Influence of Particle Properties on Filter Cake Compaction Behavior under Oscillatory Shear

Abstract

Filter cake compaction is a common method for mechanical deliquoring of compressible filter cakes. In addition to the conventional squeezing compaction method, applying oscillatory shear to filter cakes at low pressure is an alternative compaction process in cake filtration. While basic differences in terms of compaction success have already been identified for various materials, a systematic analysis of the influence of material properties on compaction behavior under oscillatory shear is missing. The present work addresses the influence of particle size distribution and increasing particle agglomeration on the compaction success of oscillatory shear to further clarify the process knowledge and applicability. The compressibility achieved by this technique was investigated for calcium carbonate materials with various particle size distributions. The results show that the compaction potential increases from 17.3% for the coarsest material (x50,3 = 23.5 μm) to 26.6% for the finest material (x50,3 = 2.3 μm) with decreasing mean particle size. The more widely distributed material exhibits a higher compaction potential of 21.7% compared to 18.4% for the narrowly distributed material. Increasing particle agglomeration to improve the slurry filterability does not affect the achievable compaction states of the material by vibration compaction at sufficiently high energy input.

Mechanical Dewatering of Homogeneous and Segregated Filter Cakes by Vibration Compaction

“…Due to the widely distributed particle size, this material tends to show particle segregation during cake formation for small solid volume fractions of the slurry. Following Yildiz et al [36], who reported correlations between the mean particle size and particle size distribution width of ground calcium carbonates and the vibration compaction behavior, the material is expected to be compressible by oscillatory shear. For these reasons, the choice of this material as a model particle material for this study was justified.…”

“…The cake residual moisture dropped rapidly until the vibration application no longer removed any more liquid from the cake after a few number of oscillations n, and a stationary equilibrium value was reached. The model in Equation ( 6), already used by Illies et al [30,31] and Yildiz et al [36] to describe the exponential kinetics of vibration compaction, provides the minimum achievable residual moisture RM ∞ at a certain frequency in the compaction equilibrium by approximating the experimental data. Other fitting parameters include the consolidation potential B and the compaction rate ϑ.…”

“…Thus, tests were carried out with a compression-permeability cell (CP cell) to compare vibration compaction with compaction by squeezing. Compaction and deliquoring results obtained by squeezing have only been compared with the results of vibration compaction during the load so far [30,31,33,36]. As the compressive pressure is obviously removed from the cake after a certain period on industrial belt filters, this time, the compaction was examined after squeezing, taking the elastic recovery effects of the cake into account.…”