GB664589A - Method for the continuous separation of tars by distillation - Google Patents

Abstract

<PICT:0664589/III/1> <PICT:0664589/III/2> In the continuous distillation of tar in which preheated tar is subjected to a flash evaporation and the vapour products then subjected to fractionation in one or more fractionating columns, the bottom product of the or each column is heated, to enable the quantity of reflux returned to the column to be increased, by indirect heat exchange with the pitch residue from the flash evaporation In the arrangement of Fig. 1 tar is fed at about 3 atmospheres pressure to a chamber V where it is flashed at 60-100 mm. of mercury the vapours passing to the column KI. Reflux is provided by dephlegmator d and the bottom product is continuously heated by the pitch residue from chamber V flowing through pipe coil e. The bottom product (anthracene oil) is drawn off at f. Uncondensed vapours pass to column KII in which reflux is provided by dephlegmator l and the bottom product is heated by an external heat exchanger i through which flows the pitch residue from pipe coil e. The bottom product is drawn off at m. The vapour passing over at n at about 25 mm. pressure may be rectified in a further column or condensed. In the arrangement of Fig. 2 reflux for the column 4 is provided by a condenser 7 and pump 11 the remainder of the condensate being drawn off at 9. Condensate is taken from an intermediate level in column 4 and fed at 13 to a side column 14 the bottom product of this column being heated by pitch residue from the flash chamber 2 flowing through pipe coil 23 after passing through coil 19 at the bottom of column 4 to heat the bottom product of this column.