TCF Bleaching of Conventional Cooked Softwoods- An Analysis of Oxygen, Peroxide and Ozone Options, 1996 Pulping Conference Proceedings

Debra Breed

Beloit Pulping

Elias Salvador

Jorge L. Colodette

Universidade Federal de Vicosa

The use of TCF bleaching is growing at a rate of approximately one million tons per year. As demand grows the number of options are increasing for mills considering TCF bleaching. The purpose of this study is to examine a series of options available for conventionally cooked Kraft softwood pulps of 25-30 kappa. The focus of this report is on TCF bleaching sequences using oxygen and peroxide and evaluation of the benefits of ozone to the sequence. Three pulps were studied to address: l How different types of peroxide stages fit: P(atmospheric), EOP or PHT (high temperature) l The effect of low ozone doses on pulp quality, final brightness and TCF economics. With a minimal capital investment, and just peroxide, it is possible to approach an 8O%ISO brightness with conventional cooking. To approach higher brightness levels, >88%ISO, requires lowering the kappa number to the bleach plant with extended cooking and oxygen and/ or the addition of ozone.