Improvement of the Richardson-Zaki liquid-solid fluidisation model on the basis of hydraulics (PPT)

One of the most popular and frequently used models for describing homogeneous liquid-solid fluidised suspensions is the model developed by Richardson & Zaki in 1954. The superficial fluid velocity and terminal settling velocity together with an index, make it possible to determine the fluid porosity in a straightforward way. To maintain optimal process and control conditions in multiphase drinking water treatment processes, the porosity is kept relatively low. Unfortunately, the Richardson-Zaki index models tend to overestimate the minimum fluidisation velocity and therefore also result in less accurate predictions with respect to porosity values. We extended the Richardson-Zaki model with proven hydraulics-based models. The proposed models are compared with data from expansion experiments with grains applied in drinking water softening using the fluidised bed process. The porosity prediction error decreases from 15% to 3% and the minimum fluidisation velocity error from 100% to 12%.