Method and apparatus for removing solid impurities from fluid suspensions

摘要

832,945. Presses for separating liquids from solids. OWENS, T. M. March 19, 1958 [March 28, 1957], No. 8771/58. Class 46. A method for removing solid impurities from fluid suspensions containing in addition to the impurities other useful solids is characterized in that the solids of the suspension are squeezed against a screen, having openings generally smaller than the impurities, with such force as to adhere the impurities relatively firmly to the screen, the useful solids remaining on the outer surface of the screen and being relatively non-adherent thereto, separating the useful solids from the screen in fluid suspension while leaving the impurities adhering to the screen, and separately removing the impurities from the screen. Incoming pulp 1, Fig. 1, flows from right to left towards a cylindrical screen 5 driven clockwise by contact with a rubber or like roller 10. Water and fine fibres pass through the screen perforations to the screen interior at A. The solids (of which the impurities from a small proportion) form a layer against the screen 5 which is squeezed at the nip of the screen and roller, and the remaining water is forced through the screen to the inner pool 15. The small head of water provided by the pool 15 is chosen to be sufficient to wash away the useful fibres on the discharge side at B, but insufficient to wash away the impurities, which have become adhered to, or embedded in the meshes of, the screen 5. The effluent level can be changed by an adjustable dam 22. Impurities are removed from the screen 5 to a channel 21 by high-pressure fluid from jets 20. In Fig. 3 (not shown), a screen belt runs over two pulleys vertically aligned, the lower one being an open framework occupying the position of the screen 5 in Fig. 1. Four jets (20), for water, steam or chemical cleaning agents are provided. In Fig. 4, the screen belt 51 passes over four pulleys. In Fig. 5 (not shown), the roller 10 is replaced by a horizontally-arranged belt while in Fig. 6, such a belt 1011 is used with a screen belt 511, the dam 22 in both these cases being dispensed with.