Bott, R., Langeloh, T., Hahn, J., Arpe, R., Vollmers, A.R., Lalla, A.

Bauxite residue is the main by-product of alumina refineries which has to be treated and disposed of in tremendous amounts. Proper bauxite residue filtration, treatment, long-termed disposal or even reusage influence the sales cost per tonne alumina remarkably due to caustic loss in the disposed residue, residue handling and disposal technology, water consumption for washing and water recirculation from disposal area, maintenance of the disposal ponds and especially due to financial reserves per tonne mud for later recultivation of the disposal area. Numerous attempts have been undertaken to solve at least some of the problems of bauxite residue disposal or to make it available for any industrial re-usage. Semi-dry mud stacking by different treatment/transportation measures is the latest state of the art causing a series of new problems like (cost) intensive engineering, monitoring of the disposal area or even dust problems. Only exotic examples are known to re-use bauxite residue in industrial applications in amounts worth mentioning. This situation is mainly caused by major disadvantages of the dry bauxite residue, such as thixotropy, non bulk-like transportation and handling behaviour, high moisture content and high content of soluble soda. Any new technical solution which makes the bauxite residue acceptable for a really dry disposal or even industrial re-usage is directly linked with overcoming the above mentioned disadvantages. The Hi-Bar® Steam Pressure Filtration is an innovative technology already applied to the chemical industry, which has now been shown to be able to produce a really dry, easy to handle, bulk-like material. In a German alumina refinery a Hi-Bar® pilot plant using Steam Pressure Filtration has been operated for several weeks to produce a large amount of dry bauxite residue under industrial conditions.