The life of iron

Materials World magazine
,
3 Mar 2011
A banded iron formation

Large iron ore deposits are continually being unearthed globally. Michael Forrest reports on the IOM3 Commodity Day dedicated to the ferrous mineral.

Steel is the bellwether of the global economy. It is of particular importance to those countries developing their infrastructure, with the largest consumer, China, accounting for 44% of the global steel market. It is against this background that Iron Ore Day held in January in London, UK, mapped the life cycle of iron ore – the foundation of steel making.

Exploration is the first stage in the cycle and iron ore has been a target for centuries. However, it is in the last 100 years that large-scale deposits have been discovered and exploited. Chris Wheatley, Senior Associate of minerals industry advisor Behre Dolbear International, Denver, USA, gave a global overview of the world’s iron ore deposits, putting into context the geological environment where they were formed. The tour started in the USA and Canada via South America, Africa, Australia, Asia and finally to northern Finland and Sweden. Deposits occur in all ages, but it is in the Archean (<2,500 million years) and Proterozoic that large scale deposits are prevalent.

‘The Algoma type deposits are associated with Archean greenstone belts interbedded with volcanic rocks in an island arc setting,’ explained Wheatley. ‘Continents probably accounted for less than 10% of the planet’s surface and oxygen was mainly consumed in ocean-crust alteration. Major crustal growth in the Proterozoic (2500-600Ma) was followed by widespread algal stromatolite formation as oxygen levels rose. At this time banded ironstone formations (BIFs) arose (classified as Lake Superior type), and form a major source of iron ore, from the Quadrillátero Ferrifero in Brazil to the Pilbara, Western Australia, where BIFs were enriched to provide ores of over 60% iron.’

Quoting mining company, Vale in Rio de Janeiro, Brazil, Wheatley believes that the easy discoveries are gone and that the new world-class deposits are increasingly dependent on Africa.

African discoveries

Core Mining, Isle of Man, UK, under the leadership of Socrates Vasiliades, is developing its Avima iron ore project in the Democratic Republic of the Congo (DRC). Avima is near the border with Cameroon and Gabon and is the focus of an exploration programme that already has identifed ore over 330m-thick iron ore grading 69.75%. This is direct shipping grade ore and will form the basis of the first production planned for 2015. The deposit occurs in a ridge over 30km in length, and the company is working on the centre section where it has an extensive drill programme, designed to define resources of the haematite/geothite mineralogy. An independent study by Coffey Mining Ltd, Brisbane, Australia, indicates a resource of 1-2bln tonnes of ore. Like all greenfield sites, a major challenge will be in rail links to ports and the world market.

In Liberia and the Cameroon, dual-listed (London and Toronto) African-Aura Mining Inc will be completing a pre-feasibilty study at its Liberian Putu project. Terms with the Liberian government have been ratified, while a 62,000m core drill project is due for completion this year. Putu is a 13km ridge of banded ironstone that contains haematite and magnetite horizons, the former grading around 55- 65% Fe up to 91m thick, while below fresh magnetite, up to 367m grading 40% Fe, has been encountered in one drill hole.

Initial investigation indicates favourable mineralogy with recoveries up to 95% and a concentrate grade up to 70%. The base investment case calls for a resource of 2bln tonnes to provide 20Mt/y of magnetite concentrate. Capital costs are estimated at US$2.5bln.

African-Aura Chief Executive, Luis da Silva, also illustrated its Nkout project in Cameroon where geophysical techniques have identified a 20km anomaly. Drill core to date show up to 75m of haematite and 195m of magnetite in banded ironstones.

‘These results indicate an emerging iron ore province with a number of other companies developing projects in neighbouring Gabon and DRC. A proposed rail route for these projects will likely pass through Cameroon and our project licences,’ declares da Silva.

 


Fines, slimes and furnaces

Steelmaking requires iron ore oxides (hematite and magnetite) to be reduced to their metallic state. Traditional blast furnaces require lump iron ore, metallurgical coke and fluxes. Grain size is important to allow air/ oxygen to flow through the furnace, while porosity is significant. In electric arc furnaces porosity is also important to ensure melting of ore/ scrap. However, fines are produced that reduce porosity and are consequently unusable.

