Method and assembly for fractionating olefins for the production of sustainable jet fuel

Abstract

The invention relates to a method for fractionating olefins for the production of sustainable jet fuel, having the following steps: providing (S10) a reactant stream (4) comprising olefins, in particular unfractionated olefins, said reactant stream (4) being provided in particular by means of a methanol-to-olefin process or a methanol-to-propylene process; separating (S20) the reactant stream (4) into a gas stream (6) and a liquid stream (8) by means of a separator (2); feeding (S30) the liquid stream (8) into a liquid rectification column in the form of a dehexanizer (10); and separating (S40) hydrocarbons having a carbon chain length of six or less by means of the dehexanizer (10) in order to obtain an olefin product stream (18). No further steps for separating or fractionating the liquid stream (8) are carried out between the step of separating (S20) the reactant stream (4) into a gas stream (6) and a liquid stream (8) and the step of feeding (S30) the liquid stream (8) into the dehexanizer (10). The invention also relates to a corresponding system (1).

Description

[0001] Description

[0002] Method and arrangement for fractionating olefins for the production of sustainable aviation fuel

[0003] The present invention relates to a process and a plant for fractionating olefins for the production of sustainable aviation fuel.

[0004] Sustainable aviation fuel (SAF) is a fuel that is produced using the greatest possible amount of renewable energy and avoiding climate-damaging emissions as far as possible. SAF production involves producing olefins from renewably produced methanol using the methanol-to-propylene process (MTP process) or the methanol-to-olefins process (MTO process). Zeolites, such as SAPO-34 or ZSM-5, are particularly used as catalysts. Depending on the process conditions, reactor design, and catalysts, these processes can be carried out in fixed-bed or fluidized-bed reactors in ethylene and propylene mode.Typically, after the initial production of the olefins, the intermediate product stream is processed, comprising quenching, separation of previously used solvents and absorbents, such as water, methanol and caustic soda, as well as compression and subsequent fractionation of the olefins.

[0005] Conventional processes and plants for fractionating olefins are designed to produce ethylene and propylene fractions with very high degrees of purity. In this way, conventional processes and plants provide ethylene and propylene with what is known as "polymer grade" purity for the plastics industry. For example, a conventional plant has an arrangement of rectification columns comprising a deethanizer, a demethanizer, a debutanizer, a depropanizer and a dehexanizer. In particular, a conventional arrangement has an ethylene fractionation unit for separating ethane and ethylene (so-called C2 splitter) and a propylene fractionation unit for separating propane and propylene (so-called C3 splitter) in order to provide ethylene and propylene with a purity of "polymer grade".

[0006] The provision of numerous rectification columns as well as C2 and C3 splitters implies a high energy and plant engineering expenditure.

[0007] Previous approaches to the production of SAF involve the use of the above-mentioned conventional arrangement of rectification columns with C2 and C3 splitters, so that SAF is produced according to the previous approaches with high energy input.

[0008] Based on the known prior art, it is an object of the present invention to provide a process for fractionating olefins for the production of sustainable aviation fuel and a corresponding plant.

[0009] The problem is solved by a method having the features of claim 1. Advantageous further developments emerge from the subclaims, the description and the figures.

[0010] Accordingly, a process for fractionating olefins for the production of sustainable aviation fuel is proposed, comprising the following steps:

[0011] - Providing a reactant stream comprising olefins,

[0012] - Separating the reactant stream into a gas stream and a liquid stream by means of a separator,

[0013] - feeding the liquid stream into a liquid rectification column in the form of a dehexanizer, - separating hydrocarbons having a carbon chain length of six or less by means of the dehexanizer to obtain an olefin product stream.

[0014] Between the step of separating the reactant stream into a gas stream and a liquid stream and the step of feeding the liquid stream into the dehexanizer, no further step for separating or fractionating the liquid stream takes place.

[0015] In other words, the liquid stream is fed into a first rectification column in the form of the dehexanizer.

