BLEACH LOAD: A NEW INLINE SENSOR BASED IMPROVEMENT FOR BLEACH PLANT ADVANCED CONTROL, 2012 TAPPI PEERS Conference

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Minimizing the chemical usage for the delignification and brightening of pulp in a bleach plant requires an automated control strategy that uses accurate, reliable, and timely measurements. Today's advanced control strategies can make minute-by-minute optimization moves, yet their effectiveness is limited by stale measurement signals provided by intermittent lab analyses and sampling, asynchronous analyzers. A new continuous inline measure of the total lignin load to the bleach plant has been developed. This inline reflective sensor uses the same UV light that sampling analyzers use to measure both the fiber lignin and the "wet" or dissolved lignin, as kappa. This combination creates a new value called the "total bleach load," which is used to calibrate the sensor called the Bleach Load Transmitter (BLT). The BLT provides a cost-effective, low-maintenance alternative to sampling analyzer systems. No transport or washing of the sample is required as the measurement is in situ to the process and continuous. The BLT sensor has been implemented in bleach plant control strategies using Profit Controller®, Honeywell's multivariable model-based predictive control (MPC) product. Chemical cost data is used directly by the controller to optimize the spread of the bleaching load.

This paper will describe the installation requirements and performance experience from several mill applications, highlighting the chemical savings achieved when combined with MPC.