GB692704A - Method and device for the purification or treatment of liquids - Google Patents

Abstract

692,704. Filters; purfying liquids. MADE. D. VAN DER, and SMIT, P. Feb. 14, 1950 [Feb. 24, 1949], No. 3778/50. Class 46 [Also in Group VI] Liquids to be purified by filtration or by ion-exchange are passed mainly in the upward direction through a mass of material, the grains of which gradually decrease in size from the bottom to the top, to a draining system disposed in the upper part of the mass. The method may be carried out in an open or closed tank in which the filtering- or treating-material rests on a permeable support, and the draining system is so shaped that a minimum resistance is offered to the liquid current during cleaning or regeneration. Surface water containing 2.1 mg. iron per litre and having a total hardness of 15 degrees is intensively aerated, mixed with 3 mg. Al 2 (SO 4 ) 3 per litre and then passed upward through a perforated copper plate C, Fig. 2, and layers of successively finer gravel (ranging for example from 20 mm. to 1.5 mm.) at a rate of 10 cubic metres per hour. It leaves by a web of perforated copper tubes E covered with copper-nickel gauze of 1 mm. mesh. The outlet tube F is surrounded by dishshaped discs to prevent short-circuiting. Ten per cent of the filtered liquid is raised by a pump R to a distributing channel K whence it falls on the bed to prevent a "break-through" by the rising liquid. For cleaning, valve 6 is closed and valve 1 opened, and 2 cubic metres of water and air per minute passed upwardly through the bed. Finally 2 cubic metres per minute of water only is passed for two minutes. A (sugar) diffusion-juice having a pH of 3.8 may be partially decolorized from black to pale yellow with this apparatus. For obtaining a clear juice from sugar-beet juice a vessel A, Fig. 3, is provided with a coppernickel perforated plate C<SP>1</SP> supporting a layer of 10 mm. gravel and a layer of cation-exchange material having a grain size of less than 0.5 mm. The juice is supplied simultaneously to the bottom and top of the bed through a connection D and valve 4 respectively, from a pipe M, at a rate per hour of ¥ volume juice per volume of cation-exchange material. An air-release valve 5 is opened as necessary. The purified juice leaves by a perforated hollow sphere E of rustproof steel covered with copper-nickel gauze. The outlet tube F is again provided with dish-shaped discs G. When the effluent is no longer satisfactory the filter is sweetened-off by passing water through a valve 8 and open dish K and through valve 7 and the sphere E to the upper part of the bed. The water passes away by the connection D and valve 2. Valves 3, 4 and 6 are closed during this operation. For the regeneration step which follows a cover B is opened, and steam and air are admitted through valve 2, the filter being then partly filled with water, until the whole mass is loose. Alternatively, steam and either air or water are admitted through an annular tube S having peripherally distributed injectors T. Half the requisite quantity (50 kg.) of regeneration acid (H 2 SO 4 ) is admitted via D and valve 2, the remaining valves being closed, and the mass is boiled by blowing in steam. Valve 1 in pipe L is next opened, and water is admitted through valve 2 at a speed such that the particles are freely-suspended but not carried away. The mass is allowed to settle and 50 kg. H 2 SO 4 in 6 per cent solution are added via valve 8 and dish K and washed out with water following the same path. A washing with lye may precede the acid-regeneration step. Examples of treating or filtering materials are: activated carbon, gravel, sand, granular coke, pumice stone, coal, quartz, infusorial earths combined or not with gravel or sand. The liquid is preferably homogenized for example by intensive stirring before treatment. The filter may be vibrated during settlement of the material after washing. Normal washing may be followed by boiling or sterilizing by SO 2 . In a modification of the apparatus, not shown, an excess pressure of air or of raw or partially purified liquid is maintained in a bell-shaped cover which surmounts the filter surface immediately surrounding the outlet tube.