Importance

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Abstract

A mixer, having a unique rotor, is particularly suitable for mixing paper pulp having a consistency of about 6-15% (medium consistency) with a bleaching gas having an ozone content of at least one percent, and typically at least six percent. The rotor comprises a disc shaped base, a hub at the center of the base for connecting it to a drive mechanism for driving the rotor at an angular velocity of 1000-6000 rpm, and one or more rings concentric with the base and extending outwardly from the base at least about three inches (and of the same for different heights). A number of blades may extend radially through the center of the base along the contour of the rings, extending outwardly from the base, rings, and hub. Degassing holes may be formed in the hub and connected up to a suitable degassing structure in the mixer. The rings may have a cross-sectional shape corresponding to that of a truncated right circular cone frustum, or may have a rectangular cross-section. The rotor is mounted in a housing having a pulp inlet and outlet, and the stator has complimentary shaped cooperating surfaces with the rotor defining annular mixing volumes, the cooperating surfaces having a spacing of 0.5 inches or less (preferably 0.25 inches or less). The fluid to be mixed with the pulp is introduced into the inlet adjacent the rotor and into the mixing volumes, for example at the extremity of the rings from the base.

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First Claim