GB721509A - A process for the purification of coal tar - Google Patents

Abstract

<PICT:0721509/III/1> In a process of purifying and distilling tar the crude tar is fed by a pump 1 through a line 2 and heat-exchangers 3, 4 and 5 into a vessel 6 where the preheated tar is treated with high-tension electric currents, then passing into a separator 10 where an aqueous solution of ammonium chloride and other salts is separated out (see Groups XII and XXXVI). The purified tar passes through a heating coil in a furnace 14 leaving the coil at about 330 DEG C. and three atmospheres pressure and then passing through a pressure-reducing valve and line 15 into the base of a fractionating column 16 more or less at atmospheric pressure. Creosote, naphthalene, phenols and lightoil fractions are taken off the column 16 through lines 22, 19, 18 and 17 respectively. The naphthalene and creosote fractions pass into auxiliary columns 20 and 23 from which naphthalene is withdrawn at 21 and creosote at 24. Soft pitch is taken from the base of the column 16 and passed through line 25, heat exchanger 4 and line 26 into a second heating coil in the furnace 14. Heated soft pitch at a temperature below 330 DEG C. passes through line 27 into a column 28 which is maintained under a vacuum of about 90 mm. mercury absolute. Vapours released from the soft pitch pass into an auxiliary column 31 from which anthracene oil is withdrawn through line 33, heat exchanger 3 and line 34. A creosote fraction leaves the column 31 overhead and is condensed in condensers 36 and joins the creosote from line 24. The residue of pitch from the column 28 flows by the line 29 into the base of the auxiliary column 31 and thence by line 31a, heat exchanger 5 to a withdrawal line 32.