Patent GB-1493075-A (GB)
Title: Process for the separation of hydrocarbons
IPC: C10G5/04
Filed: 1975-03-20
Abstract: 1493075 Separating hydrocarbons UOP Inc 20 March 1975 [21 March 1974] 11610/75 Heading C5E A process for the recovery of selected hydrocarbon liquid and vapour constituents from a feed stock containing these constituents comprising (i) contacting the feed stock with a lean oil in an absorption zone; (ii) passing rich oil from the absorption zone to a stripping zone; (iii) passing stripped oil from the stripping zone to a fractionation zone; and (iv) passing a portion of fractionation zone bottoms to the absorption for use for the lean oil, further comprises the improvement of introducing separately into the absorption zone for use as the lean oil not only the portion of fractionation zone bottoms but also a portion of stripped oil from the stripping zone. In a modification of the process (i) the feed stock, a first lean absorber oil, a second lean absorber oil and a stripped vapour are passed to an absorption zone maintained under conditions sufficient to absorb at least a part of the hydrocarbon vapour constituents of the feed stream into the lean absorber oils; (ii) withdrawing from the absorption zone a rich absorber oil and a vapour substantially free from hydrocarbons with more than two carbon atoms per molecule; (iii) passing the rich absorber oil into a stripping zone maintained under conditions sufficient to provide a stripped vapour for passage to the absorption zone for use as stripped vapour and principally comprising hydrogen and hydrocarbons having less than 3 carbon atoms per molecule, and to provide a stripped oil principally comprising hydrocarbons having 3 or more carbon atoms; (ii) passing a first portion of the stripped oil into a fractionation zone maintained under conditions sufficient to provide a stabilized liquid hydrocarbon product and a liquid hydrocarbon product; (v) withdrawing a portion of the stabilized liquid hydrocarbon product and passing it to the absorption zone for use as the first lean absorber oil; and (vi) passing a second portion of the stripped oil to the absorption zone for use as second lean absorber oil. In the preferred embodiment described, a feed stream comprising hydrogen, normally vaporous hydrocarbons such as methane, ethane and propane, and normally liquid hydrocarbons such as pentane and hexane enters absorption zone 2 by conduit 1. A first lean oil enters this zone by conduit 9 and a second lean oil enters this zone beneath the entry point of the first lean oil. The lean oils pass downwardly through zone 2, absorbing at least part of the vaporous hydrocarbon constituents of the feed, gases not absorbed by the lean oil leaving absorption zone 2 by conduit 3, a rich oil stream containing liquid feed components, lean oils and absorbed gaseous and vaporous feed components leaving zone 2 by conduit 4 and passing to stripping zone 5. Absorbed gases are removed from the rich oil in zone 5 and pass by conduit 6 to conduit 1, intermixing therein with the feed, a stripped oil stream being withdrawn from stripping zone 5 by conduit 7. A portion of stripped oil leaves conduit 7 by conduit 8 and passes to absorption 2 as the second lean oil, the remaining portion of stripped oil leaving conduit 7 by conduit 10 and passing to fractionation zone 11 where it is separated into a liquefied hydrocarbon vapour product and a hydrocarbon liquid, the vapour product being withdrawn from zone 11 and leaving the system by conduit 12. A portion of the liquid leaves conduit 12 by conduit 9 passing as the first lean oil to absorption zone 2, the remaining portion of the liquid being withdrawn from conduit 12 by conduit 13 and leaving the system.