University of Oulu

Implementation of a novel pigment recovery process for a paper mill

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Author: Jortama, Pirjo1
Organizations: 1University of Oulu, Faculty of Technology, Department of Process and Environmental Engineering
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.4 MB)
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Language: English
Published: 2003
Publish Date: 2003-12-19
Thesis type: Doctoral Dissertation
Defence Note: Academic Dissertation to be presented with the assent of the Faculty of Technology, University of Oulu, for public discussion in Raahensali (Auditorium L10), Linnanmaa, on December 19th, 2003, at 12 noon.
Reviewer: Professor Kari Edelmann
Professor Juha Kallas


The objective of this study is to demonstrate an ecological and economic recovery process, which was developed and implemented at Stora Enso Oyj Fine Paper Oulu mill during the period 2000 to 2002. The ECO plant recovers the material called ECO pigment from the effluent treatment sludge and it can be used as a filler in multicoated fine paper production for art printing purposes.

The ECO plant process consists of the following process stages. First, there is a separating phase for the recoverable material from fibres and other rejects, which is done with a wire washer. Then the fractionating of the recoverable material is performed with two-stage centrifugal cleaners. Chemical treatment with peracetic acid is used as a preservative and to increase the brightness of the ECO pigment a little. Then the recoverable material is stored in the pigment storage area and dosed to the paper machines as a filler. The rejects from the ECO plant are thickened in belt filter presses and then transferred to the bark storage area, where they are mixed with bark and combusted in a solid fuel boiler.

The majority of the particles of the recovered ECO pigment were less than 45 μm; this size of particle accounted for 96.4% (on average) according to the studies made between June and December 2002.

The use of ECO pigment is not found to cause more web defect problems on the base paper than before, according to the studies of the number of total web defects with the achieved particle size distribution and because the microbe content has been controlled.

There are three sources from which the ash content of the base paper is composed after the start-up of the ECO plant, i.e. the broke, the virgin filler and ECO pigment. Therefore the use of ECO pigment partly decreases the need to use virgin filler. The ECO pigment was tested in the coating colour in pilot tests, and based on these results it could be used in the coating colour. The dry solid content of the ECO pigment has to be increased from the present level for the coating application.

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Series: Acta Universitatis Ouluensis. C, Technica
ISSN-E: 1796-2226
ISBN: 951-42-7222-6
ISBN Print: 951-42-7221-8
Issue: 194
Copyright information: © University of Oulu, 2003. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.