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Control model for compressible cake filtration of green liquor in cassette filter
KTH, School of Electrical Engineering (EES), Automatic Control.
2006 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In the closed chemical recovery cycle in the sulphate pulp mill it is important to remove non-process elements. This is done by clarification of the green liquor, either in clarifiers or in filters. This project focuses on a cassette filter developed by Kvaerner Pulping AB. The cassette filter is semi-continuous and the aim of the project was to model the filter in order to be able to control cycle time and feed towards optimization of the capacity. The green liquor sludge forms a compressible filter cake when filtered.

The model was built on the filter equation for compressible cake filtration and parameters such as filter cloth resistance, compressibility index and specific resistance in the cake were to be determined. The parameters were calculated by minimizing the difference between the calculated model and the measured data. Some simulation experiments were done to examine if optimization was possible.

It turned out that the two parameters describing the green liquor (specific resistance in the cake and compressibility) were not identifiable from each other and the third parameter (resistance in the filter cloth) was also sometimes unidentifiable. The simulation experiments showed that the capacity of the cassette filter is hard to optimize during unfavourable conditions controlling only cycle time and feed. Proper actions might be to add lime mud or aluminium to increase the filterability of the green liquor sludge or to wash the filter socks to decrease the resistance in the filter cloths.

Place, publisher, year, edition, pages
2006. , 32 p.
National Category
Control Engineering
URN: urn:nbn:se:kth:diva-107502OAI: diva2:576310
Subject / course
Automatic Control
Educational program
Master of Science in Engineering
Available from: 2012-12-13 Created: 2012-12-12 Last updated: 2012-12-13Bibliographically approved

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