Subscribe to SSC News

Get regular SSC updates delivered to your inbox.
Name:

Email Address:

Join SSC

By joining SSC you can enjoy the benefits of belonging to an organisation dedicated to the advancement of steel as the sustainable construction material of choice.

Steel Producer

NZ Steel

New Zealand Steel

New Zealand Steel is the country's largest steel producer generating up to 600,000 tonnes a year. Contributing 1% of the country's GDP, the company employs over 1,000 people making it the largest single site employer in New Zealand.

New Zealand Steel has mastered the sand-to-steel process, making it unique among steel producers worldwide. The rich black sands of the North Island's west coast underpin steelmaking at NZ Steel's Glenbrook facility. The company mines the vast inland deposits of ironsand (titanomagnetite) from two sites: Waikato North Head and Tarahoa. This ironsand, formed through the breakdown of rocks created by volcanic activity in the Taranaki region, was transported up the coast by ocean currents over 2 million years ago. Today it forms huge ironsand reserves that stretch inland from the beach.

New Zealand Steel's facility at Glenbrook operates as a one-stop shop for steel production. The ironsand is converted into a slurry and pumped from the Waikato North Head minesite to Glenbrook - ready to begin the steel making process. This process of transforming sand into steel is extremely complex. In short, the ironsand is mixed with Huntly coal and limestone, then heated and dried in multi hearth furnaces. Next it is fed to reduction kilns where the temperature converts the primary concentrate to direct reduced iron. This is then fed to electric melters and heated to 1480°C melting the direct reduced iron - upon which it separates into molten pig iron and vanadium rich slag.

Molten pig iron is a key ingredient in the steelmaking process. After being tapped from the melters into ladles it is transported to the Slabmaking Plant, which consists of an Oxygen Steelmaking Furnace and Continuous Slab Casting machine. The molten iron is then mixed with scrap steel and refined to produce liquid steel upon which it is transferred to the continuous caster, where the molten product is cast into slabs.

The steel slabs are left to cool before eventually being reheated and rolled down to about 25mm before passing through the finishing mills to achieve its final thickness. The steel is then water cooled and coiled ready for further processing.

From here the steel coil can go through an array of different processes but will ultimately be transported off site as one of the following products:

  • COLORSTEEL®
  • ZINCALUME® steel
  • GALVSTEEL™
  • Hot Rolled Steel
  • Cold Rolled Steel
  • Pipe & Hollow Sections
  • AXXIS® steel for framing

Sustainability

NZ Steel has had an environmental management system in place since taking the lead in the 1970s and establishing a laboratory to assess the environmental impact of its operations at Glenbrook. In 2003 it was awarded ISO 14001, an internationally recognised environmental standard.

In the mid-90s, NZ Steel voluntarily agreed to lower its carbon emissions. This commitment led the company to build a cogeneration plant, which uses waste gas from the ironmaking reduction kilns to generate electricity. Today NZ Steel produces up to 60% of its own electricity, greatly reducing its reliance on the national grid.

Heat
The process of converting iron to steel requires heating materials to extremely high temperatures. Once molten, the iron must be transferred between different areas exposing it to heat loss. The plant is highly efficient at getting the hot iron from one point to the next, reducing the need to reheat the material.

Waste
Close to 82% of the waste from the plant is diverted from landfill and recycled into co-products, reused or resold. One of the main by-products of steel making is steel aggregate or slag, a non-metallic residue skimmed from the smelting process. A range of uses has been developed for this product, including base coarse and road surfacing, sports field drainage, soil conditioning, sandblasting and water filtration.

Water
New Zealand Steel recycles 99% of its water. The remaining 1% is cleaned, tested and discharged. Water is discharged into mixing points in the Waiuku estuary, which are continuously checked. Reports are submitted to regulatory bodies and New Zealand Steel consistently meets the requirements set.

All rainwater falling on site is collected in large settling ponds. The water is then clean enough to either discharge into the Waiuku Estuary, or recycle back into the site water circuits.

Transportation
Around 1.4 million tonnes of ironsand concentrate – the equivalent of the iron ore used in other steeling-making processes – is pumped 18km to the Glenbrook site each day. Electric-powered conveyor belts and an electric underground slurry pipeline are used to transport the ironsand. The cost to install the underground transportation was very significant.

Coal is the other major ingredient for steeling making. It's sourced close to the mill in the Waikato area and transported to Glenbrook via a purpose-built rail link. The material is stockpiled close to the smelter area to minimise handling.

New Zealand Steel is an integrated site where raw steel and finished products, including painted products, are all made. This is unusual in the global steel industry but by its very nature eliminates extensive transportation between each steel-making process.

Land Restoration
25% of mined sand is extracted as titanomagnetite (ironsand). The remainder is returned to the mined areas, which are then planted with marram grass and pine trees. Once restored there is little or no trace of mining.

Air
The biggest percentage of the company's capital investment in environmental control is in the improvement of the quality of its emissions into the atmosphere. The scale of the air cleaning operation is enormous with more than 3 million cubic metres of waste gas being cleaned each hour when the steel mill is working to full capacity. New Zealand Steel has an air monitoring programme in place to assess air quality. Reports are submitted to regulatory bodies and New Zealand Steel consistently meets the stringent requirements set.

Carbon
The chemical reaction in any steel-making process produces carbon as there is no steel-making technology available in the world that does not produce this reaction. At New Zealand Steel 80% of the organisation's carbon emissions come from the-steel making process. New Zealand Steel has comprehensive environmental policies and practices in place to manage the remaining 20% of carbon emissions.

In line with the sustainability actions identified by worldsteel, New Zealand Steel is exploring new technology for the future to reduce carbon emissions associated with the steel-making process. Research is currently underway with a major Japanese steel producer to explore ways to reduce coal usage.


www.nzsteel.co.nz