Electric furnace steelmaking technology 01

Electric arc furnace steelmaking

Focusing on the objectives of high production efficiency, simple function, environmental friendliness, intelligent control and diversified raw materials, electric furnace steelmaking technology has been continuously developed. The goal of high efficiency of electric furnace smelting is to shorten the smelting cycle and power on time as much as possible and reduce the smelting power consumption as much as possible. We should focus on the following six aspects: adopting the method of increasing the input power per ton of steel is reflected in the large-scale and higher power of equipment at the technical level; Improve the chemical heat of element oxidation in steel and the chemical heat provided by oxygen burner; Improve the sensible heat of scrap preheated by scrap; Improve electrical efficiency and power factor, such as rationalization of power supply system, adoption of intelligent electric arc furnace, optimization of short network structure, etc; Shorten hot shutdown time, such as scrap loading time, electrode connection time, tapping time, furnace repair time, etc; The production efficiency of a single variety of the whole production line is higher than that of multiple varieties.

The advanced furnace type is selected to achieve the purposes of full scrap preheating, continuous feeding, no cover opening, flat melting pool, low noise, less smoke and dust, trace dioxin, dust removal and ash recovery. In the process of technological development, electric furnaces have experienced different types of development, such as traditional open cover electric furnace, Fuchs electric furnace (vertical preheating of scrap), Consteel electric furnace (horizontal continuous charging), quantum electric furnace (quantum electric furnace), ecoarc electric furnace (environmental protection and ecological electric arc furnace), SHARC electric furnace (vertical shaft electric arc furnace), CISDI green electric furnace (CCID green intelligent electric furnace), ceri-s1-arc electric furnace (new scrap preheating electric furnace of MCC Jingcheng).

The advantages of traditional open cover electric furnace are less equipment failure, stability and reliability, but the disadvantages are that it can hardly achieve the above purpose and the production efficiency is low. In the 1990s, Fuchs electric furnace and Consteel electric furnace were introduced into China almost at the same time. Because of the high failure rate of Fuchs electric furnace equipment, it was basically eliminated under the background that the scrap cost could not be offset. After the domestic production of Consteel electric furnace equipment, under the background of "China to electricity", it has developed rapidly because of its advantages of high efficiency, low cost, stability and reliability. Before 2017, 95% of electric furnaces in China were of open top charging type; Since 2017, more than 85% of the new electric furnace equipment of the enterprise has been continuous horizontal feeding system. However, Consteel electric furnace also has obvious disadvantages, mainly that the design temperature of waste steel preheated by tail gas of horizontal flue is 400 ℃ ~ 600 ℃, and the waste steel temperature can only reach 200 ℃ ~ 300 ℃; The temperature of waste gas in the preheating scrap channel is in the peak range of furan and dioxin, so the pollution of harmful gas to the environment is difficult to solve; The amount of "wild wind" entering the preheating channel is large, which brings difficulties to dust removal and waste heat recovery.

Quantum electric furnace, ecoarc electric furnace and SHARC electric furnace hope to solve the above problems by preheating scrap through vertical flue. Quantum electric furnace replaces the basket feeding through the lifting trolley of scrap chute, adopts the siphon slag free tapping system, and still uses the finger system to maintain and preheat scrap, with high preheating temperature and less harmful gas. At present, there are 11 quantum electric furnaces put into operation and under construction in the world, including one in Mexico, one in Turkey, one in Bangladesh and eight in China. At the end of 2020, two quantum electric furnaces in China were put into operation, and the comprehensive effect remains to be observed. The main part of ecoarc electric furnace is composed of a melting chamber for melting waste steel and a preheating shaft furnace directly connected with the melting chamber. The furnace body sealing is combined with waste steel preheating. The operation of flat melting pool is highly automatic. The preheating temperature of waste steel can reach 800 ℃, which can avoid the generation of pollutants. The emission of dioxin is less than 0.1ng-teq/m3 (nanogram toxicity equivalent value per standard cubic meter, the same below). At present, there are 9 ecoarc electric furnaces put into operation and under construction, including 5 in Japan, 1 in South Korea, 1 in Thailand and 2 in China (under construction). SHARC electric furnaces are DC electric furnaces with low noise and dust. Double shafts are designed to preheat scrap steel with tail gas, and dioxin is less than 0.1ng-teq/m3. In terms of application, in addition to one 100 ton SHARC electric furnace in operation in Turkey, two 130 ton SHARC electric furnaces have been introduced from Hegang and Shijiazhuang steel. In short, the number of applications of these three electric furnaces is small, and the prospect remains to be further observed.