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CUPOLA FURNACE
Introduction
For many years, the cupola was the primary method of melting used in iron foundries.
The cupolas is one of the only methods of melting which is continuous in its operation;High melt rates;Relatively low operating costs;Ease of operation
working of cupola furnace
The cylindrical body of the furnace is oriented vertically, thus allowing gases to escape out of its top. Two doors seal the bottom opening of the furnace during normal operation; however, at an operating cycle's end, they can be opened to empty the furnace of all remaining material.
The gases released by the cupola's operation can be controlled by fitting its top opening with special "caps" that absorb the heated gases released during firing, cooling and filtering before releasing them into the atmosphere.
Preparation & Smelting
To prepare the furnace for firing, sand is first piled around the tap-hole, on top of which layers of fuel are stacked and gradually heated. A special type of coal called coke, which has been processed by burning away noncarbon impurities, serves as the cupola furnace's main fuel source.
Once the layers of coke have reached a sufficient height, metal pieces are inserted through the top opening, along with a limestone flux that removes impurities from the metal during melting.
Once the furnace is sufficiently filled with fuel and crude material, air is blasted into the combustion mixture, increasing the temperature inside the furnace. Some furnaces have special devices that insert pure oxygen gas into the furnace's interior
Soon molten metal begins to accumulate around the tap-hole and can be extracted from the furnace. As molten metal is removed, more pieces of crude metal are inserted through the top hole to maintain a constant level of material inside the furnace.
