Construction and works

ALOCLIN

SALT SLAG TREATMENT BYPRODUCTS FOR CLINKER PRODUCTION

SECONDARY ALUMINIUM REFINING REQUIRES THE USE OF SODIUM AND POTASSIUM CHLORIDE MIXTURES as fluxes to prevent oxidation, increase yield and boost thermal efficiency; but in doing so, it generates so-called aluminium salt slag which is a hazardous waste. The recovery of salt slags aims at separating the aluminium metal and salt from the contaminants so that all components can be reused. RESAL, a company of the Otua Group, carries out the necessary grinding and separation treatments, and the hydrometallurgical treatment of the non-metallic fraction (NMF) of the salt slag, and is able to fully close the aluminium recycling and reuse cycle. For ALOCLIN, the cement company SOCIEDAD FINANCIERA Y MINERAL and INATEC, the Otua Group’s R&D Unit, have collaborated in the project.

The main source of input waste for the Otua Group’s secondary aluminium refinery is ELVs, which are subject to reuse, recycling and recovery targets that are difficult to achieve with the treatment technologies currently in operation.

RESAL
OBJECTIVES
  • Adapt a by-product, NMF from the hydrometallurgical treatment of salt slag, to be used in a highly demanded application, i.e., clinker production, as a replacement for the metal oxides normally used, based on the similar composition of bauxite used in the cement industry and NMF from salt slag.
  • Increase the percentage of material recovery in the treatment of ELVs.
RESULTS
  • Definition of specifications to be met by the material destined for the cement production company.
  • Characterisation of NMF resulting from the hydrometallurgical treatment of salt slags (free moisture, hydration, chlorides, aluminium, reactive species, and chemical composition).
  • The NMF refurbishment encountered technical problems which did not allow the required specifications to be met.
CONCLUSIONS
  • ALOCLIN has studied the use of aluminium salt slag NMF in the production of clinker and has demonstrated, according to the characterisations, that it is possible to obtain raw material with the appropriate characteristics for clinker production from salt slag NMF.
  • RESAL is still interested in recovering the NMF resulting from the management of salt slag, under the specifications set by the cement production industry, and continues to work at process level to obtain the operability that will allow it to meet the needs of ALOCLIN in the future.

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