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Title
A higher brightening of mechanical pulps
Authors
HAO REN and SHIGETOSHI OMORI
Received
September 28, 2011
Published
Volume 46 Issue 1-2 January-February
Keywords
mechanical pulp, alkalinity, hydrogen peroxide, pulp consistency, brightness
Abstract
Enhanced utilization of mechanical pulp is an ideal strategy for countries such as China, whose supply of wood and of other high quality biomass is limited. The objective of this study was to minimize the brightness difference between hydrogen peroxide (H O ) bleached mechanical pulps and bleached chemical pulps. The relationships 2 2 between alkalinity and brightness, alkalinity and H O consumption, H O application and brightness, HO 2 2 2 2 2 2 application and its consumption, maximum brightness versus HO consumption, and extinction coefficient versus 2 2 bleaching time were investigated. The investigation was conducted on Norway spruce (Picea abies) thermomechanical pulp (TMP). A bleached brightness of 81.1% was obtained with H O application of 4.0% on pulp for 3.0 h at 30.6% consistency and 60 °C. 2 2 The optimization of the sodium hydroxide application dose was the key to such a high final brightness. Preliminary results suggest that a higher brightness could be obtained if two-stage bleaching with liquor recycle was used. However, the concentrations of TOC and calcium in the recycled liquor have to be carefully controlled.
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