[0016] The reactant stream may, in particular, comprise unfractionated olefins. "Unfractionated" is understood here to mean that a mixture of fractions of different valences is present, for example, that a C2 olefin fraction is mixed with a C3 olefin fraction.

[0017] The term liquid rectification column is understood here to mean a rectification column that has an input stream in the liquid phase, in other words a liquid stream at the inlet. Analogously, a gas rectification column is understood here to mean a rectification column that has an input stream in the gaseous phase, in other words a gas stream at the inlet. Accordingly, the deethanizer and demethanizer units used in the conventional arrangement of rectification columns are referred to here as gas rectification columns, and the depropanizer, debutanizer, and dehexanizer units are referred to as liquid rectification columns.

[0018] The reactant stream can be provided by means of a methanol-to-olefin process (abbreviated to "MTO") or a methanol-to-propylene process (abbreviated to "MTP"). Furthermore, the methanol used for this purpose can be produced regeneratively. MTO, MTP and the regenerative production of methanol are known in principle to those skilled in the art. In the course of the present invention, it was recognized that an olefin-containing hydrocarbon mixture in which ethylene or propylene is present in relatively low degrees of purity compared to the degrees of purity achieved with a conventional plant or arrangement for fractionating olefins can be used for SAF production.

[0019] Accordingly, by feeding the liquid stream into the dehexanizer immediately after the reactant stream has been separated into the gas stream and the liquid stream, the debutanizer can be eliminated according to the conventional process.

[0020] Furthermore, by separating hydrocarbons with a carbon chain length of six or less using the dehexanizer, an olefin product stream can be obtained that has a sufficient degree of purity for SAF production. This also eliminates the need for a depropanizer, a C2 splitter, and an O3 splitter, for example, so that the equipment and energy requirements for SAF production are drastically reduced compared to conventional processes or arrangements.

[0021] Consequently, it may be necessary to design the dehexanizer to be more efficient than conventional processes or systems. Surprisingly, it was discovered in the course of the present invention that the additional effort required to dimension the dehexanizer to be more efficient can be more than compensated for by the aforementioned savings in the other process units or steps.

[0022] As described above, the process provides that between the step of "separating the reactant stream into a gas stream and a liquid stream" and the step of "feeding the liquid stream into the dehexanizer" no further step for separating or fractionating the liquid stream takes place. In other words, the above step of "feeding" can take place essentially immediately after the above step of "separating". In this way, the liquid stream separated after compression is fed to only a single liquid rectification column, so that expenditure for further liquid rectification columns can be saved.

[0023] Thus, in the process or a corresponding plant, it can be provided that no further liquid rectification column for separating hydrocarbons is interposed between the separator and the dehexanizer.

[0024] The procedure may also include:

[0025] - feeding the gas stream into a gas rectification column, in particular in the form of a deethanolizer,

[0026] - Separation of C2 hydrocarbons to obtain another olefin product stream.

[0027] In other words, the gas stream is fed into a second rectification column in the form of a deethane condenser. The term "C2 hydrocarbons" refers here to hydrocarbons with a carbon chain length of two. Thus, the separation particularly concerns ethane and ethylene. In this way, two separate olefin product streams with sufficient purity for SAF production can be provided, requiring only a single gas rectification column and a single liquid rectification column.

[0028] The procedure may also include:

[0029] - Separation of light gas using a demethanizer. This allows the purity of the further olefin product stream to be easily improved. In this way, the further olefin product stream contains predominantly ethylene and ethane, while the olefin product stream contains predominantly C3 to C6 olefins as well as by-products harmless for SAF production. The process can further comprise:

[0030] Combining the bottoms fraction of the deethanier with the tops fraction of the dehexanier. This allows the olefin product stream to be provided with hydrocarbons with a carbon chain length between three and six in a particularly simple manner.

[0031] The above-mentioned object is further achieved by a system having the features of claim 7. Advantageous further developments emerge from the present description and the figures.

