Method for treating process water in connection with pulp bleaching
AssigneeKemira Kemi AB
InventorsChristos Rampotas, Viveka Svensson, Jonny Hansson, Margareta Nilsson
Life of this patent
Estimating the term…
Abstract
A method treats process water containing metal ions, in connection with bleaching of lignocellulosic pulp. The method is characterized by the steps of a) adjusting the Mg2+ content of the process water to form a flocculating base for metals and an organic substance; b) supplying a carbonate source to the process water to precipiate calcium as calcium carbonate; c) increasing the pH of the process water by adding white liquor to precipipate metals such as metal hydroxides; d) adding a flocculating agent to the process water; and e) separating the precipitated, flocculated metal compounds from the process water by flotation.
Claims11
A method for treating process water containing metal ions, in connection with bleaching of lignocellulosic pulp, comprising the sequential steps of:
- a) adjusting the Mg2+ content of the process water to form a flocculation base for metals and an organic substance by adding Mg2+,
- b) supplying a carbonate source to the process water to precipitate calcium as calcium carbonate,
- c) increasing the pH of the process water by adding white liquor to precipitate metals,
- d) adding a flocculant to the process water, and
- e) separating the precipitated, flocculated metal compounds from the process water by flotation.
Dependencies are inferred from the claim text.