Influence of the properties of solid particles added to a structured suspension on its dynamic sedimentation stability

Abstract

The research paper analyzes previous studies of the influence of two natural relatively pure aluminum oxides on rheological properties of structured suspensions. The results of the research show that the content of these materials in the mineral part of coal contributes to a decrease in viscosity inversely proportional to the ash content of coal to a certain fractional degree. The analysis showed that the effect of additions of mineral particles, their size and concentration on the dynamic or static sedimentation stability of structured suspensions has never been studied. The aim of the research paper is to study the effect of additions of mineral particles of polydisperse granulometric composition of different nature on the dynamic sedimentation stability of a structured suspension of high-ash coals. The solution of the problem is carried out by comparison of the forces of attraction and repulsion, which are characterized by an ion-electrostatic and van der Waals nature, with the forces , which arise when a fluid flows around two particles of different density and size, with taking into account the turbulent component and speed deficits proportional to the hydraulic sizes of interacting particles. As a result of the research, the authors developed and specified the hypothesis of the mechanism of aggregative stability of a structured suspension in dynamics. It takes into account the heterogeneity of the properties of particles of the solid phase, which made it possible to establish the value of the average flow velocity in a circular tube, at which the aggregative stability of a structured suspension is disturbed. It is found that the particle size, the nature of the solid material and its mineral inclusions, their surface potential, and rheological characteristics are the main factors, which determine the aggregative stability of structured suspensions. The influence of rheological characteristics of the structured suspension and the radius of the pipeline on the flow velocity, at which its aggregative stability was disturbed, was studied for the case when the solid phase was represented by particles with different density and fineness. In addition, the minimum possible ratio of the Archimedes parameters of the interacting particles, at which the effect of pseudo-homogeneity occurred, was evaluated.