PRESSURIZED PEROXIDE BLEACHING

摘要

Paper pulp, typically having a consistency of about 8-20%, is mixed with hydrogen peroxide and bleached at superatmospheric pressure (typically about 25-150 psig). When bleaching at superatmospheric pressure, and at a temperature of about 80-140.degree.C (preferably about 90-110.degree.C), brightness comparable to atmospheric bleaching for three hours can be obtained in 45-60 minutes for a given peroxide charge (e.g. 1-4 kg per ton of pulp). Bleaching can take place in a reaction vessel having overpressure provided by a gas, such as substantially pure oxygen, or nitrogen.