Avaliação do impacto do teor de enxofre de carvões metalúrgicos nos seus valores em uso

Abstract

The origin of sulfur in steel is mainly related to the use of coke on pig iron production in blast furnaces. For some types of steel higher sulfur levels are required due to layers formation of sulfide, which increases machinability. However in most of steels, low sulfur levels are required because this element affects the isotropy of mechanical properties, especially toughness. Considering the limited desulfurization capacity in the primary refining of steel, desulfurization processes between the blast furnace and steel plant are required. This work aims to assess the impact of the sulfur content of metallurgical coals on their values in use. Value in use is the maximum price that a particular company is willing to pay for a replacement material without deteriorating economic results. It was developed an integrated mathematical model of coke oven, blast furnace and desulfurization process in order to assess the impact of the metallurgical coal sulfur content in its value in use. The desulfurizing agents considered were magnesium, synthetic slag, calcium carbide and calcium oxide based mixture. The penalty estimated by price assessment agency for each 0.10% additional sulfur in the coal is 1.20 $/t, considering the price of coal reference equal to 120 $/t. The results showed that in the 18 of the 19 evaluated conditions values of penalties for additional sulfur were lower and therefore the values in use of coals were higher than values published by price assessment agency. The estimated penalty values were between 0.41 $/t and 1.45 $/t. The lowest value was obtained in desulfurization with magnesium, considering sulfur partition in the blast furnace equal to 60 and the highest value was obtained in desulfurization with synthetic slag, considering a pig iron temperature equal to 1300oC.