IN-PLANT SOLUTIONS FOR DECREASING EFFLUENT CONDUCTIVITY IN BLEACHED KRAFT PULP MILLS: MANAGING EXCESS CLO2 GENERATOR SALTCAKE

摘要

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