(586j) Dynamic Modeling of Encrustation and Mitigation Strategies in a Continuous Plug Flow Crystallizer

Authors: 
Majumder, A., Loughborough University
Nagy, Z. K., Purdue University



Encrustation, also known as scaling or crystallization fouling, on the wall of plug flow crystallizers (PFC) can cause major operating and economic problems in pharmaceutical industries. These include increased energy consumptions due to increment of thermal resistance and pressure drop, and unplanned plant shut down due to clogging of the crystals originating from reduction of flow area.  In this work, a mathematical model for predicting the dynamic behavior of a PFC undergoing encrustation is presented. This model, which is adapted from the fouling model in heat exchangers by Coletti and Macchietto [1] and Chanapai [2], seeks to predict the encrustation thickness by tracking the thermal resistance.  In addition, a population balance model for describing the crystallization process in the PFC is coupled with the encrustation model in order to obtain the appropriate concentration profile along the PFC as well as product crystal size distribution (CSD). Based on this model, mitigation strategies are also proposed that include heating cycles to overcome the problem of encrustation.

[1] Coletti, F. and Macchietto, S. (2011). A Dynamic, Distributed Model of Shell-and-Tube Heat Exchangers Undergoing Crude Oil Fouling. Industrial & Engineering Chemistry Research 50(8): 4515-4533.

[2] Chanapai, A. (2010). Modeling of crystallization fouling in shell-and-tube heat exchangers. Master's thesis, Department of Chemical Engineering and Chemical Technology, Imperial College London.