Molten slag pours on to a rotary disc during CSIRO’s dry granulation process.

Cutting steelmakers GHG

In response to climate change, CSIRO is working with Australian steel manufacturers BlueScope and OneSteel on two significant projects aimed at delivering deep cuts in net greenhouse gas emissions associated with the steel making process. (8:17)

  • 29 July 2011

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Read more about Dry granulation - a new sustainable process for full value recovery from molten slags.

Transcript

Glen Paul: G’day, and welcome to CSIROpod. I’m Glen Paul. Steel and iron are commodities that have no effective substitutes – they’re essential elements for world growth and development. Across the globe the steel industry produces 1400 million tonnes of steel annually, and from that comes just over 2000 million tonnes of greenhouse gas. Of that greenhouse gas, Australia’s steel industry contributes 14 million tonnes.

In an effort to reduce that amount, CSIRO is working with Australia’s two steel makers, Bluescope and OneSteel, on two significant projects which aim to lessen the carbon emissions associated with the steel making process. The research is focusing on two areas, which if successful could result in more than halving the greenhouse gas emissions from steel making.

Joining me on the line to discuss the projects is Dr Sharif Jahanshahi from CSIRO’s Minerals Down Under National Research Flagship. Firstly Sharif, how significant is our 14 million tonnes against the 2200 million tonnes of greenhouse gas produced globally in the manufacture of steel?

Dr Jahanshahi: 14 million tonnes is not a small amount, and compared to Australian total emission it’s quite significant – we emit over 200 million tonnes of CO2. But from the metallurgical sector, that’s iron and steel, it is one of the highest in Australia, and the tonnage there they’d be talking about represents about one per cent of the global production of steel.

So in that respect it’s significant from Australia, but we should also remember that we also export large tonnage, hundreds of millions of tonnes of iron ore and coal for the international steel industry, and the emission associated with those sort of run into also hundreds of millions of tonnes.

So the technologies we’re looking at is aiming at reducing the overall emission by the steel industry around the world.

Glen Paul: OK. Let’s have a look at the biomass research firstly. What does that involve?

Dr Jahanshahi: This involves partial replacement of coal with renewable carbon or charcoal, which is dried by pyrolysis of biomass materials. These biomass materials are sourced from plantation of trees and residues from forestry, agriculture, and wood processing industries. 

These materials are sourced from sustainable sources rather than native forests, thus we consider them to be carbon neutral. And it is worth noting that the pyrolysis process that CSIRO is developing for conversion of the biomass to charcoal also produces some very valuable by-products, such as bio oil and hydrocarbons, which could be used for other applications such as producing green electricity, plastics, and liquid fuels, which obviously would be considered as carbon neutral as well.

Glen Paul: Right. So would you need to burn more of this to generate the same amount of heat as you would in burning coal?

Dr Jahanshahi: Mass and energy balance modelling shows that because charcoals contain less amount of gangue materials or impurities, the amount required to replace the coal would be slightly less in fact, much more efficient in that regard. And as they also combust much more efficiently than coal, then some further efficiency and improvements there is expected to happen once we replace some of the pulverised coal injection with charcoal.

Glen Paul: OK. What about the actual noxious gas emissions that are generated through the metallurgical processes themselves?  Will there be more or less of that using biomass derived charcoal?

Dr Jahanshahi: Yeah, our measurements to date have shown these are a part of plant results, particularly in sintering of iron ore, that because charcoals contain less impurities, such as sulphur, the emissions of oxides of sulphur and nitrogen are considerably less than when we use coal for the same sort of sintering application. So we expect significant improvements also in that regard arising from the use of charcoal.

Glen Paul: OK. So let’s turn our attention now to the other area of research in reducing greenhouse gas emissions in dry slag granulation, which relates to molten slag, which as we know is a by-product of steel making. But it’s in the cooling process where this dry slag granulation differs. Can you explain that for us?

Dr Jahanshahi: In this process we are aiming to recover the heat from the molten slag by-product, which is produced during smelting of iron ore. Currently all of this heat is lost to the atmosphere, and the intention is to recover this very high grade heat there by first breaking up the molten material into droplets, by contacting it with a spinning disc, and then each droplet will be then contacting air and passing its thermal energy to the air. It’s producing a high grade heat source there which could be used for a variety of applications around the plant, such as electricity generation, or preheating material.

The interesting second feature of this process is that because the slag is coold very quickly, and it’s got glassy and some surreptitious properties, it can be used as a substitute for Portland cement. And hence here we’re converting a base by-product into quite a useful saleable product which usually each tonne of Portland cement results in production of one tonne of CO2. So in Australia where we produce two million tonnes of such slags, you can expect that some few million tonnes of CO2 being saved through application of this process.

Glen Paul: Hmm, and that is a sizeable amount of CO2, and I guess you’re using the particles produced from this process from the slag as a substitute for limestone in the Portland cement?

Dr Jahanshahi: Yes. To some extent its limestone, plus other materials which are added to the cement kiln, so that the limestone you could say is being replaced as well as some of the silica and other materials there.

The other advantage of this process is that because it’s dry and does not use water for granulation process, it saves huge amounts of fresh water for conversion of the slag into the granulate products. And again it’s got good environmental credentials coming with it when it’s commercialised.

Glen Paul: OK. Now, with Australia producing only about one per cent of the world’s steel it would make sense that we share this technology with the rest of the world. Is there a plan in place for that?

Dr Jahanshahi: Yes, there is. Our vision has been from the beginning to share these technologies, both of them, with the rest of the world, and the strategy has been to engage the international steel industry through the World Steel Association. Most of the work that we have carried out has been exposed to the World Steel CO2 breakthrough program, and they have not only endorsed these projects as being breakthrough in nature, but also see them as technologies which could be implemented in the next five to seven years, or five to seven years after the demonstration through the full scale plant trials in Australia.

So we were quite excited again about being able to influence the international scene and reduce the overall greenhouse gas emissions from the steel industry.

Glen Paul: Well, we’re all in it together, so it certainly makes sense that we do that. Thank you very much for talking to me about the research today, Sharif.

Dr Jahanshahi: Thanks, Glen.

Glen Paul: Dr. Sharif Jahanshahi. For more information find us online at csiro.au. You can like us on Facebook, or follow us on Twitter at CSIROnews.