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Controlling thickener underflow rheology using a temperature responsive flocculant
Author(s) -
Franks George V.,
O'Shea JohnPaul,
Forbes Elizaveta
Publication year - 2014
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.14469
Subject(s) - arithmetic underflow , flocculation , rheology , sedimentation , slurry , viscosity , materials science , chemical engineering , tailings , hydrocyclone , chemistry , waste management , sediment , composite material , geology , metallurgy , engineering , mechanics , paleontology , physics , computer science , programming language
Continuous solid–liquid separations with the temperature responsive flocculant poly ( N ‐isopropylacrylamide) (PNIPAM) were conducted in a pilot‐scale thickener for the first time, using fine quartz as the feed slurry. The performance in continuous operation was compared to batch sedimentation. The increase in sediment consolidation on cooling in batch sedimentation was less significant in the continuous operation due to kinetic limitations of the deeper sediment bed and shorter residence times in the pilot‐scale thickener. The reduction in underflow rheology which results when using the temperature responsive polymer as flocculant is significant. Paste‐like behavior results when underflow is discharged at 50°C, whereas low viscosity, near Newtonian behavior results when the underflow is discharged at 20°C. Compared to conventional polyacrylamide‐based flocculants, PNIPAM produces higher concentration underflow but lower clarity overflow and most importantly, significantly reduced underflow rheology (viscosity and yield stress). Temperature responsive flocculants have significant potential to reduce underflow pumping energy and cost for mineral tailings. © 2014 American Institute of Chemical Engineers AIChE J , 60: 2940–2948, 2014