GB614309A - Improvements relating to fractionation applied to petroleum and other hydrocarbon feedstocks - Google Patents

Abstract

Hydrocarbons boiling within a range of 30 DEG F. are economically separated by subjecting the mixture to fractional distillation in a centrifugal fractionator which is heated by vapours withdrawn from the fractionator and compressed. The pressure of the vapours withdrawn is preferably raised to a value at which the temperature of the compressed vapour is not less than 5 DEG F. above the temperature of the liquid leaving the stripping section of the fractionator. The process is particularly applicable to the separation of pure paraffin or aromatic hydrocarbons from close-boiling fractions, or of pure olefinic hydrocarbons from fractions of cracked spirit. The vapours of hexane, heptane and octane are particularly suitable for compression. The compression required may be obtained by injection, along with the reflux, of an immiscible liquid of low vapour pressure at the centre of the centrifugal fractionator. In an example, a mixture of normal and iso-butane together with small quantities of propane and pentane was fractionated in a centrifugal fractionator having substantially no pressure drop and operating at 73.7 lbs. per square inch (absolute). Isobutane at 100 DEG F. was taken off overhead, compressed to 109 lbs. per square inch (128 DEG F.) in an electrical compressor, and passed to the reboiler where normal butane was boiling at 123 DEG F. Specifications 590,554 and 600,551 are referred to.