Influence of Process Parameters on the Tapping Characteristics of High Shear Mixer Agglomerates Made with Ultra-High Viscosity Binders

Abstract

Agglomeration by high-shear mixing of linear alkylbenzene sulphonate (LAS) paste and zeolite powder is investigated in terms of the initial temperature of the paste (and hence its apparent viscosity), impeller speed and volume ratio of paste to powder. Variations in these parameters chiefly affect the rate of development of the different regimes in the agglomeration process. The regimes are quantitatively described by the bulk granular aerated and tapped densities, which are determined using an automated tapping technique. The bulk tapping data are analysed using the Kawakita equation and a logarithmic compaction approach. A number of bulk compaction parameters (including the Hausner ratio) are obtained, and their variation with mixing time is discussed. Comparison of the tapping parameters, along with optical micrographs and granule size distribution data, confirmed that similar agglomeration mechanisms are occurring for each system studied. The agglomeration process features two main mechanisms, namely binder distribution followed by granule consolidation and coalescence. The results indicate that it is possible to assign scaling factors to predict the mixing time required to obtain a designated regime. The scaling factors employed for the variation in paste apparent viscosity, impeller speed and paste amount are explained physically in terms of power law functions, Froude numbers and adsorption/ viscous energy dissipation mechanisms respectively.