Different types of metals are used for melting different metals. Various Furnaces types are cupolas, electric arc, induction, hearth or reverberatory and crucible. Due to the different nature of metals, varying inputs are required and different toxic wastes are released from each type.
After the metal has been melted, it is poured into the cast already made previously and made to cool and set. Silica sand, moisture, oils and green sand are mixed together to form a mould cavity. Metal is then poured in this cavity. When the metal is cooled, it is easily separated from the mould. This type of sand should b capable of handling high temperatures and pressure, allow gases to escape, have a constantly small grain size and be non-reactive with metals.
The wastes produced by foundries depend on the type of metal, foundry types.gaseous wastes are usually the largest pollutants. They contain metal, semi-volatile and volatile organic compounds. Emission control systems can be installed to capture these gases.
Liquid wastes in foundry results from water used to chill metal. Water used for cleaning the floor & other maintenance can also formulate liquid waste. A water treatment plant can be installed for water waste.
Solid wastes come from slag, sand, spent refractories, and emissions control dust. For this various process like sand reclamation, attrition sand reclamation, dry sand reclamation, wet sand reclamation, etc is used. Sand may also be recycled for outside processes.
Slag and emission are also a waste produced by a foundry. These can be fed back to furnace to recover any metal, which can possibly be recovered.
Other special foundry processes are thermal galvanization and electro less nickel plating.