Method of bleaching high consistency pulp with ozone
AssigneeUnion Camp Patent Holdings, Inc.
InventorsDavid E. White, Michael A. Pikulin, Thomas P. Gandek, William H. Friend
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Abstract
A method for delignifying and bleaching a lignocellulosic pulp with a gaseous bleaching agent in a reactor 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.
Claims24
A method for bleaching pulp particles having a high 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 a gaseous bleaching agent when exposed thereto, to a second, higher GE brightness which comprises:
- introducing high consistency pulp particles having a consistency of above about 20% into a reactor at a fill level of at least about 10%;
- introducing an ozone containing gaseous bleaching agent into the reactor;
- and
- intimately contacting and mixing the pulp particles with the ozone by lifting, displacing and tossing the pulp particles in a radial direction to disperse the pulp and expose substantially all surfaces of the majority of the pulp particles to the gaseous bleaching agent while advancing the dispersed pulp particles axially through the reactor in a plug-flow like manner and at a dispersion index of below about 4.8 for a predetermined time to obtain substantially uniform bleaching throughout the majority of the pulp particles and to form a bleached pulp having the second GE brightness.
A method for ozone bleaching of pulp particles having a high 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 a gaseous bleaching agent when exposed thereto, to a second, higher GE brightness which comprises:
- introducing an ozone containing gaseous bleaching agent into a reactor to provide an ozone containing atmosphere therein;
- introducing high consistency pulp particles having a consistency of above about 20% into the reactor at a fill level of at least about 10%;
- and
- intimately contacting and mixing the pulp particles with the ozone by lifting, displacing and tossing the pulp particles in a radial direction to disperse the pulp particles along the radius of the reactor to suspend a majority of the pulp particles in the ozone containing atmosphere, thereby exposing substantially all surfaces of the majority of the pulp particles to the gaseous bleaching agent while advancing the dispersed pulp particles axially through the reactor in a plug-flow like manner and at a dispersion index of below about 4.8 for a predetermined time to obtain substantially uniform bleaching throughout the majority of the pulp particles and to form a bleached pulp having the second GE brightness.
A method for ozone bleaching of pulp particles having a high consistency of the above 20%, comprising:
- introducing an ozone containing gas into a reactor having first and second ends;
- introducing high consistency pulp particles having a consistency of above about 20% into the first end of the reactor;
- advancing the high consistency pulp particles through the ozone containing gas axially from the first end to the second end of the reactor in a plug flow like manner and at a dispersion index of below about 4.8;
- radially dispersing the high consistency pulp particles into said ozone containing gas to continually expose substantially all surfaces of the majority of the pulp particles to the ozone containing gas, said dispersing occurring simultaneously with said advancing;
- and
- maintaining a predetermined fill level of the dispersed high consistency pulp particles in the reactor, said predetermined fill level being between about 10% to 50%.
Dependencies are inferred from the claim text.