Patent GB-737955-A (GB)
Title: Solvent extraction and removal system
IPC: C11B1/10
Filed: 1953-07-17
Abstract: A system for the solvent extraction of oils from solids followed by the desolventizing of the solids comprises an extractor vessel, a desolventizing vessel of similar horizontal cross-sectional area connected thereto to receive solids therefrom and at least one vapour outlet pipe for the removal of vapour from both the vessels.  The vapour recovered from the solvent extract is preferably re-cycled to the extractor; the vapour from the desolventizer is preferably condensed and returned as fresh solvent to the extractor, and the desolventizing vessel preferably comprises desolventizing, deodorizing and toasting zones one above the other.  In the plant shown, a combined extractor 11 and desolventizer 12 is provided.  The extractor 11 is preferably a rotating radial cell type extracted by solvent of increasing oil <PICT:0737955/III/1> <PICT:0737955/III/2> content pumped from drainage compartments 15 as described in Specification 739,602.  After a complete circuit of the cells, their bottom hinged doors successively open and drop the extracted material upon an arcuate impact tray 19 in the desolventizer 12. From the tray 19 the material is swept by rakes to successive steam-heated trays therebeneath, firstly outwardly on the tray 19 and then inwardly on the next tray 21 and in similar sinusoidal manner to the bottom tray 43, Fig. 7.  A restricted cascade zone 26 completes the desolventizing of the solids, and accelerates the velocity of the vapours passing to the outlet pipe 27.  The zone 26a below the zone 26 comprises the deodorizing and toasting zone, steam being supplied through nozzles 50.  Water vapour enters the zone 26 from the zone 26a and assists in the vaporizing of the solvent while it is partly condensed on the solids.  The solvent vapour recovered from the miscella flows through pipe 16 to the extractor and is removed with the vapour and steam from the desolventizer through the pipe 27. After scrubbing with solvent, the vapours pass to a separator 53 and then to a condenser 56 from which the liquid passes to a separating tank 60, the solvent being returned to the extractor through pipe 59. The oil-rich solvent is withdrawn from the extrator through a pipe 62 and fed to a rising-film evaporator 72.  The vapour passes to the pipe 16 and the extracted oil is taken off through pipe 75.  The vapour from the extractor 11 entering the top of the desolventizer is sufficient to ensure that water vapour in the outlet pipe 27 is present in less than azeotropic proportion.  The desolventizer is provided with a central rotatable shaft 23 carrying rake arms 20, 22, 35, &c., with teeth depending therefrom, extending over the trays in each tier thereof to move the solids towards the tray edges.  The trays are alternately circular and annular to permit the sinusoidal movement of the solids, the rakes co-operating with the circular trays having their leading vertical edges nearer to the axis of the vessel for radially outward movement, and the rakes co-operating with the annular trays having their leading vertical edges further from the axis of the vessel for radially inward movement.  The trays may be heated by steam in sectors therebeneath, superposed sectors of the trays being interconnected.