Characterization of Solid-Liquid Separation of Flocculated Mineral Slurries by NIR-Transmission and X-Ray Concentration Profiling

Flocculation is often used in solid-liquid separation processes to ensure removal of fines. Average packing density in sediments and degree of clarification are easily accessible by optical detection with light. For a more comprehensive understanding of separation process and packing behaviour of sediments more detailed information on local particle concentration, i.e. concentration profiles are necessary. To this end measurement of X-ray transmission profiles can be used. The paper presents examples of flocculation of mineral suspensions (quartz, kaolin). Settling and dewatering behaviour at gravity and in centrifugal field as function of acceleration was characterized by STEP-technology measuring light transmission. These measurements were complemented by measurement of X-ray transmission profiles with LUMiReader X-Ray. This enables to determine mean and local packing density as function of flocculant concentration and settling history, i.e. settling time and pressure applied. Thus important information is obtained at lab-scale to optimize solid-liquid separation processes. Results demonstrate clearly that use of NIR and X-ray delivers complementary information. While NIR is highly sensitive for low particle concentrations, X-ray can determine the distribution of packing density inside sediment and generally also concentration gradients in highly concentrated dispersions.