Method for bleaching pulp with ozone
AssigneeMyrens Verksted A/S
InventorBjorn H. Fritzvold
Life of this patent
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Abstract
In a reactor plant for treating finely divided bulk material an acid bulk material or pulp having a solids content of approximately 35-50% is conveyed to a combined high-consistency ozonizer and maturation reactor as a substantially vertical pulp column forming a gas blocking means. In the transition area between the ozonizer and the maturation reactor the finely divided and ozonized pulp which has a very acid pH-value is mixed with chemicals to a pH-value of approximately 8-11 and to a solids content of approximately 15-20%, at which solids content the alkaline pulp in the form of a continuously advancing column is subjected to a maturation process which terminates at a pH-value of the pulp of 6-7.
Claims11
A method of treating finely divided fibrous pulp comprising the sequential steps of the continuous flow process of:
- (a) supplying a finely divided fibrous pulp having a solids content of from about 35 to about 50 percent and a pH of about 5;
- (b) treating the pulp with ozone until its pH decreases to from about 2 to 4 while maintaining its solids content;
- (c) alkalizing the pulp by mixing it with alkali until the pH is temporarily increased to from about 8 to 12 and the solids content is reduced to from about 15 to about 30 percent;
- and
- (d) permitting the pulp to mature by diffusion, and without further mixing, until it reaches a stable pH of from about 6 to 7, the solid content of from about 15 to about 30 percent remaining unchanged.
Dependencies are inferred from the claim text.