ACID CLEANING OF TITANIUM BASED SCALES FORMED ON PREHEATERS IN THE BAYER PROCESS

Today, Bayer process is the basic method for producing alumina from bauxite. Bauxite does not only contain alumina but also contains iron, silicon, titanium and other impurities. Impurities are also dissolving with alumina in hot caustic solution and results to scale formation on several sections of the process. Because of the changing working conditions on different parts of the Bayer process, scale formation occurs having different characteristics at different parts of the process. Scales must be cleaned periodically due to the decreasing heat transfer efficiency and increased energy costs due to scale build up on the heat exchanger surfaces. As the characteristics of the scales are changing form one section to another there is not only one effective solution to remove all kind of scales. The purpose of this study is to find effective chemical compositions for acid cleaning of TiO2 containing scales on Bayer process.