Abstract

The major objective of this study was the design, construction and testing of a laboratory scale paste thickener. This unit has a modular construction and can be operated on a totally batch mode or as a fully continuous thickener. The thickener was constructed in Plexiglas in order to allow the direct observation of the slurry behaviour inside the equipment. It has two modules reaching a maximum height of 1.2 m with 10 cm of internal diameter. It still makes use of a system for taking samples with orifices of 1cm of internal diameter and equally spaced in the vertical axes by 9 cm. The mineral pastes produced by the equipment were characterised for their rheological properties by means the determination of: viscosity (viscometry), consistency (slump test), fluidity (flume test) and yield stress measurements. The best result without the addition of flocculant in the tests, with the recirculation of the pulp and a residence time of 10 min, was reached when the slurry was taken from orifice number 3 to orifice 1. The paste reached 55.6% of solids by weight under this testing condition. Considering the addition of flocculants the best result was achieved with recirculation of the slurry from orifice number 4 to orifice number 1. This paste reached 53% of solids by weight. Employing two modules of the thickener, the final paste with recirculation reached 56.7% of solids by weight.