Plural stage mixing and thickening oxygen reacting

Abstract From the Canadian patent

A method and apparatus for the treatment of fiber material by oxygen bleaching. Digested cellulosic fiber material is treated with oxygen to reduce the Kappa number thereof further to about 15 or below. The reaction products are removed immediately after formation and during the oxy-, gen bleaching process. The fiber material is at a first consistency of about 8 to 15% consistency and treatment, with oxygen is accomplished by mixing the pulp with O2 NaOH, solution, and water to thereby form an integral mixture of pulp with oxygen at a second consistency thickening the, integral mixture to return it to generally its first consistency, and repeating the mixing and thickening until pulp of a …