BCTMP filtrate recycling system and method

摘要

A process for making bleached pulp comprises contacting an unbleached pulp mixture with a first recycled filtrate obtained from a first location (3) of a first recycled filtrate loop, to obtain a first pulp mixture having a first consistency; bleaching the first pulp mixture, to obtain a first bleached pulp mixture; pressing or dewatering the first bleached pulp mixture, to obtain a first pressed bleached pulp mixture and a second filtrate; sending at least a portion of the second filtrate to a second location (5) of the first recycled filtrate loop, wherein the second location (5) is downstream of and in fluid communication with the first location (3); contacting the first pressed bleached pulp mixture with a second recycled filtrate obtained from a third location (6) of the first recycled filtrate loop, to obtain a second pulp mixture having a second consistency, wherein the second consistency is greater than the first consistency, and wherein the third location (6) is downstream of and in fluid communication with the second location (5); bleaching the second pulp mixture, to obtain a second bleached pulp mixture; pressing or dewatering the second bleached pulp mixture, to obtain a second pressed bleached pulp mixture and a third filtrate; sending at least a portion of the third filtrate to a fourth location (8) of the first recycled filtrate loop, wherein the fourth location (8) is downstream of and in fluid communication with the third location (6); and recycling at least a portion of the third filtrate in the first recycled filtrate loop to the first location (3); to obtain the bleached pulp.

主权项

1. A bleaching plant for making bleached pulp, comprising:
(a1) at least one device configured to press or dewater a first unbleached pulp mixture to produce an unbleached pulp mixture and a first filtrate; (a2) at least one device configured to send at least a portion of the first filtrate to a first location (2) of a second recycled filtrate loop; (a3) at least one device configured to contact the unbleached pulp mixture with a first recycled filtrate obtained from a first location (3) of a first recycled filtrate loop and obtain a first pulp mixture having a first consistency; (b) at least one device configured to bleach the first pulp mixture and obtain a first bleached pulp mixture; (c) at least one device configured to press or dewater the first bleached pulp mixture and obtain a first pressed or dewatered bleached pulp mixture and a second filtrate; (d) at least one device configured to send at least a portion of the second filtrate to a second location (5) of the first recycled filtrate loop, wherein the second location (5) is downstream of and in fluid communication with the first location (3); (e) at least one device configured to contact the first pressed or dewatered bleached pulp mixture with a second recycled filtrate obtained from a third location (6) of the first recycled filtrate loop and obtain a second pulp mixture having a second consistency, wherein the second consistency is greater than the first consistency, and wherein the third location (6) is downstream of and in fluid communication with the second location (5); (f) at least one device configured to bleach the second pulp mixture and obtain a second bleached pulp mixture; (g) at least one device configured to press or dewater the second bleached pulp mixture and obtain a second pressed or dewatered bleached pulp mixture and a third filtrate; (h) at least one device configured to send at least a portion of the third filtrate to a fourth location (8) of the first recycled filtrate loop, wherein the fourth location (8) is downstream of and in fluid communication with the third location (6); and (i) at least one device configured to recycle at least a portion of the third filtrate in the first recycled filtrate loop to the first location (3); and obtain a bleached pulp; wherein the second recycled filtrate loop is in fluid communication with the first recycled filtrate loop to either control a fluid level in the first recycled filtrate loop, to dilute a residual bleaching agent level in the first recycled filtrate loop, or a combination thereof.