Chlorine Dioxide for Processing Mixed Paper Wastes, 1995 Pulping Conference Proceedings

Philip E. Quinnett

Olin Chlor-Alkali Products

L. René Ward

Olin Chlor-Alkali Products

As secondary fiber processing increases, typical waste paper sources are predicted to become lower quality with increasing contamination from “difficult-to-bleach” papers, e.g., highly colored papers, groundwood, or unbleached Kraft. As the complexity of the waste paper furnish increases, processing must become more flexible to respond to potential variations. This paper reviews the results of laboratory “bleaching” tests of different secondary fiber pulp samples from mill, pilot plant, and laboratory. The pulp samples demonstrate a wide variety of pulp quality including high color content, varying lignin content, and varying mechanical fiber content. The results show that solution chlorine dioxide is a powerful “bleaching” agent applicable to a wide variety of pulps. Chlorine dioxide provides multiple functions to processing sequences including decolorization, bleaching(brightening), and delignification. The use of chlorine dioxide with mixed recycled paper allows a high degree of process flexibility and generates low AOX in the process. Chlorine dioxide is a very effective color-removal-agent with potential for 30-point brightness gains in a single, chlorine dioxide stage. For pulps including those with groundwood and Kraft content, results indicate that chlorine dioxide is a very effective initial “bleaching” stage that integrates effectively with hydrosulfite and peroxide brightening. One pilot plant pulp sample reached a 90 + brightness with a DPY process sequence.