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Fundamental Modeling of Black Liquor Falling Film Evaporators

Authors: Zdravko I. Stefanov and Karlene A. Hoo*
* Department of Chemical Engineering, Texas Tech University


Fundamental modeling of evaporators found in the pulp and paper industry is a very challenging task. The physico-chemical phenomena that occur do not lend themselves readily to known mechanisms and in many instances data to support these hypotheses are difficult to obtain. In this work, a distributed parameter model (a system of partial differential equations - PDEs) based on first-principles knowledge about fluid dynamics and heat transfer processes is developed for one type of an evaporator, that of a falling film lamella type black liquor evaporator. Primarily, the model describes falling film evaporation on one lamella. The model is solved using orthogonal collocation on finite elements when there are disturbances in the mass feed rate and feed dry solids content and wall temperature; and in the presence of scaling.


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Corresponding Author: Karlene A. Hoo