GB1237863A - Improvements in and relating to the counter-current washing of solids - Google Patents

Abstract

1,237,863. Sugar extraction apparatus. A. & W. SMITH & CO. Ltd. 14 Aug., 1968 [21 Aug., 1967], No. 38396/67. Heading B1Q. [Also in Division C6] In a process for extracting sugar by diffusion with sugar solution and water or for other treatments of particulate solid materials with liquids, the material is fed into one end of a rotatable cylindrical or polygonal drum 10 within which compartments are formed by a number of transverse discoid members 16 which are preferably conical as shown, each member 16 having a central aperture and adjacent members 16 being interconnected by axially extending flights 50 which are preferably inclined to the radial direction as shown to divide each compartment into a number of pockets, the arrangement being such that when the drum is rotated the sugar cane or other material is entrained by the pockets, raised to nearly the full height of the drum, and then caused to fall in such a way that it drops into the pockets of the next compartment, so as to progress in one direction along the drum, the treatment liquid being caused to move counter to this direction. Four such arrangements are described, each utilizing perforated conical discoid members. In that shown in Fig. 1, the drum is inclined at an angle not greater than 1 in 25 so that the liquid, which in the case of sugar extraction is a dilute sucrose solution obtained from final pressing of the cane following diffusion, can flow from an inlet pipe 30 to an outlet trough 20, passing through the perforations in the discoid members. The portions of cane elevated by the flights 50 are directed successively into compartments further along the drum in the direction of its higher end by a series of baffles 31 mounted on a pair of tubular members 32 which are carried in bearings 33, 39 in supports 34, 38 for axial sliding so that the baffles may be oscillated by a reciprocating mechanism 36 linked to a face plate 35. A motor 15 rotates the drum, which is preferably between forty and a hundred feet long, from twelve to twenty four feet in diameter, and is supported by rollers 11 engaging channels 12, at a speed of about one R.P.M. The discoids divide the drum into between twenty and fifty compartments, and the flights 50 divide each compartment into from six to twelve pockets. Some of the sucrose solution collected in trough 20 or/and water or steam may be fed to the tubular members 32 and sprayed through orifices 44 to provide some recirculation, the liquid inevitably lifted with portions of cane and deposited higher along the drum providing further recirculation. In a second arrangement (Fig 3, not shown), the discoid members are placed closer together so that the baffles can be omitted. In a third arrangement (Fig. 4, not shown), a helical screw (85) carried on a shaft (84) is rotated by a motor (92) to impel material falling from the pockets of one compartment into those of the next higher compartment. In a further arrangement (Fig. 5, not shown), no baffles or impeller is used, the material being moved down the slope, so that the discoid members need not be so closely spaced as in the second arrangement, the ends of the drum being so constructed that the liquid can be fed into the drum at its lower end and discharges from the higher end of the drum. A conventional shredder and milling machine preferably precedes the drum so that sugar cane is reduced to the desired state for diffusion extraction. The sucrose solutions fed into both upper and lower ends of the drum and a water supply, which may be additionally provided at the upper end, are preferably heated to a temperature of between 80 degrees and 100 degrees centrigrade.