MODELING OF MULTICOMPONENT DRYING OF A SHRINKING GEL CYLINDER CONTAINING DCCA

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 cond itions or by convective drying. During convective drying gels signific antly shrink producing porous glass-like xerogels. Adding a third comp onent called DCCA (Drying Control Chemical Additive) to sol crates a d iffusional barrier which lowers the drying rate and also reduces crack ing. This paper presents formulation and solution of a rigorous model of multicomponent diffusion both in liquid and gas phase in the case o f convective drying of a gel cylinder containing a ternary mixture of ethanol, water and formamide as DCCA. Details of the numerical techniq ue and methods used for prediction of physico-chemical property data i nvolved in the solution of the model are presented. A short discussion of the obtained results follows. The model can provide a basis for a more complex process description incorporating drying stresses and pre dicting conditions at which cracking occurs.