B3 Unrefereed conference proceedings

Effect of hydrocyclone classification on the filtration characteristics of green liquor dregs


Publication Details
Authors: Golmaei Mohammad, Kinnarinen Teemu, Jernström Eeva, Häkkinen Antti
Publication year: 2018
Language: English
Title of parent publication: FILTECH 2018 - Proceedings
JUFO-Level of this publication: 0
Permanent website address: http://www.filtech.de/
Open Access: Not an Open Access publication

Abstract

Green liquor dregs have the largest share of inorganic solid residues in kraft pulp mills. These solid residues are generated in the chemical recovery cycle in the stage where the smelt from the chemical recovery boiler is dissolved in weak white liquor to produce green liquor. The dregs are separated from the green liquor and disposed of in the landfill after washing and deliquoring. One of the most typically applied separation methods at the purification stage of green liquor is cake filtration. The formation of a highly resistant dreg cake in the filter is a major challenge in industrial scale. A common technique for improving the filterability of green liquor sludge is utilizing a fraction of lime mud generated in the chemical recovery cycle as filter aid in precoat filters. However, this technique increases the amount of contaminated solid residue, which has to be transported to the landfill.

In this study, classification with a narrow-angle hydrocyclone is used as a pretreatment method for the pressure filtration of green liquor sludge without a lime mud precoat. The hydrocyclone is utilized to split the dregs into overflow and underflow fractions according to their size and density. In the hydrocyclone classification stage, the effects of variables such as the underflow diameter size and the inlet pressure on the classification of the dregs are studied. Then the filtration properties of the obtained overflow and underflow samples are compared with the original green liquor sludge by using a laboratory-scale pressure filter. The results show that the finer particles migrate to the overflow, while the coarser particles are collected with the underflow. Similarly, the use of smaller underflow diameter improves the separation efficiency of finer particles. In the pressure filtration tests with the overflow and underflow samples, the filtration characteristics of dregs are affected considerably by their particle size distributions.


Last updated on 2019-22-01 at 10:19