Optimization of physicochemical process for pre-treatment of fine suspension by flocculation prior to dewatering

Abstract

In the design of process reactors, it is often necessary to tailor the separation technique to the dynamics and characteristics of the working slurry. This study reports the results of physicochemical optimization tests conducted on a model system prior to its pre-treatment in a Taylor-Couette device. The assessment of the flocculation performance was carried out on the basis of surrogate indicators such as sludge volume index ISV and supernatant turbidity; which were chosen on the strength of a preliminary investigation and the particular solid–liquid separation method employed in this study. The results of this investigation showed that the lowest sludge volume index ISV of 4.2 and residual turbidity of 7.27 NTU were obtained at the optimum polymer dose of 2 kg/t TS in single conditioning and 4 kg/t in dual additions. Theoretical charge neutralization of 48.4, 37.8, and 49.1% for the single conditioning and 32.1, 25.1, and 32.6% for the dual additions were recorded at the optimum conditions. The optimum dosage values confirmed polymer bridging as the primary flocculation mechanism. The analysis provides information on the slurry polymer dose response and will serve as a guide for polymer selection and subsequent performance optimization of the pre-treatment devices under development.