Feasibility of separation processes in liquid‐liquid solid systems: Free energy and stability analysis

Abstract

The feasibility of new solid/liquid separation processes, such as solids removal from oil and certain tertiary oil recovery techniques, can be evaluated by a thermodynamic stability analysis of possible liquid-liquid-particle configurations. The thermodynamic stability and hence feasibility of two possible liquid-liquid-particle separation process is predicted by use of a free energy analysis. Stability is shown to depend primarily on droplet/particle size ratio (n) and three phase contact angle (0). Stability criteria are presented which can be applied to many particle and liquid separation processes. The stability of liquid-liquid-particle systems is of considerable concern in many chemical and energy process applications. Several solids separation processes, for example, rely on the distribution of suspended particles from a bulk liquid phase into a second immiscible liquid phase which is then subsequently separated from the bulk phase prior to removal of the particulates. Examples of such applications include particle removal from oil continuous media using an aqueous solution as the second immiscible liquid and selective removal of cell particles and macromolecules from body fluids by use of a second immiscible liquid. MALCOLM T. JACQUESOther separation processes utilize a second immiscible liquid to form a bridge between suspended particles resulting in particle agglomeration prior to removal of the solids. Examples of this type of separation process are found in tar sand treatment to remove suspended solids. Selective agglomeration and fractionation techniques are also used for the beneficiation of low grade coals and ores.An increasingly important process area in which the interactions between two immiscible liquids and solid particles play an important role is in the removal oE a liquid phase from the interstices of a densely packed particle matrix. Several tertiary oil recovery techniques, such as surfactant or micellar flooding, utilize a bulk aqueous phase to remove the immiscible oil phase from the interstices of the oil bearing strata.Despite the widespread application and growing demand of new energy based processes for liquid-liquidparticle separations, there is surprisingly little fundamental information available on the mechanisms and parameters which govern such systems. Consequently, a systematic evaluation of possible liquid-liquid-particle separation techniques for new process applications cannot be accomplished without expensive and time consuming trial and error experimentation.This paper attempts to partially redress these shortcomings and presents a general thermodynamic surface-energy analysis, the results of which are used to infer the relative of interest in-separation-process applications. The free energy of an initial equilibrium state consisting of single discrete spherical particles and immiscible liquid droplets dispersed in a bulk liquid phase is evaluated in terms of dispersed droplet/particle size ratio (n), three phase contact angle (e), and liquid-liquid surface tension (7%)...

Long-range attractive interaction between macroparticles in a binary fluid mixture

“…In example 2h M2 (0) is more divergent thanh M1 (0). The variation of u MM (r ) / (k B T ) with increasing x 2 is illustrated in ® gure 9. As x 2 increases, the interaction between macroparticles shifts in a more attractive direction and becomes longer range.…”

Modelling of Binder-Induced Agglomeration

“…The volume of the bridge is calculated by integrating the equation of the meniscus line C 1 C 2 around the x-axis and subtracting the volumes of the segments of the spheres [3]. This is a relatively trivial task when the bridge adopts the geometry of a toroid (the usual theoretical assumption) but becomes significantly more challenging for non-constant curvature meniscus geometries.…”

Development and scale-up of particle agglomeration processes for coal beneficiation

“…14, the agglomerate diameter was mainly in the range of 0.2 to 0.3 mm, while for runs MS 64, 72 and 80, which produced the results shown inFig. 5.15, the agglomerate diameter was mainly in the range of 0.05 to 0.12 mm.…”

“…Jacques et al [14] found that the stability of particle attachment to immiscible liquid droplets (oil droplets) in a bulk liquid phase (water) can be explained by the change in free energy. The most stable state was shown to be reached when the three phase contact angle (0) approaches 0°, and the dispersed liquid droplet over particle size ratio (n) approaches infinity.…”