Chemical Engineering Research & Design, Vol.154, 303-315, 2020
Modeling and simulation of an industrial falling film evaporator for alumina production
This paper describes a mathematical model developed by combining a lumped parameter model (LPM) and a distributed parameter model (DPM) for an industrial falling film evaporator used for the evaporation of a sodium aluminate solution (SAS) during the alumina production process. In the LPM, the dynamic equations were deduced to calculate the concentration of the evaporator outlet. The DPM was developed to study the evaporation occurring in each heating tube, in which the residence time, film thickness, liquid load of the feed, and the amount of heat transfer were established as functions of the longitudinal location from the entrance down the tube. Material properties related to the compositions, such as the density and viscosity, were fitted from industrially measured data acquired during a heat balance test. The modeling of the overall heat transfer coefficient based on fluid mechanics is discussed. The effect of scaling, which is an obstacle to accurate modeling, was considered using the industrial history data combined with the calculations of the mass and heat balance equations. The simulated concentrations of the products revealed the high accuracy of the model. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.