Statistical Modelling of Operating Parameters on Bauxite Slurry Hyperbaric Filtration

The Hydro Alunorte refinery receives bauxite slurry used in the alumina production from Mineração Paragominas, both sites located in Pará—Brazil. This bauxite slurry, which is dewatered in hyperbaric filters located in Alunorte, has been affecting the lifetime of the pipeline through erosion and corrosion processes since the beginning of its transportation in 2008. To increase the lifetime of the pipeline and preserve the dewatering plant production capacity, this work evaluated the influence of filter rotation, basin level, and feed slurry density on filter productivity by applying a factorial design. The experiment, which was carried out on the industrial filters, complemented the outcome of a previous investigation executed on a laboratory scale using slurry density, top size, and pH as control factors to assess the solids throughput through Box Behnken Design statistical technique. Results indicated that a top size reduction and pH elevation by the addition of milk of lime decreases the productivity by 13.3%. However, an increase in density, filter rotation, and basin level proved to offset and surpass this predicted loss, making viable the pipeline lifetime increase project and preventing alumina production losses in Alunorte.