Process and plant for producing an olefin

Patent metadata

Field	Value
Publication number	US-10730810-B2
Application number	US-201716472435-A
Country	US
Kind code	B2
Filing date	Dec 22, 2017
Priority date	Dec 22, 2016
Publication date	Aug 4, 2020
Grant date	Aug 4, 2020

Abstract

A process for producing an olefin having N carbon atoms is proposed in which using a dehydrogenation a process gas is formed which contains at least the olefin having N carbon atoms, a paraffin having N carbon atoms and a hydrocarbon having N−1 carbon atoms and in which using at least a portion of the process gas a separation input is formed which is subjected to a low temperature separation in which the separation input is cooled stepwise over a plurality of temperature levels and condensates are separated from the separation input, wherein the condensates are at least partly subjected to a first low temperature rectification to obtain a first gas fraction and a first liquid fraction, wherein the first gas fraction contains at least the olefin having N carbon atoms in a lower proportion than in the condensates and the hydrocarbon having N−1 in a higher proportion than in the condensates. It is provided that the first gas fraction is at least partly subjected to a second low temperature rectification using a liquid reflux containing predominantly or exclusively the hydrocarbon having N−1 carbon atoms in which the first gas fraction undergoes depletion in the olefin having N carbon atoms. A corresponding plant ( 100 ) likewise forms part of the subject matter of the invention.

First claim

The invention claimed is:

1. Process for producing an olefin having N carbon atoms in which using a dehydrogenation a process gas is formed which contains at least the olefin having N carbon atoms, a paraffin having N carbon atoms and a hydrocarbon having N−1 carbon atoms and in which using at least a portion of the process gas a separation input is formed which is subjected to a first low temperature separation in which the separation input is cooled stepwise over a plurality of temperature levels and condensates are separated from the separation input, wherein the condensates are at least partly subjected to a first low temperature rectification to obtain a first gas fraction and a first liquid fraction, wherein the first gas fraction contains at least the olefin having N carbon atoms in a lower proportion than in the condensates and the hydrocarbon having N−1 in a higher proportion than in the condensates, characterized in that the first gas fraction is at least partly subjected to a second low temperature rectification using a liquid reflux containing predominantly or exclusively the hydrocarbon having N−1 carbon atoms in which the first gas fraction undergoes depletion in the olefin having N carbon atoms.

2. Process according to claim 1 in which a proportion of the separation input which remains gaseous in the stepwise cooling is likewise at least partly subjected to the second low temperature rectification.

3. Process according to claim 1 in which in the second low temperature rectification a second gas fraction poor in or free from the olefin having N carbon atoms and a second liquid fraction containing the olefin having N carbon atoms in a higher proportion than in the first gas fraction are formed.

4. Process according to claim 3 in which the second liquid fraction is recycled into the first low temperature rectification.

5. Process according to claim 1 in which the liquid reflux is provided as a liquified gas or in which the liquid reflux is formed using a liquid fraction formed by partial condensation of a gas containing predominantly or exclusively the hydrocarbon having N−1 carbon atoms.

6. Process according to claim 5 in which a proportion which remains gaseous in the partial condensation of the gas containing predominantly or exclusively the hydrocarbon having N−1 carbon atoms is at least partly introduced into the low temperature separation.

7. Process according to claim 5 in which the liquefied gas or the liquefied fraction are partly introduced into the low temperature separation.

8. Process according to claim 1 in which N is two, so that the olefin having N carbon atoms is ethylene, the paraffin having N carbon atoms is ethane and the hydrocarbon having N−1 carbon atoms is methane.

9. Process according to claim 6 in which the dehydrogenation is performed oxidatively.

10. Process according to claim 8 in which the temperature levels to which the separation input is cooled stepwise comprise a first temperature level of −20° C. to −40° C. and/or a second temperature level of −40° C. to −60° C. and/or a third temperature level of −70° C. to −80° C. and/or a fourth temperature level of −95° C. to −105° C.

