GB380348A - Improvements in process and apparatus for the final refining of benzoles washed withacid - Google Patents

Abstract

<PICT:0380348/III/1> In the fractional distillation of acid refined benzol to obtain pure benzene, toluene and xylene, the benzene and toluene are each rectified twice in two separate columns, the second column being operated under vacuum and the heat necessary for the rectification being supplied by the hot vapours from the first column, which is heated by steam. Washed benzol from a reservoir A is supplied to a heater A<1>, from which vapours pass to the lower part B of a rectifying column B, B<1> heated by steam coils C. Vapours pass off at the top and are condensed in receivers D, D<1>, p the light impurities being run off through a test gauge b while the condensate is returned as reflux through a pipe 5. The partially purified benzene is withdrawn from an upper plate E and passed through a pipe 6 and gauge E<1> to the second rectifier F, F<1>, maintained under such vacuum that the boiling point of benzene is reduced from 80 DEG to about 50 DEG C. The benzene is rectified in this column without external heating by pumping the liquid from the bases of the column through pipes 12, 13 into the condenser D, where it is boiled by exchange of heat from the vapours from the column B<1>. The vapours are returned to the column through the pipe 15, and the vapours leaving the top of the column are condensed in a condenser G and the condensate is divided into two parts, one part being returned through the pipe 10 as reflux while the other is mixed with steam in an ejector 8, thus creating a vacuum in the tower F, and is used for heating the heater A<1>, the condensate formed passing to a cooler J and separator J<1>. The purified benzene is removed through a cooler H to a test gauge l. The residues from the column B, B<1> are passed through a pipe 9 through a steam lift emulsifier L into columns K, Q, where the toluene is doubly rectified in a similar manner to the benzene, and finally the residues from the column K are transferred through a pipe 34 into a boiler T and the vapours are rectified in a column S to give xylenes which are removed through a pipe s and cooled in a condenser s<1> and solvent naphtha drawn off through a test gauge j.