GB403436A - Improvements in or relating to the filtration of slimes - Google Patents

Abstract

403,436. Filters. HENRY, R. A., 78, Quai de Rome, Liege, Belgium. March 22, 1933, No. 8636. Convention date, June 24, 1932. [Class 46.] In apparatus for filtering slimes wherein transverse filter buckets 8 in cavities 7 formed by radial partitions on a rotary drum 3 are subjected alternately to vacuum and compressed air, the buckets are in the form of deep pockets and receives the slimes under an external pressure greater than atmospheric. Two drums 3 may be mounted on pressure distributers 4 one on each side of an intake 2 having supply ports 6. The buckets 8 may be formed of cloth or melted fabric or of thick wire gauze whereon a fine gauze is soldered and the edges of the gauze may be embedded in frames 8a, Fig. 2, which are secured on the cavities by bolted cover frames 8b. The distributer 4 places the buckets travelling round an annular channel 4d in communication with a vacuum through holes 3a, and ports 4a, 4c in the channel. The caked slime is blown out when an aperture 3b in a cavity registers with an orifice 4f on the distributer and communicating with compressed air by a port 4b. The slime is introduced under a head of pressure provided by a tank arranged above the apparatus, such pressure being maintained by a leakproof casing 5. The tank may be fifty feet above the apparatus and the pressure may be increased by the velocity of the liquid introduced. The drums are relatively displaced by half the angle of their cavities and are thus filled alternately so as to limit the effect of the pressure on the filters. To prevent clogging the slime may be subjected to a preliminary treatment consisting in flocculation of the slime in suspension by alkaline earth hydroxides, particularly lime, or by a sol made with starch treated with alkaline hydroxides, or by both. Alternatively the slime may be mixed with amylaceous substances treated with caustic soda as by adding starch and alkali separately or together as a gel or as starch paste or as an unstable sol formed by partial reaction between the starch and alkali.