Process for recovering olefins from cat-cracked gas without accumulating undesirable oxides of nitrogen
US5710357A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 5, 1995 |
| Grant date | Jan 20, 1998 |
| Priority date | — |
| Expiry date | Jun 5, 2015 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF25J2220/02
- WIPO fieldChemical engineering
- WIPO sectorChemistry
Abstract
A safe, effective, and economical method is provided for recovering olefins from cat-cracked gases without accumulating dangerous amounts of nitrogen oxides. A stream of cat-cracked gas first is scrubbed to remove acid gases, including nitrogen dioxide (NO.sub.2), and then is passed through a depropanizer fractionation tower. Hydrocarbons having four or more carbon atoms are recovered in the bottoms of the depropanizer, and the overhead from the depropanizer--which is composed of hydrocarbons having three or fewer carbon atoms--is sent to an absorber demethanizer tower. Hydrocarbons having two or more carbon atoms are recovered in the bottoms from the absorber demethanizer tower, where temperatures are no lower than about -45.56.degree. C. (-50.degree. F.) The overhead from the absorber demethanizer tower--which is composed of methane, hydrogen, and trace amounts of nitrogen oxide, C.sub.2, and absorbent (C.sub.3)--then is chilled to condense and recover trace amounts of C.sub.2 and heavier gases, including trace amounts of the C.sub.3 absorbent, at temperatures of about -101.11.degree. C. (-150.degree. F.) or higher. Thus, recovery of desired hydrocarbons from the cat-cracked gas …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.