11. Process according to claim 8 in which the liquid reflux which contains predominantly or exclusively methane is provided in the form of liquefied natural gas or formed using at least a portion of a liquid fraction provided by cooling a predominantly or exclusively methane-containing gas at a pressure level of 30 to 70 bar to a temperature level of −70° C. to −100° C. and decompressing to a pressure level of 10 to 20 bar.

12. Process according to claim 1 in which for the second low temperature rectification a rectification column having 1 to 10 theoretical or practical trays is employed.

13. Process according to claim 1 in which the process gas further contains oxygen and carbon monoxide.

14. Plant ( 100 ) for producing an olefin having N carbon atoms, comprising at least one reactor unit ( 103 ) adapted for using a dehydrogenation to form a process gas which contains at least the olefin having N carbon atoms, a paraffin having N carbon atoms and a hydrocarbon having N−1 carbon atoms and comprising means adapted for using at least a portion of the process gas to form a separation input and subjecting said input to a first low temperature separation which is adapted for cooling the separation input stepwise over a plurality of temperature levels and separating condensates from the separation input and at least partly subjecting the condensates to a first low temperature rectification to obtain a first gas fraction and a first liquid fraction, wherein the first gas fraction contains at least the olefin having N carbon atoms in a lower proportion than in the condensates and the hydrocarbon having N−1 in a higher proportion than in the condensates, characterized in that means are provided which are adapted for at least partly subjecting the first gas fraction to a second low temperature rectification using a liquid reflux containing predominantly or exclusively the hydrocarbon having N−1 carbon atoms in which the first gas fraction undergoes depletion in the olefin having N carbon atoms.

15. Plant ( 100 ) according to claim 14 adapted for performing a process for producing an olefin having N carbon atoms in which using a dehydrogenation a process gas is formed which contains at least the olefin having N carbon atoms, a paraffin having N carbon atoms and a hydrocarbon having N−1 carbon atoms and in which using at least a portion of the process gas a separation input is formed which is subjected to a first low temperature separation in which the separation input is cooled stepwise over a plurality of temperature levels and condensates are separated from the separation input, wherein the condensates are at least partly subjected to a first low temperature rectification to obtain a first gas fraction and a first liquid fraction, wherein the first gas fraction contains at least the olefin having N carbon atoms in a lower proportion than in the condensates and the hydrocarbon having N−1 in a higher proportion than in the condensates, characterized in that the first gas fraction is at least partly subjected to a second low temperature rectification using a liquid reflux containing predominantly or exclusively the hydrocarbon having N−1 carbon atoms in which the first gas fraction undergoes depletion in the olefin having N carbon atoms.

16. Process according to claim 2 in which in the second low temperature rectification a second gas fraction poor in or free from the olefin having N carbon atoms and a second liquid fraction containing the olefin having N carbon atoms in a higher proportion than in the first gas fraction are formed.

17. Process according to claim 2 in which the liquid reflux is provided as a liquified gas or in which the liquid reflux is formed using a liquid fraction formed by partial condensation of a gas containing predominantly or exclusively the hydrocarbon having N−1 carbon atoms.

18. Process according to claim 3 in which the liquid reflux is provided as a liquified gas or in which the liquid reflux is formed using a liquid fraction formed by partial condensation of a gas containing predominantly or exclusively the hydrocarbon having N−1 carbon atoms.

19. Process according to claim 4 in which the liquid reflux is provided as a liquified gas or in which the liquid reflux is formed using a liquid fraction formed by partial condensation of a gas containing predominantly or exclusively the hydrocarbon having N−1 carbon atoms.

Assignees

• Linde Ag

Inventors

• Peschel Andreas
• Obermeier Andreas
• Fritz Helmut
• Zellhuber Mathieu

Classifications

• F25J2270/60

  Closed external refrigeration cycle with single component refrigerant [SCR], e.g. C1-, C2- or C3-hydrocarbons · CPC title

• F25J2270/12

  External refrigeration with liquid vaporising loop · CPC title

• F25J2215/62

  Ethane or ethylene · CPC title

• F25J2210/62

  Liquefied natural gas [LNG]; Natural gas liquids [NGL]; Liquefied petroleum gas [LPG] · CPC title

• F25J2210/12

  Refinery or petrochemical off-gas · CPC title