Optimization of wash water usage in brown stock washing, 2010 TAPPI PEERS Conference

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The aim of the study was to determine the optimum wash water usage level, at which washing losses are satisfactory, by utilizing 12 separate real-time refractometer measurements and advanced process data analysis tools. Refractometers are able to measure total dissolved solids (TDS) with high reliability.

These results were analyzed with the WEDGE™ tool to calculate various parameters of washing performance. WEDGE™ is a software tool designed for the management of process data and the analysis of process fluctuations. All tests were performed on a mill scale brown stock washing operation at a Finnish pulp mill. The results indicated that TDS changes in the incoming flows (liquid and pulp suspension) to the washer can be detected immediately and reliably by using refractometer measurements. TDS changes also had a clear effect on washing loss in the brown stock line’s oxygen delignification performance. Real-time measurement enables high level control of the washing line and instant information also allows the possibility to control the amount of fresh water to the washer. By proper control of such a system water usage can be optimized and thus excess wash water usage can be reduced.

In conclusion, by utilizing refractometers and data-analysis tools it is possible to discover the black spots of the washing line and evaluate the washing result continuously making it possible to improve washing efficiency and reduce water consumption.