Method for bleaching mechanically defibered pulp
OwnerTeemu Tannerinventor
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Abstract
The invention relates to a method for bleaching mechanically defibered pulp with peroxide in alkaline conditions and for washing the bleached pulp and recovering chemicals from the spent liquor the bleaching step by concentrating and combusting the spent liquor and subsequently dissolving the ash thus formed into water. According to the invention, the alkaline conditions of the bleaching step are obtained by adding sodium aluminate to the pulp to be bleached, at least a part of the added sodium aluminate being the ash dissolved in water.
Claims20
A method for bleaching (3) mechanically (2) defibered pulp (14) with peroxide (29) in alkaline conditions and for washing (4) the bleached pulp (15) and recovering chemicals from the spent liquor (16) of the bleaching step by concentrating (5, 8) and combusting (6) the spent liquor and dissolving (7) the ash (31) thus formed into water (13), wherein the alkaline conditions in the bleaching step (3) are obtained by adding alkali metal aluminate (12) to the pulp (14) to be bleached, which alkali metal aluminate at least to a part is said ash (28) dissolved in water.
Dependencies are inferred from the claim text.