Residue

Review of Bauxite Residue Re-Use Options 2009

The question of what to do with bauxite residue arose with the development of the Bayer process for alumina refining and the recognition that it generated a large

amount of waste material. In the subsequent 120 years residues were disposed of with the aim of long-term storage, with a wide range of industry practice depending on local circumstances. Despite over 50 years of research and hundreds of publications and patents on the subject, little evidence exists of any significant utilization of

bauxite residue at any time. In this review the reasons are examined, future opportunities are identified, and a way forward is proposed. This review considers all avenues of residue “re-use”, or more appropriately use , but concentrates on the few highest volume uses of lowest risk. Utilization is considered as taking the residue in some non-hazardous form (as a by-product) from the alumina refinery site and using it as feedstock for another distinct application. Although residues from different

bauxites have generic similarities, their specific make-up and residue location can influence their suitability for a given type of use. There are four primary reasons for

this inaction: volume, performance, cost and risk, with the last two probably being overriding. In tenns of cost there are better options for raw material input from virgin

sources (lower cost for better grades) that do not come with the same perceived risks as bauxite residue. The risks are composition based, both technical and community perception and relate to: soda, alkalinity, heavy metals and low levels of naturally occurring radioactive material (NORM). Amongst the outcomes of this review are a set of Research Priority recommendations to address the Knowledge Gaps identified that, amongst other factors, are impeding the implementation of residue use.

To successfully transition bauxite residue from a by-product to be disposed at a cost, to a product of value, will require more than the development of technological solutions. Arguably a choice of technologies already exists to fully utilise bauxite residue. The barriers that will need to be overcome may be summarised as follows:

Volume

  • Reuse options must be high volume

Performance

  • Substituting for low cost virgin raw materials — performance must equal
  • Effective removal/treatment of soda for some applications

Cost

  • Evaluating the economics of current BRDA management
  • Economics of additional downstream processing
  • Co-use of other by-product waste streams

Risk

  • Removal of soda, alkalinity and removal or immobilization of heavy metals and NORM
  • Lifetime of the secondary product
  • Liability issues covering heavy metals and NORM components.

To provide a framework to move forward, residue utilization has been organized into

three Value Opportunities and these are each further divided into three Key Priority

Areas (KPAs).

Value Opportunity 1: Construction and Chemical Applications

  • KPAI : Civil and building construction
  • KPA2: Catalysts and adsorbents
  • KPA3: Ceramics, plastics, coatings and pigments

Value Opportunity 2: Environmental and Agronomic Applications

  • KPA4: Waste water and effluent treatment
  • KPA5: Waste gas treatment
  • KPA6: Agronomic applications

Value Opportunity 3: Metallurgical Applications

  • KPA7: Recovery of major metals
  • KPA8: Steel making and slag additive
  • KPA9: Recovery of minor metals