In this article, we shall discuss the working principle, construction, advantages, disadvantages, and applications of Cupola Furnaces . We have also provided a PDF for the same. A Cupola furnace is one of the furnaces where we melt different types of metal some are cast iron, some are maybe bronze.
A Cupola furnace is a melting device. We used this device in the forging operation where Cast Iron, Bronze, and other alloying elements are melted. This is a very old device we used in manufacturing for melting because this system produces good cast iron from Pig Iron. The shape of this device is cylindrical but others size is also available. While choosing a them we keep some valid factors such as Melting Point Temperature, Shapes, and many more.
The Cupola Furnace is consists of the following
Legs are provided for supporting purposes.
The slag hole is used for removing or extracting the slag from the melting iron.
This is in taper form and from this, the melted iron comes out easily.
By tuyeres, we enter the gas to the proper burn of fuel.
In the Preheating zone, the heating process started and heats the metal charge to about 1090 degrees Celsius.
In the melting zone, we do not provide much heat to melt the metal charge because it’s already melted in the preheating zone with a temperature of about 1090 degrees Celsius.
From here we supply the charge to the furnace. The various charges for the cupola furnace are Pig Iron, Coke, and limestone.
The shell of the cupola furnace is usually made of steel and it’s called a steel shell.
This device is used in the system for preventing emissions from the fireplace.
The Cupola furnace works on the principle where we generate heat from burning coke and when the temperature of the furnace is above the melting point of the metal then the metal is melted. The charge introduced in the cupola consists of pig iron, scrap, casting rejection, coke, and flux. Coke is the fuel and limestone are added as a flux to remove undesirable materials like ash and dirt. The scrap consists of Steel and cast iron rejections.
Here Over the sand Bottom, Coke is in charge of extending up to a predetermined height. This serves as the coke bed within which the combustion takes place. The Cupola operation is started by igniting the coke bed at its bottom. After the Coke bed is properly Ignited, alternate charges of limestone, pig iron, and coke are charged until the level of the charging Door. Then the air blast is turned on and combustion occurs rapidly within the coke bed. Within 5 to 10 minutes after the blast is turned on the first molten cast iron appears at the tap hole.
Usually, the first iron which comes out will be too cold to pour into sand molds. During the cupola operation, molten metal may be tracked every 10 minutes depending on the melting rate and the capacity. All the oxygen in the air blast is consumed by the combustion, Within the combustion zone. The chemical reaction takes place which is,
C + O2 (from the air) → CO2 + Heat
This is an exothermic reaction. The temperature in this zone varies from 1550 to 1850 degrees Celsius.
Then hot gases consisting principally of Nitrogen and carbon dioxide moved upward from the combustion zone, where the temperature is 1650 degree Celsius. The portion of the coke bed if the combustion zone is reducing zone. It is a protective zone to prevent the oxidation of the metal charge above and while dropping through it. As the hot carbon dioxide gas moves upward through the hot coke, some of it is reduced by the following reaction.
3Fe + 2CO → Fe3C + CO2
This is an endothermic reaction.
The first layer of iron above the reducing zone is the melting zone where the solid iron is converted into the molten state. A significant portion of the carbon that is picked up by the metal also takes place in this zone. The hot gas is passed upward from the reducing and melting zones into the preheating zone which includes all layers of charge above the melting zone up to the charging Door. Since the layer of the charge is preheated by the outgoing gases which exist at the top of the cylindrical shell. The temperature is this zone is around 1090 degrees Celsius.
In conclusion, a cupola furnace is a popular melting furnace used in foundries for melting various types of metals such as cast iron, brass, and aluminum. The furnace works on the principle of combustion of coke, which generates heat to melt the metal charge in the furnace.
The construction of the furnace involves a cylindrical shell, refractory lining, tuyeres, and a charging door. Cupola furnaces are widely used in the production of automotive parts, pipes, and agricultural equipment. However, the use of has declined in recent times due to the increasing popularity of electric arc furnaces, which are more energy-efficient and environmentally friendly.
