A green approach to iron-making
 |
Macquarie University scientists are working with the HIsmelt Corporation of the Rio Tinto Group to reduce the environmental impact of the global steel industry.
One of the unfortunate side-effects of traditional iron smelting is that mercury – which is present in tiny amounts in all coal - is released into the atmosphere where it oxidises and then is carried by rain into our lakes and rivers, eventually accumulating in fish and other biological life.
A new approach
But a new iron smelting technology developed by Rio Tinto at a cost of more than $600 million over the last 20 years may improve this situation. The HIsmelt technology allows iron ore fines and non-coking coals to be injected directly into a molten iron bath to produce moltenpig iron without the need to make coke and sinter.
“The processes by which coke and sinter are made are very environmentally unfriendly and unsustainable,” says Dr Vladimir Strezov of Macquarie’s Graduate School of the Environment. “Because HIsmelt uses direct reduction however, you don’t produce sinter or coke, so the company is advertising their technology as much cleaner than what’s currently out there in the market.”
Rio Tinto says HIsmelt technology will lower emissions of carbon dioxide and sulphur dioxide but are also keen to assess mercury emissions before licensing the technology around the world. This is where Strezov and his Macquarie colleagues Professor Peter Nelson and Dr Timothy Evans come in.
A mercurial question
Funded by an Australian Research Council Linkage grant totalling $420,000 over the next four years, the scientists will work with Rio Tinto to check how much mercury is released via the new method of iron smelting.
“In terms of mercury, Australian coal have much lower levels than many overseas coals,” explains Strezov. “In order to develop the new technique and introduce it to countries such as the United States which have coal with higher mercury levels and therefore more stringent regulations, it is very important for the company to prove that it’s much cleaner than what they already have there.
“We are not yet sure what’s happening with the mercury, but we expect that because the HIsmelt technology uses a desulphurisation unit – an air pollution control device whose main purpose is to use water droplets to take sulphur dioxide out of the air - that larger proportions of mercury will be trapped in that unit also.
“If some mercury is being released into the environment, we’ll look at what they can do to control that. The world still wants to make steel, so some emissions are unavoidable, but at least we can reduce them.”
For more information contact Dr Vladimir Strezov at vladimir.strezov@mq.edu.au or visit www.hismelt.com.au to find out more about Rio Tinto’s HIsmelt.