The Roles of DRI in Electric Arc Furnaces and Blast Furnaces
1. In Electric Arc Furnace (EAF)
In the process of analyzing the role of DRI in EAF metallurgy, it is necessary to analyze the effect of using DRI in EAF. After comprehensive analysis, the effectiveness of DRI in the production of high-quality steel in EAF is reflected in the following aspects:
1.1 The content of residual metals and harmful elements in EAF steel is relatively low. In the actual smelting process, the proportion of DRI as the raw material for EAF continues to increase, the amount of residual metals such as Cr, Ni, and Cu in the steel continues to decrease, and the content of harmful elements such as P and S also decreases to a certain extent. Comparing the specific changes in the metal content and harmful element content in steel, it can be found that because DRI itself does not contain residual metal elements such as Cr, Ni, Cu, etc., it can be effectively used as a raw material in the smelting process of high-quality steel in EAF. Its use effect is comparable to that of a converter. And because the continuous charging of DRI will produce a boiling effect, the N2 content is similar to the converter production level. In addition, because coated steel products are recycled multiple times during the smelting process, harmful impurities in the scrap steel will continue to increase, which can improve the smelting quality of EAF steel.
1.2 It can greatly shorten the EAF steelmaking time. As the proportion of DRI in the EAF charge continues to increase, the actual steelmaking time is greatly shortened. After comparison, it was found that when the proportion of DRI is increased from 30% to 90%, the steelmaking time will be shortened by about 10 minutes.
1.3 The application of DRI in EAF can reduce electricity consumption and increase the yield of EAF steelmaking. When the proportion of DRI is constant, the higher the metallization rate of DRI, the electricity consumption will tend to decrease, and the iron yield will continue to increase.
1.4 it can effectively improve and optimize the mechanical properties of steel. By applying DRI, it can be found that the yield strength, strain aging, formability, internal cleanliness, etc. of EAF steel have been improved. When the residual elements and N2 content are reduced, the yield strength of the C steel plate can be improved. Comparing 100% DRI with 100% scrap steel, the yield strength can be reduced by about 15%, improving the quality of EAF products. From this aspect of analysis, it can be determined that the use of DRI for EAF steelmaking can smelt high-quality steel. At this stage, the main role of DRI in the application of EAF at home and abroad is to improve the quality of smelted steel varieties and ensure that the smelted steel varieties can meet special purposes. For example, oil casings and drill pipes in the petroleum industry; deep-drawn automobile sheets used in the production process of the machinery industry; special-purpose steel wires and steel materials, such as bearings, steel wheels, generator rotors, gun barrels, aerospace, and atomic energy Steel materials used in industry, etc. An analysis of the comprehensive quality of DRI EAF smelting products found that full utilization of DRI can greatly improve the overall quality of EAF smelting products, which lays a good foundation for promoting the production of high-quality steel.
1.5 The use of hot charging DRI can achieve the purpose of energy saving and production increase. As the DRI hot charging temperature continues to increase, energy requirements show an overall downward trend, and the total energy savings are relatively large. Comparative analysis of energy changes found that when the hot charging temperature of DRI is 300 degrees Celsius, the energy contained in DRI and the energy required to melt gangue in DRI and reduce FeO can offset each other. The hot charging temperature of DRI continues to increase, and the productivity of EAF shows an upward trend.
1.6 The high carbon effect in DRI. High carbon DRI can improve the productivity of EAF and reduce steelmaking costs whether it is cold charging or hot charging. Mainly because the carbon content of high-carbon DRI is relatively high, which can increase the use of oxygen and improve the overall production efficiency. And in the application process of high-carbon DRI, the form of carbon is mainly iron carbide. As the carbon content continues to increase, the power consumption of the EAF will continue to decrease.
2. In Blast Furnace (BF)
Adding DRI to the BF can reduce the coke ratio of the BF and improve the overall productivity of the BF. The specific effect is as follows: if the proportion of DRI in the BF is 35%, the coke ratio can be reduced by about 21%, the slag amount can be reduced by about 10%, the melting loss reaction can be reduced by about 40%, and the BF smelting product can be improved by about 20% yield. In addition, the sensible heat required for preheating iron ore and coke is reduced by 10% and 21% respectively. In the early 1990s, this research result was confirmed by adding DRI to the BF of a Japanese steelmaking company in production practice. Adding less than 30% DRI to the BF raw material can reduce the coke ratio by more than 20%, and continuous IG can increase it by about 20%. At that time, Japanese steel mills added about 20% DRI and used about 9% oxygen during the BF smelting process. It was eventually discovered that the increasing oxygen enrichment rate could increase the fuel ratio to a certain extent and improve the efficiency of the BF.
