Mathematical Modeling of Wiped-Film Evaporators.

摘要

A mathematical model and associated computer program were developed to simulate the steady-state operation of wiped-film evaporators for the concentration of typical waste solutions produced at the Savannah River Plant. In this model,which treats either a horizontal or a vertical wiped-film evaporator as a plug-flow device with no backmixing,three fundamental phenomena are described:sensible heating of the waste solution,vaporization of water,and crystallization of solids from solution. Physical property data were coded into the computer program,which performs the calculations of this model. Physical properties of typical waste solutions and of the heating steam,generally as analytical functions of temperature,were obtained from published data or derived by regression analysis of tabulated or graphical data. Preliminary results from tests of the Savannah River Laboratory semiworks wiped-film evaporators were used to select a correlation for the inside film heat transfer coefficient. This model should be a useful aid in the specification,operation,and control of the full-scale wiped-film evaporators proposed for application under plant conditions. In particular,it should be of value in the development and analysis of feed-forward control schemes for the plant units. Also,this model can be readily adapted,with only minor changes,to simulate the operation of wiped-film evaporators for other conceivable applications,such as the concentration of acid wastes. (ERA citation 02:000295)