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UNDERSTANDING MATERIAL PROPERTIES TO OBTAIN MAXIMUM EFFICIENCY FROM YOUR FILTERS

Parent L

Filters are used in many steps of alumina production. For instance, they are used to remove impurities from Bayer liquor or to limit emissions in alumina calciners. Flexible polymers are used for Bayer liquor filtration whereas ceramics, more resistant to higher temperatures, are used to treat gas coming from the Alumina calcination process. Whatever the application, different material properties are required. Making the proper selection of material is a key factor in optimizing filter performance. This paper presents a different point of view in selecting appropriate media to optimise liquid or gas filtration properties. Depending if metal, polymer or ceramic are required, the media is available commercially through different forms. Woven fabric, felt, foam and also membrane are among possible choices of media. In order to obtain correlation between properties, limits and microstructure, micrographs using scanning electron microscope are presented. These observations, along with known properties, will help in understanding material properties. However even the best filter fails with time, therefore this paper also discusses failure modes like hydrolysis, fatigue and plugging.