Minimise risk of stranded assets in steelmaking transformation

The transformation of the steelmaking industry towards fossil-free steel production generates risk of stranded assets. This will have an impact on the industry and potential costs of transformation, but there are strategies that can be implemented to minimise these risks. In this blog post, we present a three-step process that could be implemented.

Executing the transition to minimise the risk of stranded assets

Several transformation scenarios could be considered that allows for minimum production interference with secure iron feedstock supplies during a step-wise migration towards a fossil-free ironmaking production.

The exact configuration and processing design of the different tiers are strongly dependent on the local conditions such as the configuration of the existing plant, availability of energy and scrap, planned lifetime of existing equipment, etc.

Below follows a scenario to trigger the thought process and highlight potential solutions when a tiered migration over a long period allows for a smooth transition and minimises stranded assets.

Point of departure

The point of departure is the existing production set-up, in this case, a Blast Furnace (BF) for iron production, torpedo cars for transfer of liquid pig iron to the steel plant, where the steelmaking operations consist of a single line of Basic Oxygen Furnace (BOF) converter, a Ladle Furnace (LF) and a Continuous Casting Machine (CCM), figure 1.
Figure 1: Point of departure. A standard single line integrated BF-BOF steel plant.

Step 1 – Introducing EAF steelmaking and granulation of pig iron

The initial step of migration towards fossil-free steelmaking is the introduction of an EAF and a pig iron granulation unit (figure 2). This serves several purposes:

• Getting acquainted with the EAF operations is important to later have a trouble-free ramp-up that gradually introduces more sophisticated steel grades.
• Pig iron granulation secures 100% iron yield from the BF and a full BF production pace without constraints from the steelmaking that causes unexpected shut-downs, idling periods, or pig iron discarding.
• The Granulated Pig Iron (GPI) feedstock has a format suitable for feeding into the EAF (similar to DRI feeding) or to be used in any other metallurgical process (like BF or BOF).
• GPI feedstock secures critical steelmaking carbon levels which remedies initial challenges in a low-carbon steelmaking scenario.
• If downstream capacity allows, there is a possibility to increase production rate during this period, making use of all BF iron produced in combination with merchant scrap.

During this period the BOF and EAF units will have relatively low utilisation, but the set-up allows for a smooth transition as more and more steel shift processes route from BOF to EAF.Figure 2: Step 1 – Introducing EAF steelmaking and granulation of pig iron.

Step 2 – 100% EAF steelmaking based on scrap, DRI/HBI, and GPI

Step 2 should be introduced when the EAF processing has stabilised, and all steel grades in the product portfolio have successfully been processed via the EAF route (figure 3):

• A dual EAF set-up is in place to accommodate the total steelmaking volume.
• DRI/HBI is used as the primary iron feedstock together with merchant scrap. 
• GPI is produced using the existing BF to make a high-carbon metal feed available and keep the BF operational.
• The BOF is on standby as a backup to handle unforeseen situations.

The DRI/HBI can be imported from different locations globally, sourced from an internal remote site, or produced on-site. The DR-process operates either on natural gas, a natural gas/Hydrogen mix, or 100% Hydrogen.

The BOF-GPI production line may operate independently to produce merchant GPI to maximise the BF lifetime, or to supply GPI to other production sites in need of carbon-bearing iron.

Figure 3: Step 2 – 100% EAF steelmaking based on scrap, DRI/HBI, and GPI.

Step 3 – Complete migration to fossil-free steelmaking

As production using the new technologies implemented stabilises, the BF, BOF, and granulation units are decommissioned (figure 4).

The iron feedstock is now dominated by scrap and DRI/HBI. GPI is only used as a complement for carbonising the metal or when required in exceptional processing cases, and is sourced externally (or within the group).

To reach a truly fossil-free operation, the HBI/DRI is produced using green Hydrogen.

Figure 4: Step 3 – fossil-free steelmaking set-up.

Conclusion

Iron- and steelmaking decarbonisation requires major considerations on a strategic level. Obtaining a smooth transition towards fossil-free production is only possible with a well-designed plan, preferably tiered in several steps with lengthy periods operating at an intermediate set-up. This wp-contentroach will minimise risk considerably by securing processing, productivity, iron feedstock, energy availability, equipment set-up, and product quality.

It will also minimise the risk of stranded assets in steelmaking.

If you want to read more about strategies for moving towards a fossil-free steelmaking process you can download our guide here.

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