GB912021A - Method and machine for screening pulp - Google Patents

Abstract

912,021. Filters. IMPROVED MACHCHINERY Inc. Sept. 8, 1960 [April 14, 1960], No. 30947/60. Class 46. Both ends of the driving shaft 118, Fig. 2 of a bladed rotor 126, 128, rotating within a fixed outward flow cylindrical perforate screen 130 intended for paper pulp, are sealed so that when the pulp is flung centrifugally outwardly beyond the line 148 by the rotor, a partial vacuum is created in the space so formed, liquid flow direction thus being contrary to the pressure gradient. The rotor blades 126 act to feed the pulp axially over a diametral baffle 124 as in Specifications 852,994 and 853,644 after which it is diluted through a pipe 156. The portions of the rotor blades to the right of baffle 124 may be pitched reversely as in Specification 869,946. If the screen clogs, with consequent rise in internal pressure, a pressure-controlled device (not shown), connected at 86, operates valves to dilute incoming pulp before it reaches the apparatus, or even to cut off the pulp supply and admit only diluent (" black liquor ") until the screen is cleaned and vacuum is restored. Three such screens may be fed in parallel, one of them however, also acting as a secondary screen because to its input are added the rejects from the other two screens. Pulp enters at 116, 112, accepted pulp leaves at 136, and rejects leave at 134. The whole apparatus is arranged between a brown stock blow tank and a black liquor tank (not shown) in a pulp-preparation plant. In Fig. 5 the rejects are subjected to mechanical attrition (for recirculation through a tangential outlet, not shown, or discard at 312 or both) by extensions 129 on blades 126, and by blades 304 on a disc 302 secured to shaft 118, these members co-operating with fixed mutuallyadjustable perforate annuli 308, 317 on a baffle 306. The pitch angle of blades 304 directs the rejects both axially and tangentially. An access cover (not shown) having a sliding bayonet connection with casing 104 is sealed by an inflatable tube.