Method for centrifugally removing liquid from a mixture

Abstract

Abstract A method and apparatus for continuously removing, through a centrifuging operation, liquid from a mixture including therein a cellulose fiber pulp of organic origin which is used or could be used in the making of paper. The method involves impinging the mixture upon a rotating screen surface to form a layer of lightly compacted, relatively porous, fibrous material thereon and passing a portion of liquid through said porous layer of material and through said screen followed by effecting a further removal of the liquid from said mixture by cleaning said screen surface by moving the edge of a transportating member adjacent said screen surface while simultaneously producing and maintaining a mass of densely compacted, relatively impervious, fibrous material between said edge and said screen and using said mass to remove continuously from said screen surface fibrous material deposited thereon, and rolling, wringing and redepositing said fibrous material upon said screen surface while passing additional liquid through said screen and moving said fibrous material along said screen surface. The mixture is centrifuged at a force varying within a range between approximately 70 and 650 times the force of gravity. The fibrous material passing with the liquid through the screen is recovered by impinging the liquidfibrous material upon the surface of a second screen. The method may also be used with a mixture containing fibers which are relatively short in length by adding to said mixture a predetermined quantity of fibers having a relatively long length. The apparatus comprises a hollow, rotatably mounted screen means, a scroll member rotatably mounted concentrically within said screen means, and means for rotating the scroll member at a predetermined angular velocity differential relative to the angular velocity of rotation of the screen means. The screen means preferably has a circularly shaped inner surface and a plurality of openings formed therethrough, the minimum dimension of said openings, taken in a direction generally normal to the longitudinal axis of said openings, varying within a range of not less than approximately 0.3 millimeters nor more than approximately 3 millimeters. The scroll member has a plurality of helical flights formed on the surface thereof so constructed and arranged to prevent fibrous material from ''''bridging'''' between adjacent flights. This construction and arrangement includes helical flights disposed to form an included angle with a plane disposed perpendicular to the longitudinal axis of the scroll member not more than approximately 65*, and perpendicularly spacing each flight from an adjacent flight by an amount equalling at least approximately 0.03 and preferably 0.04 times the inner circumference of the screen means. The clearance between the edge of each flight and the inner surface of the screen means adjacent the end into which the mixture is supplied to the apparatus equals approximately not more than 0.004 times the inner diameter of the screen means. A relationship exists between certain structural parts of the apparatus whereby, upon operAtion thereof, the fibrous material is retained upon the inner surface of the screen means at least approximately 1 1/2 seconds and preferably about 3 seconds.

Inventors

• 👤 P Wilson
• 👤 R Hughart

Bibliographic Details