ENERGIRON technology: DRI-EAF production route using natural gas or H2

The DRI-EAF route consists in the direct reduction of iron ore in shaft furnaces followed by melting of the Direct reduced Iron (DRI, cold or hot) or hot briquetted iron (HBI) in electric arc furnaces. The ENERGIRON technology which is using a vertical shaft furnace to reduce iron ore pellets into DRI, has been developed by Tenova and Danieli, and constitute one of the main technologies available worldwide for DRI production.

TECHNICAL DESCRIPTION
The so-called ZR (Zero Reformer) process is the most advanced version of the ENERGIRON technology which enables the reduction of iron ore pellets / lump ores (or mixtures of both) in a shaft furnace without the need for an external gas reforming equipment. In this process, reducing gases are generated in situ inside the reduction reactor. Several options are available for generating the reducing gases depending on local conditions, including:

• Direct in situ reforming of natural gas, in this case, natural gas is fed directly as make-up gas through the reducing gas circuit;
• Using an external natural gas / steam reformer;
• Using syngas obtained from gasification of fossil fuels / biomass;
• Using coke oven gas;
• Using hydrogen.

Inside the shaft furnace, the hot reducing gas is fed to the reduction zone and flows upward counter-current to the iron ore moving bed. The exhaust reducing top gas leaves the reactor at about 400 °C and passes through a heat recuperator, where its energy is recovered to produce steam or to preheat the reducing gas stream. The water produced during the reduction process is condensed and removed from the gas stream. The scrubbed gas is passed through a process gas compressor where its pressure is increased.
After the compressor, the gas is sent to a CO2 removal system which constitutes a unique feature of the ENERGIRON process. It consists of an amine absorption system combined with a stripper. Overall, the CO2 removal system leads to the sequestration of about 256 kg CO2 / t DRI, which can be sold and used as by-products by different off-takers (e.g. food and beverage industry, dry ice, enhanced oil recovery).

DEGREE OF MATURITY

Natural gas-based direct reduction:
Direct reduction plants operating with natural gas are fully commercially available and widely deployed with many installations around the world. DRI plants using the ENERGIRON process in operation worldwide have a total DRI production of 15.6 Mt in 2024.

H2-based direct reduction:
The technology readiness level is 7/8 for the use of 100% H2 in direct reduction plants, but this is expected to rise to TRL 9 in the period 2026 / 2030 when full-scale hydrogen integration projects will materialise.

Energiron plants already use large amounts of hydrogen in gas entering the shaft furnace (i.e. 70% H2 Content) and as such can accommodate additional hydrogen produced from electrolysers without process modifications.

Successful tests were carried out already during the 1990’s by Tenova at a DRI pilot plant with a production capacity of 36 tons of DRI / day situated in Mexico (Hylsa, Monterrey) with > 90% H2 (vol.). This study gathered data for design and operation under such operating conditions that are directly applicable to any existing and/or new ENERGIRON direct reduction plant. These tests also showed that using 70% H2 as energy input (about 88 % at the inlet of the furnace), the expected carbon content in the DRI was about 1.8 %.

CROSS-MEDIA EFFECTS
The electric power consumption in EAF steelmaking increases when increasing amounts of DRI are used in the furnace (in substitution for steel scrap). Typically, every increase of 10 % in DRI leads to an increase in electric power consumption of about 14.5 kWh/ton of liquid steel .
Adequate process safety management shall be implemented from the design to the operation of DRI plants both using natural gas as well as high proportions of H2.

BARRIERS TO IMPLEMENTATION
Key challenges to overcome include the availability and cost of green hydrogen, infrastructure development and the integration with existing steelmaking facilities.

Basic information about the technique

Participant Companies