Learn more about eaf steelmaking technology development

Arc furnace steelmaking technology development

1. Cleaning

Scrap crushing and sorting technology The resource utilization of scrap steel plays an important role in the energy saving, emission reduction, transformation and upgrading of the iron and steel industry. With the increasing number of scrapped automobiles, electromechanical appliances, and home appliances, the scrap metal components recycled by society are more mixed, including ferrous metals, non-ferrous metals, and non-metals. Efficient crushing and sorting of scrap steel is the premise and key to ensure the quality of EAF steelmaking raw materials, and it is very important for EAF steelmaking to achieve clean smelting. The scrap steel after crushing and sorting can greatly improve the cleanliness of raw materials, and provide clean and reliable raw material guarantee for electric arc furnace steelmaking.

(1) EAF steelmaking safety and longevity bottom blowing stirring technology

The metallurgical reaction kinetics of the molten pool of electric arc furnace steelmaking is poor, the composition and temperature of molten steel in the molten pool are not uniform, and the oxygen content at the end point and the content of iron oxide in the slag are high, which ultimately affects the smelting index and the quality of molten steel. The safety and longevity bottom blowing technology of electric arc furnace steelmaking developed by Beijing University of Science and Technology has strengthened the stirring of the electric arc furnace molten pool. The quality of molten steel at the end of smelting is improved significantly. At present, this technology has been applied in more than 20 electric arc furnaces at home and abroad, and the life of the bottom blowing element exceeds 800 heats, realizing the synchronization of the bottom blowing life and the furnace age of the electric arc furnace.

(2) Electric arc furnace steelmaking composite blowing technology

Aiming at high efficiency, low consumption, energy saving, and high-quality production, the new generation of electric arc furnace smelting technology proposed and developed by Beijing University of Science and Technology - "Electric Arc Furnace Steelmaking Composite Blowing Technology", uses cluster oxygen supply, synchronous longevity bottom blowing and stirring, etc. With technology as the core, the operation integration of electric arc furnace steelmaking power supply, oxygen supply and bottom blowing has been realized, meeting the technical requirements of EAF steelmaking composite blowing under the condition of multiple charge materials. At present, the overall and unit technology of the project has been applied in more than 100 domestic electric furnace factories, and exported to Italy, Russia, South Korea, Iran and other countries. After the application of 50-150t electric arc furnaces in Tianjin Steel Pipe, Laiwu Steel, Hengyang Steel and other enterprises, the smelting power consumption has been reduced by 13kWh/t, the steel material consumption has been reduced by 15.5kg/t, and various technical and economic indicators have been significantly improved.

(3) Low-cost dephosphorization technology

The traditional electric arc furnace smelting low phosphorus steel usually adopts multiple slag making and slag flow operations, which has long smelting cycle, large slag amount, high final slag (FeO) content, serious molten steel overoxidation, and difficult to control the smelting cost.

Beijing University of Science and Technology has developed the electric arc furnace steelmaking buried oxygen supply injection technology, which moves the oxygen supply method from the top of the molten pool to below the molten steel level, and directly enters the oxygen into the molten pool, which speeds up the metallurgical reaction speed. The technology significantly improves the molten steel flow and chemical reaction speed, effectively controls the molten steel peroxidation, and improves the dephosphorization efficiency of the molten pool. On this basis, the oxygen-lime powder mixed injection dephosphorization process in the electric arc furnace steelmaking molten pool was developed, and the lime powder was directly injected into the steelmaking molten pool with oxygen, which realized the low cost, rapid and deep dephosphorization of electric arc furnace steelmaking. The consumption of lime per ton of steel is significantly improved, and the dephosphorization effect is remarkable.

(4) High-efficiency denitrification technology

On the basis of the bottom-blowing Ar stirring technology in the electric arc furnace, based on the physical and chemical properties of CO2 and the CO2 reaction mechanism in the high-temperature metallurgical molten pool, the Beijing University of Science and Technology has developed the CO2-Ar dynamic bottom-blowing denitrification technology in the electric arc furnace, which uses the strong denitrification characteristics of CO2 to strengthen the arc furnace. The nitrogen content of the molten steel at the end of the whole scrap smelting process is stably controlled below 45×10-6, and the quality of the molten steel is significantly improved.

2. Greening

(1) Scrap preheating technology

In the aspect of scrap preheating in EAF steelmaking, EAFs such as double shell, vertical and Consteel scrap preheating furnaces have been developed and applied successively. Double shell electric arc furnaces have been withdrawn from the market due to problems such as low waste heat efficiency, large equipment maintenance and pollutant emissions such as dioxins; vertical preheating electric arc furnaces are affected by the impact of blanking. Equipment reliability and other drawbacks are gradually withdrawing from the market. Consteel electric arc furnaces are widely used due to their good production environment, small grid impact, reliable and controllable feeding, and high utilization efficiency of flue gas waste heat. At present, the latest mainstream electric arc furnaces developed at home and abroad are mainly developed on the basis of the original scrap preheating electric arc furnaces.

