Title

Fundamental Studies on Blast Furnace Burden Softening and Melting

Fundamental Studies on Blast Furnace Burden Softening and Melting

Authorship

NOGUEIRA, PAULO F.; FRUEHAN, RICHARD J.

NOGUEIRA, PAULO F.

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FRUEHAN, RICHARD J.

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DOI

10.5151/2594-357x-34Red-893-902

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Abstract

The cohesive zone in the blast furnace, where ferrous burden materials soften and melt, greatly affects the furnace’s performance. Minimizing the width of the cohesive zone will improve productivity and decrease the coke rate. This work was designed to better understand the softening and melting phenomena of ferrous feed materials. The pellets were reduced to wustite, 60% or 80% reduction degree. Different experimental techniques were used to allow the observation of different stages of softening and melting. For X-ray observation, they were placed in a graphite crucible and heated under N₂ gas flow, while recording the temperature and the contraction of the pellets. In the interrupted experiments, a specially designed apparatus was used allowing interruptions at selected temperatures for microstructural observation. The melt onset experiments allowed the observation of the appearance of liquid, and by cooling from select temperatures allowed the analysis of the evolution of the microstructure. These experiments showed that the dripping of liquid from the pellets occurred at different conditions depending on the reduction degrees. In addition, the melt onset occurred before softening. Furthermore, this early liquid acts as a trigger to the microstructural transformations surrounding softening. These techniques were successful in separating the variables involved in blast furnace metallic burden softening and melting

The cohesive zone in the blast furnace, where ferrous burden materials soften and melt, greatly affects the furnace’s performance. Minimizing the width of the cohesive zone will improve productivity and decrease the coke rate. This work was designed to better understand the softening and melting phenomena of ferrous feed materials. The pellets were reduced to wustite, 60% or 80% reduction degree. Different experimental techniques were used to allow the observation of different stages of softening and melting. For X-ray observation, they were placed in a graphite crucible and heated under N₂ gas flow, while recording the temperature and the contraction of the pellets. In the interrupted experiments, a specially designed apparatus was used allowing interruptions at selected temperatures for microstructural observation. The melt onset experiments allowed the observation of the appearance of liquid, and by cooling from select temperatures allowed the analysis of the evolution of the microstructure. These experiments showed that the dripping of liquid from the pellets occurred at different conditions depending on the reduction degrees. In addition, the melt onset occurred before softening. Furthermore, this early liquid acts as a trigger to the microstructural transformations surrounding softening. These techniques were successful in separating the variables involved in blast furnace metallic burden softening and melting

Keywords

Blast Furnace, Iron Ore Pellets, Softening, Melting, cohesive zone

Blast Furnace, Iron Ore Pellets, Softening, Melting, cohesive zone