GB782051A - Improvements in or relating to countercurrent contacting of fluids - Google Patents

Abstract

<PICT:0782051/III/1> <PICT:0782051/III/2> A process for effecting continuous counter-current contact, in a plurality of superimposed contacting zones separated by horizontal perforated partitions, between a liquid introduced into the highest zone and a fluid which is lighter than and incompletely miscible with the liquid introduced into the lowest zone, comprises maintaining upper and lower layers of fluid and liquid respectively in at least two zones; passing liquid from the lower layer downwardly through the perforations of the partition into the next lower zone and therein in dispersed state through the upper layer into the lower layer; passing the fluid from the upper layer at approximately the interface between layers through at least one transfer conduit in a substantially unbroken stream into the upper layer in the next higher zone; and regulating the withdrawal of liquid from the lowest zone so that the interface in the highest zone containing two layers is maintained below the outlet of the transfer conduit. From 2 to 200 contacting zones may be used. The process may be used for liquid-liquid or liquid-gas contacting, for example for extracting aromatic compounds from hydrocarbons such as petroleum fractions containing also paraffinic and/or naphthenic or olefinic hydrocarbons, using as selective solvent such organic liquids as furfural, phenol and glycols, e.g. diethylene, triethylene and dipropylene glycol and b ,b 1-dipropionitrile; for removing phenols or sulphur-containing compounds from gasolines with aqueous caustic alkali solution; and for removing phenols from gasoline with amines. The extraction of a petroleum fraction, containing benzene and other aromatic hydrocarbons boiling at 65-81 DEG C., with aqueous diethylene glycol solution preferably containing 5-15 per cent of water, is described. With reference to the extraction column shown in Fig. 1, naphtha is introduced into the column by conduit 3 and flows upwards as the continuous phase through transfer conduits 6, 18, 19, 20, 21 and 22 and is withdrawn through conduit 23. The solvent enters the column through inlet 7 which may have a spray head 8 attached to the end of the conduit, and flows downwardly through perforated plate 2 and the remaining plates and is withdrawn from conduit 9. A liquid level indicating device may be provided, for example by ball float 10 placed at the interface on the uppermost plate 2. The transfer conduits may be designed as shown in Fig. 2. Methods of starting-up the process are described.