GB812474A - Method and apparatus for continuous multistage counter current contacting of liquidswith vapors - Google Patents

Abstract

<PICT:0812474/III/1> <PICT:0812474/III/2> In the treatment of viscous liquids with vapours, efficient contact between the two phases is achieved by passing the vapour through tube 20 continuously into one end of a substantially horizontal elongated chamber 20 and introducing the liquid through tube 17 into the other end of the chamber so that its general flow is countercurrent to that of the vapour; the liquid flows through at least ten liquid pools in the lower part of the chamber, these pools being bounded by rings 16 which are spaced along the chamber and form weirs for the liquid; sprays of liquid from each pool are projected across the vapour stream by impellers 13 mounted at spaced intervals along a rotating shaft 12; the sprayed liquid coalesces on the upper wall of the chamber and then flows down the sides between the upper parts of the rings 16 into the same pool from which it was projected. Most of the liquid in each pool at any time is sprayed several times across the vapour stream before it weirs over into the next pool. The apparatus may be used for steam-stripping free fatty acids and odoriferous components from fats and oils of the glyceride type. The following oils are referred to: soybean, linseed, cottonseed, peanut, corn, whale, menhaden, sardine, lard, and also hydrogenated vegetable, marine and animal oils. The fat or oil is preliminarily treated to effect deaeration and is thereafter heated to the desired processing temperature, e.g. 200-270 DEG C. The stripping operation is preferably carried out at a pressure below 25 mm. Hg. Steam is the preferred stripping vapour, but lower boiling alcohols and hydrocarbons, such as hexane, can also be employed. The apparatus may also be used for the recovery of volatile components from tall oil, the distillation of fatty acids, the removal of tocopherols and sterols from natural oils, the recovery of solvent from solven-extracted animal and marine oils and fats or from solvent-extracted mineral oils such as lubricating oils, the steam-stripping of tars, and for the removal of absorbed hydrocarbons from oils used in connection with the recovery of desirable hydrocarbons from natural and refinery gases. Chamber 10 is generally inclined at a slight angle, e.g. 1 to 10 degrees to the horizontal in order to assist liquid flow. A small amount of liquid, as it drains down the sides of chamber 10, will flow through openings 38 in the dividing rings 16 (Fig. 2); these openings are above the liquid level in the pools. Chamber 10 is surrounded by a jacket 39, through which a heating medium, such as steam or diphenyl-diphenyl oxide, can be passed in order to control the temperature of the phase-interchange. The treated liquid is withdrawn via tube 19. The effluent vapour passes through baffles 29, 30 to remove entrained liquid droplets, and is then withdrawn via tube 18, which is connected to condensers, receivers and the vacuum pump. When used for continuous fractional distillation, means are provided for returning part of the condensed overhead as reflux to the right-hand end of chamber. Examples 1, 2 and 3 relate to the steam treatment of a mixture of refined corn oil and 1 per cent by weight of lauric acid, the speed of the rotor being 1680 R.P.M. Example 4 relates to the deodorization of shortening comprising hydrogenated soybean oil together with a small percentage of hydrogenated cottonseed oil and other vegetable oils. The melted fat was de-aerated before the test. Example 5 relates to the refining of lard. Examples 6 and 7 relate to the fractional distillation of a mixture of trans-decahydronaphthalene and n-decane at a pressure of 18 mm. Hg. In this case, one end of the contacting chamber is connected to a pot-still for the distilland, and the other end is connected to a refluxing still-head.