Cupola is a melting furnace commonly used for cast iron production. It uses bare metals like iron scrap or return iron and cast metal coke with a large grain size as fuel. Most of cupolas are hot-blast cupolas, in which exhaust gas is introduced into a heat exchanger and the air preheated to a temperature of 500°C is sent. In cupola operation, the coke rate (coke charge rate / iron source charge rate) can be decreased by increasing the blast temperature. In recent years, a high-temperature air blasting at 600 - 800°C is realized by a heat exchanger for air-blowing and preheating, which uses ceramic pellets with 1 - 2mm diameter grain size as the heat medium.

In addition to hot-blast cupola, 2-stage tuyere cold blast cupola, plasma cupola, and a cupola using natural gas other than coke have been developed. In recent years, use of cupolas that are partially fueled on coal dust and waste plastic and having furnaces equipped with an oxygen enriching device for liquid temperature control are being used. These cupolas reduce coke consumption and improve material quality, as well as reducing production costs and energy demand. At the same time, a high-efficiency cupola has been developed, which allows the high-efficiency, low-coke operation by combining partitioned charging of material and fuel and multi-stage air blowing while using cheap fine-grain coke (NEDO, 2008. p. 97)