[0032] Accordingly, a plant for fractionating olefins for the production of sustainable aviation fuel is proposed. The plant comprises a separator for separating a reactant stream into a gas stream and a liquid stream, a liquid rectification column in the form of a dehexanizer, and a connecting line connecting the separator to the dehexanizer to feed the liquid stream to the dehexanizer. The connecting line does not have any further or additional rectification column.

[0033] The definitions, technical effects and advantages explained above in relation to the proposed process apply equally and mutatis mutandis to the proposed plant, and vice versa.

[0034] In particular, the plant now features only the dehexanizer as its sole liquid rectification column. This allows the dehexanizer to produce an olefin product stream that meets the requirements of SAF production. This provides a particularly simple and effective plant.

[0035] Furthermore, the plant can comprise an arrangement of rectification columns consisting essentially of the dehexanizer, a deethanizer, and a demethanizer. In other words, the arrangement of rectification columns can be formed essentially of the dehexanizer, a deethanizer, and a demethanizer. For example, the arrangement of rectification columns can therefore be provided without a debutanizer or depropanizer. Furthermore, the plant can thus operate without a C2 or C3 splitter.

[0036] Furthermore, the column bottom of the deethanier can be connected to the column head of the dehexanier. This allows the olefin product stream to be provided with hydrocarbons with a carbon chain length of between three and six in a particularly simple manner.

[0037] In particular, the outlet of the column head of the demethanizer can be connected to the inlet of the demethanizer. Thus, Cl hydrocarbons can be easily separated, so that a further olefin product stream comprising C2 olefins can be provided. The further olefin product stream can contain by-products harmless for SAF production, in particular ethane.

[0038] Furthermore, the outlet of the column bottom of the deethanizer can be connected to an outlet line of the column head of the dehexanizer. Thus, hydrocarbons from the gas stream with a carbon chain length of three or more can continue to be fed to the olefin product stream. In this way, the yield is further increased.

[0039] Furthermore, the plant can be designed such that it does not have an ethylene fractionation unit for separating ethane and ethylene. In other words, the plant or the arrangement of rectification columns can be provided without an O2 splitter.

[0040] Furthermore, the plant can be designed such that it does not have a propylene fractionation unit for separating propane and propylene. In other words, the plant or the arrangement of rectification columns can be provided without a C3 splitter.

[0041] Furthermore, the reactant stream in the proposed process or in the proposed plant may comprise: - 0.5 to 5% by weight of light gases, in particular methane, ethane and / or propane,

[0042] - 25 to 40% by weight of ethylene and / or propylene,

[0043] - 1-5 weight percent butenes,

[0044] - 1 to 20% by weight of hydrocarbons with a carbon chain length of five or more, in particular pentenes, hexenes, higher olefins, paraffins, aromatics, naphthenes,

[0045] - remaining percentage by weight of water, in particular 30 to 72.5% by weight of water.

[0046] Thanks to the proposed process and the proposed arrangement, the olefin product stream and the further olefin product stream are not limited to ethylene and propylene. Ethane and propane are inert substances in SAF production and do not cause any harm. However, the weight yield can be increased by approximately 5% thanks to the inclusion of butene, especially when butene accounts for 5% by weight of the reactants. This applies analogously to the inclusion of pentene and hexene.

[0047] For example, the reactant stream can contain: 2 weight percent ethane and propane, 30 weight percent ethylene and propylene, 4 weight percent butene, 10 weight percent pentene and hexene. Thanks to the proposed process and the proposed arrangement, in this example not only the 30 weight percent ethylene and propylene of the reactant stream are utilized for SAF production, but also the 4 weight percent butene and the 10 weight percent pentene and hexene. In other words, in this example not only 30 weight percent hydrocarbons of the reactant stream are utilized - as in the prior art - but 30 + 4 + 10, i.e. 44 weight percent hydrocarbons of the reactant stream are utilized for SAF production, i.e. almost 50% more, while at the same time the energy and equipment required to fractionate the olefins can be drastically reduced.

