Process and facility for producing propylene by combining propane dehydrogenation and a steam cracking method with propane recirculation into the steam cracking method

Abstract

The invention relates to a process (10) for the production of propylene which comprises carrying out a process (1) for propane dehydrogenation to obtain a first component mixture (A), carrying out a further propylene production method (2) to obtain a second component mixture (B), and forming a separation product (P2) containing predominantly propane using one or more propane separation steps (S1), wherein at least part of the first component mixture (A) is supplied to the propane separation step or steps (S1). It is envisaged that the separation product (P2), which mainly contains propane, will at least partly be returned to the further propylene production method (2). A corresponding plant and a process for converting a steam cracking plant are also the subject of the invention.

Claims

1. A process (10) for the production of propylene, which comprises: carrying out a propane dehydrogenation method (1) to obtain a first component mixture (A) containing at least hydrogen, ethane, ethylene, propane and propylene, carrying out a further propylene production method (2) to obtain a second component mixture (B) containing at least hydrogen, methane, ethane, ethylene, propane and propylene, forming a separation product (P2) predominantly containing propane using at least a portion of the propane of the first component mixture (A) and using one or more propane separation steps (S1), wherein at least part of the first component mixture (A) is supplied to the propane separation step or steps (S1), characterized in that the separation product (P2) predominantly containing propane is at least partly returned to the further propylene production method (2).

2. The process (10) according to claim 1, in which the formation of the separation product (P2) predominantly containing propane which is carried out using one or more propane separation steps (S1) is further carried out using at least a part of the propane of the second component mixture (B), wherein at least a part of the second component mixture (B) is furthermore supplied to the propane separation step or steps (S1).

3. The process (10) according to claim 1 in which the predominantly containing propane separation product (P2) is not recycled to the propane dehydrogenation method (1).

4. The process (10) according to claim 1, in which only propane which has not been separated either from the first component mixture (A) or from the second component mixture (B) is supplied to the propane dehydrogenation method (1).

5. The process (10) according to claim 1, in which a steam cracking method is used as the further propylene production method (2).

6. The process (10) according to claim 1, in which the separation product predominantly containing propane predominantly contains propane and also from 0.1 to 25 volume percent mono- and polyunsaturated C3 hydrocarbons and/or heavier hydrocarbons.

7. The process (10) according to claim 1, which further includes forming a separation product (P1) containing predominantly or exclusively propylene using at least a portion of the propylene of the first and second component mixtures (A, B) and the propane separation step or steps (S1), forming a separation product (P3) containing at least predominantly ethylene using at least part of the ethylene of the first and second component mixtures (A, B) and one or more further separation steps; and forming a separation product (P4) containing at least predominantly ethane using at least part of the ethane of the first and second component mixtures (A, B) and the further separation step or steps.

8. The process (10) according to claim 1, which includes that at least part of the first component mixture (A) is subjected to one or more first pre-separation steps (V1) which comprise a pressure increase and an at least partial removal of hydrogen, to obtain a third component mixture (C), that at least part of the second component mixture (B) is subjected to one or more second pre-separation steps (V2) which comprise a pressure increase, an at least partial removal of hydrogen and an at least partial removal of methane, to obtain a fourth component mixture (D), that at least part of the third component mixture (C) together with at least part of the fourth component mixture (D) is subjected to the propane separation step or steps (S1), and/or that at least part of the third component mixture (C) is subjected together with the second component mixture (B) to the second pre-separation step or steps (V2) to form the fourth component mixture (D), and the fourth component mixture (D) is subjected to the propane separation step or steps (S1).

9. The process (10) according to claim 8, in which ethane and ethylene are also at least predominantly removed during the removal of hydrogen and methane in the second preliminary separation step or steps (V2), the removal of hydrogen and methane in the second preliminary separation step or steps (V2), in which ethane and ethylene are also at least predominantly removed, being carried out using a deethanization column.

10. The process (10) according to claim 8 in which ethane and ethylene are at least predominantly not removed in the removal of hydrogen and methane in the second preliminary separation step or steps (V2), wherein the removal of hydrogen and methane in the second preliminary separation step or steps (V2) in which ethane and ethylene are at least predominantly not removed is carried out using a demethanization column.

11. The process (10) according to claim 8, in which a demethanization column and/or a deethanization column and/or a depropanization column is used in the second preliminary separation step or steps (V2) and/or in the propane separation step or steps (S1), wherein the third component mixture is fed at least partially in the liquid state into the lower region of the demethanization column and/or the deethanization column and/or the depropanization column.

12. The process (10) according to claim 8, in which in the first preliminary separation step or steps (V1) of the first component mixture its hydrogen content is depleted to a value of 0 to 10 mol %, in particular 0.1 to 5 mol %, for example 0.2 to 2 mol %.

