Process for the production of low-concentration ethylene for chemical use

• US 8,173,855 B2
• Filed: 05/28/2009
• Issued: 05/08/2012
• Est. Priority Date: 06/03/2008
• Status: Expired due to Fees

• Current Assignee: Solvay SA (Solvac SA)
• Original Assignee: Solvay SA (Solvac SA)
• Inventors: Kotter, Joachim, Winkler, Hans-Dieter, Mews, Peter, Lempereur, Michel, Balthasart, Dominique, Strebelle, Michel
• Primary Examiner(s): Nguyen, Tam M
• Application Number:
  US12/995,509
• Publication Number:
  US 20110077439A1
• Time in Patent Office: 1,076 Days
• Field of Search: None
• US Class Current: 585/809
• CPC Class Codes: C07C 11/04 Ethylene
• CPC Class Codes: C07C 4/04 Thermal processes C07C4/025 takes precedence
• CPC Class Codes: C10G 2300/1044 Heavy gasoline or naphtha having a boiling range of about 100 - 180 °C
• CPC Class Codes: C10G 2300/1059 Gasoil having a boiling range of about 330 - 427 °C
• CPC Class Codes: C10G 2300/1081 Alkanes
• CPC Class Codes: C10G 2400/20 C2-C4 olefins
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2210/12 Refinery or petrochemical off-gas
• CPC Class Codes: F25J 2215/62 Ethane or ethylene
• CPC Class Codes: F25J 2270/02 Internal refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 3/0219 Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
• CPC Class Codes: F25J 3/0238 separation of CnHm with 2 carbon atoms or more
• CPC Class Codes: F25J 3/0252 separation of hydrogen production of hydrogen containing gas in general C01B3/00, e.g. separation of hydrogen or hydrogen containing gases form gaseous mixtures at low temperatures C01B3/506
• CPC Class Codes: Y02P 30/40 Ethylene production

Abstract

Process for the production of ethylene for chemical use starting with a hydrocarbon source according to which: a) the hydrocarbon source is subjected to a first cracking step, namely a pyrolysis step carried out in a cracking oven, thus producing a mixture of cracking products; b) the mixture of cracking products is subjected to a succession of treatment steps, including a compression step, which makes it possible to obtain a purified crude gas stream; c) the purified crude gas stream is then cooled to a temperature where hydrocarbons with 6 and more carbon atoms condense so that they can be removed from the purified crude gas stream; d) the resulting purified gas stream is afterwards supplied to one separating column, where a fraction A containing hydrogen, methane and ethylene is separated at the head of the column and a heavy fraction C is separated at the bottom of the column; e) a part of the reflux of this column is supplied to a refrigeration cycle leading to a fraction B enriched with ethylene; and f) the fraction A and fraction B are separately supplied to chemical use of ethylene.

Claims

1. A process for the production of ethylene for chemical use starting with a hydrocarbon source according to which:

a) the hydrocarbon source is subjected to a first cracking step, namely a pyrolysis step carried out in a cracking oven, thus producing a mixture of cracking products;

b) said mixture of cracking products is subjected to a succession of treatment steps, including a compression step, which makes it possible to obtain a purified crude gas stream;

c) the purified crude gas stream is then cooled to a temperature where hydrocarbons with 6 and more carbon atoms condense so that they can be removed from the purified crude gas stream;

d) the resulting purified gas stream is afterwards supplied to one separating column, where a fraction A containing hydrogen, methane and ethylene is separated at the head of the column and a heavy fraction C is separated at the bottom of the column;

e) a part of the reflux of this column is supplied to a refrigeration cycle leading to a fraction B enriched with ethylene; and

f) said fraction A and said fraction B are separately supplied to chemical use of ethylene.

2. The process according to claim 1, wherein the hydrocarbon source is selected from the group consisting of naphtha, gas oil, natural gas liquid, ethane, propane, butane, isobutane and mixtures thereof.

3. The process according to claim 2, wherein the hydrocarbon source is selected from the group consisting of ethane, propane, butane, and propane/butane mixtures.

4. The process according to claim 1, wherein the hydrocarbons condensed in step c) are returned to step b).

5. The process according to claim 1, wherein the refrigeration cycle is an ethylene refrigeration cycle.

6. The process according to claim 1, wherein the part of the reflux of the separating column is supplied to the refrigeration cycle after evaporation and utilization of the refrigeration content.

7. The process according to claim 1, wherein said fraction B is depleted in hydrogen and methane by removing them as inert gas from the refrigeration cycle.

8. The process according to claim 1, wherein said fraction C is hydrogenated and fed to the hydrocarbon source in step a).

9. The process according to claim 8, wherein, when using ethane as feedstock, the hydrogenation of said fraction C takes place together with the optional hydrogenation of acetylene allowing direct supply of said fraction C to the hydrocarbon source without further hydrogenation.

10. The process according to claim 8, wherein, when using propane, butane or propane/butane mixtures as feedstock, said fraction C is subjected to hydrogenation in a trickle-phase reactor without additional separation and afterwards mixed with the hydrocarbon source.