EVALUATION OF MAX HT® AT QUEENSLAND ALUMINA LTD

During the Digestion step of the Bayer Process, silica-containing minerals within bauxite are dissolved into caustic liquor and re-precipitate as sodalite. As a result, Bayer liquors are supersaturated in Silica at all points within the liquor circuit, which promotes scaling of process equipment with sodalite. This scaling is most problematic in heat exchange equipment responsible for heating spent Bayer liquor to Digester conditions, where high temperatures (>150°C) and high silica supersaturation promote high scaling rates. Cytec Industries have developed a chemical product (MAX HT^®) capable of inhibiting sodalite scale formation under spent Bayer liquor conditions^1,2. This paper outlines the details and results of first generation MAX HT^® trials conducted in the spent liquor circuit at the Queensland Alumina Refinery (QAL).