Aggregate evolution rule during tailings thickening based on FBRM and PVM

The real-time inline monitoring technologies of focused beam reflectance measurement (FBRM) and particle video microscopy (PVM) were used to analyze the aggregate structure evolution during the operation of a dynamic thickening system. The tailings dewatering studies were performed under two series of conditions: (i) rake rotation speeds of 0, 0.1, 1, and 10 r·min⁻¹ and an initial mud bed height of 75 cm and (ii) initial mud bed heights of 75, 45, and 25 cm and a rake rotation speed of 0.1 r·min⁻¹. The aggregate diameter, particle size distribution, and real-time images of the tailings thickening process were obtained. The results show that with the increase in the shearing time, the diameter and counts of aggregate first increase, then decrease, and then become stable. According to the aggregate diameter variation, the aggregate evolution can be divided into three stages: growth, reconstruction, and densification periods. The condition of a shear rate of 0.1 r·min⁻¹ and an initial mud bed height of 75 cm has the best effects on the aggregate growth, structure breaking acceleration, aggregate reconstruction, and aggregate densification improvement, as determined in the laboratory; however, high shear rate has a degrading effect on the aggregate structure evolution. The aggregate diameter progressively decreases with the increase in the shear rate. The longer the aggregate growth period, the larger the maximum aggregate diameter, and a longer reconstruction period is observed at higher initial mud bed heights. Moreover, the aggregate diameter increases with the increase in the initial mud bed height. The fractal dimension of tailings aggregate reflects the change characteristics of the aggregate structure. According to the calculation of fractal dimension and porosity of the PVM image, the dynamic equilibrium relastionship between the breaking force and cohesive force of aggregates was analyzed, the influence on the aggregate breaking was analyzed. The aggregate densification rule in the tailings thickening process was revealed analyzed, based on the dynamic equilibrium relationship between the breaking force and cohesive force of aggregates.