Per: pericles guimarães oliveira aguiar (Aperam South America), Filipe Soares Pontes (Aperam South America), José Roberto Simão (Aperam South America), Emagston Martins da Costa (Aperam South America), Roberto Salles de Almeida (Aperam South America), Victoria C. Velozo Meireles (Aperam South America), Raphael F. Miranda de Oliveira (Aperam South America,)
Abstract:
The Blast Furnace, like any other equipment, requires preventive maintenance to ensure continued safe operation and mitigate the risks of emergency shutdowns. As it is equipment that works with positive pressure, high temperatures and generates gases with a risk of explosion, some equipment can only be accessed after stopping the Blast Furnace. After the Blast Furnace stops, the energy input generated by the hot air blown and exothermic reactions are interrupted and the reactor loses energy, generating a heat deficit throughout the stop time. To compensate for the loss of energy, loads with extra fuel are created, thus guaranteeing the thermal recovery of the reactor and the resumption of reactions in the various internal zones.
The impacts caused by the extra fuel are reflected in the low productivity and high percentage of silicon in the hot metal, exceeding the quality limit range, increasing scrapping and limiting the supply of hot metal for the Steelmaking. To guarantee the performance of Blast Furnace 2, 4 stops are scheduled during the year, with an interval of 90 days, for 48 hours, 96 hours or 120 hours.
Aiming to reduce the impacts caused by stopping and restarting Blast Furnace 2. In 2017, work began focusing on the hot air flow curve, extra fuel, binary basicity of the slag, melting time and casthouse operation during the period of stopping and restarting the reactor.
The work reduced the average percentage of silicon in pig iron from 2% (2015) to 1.01% (2021), the standard deviation from 1.20% (2015) to 0.68% (2021) and the peak of the percentage of silicon from 4.84% (2015) to 2.92% (2021). The improvement in the quality of hot metal was reflected in the reduction in scrapping, from 27% of calculated production (2015) to 6% (2021) and in the increase in the delivery of hot metal to the Steelmaking, from 72% of calculated production (2015) to 88% (2021 ) ). To determine the effectiveness of the actions and results obtained, emergency stops were not considered.
