SEDIMENTATION AND CONSOLIDATION BEHAVIOUR OF KAOLIN SUSPENSIONS IN PRESENCE OF DISPERSANT

FILTECH 2009 International Conference Exhibition for Filtration and Separation Technology
October 13 - 15 Wiesbaden Germany

Characterization of sedimentation and consolidation behaviour of kaolin suspensions in presence of dispersant

T. Sobisch², C. Le Coeur¹, T. Detloff², A. Zierau², O. Larue¹ .D. Lerche², E. Vorobiev¹

¹ Université de Technologie Compiègne / Département Génie Chimique, Compiègne/France

² LUM / 12489 Berlin / Germany

During processing and application of kaolin usually dispersants are used. For optimization evaluation of the sedimentation behaviour of the suspensions can deliver important information. To this end a method for comprehensive characterization of this process is required.

Space and time resolved photometric methods using near infrared (NIR) light enable the measurement of the movement of the boundary towards the supernatant and to characterize clarification processes. X-rays on the other hand give information on concentration profiles in sediment and suspensions. These two methods complement each other to characterize sedimentation and consolidation behaviour.

In this paper the sedimentation and consolidation behaviour of kaolin suspensions was studied by multisample analytical centrifugation with photometric detection. Kaolin, dispersant concentration and centrifugal acceleration was varied. After dewatering of the sediments in the centrifugal field, the distribution of packing density was determined using X-ray measurements.

LABORATORY SCALE EVALUATION OF INCLINED SETTLING

FILTECH 2009 International Conference Exhibition for Filtration and Separation Technology
October 13 - 15 Wiesbaden Germany

Laboratory scale evaluation of inclined settling

T. Sobisch, D. Lerche, LUM, Berlin/Germany

The principle of inclined settling is often used in practise to increase capacity and efficiency of settling aggregates. The settling rate in inclined-plate (lamella) and tube settlers is influenced by two factors, the effect of gravity acting on the particles and the settling rate due to the presence of inclined surfaces. The increase in settling rate exhibits a complex dependence on material properties (solids density and size distribution, concentration, surface properties, liquid properties) and the angle of inclination. So far adjustment of operating conditions is done empirically or based on pilot or field scale experiments. A preselection based on lab scale experiments would be beneficial.

The LUMiReader instrument can measure space and time resolved extinction (transmission) profiles (STEP technology) in multiple channels using near infrared (NIR) or visible light. This way it measures changes in turbidity and the movement of the boundary towards the supernatant. Even more the angle of inclination can be varied between 0 and 30° from the vertical.

Investigations on settling as function of angel of inclination were carried out on lime suspensions with varying solids concentration.

FLOCCULATED DISPERSIONS CHARACTERIZED BY DIFFERENT METHODS MEASURING TRANSMISSION

FILTECH 2009 International Conference Exhibition for Filtration and Separation Technology
13 - 15 October 13 - 15 Wiesbaden Germany

sedimentation and consolidation behaviour of Flocculated Dispersions Characterized by different methods measuring transmission

T. Sobisch¹, A. Zierau¹, A. Bjeoumikov², M. Holke³, D. Lerche¹

¹ LUM, ² IFG GmbH, ³ IAP e.V., Berlin/Germany

During technical application and during solid-liquid separation dispersions are often flocculated. While during application sedimentation and consolidation usually have to be avoided or minimized, for solid-liquid separation these are essential. In both cases there is a need for fast reliable methods for comprehensive characterization of these processes.

Space and time resolved photometric methods using near infrared (NIR) light are well suited to measure kinetics of sedimentation and clarification. Using X-rays additional information on concentration profiles in sediments and highly concentrated suspensions can be obtained. Therefore photometric and X-ray measurements can ideally complement each other.

Investigations on sedimentation and consolidation behaviour of flocculated polydisperse quartz suspensions are presented. These were carried out at normal earth gravity as function of flocculant concentration using both transmission measurements with NIR light and X-rays. This was followed by measurement of the compressional behaviour of the sediments formed at earth gravity. To this end multisample analytical centrifugation with photometric detection was used. After dewatering of the sediments in the centrifugal field the space resolved distribution of packing density inside the sediments was determined measuring X-ray transmission.

Qualitätskontrolle und Stabilitätsuntersuchungen an Wasserlacken

GDCh - Lacktagung 2009 - Wasserlacke überall
23.-25.09.2009 Überlingen Germany

Qualitätskontrolle und Stabilitätsuntersuchungen an Wasserlacken mittels Analytischer Zentrifugation

Sobisch, T., Uhl, A., Lerche, D., LUM Berlin/D

Wasserlacke sind Dispersionen. Deshalb ist nicht nur die mikrobiologische und chemische, sondern auch die Entmischungsstabilität der Produkte zu prüfen. Diese Aufgabe ergibt sich sowohl in Bezug auf die Entwicklung neuer Produkte als auch für die Qualitätskontrolle.

Es wird eine Multiprobentechnik vorgestellt, die mittels Analytischer Zentrifugation eine beschleunigte Charakterisierung von Entmischungsprozessen (Aufrahmung, Sedimentation, Koaleszenz, Phasenseparation) erlaubt. Hierbei kann die Kinetik dieser Destabilisierungsprozesse direkt zeitgleich für bis zu 12 verschiedene Proben bestimmt werden.

Die Analytische Zentrifugation mißt die den Proben inhärente Stabilität. Erst in der Zukunft ablaufende Destabilisierungsprozesse, die auf langsamen Diffusionsprozessen beruhen, können nicht vorhergesehen werden. In dieser Hinsicht empfiehlt sich eine Kombination mit gängigen Alterungstests. Neben der direkten und indirekten Messung der Dispersionsstabilität kann die Dispersionsstruktur (geflockt/nicht geflockt) und Art der Partikelwechselwirkungen (attraktiv oder repulsiv) sowie die Partikelgrößenverteilung der Produkte charakterisiert werden.

Konzentrationsprofile innerhalb der sich bildenden Sedimente wurden mittels ortsaufgelöster Messung der Röntgentransmission gemessen.

Die Leistungsfähigkeit der Methode wird am Beispiel ausgewählter Wasserlacke insbesondere in Bezug auf pH und Temperatureinfluß belegt.