(1) It is an inevitable trend to popularize the use of hot air, water-cooling, continuous operation and long service life cupola to the direction of large-scale, long-term continuous operation.
Foreign foundry enterprises use it as an important energy-saving measure. In recent years, a lot of work has been done in this field in China, and some enterprises have adopted it, which has achieved obvious energy-saving effect. For example, the adoption of large row distance double layer blast cupola technology can save 20% – 30% of coke, reduce 5% of scrap rate, and reduce 5% – 10% of Si and Mn burning loss respectively; the water-cooled cupola without furnace lining and thin furnace lining has a long continuous operation time, which can save more than 30% of energy; the hot blast cupola is both energy-saving and environmental protection.
(2) Strengthen the energy saving and consumption reduction of heat treatment process in foundry
The main equipment of heat treatment process in foundry is resistance furnace. Resistance furnace mainly generates heat energy through the resistance heater of resistance furnace, and transfers heat to the upper part at the same time, so that the temperature of the upper part quickly rises to the predetermined temperature. Therefore, the main way to save energy is to strengthen the heat preservation, improve the heating efficiency of the resistance heater and reduce the heat loss of the resistance furnace. It has been proved by practice that the thermal efficiency of the resistance furnace is only about 25% before the transformation, but after the transformation, the thermal efficiency can be doubled to 40% – 50%. There are two specific methods. First, the furnace wall is pasted with ceramic fiber felt, and the furnace wall is built with light insulating bricks to reflect the heat, so as to prevent heat loss. Second, the resistance belt can be used instead of the resistance wire and coated with infrared paint, which can not only protect the resistance belt, but also enhance radiation and heat transfer.
(3) Do well in structural adjustment and optimization, and change the mode of economic growth
Do well in the adjustment of industrial structure. We should take the adjustment of property rights and ownership as an opportunity to adjust and optimize the industrial structure. According to the principle of “four same” (same size, wall thickness, material quality and complexity) or according to the classification of casting method, the basis of specialized economic energy consumption can be realized through reorganization and merger.
Adjust and optimize the energy consumption structure. At present, the heating furnaces in China’s foundry industry are mainly coal-fired, with low energy utilization rate and difficult to control process parameters. It is difficult to meet the process requirements of heat treatment of alloy steel castings and ductile iron castings, and it also pollutes the atmosphere, which is not conducive to environmental protection. Therefore, the electric furnace, natural gas furnace and oil furnace can be used properly, which not only improves the quality of castings, but also reduces the environmental pollution, and improves the utilization rate of energy.
(4) Promote comprehensive utilization of cupola waste gas and waste heat recovery technology to realize clean production and energy saving
At present, 90% of China’s cast iron is produced by cupola melting, which will continue for quite a long time. The waste heat utilization of foundry industry is mainly concentrated on Cupola. A large amount of smoke is discharged from cupola smelting, which contains combustible carbon particles and combustible gases, which not only causes environmental pollution, but also wastes a lot of heat energy. In addition to 38% ~ 43% of the effective heat used in cupola smelting, the heat taken away by flue gas is 7% ~ 16%, the heat of incomplete combustion (combustible gas) is 20% ~ 25%, and the heat of incomplete combustion of solid is 3% ~ 5%. These heat accounts for 30% – 45%. It can be seen that the waste heat of cupola smelting has great potential. It can not only save energy and improve the quality of molten iron, but also meet the requirements of environmental protection.
