Continuous liquid extraction from saturated granular materials

- A two-dimensional differential equation similar in form to Richard's equation is derived and solved.
- Effects of capillary and adsorptive forces are taken into account in the model.
- Two dimensional pore saturation, pressure head and liquid flux distributions are predicted.
- Effects of rotation speed, inlet slurry flow rate and cone angle on extracted liquid fraction are investigated.
- The model can be used as a design tool for the development of continuous filtering centrifuges.

A steady-state model for continuous extraction of liquid from saturated cake in a conical filtering centrifuge is presented in this work. The model describes unsaturated liquid flow through a cake of solid particles sliding along a conical screen basket. Effects of capillary and adsorptive forces are taken into account by using the liquid retention curve and the hydraulic conductivity function. Mass balance and the Darcy-Buckingham equations are used to develop a transport equation for the centrifuge similar in form to the Richards equation. The model is applied to predict extraction of molasses from sugar sucrose particles and can be applied in other applications where liquid is extracted from saturated granular materials. Distributions of pressure head, pore saturation, and drained liquid flux in the cake are predicted. Effects of cone geometry, rotation speed and mass flow rate on the fraction of extracted liquid are investigated. The model presented in this work can be used for the design of continuous filtering centrifuges and the prediction of optimal operating parameters in various applications.