Use of multisample analytical centrifugation for evaluation of separation of fine particle slurries in the centrifugal field

摘要

Unit processes using centrifugal fields are often applied for separation, deliquoring and classification of fine grained materials. Modelling of these processes requires information about the separation behaviour of the suspensions to be processed. To this end direct measurements in centrifuges are obligatory. Moreover, these measurements have to gather kinetic information as function of the processing conditions, particle interaction and particle concentration. The separation behaviour of quartz (stable dispersions) and limestone suspensions (moderately and strongly flocculated) was investigated as function of solid concentration and centrifugal acceleration using a multisample analytical photocentrifuge. The new multisample approach uses the STEP-technology. Space and time resolved extinction profiles quantify the alteration of particle concentration, the velocity distribution of particles and packing behaviour during centrifugation. Particle interactions are characterized by the packing density determined under defined conditions and by its variations under alternating centrifugal load. Multisample analytical batch centrifugation with optical detection proved to be a versatile tool for the characterization of the separation of fine grained materials. This holds for information on the type of sedimentation behaviour (free sedimentation of individual particles, hindered settling, zone settling) on the sedimentation velocity distribution inside the centrate and on the packing, compression and elasticity behaviour, on the nature of particle interactions and the degree of flocculation as well. The results of multisample analytical centrifugation with optical detection were in good agreement with the results derived by other methods (velocity distribution determined by manometric detection and average packing density obtained during compression in a disc centrifuge).