Preliminary evaluation of the FIBROSIC candle filter for particulate control in PFBC

The FIBROSIC candle filter element is made by the vacuum-forming of a select blend of alumino-silicate fibres with silica and alumina binders. It is potentially useful as a hot-gas clean-up device for control of particulates in pressurised fluidised-bed combustion (PFBC). Relative to the more widely studied SiC candle filter, it has the advantages of light weight, low cost and reduced tendency to thermal-shock breakage. With Illinois No.6 high-sulphur coal in a laboratory-scale PFBC/alkali sorber facility, filters of both types were tested for particulate-collection efficiency; permeability characteristics; and physical and mechanical strength and integrity. Tests were conducted at 800-825°C with a system pressure of 9.2 bar. Filter-face velocities were 5.1 and 10.2 cm s -1 during test periods of 8 and 9.5 hours for SiC and FIBROSIC candle filters respectively. The filters were periodically cleaned by a reverse jet pulse of nitrogen gas. Both types achieved particulate-collection efficiencies of >99.9% and exhibited comparable permeability characteristics. Although the FIBROSIC candle filter possesses inherently lower bursting strength than the SiC, its physical and mechanical strengths were shown to be sufficient under PFBC conditions.