According to Stuart Sneyd, Head of Direct Smelting and Reduction at Outotec GmbH, the company has developed a number of techniques that enable fines to be used in conventional and direct reduction plants. ‘Iron ore fines and slimes are a valuable commodity that can be upgraded from around 30%Fe to 64-66%Fe as sintered feed, 64-68% pellet feed for blast furnaces, and >68% Fe for direct reduction. We have designed a route for the treatment of fines that provides a pellet product that minimises the final waste slimes to particles of less than 15 microns’.

Sintering, pelletising, and direct reduction can also be applied to iron ore fines and steel plant dusts.

‘Outotec has developed a number of processing that will provide valuable feed to all steel plants that use increasingly finer grain sizes,’ informs Sneyd.

Chinese dominance

Roger Emmott, Global Head of Research & Consulting and Training at Steel Business Briefing (SBB), London, UK, reviewed the global iron ore trade and gave a great deal of attention to China.

‘It is the largest iron ore importer and the largest steelmaker. Chinese production is primarily by basic oxygen furnace (just under 600Mt/y) with around 50Mt/y by electric arc furnace, while the rest of the world in total struggles to meet the Chinese basic oxygen furnace (BOF) production. In electric arc production, China has only 20% of world totals. This accounts for the pre-eminence of China in seaborne trade that is dominated by three companies, Vale, Rio Tinto and BHP Billiton, as BOF is reliant on iron ore while electric arc furnaces (EAF) use a higher proportion of scrap.’

Looking to the future, SBB forecasts a continual growth on global steel production over the next decade of around 30%. Iron ore will grow at a slightly faster rate as China continues to expand its BOF capacity. Accordingly seaborne trade will also increase, modified by increasing scrap availability within China.

Price will also have an effect on the market, and Jean-Luc Fiorenzoni, Director, Stemcor Risk Management AG, London, UK, illustrated the complexity of modern steel trading.

‘The high spot prices seen over the past few years have effectively triggered the end of the iron ore traditional benchmarking pricing system that was negotiated annually with the “big three” producers. Today there are quarterly prices that might become monthly, as volatility is expected to be high for the foreseeable future and continues to create tensions between buyers and sellers,’ says Fiorenzoni.

All of these have impacted on traders who recognise the need for hedging against price fluctuations, for robust price indices, and mitigate concerns over counterparty credit risk. Some of these risks can be reduced by using a clearing house to provide a stable price platform. In partnership with Deutsche Bank, Stemcor has formed a strategic alliance to trade financial steel products.

European mines

Although Africa may be the new frontier, TSX and Oslo-listed Northland is developing iron ore mines in northern Scandinavia. CEO, Karl-Axel Waplan, outlined the advanced plans at the north Sweden Kaunisvaara deposit and the Hannukainen iron Oxide-Copper-Gold in Finland. ‘The company has completed a “definitive” feasibility study, gained a permit to produce from 2013, and hopes to ramp up production to 5Mt/y by 2015.’ Two open pits are being developed with a combined production of 12Mt/y from ores grading 26% Fe and 41% Fe that will require upgrading to concentrate,’ added Waplan.

Like all bulk commodity mines, transport is crucial, and Northland has chosen to truck the concentrate 150km to the Malmbanan railhead that links Svappavaara with the Norwegian ice-free port of Narvik. Narvik is also the destination of the Kiruna iron ore, and is uncongested and a deep water haven, some five days from Rotterdam and the European steel market.

‘We also have offtake agreements with Standard Bank, Tata Steel and steel-trader Stemcor that accounts for 5Mt/y of pellet feed,’ confirmed Waplan.

A road map for sustainable development in steelmaking was presented by Louis Brimacombe, Manager of the Environment Department at Tata Steel Research, Development & Technology, IJmuiden, The Netherlands.

‘Steel is one of the most recycled of commodities, although its sustainability image is weak,’ says Brimacombe. Some 85-99% of construction steel is recycled, and >95% automotive and 61% packaging steel can be looped through several cycles whilst maintaining quality. Scrap alone will not fill the supply gap as it only meets around 30% of global demand and new technologies will have to be perfected to reduce steel’s global CO2 footprint of four per cent.

Most promising are blast furnace top recycling, smelting reduction and alkali-based iron ore electrolysis. The use of biomass, including algae, may also have a role to play as a fuel while releasing oxygen. The way forward towards sustainability has been led by the automotive sector where steel lightweighting and alternative engine technologies have led to dramatic increases in fuel economy.

Further information

www.minsouth.org.uk

Also see Optimising iron and steel waste, Materials World, February 2011