Formation of Primary Slag and Carburizing Behavior of Metal Iron in Cohesive Zone of Hydrogen-rich Blast Furnace

Abstract

To obtain the formation characteristics of melting slag-iron in cohesive zone of hydrogen rich blast furnace (BF), the phase composition of primary slag, the variation of slag amount and the mechanism of metal iron carburizing under different atmosphere conditions were analyzed. The results showed that: The hydrogen-rich operation in BF changes the formation of primary slag and the carburizing behavior of metal iron in the cohesive zone. After hydrogen enrichment in gas, the amount of primary slag decreases. The wustite decreases, however, the primary slag absorbs CaO and Al₂O₃ to form the monticellite, hortonolite and magnesium rosaceite. With the increase of hydrogen enrichment ratio φ(H₂), the high melting point material (2CaO·SiO₂) began to crystallize out, and the melting point of primary slag gradually increase, coupled with the substantial reduction of slag content, which may lead to the "Drying" phenomenon of primary slag in hydrogen-rich blast furnace. The hydrogen-rich operation of blast furnace changes the contact mode between the iron charge and coke from surface contact to point contact in the cohesive zone, which reduces the carburizing rate of metal iron in cohesive zone so that the content of [C] and [S] in the dripping molten iron decreases accordingly. The formation of high melting point material in the primary slag and the blockage of the carburizing process of metal iron lead to the increase of the droplet temperature of slag-iron, which makes the blast furnace's cohesive zone move down and thinner.