How to use total dissolved solids measurements to evaluate the performance of diffuser washers—A mill study, TAPPI Journal April 2020

Application: Diffusers washers are still very common washers at pulp mills in the United States. With the monitoring and control of diffuser washers’ performance using the latest measurement technology, it is possible to achieve economic savings at mills. From this study, readers can learn the importance of control and monitoring of washing and the importance of accurate in-line measurements. They can also learn some new information about the reaction from different adjustments. We think this information could be beneficial for Research and Development engineers and also production personnel.

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Author: Riku Kopra, Anna Pesonen, Jari, Käyhkö, and Olli Dahl
How to use total dissolved solids measurements to evaluate t
ABSTRACT: Various types of pulp washing equipment are available. Each washing device has a unique mechanical construction, and the washing principle is often a combination of dilution, thickening, and displacement washing. In this work, the performance of the pressure diffuser washer is studied. In stepwise trials, the effect of the feed and discharge consistencies on the performance of the diffuser was studied. The effect of the downward velocity of the screen on the pressure diffuser’s washing efficiency was also studied. The measurement of total dissolved solids (TDS) by a process refractometer was used as a wash loss measurement unit and the refractometer’s results were used in the calculations of standardized Nordén efficiency (E10) values. The chemical oxygen demand (COD) and conductivity values were also measured and their results compared to the TDS results.The results indicated that feed consistency has a significant effect on the performance and effectiveness of the diffuser washers in the mill. It can also be stated that when the downward velocity of the screen is adjusted to too high a level, the washing efficiency of the pressure diffuser decreases. As a conclusion from the mill tests, it can be stated that even small process parameter changes can provide enhanced diffuser washing at the beginning of the washing line, which has a direct effect on the performance of post-oxygen washing.

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