Smelting

What Does Smelting Mean?

Smelting is the process of extracting metal from ore by a process of chemical reduction. This makes the metal usable for various types of manufacturing.

The metal found in ore is frequently oxidized, meaning it requires a chemical transformation to remove the oxygen before it is extracted. To do this, the ore is put into a blast furnace along with carbon-rich fuel and flux to separate metal from the oxygen and other elements and impurities.

Safeopedia Explains Smelting

Some chemical reactions of metallic ores with carbon that can produce metal include:

• Mercury oxide: 2HgO + C = 2Hg + CO₂
  
• Hematite: 2Fe₂O₃ + 3C = 4Fe + 3CO₂
  
• Cuprite: 2CuO + C = 2Cu + CO₂
  
• Cassiterite: 2SnO₂ + 2C = 2Sn + 2CO₂
  
• Silver oxide: 2Ag₂O + C = 4Ag + CO₂
  
• Minium: 2PbO + C = 2Pb + CO₂

Smelting vs. Melting

Smelting should not be confused with melting, as melting at high temperatures without the use of a reducing agent will produce molten ore but will not melt the metal out of the ore. Melting only changes the state of the ore from solid to liquid.

The Smelting Process

The smelting process requires:

• A smelting furnace (such as a blast furnace, reverberatory furnace, or electric arc surface)
• A fuel source
• A reducing agent
• Flux (such as limestone, borax, and silica)
• Temperature control and monitoring
• Tapping tools
• Casting equipment

The ore is crushed and processed before being introduced into the furnace. A fuel source such as coal, coke, natural gas, or electricity is used to generate the required temperatures. A carbon-rich reducing agent such as charcoal or coke is then added to help reduce metal oxides into their elemental forms. Finally, impurities are removed using a flux substance that helps in the formation of liquid slag, which can be easily removed from the furnace.

Hazards Associated with Smelting

The smelting process generates a tremendous amount of thermal energy and can pose serious health hazards to unprotected workers. Some hazards of the molten metal industries include:

• Respiratory hazards from airborne contaminants, such as metal dust, silica, carbon monoxide, and fumes
• Hearing loss from the noise levels generated during the smelting and casting process
• Eye injuries due to optical radiation, flying particles, and sparks
• Burn injuries due to molten metal splash and radiant heat from the furnace

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