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Steel Producer

Pacific Steel

 

Pacific Steel

Steel is infinitely recyclable without detriment to its material properties. Pacific Steel makes steel in New Zealand entirely by recycling. Of the approximately 500,000 tonnes of scrap metal generated annually in New Zealand, Pacific Steel use an average 300,000 tonnes per year and the rest is exported. It is an extremely efficient process with around 92% of the scrap metal it processes being turned into steel.

Pacific Steel's steel-making process
All Pacific Steel scrap is sourced locally and is sorted and shredded depending on its grade and size. The scrap is fed in batches to an electric arc furnace, where an electric current is combined with chemical energy to heat the scrap to a near molten state.

Oxygen and carbon are injected taking the molten metal to a base level, and allowing slag to form a ‘skin' over the top of the molten steel. The slag, which contains unwanted impurities, is collected, processed and reused as high-grade roading material.

Following further processing the molten steel is transformed into billets, which are cut to the desired length. The billet is normally consumed by Pacific Steel's rolling mill, where it is turned into rolled products like reinforcing bar and wire rod.

Sustainability

Since 1962 when Pacific Steel was founded, the company has played an important role in the environment by taking waste material and converting it into a valuable product. Today the company is New Zealand's largest recycling operation, and the Otahuhu mill in Auckland is the country's primary producer and supplier of wire rod, reinforcing bar products, all made from recovered scrap steel.

Raw materials

Pacific Steel makes all its steel from recycled scrap metal, turning it into an array of reinforcing bar, wire rod and coil products. Recycled steel can be made by using as little as 25% of the energy it takes to make virgin steel and that doesn't take into account the savings in terms of mining, transportation, landfill and greenhouse gas emissions.

The American Institute of Architects (AIA) Environmental Resource Guide says that each tonne of recycled steel saves 1,100kg of iron ore, 600kg of coal and 50kg of limestone. The AIA also states that every kilogram of steel produced from recycled sources rather than raw materials, saves 12.5MJ of energy, 86% less emissions to air are produced, 40% less water is used and 97% less mining waste is created.

Recycling and waste minimisation

Pacific Steel has developed a by-product management strategy to reduce its waste streams. Historically, waste streams were stockpiled on site, creating the 200,000 tonne “Mt Pacific”. Over a nine-month period in 2009 this debris was painstakingly sorted, recovering $3 million of metal, which was recycled back into the furnace.

Winstone Aggregates set up a crushing and sorting plant on site, which now processes all the primary steel-making slag into “GRIPCHIPTM”, a hard-wearing and high skid-resistant product used for road surface application.

Dedicated bays in the reclaimed areas ensure that streams are kept separate to avoid potentially valuable by-products being contaminated by other debris. Where possible, by-products are reused in the process.

  • Waste ladle refractory is ground, bagged and used to replace the lime previously used to plug the ladle taphole, rather than being landfilled.
  • Mill scale, formed on the steel billets and removed in the Rolling Mill and from the bar in the wire-drawing process, is collected and sold to both New Zealand Steel as a feedstock and to Golden Bay Cement as an additive in high iron mixes.
  • Used refractory material is stored separately and returned to the supplier for recycling.
  • Secondary slag is stockpiled for three months and then sorted to recover the approximately 1/3 metal content for recycling. The remaining debris goes to a landfill site, but is used there for road construction and cover material rather than being dumped as waste.

Hazardous dust extracted from the steel plant baghouse is currently the only true ‘waste' stream as this is stabilised and landfilled. However, technologies for extracting the 20-50% zinc in this dust have been trialled and in the future it is hoped that a recovery plant will be constructed to process this.

Emissions management

Creating a by-product processing facility on site required Pacific Steel to minimise any impact on its neighbours. Dust was a key concern, with a requirement to minimise emissions during processing and ensure there is no wind-blown nuisance from stockpiles. A permanent noise bund was created using stabilised waste material and extensive native planting went in around the fence lines to create a further natural amenity screen.

Water minimisation

Water spray systems were required to suppress dust from the stockpiles and additional water was required for the crusher and for wetting the dusty unsealed roads on site. Rather than use potable water, a pumping system takes water from the wetlands to treat the site stormwater and overflows from the plant water treatment systems. This ensures that in dry weather there is no discharge to the environment from the site and minimises the use of potable water.


www.pacificsteel.co.nz