[0048] Preferred further embodiments of the invention are explained in more detail in the following description of the figures. These schematically show:

[0049] Figure 1 shows a conventional plant for fractionating olefins;

[0050] Figure 2 shows a plant for fractionating olefins for the production of sustainable aviation fuel; and

[0051] Figure 3 shows a process for fractionating olefins for the production of sustainable aviation fuel.

[0052] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the various figures are provided with identical reference symbols, and a repeated description of these elements is partially omitted to avoid redundancies.

[0053] Figure 1 schematically shows a conventional plant 50 for fractionating olefins. Using a known methanol-to-propylene process (MTP) or methanol-to-olefins process (MTO), an intermediate product stream in the form of a mixture of various hydrocarbons is produced from methanol. The intermediate product stream is processed by quenching, separating oxygenates with solvents and absorbents, and compressing and fractionating the olefins. The olefin fractionation is carried out using rectification columns that are connected as follows.

[0054] To fractionate the olefins, a conventional arrangement of rectification columns is used, in which the hydrocarbons are separated according to their carbon chain length and boiling points. The term rectification column refers to a device for countercurrent distillation, i.e., a thermal separation process for separating a homogeneous solution of two or more substances.

[0055] The intermediate product stream is compressed to form a gaseous and a liquid fraction, which are then separated. The gaseous fraction is fed to a deethanizer. In this context, a deethanizer is a continuously operated rectification column used to separate ethane from an input stream of mixed light hydrocarbons. Typically, the ethane and lighter components leave the column top, while heavier components are discharged via the column bottom. Boiling and distillation of the light hydrocarbons takes place, for example, at around 14 bar or less.

[0056] In general, the operating principle of an n-rectification column is symbolized in the figures with markings Cn- at the column head and Cn+ at the column bottom. For example, the deethanizer in the figures is marked C2- at the column head and C3+ at the column bottom. This indicates that mainly hydrocarbons with a carbon chain length of two or less exit at the column head and mainly hydrocarbons with a carbon chain length of three or more exit at the column bottom. This operating principle and nomenclature applies analogously to the other rectification columns, i.e. the demethanizer for n=1, the depropanizer for n=3, the debutanizer for n=4 and the dehexanizer for n=6.

[0057] As described above, the deethanizer separates the mixture into a hydrocarbon fraction consisting of components with a carbon chain length of two or less at the column top (C2-) and one with components with a carbon chain length of three or more at the column bottom (C3+). A demethanizer is connected downstream of the deethanizer. In the demethanizer, a residual gas containing, among other things, methane is separated from the top fraction of the deethanizer at the column top. The remaining C2 fraction is transferred to a C2 splitter 52, where the separation of the ethane / ethylene mixture takes place. In this way, the conventional plant provides ethylene with a purity of "polymer grade."

[0058] After compression and separation from the gaseous fraction, the liquid hydrocarbon fraction is transferred to a debutanizer. The overhead fraction of the debutanizer, comprising hydrocarbons with a carbon chain length of four or less (C4-), is combined with the bottoms fraction of the deethanizer (C3+) to form an inlet stream of a downstream depropanizer.

[0059] In the depropanizer, hydrocarbons with a carbon chain length of four or more (C4+) are removed from the column bottom, which are classified as byproducts in conventional plants. The overhead product of the depropanizer (C3), consisting primarily of a propane / propylene mixture, is transferred to a C3 splitter 54 for separation and production of propylene.

[0060] The bottoms fraction of the debutanizer, comprising hydrocarbons with a carbon chain length of five or more (C5+), is fed to the dehexanizer. The dehexanizer delivers hydrocarbons with a carbon chain length of six or less (C6-) at the top of the column, so that the top fraction delivers C5-C6 hydrocarbons as a further by-product. Accordingly, the bottoms fraction of the dehexanizer delivers hydrocarbons with a carbon chain length of seven or more (C7+) as a further by-product of the conventional plant 50. Thus, the conventional plant 50, by means of the conventional arrangement 56 of rectification columns, essentially delivers fractionated hydrocarbons, which particularly concerns the C1 to C4 range, as well as C2 and C3 olefins with the particularly high degree of purity "polymer grade".

