Electric arc gets the orders
4 Aug 2000
NKK has landed the first order for its environmentally-friendly, energy-efficient electric arc furnace, 'ECOARC,' from Kishiwada Steel, an Osaka-based electric-furnace steelmaker specialising in small round bars.
ECOARC is a new electric arc furnace independently developed by NKK. The company launched development work in 1995, proceeding to test operations in 1998 by building a 6-ton capacity plant at its Toyama Works (now NKK Materials).
NKK's 3-billion yen order covers an electric arc furnace and a set of related facilities that include a ladle furnace for secondary refining, a material handling system and a scrap yard facility. The furnace will be installed at Kishiwada's steelmaking shop as a replacement for the existing facility.
By using the new electric furnace, it is possible to lower the consumption of electricity to 185 kWh per billet ton compared to 360-380 kWh per billet ton consumed by conventional furnaces, leading to substantial reductions in steelmaking cost. NKK believes a reduction of about 20%, or 2,000 yen per ton, will be possible. The furnace also achieves reduced dioxin emissions, assuring an emission level below 0.5ng-TEQ/Nm3.
ECOARC is a fully closed melting shaft furnace, into which scrap is continuously charged from the top of the shaft portion. As scrap falls to the furnace portion, it mixes with molten steel and is melted rapidly. Due to this furnace structure, which enables scrap to be fed into molten steel, the heat loss on water-cooled panels and fingers is effectively prevented, thereby maintaining scrap-preheating temperature at around 1,000C, which results in lower consumption of electricity.
To deal with dioxin emissions, the furnace is equipped with flue gas post-treatment devices. Due to the completely sealed design of ECOARC, flue gas is heated to around 900°C in the combustion chamber, then rapidly cooled to below 200°C. This rapid cooling prevents the generation of dioxin and other pollutants. Generation of dust and smoke is also minimised.
On the web at www.nkk.co.jp
