Impurities removal from aqueous fiber suspension, particularly used paper suspension, involves carrying out fractionation for forming fine fraction and crude fraction, where fine fraction floats and crude fraction is dispersed

摘要

Impurity removal involves carrying out fractionation (3) for forming a fine fraction (F) and a crude fraction (G), where the fine fraction floats and the crude fraction is dispersed. A part of the crude fraction after dispersion is treated together with the fine fraction in a selective floatation (1). The fine fraction are loaded with short fibers and the crude fractions are loaded with long fibers during fractionating process.