Method for producing a stream of propylene and associated facility

A propylene production installation, comprising:

• a metathesis reactor configured to be supplied with at least one feed cut rich in C4 and/or C5 hydrocarbons, and by at least one cut rich in ethylene, the metathesis reactor being configured to produce a metathesis product;
• a deethylenizer, fed with the metathesis product from the metathesis reactor, the deethylenizer having a deethylenizer top and a deethylenizer bottom, the deethylenizer being configured to produce an overhead stream rich in ethylene at the deethylenizer top, and to produce a feed stream at the deethylenizer bottom;
• a depropylenizer having a depropylenizer top and a depropylenizer bottom, the depropylenizer being configured to receive the feed stream and to produce a bottom stream containing C4+ hydrocarbons at the depropylenizer bottom and to produce an overhead stream rich in propylene at the depropylenizer top;
• a collector configured to collect a propylene stream from the overhead stream of the depropylenizer;
• a lateral withdrawer configured to withdraw a recycle stream rich in C4 and/or C5 hydrocarbons in the depropylenizer and a recycler configured to return the recycle stream to the metathesis reactor;
• a lateral off-drawer configured to draw off a purge rich in C4 paraffinic hydrocarbons and/or rich in isobutene in the depropylenizer,
• wherein the depropylenizer has a level N4 at which the recycle stream is withdrawn, and a level N2 at which the purge rich in C4 paraffinic hydrocarbons and/or rich in isobutene is withdrawn, the level N4 being located below the level N2.

A method for producing a stream of propylene, comprising:

• introducing a feed cut rich in C4 and/or C5 hydrocarbons, and at least one cut rich in ethylene into a metathesis reactor;
• recovering a metathesis product at an outlet of the metathesis reactor;
• introducing the metathesis product into a deethylenizer;
• producing an overhead stream rich in ethylene at a head of the deethylenizer and producing a feed stream at a bottom of the deethylenizer;
• introducing the feed stream in a depropylenizer and recovering a bottom stream containing C4+ hydrocarbons from a bottom of the depropylenizer;
• recovering a propylene stream from an overhead stream of the depropylenizer;
• withdrawing a recycle stream rich in C4 and/or C5 hydrocarbons laterally in the depropylenizer;
• returning the recycle stream to the metathesis reactor;
• the lateral withdrawing of the recycling stream being carried out in gas phase.

A method for producing a stream of propylene, comprising:

• introducing a feed cut rich in C4 and/or C5 hydrocarbons, and at least one cut rich in ethylene into a metathesis reactor;
• recovering a metathesis product at an outlet of the metathesis reactor;
• introducing the metathesis product into a deethylenizer;
• producing, an overhead stream rich in ethylene at a head of the deethylenizer and producing a feed stream at a bottom of the deethylenizer;
• introducing the feed stream in a depropylenizer and recovering a bottom stream containing C4+ hydrocarbons from a bottom of the depropylenizer;
• recovering a propylene stream from an overhead stream of the depropylenizer;
• withdrawing a recycle stream rich in C4 and/or C5 hydrocarbons laterally in the depropylenizer;
• returning the recycle stream to the metathesis reactor;
• drawing-off a purge rich in C4 paraffinic hydrocarbons and/or rich in isobutene, laterally in the depropylenizer,
• wherein an of amount of C4 paraffinic hydrocarbons and/or isobutene in purge is greater than 50 mol %.