The Sandy Desilication Product Process Concept

Reactive silica is the most detrimental impurity in bauxite. When bauxite is contacted with Bayer liquor, reactive silica dissolves and then precipitates as a sodium aluminum silicate known as the desilication product (DSP), which is discarded along with the bauxite residue and maintained in long-term storage facilities. DSP recycling using bauxite residue lime sinter-leach is prohibitively expensive due to the high energy requirement for heating as well as high investment costs. In the sandy desilication product process, DSP is coarsened by controlling the desilication conditions, which enables the DSP fraction of the residue to be concentrated by physical separations. The DSP concentrate can then be recycled by sinter-leaching, whereby sodium and aluminum are returned to the Bayer process, reducing the burden associated with bauxite residue and facilitating total residue treatment options. Results are presented herein demonstrating DSP particle enlargement by seeding the reaction and controlling the supersaturation.