[0061] Figure 2 shows a plant 1 for fractionating olefins for the production of sustainable aviation fuel. Furthermore, the steps of the proposed process for fractionating olefins are additionally shown in Figure 2 with reference symbols for the corresponding process units.

[0062] First, a reactant stream 4 is provided S 10 by means of the known methanol-to-propylene process (MTP) and / or methanol-to-olefins process (MTO). The reactant stream 4 is a mixture of various hydrocarbons, in particular unfractionated olefins, and can also be referred to as an intermediate product stream. As in a conventional plant, the intermediate product stream is subjected to initial processing, comprising quenching and the removal of oxygenates using solvents and absorbents.

[0063] Subsequently, the reactant stream 4 is compressed, and a separation S20 of the reactant stream 4 into a gas stream 6 and a liquid stream 8 takes place by means of a separator 2. The separator 2 can be provided together with the corresponding compressor.

[0064] The plant 1 comprises an arrangement 22 of rectification columns, comprising a deethanier 14 downstream of the separator 2, a demethanizer 16 downstream of the deethanier 14 and a dehexanier 10 downstream of the separator 2, wherein the bottom fraction of the deethanier 14 is connected or combined with the top fraction of the dehexanier 16 to form a common main product output line 18, S50, which contains an olefin product stream 18. After the separation step S20, the gas stream 6 is fed S32 into a gas rectification column in the form of the deethanizer 14. The top fraction of the deethanizer 14 comprises hydrocarbons having a carbon chain length of two or less (C2-), the bottom fraction of the deethanizer 14 comprises hydrocarbons having a carbon chain length of three or more (C3+).

[0065] The top fraction (C2-) of the deethanizer 14 is fed to the demethanizer 16, which separates the incoming mixture into a top fraction containing Cl-hydrocarbons and a bottom fraction (C2+) with a carbon chain length of two or more. Since the demethanizer 16 is downstream of the deethanizer 14, essentially no hydrocarbons with a carbon chain length greater than two enter the inlet of the demethanizer 16, so that the bottom fraction of the demethanizer 16 essentially comprises hydrocarbons with a carbon chain length of two (C2), which is referred to herein as a further olefin product stream 20, which represents another main product of plant 1. Since plant 1 does not have a C2 splitter (compare reference numeral 52 in Figure 1), the further olefin product stream 20 comprises a mixture of ethane and ethylene, which can be used for SAF production, since ethane is inert in SAF production and thus harmless.Via the head fraction of the demethanizer 16, a further separation S52 of light gas or residual gas, which essentially contains methane and is a by-product of plant 1, takes place.

[0066] Furthermore, after the separation step S20, the liquid stream 8 is fed S30 into a liquid rectification column in the form of the dehexanizer 10. By means of the dehexanizer 10, hydrocarbons with a carbon chain length of six or less are separated S40 in order to obtain the olefin product stream 18. Accordingly, the top fraction of the dehexanizer 10 comprises hydrocarbons with a carbon chain length of six or less (C6-) and, as shown above, is combined S50 with the bottoms fraction (C3+) of the deethanizer 14 to form the olefin product stream 18.

[0067] Thus, the olefin product stream 18 essentially comprises a mixture of C3 to C6 hydrocarbons, i.e., hydrocarbons with a carbon chain length of between three and six. Thus, the olefin product stream 18 contains propylene at a significantly lower purity than in the conventional plant 50 (see Figure 1), but this purity is sufficient for SAF production and can be provided with significantly less effort.

[0068] The bottoms fraction of the dehexanizer 10 provides another by-product of plant 1 in the form of hydrocarbons with a carbon chain length of seven or more (07+).

