Modeling Of Multicomponent Drying Of A Shrinking Gel Cylinder Containing Dcca

Abstract

ABSTRACT Inorganic chemical gels obtained by hydrolysis/condensation of organic precursors (alcoxides) contain alcohol and water mixture which fills pores of the gel. This mixture is either removed in supercritical conditions or by convective drying. During convective drying gels significantly shrink producing porous glass-like xerogels. Adding a third component called DCCA (Drying Control Chemical Additive) to sol crates a diffusional barrier which lowers the drying rate and also reduces cracking. This Paper presents formulation and solution of a rigorous model of multicomponent diffusion both in liquid and gas phase in the case of convective drying of a gel cylinder containing a ternary mixture of ethanol. water and formamide as DCCA. Details of the numerical technique and methods used for prediction of physico-chemical property data involved in the solution of the model are presented. A short discussion of the obtained results follow. The model can provide a basis for a more complex process description incorporating drying stresses and predicting conditions at which cracking occurs.