Apparatus for thickening pulp and paper stock

Abstract

Embodiments of apparatus for thickening a liquid suspension of solid particles, such as papermaking pulp in water, include a pair of spaced apart rolls and a woven wire or plastic wire belt trained around these rolls. The suspension is supplied to the apparatus at the first roll for centrifugal extraction and is carried by the belt to the second roll for further water extraction and thickening, and is then discharged from the apparatus. In one embodiment, the first roll is formed with an open surface, and the suspension is delivered to the web at least partially by flowing through the first roll openings, from either a headbox in the on-running wedge zone or a headbox internal to the rolls to deliver stock outwardly through the roll. The apparatus may also include a second roll which is porous and has auxiliary water-removing appliances associated therewith, including blow boxes for forcing air either radially inwardly or radially outwardly of the second roll, and an auxiliary nip roll for creating a zone of higher compression for mechanical extraction of water from the mat of solid particles between the belt and the second roll. Rewetting of the mat caused by water entrained in the wire mesh cavities is reduced by the impingement of air jets to remove such water. In a further embodiment, one or both rolls may include a pair of disks spaced apart on a support shaft with the wire belt trained over the outer surfaces of the disks so that a substantial open extent of the belt is defined between the disks. The rolls may be mounted with the plane defined by their axes in any desired spatial orientation, from horizontal to vertical.