Increased scrutiny over greenhouse gas emissions in iron and steel production have prompted all parties involved in its value chain to invest significant resources into reducing their carbon footprint. ROBERT HOBSON reports
Miners, in particular, view their carbon footprint as a risk to their social licence to operate despite the bulk of the carbon emissions weighted on the manufacturing end of process.
This poses a challenging situation for the Australia resources industry as, according to CSIRO research scientist Keith Vining, the heavy industries which turn iron ore into iron and steel are largely located overseas.
Steel making is carbon-intensive
"The majority of the work and the carbon-intensity is in the steel making process at the other end of the chain in Asia, for example in China, Japan and South Korea," he said.
"It's difficult for us to influence what goes on there and the energy used is significantly higher in the smelting process than it is in the mining process."
The main source of carbon emissions comes from the use of metallurgical coal as fuel or coke to melt the waste material – also known as gangue – from the ore to extract the iron.
Opportunities for miners to limit emissions
Downstream, however, Vining said miners could contribute to limiting the emissions at the other end of the value chain by essentially improving the quality of the ore before it is shipped to the smelters through the processes of drying, beneficiation, agglomeration and pre-reduction.
"One of the biggest emitters of carbon in the iron making value chain is the use of metallurgical coke in the blast furnace, and the simplest way we can influence how that is reduced is by upgrading the material prior to shipping it overseas," he said.
"In order to beneficiate any kind of ore, regardless of what it is, you need to do some sort of size reduction – crushing and grinding – so you can liberate the good stuff from the bad and effect the separation,"
"However, in doing that you negatively affect the size distribution of the material and it becomes problematic for the consumer,"
Separating waste material before processing to steel
"The iron ore agglomerates, can then be charged into a blast furnace along with the metallurgical coke to separate the metal from the gangue avoiding the sintering process." Vining said.
As there is less waste material to melt, there would also be less metallurgical coke needed in the furnace per tonne of iron metal.
He also points out that another way in which beneficiation and agglomeration can reduce carbon in the value chain is in the transportation of the materials.
"It is important to remember the scale of the mining operations because you're talking about hundreds of millions of tonnes of material being transported from Australia to Asia," Vining said.
"In a wet tonne of iron ore, more than 50 per cent may be comprised of water, oxygen and gangue content, which is a significant amount of 'packaging' for the product."
Onshore processing iron-ore before export
He believes water and gangue removal is something Australian iron ore producers can do onshore to lower the carbon intensity associated with out iron ore exports.
Also, a higher quality ore would impart a further economic benefit to iron ore producers through their products commanding higher prices as well as spurring jobs growth in this part of the iron and steel value chain.
Although doing this may increase Australia's carbon emissions in the near term, Vining said it was important to take into account the bigger picture, which is the overall carbon-reduction in iron and steel making process.
Japan uses hydrogen in blast furnace to decrease emissions
For example, Japan's COURSE 50 program– the world's third largest steel producer – is actively researching the reduction of carbon intensity in its iron and steel industry by introducing hydrogen into the blast furnace.
It won't entirely replace metallurgical coke but rather reduce the reliance on metallurgical coke which, according to the COURSE 50 website, will generate water as opposed to carbon dioxide emissions.
The program also goes a step further to develop 'chemical absorption' technologies which aim to capture carbon dioxide from blast furnace gasses.
"They're still using metallurgical coal or coke, and that's to maintain the permeability of the blast furnace," Vining said.
"And this is because the coke does a couple of things – it's very, very stable at very high temperatures and it maintains the integrity and permeability of the blast furnace burden,"
"So, it performs a physical function and you need that material in there. But the concept is to introduce more hydrogen to limit the carbon they need to use and to capture what carbon they do produce."
Again, it is at the 'bigger picture' level where the cumulative effect of these types of carbon reduction measures can be seen.
It also raises the possibility of the iron and steel value chain going that step further to produce 'green steel', particularly if hydrogen can be harnessed in its manufacture.
Despite some of the technical and commercialisation challenges faced by a latent hydrogen industry, Vining believes it is a promising, albeit a longer-term goal.
"It opens up a pathway to asking, 'Well, if we have gone this far in the process, should Australia be making its own iron and steel?', and that’s a much bigger challenge because that will be a structural change in the way iron and steel is made," he said.
"The blast furnace has been refined over centuries and it is an extraordinarily efficient process. But, of course, it uses carbon,"
"If you want a process that can compete with blast furnaces in terms of efficiency and productivity, you have got to produce the hydrogen in a competitive way."
Renewable options for powering beneficiation processes
Vining suggests that pairing up renewable energy sources like solar and wind farms with beneficiation and agglomeration activity can spur iron ore producers to consider further opportunities to reduce their downstream carbon footprint in the short term.
"There might be a bit of reluctance from iron ore producers to start doing these sorts of things in the absence renewable energy," he said.
"But everything changes with the availability of renewable energy to power beneficiation and agglomeration processes. Cheap renewable energy can really change the landscape,"
"I believe (hydrogen) is a long-term solution, but beneficiation and agglomeration using conventional renewable energy sources is something we can do right now."