Centrifugation – Key technology for solid/liquid/liquid separation

Dr. Harald Anlauf, Karlsruhe Institute of Technology (KIT) - Germany

Particle/liquid separation can be focused on very different tasks like thickening, purification, fractionation, sorting, extraction or deliquoring. The separation has to be mastered for wide ranges of particle size and shape, specific solid and liquid weight, slurry concentration, chemical composition and rheology, flow rate, process and technical boundary conditions and last but not least demands on the separation results. To solve all the separation problems beside centrifuges many physically different methods and in total more than 2000 different apparatuses and machines are available at present, but always new developments can be observed.

The necessary pressure difference for separation can be generated either by gas, mechanical and hydraulical pressure or by hydrostatic and centrifugal pressure. This causes for cake filtration some fundamental physical differences between pressure filters and filter centrifuges. These physical differences and further aspects have to be considered, when the question has to be answered, whether a pressure filter or a centrifuge may be the better option to solve a specific separation problem. Beside filtration by centrifuges with a perforated bowl centrifuges with a solid bowl are able to realize density separation. Thus both fundamental separation principles can be covered by centrifuges. This enables for centrifuges not only solid/liquid but in addition solid/liquid/liquid or liquid/liquid separations.

Centrifuges can be applied very flexible to solve most different separation problems and beside speed the centrifuge design parameters are decisive to adapt the machine best possible to the specific separation problem. The improvement of the centrifugal technology is a dynamic process and many technical innovations as well as theoretical progress can still be observed. One important issue for centrifuges represents the reduction of the necessary energy demand for the separation process, because the physical principle of using mass forces requires an acceleration of the total slurry mass to the circumferencial speed.

To increase the centrifugal separation efficiency not only the centrifuge itself has to be considered but in addition diverse possibilities of slurry pre-treatment and apparatus combinations. Last but not least beside centrifugal forces gas differential pressure and thermal drying can be implemented in some centrifuges additionally to realize a synergistic hybrid separation concept.

Session: Plenary Lecture
Day: 22 October 2019
Time: 10:45 - 12:00 h

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