Filter cake washing is an important unit operation in different process industries. In order to reduce operating costs like wash liquid or to reduce filtrate liquid it is possible to use multi-stage countercurrent washing on continuously operated filters. Mechanical dewatering by gas differential pressure can additionally decrease the wash liquid consumption.
The single-stage filter cake washing in laboratory scale in filter nutsches is technically and academically well understood but not all complex mechanisms of the multi-stage countercurrent filter cake washing are clarified yet.
The washing process is typically divided into three regimes. Those are the displacement, the dispersion and the diffusion regime. The first two regimes can be described by the dispersion model. Expanding the dispersion model with the two chamber model for stagnant fluid volumes allows describing the diffusion regime. For the single-stage filter cake washing, analytical solutions are already developed. To solve the multi-stage countercurrent filter cake washing, numerical calculation models are needed. Therefore a simulation tool was developed to provide the opportunity to analyze and evaluate different washing scenarios. Single-stage washing experiments provide the needed parameters for the simulation of the multi-stage filter cake washing.
To validate the model the results of washing experiments in a filter nutsche for two and three stages will be compared with the simulated washing curves based on single stage washing experiments.
Furthermore different simulation results of multi-stage countercurrent filter cake washes will be shown as well as a procedure for a scenario based evaluation for designing cake washing processes
Session: L6 - Cake Filtration - Characterization, Modelling, Simulation
Day: 23 October 2019
Time: 10:45 - 12:00 h