In-Plant Solutions for Decreasing Effluent Conductivity in Bleached Kraft Pulp Mills: Managing Excess CLO₂ Generator Saltcake, 2003 Environmental Conference Proceedings

Over the past few years, bleached kraft pulp mills have increased their use of chlorine dioxide, and at the same time have tightened their brownstock washing and screening systems to decrease losses. This has resulted in a decreased need for make-up sodium and sulfur, and an increase in the production of by-product ClO2 generator saltcake. Often this excess saltcake is simply sewered. While sodium sulfate is chemically inert and not bioactive, in some locations the disposal of excess saltcake to the mill effluent can contribute to conductivity in the receiving waters. Several viable options are available for decreasing saltcake production and/or decreasing effluent conductivity levels by manipulating and better-managing the process streams within the pulp mill – in some cases decreasing operating costs as well – while at the same time maximizing the use of already-capitalized equipment in the bleach and chemical plants. This paper will review these in-plant solutions and examine their impact on pulp mill costs and effluent conductivity levels.