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Last updated: April 21, 2014

What Does Skimming Mean?

Skimming is a technique of metal refining through concentrating metal ore. It is the removal of any material or particles that are floating on the surface. Most of the items float to the top of the water and are skimmed off or removed.

Skimming stations are the locations inside a basic oxygen process furnace shop where slag is removed from the top of the molten metal bath.

The skimming technique is used in metallurgical processes to concentrate valuable matter or refining metals.


Corrosionpedia Explains Skimming

Skimming may refer to:

  • Material that is skimmed off a liquid
  • Froth containing concentrated ore removed during a flotation process
  • Slag, scum or impurities removed from molten metals

In mineral treatment and mining, one process for concentrating the metal-bearing mineral in an ore is froth flotation. Crude ore is ground to a fine powder and mixed with water/frothing reagents and collecting reagents. When air is blown through the mixture, mineral particles cling to the bubbles, which rise to form a froth on the surface. The waste material (gangue) settles to the bottom, the froth is skimmed off, and the water and chemicals are distilled or otherwise removed, leaving a clean concentrate. This is used for a number of minerals, particularly silver.

Since impurities are present in the concentrate and remain in copper during processing, they may be removed by a fire-refining step in which air is blown into the molten copper to oxidize the impurities selectively to form a slag or oxide gas. The slag is then skimmed off and the copper is covered with charcoal to prevent further oxidation. Any blast-furnace slag and slag formed during desulfurization is skimmed off before the iron is charged.

Specific ore applications where skimming is used include:

  • Sulfide ores
  • Copper
  • Copper-molybdenum
  • Lead-zinc
  • Lead-zinc-iron
  • Copper-lead-zinc-iron
  • Gold-silver
  • Oxide copper
  • Lead

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