GB1075005A - Improvements in or relating to centrifugal air classifiers - Google Patents

Abstract

1,075,005. Centrifugal classifiers. ASSOCIATED PORTLAND CEMENT MANUFACTURERS Ltd. Sept. 8, 1965 [Dec. 11, 1964], No. 38374/65. Heading B2P. In an air classifier comprising a casing 22, Fig. 1, in which is mounted a rotor 2 having a top plate 52 and a bottom shroud plate 53', 4 with radial blades 5 extending therebetween, the shroud plate 53', 4 is sloped downwardly and outwardly to permit gravity to assist in the rejection of particles at or near "cut" size and not normally rejected by centrifugal force exceeding the drag exerted by the inwardly flowing carrier air, means being provided for introducing material to be classified into the rotor in a direction such that it is thrown by centrifugal force across the air stream through the classifying zone. The bottom plate of the rotor is made up of two sections, the outer section 4 being integral with a horizontal plate 54 and the section 53' being integral with the lower end of a feed duct 32. The sections 4 and 53' are spaced apart to define an annular opening 58 for the entry of material into the classifying zone of the rotor. Alternatively, entry may be by means of a series of slots. Material to be classified is fed from a hopper 33 down the duct 32 and is thrown by centrifugal force in the space between the plate section 53' and the plate 54 and thence into the rotor interior via the slot or slots 58. Carrier air is introduced via a pipe 31 into a volute chamber 34 and passes via an annular passage 57 to the outer periphery of the rotor through which it flows radially inwardly entraining with it fine particles to be discharged centrally and upwardly into a volute chamber 35 and an outlet pipe 36. Coarse particles are thrown outwardly from the rotor under the action of the predominantly acting centrifugal force and are rejected through an outlet 15. 'Cut' size particles, which may rebound against the top plate 52 of the rotor and thereby liberate any fine adhering particles, pass under gravity down the sloping bottom plate 53', 4 and leave the rotor with the rejected coarse particles. Radial vanes 52' reduce leakage of air over the top of the rotor. In a modification, Fig. 2 (not shown), the rotor has a bottom plate section 54' extending horizontally beyond the entry slot 58 and the outermost plate section 4' is at an angle instead of being curved as in Fig. 1. Material to be classified is fed with air through a pipe 60, the carrier air being introduced as before via a volute chamber.