Abstract: Nozzle breakage in an atmospheric diffuser for treating paper pulp is precluded by mounting the nozzle to the rotating scraper arm by a connection which will break when the nozzle is subjected to a drag force of about 50% of the force that will break the nozzle. The connection preferably includes a pivot connection of a nozzle extension at one side of the arm, and a shear pin connection of the extension at the end opposite the pivot connection. An oblong nozzle is integral with the nozzle extension, with the fluid introducing openings of the nozzle remote from its connection to the extension. The amount of pivotal movement of the nozzle when the shear pin breaks is limited to about 15.degree.-26.degree. so as to prevent the nozzle from contacting an annular extraction screen of the diffuser.

Abstract: A centrifugal pump for pumping suspensions having a consistency of about 6-20% (for example, for pumping paper pulp) has a second stage for increasing head. An auxiliary impeller is connected to the drive shaft in front of the main impeller, and upon rotation of the drive shaft directs the suspension being pumped axially into association with the main impeller. Mounted between the pump inlet and the auxiliary impeller are a plurality of stationary guide vanes, and mounted on the opposite side of the guide vanes from the auxiliary impeller are a plurality of prefluidizing vanes which are also connected to the drive shaft. The stationary guide vanes remove extreme prerotation of the suspension ahead of the auxiliary impeller, and change the turbulent and chaotic condition of the suspension into a directional flow at a definite angle of entrance. Utilizing the pump of the invention, there is no need to provide a vacuum system in order for the pump to operate properly.

Abstract: An assembly for treating pulp and the like in a vessel by directing an axial flow of bleaching or washing liquid or the like through the pulp, and immediately thereafter removing the spent liquid from the pulp by a straining assembly. The straining assembly includes a plurality of concentric ring-like screens having radially spaced perforated or slotted side plates, a plurality of concentric ring-like headers corresponding in number to the screens and connected to the screens in end-to-end fluid communicating relationship, and a plurality of radially extending axially reciprocal arms. Liquid passing through the screens flows through the headers and through the arms out of the vessel under the influence of pressure differential.

Abstract: A liquid separating screen member is continuously oscillated, with an amplitude larger than the apertures in the screen member face, from a middle position with substantially the same speed in first and second opposite directions. The screen member separates liquid from the suspension of finely comminuted fiber material and the liquid, which suspension is flowing in the first direction. The oscillation prevents fiber mat build-up on the screen face during movement of the screen face either in the first or the second direction. The amplitude of oscillation may be about one-tenth of an inch, and the frequency of oscillations may be about 6 cycles/sec. with the average speed of oscillation of the screen member in both the first and second directions about 2.4 inches per second, and the maximum speed in both directions about 3.8 inches per second. The frequency of oscillation, which is below the natural frequency of the screen member and associated structures, is about at least two cycles per second.