Method and apparatus for producing hydrocarbons

Abstract

A method (100) for producing hydrocarbons is proposed, in which one or more steam cracking feed streams (a) which predominantly or exclusively contain hydrocarbons with two or more carbon atoms are subjected to one or more steam cracking steps (10), thus obtaining one or more steam cracking discharge streams (b), and wherein one or more reaction feed streams (t, u) which predominantly or exclusively contain methane are subjected to one or more steps (60) for the oxidative coupling of methane, thus obtaining one or more reaction discharge streams (v) which contain ethane, while a separation discharge stream (m) which predominantly or exclusively contains ethane is formed using fluid from the steam cracking discharge stream or streams (b). In the proposed method, it is provided that fluid from the reaction discharge stream or streams (v) is subjected to one or more thermal cracking steps (70) which are subsequent to the step or steps (60) for the oxidative coupling of methane, and in which the ethane which is present in the fluid from the reaction discharge stream or streams (v) is at least partially reacted to form ethylene, under the influence of waste heat from the step or steps (60) for the oxidative coupling of methane, and that fluid (w) from the separation discharge stream (m) is fed into the subsequent thermal cracking step or steps (70), wherein the step or steps (60) for the oxidative coupling of methane and the subsequent thermal cracking step or steps (70) are carried out in a joint reactor and wherein the transfer of heat into the thermal cracking step or steps (70) that follow takes place by convection.

Claims

1. Method (100) for producing hydrocarbons, wherein one or more steam cracking feed streams (a) which predominantly or exclusively contain hydrocarbons with two or more carbon atoms are subjected to one or more steam cracking steps (10), thus obtaining one or more steam cracking discharge streams (b), and wherein one or more reaction feed streams (t, u) which predominantly or exclusively contain methane are subjected to one or more steps (60) for the oxidative coupling of methane, thus obtaining one or more reaction discharge streams (v) which contain ethane, while a separation discharge stream (m) which predominantly or exclusively contains ethane is formed using fluid from the steam cracking discharge stream or streams (b), characterised in that fluid from the reaction discharge stream or streams (v) is subjected to one or more thermal cracking steps (70) which are subsequent to the step or steps (60) for the oxidative coupling of methane, and in which the ethane which is present in the fluid from the reaction discharge stream or streams (v) is at least partially reacted to form ethylene, under the influence of waste heat from the step or steps (60) for the oxidative coupling of methane, and in that fluid (w) from the separation discharge stream (m) is fed into the thermal cracking step or steps (70), wherein the step or steps (60) for the oxidative coupling of methane and the subsequent thermal cracking step or steps (70) are carried out in a joint reactor and wherein the transfer of heat into the thermal cracking step or steps (70) that follow takes place by convection.

2. Method (100) according to claim 1, wherein an additional separation discharge stream (l) which predominantly or exclusively contains methane or methane and hydrogen is formed using fluid from the steam cracking discharge stream or streams (b), wherein fluid (u) from the additional separation discharge stream (l) is used as the or one of the reaction feed streams.

3. Method (100) according to one of the preceding claims, wherein a pyrolysis oil (c) and/or a pyrolysis gasoline stream (d) is formed using fluid from the steam cracking discharge stream or streams (b), while fluid from the pyrolysis oil (c) and/or the pyrolysis gasoline stream (d) is used to heat the steam cracking step or steps (10).

4. Method (100) according to one of the preceding claims, wherein fluid from the separation discharge stream (m) is subjected to the or one of the steam cracking steps (10).

5. Method (100) according to claim 4, wherein a quantity of the fluid (w) from the separation discharge stream (m) which is fed into the thermal cracking step or steps (70), and/or a quantity of the fluid from the separation discharge stream (m) which is subjected to the or one of the steam cracking steps (10), is adjusted as a function of an ethane requirement of the thermal cracking step or steps (70) and/or of the steam cracking step or steps (10).

6. Method (100) according to one of the preceding claims, wherein fluid from the steam cracking discharge stream or streams (b) and fluid from one or more discharge streams (x) of the thermal cracking step or steps (70) which follow the step or steps (60) for the oxidative coupling of methane, is subjected to at least one joint processing and/or separation step (20-50).

7. Method (100) according to one of the preceding claims, wherein all the fluid from the reaction discharge stream or streams (v) is subjected, without separation, to the one or more thermal cracking steps (70) which follow the step or steps (60) for the oxidative coupling of methane.

8. Method (100) according to one of the preceding claims, wherein the waste heat from the step or steps (60) for the oxidative coupling of methane is used in a joint reactor in which the thermal cracking step or steps (70) are carried out.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows a method for producing hydrocarbons according to one embodiment of the invention, in the form of a schematic flow diagram.

[0033] FIGS. 2A and 2B illustrate the conversion of a method according to one embodiment of the invention in the form of a schematic flow diagram.

DETAILED DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 shows a method for producing hydrocarbons according to one embodiment of the invention in the form of a schematic flow diagram, which is generally designed 100.