13. The process (10) according to claim 8, in which the first pre-separation step or steps to which the first component mixture is subjected comprise an increase in pressure to an absolute pressure of 3 to 40 bar, in particular of 10 to 30 bar, for example of 12 to 30 bar, wherein in particular in the first pre-separation step or steps after the increase in pressure an at least partial condensation of components boiling lower than hydrogen is carried out.

14. A plant for the production of propylene comprising: a first reactor unit provided and arranged to perform a propane dehydrogenation method (1) to obtain a first component mixture (A) containing at least hydrogen, ethane, ethylene, propane and propylene, a second reactor unit which is provided and arranged to perform a further propylene production method (2) to obtain a second component mixture (B) containing at least hydrogen, methane, ethane, ethylene, propane and propylene; and a separation unit provided and arranged to form a separation product (P2) predominantly containing propane using at least a portion of the propane of the first component mixture (A) and using one or more propane separation steps (S1), wherein means are provided adapted to supply at least a portion of the first component mixture (A) to the propane separation step or steps (S1), characterized by means provided and arranged to return at least part of the separation product (P2) predominantly containing propane to the further propylene production method (2).

15. A method of retrofitting a plant arranged to perform a steam cracking method using a number of plant components, wherein a hydrocarbon-containing feed mixture having a first composition is fed to the plant prior to retrofitting, characterised in that the retrofitting comprises to feed a hydrocarbon-containing feed mixture having a second, different composition to the plant instead of the hydrocarbon-containing feed mixture having the first composition, and to use one or more of the plant components for a propane dehydrogenation method instead of for the steam cracking method, wherein after the conversion a-the process (10) according to claim 1 is used by means of the conversion.

16. The process (10) according to claim 2 in which the predominantly containing propane separation product (P2) is not recycled to the propane dehydrogenation method (1).

17. The process (10) according to claim 2, in which only propane which has not been separated either from the first component mixture (A) or from the second component mixture (B) is supplied to the propane dehydrogenation method (1).

18. The process (10) according to claim 3, in which only propane which has not been separated either from the first component mixture (A) or from the second component mixture (B) is supplied to the propane dehydrogenation method (1).

19. The process (10) according to claim 2 in which a steam cracking method is used as the further propylene production method (2).

20. A method of retrofitting a plant arranged to perform a steam cracking method using a number of plant components, wherein a hydrocarbon-containing feed mixture having a first composition is fed to the plant prior to retrofitting, characterised in that the retrofitting comprises to feed a hydrocarbon-containing feed mixture having a second, different composition to the plant instead of the hydrocarbon-containing feed mixture having the first composition, and to use one or more of the plant components for a propane dehydrogenation method instead of for the steam cracking method, wherein after the conversion the plant according to claim 14 is provided by means of the conversion.

Description

SHORT DESCRIPTION OF THE DRAWINGS

[0060] FIG. 1 illustrates a process designed according to an embodiment of the invention in a highly simplified, schematic representation.

[0061] In the figures, constructionally and/or functionally corresponding elements are indicated with identical reference signs and are not explained repeatedly for the sake of clarity.

DETAILED DESCRIPTION OF THE DRAWINGS

[0062] FIG. 1 illustrates a process designed according to the invention in a highly simplified, schematic representation and is designated 10 in total.

[0063] Process 10 comprises a process 1 for propane dehydrogenation, a steam cracking method 2, one or more first preliminary separation steps V1, one or more second preliminary separation steps V2, and one or more propane separation steps S1. The first pre-separation step or steps V1, the second pre-separation step or steps V2, the propane separation step or steps S1 and any other separation steps not separately illustrated here can be grouped as required and, for example, combined in corresponding plant components.

[0064] In the example shown, procedure 1 for propane dehydrogenation is supplied with an initial input stream E1, which may include propane in particular, but not recycled propane. Instead, the first input current E1 is formed exclusively using an output current E0, which is fed to process 10 from the BL system limit. A part of this output stream E0 can also be fed to the steam cracking method 2, as illustrated in the form of a dashed material stream E0. In the example shown, the first input stream E1 is divided into two partial streams E1 and E1, wherein the partial stream E1 is fed directly to process 1 for propane dehydrogenation and the partial stream E is first used in the first pre-separation step or steps V1. In the first pre-separation step or steps V1, the partial stream E1 can, for example, be expanded to generate cold and only then fed into process 1 for propane dehydrogenation. In contrast to FIG. 1, however, the input stream E1 can also be treated completely as illustrated here with regard to the partial stream E1, i.e. it can be fed directly to process 1 for propane dehydrogenation.

[0065] Process 1 for propane dehydrogenation is carried out in a generally known manner so that a first component mixture A containing at least hydrogen, ethane, ethylene, propane and propylene is formed therein and which can be carried out from process 1 for propane dehydrogenation in the form of a corresponding material stream. Procedure 1 for propane dehydrogenation may in particular be carried out using one or more suitable reactors, which may have been designed in a customary manner.