[0069] The provision of demethanizer 16 is optional. If a demethanizer 16 is omitted, the remaining olefin product stream comprises 20 Cl hydrocarbons, which can be further processed or separated as required during SAF production.

[0070] Where applicable, all individual features shown in the embodiments can be combined and / or exchanged without departing from the scope of the invention.

Claims

Patent claims:

1. A process for fractionating olefins for the production of sustainable aviation fuel, comprising the following steps: - Providing (S10) a reactant stream (4) comprising olefins, in particular unfractionated olefins, in particular wherein the reactant stream (4) is provided by means of a methanol-to-olefin process or a methanol-to-propylene process, - Separating (S20) the reactant stream (4) into a gas stream (6) and a liquid stream (8) by means of a separator (2), - feeding (S30) the liquid stream (8) into a liquid rectification column in the form of a dehexanizer (10), - Separating (S40) hydrocarbons having a carbon chain length of six or less by means of the dehexanizer (10) to obtain an olefin product stream (18), wherein no further step for separating or fractionating the liquid stream (8) takes place between the step of separating (S20) the reactant stream (4) into a gas stream (6) and a liquid stream (8) and the step of feeding (S30) the liquid stream (8) into the dehexanizer (10).

2. The method according to claim 1, wherein between the separator (2) and the dehexanizer (10) no further liquid rectification column for separating hydrocarbons is interposed.

3. A method according to claim 1 or 2, comprising: - feeding (S32) the gas stream (6) into a gas rectification column, in particular in the form of a deethanizer (14), - Separating (S42) C2 hydrocarbons, in particular to obtain a further olefin product stream (20).

4. The method according to claim 3, comprising: - Combining (S50) the bottom fraction of the deethanizer (14) with the top fraction of the dehexanizer (10).

5. A method according to any one of the preceding claims, comprising: - Separation of light gas by means of a demethanizer (16).

6. Process according to one of the preceding claims, wherein the reactant stream (4) comprises: - 0.5 to 5% by weight of light gases, in particular methane, ethane and / or propane, - 25 to 40% by weight of ethylene and / or propylene, - 1-5 weight percent butenes, - 1 to 20% by weight of hydrocarbons with a carbon chain length of five or more, in particular pentene, hexene, higher olefins, paraffins, aromatics, naphthenes, - 30 to 72.5% water by weight.

7. Plant (1) for the fractionation of olefins for the production of sustainable aviation fuel, comprising - a separator (2) for separating a reactant stream (4), which in particular comprises unfractionated olefins, into a gas stream (6) and a liquid stream (8), - a liquid rectification column in the form of a dehexanizer (10), characterized by a connecting line (12) which connects the separator (2) to the dehexanizer (10) in order to feed the liquid stream (8) to the dehexanizer (10), wherein the connecting line (12) does not have a further rectification column.

8. Plant (1) according to claim 7, comprising an arrangement (22) of rectification columns consisting essentially of the dehexanizer (10), a deethanizer (14) and a demethanizer (16) exists.

9. Plant (1) according to claim 8, wherein the column bottom of the deethanizer (14) is connected to the column top of the dehexanizer (10).

10. Plant (1) according to claim 8 or 9, wherein the output of the Column head of the deethanizer (14) is connected to the inlet of the demethanizer (16).

11. Plant (1) according to one of claims 7 to 10, wherein the plant (1) does not have an ethylene fractionation unit (52) for separating ethane and ethylene.

12. Plant (1) according to one of claims 7 to 11, wherein the plant (1) does not have a propylene fractionation unit (54) for separating propane and propylene.

13. Plant (1) according to one of the preceding claims 7 to 12, wherein the reactant stream (4) comprises: - 0.5 to 5% by weight of light gases, in particular methane, ethane and / or propane, - 25 to 40% by weight of ethylene and / or propylene, - 1-5 weight percent butenes, - 1 to 20% by weight of hydrocarbons with a carbon chain length of five or more, in particular pentene, hexene, higher olefins, paraffins, aromatics, naphthenes, - 30 to 72.5% water by weight.

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