Energy Conservation in Heavy-Hydrocabon Distillation

PATENT
Energy Conservation in Heavy-Hydrocabon Distillation
United States Patent Application 20120048711
Inventors:
Werba, Gregory R. (Arlington Heights, IL, US)
Corradi, Jason T. (Arlington Heights, IL, US)
Ablin, David W. (Arlington Heights, IL, US)
Application Number: 12/868223
Publication Date: 03/01/2012
Assignee: UOP LLC (Des Plaines, IL, US)
Abstract:
An aromatics complex producing one or more xylene isomers offers a large number of opportunities to conserve energy by heat exchange within the complex. One previously unrecognized opportunity is through providing two parallel distillation columns operating at different pressures to separate C8 aromatics from C9+ aromatics. The parallel columns offer additional opportunities to conserve energy within the complex.
FIELD OF THE INVENTION
This invention relates to an improved apparatus suitable for energy savings in the distillation of hydrocarbons. More specifically, the present invention concerns an apparatus providing energy conservation within an aromatics-processing complex producing xylene isomers.
BACKGROUND OF THE INVENTION
The xylene isomers are feedstocks for a variety of important industrial chemicals. The most widely produced and used of the xylene isomers is para-xylene, the principal feedstock for polyester, which continues to enjoy a high growth rate from large base demand. Ortho-xylene is used to produce phthalic anhydride, which supplies high-volume but relatively mature markets. Meta-xylene is used in lesser but growing volumes for such products as plasticizers, azo dyes and wood preservers. Ethylbenzene generally is present in xylene mixtures and is occasionally recovered for styrene production, but is usually considered a less-desirable component of C8 aromatics.
Among the aromatic hydrocarbons, the overall importance of xylenes rivals that of benzene as a feedstock for industrial chemicals. Xylenes and benzene are produced from petroleum by reforming naphtha but not in sufficient volume to meet demand, thus conversion of other hydrocarbons is necessary to increase the yield of xylenes and benzene. Often toluene is de-alkylated to produce benzene or selectively disproportionated to yield benzene and C8 aromatics from which the individual xylene isomers are recovered.
An aromatics complex flow scheme has been disclosed by Meyers in the Handbook of Petroleum Refining Processes, 2d. Edition in 1997 by McGraw-Hill, and is incorporated herein by reference.
Aromatics complexes producing xylenes are substantial consumers of energy, notably in distillation operations to prepare feedstocks and separate products from conversion processes. The separation of xylenes from heavy aromatics in particular offers substantial potential for energy savings. Energy conservation in such processes would not only reduce processing costs but also would address current concerns about carbon emissions.
SUMMARY OF THE INVENTION
A broad embodiment of the present invention is a distillation apparatus comprising two distillation columns for separating C8-aromatic components from C9-and-heavier aromatic components, comprising a first distillation column adapted to operate at a first pressure and having a bottom portion in fluid communication with a reboiler, a second distillation column adapted to operate at a second pressure and having a top portion in fluid communication with an overhead conduit, the overhead conduit from the second column providing fluid communication to the reboiler of the first column.
A more specific embodiment is a distillation apparatus comprising two distillation columns for separating C8-aromatic components from C9-and-heavier aromatic components, comprising a first distillation column adapted to operate at a first pressure and having a bottom portion in fluid communication with a reboiler, a second distillation column adapted to operate at a second pressure and having a top portion in fluid communication with an overhead conduit, the overhead conduit from the second column providing fluid communication to the reboiler of the first column and the overhead conduit adapted to supply a heat source to the reboiler.
More preferably, the second pressure is at least 400 kPa higher than the first pressure.
Additional objects, embodiments and details of this invention can be obtained and inferred from the following detailed description of the invention.
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