Freeze concentration of milk and saline solutions in a liquid–solid fluidized bed: Part II. Modelling of ice removal

Liquids can be concentrated via the process of freeze concentration using a fluidized bed heat exchanger (FBHE) as demonstrated in part I for milk and saline solutions. The effect of fluidized particle size, bed porosity and type and concentration of fluid were analysed previously which led to the development of an empirical model presented in this paper. The Wood and Woodford (WW) fatigue erosion concept, previously developed for metal erosion in tubes, was applied to the phenomenon of ice removal inside the FBHE. The ice strength or its ease of removal was measured in the form of a lumped model parameter γ. Increased values of γ allowed the fluidized bed to achieve stable operation at higher cooling duties with higher bed porosity. γ values for milk were lower than for NaCl solutions indicating that it is harder to remove ice formed from milk than from NaCl solutions. For both milk and NaCl solutions, γ increases with increasing solution concentration.