Apparatus and method for thickening pulp and paper stock

Abstract

Apparatus and method for thickening a suspension of solid particles in liquid employs three rolls ranged in spaced relation with their axes defining a triangle, and a single loop of wire is trained around and in wrapping relation with all three rolls. With one exception, each of the rolls has in combination therewith a headbox which delivers a flow of the suspension to be thickened in such manner that it is trapped between the wire and the portion of the roll wrapped by the wire so that the trapped suspension is dewatered and concentrated by expression of liquid through the wire. The pulp deposited on the inside of the wire at each of the stations comprising a roll and headbox is ultimately collected from the surface of the one roll having no headbox and is transported out from within the space within the wire loop. In one embodiment, the roll at each roll-headbox station has a grooved surface such that it forms separate strips of pulp on the wire, and the next roll downstream therefrom has a similar grooved surface offset axially from the preceding roll so that it causes strips of pulp to be deposited on the wire between the strips produced by the previous roll. In another embodiment, each of the rolls having an associated headbox is of the open faced type so that the layer of pulp deposited thereby on the wire is essentially continuous across the wire, and the successive open faced rolls thus lay successive uniform layers of pulp on the wire.