On-Line Kappa-Bright Analyzer in ECF- and TCF- Bleaching, 1997 Process & Product Quality Conference Proceedings

ECF- and TCF-bleaching pose new challenges to pulp makers: how to produce high quality pulp economically and in an environmentally sound way. Lignin removal has shifted to the brown stock area, and the bleaching process conditions have also changed. This involves opportunities and needs for new, more reliable process measurements. High product quality requires effective process control. Continuous on-line and in-line measurements enable the control to handle process variations with minimum delay. Laboratory measurements lag several hours behind the situation, and that may have crucial effects on the final product. To ensure quality and economy, bleaching process control needs on-line Kappa and brightness measurements. Kappa factor control, based on Kappa measurement, optimizes bleaching chemical consumption, and brightness measurement safeguards good IS0 brightness of the final product. In DO-stage on-line Kappa and brightness measurements, together with in-line sensors, reduce brightness and EO Kappa variations. In Dl-stage, chemical dosage control is based on on-line Kappa measurement, and on-line brightness measurement ensures uniform brightness. In D2-stage, absolute brightness measured before and after the stage optimizes final brightness. In TCF-processes on-line Kappa and brightness are also used for control and monitoring.