| 摘要 |
Treating process water contg. metal ions washed out from pulp of lignocellulose contg. material, prior to bleaching of the pulp with hydroperoxide or ozone, comprises contacting the process water with pulp not intended to be bleached by hydroperoxide or ozone at a pH above 7 at 50-120 deg. C whereby the metal ion content is partially or entirely removed from the process water. - Pref. the process water is brought into contact with pulp at pH 11.0-12.0. The process water is waste water from the washing of pulp after treatment with complex former. The metal ions are sepd. at the washing of the pulp prior to bleaching with hydroperoxide or ozone and are returned entirely or partially to at least a partial flow of the pulp after the bleaching. The pulp used for the sepn. consists of bleached pulp, unbleached pulp or reject pulp. |
