The sustainability of steel
(Originally published 11 March 2016)
Globally, the steel industry is raising its sustainability credentials, boosted by steel’s infinite recyclability. In Australia, this is a primary focus for InfraBuild (formerly LIBERTY OneSteel), which has collaborated with UNSW to develop Polymer Injection Technology (PIT), an innovation that can help raise a project’s Green Star credentials. This groundbreaking work also delivers greater efficiencies in the steel-making process by recycling materials that would otherwise go to landfill.
PIT: Inventive and energy efficient
The equivalent of more than 2.4 million car tyres have been recycled in Australia using PIT since 2007. If laid out in a single line, the tyres would run 1565 km – the equivalent of the distance from Melbourne to Coober Pedy. In a development process that took years, InfraBuild worked with the University of NSW to evolve the conventional Electric Arc Furnace (EAF) process which, worldwide, accounts for approximately 430 million tonnes of the 1.6 billion tonnes of steel produced annually. In the traditional EAF process, slag foaming is improved by injecting coke or anthracite.
The PIT process adds recycled polymers, from car tyres for example, to reduce the amount of coke being injected. PIT improves the foaming properties of steel slag, in turn reducing energy consumption, improving productivity and yield, and lowering greenhouse gas emissions. PIT has been implemented at InfraBuild’s EAF facilities in NSW and Victoria, and it has also been licensed to steelmakers overseas, with successful implementations in Thailand, South Korea, the United Kingdom and Norway.
PIT uses recycled polymers (particularly rubber) in the injectant blend, which can cost less than coke, and reduces the overall amount of injectant required. Moreover, PIT is making use of millions of tyres that would otherwise be sent to landfill, or as has sometimes been the case, discarded in unsightly and unsafe illegal dumps.
Trials for PIT commenced in 2006 and InfraBuild adopted it as standard practice in 2008. As of February 2016, InfraBuild had used over 15,000 tonnes of crumb from end-of-life tyres in its steelmaking process. In a typical month it will use the equivalent of between 20,000 and 40,000 tyres – predominantly shredded car and truck tyres – in the PIT process at its facilities in Laverton in Victoria and Rooty Hill in New South Wales. The PIT process also sees an increase in furnace productivity as a result of reduced power-on time.
Electrical energy efficiency is improved, reducing consumption by approximately three per cent. As InfraBuild notes, increasing the volume and foaminess of the slag leads to a longer arc and improved heat transfer from the arc to the steel; the amount of heat loss through the slag and furnace sidewalls is also decreased. “Significant savings on inject carbon costs can also be made as the PIT process has been shown to reduce the total amount of inject carbon required per heat by 10–20 per cent, depending on the quality of the coke being used,” says InfraBuild.
“Combined with the potential lower price of polymer versus coke, savings of 15–35 per cent can be made on total carbon injectant costs.”
Green Star advantages
The use of InfraBuild can assist in meeting the Green Star steel credit requirements, a system that has allowed property organisations to obtain Green Star steel credit points in construction projects since 2010. In using PIT, InfraBuild customers may be eligible to allocate one Green Star point. The patented process’ use of coke with polymers as an alternative carbon injectant to produce foaming slag in EAF has environmental benefits – in particular, energy is saved, CO2 emissions are reduced and polymers are recycled.
Though PIT has already delivered numerous benefits, InfraBuild’s work is not done. Its collaboration with UNSW continues in a bid to identify and develop greater improvements to conventional steelmaking processes through the use of recycled polymers.
The world’s most recycled material
While the steel industry is increasing its sustainable manufacturing, it should also be noted that steel is itself a sustainable material. More than 650 mega tonnes are recycled annually, making it the most recycled material in the world, according to the World Steel Association.
Steel is 100 per cent recyclable, which is a benefit for the construction industry, a major contributor to waste. A significant proportion of the structural and reinforcing steel produced by InfraBuild is produced from recycled steel, collected by InfraBuild Recycling (formerly LIBERTY Recycling).
Of its many benefits, the steel industry’s commitment to sustainability is enhanced by the inherent reusability of steel. Steel is a prevalent resource in many industries, including infrastructure and, housing and construction – the latter two being the largest consumer of steel; it uses approximately 50 per cent of steel produced.
As the World Steel Association notes, once steel is produced, it has a potentially endless life cycle, adding that: “[One hundred per cent of] scrap from steel production and downstream processing is collected and recycled directly into steel production.”
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