GB843536A - Improvements in or relating to the classification or transfer by gravity of solids from a suspension in a liquid - Google Patents

Abstract

843,536. Washing granular materials; mixing appliances. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Oct. 7. 1957 [July 6, 1956], Na. 21041/56. Classes 82(2) and 86 [Also in Group I] Liquid containing suspended solids is pumped at 14, Fig. 1, from a classifier 41 to the tangential inlet 23 of a vessel 11 whence liquid containing solids, if any, below a certain grade (grade being a function of particle size, shape and density) is discharged by a siphon 13 and weir 45, while the remaining solids fall freely through the outlet 11b, at the base of the vessel, which is slightly submerged below a body of liquid (not necessarily of the same kind as that entering the vessel 11) in an open-topped receiver 12. There is no liquid flow into or out of the column at 11b. Hence solids (e.g. sand), may be transferred from liquid (e.g. sea water) in the column to a different liquid, which may also be of lower density (e.g. fresh water) in the receiver 12. There may be an independent flow of liquid through the receiver 12. The upward velocity at the separation level is rendered constant across the cross-section of the vessel 11 by vertically-arranged corrugated sheets in contact, or by a honeycomb structure 25, into which tapering needles 26 extend. The centrifugal pump 14 is operated as a constant head device. The level in receiver 12 is to some extent selfadjusting. Larger fluctuations, or changes caused by adjustment of valve 15 or valve 16 are compensated for by a needle valve 17 linked to a float 22 in a stilling pot 21. The pump may be replaced by a flume discharging into an open hopper having a control valve. The outlet of vessel 11 may be provided with a valve 30, Fig. 4, which may be raised vertically to raise, and close the aperture in a flexible sleeve 31 by a wire 39 and links 35, 32.