High Efficiency Fiber Bleaching Process

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 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 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.