[0066] In the example shown, the first component mixture A or the corresponding material flow is at least partially fed to the first pre-separation step or steps V1 in which the first component mixture A or the corresponding material flow is subjected to a pressure increase and at least partial removal of hydrogen. As mentioned above, this can be done in a generally known way. In particular, the first component mixture A or the corresponding material flow can be liquefied in the first pre-separation step or steps V1. Separated hydrogen is illustrated in the form of a material stream called H2. Also an at least partial removal of hydrocarbons with two carbon atoms is possible, but optional, as not shown separately in FIG. 1. In this way, a component mixture is obtained, which is also referred to here as the third component mixture C, and which can be executed in the form of a corresponding material flow from the first pre-separation step or steps V1. Possible hydrogen contents of the third component mixture C or the corresponding material flow have already been explained above. In particular, the third component mixture C downstream of the first preliminary separation step or steps V1 still contains hydrocarbons with three carbon atoms and minor amounts of other components, for example hydrocarbons with two hydrocarbon atoms, if not yet removed, and hydrocarbons with four carbon atoms formed as by-products in propane dehydrogenation method 1. If the first component mixture A also contains water and carbon dioxide, these can also be removed in the first pre-separation step or steps V1.

[0067] The steam cracking method 2, which can also be carried out in the usual manner, for example by using several cracking furnaces, is fed a hydrocarbon-rich feed in the form of a material flow E2 in the example shown, which is fed from the BL plant boundary. The hydrocarbon-rich use can include in particular naphtha and lighter hydrocarbons, but also heavy hydrocarbons. In particular, hydrocarbon-rich applications may include paraffinic hydrocarbons with two, three and four carbon atoms, in particular ethane, propane and butane. The steam cracking method 2 as a whole or different furnaces used in the steam cracking method 2 can also be supplied with different hydrocarbon feedstocks and processed there under different splitting conditions. In the example shown, the steam cracking method 2 is additionally supplied with the aforementioned partial stream E0 of the output stream E0, a propane-containing separation product P2 of the propane separation step or steps S1 and a further recirculated stream C2H6 which contains predominantly or exclusively ethane. With the exception of the return of the separation product P2, which mainly contains propane, the supply or return of the other flows shown is completely optional within the scope of this invention.

[0068] In the steam cracking method 2, the hydrocarbons of the hydrocarbon-rich feed(s) are at least partially converted so that a second component mixture B is obtained which contains at least hydrogen, methane, ethane, ethylene, propane and propylene. The second component mixture B can be drawn off from the steam cracking method 2 in the form of a corresponding material flow and then at least partly fed to one or more second pre-separation steps V2. The composition of the second component mixture B or of the corresponding material flow depends to a large extent on the hydrocarbon-rich application supplied to the steam cracking method 2.

[0069] As already explained several times, the second pre-separation step or steps V2 may include demethanization and/or deethanization in particular. For example, a demethanizer first process or a deethanizer first process can be used. Both variants have already been explained before and are generally known from the state of the art. They are therefore not explained here again. In addition to hydrogen, as illustrated here in the form of a material stream HZ, the mentioned material stream C2H6, which predominantly or exclusively contains ethane, as well as one or more product streams, here commonly designated PX, can also be formed in the second pre-separation step or steps. The product flow(s) PX can be led to the BL system limit. The hydrogen-rich material flow HZ can be combined with the hydrogen-rich material flow H2 and led together with this to the BL plant boundary. Together with the hydrogen-rich material stream HZ, methane in particular can also be discharged.

[0070] Irrespective of the process specifically carried out, however, in both cases a component mixture D is formed by the use of the second pre-separation step or steps V2, which is referred to here as the fourth component mixture, and which is at least depleted of hydrogen and methane with respect to the second component mixture B, or which is formed by at least partially removing hydrogen from methane from the second component mixture B. The second component mixture B is formed by the use of the second pre-separation step or steps V2. This fourth component mixture D is fed to the propane separation step or steps S1 in which the separation product P2, which mainly contains propane, is formed. Furthermore, in the example shown, a separation product P1 containing predominantly or exclusively propylene can also be formed in the propane separation step or steps S1 and taken to the BL plant boundary. One or more further separation products, herein referred to as PY, can also be separated in the propane separation step or steps S1 and led to the plant boundary BL. Depending on the specific design of the process in accordance with the invention, further separation steps, such as deethanization or depropanization, may be part of the second pre-separation step or steps V2 or part of the propane separation step or steps S1.

[0071] The third component mixture C can be fed to the second pre-separation step or steps V2 and/or the propane separation step or steps S1. For example, the third component mixture can be in the region of a separating bottom near the bottom of a demethanization column or deethanization column used in the second preliminary separation step or steps V2 and/or in a depropanization column which can be part of the second preliminary separation step or steps V2 and or of the propane separation step or steps S1. Corresponding alternatives are illustrated in the form of material flows C and C. Material flows can also be returned from the propane separation step or steps S1 to the pre-separation step or steps V2, as illustrated here in the form of the material flow PZ.