Application of the dynamic flow sheet simulation concept to the solid-liquid separation: Separation of stabilized slurries in continuous centrifuges

- Transient calculation of the clarification process in decanter centrifuges.
- Fast simulation tool for application in flow sheet simulators.
- Process simulation tool for continuous centrifuges in the lab-scale.
- Changes in sediment solids concentration cannot be calculated.

In recent years, the concept of flow sheet simulation of fluid processes has been extended to the dynamic performance of solids handling by considering the particle size distribution as one relevant material property. Continuous centrifugation is widely used throughout the process industry and applied to separate finely dispersed particles from a liquid phase. Current process simulation tools for calculation of separation in decanter centrifuges are limited to steady-state conditions and are currently not applicable for real time simulations. This work illustrates the basic framework of a new dynamic flow sheet approach to predict the clarification process of stabilized particles in decanter centrifuges. The solids residence time distribution describes the transient behavior of a lab decanter centrifuge. This allows the simulation of the complex process behavior with small numerical effort. In the presented approach, the number of related compartments is one key parameter. It could be shown that the concept is suitable for real time simulations of decanter centrifuges. The presented numerical algorithm is capable of real time simulations and model-based process control of a lab decanter centrifuge. This is guaranteed by connecting the solids residence time distribution with the properties of the material for the sedimentation and sediment build-up. The accuracy of the new approach is shown by comparing numerical simulations with experimental results. The presented model is unsuitable to predict the sediment solids concentration of a material which forms a compressible cake. An extension of the basic framework to tubular centrifuges or filter centrifuges is also applicable by considering the solids residence time distribution of these types of machines, the properties of the processed materials and neglecting the sediment transport.

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