GB688690A - Improvements relating to the continuous extraction of substances from solid matter by means of a solvent - Google Patents

Abstract

<PICT:0688690/III/1> <PICT:0688690/III/2> A process for the continuous extraction of liquids from solids, and especially oil from seeds, with the aid of solvents comprises placing the solid, preferably ground, on an endless gridded conveyer, sprinkling a solvent on to the said solid as it is conveyed and stirring the upper layer of the solid to be treated. As shown, a hopper 2 feeds ground seeds on to an endless chain conveyer 5 and the thickness of the layer so formed is adjustable by means of a gate 3. The conveyer 5 has rollers 39 circulating on a track 40 and engaging recesses 43 in a driving drum 6 and loose drum 45 positioned at the discharge and charging ends of the conveyer respectively. The drum 6 is driven by motors 48 or 49. Fig. 4, through the speed reduction gear 77. The speed of p the conveyer is automatically controlled by the pressure of the feed exerted on a diaphragm 47, preferably of synthetic resin, which is provided in one of the walls of the hopper 2. The diaphragm controls a mercury change over switch 50 which in turn acts through coils 74 and 75 to bring either motor 48 or motor 49 into action. The speed of one motor is twice that of the other. A second diaphragm 85 cuts out the motors as the hopper empties. Fresh solvent entering the system at 56 is sprinkled through atomizers 16 on to the exhausted seeds at the discharge end of the conveyer and, after percolating through the seed bed, collects in a tank 55, overflows at 30 into the adjacent tank 23 and is forced from the base of the tank 23 by pump 8 to atomizers 17, whence it falls on and percolates through the layer of seeds above the tank 23. The counter-current extraction proceeds through tanks 24 to 29 with their associated pumps 9 to 13 and atomizers 18 to 22, the most highly concentrated extract at 29 overflowing into a tank 31, from which it is pumped to the solvent recovery unit. The pumps 8 to 13 are individually regulated at e.g. 57, 58 and 59 to allow for the different permeability of the seed layer at various stages in the extraction. The atomizers consist of a feed device formed by a vertical liquid supply pipe closed at its bottom by a movable plate and positioned in the centre of a distribution means having a series of vertical bars 69, Fig. 3 (not shown), distributed in space along concentric cylindrical surfaces. The arrangement ensures uniform distribution of the liquid over the seed area to be sprinkled. As the seeds are conveyed above the first half of a collector tank they are sprinkled with liquid from an atomizer. During the second half of their passage above the said tank they drain. Freely oscillating rakes 51 stir the seed bed at the limit of the zone which is sprinkled by the atomizers and in so doing form a slope which is situated in the draining zone. This arrangement prevents mixing of liquid extracts of different concentrations. The assembly is totally enclosed and can be worked under pressure. Specification 616,825 is referred to.