Patent ID: 6303021
Filing Date: 2001-10-16
Classification: C10G

Abstract:
An improved process for the recovery of aromatic hydrocarbons from a feed comprising a mixture thereof with non-aromatic hydrocarbon, the process comprising at least the steps of:a) contacting the feed with a lean solvent stream and a recycle stream in an extractor column operated at extraction conditions effective to separate the feed into a raffinate stream comprising non aromatic hydrocarbons and a first rich solvent stream comprising solvent, aromatic hydrocarbons and non aromatic hydrocarbons;b) passing the first rich solvent stream to a flash drum wherein the stream encounters a reduction in pressure causing the stream to separate into two streams comprising a vapor hydrocarbon stream produced by flashing and a second rich solvent stream;c) passing the second rich solvent stream to an isolated top tray of a stripper column wherein the stream encounters a further reduction in pressure causing the stream to separate again into a vapor hydrocarbon stream produced by flashing and a third rich solvent stream;d) passing the third rich solvent stream to a multitiered tray portion of the stripper column, contacting the stream with an upwardly flowing vapor hydrocarbon-steam stream under conditions suitable for stripping and recovering a first flashless vapor stream;e) combining the vapor streams from the flash drum, isolated top tray and multitiered tray portion into a condensed overhead mixed hydrocarbon stream and passing said mixed hydrocarbon vapor stream to said extr8Xcolumn as at least a portion of said recycle stream;f) separating water from the overhead vapor stream and combining the separated water with water from a raffinate wash system and further water streams created by the process and sending the combined water stream to a vaporizer where the steam of the upwardly flowing hydrocarbon-steam stream of the stripper column is generated;g) recovering an aromatic product stream together with a portion of the upwardly flowing steam from said upwardly flowing vapor stream and withdrawing a lean solvent stream from the bottom of the stripping column; andh) returning the lean solvent stream to the extractor column for recirculation;the improvement comprising:creating, a barrier across the multitiered tray portion of the stripper column at a position below-that at which the aromatic product stream is recovered to produce a top tray portion and a bottom tray portion;diverting the lean solvent stream exiting the bottom portion of the stripper column through a heat exchanger;diverting the third hydrocarbon stream from the top tray portion through the heat exchanger to which heat is supplied from the diverted lean solvent stream from the stripper column; andcreating a fourth heated hydrocarbon stream which is then fed to the bottom tray portion of the stripper column for continuation through steps d) through h) above, the heating of the fourth hydrocarbon stream generated significantly improving the degree of extraction of the aromatic product.