Operating data for the hot-gas filtration system of the Integrated Gasification and Cleanup Facility (IGCF) at the Federal Energy Technology Center are carefully analyzed. A model for candle filters is developed and used to describe the ideal filtration process. The parameters of the model are evaluated with a least-square error fit procedure. It is shown that the model predicts the time variation of the pressure drop with reasonable accuracy. The model is used to evaluate the buildup of filter-cake thickness and the filter-cake permeability.