Energy Efficient DRI-EAF based Steel Production

by Ananya Mukhopadhyay, Marco Ometto

Publisher - Danieli India Technopolis, Danieli Automation SpA

Category - General Novel

DANIELI’s ENERGIRON DRI (Direct Reduced Iron) technology coupled with hot transport of DRI to the EAF (Electric Arc Furnace) is aimed to produce high carbon DRI at lower energy and reduced CO2 emission. While conventional blast furnace route of iron making is characterized by intensive use of coal, ENERGION DRI route allows the flexibility to use natural gas (for example, gas rich countries in South East Asia) and also the gas from other sources. Further, ENERGIRON ZR scheme capitalises on generation of reducing gas in-situ inside the reactor, and thereby eliminate the need for external reformer, resulting maximum utilization of supplied heat with minimum energy loss to atmosphere. Use of high carbon DRI at elevated temperature (continuous transport through HYTEMP tower) into the EAF needs less electrical energy for melting. Thus, ENERGIRON ZR scheme, producing high quality DRI (94% metallization, 4% carbon, and discharge temperature at 700 C) needs energy consumption of 2.25-2.30 GCal/t DRI and 60-80 kWh/t DRI as electrical power with iron ore consumption of 1.35-1.40 t/t DRI. The energy saving from hot charging (600 C) of 100% DRI in EAF at Emirates Steel, Abu Dhabi, reaches the new world benchmark of 141 KWh/t liquid steel. Such performance has been achieved through high level of process automation in DR Plant and Meltshop. Automation systems for control of Reactor and Reformer ensure process gas temperature for efficient reduction, and help maintain reformer gas temperature and composition uniform. EAF automation ensures stable operation through advanced electrode regulation, foamy slag practice, and use of optimum melting profile for minimum use of power. The use of off-gas analyzer can improve combustion efficiency and reduces use of chemical energy in EAF. Excess heat from the off-gas can be recovered through evaporative cooling for steam generation to drive the vacuum pump of steel degasser or co-generation of heat and power. All these measures to improve energy efficiency in DRI-EAF based steel production.

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