Countercurrent Decantation Circuit Design for Washing of Bauxite Residue in Alumina Refinery Operations

Abstract

Bauxite residue generated during alumina refinery operations contains significant amounts of entrained caustic liquor and fine particulate matter, creating environmental and operational challenges associated with residue disposal and resource recovery. The present study investigates the design and optimization of a countercurrent decantation circuit for efficient washing of bauxite residue under industrial processing conditions. The research focuses on evaluating washing efficiency, caustic recovery, solids settling behavior, and water utilization associated with multistage decantation systems. Experimental analysis was conducted to examine the influence of slurry concentration, wash water flow rate, underflow density, stage configuration, and residence time on residue washing performance and liquor recovery efficiency. Results demonstrate that optimized countercurrent decantation operation significantly enhances the removal of soluble sodium compounds from bauxite residue while minimizing wash water consumption and improving overall process sustainability. The study further reveals that proper stage arrangement and controlled slurry flow conditions improve sedimentation characteristics and solid–liquid separation efficiency. Increased washing stages and optimized underflow control contributed to reduced residual alkalinity and improved recovery of valuable process liquor for reuse in alumina refining operations. Comparative assessment with conventional single-stage washing methods confirms the advantages of countercurrent decantation circuits, including improved washing efficiency, lower operational costs, and enhanced resource conservation.