Reactor for bleaching high consistency pulp with ozone
AssigneeUnion Camp Patent Holdings, Inc.
InventorsDavid E. White, Michael A. Pikulin, Thomas P. Gandek, William H. Friend
Life of this patent
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Abstract
An apparatus for delignifying and bleaching a lignocellulosic pulp without the use of elemental chlorine. The bleaching reactor is a horizontal vessel having a central rotatable shaft which preferably contains paddles, cut and folded screw flights or a ribbon flight, to disperse and advance the pulp particles in a plug flow manner while contacting and mixing the pulp particles with a gaseous bleaching agent such as ozone for substantially uniform bleaching thereof.
Claims29
A high consistency pulp/ozone bleaching reactor apparatus for ozone bleaching of high consistency pulp particles having a consistency of above 20%, a first GE brightness, and a particle size sufficient to facilitate substantially complete penetration of a majority of the pulp particles by ozone when exposed thereto, to a second, higher GE brightness, said apparatus comprising:
- a shell having a pulp inlet and a pulp outlet;
- means for introducing high consistency pulp particles into the shell;
- a source of ozone containing gaseous bleaching agent;
- means for introducing a flow of said ozone containing gaseous bleaching agent into the shell to provide an ozone containing gas phase within said shell;
- a shaft extending through the shell along a longitudinal axis thereof and having a first end adjacent to the pulp inlet and a second end adjacent to the pulp outlet;
- and
- a plurality of paddle blades extending radially from the shaft and being sized, positioned and oriented in a predetermined pattern defining a pitch to simultaneously provide
- (a) means for exposing substantially all surfaces of a majority of the high consistency pulp particles to the gaseous bleaching agent to allow approximately equal access of the ozone to all pulp particles by lifting, displacing and tossing the pulp particles in a radial direction to disperse the particles along the periphery of the shell and suspend pulp particles in the gas phase,
- (b) means for advancing the dispersed and exposed high consistency pulp particles through the shell in an axial direction in a plug-flow like manner with a dispersion index of about 4.8 or less, and
- (c) means for advancing the high consistency pulp particles though the shell in the axial direction with a predetermined pulp residence time sufficient to maintain a fill level of at least about 10% of the dispersed pulp particles in said shell;
- whereby substantially uniform bleaching by reaction with said ozone throughout the majority of the pulp particles is achieved to form a bleached pulp having the second GE brightness.
A high consistency pulp/ozone bleaching reactor apparatus for ozone bleaching of high consistency pulp particles having a consistency of above 20%, comprising:
- a shell having a pulp inlet and a pulp outlet;
- means for introducing high consistency pulp particles into the shell at the pulp inlet;
- means for introducing a flow of ozone containing gas into the shell to provide an ozone containing atmosphere within said shell;
- a shaft extending through the shell along a longitudinal axis thereof with a first end adjacent to the inlet and a second end adjacent to the outlet;
- and
- paddles extending radially from the shaft positioned approximately at 240.degree. spacings in a helical quarter-pitch pattern along at least a portion of the shaft, wherein said paddles are configured and dimensioned for lifting, displacing and tossing the pulp particles along the radius of the shell to increase radial dispersion of the pulp and suspend a majority of the pulp particles in the ozone containing gas, while simultaneously conveying the pulp particles axially through the shell with a fill level of dispersed pulp particles of at least about 10% in a plug flow-like manner having reduced axial dispersion to provide a dispersion index of less than about 8, said paddles being disposed around said shaft to provide at least one predetermined conveying rate at a predetermined speed.
Dependencies are inferred from the claim text.