Patent GB-667262-A (GB)
Title: Improvements relating to solvent extraction of oils, fats and waxes from discrete organic materials, such as oleaginous seeds
IPC: C11B1/10
Filed: 1946-05-23
Abstract: <PICT:0667262/III/1> <PICT:0667262/III/2> In the batch method of solvent extraction of oils, fats and waxes from discrete organic materials such as oleaginous seeds, the steeped and at least partially drained mass of material is mechanically withdrawn from the extraction vessel in a substantially uniform continuous stream and successively preheated and percolated with steam (or an equivalent condensable vapour of higher boiling point than the solvent) to evaporate off the residual solvent and then dried, at least the evaporation being effected under reduced pressure.  In one embodiment of the invention, on completion of the extraction process in the extraction vessel 1, Fig. 1, the aperture 9 of the extraction vessel being opened by withdrawal of the sliding baffle 11, the extracted material is withdrawn from the vessel 1 in a uniform, continuous stream which fills the casing of the Redler type of chain conveyer 6 in the manner well known in that type of conveyer, the discharge of the material from the vessel being assisted, if required, by agitating means in the usual manner. The material is raised by the conveyer and in passing through the portion 13 of the conveyer casing is heated by steam introduced through the branch 15 and condensing in the jacket 14.  The preheated stream of material then passes on round the loop 17 of the casing into which steam is directly introduced through the branch 18.  Residual solvent in the extracted material is thereby evaporated and withdrawn from the conveyer casing through the branch 21 to a vacuum pump or exhauster.  Steam condensed in the loop 17 and any entrained solvent drains through the perforated section 20 of the casing and is discharged through the branch 19. The stream of material finally passes through the portion 22 of the conveyer casing lying within the heating jacket 14, in which it is dried, and then to the discharge hopper 23 through which the material falls on the belt conveyer 24.  The empty conveyer chain then continues in its closed path through the downward section 26 and round the loop 7 of the casing to the portion 8, where it again picks up more extracted material.  In a modification, the rising run 10, Fig. 3, of the conveyer casing may be provided with a discharge aperture 28 opening into the upper part of the extraction vessel 103 and controlled by a sliding baffle which may be withdrawn during the steeping process. Material undergoing extraction, together with solvent, can be withdrawn from the bottom of the vessel 103 through the aperture 93, which is also left open by withdrawal of the baffle 113, and carried up the rising run 10 of the conveyer until it reaches the opening 28, through which it is again discharged into the extraction vessel on top of the mass of material therein.  On completion of the extraction process the opening 28 is closed so that the material withdrawn from the bottom of the vessel by the conveyer may be carried onwards past the opening 28 to the preheating, stripping and drying portions of the conveyer.  In a further modification, the extracted material is transferred from the extraction vessel to a chamber (which is under reduced pressure) by means of a steam-jacketted screw conveyer and after vaporization of most of the residual solvent is removed from the evaporator chamber by means of a second screw conveyer in which the remainder of the solvent is stripped from the material by a counter-current of live steam.  The material is then finally dried prior to its discharge from the second conveyer by means of a steam jacket surrounding the delivery end portion thereof.  In a further modification, the extracted material from four extraction vessels is transferred in turn by means of four screw conveyers to a common evaporating chamber which is under reduced pressure and from which a fifth steam-jacketted conveyer extends, by means of which the extracted and partially dried material is steamed, finally dried and discharged.  The screw conveyer casings, instead of being of circular cross-section, may be U-section troughs provided with internal radiant heating elements in the upper corners.  The drying of the extracted material may be effected substantially simultaneously with the stripping of the residual solvent by the use in the latter step of a super-heated vapour (introduced directly into the conveyer casing) instead of ordinary steam.  In this case the separate additional external or internal heating of the final portion of the discharge conveyer may be omitted.  The conveyer may be of the vibrating type.  If of the chain type it may consist of a chain of transverse paddles or U-shaped bars conforming to the cross-section of the casing.