Bleaching optimization at WestRock mill  in Covington, Virginia, TAPPI JOURNAL September 2016

ABSTRACT: The WestRock mill in Covington, VA, USA, initiated a long term diagnostic and optimization pro-gram for all three of its bleaching lines. Benchmarking studies were used to help identify optimization opportunities. Capital expenditures for mixing improvement, filtrate changes, equipment repair, other equipment changes, and species changes were outside the scope of this work. This focus of this paper is the B line, producing southern hard-wood pulp in a D(EP)DD sequence at 88% GE brightness. The benchmarking study and optimization work identified the following opportunities for improved performance: nonoptimal addition of caustic and hydrogen peroxide to the (EP) stage, carryover of D0 filtrate to the (EP) stage, and carryover of (EP) filtrate to the D₁ stage. As a result of actions the mill undertook to address these opportunities, D0 kappa factor decreased about 5%, sodium hydroxide consump-tion in the (EP) stage decreased about 35%, chlorine dioxide consumption in the D₁ stage decreased about 25%, and overall bleaching cost decreased about 15%.

Application: A long term, sustainable, bleach plant optimization and cost reduction study was performed with minimal to no capital. Mills can apply similar methodologies to their own bleach plants and obtain reasonable results.

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