Comparing cupolas with induction furnaces, you can see that both are good equipment, but they cannot be used in all applications.Although the cupola is the first traditional equipment to be invented, it still has great advantages over electric furnaces as technology progresses.First, it is a continuous production smelting equipment; second, its productivity can now reach over 100t per hour, which is not possible with electric furnaces.In addition, the cupola is more energy-saving than the electric furnace: it needs heat of 1 322 600 kJ to melt the 1kg iron charge at 24 C room temperature to 1500 C liquid iron.The theoretical heat generating capacity of cast coke is 30400k J/k G.Coke is needed to melt 1t iron to 1500 C. If the efficiency of cupola is 30%, then the standard coal is 141.26kgce. If the efficiency of cupola is 40%, the standard coal is 105.95kgce.1K W.h can generate 3600K J of heat, so it needs 367.4kW.h of electric power to melt 1t and 1500 C of molten iron. The efficiency of electric furnace is 70%, which means that the primary energy consumption is 173.2kg of standard coal.
Domestic and foreign foundries consume 590 kW/h/t, or 189.39 kgce, which means that the energy consumption of cast iron melted in electric furnace is 35% higher than that of cupola.Now there are more scrap steel. In order to reduce costs, foundries have turned to the use of synthetic cast iron to produce cast iron parts.Due to the high melting point of waste steel, more energy is required.Table 2 shows the statistics of energy consumption of hot air cupola for melting synthetic cast iron, which is smaller than that of cold air cupola.
Another advantage of the cupola is its low production cost.Many of our small foundries are reluctant to give up cupola smelting because of its low smelting costs.Figure 1 is a comparison of the cost of cupola and induction furnace smelting.At the same productivity, the production cost of a hot air cupola is only 73% of that of an electric furnace.The results of the calculations will differ depending on the conditions.When a domestic enterprise chooses the 30 t/h smelting system, when using hot air cupola, the production cost can be reduced by 14% compared with using electric furnace, and the investment of cupola can be recovered within one and a half years.
Cupola is continuous production, its feeding is inconvenient, in addition, it is suitable for mass production, if only a few hours per day, the production cost will increase.Electric furnaces are flexible in that they can charge each furnace and the production time has less effect on the production cost than the cupola.
The different characteristics of the two types of furnaces determine their different application occasions, especially in relation to the scale of the enterprise, i.e. production capacity and varieties.There is a consensus in the industry that if the cast iron is produced with a single brand, a large production volume, a continuous working day of 16 hours and an hourly iron demand of more than 10 t, hot air cupola should be considered as the primary smelting equipment first; if there are many types of cast iron and the amount is not large, only 5 or 6 tons per hour and only 8 hours per shift per day, then the smelting equipment should be selected.Induction furnaces are preferred.
If we pay attention to the operation of foundries in the world, it is not difficult to find that all foundries with annual production of over 100,000 t cast iron are basically smelted in large cupolas.A foundry that only produces brake discs uses a 67 t/h cupola; a foundry that produces the body of the car engine uses an 80 t/h cupola; and an enterprise that only produces castings for the car chassis uses a 90 t/h cupola.With the same amount of liquid iron produced, the number of cupolas is becoming smaller and the capacity of cupolas is becoming larger and larger.