A parametric study of filtration through a ceramic candle filter

Abstract

Ceramic candle filters have been developed for cleaning high-temperature high-pressure (HTHP) gas streams. They meet environmental and economical considerations in combined cycle power plant, where gas turbine blades can be protected from the erosion resulting from the use of HTHP exhaust from the fluidized bed. Ceramic candle filters are the most promising hot gas filtration technology and have demonstrated high collection efficiencies at high-temperature high-pressure conditions. This paper reports a computational fluid dynamics (CFD) investigation of a candle filter in cross-flow arrangement. The aim is to increase understanding of the deposition process and the factors that affect the build-up of the filter cake. A parametric investigation is undertaken, with particular emphasis on the effects of the ratio of the approach cross-flow velocity to filter face velocity on the deposition pattern as a function of the particle size (1–300 μm). Velocity fields and particle tracks are presented, in addition to the radius of convergence which is a parameter that characterizes the deposition process for each flow regime. Furthermore, a method has been developed for predicting filter cake growth using CFD and particle deposits distributed around the filter element surface uniformly for particle sizes below 50 μm. The paper contains a potential flow solution for the flow around a single porous filter element in cross-flow.