Not sure of capability of HYSIS or ASPEN+ in modeling adsorption using Silica Gel.

In CHEMCAD a Component Separator UnitOp will provide the water removal at a specified efficiency, but gives no indication of packed bed performance (e.g., height and diameter).

Our ENVIROKIT software has a module to study adsorption. Click here to view the relevant manual.
You could use the Excel interface to simulate an Adsorption UnitOp using the equations detailed in manual.