Marine Blocks for Artificial Reefs Made from Steelmaking Slag
NKK has succeeded in developing eco-friendly marine blocks, ideal for use in artificial reefs, which are made by utilizing slag, an inevitable by-product of steelmaking. The company has already confirmed good adherence of living marine organisms to these blocks during initial experimental tests. NKK's Marine Block is a large carbonic solid (CaCO3) produced by reacting lime (CaO), a main ingredient of slag generated in the steelmaking process, on carbon dioxide (CO2) contained in exhaust gas. While this reaction process has been known for years, it has been difficult to achieve a uniform reaction pervading throughout the block, which restricted the size of the block manufactured. To overcome this problem, NKK applied a new technology to add optimum amounts of water along with apertures to the slag-formed solid block, thereby forcibly supplying CO2 deep into the inner part of the block. This method made it possible to manufacture uniformly carbonated large solid blocks. Marine Blocks offer the following advantages.
In the experimental tests conducted with 25cm cube blocks sunk in the sea bed for a year and half, NKK confirmed greater adherence of marine plants and turban shells on the blocks, which did not collapse, than on concrete blocks or natural stones. NKK is now conducting scaled-up demonstration tests by sinking 15 large blocks (1m × 1m × 50cm weighing about a ton) in pyramid shape into a test site of the Seto Inland Sea in western Japan. After these tests, NKK plans to begin commercial production of Marine Blocks at its Fukuyama Works in mid 2000. |
