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Patent Abstracts

      437.     ------.  [CORNELL, P. W.]  (Gulf Oil Corp.).  Process and Apparatus for Concentrating Dilute Solutions.  United States Patent 2,509,136, May 23, 1950: appl. filed June 17, 1949, Serial No. 99,788: 14 claims (Cl. 202-40).  Chem. Abs., vol. 44, 1950, p. 7100.

Dilute aqueous solutions of oxygenated organic compounds produced as secondary products in the Fischer-Tropsch process are concentrated by fractional distillation in 2 stages.  The 1^st fractionating column contains a relatively small number of plates and is operated so as to produce a bottoms fraction consisting essentially of H₂O.  The enriched overhead fraction is compressed in a compressor driven by a steam turbine.  The compressed vapors enter a heat exchanger, where they are condensed, supplying their heat of vaporization to the reboiler of the column.  Part of the resulting liquefied overhead is returned to the column as reflux, and the remainder is fed to a 2d column containing a relatively large number of plates.  This column produces an overhead fraction of the desired final concentration, the bottoms being essentially H₂O.  The entire process is controlled by varying the degree of compression in accordance with the composition of the liquid on an intermediate tray in the second column, the degree of compression decreasing as the concentration of oxygenated compounds increases.  Thus, the 2d column is operated to produce the desired separation between H₂O and oxygenated products, while the 1^st column is automatically controlled to supply the maximum quantity of oxygenated products that the 2d column is capable of concentrating.  The exhaust steam from the turbine is used to preheat the feed to the system and to supply heat to the reboiler of the 2d column.  Thus, all the necessary heat is supplied in the steam to the turbine.