(2) Waste heat recovery technology

At present, EAF waste heat recovery technologies mainly include Tenova iRecovery and MCC CCID's total waste heat recovery technologies. Tenova iRecovery flows pressurized water (150℃/5bar to 270℃/55bar) in the exhaust gas pipeline, and the water close to the boiling point absorbs the waste heat in the exhaust gas through evaporation, which can recover 35%-70% of the EAF steelmaking flue gas heat; the total waste heat recovery technology developed by MCC CCID and other enterprises adopts high temperature resistant and long life vaporization cooling flue, high efficiency flue gas combustion settling chamber and tubular waste heat boiler, etc., to realize the process smoke from the fourth hole of the electric arc furnace to the waste heat boiler The stable recovery of total gas waste heat and efficient dust removal solves the traditional problem of low utilization rate of waste heat, and the recovery rate of waste heat from EAF steelmaking flue gas is increased by more than 10%.

(3) Dioxin control technology

The reduction method of dioxin in electric arc furnace steelmaking is mainly reflected in the three aspects of dioxin formation source, formation process and exhaust gas purification. Relevant research focuses mainly on source inhibition and synthesis inhibition. Source suppression: through on-line detection and manual sorting, scrap steel is strictly sorted to minimize or even prevent scrap steel containing chlorine source materials from entering the furnace. In terms of synthesis inhibition: use furnace temperature control, rapid cooling, and catalyst/inhibitor addition to inhibit the regeneration of dioxins in electric arc furnace flue gas. How to achieve high-efficiency and low-cost dioxin control in the electric arc furnace steelmaking process will be the focus of the next research.

3. Intelligent

Electrode intelligent adjustment technology At present, there are many electric arc furnace electrode intelligent adjustment technologies. Among them, the new generation of intelligent electrode adjustment system developed by MCC CCID - DMI-AC, includes distributed collection of high-speed digital signals against strong electromagnetic interference - centralized Processing-network digital transmission system and multi-strategy, multi-constraint optimization flexible intelligent control system two core technologies, after Japan Steel Plantech general contractor Vietnam VKS company 90t electric arc furnace project adopts this technology, the electrode adjustment electrical response time is reduced to 60ms, The current fluctuation rates in the penetration period and melt-down period are <33% and <14%, respectively, which are better than the international advanced level.

On-line detection technology of smelting In recent years, with the development of science and technology, researchers at home and abroad have developed a series of detection technologies for the smelting process of electric arc furnace. The USTB non-contact molten steel temperature measurement system independently developed by our country, through the non-contact temperature measurement device installed on the furnace wall, uses multi-component temperature measurement gas injection to obtain the molten steel temperature characteristic signal, and establishes the molten steel temperature signal processing model, It can realize the measurement and prediction of molten pool temperature.

The self-developed USTB furnace gas analysis system can accurately measure the temperature, flow rate of the furnace gas and the components of each gas in the furnace gas, and use the collected information and its own control model to analyze, judge and control the smelting process.

Multifunctional furnace door robot: Facing the harsh environment, danger, heavy manual operation and precise process control of smelting in the electric arc furnace steelmaking area, a series of new technologies for automatic temperature measurement and sampling have been gradually developed and applied. Relevant domestic units are carrying out the research and development and promotion of multi-functional furnace door robots for electric arc furnaces. At present, most domestic electric arc furnace steelmaking enterprises still use the traditional manual sampling temperature measurement method. With the localization of advanced automatic temperature measurement and sampling devices, domestic electric arc furnace steelmaking has gradually adopted this technology.

Quality analysis monitoring and cost control system: With the development of electric arc furnace smelting technology, only relying on the operator's experience to control the production of electric arc furnace has been unable to adapt to the production rhythm of modern electric arc furnace steelmaking. Through the exchange of data information and process optimization control, the cost control and reasonable energy supply of the electric arc furnace steelmaking process can be optimized, which can also reduce costs and improve efficiency. However, the related systems introduced abroad are difficult to exert their effectiveness due to the complex raw material structure and special smelting process in China. The electric arc furnace steelmaking quality analysis monitoring and cost control system developed by Beijing University of Science and Technology can predict and calculate the cost of a single electric arc furnace in real time, and provide power supply and oxygen supply optimization guidance curves and optimization for different charge structures. Costs are forecasted and calculated in real time, and optimized alloy and slag combinations are provided. At present, the system has been popularized and applied in many electric furnaces at home and abroad.