DRYING OF SILICA-GELS WITH SUPERCRITICAL CARBON-DIOXIDE

Results of drying experiments of aerogels with supercritical carbon di oxide are reported. In addition to the results of experiments with a p ilot extracting apparatus, a preliminary design is also given of a lar ge-scale supercritical carbon dioxide extraction plant to be used for drying of aerogels. From the experiments it was found that crack-free aerogels could be obtained when drying with carbon dioxide under super critical conditions. The lowest temperature and pressure at which crac k-free aerogel samples were obtained was at 35-degrees-C and 85 bar, r espectively. The temperature had a minor influence dn the drying time. It was also found that the diffusion of ethanol into the aerogel pore s limits the drying time. This limitation implies that the thickness o f the aerogel tiles will have a large influence on the cost of drying of an aerogel.