1 Introduction


Steel production can be divided into two processes: "from iron ore to steel" and "from scrap to steel". Compared with the conventional process represented by blast furnace converter in iron and steel complex, EAF steelmaking with scrap as the main raw material has the characteristics of less process, low investment and short construction cycle, so it is called short process. In recent years, the production of scrap steel resources in China has increased, the power conditions have improved, and the support of national policy guidance has created certain conditions for the development of EAF steel. However, there are still some restrictive factors for the development of EAF steel. First, the quality of scrap steel resources is uneven, second, the cost competitiveness of EAF steel is not strong, the price difference between scrap steel and molten iron can not support the cost competitiveness of EAF steel for a long time, and the overall domestic electricity price level is high, The price of graphite electrode is high and fluctuates greatly, which makes it difficult to control the cost of electric furnace steel. The requirements for emission indicators of iron and steel enterprises are becoming more and more strict. 80% of the pollutants discharged by iron and steel enterprises come from coking, sintering and other links. The disadvantages of long process steelmaking are becoming more and more obvious. The systematic comparison of the cost of EAF steel and converter steel, as well as the energy consumption and emission of long and short processes, is of great significance for the development of EAF steel enterprises.




2. New technology of EAF steel development

The new technologies of electric furnace steelmaking mainly include hot metal + scrap smelting technology, enhanced oxygen consumption technology, telescopic furnace cover electric furnace technology, new comste electric furnace steelmaking technology, new quantum electric furnace steelmaking technology, etc. The future development direction of electric furnace type is to realize continuous feeding, scrap preheating, green environmental protection, waste heat recovery and artificial intelligence steelmaking. At present, China's kangsidi electric furnace accounts for about 70% of the total number of electric furnaces. The electric furnace enterprises built earlier are generally ordinary electric furnaces with discontinuous charging.

2.1 electric furnace technology with telescopic furnace cover

In order to realize the one basket operation of electric furnace, German fox technology company has developed the telescopic furnace cover technology, which increases the height of furnace shell and the lifting stroke of furnace cover on the basis of ordinary electric furnace, which is conducive to shortening the non energization time and improving productivity. Operation effect: oxygen blowing per ton of steel is less than 30nm3 / T, and natural gas is 4 Nm3 / T; The power consumption is 369 kwh / T, the electrode consumption is 0.91 kg / T, and the feeding times of a basket of materials is increased from 40% to 54%.

2.2 new comste electric furnace steelmaking technology

The main features and advantages of the new comsti electric furnace: the installation position of the furnace body weighing device is changed from the four rollers under the tilting platform to the four corners above the tilting platform. The furnace body weight in the working state is measured according to the four weighing units. This method is convenient for installation and maintenance and has low failure rate; Shorten the length of scrap preheating section and increase the flue gas outlet temperature; Control the mixing of wild wind, strengthen the secondary combustion in the preheating section, ensure the outlet temperature at 800 ~ 900 ° C and inhibit the generation of dioxin; The bottom blowing device is set at the bottom of the electric furnace and at the bottom of the scrap blanking area to improve the temperature deviation of molten steel in the molten pool and shorten the smelting cycle; A baffle shall be set in the scrap preheating section to prevent the deviation of electrode center circle.

2.3 new quantum electric furnace steelmaking technology

Advantages of the new quantum electric arc furnace: the process is basically without power failure, the non power on time is 1 ~ 2 min, the productivity is high, and the smelting cycle can reach 33 ~ 36 min; The power utilization rate of transformer is high, about equal to 1, so as to reduce the matching of transformer power; The power consumption can reach 280 kwh / T (scrap preheating 600 ° C), and the electrode consumption can reach 0.9kg/t; Flat melting pool operation, voltage flicker, low noise level, can avoid the use of roof smoke hood; Energy saving, environmental protection and new. The structure of this new type of electric furnace is complex. Some foreign steel enterprises have put it into use, but no new quantum electric furnace has been put into operation in China.


3. Cost comparison data selection

According to relevant introduction, the power consumption of quantum electric furnace can reach 280 kwh / T and the electrode consumption can reach 0.9 kg / T.

(1) Electrode consumption.

The electrode consumption is related to the raw material structure, strengthened oxygen, scrap preheating and continuous feeding. At present, the electrode consumption of electric furnaces at home and abroad is 0.91 ~ 4.0 kg / T. when molten iron is added, the electrode consumption is lower than that of all scrap smelting electric furnaces.

For all scrap smelting, the electrode consumption is taken as 3 kg / T.

35% molten iron + 65% scrap steel, and the electrode consumption is 2 kg / T of the domestic advanced level.

50% molten iron + 50% scrap steel, and the electrode consumption is 1.8 kg / T of the domestic advanced level.

For quantum electric furnace, the electrode consumption is taken as 0.9 kg / T.

(2) Electrode price.

The price of graphite electrode is 105000 ~ 145000 yuan / T. the larger the electrode diameter, the higher the price. The electrode diameter of electric furnace steel enterprises is generally 400 ~ 550m, with 14 50000 yuan / T.

(3) Power consumption.

The power consumption of electric furnace steel depends on the raw material structure, equipment level, oxygen intensity, scrap preheating temperature, feeding mode and other factors. At present, the power consumption of electric furnaces at home and abroad is 200 ~ 480 kwh / T. adding some molten iron smelting has a significant effect in shortening the smelting cycle and reducing power consumption.

For all scrap smelting, the power consumption is calculated as 400 kwh / T.

35% molten iron + 65% scrap steel, and the power consumption is calculated based on the domestic advanced level of 250 kwh / T.

50% molten iron + 50% scrap steel, and the power consumption is calculated according to the domestic advanced level of 200kwh / T.

Quantum electric furnace, the power consumption is calculated as 280 kwh / T.