that is depleted in hydrogen and enriched in methane compared to the tail gas. In this way, a pure hydrogen product can be provided in the form of the first tail gas fraction.

[0034] Through the (at least partial) separation of methane and hydrogen in appropriate configurations, an export stream with even lower carbon dioxide intensity can be generated, down to zero carbon dioxide intensity (hydrogen). The exported hydrogen can therefore be attributed a very low direct carbon dioxide emission ("blue" hydrogen), provided, for example, more than 60%, or in particular more than 95%, of the carbon dioxide is captured from the flue gases.

[0035] In any case, the first tail gas fraction, or a portion thereof, can be permanently discharged from the process; however, it is also possible to use the first tail gas fraction, or a portion thereof, separately from the fuel gas to provide additional combustion heat. Due to the preferably pure hydrogen combustion, no carbon dioxide separation is performed in the resulting exhaust gas. The second tail gas fraction, or a portion thereof, can, however, be used for "regular" combustion due to its corresponding methane content, downstream of which carbon dioxide capture takes place.

[0036] In embodiments of the present invention, the one or more tail gas separation steps may comprise one or more membrane separation steps and / or one or more adsorptive separation steps. These can take place directly in the separation section or in a separate unit that processes the tail gas. The separation may comprise compression and cryogenic separation, as well as (vacuum) pressure swing adsorption, membrane processes, or a combination of the aforementioned processes, as are generally known to those skilled in the art.

[0037] As already mentioned, in embodiments of the invention, more than 60% or 95% of the carbon dioxide contained in the flue gas or in the portion thereof subjected to carbon dioxide capture can be captured during carbon dioxide capture. This results in the aforementioned advantages.

[0038] In embodiments of the present invention, carbon dioxide capture can be carried out using one or more absorption liquids, as is also generally known. For example, amine and caustic scrubbing can be used alone or in any combination. Alternatively, simple compression and condensation can also be provided (in the case of the oxyfuel furnaces explained below).

[0039] In embodiments of the present invention, the fuel gas, or a portion thereof, can be combusted using an oxygen-enriched oxidizer gas. The oxidant for such furnaces can thus be oxygen-enriched or even (almost) entirely oxygen (so-called oxyfuel furnaces). In this case, carbon capture from these furnaces becomes particularly easy, since the flue gas consists almost entirely of hydrogen and carbon dioxide.

[0040] If available, the conversion step(s) can also be carried out using electrically generated heat. This reduces the need to import fossil fuels.

[0041] In embodiments of the present invention, the fuel gas can be a methane-rich gas or gas mixture. For example, it can be fossil methane, e.g., natural gas, whereby the carbon dioxide formed can be almost completely (e.g., 95%) removed from the flue gas, as described above. This emission reduction can be credited to the olefin product and / or the hydrogen-rich export stream.

[0042] Biogas supplementation may also be considered. Since the carbon from the biogas is almost completely removed from the flue gas during carbon capture, this generates "negative" direct carbon dioxide emissions ("biocarbon dioxide" is captured). These negative emissions can be attributed to the olefin product and / or the hydrogen-rich export stream. The feedstock can also be of fossil origin or could be from a circular or biogenic source. The prerequisite is that this feedstock produces a high hydrogen / methane ratio during conversion.

[0043] A resulting hydrogen-rich stream can be low-pressure if used directly for underfiring. Alternatively, it can be high-pressure if fed into any hydrogen value chain and / or pipeline. Accordingly, specifications can vary considerably, from typical tail gas to 99.9999 mol% hydrogen.

[0044] A plant for producing one or more olefins is designed to convert one or more paraffins to obtain a product mixture in one or more conversion steps, to carry out the conversion step(s) using heat of combustion, to form the product mixture in such a way that it contains the one or more olefins, hydrogen and methane, to form a tail gas using the product mixture or a part thereof in one or more separation steps, to form the tail gas in such a way that it is substantially free of the one or more olefins and contains the hydrogen and methane from the product mixture or a part thereof, to permanently discharge the tail gas or a part thereof from the plant, and to provide the heat of combustion using a fuel gas,wherein a 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 heat of combustion, and wherein the flue gas or a part thereof is subjected to carbon dioxide separation.

[0045] For further features and advantages of a corresponding system and embodiments thereof, reference is expressly made to the above explanations concerning the method proposed according to the invention and its embodiments, since these apply equally to this.

