NON-CHLORINE BLEACHING METHOD OF ARTIFICIAL FIBER CELLULOSE

摘要

PURPOSE: To provide a bleaching method for synthetic fiber cellulose, which reduces environmental pollution and saves energy, by utilizing residual oxygen in the off gas from an ozone bleaching process for oxygen bleaching and waste water from the ozone bleaching process for, e.g. de-ashing of bleached cellulose, to recycle chemicals. CONSTITUTION: This method bleaches synthetic fiber cellulose comprises in three stages, as necessary combined with oxygen, and using hydrogen peroxide, ozone and hydrogen peroxide in this order, wherein residual oxygen in the off gas from an ozone bleaching stage is recycled back to the oxygen bleaching stage to be completely reacted with the cellulose. At the same time, the waste water, preferably kept at pH 3 or less, discharged from the hydrogen peroxide bleaching stage is used for diluting the cellulose stream between the oxygen and ozone bleaching stages, and/or for de-ashing of the bleached cellulose. The oxygen bleaching stage is preferably controlled under the conditions of temperature: 75 deg.C, NaOH concentration: 2.5 to 5 wt.%, based on the bleached cellulose, O2 concentration in the O2 -H2 O2 mixture: 50 to 100%, and H2 O2 concentration: 0 to 50%, in order to match the oxygen consumption with residual oxygen content in the off gas from the ozone bleaching stage at a constant throughput.