However, it is understood that option was scrapped very early on in the process.

In an online forum on the blast furnace reline for Illawarra industry network i3net, the company's Head of Engineering and Capital Development Steve Shaw said a range of options were assessed before opting for the reline of the dormant No6 blast furnace.

Read more: Illawarra businesses getting ready to re-open

"We had a look at everything from the worst possible case for the region in shutting the front end of the business down and importing hot rod coil to relining No5 [the active blast furnace]," Mr Shaw said.

"We looked at the number of different technologies... most of the alternatives were far less attractive than relining No6."

Among the other options were different technologies to make iron - which is one of the ingredients needed to make steel. These included electric arc furnaces and the "direct reduced iron" process.

Mr Shaw said these options were not suitable as the technologies weren't "available on the scale that we require to keep our production levels and our market satisfied" in the near term.

The reline itself involves replacing the refractory bricks that line the inside of the 90-metre tall blast furnace - which is like a large bottle where raw material is constantly poured in at the top and molten iron extracted at the bottom.

Previously, this has required turning off the blast furnace and working around the clock for 50 days, because while the furnace is switched off it's not making iron.

However, this time BlueScope is in the fortunate position of having a spare blast furnace - No6 - at Port Kembla, That furnace was turned off in 2011 when the steel maker decided to leave the export market.

"Because we have No6 sitting there not operating, we can take a bit more time to do it and do it in a way which we believe is safer and more cost-effective than having a whole lot of people crammed into a small space doing work around the clock," Mr Shaw said.

The reline project is expected to cost around $800 million and is in the pre-feasibility stage, which is likely to be completed this year.

The BlueScope board will make a final decision to reline the furnace by the end of next year.

The timeline would have the revamped No6 blast furnace online by 2026, at which time it is expected No5 will be turned off.

BlueScope is holding a virtual town hall meeting on October 7 from 5pm to explain the details around the blast furnace reline.

For more information and to register, visit www.bluescopeillawarra.com.au

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