Attrition Kinetics and Mechanism of Potassium Sulfate Crystals in Stirred Supersaturated Solutions: Experimental Investigation and Quantitative Modeling

Abstract

Potassium sulfate (K₂SO₄) is a critical industrial raw material with extensive applications in high-efficiency agriculture, fine chemicals, and pharmaceutical manufacturing. The mechanical integrity of K₂SO₄ crystals directly determines product quality, process yield, and downstream processing performance. However, crystal attrition during stirred crystallization remains a major bottleneck limiting industrial production efficiency, with systematic studies on its kinetics and underlying mechanisms remaining scarce. This work presents a comprehensive investigation into the attrition behavior of K₂SO₄ crystals in supersaturated solutions under controlled hydrodynamic conditions. A series of batch experiments were conducted to quantify the effects of stirring rate (200–400 rpm) and residence time (20–50 min) on crystal breakage characteristics. A semi-empirical attrition rate correlation was developed based on indentation fracture theory, incorporating key material properties and hydrodynamic parameters. The results reveal that crystal attrition degree increases monotonically with stirring rate, while exhibiting a non-monotonic “rise-then-decline” trend with residence time, attributed to the dynamic equilibrium between surface abrasion and crystal regrowth. The proposed model demonstrates excellent predictive performance with a relative average deviation of 11.86% between experimental and calculated values. Furthermore, the crystal attrition propensity was quantitatively evaluated, showing a strong positive correlation with particle size and stirring intensity. These findings provide fundamental insights into the attrition mechanism of inorganic salt crystals and offer quantitative guidelines for optimizing industrial crystallization processes to minimize product degradation and enhance particle size uniformity.