NKK Uses Steelmaking Slag in Marine
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| Nakaumi water cleanup and sand capping project |
NKK has begun conducting marine environment improvement tests in western Japan's Seto Inland Sea, utilizing slag, a byproduct of iron and steelmaking processes. Commissioned by the Hiroshima Prefecture, the project is the world's first of its kind to use 100% recycled materials, and aims to improve the ocean floor along the coast while revitalizing seaweed beds.
To support the project, NKK's Fukuyama Works supplied about 1,000 tons (800m3) of granulated blast furnace (BF) slag for sand capping and 20 Marine Blocks, which cover over a 600m2 area of the sea. The BF slag has chemical properties that are far more superior than natural sand to maintain the seabed fairly alkalescent. Marine Block is a large carbonic solid (CaCO3) produced by blowing carbon dioxide (CO2) into the pulverized steelmaking slag. It stabilizes perfectly in seawater, becoming marine plant cultivation beds.
NKK undertook the project as a collaborative research
endeavor with the Hiroshima Prefecture Environment Industry Promotion
Council.
Kokan Mining, an NKK subsidiary, and other companies are also involved.
NKK will continue to do follow-up studies on the marine environment
improvement tests to verify that it has indeed created maintenance-free
seaweed beds.
NKK has a long track record in promoting effective use of both BF and steelmaking slag as environmentally sound resources. Since November 1997, it has been conducting tests of Marine Block applications in seaweed bed formation in the Seto Inland Sea, finding the results to be excellent. Last year, 54,000 tons (some 40,000m3 or 4 hectares) of NKK's granulated BF slag was used in the Nakaumi water cleanup and sand capping project near Lake Shinji, supervised by the Izumo Public Works Office of the Ministry of Land, Infrastructure and Transport.
The current test marks the first time that both granulated BF slag sand capping and Marine Blocks have been used in a marine improvement project. The Hiroshima endeavor aims to capitalize on the characteristics of both recycled materials to revitalize the ocean environment.
