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Title: Reduction of iron-oxide-carbon composites: part II. Rates of reduction of composite pellets in a rotary hearth furnace simulator

Abstract

A new ironmaking concept is being proposed that involves the combination of a rotary hearth furnace (RHF) with an iron-bath smelter. The RHF makes use of iron-oxide-carbon composite pellets as the charge material and the final product is direct-reduced iron (DRI) in the solid or molten state. This part of the research includes the development of a reactor that simulated the heat transfer in an RHF. The external heat-transport and high heating rates were simulated by means of infrared (IR) emitting lamps. The reaction rates were measured by analyzing the off-gas and computing both the amount of CO and CO{sub 2} generated and the degree of reduction. The reduction times were found to be comparable to the residence times observed in industrial RHFs. Both artificial ferric oxide (PAH) and naturally occurring hematite and taconite ores were used as the sources of iron oxide. Coal char and devolatilized wood charcoal were the reductants. Wood charcoal appeared to be a faster reductant than coal char. However, in the PAH-containing pellets, the reverse was found to be true because of heat-transfer limitations. For the same type of reductant, hematite-containing pellets were observed to reduce faster than taconite-containing pellets because of the development ofmore » internal porosity due to cracking and fissure formation during the Fe2O{sub 3}-to-Fe3O{sub 4} transition. This is, however, absent during the reduction of taconite, which is primarily Fe3O{sub 4}. The PAH-wood-charcoal pellets were found to undergo a significant amount of swelling at low-temperature conditions, which impeded the external heat transport to the lower layers. If the average degree of reduction targeted in an RHF is reduced from 95 to approximately 70 pct by coupling the RHF with a bath smelter, the productivity of the RHF can be enhanced 1.5 to 2 times. The use of a two- or three-layer bed was found to be superior to that of a single layer, for higher productivities.« less

Authors:
;  [1]
  1. Praxair Inc., Tonawanda, NY (United States). Praxair Technological Center
Publication Date:
OSTI Identifier:
21126157
Resource Type:
Journal Article
Journal Name:
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
Additional Journal Information:
Journal Volume: 39; Journal Issue: 6; Journal ID: ISSN 1073-5615
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; IRON OXIDES; COAL; REDUCTION; PELLETS; FURNACES; ROTATION; SMELTING; HEAT TRANSFER; CHEMICAL REACTION KINETICS; IRON ORES; CHARS; CHARCOAL; PRODUCTIVITY; BENCH-SCALE EXPERIMENTS

Citation Formats

Halder, S, and Fruehan, R J. Reduction of iron-oxide-carbon composites: part II. Rates of reduction of composite pellets in a rotary hearth furnace simulator. United States: N. p., 2008. Web. doi:10.1007/s11663-008-9203-1.
Halder, S, & Fruehan, R J. Reduction of iron-oxide-carbon composites: part II. Rates of reduction of composite pellets in a rotary hearth furnace simulator. United States. doi:10.1007/s11663-008-9203-1.
Halder, S, and Fruehan, R J. Mon . "Reduction of iron-oxide-carbon composites: part II. Rates of reduction of composite pellets in a rotary hearth furnace simulator". United States. doi:10.1007/s11663-008-9203-1.
@article{osti_21126157,
title = {Reduction of iron-oxide-carbon composites: part II. Rates of reduction of composite pellets in a rotary hearth furnace simulator},
author = {Halder, S and Fruehan, R J},
abstractNote = {A new ironmaking concept is being proposed that involves the combination of a rotary hearth furnace (RHF) with an iron-bath smelter. The RHF makes use of iron-oxide-carbon composite pellets as the charge material and the final product is direct-reduced iron (DRI) in the solid or molten state. This part of the research includes the development of a reactor that simulated the heat transfer in an RHF. The external heat-transport and high heating rates were simulated by means of infrared (IR) emitting lamps. The reaction rates were measured by analyzing the off-gas and computing both the amount of CO and CO{sub 2} generated and the degree of reduction. The reduction times were found to be comparable to the residence times observed in industrial RHFs. Both artificial ferric oxide (PAH) and naturally occurring hematite and taconite ores were used as the sources of iron oxide. Coal char and devolatilized wood charcoal were the reductants. Wood charcoal appeared to be a faster reductant than coal char. However, in the PAH-containing pellets, the reverse was found to be true because of heat-transfer limitations. For the same type of reductant, hematite-containing pellets were observed to reduce faster than taconite-containing pellets because of the development of internal porosity due to cracking and fissure formation during the Fe2O{sub 3}-to-Fe3O{sub 4} transition. This is, however, absent during the reduction of taconite, which is primarily Fe3O{sub 4}. The PAH-wood-charcoal pellets were found to undergo a significant amount of swelling at low-temperature conditions, which impeded the external heat transport to the lower layers. If the average degree of reduction targeted in an RHF is reduced from 95 to approximately 70 pct by coupling the RHF with a bath smelter, the productivity of the RHF can be enhanced 1.5 to 2 times. The use of a two- or three-layer bed was found to be superior to that of a single layer, for higher productivities.},
doi = {10.1007/s11663-008-9203-1},
journal = {Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science},
issn = {1073-5615},
number = 6,
volume = 39,
place = {United States},
year = {2008},
month = {12}
}