Process for preparing olefins by thermal steamcracking in cracking furnaces

Patent metadata

Field	Value
Publication number	US-9505679-B2
Application number	US-201314420630-A
Country	US
Kind code	B2
Filing date	Aug 6, 2013
Priority date	Aug 9, 2012
Publication date	Nov 29, 2016
Grant date	Nov 29, 2016

Abstract

The invention relates to a process for converting hydrocarbon feeds by thermal steamcracking to at least one olefin-containing product stream comprising at least ethylene and propylene, with at least partial conversion of a first hydrocarbon feed in at least one first cracking furnace ( 1 ) and of a second hydrocarbon feed in at least one second cracking furnace ( 2 ). According to the invention, the second hydrocarbon feed is converted in the second cracking furnace ( 2 ) with cracking conditions that lead to a ratio of propylene to ethylene of 0.7 to 1.6 kg/kg, and the first hydrocarbon feed is converted in the first cracking furnace ( 1 ) with cracking conditions that lead to a ratio of propylene to ethylene of 0.25 to 0.85 kg/kg at the cracking furnace exit, the value for the ratio of propylene to ethylene for the second hydrocarbon feed being above the value for the ratio of propylene to ethylene for the first hydrocarbon feed.

First claim

The invention claimed is:

1. A process for converting hydrocarbon feeds by thermal steamcracking to an olefin-containing product stream comprising at least ethylene and propylene, with at least partial conversion of a first hydrocarbon feed in at least one first cracking furnace ( 1 ) and of a second hydrocarbon feed in at least one second cracking furnace ( 2 ), characterized in that the second hydrocarbon feed is converted in the second cracking furnace ( 2 ) with cracking conditions that lead to a ratio of propylene to ethylene of 0.7 to 1.6 kg/kg at the cracking furnace outlet, and in that the first hydrocarbon feed is converted in the first cracking furnace ( 1 ) with cracking conditions that lead to a ratio of propylene to cethylene of 0.25 to 0.85 kg/kg at the cracking furnace exit, the value for the ratio of propylene to ethylene for the second hydrocarbon feed being above the value for the ratio of propylene to ethylene for the first hydrocarbon feed and the second hydrocarbon feed predominantly comprising hydrocarbons having a maximum carbon number of 5.

2. The process as claimed in claim 1 , characterized in that the second hydrocarbon is converted in the second cracking furnace ( 2 ) with cracking conditions that lead to a ratio of propylene to ethylene of up to 1.2 kg/kg, at the cracking furnace exit.

3. The process as claimed in claim 1 , characterized in that the first hydrocarbon feed is converted in the first cracking furnace ( 1 ) with cracking conditions that lead to a ratio of propylene to ethylene of 0.3 to 0.75 kg/kg, more preferably of 0.4 to 0.65 kg/kg, at the cracking furnace exit.

4. The process as claimed in claim 1 , in which the values for the ratio of propylene to ethylene for the first and second hydrocarbons differ by at least 0.1 kg/kg, preferably by at least 0.15 kg/kg, more preferably by at least 0.2 kg/kg.

5. The process as claimed in claim 1 , characterized in that the second hydrocarbon feed consists for the most part of hydrocarbons having a carbon number of 5 or/and 4.

6. The process as claimed in claim 1 , characterized in that the second cracking furnace is supplied with one or more recycled fractions (P, T) which are obtained from the product stream and which comprise predominantly hydrocarbons having a carbon number of not more than 5.

7. The process as claimed in claim 1 , characterized in that the first cracking furnace is supplied with at least one fraction (U) which has been separated from the product stream and recycled, comprising predominantly hydrocarbons having a carbon number of at least 6.

8. The process as claimed in claim 1 , characterized in that a fresh feed is used, which is fractionated into at least one first and one second fresh feed fraction, and the first fresh feed fraction is conducted at least partly into the first cracking furnace and the second fresh feed fraction at least partly into the second cracking furnace.

9. The process as claimed in claim 1 , characterized in that the second cracking furnace ( 2 ) is supplied not only with the second fresh feed fraction (B 2 ) but also with a further fresh feed (BL) consisting predominantly of hydrocarbons having a maximum carbon number of 5.

10. The process as claimed in claim 1 , in which the cracking furnace exit temperature for the conversion in the second cracking furnace ( 2 ) is between 680° C. and 820° C., preferably between 700° C. and 800° C. and further preferably between 710° C. and 780° C. and more preferably between 720° C. and 760° C., and the cracking furnace exit temperature for the conversion in the first cracking furnace ( 1 ) is between 800° C. and 1000° C., preferably between 820° C. and 950° C. and more preferably between 840° C. and 900° C., the cracking furnace exit temperature of the first cracking furnace ( 1 ) being above that of the second cracking furnace ( 2 ).

11. The process as claimed in claim 10 , in which the cracking furnace exit temperature for the conversion in the first cracking furnace ( 1 ) is at least 10° C. above, preferably at least 15° C. above, more preferably at least 20° C. above, the cracking furnace exit temperature for the conversion in the second cracking furnace ( 2 ).

12. The process as claimed in claim 1 , in which 0.3 to 1.5 kg of steam per kg of hydrocarbon feed is used in the first cracking furnace ( 1 ), and 0.15 to 0.8 kg of steam per kg of hydrocarbon feed in the second cracking furnace ( 2 ).

13. The process as claimed in claim 1 , in which at least one fraction (V) comprising predominantly hydrocarbons having a carbon number of 2 or 3 is obtained from the product stream and at least partly converted in a cracking furnace ( 3 ) for gaseous feed.

14. The process as claimed in claim 1 , characterized in that the fresh feed (B) used for the first cracking furnace ( 1 ) or/and for the fresh feed for the fresh feed fractionation ( 7 ) comprises natural gas condensates and/or crude oil fractions, especially naphtha, and/or synthetic and/or biogenic hydrocarbons and/or mixtures derived therefrom.

Assignees

• Linde Ag

Inventors

• Fritz Helmut
• Walter Stefanie
• Schmidt Gunther

Classifications

• C10G2400/20

  C2-C4 olefins · CPC title

• C10G9/36 Primary

  with heated gases or vapours · CPC title

• C07C4/04 Primary

  Thermal processes {(C07C4/025 takes precedence)} · CPC title