[0035] One or more steam cracking steps, which have been supplied with one or more steam cracking feed streams a, are designated 10 here. One or more steam cracking discharge streams b formed in the steam cracking step or steps 10 are initially fed into an oil and water wash 20, whereby first of all a (crude) pyrolysis oil stream c and a (crude)pyrolysis gasoline stream d, for example, are separated off. A steam stream e may be fed back into the steam cracking step or steps 10. The pyrolysis oil stream c and the pyrolysis gasoline stream d may be prepared in any desired manner and separated into fractions. It is also possible to obtain a stream f, which is thermally utilised to recover heat energy at least intermittently in the steam cracking step or steps 10. Additionally or exclusively, heat energy may be provided, at least intermittently, through another combustible stream g. Fractions of the streams c and d may be taken out of the process 200 as products.

[0036] A stream h remaining after the oil and water wash 20 may be subjected to a compression and drying 30, at which point another pyrolysis gasoline stream i may be obtained. A stream k remains, which can be subjected to a low temperature separation 40. In the low temperature separation 40, a number of separation discharge streams are obtained, such as for example a fuel gas stream 1, an ethane stream m, an ethylene stream n and a stream o of hydrocarbons with three or more carbon atoms. The stream o is subjected to a further separation 50, in which another pyrolysis gasoline stream p, a propane stream q, a propylene stream r and a stream s of hydrocarbons with four carbon atoms may be obtained.

[0037] The fuel gas stream 1, the ethane stream m and the propane stream q are conventionally recycled into the steam cracking step or steps 10, while the fuel gas stream 1 is conventionally combusted.

[0038] The method 100 shown in FIG. 1 comprises one or more steps 60 for the oxidative coupling of methane into which one or more reaction feed streams t are fed. A stream u formed from fluid from the fuel gas stream m may also be fed, as a reaction feed stream, into the step or steps 60 for the oxidative coupling of methane. The step or steps 60 for the oxidative coupling of methane operate in a manner known per se, so as to form one or more reaction discharge streams v. Additional streams fed into the step or steps 60 for the oxidative coupling of methane, for example one or more oxygen streams, are not shown in the drawings.

[0039] The step or steps 60 for the oxidative coupling of methane are directly followed by one or more thermal cracking steps 70 (so-called post-bed cracking). As previously mentioned, a large amount of waste heat is produced during the oxidative coupling of methane, which can advantageously be used, for example, for cracking the ethane present during the oxidative coupling of methane. The amount of waste heat is so great that a larger amount of ethane can be cracked than is formed during the oxidative coupling of methane. Although the thermal cracking step or steps 70 in FIG. 1 are shown separately from the step or steps 60 for the oxidative coupling of methane, it should be remembered that these are typically implemented in a single construction unit.

[0040] Within the scope of the embodiment of the invention shown in FIG. 1, it is envisaged that fluid from the ethane stream m, i.e. a corresponding separation discharge stream from the low temperature separation 40, may be fed into the thermal cracking step or steps 70. Corresponding fluid is shown as the stream w. In this way, the ethane can be profitably used and there is no need for externally supplied ethane. Likewise, if necessary, some of the stream m may also be recycled into the steam cracking step or steps 10 or external ethane may be fed in.

[0041] A discharge stream x from the thermal cracking step or steps 70 may for example be guided into the low temperature separation 40. It is also possible to feed it into other steps, for example into the compression and drying 30.

[0042] FIGS. 2A and 2B illustrate the conversion of a method according to one embodiment of the invention in a pure steam cracking process in the form of a schematic flow diagram. The streams shown are given identical reference numerals to the streams in FIG. 1. FIGS. 2A and 2B are also highly simplified.

[0043] FIG. 2A shows, for example, an existing apparatus for the production of hydrocarbons, in which five parallel steam cracking steps are implemented. The steam cracking steps designated 10 are provided, for example, for reacting steam cracking feeds a (identified only at one point) which contain a large proportion of naphtha. In each case, steam cracking discharge streams b are obtained (identified only at one point). A steam cracking step designated 10, on the other hand, is provided for reacting steam cracking feeds which predominantly or exclusively contain ethane (so-called gas cracking furnace).

[0044] The steam cracking discharge streams b are fed into a processing and separation step, shown highly schematically here, which comprises steps 10 to 50 shown in FIG. 1, for example. In addition to other separation discharge streams, an ethylene stream n and a propylene stream r are obtained, for example, and removed as products. An ethane stream m which is also obtained as a separation discharge stream is introduced into the steam cracking step designated 10, where it is reacted. A methane stream 1 which has also been obtained as a separation discharge stream is used to heat the steam cracking step designated 10.

[0045] According to FIG. 2B, the steam cracking step designated 10 is replaced by one or more steps 60 for the oxidative coupling of methane, into which the methane stream 1 is wholly or partially fed, among other things. The ethane stream is wholly or partially fed into one or more subsequent thermal cracking steps 70, as explained hereinbefore.