TORNIO: Slag challenges the definition of waste
One of the side-products generated by the steel industry is slag. “It’s like limestone produced from a volcano,” explains Juha Ylimaunu, Manager of Environmental Affairs at Outokumpu’s Tornio Works and Kemi mine in Finland.
In order to reduce the amount of side-products, slag should be turned into a product that can be put to some useful use. Steel slag products are used especially as construction materials in buildings and roads. At Tornio Works, all slag from the ferrochrome plant and one-third from the steel melting shop is turned into construction material. “Our goal is one hundred percent in the future,” Ylimaunu says. Altogether the amount of slag produced by Tornio Works equals the amount of the household waste produced by half of all Finland. “Our processes and materials are unique. We engage in continuous development work. We need to develop systems for specific needs and find the economically and technically best practices,” he continues. According to him, product development is not always easy because slag faces many prejudices. By society, slag is perceived as useless, and a Finnish state permitting authority even tried to classify ferrochrome-slag based products as waste. However, Finland’s Supreme Administrative Court ruled otherwise, and at present the slag products fulfill the requirements of all applicable standards.
AVESTA: A new method turns pickling sludge into a Hydroflux material
At Avesta Works in Sweden, the amount of waste from the stainless steel process is reduced by a method that turns pickling hydroxide sludge into a Hydroflux product. “Then it’s no longer waste,” explains Gunnar Ruist, Quality Manager at Avesta Works. Hydroflux can be used as an alloying element in steel making. Thanks to the new method, about 12,000 tons of waste is avoided every year.
Outokumpu has a patent for the method. The process was implemented in 2003. Process development had started seven years earlier as a joint project with a Minerals and Metals Recycling program. It was funded by the Swedish steel industry. The goal was to find ways to utilize “waste” materials within the industry.
TORNIO: Waste reduced by swirling it around
Tornio Works has managed to reduce the amount of waste with a ferrochrome slag extraction process. The process is operated by the materials handling company Tapojärvi Oy as a subcontractor. A machine which works like a spiral separates chrome from processed fine slag. Chrome is heavier so it is concentrated in the center of the spiral. The recovered chrome can be reused in the melting shop, and the slag is used as a material for new filler products.
Filler products are used, for example, in cement and asphalt. Earlier this fine material ended up in the landfill unseparated. Thanks to the process, there is now about 10,000 tons less waste than before. Mikko Annala, an Environmental Engineer at Tornio Works, says, “This is not a new invention in the world, but last year we realized that we could use the process for our purposes here.”
DEGERFORS: Heating energy from a cooling water system
The Degerfors site in Sweden aims to improve energy efficiency with the help of a certified energy management system. Niklas Wass, an Environmental Engineer at Degerfors, feels that so far the efforts have been successful.
Degerfors rebuilt their cooling water compressors in 2006. Hot water produced by the system is now used to heat two of the site’s buildings, which were previously heated with steam. “We are also working on reducing energy consumption in other buildings,” Wass says.
TORNIO: A new system recovers the heat of combustion gases
A huge amount of energy is recovered at Tornio Works’ hot rolling mill every year. The same amount of energy would heat about 8,500 houses. The solution is quite simple. Energy is recovered from the slab heating process, transferred to a district heating system, and used again elsewhere in the mill. The recovered energy compensates for heavy fuel oil.
The latest heat recovery process was introduced in the beginning of 2006. Now two heating ovens are equipped with a system that recovers the heat of combustion gases. The recovered heat increased energy savings significantly and corresponds to the combined heating energy of about 3,400 houses. Anne Kärki, a Development Engineer at Tornio Works and a specialist in energy issues, is pleased with the solution. She comments, “In the past, combustion gases, at temperatures around 400 degrees Celsius, escaped to the air. The investment will pay itself back within two years.”
SHEFFIELD: Management system helps to save energy
The melting shop in Sheffield, U.K. intends to achieve an ambitious target in energy saving by adopting a new energy management system. According to this system, the personal development dialogue process is used to assign specific responsibilities to a few chosen people in charge of energy saving. “We are focusing on specific areas such as the melting shop and office lighting, efficient use of natural gas in the melting shop, and use of renewable energy sources in the future,” says Lee Adcock, an Environmental Engineer at the melting shop.