Tenaris Dalmine, Italy, recently installed a MORE srl HI_JET injector to pneumatically inject lime into the steel interface, which will help to improve phosphorous removal capability.
Last year (March 2008), Tenaris Dalmine had installed a MORE pneumatic lime/dolo-lime injection system in their 100-tonne electric arc furnace. The supply included two dedicated MOLI dispensers installed under two 125-m3 (4400-ft3) storage silos. From each MOLI exit, the material was pneumatically conveyed to two LIMEJET combined burner/lime injectors.
Tenaris Dalmine tried several different layout configurations as well as different kinds of injected materials through multiple campaigns, eventually deciding on a final configuration where one of the two LIMEJETs was replaced by a HI_JET injector.
With the HI_JET injector, the fluxes fines are embedded into an annular supersonic oxygen stream. The oxygen stream’s high velocity causes the lime particles to exchange momentum with the oxygen, which increases their speed up to 400 m/s (895 mph) — about ten times higher than the exit speed of the traditional lime injectors. The HI_JET injector also incorporates the MSF-Mixed Swirl Flame technology (up to 5 MW) for heating and assisted melting of scrap after each scrap bucket charge.
Because the injector helps the high-speed lime pierce through the slag to reach the steel, the technology helps to improve the interaction and minimize the loss of lime into the fumes. The injector also enables the injection of lime at the proper temperature range (at the beginning of the refining phase), which also helps to improve the phosphorous removal capability.
Consolidated results have demonstrated the ability to achieve the same phosphorous content in the steel at tapping while reducing the total amount of lime by 300 kg (661 lb) per heat, a savings of 3 kg/ton (60 lb/ton).
Based on its experience with the HI_JET and its ability to inject material into the liquid steel, Tenaris Dalmine has decided to install an additional MOLI dispenser to feed the HI_JET injector with alternative slag formers. The third MOLI dispenser is scheduled to be installed in January 2010.