Cranfield University Power Generation Technology Centre conducted a study of metallic filters for hot gas cleaning. The total cost of this project was funded by the U.K. Dept. of Trade and Industry (DTI) and Microfiltrex (a Division of Porvair Filtration Group Limited).

Advanced power generation systems, based on gasification, are being developed. Hot gas cleaning technologies for gasification systems offer the potential of a lower cost approach to pollutant control and gas turbine protection, leading to simpler cycle configurations with associated efficiency advantages. The unreliability of the ceramic filter elements used in demonstration trials and the high capital cost of these systems have hindered their application and are factors restricting the uptake of gasification power plants in general. The successful development of a durable metallic filter system for the ABGC would be a major step towards its implementation.

Metallic filter media provides a number of significant advantages over ceramics. In order to realize fully the cost and environmental advantages, it is essential that the systems provide not only efficient contaminant removal but also have the reliability and availability required of the overall system. It is now apparent that reliable, lower cost filter systems can be operated using metallic filter media, provided improved materials selection and advanced fabrication methods are developed.

This project successfully investigated the performance of a range of candidate materials for the manufacture of filters for use in gasifier (IGCC and ABGC) hot gas paths.

The following conclusions were reached.

Damage was greatest on the deposit-coated specimens.

The damage to alloys exposed in the low H₂S (ABGC) gas test was significantly lower than in the equivalent high H₂S (IGCC) gas test.

Existing corrosion life prediction models developed at Cranfield University have been modified and extended. It has been demonstrated how to predict the expected service lives and upper temperature limits of filter media under operational IGCC filter conditions.

The design requirements for a prototype element for IGCC/ABGC applications have been identified and related to the data produced in this project. Life prediction models have been illustrated for sintered metal fiber and sintered metal powder filter media.