Sunday, November 27, 2011

Key Considerations for Design of Bauxite Residue Storage Pond

Hi Friends,

In earlier posts, we have already discussed about the specifications and generation rate of Bauxite residue (Red mud) in Alumina refinery. The residue generation rate is generally 15 to 30% more than the production rate of product alumina. Thus, even for a typical Alumina refinery of 1.0 Mtpa calcined alumina, residue generation will vary from 1.15 Mtpa to 1.30 Mtpa. In a few cases, the residue generation rate is even higher where poor quality Bauxite is processed. This simply reveals that requirement of residue storage will be very high. Hence, it becomes essential In present post, we will discuss the major considerations while design of Bauxite storage pond (red mud pond) as outlined below.
  1. Location: Site for construction of Bauxite residue storage pond (Red mud pond) is located close to the Alumina refinery to minimize the energy consumption for movement / transportation of residue but at the same time away from the habitation.
  2. Natural Topography: It is preferred to locate the Bauxite residue storage pond in low lying area surrounded by hills to save on construction cost of dyke. The excavated soil is used to minimize the requirement of borrowed earth for construction of dyke / dam.
  3. Characteristics of Soil: Soil having lower porosity with more of clay is considered better for construction of residue storage pond as it gives improved strength and less chance for percolation of alkaline water outside.
  4. Volumetric Capacity: Volumetric capacity is decided based on residue generation rate and life of storage pond. As such base width is taken in to account for keeping in mind the final height of storage pond but phasing of dyke raising is done accordingly.
  5. Rain Water Drainage: All along the dyke, proper drainage is made for diverting the rain water outside so that erosion of dyke will be minimal. 
  6. Geo-Textile Lining: Entire storage pond including dykes are provided with geo-textile lining to ensure no percolation of water from storage pond to underground natural stream as it may cause harm to humanity.
  7. Adequate Free Board: Minimum free board of 1.5 meter is is considered while designing the residue storage pond. This provides additional capacity and safety provision for the future. 
These are a few major issues which are taken care of during design of Bauxite residue storage pond. Please put your views / suggestions / remarks / comments, if any.

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Kunwar Rajendra

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