[0046] The same applies to a system which is designed to carry out a method according to any embodiment of the present invention.

[0047] Before describing embodiments of the invention with reference to the accompanying drawings, some further aspects of the invention and of embodiments not according to the invention will be briefly explained, which can be used in any combination with the embodiments explained above and below.

[0048] In embodiments of the invention, a separation of methane and hydrogen in a gas cracker can also serve the purpose of exporting methane, with the objective of, among other things, direct export into a pipeline, hydrogen production, methane pyrolysis, synthesis gas production, other processes for the production of valuable products or use in a power plant.

[0049] Separating methane and hydrogen in a gas cracker can be useful even if neither hydrogen nor methane is exported. Separation allows various processes to be fired with either hydrogen or methane. This means that only the carbon dioxide from the methane-fired processes needs to be captured.

[0050] The separation of hydrogen and methane can also be achieved in combination with the use of appropriately tailored furnace designs, and various "hybrid" plant designs can be envisaged depending on the configuration. Examples include hydrogen furnaces with hydrogen firing combined with methane furnaces (and optional carbon dioxide capture), hydrogen furnaces with hydrogen firing combined with methane oxyfuel furnaces (and optional carbon dioxide capture), and hydrogen furnaces with hydrogen firing combined with an electric furnace and methane export to a value chain.

[0051] Biogas can be imported even if no carbon capture is carried out. This would also allow energy export with low carbon intensity (but not a negative carbon footprint).

[0052] Short description of the drawing

[0053] Embodiments of the invention are described below purely by way of example with reference to the accompanying drawings, in which

[0054] Figure 1 illustrates a system according to an embodiment of the invention, and

[0055] Figure 2 illustrates a system according to an embodiment of the invention.

[0056] Embodiments of the invention

[0057] The embodiments described below are described solely for the purpose of assisting the reader in understanding the claimed and previously discussed features. They are merely representative examples and are not intended to be exhaustive and / or limiting with regard to the features of the invention. It is to be understood that the advantages, embodiments, examples, functions, features, structures, and / or other aspects described above and below are not to be considered as limitations on the scope of the invention as defined in the claims or as limitations on equivalents to the claims, and that other embodiments may be utilized and changes may be made without departing from the scope of the claimed invention.

[0058] Different embodiments of the 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.

[0059] Furthermore, the disclosure may cover other inventions which are not currently claimed but which may be claimed in the future, particularly if they are included within the scope of the independent claims.

[0060] Explanations relating to devices, apparatus, arrangements, systems, etc. according to embodiments of the present invention may also apply to methods, processes, methods, etc. according to the embodiments of the present invention, and vice versa. Elements, method steps, etc. that are identical, have the same effect, are functionally equivalent, are structurally identical, or are comparable may be identified by identical reference numerals.

[0061] Figure 1 illustrates a method according to an embodiment of the present invention and is designated overall by 100.

[0062] The process illustrated in Figure 1 comprises one or more conversion steps 10, to which a reaction feed 101 is fed, which is composed depending on the design of the conversion step(s) 10 and in particular contains one or more paraffins. The reaction feed 101 is converted to obtain a product mixture 102, wherein one or more of the processes explained in detail above can be used. The conversion step(s) 10 are carried out using combustion heat provided by the combustion of a methane-containing fuel gas 111, which in the example of the process 100 illustrated in Figure 1 can be taken from a pipeline 110. During combustion, a flue gas 121 is formed, which is subjected to carbon dioxide removal 30. Carbon dioxide separated here is designated 122, and a flue gas depleted in carbon dioxide is designated 123.

[0063] The product mixture 102, which contains one or more olefins, hydrogen and methane, is then subjected to one or more separation steps 20, wherein one or more product fractions 103, which essentially contain(s), and a tail gas fraction 112, which is essentially free of the one or more olefins and contains at least a portion of the hydrogen and methane from the product mixture, are formed.

[0064] Embodiments of the present invention are characterized in that a molar ratio of hydrogen to methane in the tail gas fraction 112 is at least as high as or higher than a molar ratio of hydrogen to methane in the product mixture 102, and that a molar ratio of hydrogen to methane in the fuel gas 111 is lower than that of the tail gas fraction 112.

[0065] The tail gas 112 is permanently discharged from the process 100. More specifically, the fuel gas 111 is taken from a gas supply line 110, and the tail gas 112 is fed back into the gas supply line 110.

