In recent years, Chinese electric arc furnace (EAF) steelmaking enterprises have been actively exploring and implementing various intensified smelting process technologies and equipment. These efforts have led to remarkable progress in enhancing production efficiency, reducing smelting power consumption, and recovering secondary energy. The energy - saving technologies in the EAF steelmaking process mainly encompass the following key aspects:
One crucial approach is to improve the input electric power and the efficiency of electricity consumption for each ton of steel produced. This can be achieved through the adoption of advanced furnace types and power - related optimizations. For instance, ultra - high - power electric furnaces are employed to deliver a higher power input, enabling faster melting and increased production rates. Direct current (DC) electric furnaces offer advantages such as lower electrode consumption and more stable arc operation compared to traditional alternating current (AC) furnaces. High - impedance or variable - impedance AC electric furnaces can also be used to optimize the electrical characteristics of the smelting process.
In addition to selecting appropriate furnace types, optimizing the power supply system and short - network structure of the electric furnace is essential. Conducting cross - arms can improve the electrical conductivity and reduce power losses. Long - arc operation is another effective technique that helps to increase the energy transfer efficiency from the arc to the scrap. Moreover, safety and longevity bottom - blowing technology can enhance the mixing of the molten bath, promoting more uniform heating and melting, thereby improving overall energy utilization.
Another significant aspect is to introduce additional physical and chemical heat sources into the EAF steelmaking process. Heating molten iron before introducing it into the furnace can provide extra thermal energy, reducing the power required for melting. Scrap preheating is also a widely used method. By preheating the scrap, the initial temperature of the charge is increased, which shortens the melting time and lowers power consumption.
Technologies such as the furnace door carbon - oxygen lance, furnace wall carbon - oxygen - combustion composite cluster lance, and bottom - blowing oxygen technology are employed to generate chemical heat within the furnace. The carbon - oxygen reaction produces a large amount of heat, which contributes to the melting of the scrap and the heating of the molten bath. These techniques not only increase the heat input but also improve the kinetics of the smelting process, leading to faster reaction rates and better process control.
Optimizing operation technology is vital for achieving intensified smelting and energy saving. Eccentric bottom tapping (EBT) is a well - known technology that allows for more precise control of the tapping process, reducing the amount of slag carried over into the ladle and improving the quality of the molten steel. A mechanized feeding system and continuous feeding method can ensure a more stable and continuous supply of raw materials to the furnace, maintaining a consistent melting rate and reducing power fluctuations.
Rapid temperature measurement and sampling analysis techniques enable real - time monitoring of the molten bath conditions. This allows operators to make timely adjustments to the process parameters, such as power input, oxygen blowing rate, and raw material addition, to optimize the smelting process and minimize energy waste.
The recovery of flue gas waste heat is an important measure for energy saving in EAF steelmaking. The high - temperature flue gas generated during the smelting process contains a large amount of sensible heat. By using waste heat recovery devices, this heat can be converted into useful energy. For example, the waste heat can be used to generate steam, which can be supplied to the vacuum refining device in the workshop for various heating and processing operations. Alternatively, the generated steam can be connected to the grid for power generation, providing an additional source of electrical energy.
Currently, most electric furnaces that use the hot molten iron process are equipped with flue gas waste heat recovery devices. Moreover, China has successfully developed complete waste heat recovery devices for electric furnace flue gas and carried out engineering demonstrations, further promoting the widespread application of this energy - saving technology in the EAF steelmaking industry.
In conclusion, by focusing on these main aspects of intensified smelting and process energy saving, Chinese electric arc furnace steelmaking enterprises can continuously improve their production efficiency, reduce energy consumption, and enhance their competitiveness in the global market.
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