Hydrogenation of acetylenes in a hydrocarbon stream
A system for hydrogenation C 3 and C 4 acetylenes contained within a hydrocarbon stream generated in a stream cracker unit where a debutanizer is placed upstream of a depropanizer for more economical processing of the hydrocarbon stream to produce lighter hydrocarbons, where the system requires only one stripper tower downstream of hydrogenation to remove residual hydrogen.
1. A process for selective hydrogenation of acetylenes comprising:
directing a C 3 -C 10 hydrocarbon stream to a debutanizer;
condensing a debutanizer C 3 -C 4 overhead stream;
selectively hydrogenating C 4 acetylenes in the condensed C 3 -C 4 overhead stream in a C 4 acetylene hydrogenation reactor to give a reactor outlet stream;
directing the reactor outlet stream to a depropanizer downstream from the debutanizer;
drawing a top stream from the depropanizer containing a C 3 mixture comprising methyl acetylene and propadiene;
drawing a bottom stream from the depropanizer containing a crude C 4 mixture;
directing the C 3 mixture to a methyl acetylene and propadiene (MAPD) reactor and selectively hydrogenating the methyl acetylene and propadiene to give a crude propylene stream; and
directing the crude propylene stream to a stripper column to vent off residual unreacted hydrogen.
2. The process of claim 1 where the stripper column is the only stripper column and in the absence of a stripper column downstream of the crude C 4 mixture.
3. The process of claim 1 where condensing a debutanizer C 3 -C 4 overhead stream is conducted against a refrigeration medium.
4. The process of claim 1 where the C 4 acetylene hydrogenation reactor is operated at a temperature of from about 50° F. (10° C.) to about 140° F. (about 60° C.), and a pressure of from about 300 psia (about 2.1 MPa) to about 600 psia (about 4.9 MPa).