[0066] Figure 2 illustrates a method according to an embodiment of the present invention and is designated overall by 200.

[0067] As illustrated in Figure 2, the tail gas 112 is subjected to a tail gas separation step 21 to obtain a first tail gas fraction 113, which is enriched in hydrogen and depleted in methane compared to the tail gas 112, and a second tail gas fraction 114, which is depleted in hydrogen and enriched in methane compared to the tail gas 112. The first tail gas fraction 113 or a portion thereof can be permanently discharged from the process 200, but other uses as previously explained are also possible. The use of the second tail gas fraction 114 has also been explained.For the production of pure hydrogen as a “low-carbon” energy carrier, a very simplified example is presented below comparing an “on-purpose” variant for the production of blue hydrogen using, for example, autothermal reforming (ATR) and carbon dioxide capture from the synthesis gas (Table 1) and a variant according to an embodiment of the invention using a cracker and carbon dioxide capture (Table 2).

[0068] Table 1

[0069] Table 2

[0070] The "on-purpose" variant for producing blue hydrogen, as shown in Table 1, requires approximately 133 MW of methane (75% efficiency) for 100 MW of hydrogen, or, in the best case, 125 MW (80% efficiency). The corresponding amounts of carbon dioxide must be removed by carbon dioxide capture. This does not take into account the additional small energy gain in the form of export steam.

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

[0072] In summary, it can be concluded that the variant according to the invention requires at least 10% less thermal energy and produces 10% less carbon dioxide for the same amount of hydrogen production and, moreover, no “on purpose” process (plant for the production of blue hydrogen) is required.

[0073] This is offset by the flue gas scrubbing for the steam cracker and the separation of methane and hydrogen (which, as mentioned, would also be required for the other plant). However, this investment pays off both for the decarbonization of the olefin and the "low-carbon" energy stream. Another positive aspect is that the variant according to the invention causes fewer problems with the formation of nitrogen oxides during combustion.

Claims

A process (100, 200) for producing one or more olefins (103), wherein one or more paraffins are reacted to obtain a product mixture (102) in one or more reaction steps (10), wherein the reaction step(s) (10) are carried out using heat of combustion, wherein the product mixture (102) contains the one or more olefins, hydrogen, and methane, wherein a tail gas (112) is formed using the product mixture (102) or a portion thereof in one or more separation steps (20, 21), wherein the tail gas (112) is substantially free of the one or more olefins and contains the hydrogen and methane from the product mixture (102) or a portion thereof, wherein the tail gas (112) or a portion thereof is permanently discharged from the process (100), wherein the heat of combustion is provided using a fuel gas (111),wherein a 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 upon provision of the heat of combustion, and wherein the flue gas (121) or a portion thereof is subjected to carbon dioxide separation (30). The method (100) according to claim 1, wherein the fuel gas (111) or a portion thereof is withdrawn from a gas supply line (110), and the tail gas (112) or the portion thereof permanently discharged from the method (100) is fed back into the gas supply line (110). Method (200) according to claim 1, in which the tail gas (112) or a part thereof is obtained to obtain a first tail gas fraction (113) which is enriched in hydrogen and depleted in methane compared to the tail gas (112), and a second tail gas fraction (114),which is depleted in hydrogen and enriched in methane compared to the tail gas (112), is subjected to one or more tail gas separation steps (21). The process (200) according to claim 3, wherein the first tail gas fraction (113) or a portion thereof is permanently discharged from the process (200).

5. The method (200) according to claim 3, wherein the first tail gas fraction (113) or a portion thereof is used separately from the fuel gas (111) to provide further combustion heat.

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

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

8. Method (100, 200) according to one of the preceding claims, wherein during the carbon dioxide separation (30) more than 60% of the carbon dioxide contained in the flue gas (121) or in the part thereof subjected to the carbon dioxide separation (30) is separated.

9. The method (100, 200) according to any one of the preceding claims, wherein the carbon dioxide separation (30) is carried out using one or more absorption liquids.

10. A method (100, 200) according to any preceding claim, wherein the fuel gas (111) or a portion thereof is combusted using an oxygen-enriched oxidizer gas.

11. The method (100, 200) according to any one of the preceding claims, wherein the conversion step(s) (10) is / are further carried out using electrically provided heat.

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

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