Title

CONTRIBUÇÃO PARA COMPARAÇÕES ENTRE AS TECNOLOGIAS STRAIGHT GRATE E GRATE-KILN

CONTRIBUTIONS TO THE TECHNOLOGY COMPARISON BETWEEN STRAIGHT GRATE AND GRATE-KILN

Authorship

Kordzadeh, Elham; Campos, Fernando; Strüber, Georg; Schwalm, Thomas

Kordzadeh, Elham

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Campos, Fernando

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Strüber, Georg

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Schwalm, Thomas

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DOI

10.5151/2594-357X-30901

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Abstract

As the world’s reserves of coarse and high-grade iron ores continue to shrink, beneficiation is becoming increasingly important. The resulting concentrates cannot be used directly as feedstock for iron making, but require an additional agglomeration step. Pelletizing is preferred, because the uniform chemical, physical, and metallurgical characteristics of pellets make them a more desirable feed for the iron making processes. The heat hardening or induration of pellets is typically done in shaft furnaces, grate-kiln systems or on straight grates. Rotary kilns were originally developed in the late 19th century for Portland cement production [1]. The main development work for the successful adaptation of the process to the thermal treatment (induration) of green balls from iron ore was performed by Allis Chalmers in Milwaukee, Wisconsin, USA in the 1960’s [2].The straight grate process, which was first used in 1955 at Silver Bay, Minnesota, was a dedicated development with the aim to pelletize and indurate magnetite (taconite) concentrate [2]. There are various important technical and economical distinctions between the two pelletizing technologies. The most important differences include that a grate-kiln has three distinct pieces of equipment, a preheat grate, a rotary kiln and an annular cooler, whereas in the case of a straight grate, the entire indurating process is done on one piece of equipment only. In addition, both technological solutions have differences in their recuperation systems, direction of air flow in drying, number of burners, form of pellet movement, etc., which cause differences in raw material suitability, process control, economical aspects, plant operation and product pellet quality.

Keywords

Pelotamento, Endurecimento, Straight Grate, Grate Kiln

Pelletizing, Induration, Straight Grate, Grate Kiln