Abstract: Processes using multiple expansion turbines for efficient recovery of power from a plurality of very high pressure streams of superheated vapor are disclosed. Beneficially, processes of the invention use at least two classes of expansion turbines. Processes according to this invention are particularly useful for recovery of power from very high pressure streams of superheated steam in an olefins manufacturing process. Such streams are typically produced by thermal cracking of suitable petroleum derived feed stocks, and the olefins being produced and purified are typically ethylene and/or propylene.

Abstract: This invention is an improved distillation sequence for the separation and purification of ethylene from a cracked gas. A hydrocarbon feed enters a C2 distributor column. The top of the C2 distributor column is thermally coupled to an ethylene distributor column, and the bottoms liquid of a C2 distributor column feeds a deethanizer column. The C2 distributor column utilizes a conventional reboiler. The top of the ethylene distributor is thermally coupled with a demethanizer column, and the bottoms liquid of the ethylene distributor feeds a C2 splitter column. The ethylene distributor column utilizes a conventional reboiler. The deethanizer and C2 splitter columns are also thermally coupled and operated at a substantially lower pressure than the C2 distributor column, the ethylene distributor column, and the demethanizer column. Alternatively, a hydrocarbon feed enters a deethanizer column.