Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
200 words
In a pulp mill bleaching process wherein a pulp slurry is subjected to at least a first chlorination treatment followed by at least a first caustic extraction treatment, each said treatment being followed by a washing and filtration stage, the improvement which comprises reusing a portion of the first caustic extraction stage filtrate for direct countercurrent washing to increase the concentration of the filtrate, removing the balance of said filtrate as a concentrated caustic extraction effluent having a pH of about 9 to 12 and a volume of less than 2,000 gallons per air dried ton of bleached pulp, and combining said concentrated caustic extraction effluent with a concentrated chlorination effluent obtained by recycling the chlorination stage washer filtrate until the pH is less than 1.5, said effluents being combined in a ratio of at least one part by volume of concentrated caustic extraction effluent per part by volume of chlorination effluent and being combined prior to any lime treatment to form a combined effluent having a volume of less than about 2500 gallons per air dried ton of bleached pulp and a pH below about 2.8, to form a precipitate which removes organic color bodies from the combined effluent.
Claim 2
Dependent Claim
200 words
In a pulp mill bleaching process wherein a pulp slurry is subjected to at least a first chlorination treatment followed by at least a first caustic extraction treatment, each said treatment being followed by a washing and filtration stage, the improvement which comprises reusing a portion of the first caustic extraction stage filtrate for direct countercurrent washing to increase the concentration of the filtrate, removing the balance of said filtrate as a concentrated caustic extraction effluent having a pH of about 9 to 12 and a volume of less than 2,000 gallons per air dried ton of bleached pulp, and combining said concentrated caustic extraction effluent with a concentrated chlorination effluent obtained by recycling the chlorination stage washer filtrate until the pH is less than 1.5, said effluents being combined in a ratio of at least one part by volume of concentrated caustic extraction effluent per part by volume of chlorination effluent and being combined prior to any lime treatment to form a combined effluent having a volume of less than about 2500 gallons per air dried ton of bleached pulp and a pH below about 2.8, to form a precipitate which removes organic color bodies from the combined effluent.
Claim 3
Dependent Claim
19 words
A process according to claim 1 wherein the combined effluent has a volume of less than about 2000 gallons/ADBT.
Claim 4
Dependent Claim
17 words
A process according to claim 1 wherein the combined effluent has a volume of about 1500-1700 gallons/ADBT.
Claim 5
Dependent Claim
29 words
A method according to claim 1 wherein the concentrated chlorination effluent has a pH of about 1 and the concentrated caustic extraction effluent has a pH of about 10-11.
Claim 6
Dependent Claim
21 words
A method according to claim 1 wherein the combined effluent, after removal of precipitate, is further processed for additional color removal.
Claim 7
Dependent Claim
27 words
A method according to claim 5 wherein the additional color is removed by contacting the effluent with 2 to 8 g/l lime to precipitate additional color material.
Claim 8
Dependent Claim
33 words
A method according to claim 6 wherein the effluent, after lime precipitation, is contacted with a CO 2 -containing gas to precipitate out residual lime and adjust the effluent pH to about neutral.
Claim 9
Dependent Claim
21 words
A process according to claim 1 wherein additional mineral acid is added to lower the combined effluent pH to below 2.8.