GB456422A - Improvements relating to the treatment of hydrocarbon oils with selective solvents - Google Patents

Abstract

In the extraction or de-waxing of oils with solvents, the solvent is recovered from the mixture of oil and solvent by distillation which includes treating with steam in at least the final stage, and the wet distillate so produced is distilled whereby solvent and water are <PICT:0456422/III/1> removed as distillate leaving a residue of anhydrous solvent. The process is applied to oil mixtures containing solvents preferably boiling below 100 DEG C., especially chlorinated hydrocarbons such as chloroform, carbon tetrachloride, dichlorethylene or propylene, ethylene or propylene dichloride, ethylene tetrachloride and mixtures thereof with petroleum ether. A mixture of oil and chlorinated hydrocarbon passes through a pipe 1 and heat-exchangers 2 and 3 to a still 4 which in the first of a series of multiple-effect evaporators operating under different pressures. Vapours from the still 4 pass to the heat-exchangers 2 and 3 and into the heating chamber 9 of a second still 6, operating at a lower pressure than 4, where the vapours are condensed and pass to a cooler 16. Solvent vapours from the still 6 pass through heat-exchanger 2 to a condenser 12 and receiver 13. The oil containing some solvent is withdrawn from the still 6 and enters a stripping column 20 where it is treated in counter current with steam. The oil free from solvent is drawn off through a pipe 21, and the distillate passes through a condenser 24 to a separator 25. Water is withdrawn through a pipe 26 and may be freed from the solvent dissolved therein. The upper layer of wet solvent passes through a preheater 28 to a distillation column 29 through which a current of dry solvent vapour, air, nitrogen or methane rises, and supplied in a preheated condition. The solvent vapours from the still 4 may be used. The column 29 operates at a pressure below that of the still 4. The distillate passes to a condenser 33 and separator 34. The water layer is drawn off and freed from solvent, and the wet solvent layer is returned to the column 29. The residue of anhydrous solvent is drawn off through a pipe 36. The parts of the apparatus which are in contact with chlorinated solvents and water may be made of, or lined with copper, brass or admiralty metal. The Specification as open to inspection under Sect. 91 comprises also the subject-matter of Specification 454,176. This subject-matter does not appear in the Specification as accepted.