Patent GB-634381-A (GB)
Title: Improvements in or relating to film distillation
IPC: B01D3/12
Filed: 1947-01-07
Abstract: <PICT:0634381/III/1> Liquids are submitted to evaporative distillation by causing the heated liquid to flow downwards in the form of a film having two free surfaces, between guide members in close proximity to a condensing surface, the pressure in the space between the guide members and the condensing surface being maintained below the vapour pressure of the heated liquid.  The method is particularly applicable in short-path distillation under reduced pressure.  The condensing surface may be a cooled, solid surface or may be one or more guided, but otherwise free, films of liquid of the same or different composition as the distillate.  A crude petroleum residuum is pumped through heater 131 wherein the temperature of the oil is raised to 400 DEG  F.  The heated oil is degassed in vacuum chamber 151 and then passes to distillation chamber 11 above partition 31 which is provided with apertures 41 extending in a line across a diameter.  A constant head of oil is maintained above the partition by regulating the rate of pumping.  The fine streams of oil passing through the apertures coalesce and form a down-flowing film between guide rods 51 which are suspended from the partition adjacent the end apertures.  The pressure in chamber 11 is maintained at 5 microns by a vacuum pump connected at pipe 101.  Part of the hot oil flowing down between rods 51 vaporizes, and the vapours are condensed on a down-flowing film of cool liquid of low vapour pressure, which is supplied through apertured pipe 23 and guided by rods 22, the latter lying in a parallel plane close to that of rods 51. Undistilled residue drains into funnel 21, is withdrawn through pipe 24, and may either be passed to storage or recycled.  The condensing liquid with the condensate dissolved or entrained therein drains into the bottom of chamber 11 and is withdrawn through line 27.  If the condensing liquid consists of the oil condensate itself, a portion of the withdrawn liquid is pumped through cooler 30 to pipe 23.  It is desirable to provide two condensing films lying on opposite sides of the vaporizing film.  A modified apparatus is described which has four vaporizing films alternating with three condensing films, and which is provided with a settling vessel and a fractionating column for use respectively in the event of the condensing liquid being immiscible or miscible with the condensate.  The strength of the vaporizing film may be increased by the addition of soaps, fatty acids or esters which remain in the film during distillation.  The distillation of the following substances is referred to: lubricating oil; petrolatum; petroleum wax; petroleum acids; petroleum oils containing alkaline and alkaline-earth salts of naphthenic and sulphonic acids; animal and vegetable oils, fats and waxes; resins; sulphuric acid; phosphoric acid; sulphuric or phosphoric acid contaminated with hydrocarbons; decomposable inorganic salt solutions.  The separation of hormones, vitamins and enzymes from fish and vegetable oils is referred to.  A list of suitable condensing liquids is given.