High efficiency fiber bleaching process
AssigneeGPCP IP Holdings LLC
InventorJeffrey A. Lee
Life of this patent
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Abstract
A high efficiency bleaching method for cellulosic pulp includes: (a) providing a charge of aqueous cellulosic pulp to a bleaching vessel at a consistency of from 10% to 30% along with a peroxy bleaching agent and an alkaline agent effective to adjust pH of the charge to 9.5 to 12.5; and (b) bleaching the aqueous cellulosic pulp in the bleaching vessel while maintaining a bleaching temperature of from 110° F. (43° C.) to 135° F. (57° C.) and a pH of the charge from 9.5 to 12.5 for an extended bleaching retention time. The bleaching method is advantageously used to bleach low brightness recycle pulp, and/or as part of a multistage process with bleaching stages of lesser duration, and/or as a high peroxy efficiency, low dose bleaching process or in connection with concurrently storing and bleaching pulp.
Claims20
A multi-stage bleaching process for aqueous cellulosic pulp comprising:
- (a) bleaching the aqueous cellulosic pulp in an extended duration bleaching stage including:
- (i) providing the aqueous cellulosic pulp to the extended duration bleaching stage at a consistency of from 10% to 30% along with a peroxy bleaching agent and an alkaline agent effective to adjust pH of the charge to 9.5 to 12.5;
- (ii) bleaching the aqueous cellulosic pulp in a bleaching vessel while maintaining an extended duration bleaching temperature of from 43° C. to 57° C. and a pH of the charge from 9.5 to 12.5 for a bleaching retention time in the extended duration bleaching stage of at least 10 hours;
- and
- (b) followed by a Y bleaching stage of lesser duration or a P bleaching stage of lesser duration or both, wherein the Y bleaching stage comprises bleaching with a reductive bleaching agent, for a retention time of from 5 minutes to 3.5 hours while maintaining a bleaching temperature of from 50° C. to 110° C. and the P bleaching stage comprises bleaching with a peroxy bleaching agent, for a retention time of from 5 minutes to 3.5 hours while maintaining a bleaching temperature of from 50° C. to 110° C.,
- and wherein the aqueous cellulosic pulp is recycle pulp having an ISO brightness of from 40 to 65 prior to bleaching.
A high efficiency bleaching method for cellulosic pulp comprising:
- (a) providing a charge of aqueous cellulosic pulp to a bleaching vessel at a consistency of from 10% to 30% along with a peroxy bleaching agent and an alkaline agent effective to adjust pH of the charge to 9.5 to 12.5;
- and
- (b) bleaching the aqueous cellulosic pulp in the bleaching vessel while maintaining a bleaching temperature of from 43° C. to 57° C. and a pH of the charge from 9.5 to 12.5 for a bleaching retention time of at least 10 hours such that from 0.1 kg-moles bleaching agent/metric ton of dried pulp to 2.4 kg-moles bleaching agent/metric ton of dried pulp are consumed in bleaching the aqueous cellulosic pulp in this step (b),
- and wherein the aqueous cellulosic pulp is recycle pulp having an ISO brightness of from 40 to 65 prior to bleaching;
- (c) followed by a Y bleaching stage or a P bleaching stage or both, wherein the Y bleaching stage comprises bleaching with a reductive bleaching agent, for a retention time of from 5 minutes to 3.5 hours while maintaining a bleaching temperature of from 50° C. to 110° C. and the P bleaching stage comprises bleaching with a peroxy bleaching agent, for a retention time of from 5 minutes to 3.5 hours while maintaining a bleaching temperature of from 50° C. to 110° C.
Dependencies are inferred from the claim text.