Solid-Liquid Separation in Bio-Suspension Systems with Compressible Solids and Non-Newtonian / Viscoelastic Fluids Containing Colloidally Dispersed Macromolecules

摘要

Bio-materials are in general compressible due to a structural break down under actingnormal and shear forces but also due to gas / air fractions which are entrapped. In solid liquidseparation of suspension systems containing solid particles with such properties using pressureand/or centrifugal filtration techniques the filter-cake permeability is pressure and time dependent.At the same time most of the continuous fluid phases in bio-suspensions contain solved orcolloidally dispersed macromolecules which generate non-Newtonian rheological properties likeshear-thinning and viscoelasticity.Filtrate flow through compressible filter cakes consisting of bio material particles was carried out inpressure and / or centrifugal fields like applicable in hyperbaric centrifugation processing(superposition of static pressure and centrifugal fields). The filtration process - filter cake structure -filtrate rheology - relationships are described from a theoretical and experimental point of view. Forfilter cake structure and non-Newtonian filtrate rheology analytics, methods were developed whichallow to transfer the measured material data for the interpretation of processing experiments.As shown in detail, the influence of filter cake compressibility and non-Newtonian filtrate flowbehavior leads to material related optima in filter cake permeability and mass flow rate at specificstatic pressure and /or C-value in filtration / centrifugation processing. The developedanalytical/experimental methodology provides a basis for pre-calculation of processing optima forfiltration processing for complex bio-suspension systems.In the case of dispersed macromolecules in the filtrate its flow behavior in the pore system of thefilter cake can additionally depend on the impact of flow forces on the macromolecular structure. Ifcritical shear or elongation stresses or related deformations are exceeded, colloidally dispersedmacromolecules can change their structure, thus supporting aggregation. This has a strong impacton the flow through the filter cake but can also influence functional properties of the filtrate.Using dynamic light scattering analysis structural changes of macromolecules in bio-suspensionsystems were monitored and related to changes in the flow behavior through packed particle bedsduring filtration processing.