Browsing by Author "Halim, CE"

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    Characterisation of dense gypsum slude from waste acid
    (Institution of Chemical Engineers in Australia, 2001-09-23) Halim, CE; Bickert, G; Amal, R
    The treatment of acid waste liquors is often carried out in a conventional neutralisation circuit using lime as reagent. The High Density Sludge (HDS) process improves this technology by recycling conditioned thickener underflow to modify the precipitate particle formation, leading to an increase in the density of the settled solids. The treatment of sulphuric acid was examined using conventional lime treatment and the HDS process, in both batch and continuous mode. The HDS process produced sludge of significantly higher density than the conventional process. Particle size analysis of the solids indicated some variation between conventional and HDS solids. Particle chord length distribution and SEM examination indicated no change in particle shape. Both precipitates exhibited a flat leaf type shape. There was little difference between the conventional and HDS solids from XRD analysis, which indicated a gypsum (CaSO4.2H2O) crystal form. The results suggest that for gypsum, the HDS process alters the particle structure by removing free water molecules, giving a more compact sludge of higher density. This seems to be partially achieved by shearing of the gypsum particles in the conditioning tank, causing compaction of the gypsum sludge. © The Authors.