D/Z or Z/D a Large Step Toward Cost Reduction, 1996 International Pulp Bleaching Conference Proceedings

The Pulp and Paper Industry has undergone considerable change in recent years resulting in significant modifications in the way in which products are made and sold to the consumer. Current trends within the industry include suc-cessful efforts to reduce the impact of the entire process on the environment as well as efforts to better utilize the wood raw materials entering the process. The trend to reduce the impact of the pulping and papermaking process on the environment has thus far focused on the bleach plant operations. The industry has initiated changes in this process in order to maintain global competitiveness and to meet worldwide market and regulatory demands. The results of these efforts in the United States have included the minimization and in many cases elimination of the use of molecular chlorine and the reduction in the lignin content of pulp prior to the bleach plant. This last effect has been achieved through extended delignification in the digester, improving the selectivity of the pulping process through chemical profiling, and oxygen delignification. All of the changes have impacted on the yield of chemical wood pulps from an ever shrinking fibre supply.