1. Overview

Bauxite residue is a waste stream generated during the Bayer process when alumina is produced from bauxite ore. Due to its alkalinity, fine particle size, and high moisture content, bauxite residue requires appropriate engineering and management solutions to ensure safety and minimize environmental impacts.

As the alumina industry moves toward more sustainable practices, filter pressing combined with dry stacking is increasingly being applied to reduce the moisture content of bauxite residue, improve storage stability, and recover water for reuse in the production process.

2. Technology Objectives

Filter pressing and dry stacking are intended to achieve the following key objectives:

• Reduce the moisture content of bauxite residue;
• Improve its suitability for transportation, spreading, and layered placement;
• Recover water for recycling back into the production process;
• Reduce the storage area required compared with certain high-moisture slurry disposal methods;
• Reduce risks associated with managing large volumes of liquid slurry.

3. Operating Principle

After separation and thickening, bauxite residue is fed into a filter press system. Under pressure, the liquid phase passes through the filter medium and is recovered, while the solid phase is retained to form filter cake with a lower moisture content.

The filter cake is then transported to the storage area, where it is spread and placed in layers in accordance with the design of the storage facility. Water recovered during filtration can be recycled back into the production system.

4. Typical Process Flow

Bauxite Residue Thickening → Intermediate Tank → Feed Pumping → Filter Pressing → Filter Cake → Transportation → Spreading and Layered Placement in the Dry-Stacking Area

The actual process configuration may vary depending on the characteristics of the bauxite residue, refinery capacity, and storage-facility design.

5. Main Equipment

A typical system may include:

• Thickening equipment;
• Intermediate storage tanks;
• Residue feed pumps;
• Filter press system;
• Filter cloth washing system;
• Filtrate recovery and water-recycling system;
• Conveyors or other filter-cake transportation equipment;
• Spreading, compaction, and layering equipment;
• Drainage and water-collection systems within the storage area.

6. Key Parameters to Be Controlled

Operating parameters and material properties should be controlled according to the design of each system, including:

• Solids content and moisture content of the filter cake;
• Filtration characteristics and filtration capacity;
• Alkalinity of the bauxite residue and recovered water;
• Geotechnical properties relevant to the design and operation of the storage facility;
• Quality of recovered water for recycling to the refinery.

7. Technology Advantages

Filter pressing and dry stacking can provide a number of benefits:

• Recover and recycle a significant amount of water back into the production process;
• Improve the efficiency of storage-area utilization;
• Reduce the amount of free water within the storage facility;
• Facilitate the transportation, spreading, and layered placement of bauxite residue;
• Support the management, closure, and rehabilitation of the storage area;
• Contribute to improved environmental performance in alumina production.

To ensure long-term safety, the storage facility must still be appropriately designed and managed, including controls for drainage, stormwater, dust, geotechnical stability, and environmental monitoring.

8. Trends and Application Potential

Filter pressing and dry stacking are increasingly being adopted for bauxite residue management at alumina refineries to reduce stored water volumes, increase water recovery, and improve the efficient use of storage areas.

Technology selection should take into account bauxite residue characteristics, climatic and topographical conditions, environmental requirements, and the economic feasibility of each project.

9. Conclusion

Filter pressing combined with dry stacking is an important solution for modern bauxite residue management in the alumina industry. The technology reduces residue moisture content, increases water recovery, and improves storage-area efficiency, thereby supporting safer production and sustainable development.