Process for bleaching medium consistency pulp with ozone using a pressurized fluidizing mixer
AssigneeAndritz Inc.
InventorsKaj Henricson, Torolf Laxen, Juhani Peltonen
Life of this patent
Estimating the term…
Abstract
A method of bleaching cellulose pulp with ozone includes pumping cellulose pulp in form of a fiber suspension having a consistency range of 5 to 25% with a high-consistency pump to a fluidizing mixture in which oxygen and ozone containing gas is introduced and mixed into the pulp so as to generate a foam whereby the pulp fibers and the ozone used as the bleaching agent are brought to contact with each other, bleached, and the pulp is discharged from the mixer to a reaction vessel.
Claims21
A process for the chlorine free bleaching of cellulose pulp in an aqueous suspension at a consistency of 5-25%, using a pressurized fluidizing mixer and a reaction vessel, comprising the steps of:
- (a) forming a suspension of cellulose pulp having a consistency of 5-25%;
- (b) introducing a mixture of ozone as the only bleaching agent, and oxygen as a carrier gas for the ozone into the cellulose pulp having a consistency of 5-25%, and intimately mixing the ozone-containing gas and pulp together in the pressurized fluidizing mixer, to produce a reaction mixture;
- (c) transferring the reaction mixture from the pressurized fluidizing mixer to a pressurized reaction vessel, and continuing ozone bleaching of the pulp in the pressurized reaction vessel;
- and
- (d) discharging ozone-bleached pulp from the pressurized reaction vessel.
A method of bleaching cellulose pulp having a consistency of 5-25% with ozone, comprising the steps of:
- pumping the cellulose pulp at a consistency of 5-25% to a pressurized fluidizing mixer;
- introducing a mixture of oxygen and ozone gas into the cellulose pulp having a consistency of 5-25%;
- mixing the gas mixture with pulp in the pressurized fluidizing mixer to form a foam-like mixture composed of fibers, liquid, oxygen and ozone, and to provide contact between the fibers and the ozone acting as the bleaching chemical;
- ozone bleaching the pulp while in said foam-like mixture;
- discharging the pulp from said pressurized mixer into a bleaching reactor;
- and
- separating from the pulp, after bleaching, oxygen as the main residual gas.
Dependencies are inferred from the claim text.