Metal recovery - take out all residual metal from slags and ashes

Processes for metal recovery reach from fairly simple to highly complex – depending on the value and content of the metal in the slag on one side, and on the desired application for the residual slag on the other side. Process types might be grouped into

  • Simple crushing and screening processes for coarse metal recovery
    • for low value metals or low metal contents
  • Fine grinding processes for maximum metal recovery
    • for high value metals or high metal contents
    • wet or dry
    • get out nearly everything and have a uniform slag powder or slime as by-product
  • More complex pre-concentration processes for reducing the production of fines and grinding energy consumption
    • For brittle metals (like Ferrochromium) or if residual slag is marketed as aggregate
    • by sensor separation, jigging and fine gravity separation, magnetic separation and similar, metal recovery from pre-concentrates OR only free metal recovery

CALA has developed and optimised processes for all of those versions, wet or dry. We find out which process suits you best.

EXAMPLE: Dry grinding process for metal recovery and filler production

CALA together with Loesche GmbH have developed a new dry grinding and metal recovery process for slags, based on simultaneous grinding, drying, classifying and pre-concentration of metal in a Loesche Vertical Roller Mill and a downstream dry sorting technology for cleaning the metal product to a purity of +90%.

 

 

Process

Coarse slag preparation by conventional methods

  • Crushing and screening to -20 mm
  • Coarse (+20 mm) metal recovery by magnetic separation, density separation and/or sensor sorting
  • optional generation of coarse metal-free aggregates

Patented dry grinding and metal separation system

  • Simultaneous grinding, drying, classifying and pre-concentration of metal in a Loesche Vertical Roller Mill
  • Metal pre-concentrate is discharged through the mill overflow discharge
  • Metal-free filler is discharged through the air classifyer on top of the mill and collected in a de-dusting system
  • Metal pre-concentrate is further concentrated by dry magnetic separation, dry density separation and/or sensor sorting to final purity (+90%)
  • Middlings product from metal concentration is recirculated to the mill

The new process is characterized by the following features:

  • ~100% metal recovery for +10 mm fractions
  • 95…99% metal recovery for -10 mm fractions
  • +90% metal purity
  • well defined, easily adjustable filler product (as compared to the wet slimes generated during the analog wet grinding process)
  • energy saving grinding and drying technology
  • well defined, easily adjustable filler product (as compared to the wet slimes generated during the analog wet grinding process)
  • Thus, filler product is more amenable to any valorization method than the residue from the wet grinding process

A first plant for stainless steel recovery was commissioned at Recoval, Belgium, in 2014 (more info: Loesche)

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