GB401508A - A process for cracking tar oils or crude tars by heating under pressure in the liquid phase - Google Patents

Abstract

<PICT:0401508/III/1> Oils are cracked by passing the crude oil into a distillation column in which it is fractionated into a benzine distillate, middle oils, and pitch, the middle oils being circulated through a cracking coil and the products returned to the distillation column in which they are expanded in contact with the pitch and part of the crude oils. Crude oil preheated in a heat exchanger 54 is pumped from a tank 13 through a line 47 on to trays of a fractionating column 38 surmounted by an upper plate column 55. Fractionation may be aided by a steam coil 58 and the benzine fraction passes off through a line 74 and condenser 76 to a separator 77 from which water is removed through a pipe 80 and gases through a pipe 86 while the condensate is collected in a receiver 85 or refractionated if required in a column 90 and condenser 103. The middle fractions are collected from plates in the column 55 and pass through pipes 59, 65, 66 to receivers 62, 70, 73 from which they are pumped to the cracking coil 3 and recirculated to the bottom of the fractionating column through a line 6. The cracked products pass through a weighted valve 4 into an oil bath maintained at the bottom of the column by pumping part of the crude oil through a line 51 and by passing part of the residual oil from the bottom plate 38 through a line 41. The cracked products injected upwardly through a cone-shaped pipe 19 against a baffle 20, distil the oil in the bath 15 to a pitch which is removed continually through a cooler 16 to a receiver 18. The cracked vapours then pass upwardly through a central pipe 24 formed in an evaporating vessel 23, in which the residual oil flowing from the upper part of the column is heated indirectly by the vapours, the liquid being maintained at a constant level by an overflow 26 and syphon 27 which discharges the heavy residues through a pipe 28 and cooler 31 to a receiver 33. The heat exchanger 54 is heated by flue gases from the furnace 1. The oil cycled through the cracking coils becomes gradually enriched in naphthalene.