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Thursday, August 13, 2009
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.
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 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.
ACHEMA2009 - Paint products: Accelerated stability and quality testing by direct measurement of separation and segregation
Paper at
ACHEMA 2009 29th International Exhibition-Congress on Chemical Engineering, Environmental Protection and Biotechnology 11 - 15 May 2009 Frankfurt am Main / Germany
Paint products: Accelerated stability and quality testing by direct measurement of separation and segregation
To assure continued consumer satisfaction the following stability issues of paint products have to be minimized or avoided:
• Syneresis – separation of the liquid dispersion media • Pigment segregation – change of colour composition inside a container • Particle segregation – change of particle size distribution inside a container
These stability issues have to be addressed not only during development of new paint products but also for quality assurance during production on a regular basis. This paper demonstrates that multisample analytical centrifugation can be used as an efficient tool for the accelerated evaluation of separation stability of paint products. In addition this technique provides for high resolution data of particle size distributions of pigments or emulsions.
ACHEMA2009 - Photometric instrumentation for evaluation of dispersion stability and optimization
Paper at
ACHEMA 2009 29th International Exhibition-Congress on Chemical Engineering, Environmental Protection and Biotechnology 11 - 15 May 2009 Frankfurt am Main / Germany
T. Sobisch, T. Detloff, U. Rietz, D. Lerche, LUM Berlin/Germany
Paper 7404, 05/14/09 2 p.m.
Photometric instrumentation for evaluation of dispersion stability and optimization of separation and stabilization of dispersions
Dispersion stability – in one way or the other - is a hot topic in many industries (cosmetics, ceramics, pharmaceutics, paints, mining etc.). Mostly high dispersion stability is required, however, separation of dispersions is the issue in other fields. From this it is evident that formulation of products as well as process and quality control is in need of efficient measurement techniques. The paper proposes the use of high resolution photometric detection of transmission profiles (LUMiReader) and the use of bottom focussed backscattering (LUMiCheck). These techniques allow for an accelerated study of dispersion demixing. The LUMiReader provides information on the extent of phase separation but also on the kinetics of the underlying processes directly in-situ. The LUMiCheck is used to measure sedimentation and creaming with high sensitivity by focussing on changes in particle concentration right at the bottom part of the dispersions. The potential of these methods was demonstrated on several systems by screening for the most efficient dispersants, preparation conditions and also for selection of conditions to separate dispersions.
ACHEMA2009 - Speeding up the evaluation of the physical stability of beverage dispersions
Paper at
ACHEMA 2009 29th International Exhibition-Congress on Chemical Engineering, Environmental Protection and Biotechnology 11 - 15 May 2009 Frankfurt am Main / Germany
Speeding up the evaluation of the physical stability of beverage dispersions
Reduction of turbidity and phase separation is an important problem for the beverage industry. Traditional methods of stability evaluation are visual observations (over several months) and measurement of opacity, droplet size index particle size analysis during storage. Alternatively high resolution photometric detection of transmission profiles with a LUMiReader instrument is proposed. This technique allows for an accelerated study of beverage demixing by providing information on the extent of phase separation but also on the kinetics of the underlying processes directly in-situ. This is of great practical importance for evaluation of shelf life but is also very useful in screening of additives for more stable formulations. The method was tested for a range of beverages with the focus on beverage emulsions.
