DRI from Recycled Iron Bearing Wastes for Lower Carbon in the Blast Furnace

Abstract

Reduction of Fe-bearing FINEX process waste and carbon composite pellets from 1 373 K to 1 573 K to produce DRI (direct reduced iron) for use in the blast furnace was investigated using a modified thermogravimetric analyzer. Reduction from the initial Fe 2 O 3 was not uniform throughout the composite pellet. Oxygen removal from the Fe 2 O 3 rich composite pellets over 84% was only observed at 1 573 K. Lower temperatures resulted in significantly un-reduced FeO t due to the premature consumption of the carbon. A peripheral boundary of FeO t ·Al 2 O 3 and 2FeO·SiO 2 phases surrounding the reducible FeO t was observed in some of the partially reduced cross-sectional SEM (scanning electron microscope) images that could hinder reduction. From the apparent activation energy, interfacial reaction seems to affect the kinetics of the Fe-bearing process waste composite pellets. Bursting of pre-dried composite pellets containing less than 2 mass% moisture was simulated in a RHF hearth simulator. From direct observation of pellets charged between 1 173 K to 1 573 K, medium-sized pellets between 9.4 to 12.4 mm diameter showed less bursting of the pellet, when charged below 1 273 K. In addition, modification of the physical strength of the hard bedrock formed from pellet bursting could be softened with additions of SiO 2 .

Estimation of Carbon Dioxide Emissions in Rotary Hearth Furnace Using a Thermodynamic Model

“…Therefore, heat requirement in zone‐II is calculated from sensible heat required to heat the coal char and iron ore from 400 to 900 °C. Reduction reaction (Equation and 10) at 900 °C carried out in zone‐III, which is highly endothermic in nature and after reduction the reaction product consist of metallic iron, iron in combined form, and gangue. Finally, the reaction product is heated to solid exit temperature (1250 °C for the present study) from 900 °C.…”

“…There has been extensive work performed on the reduction of iron ore-coal composite pellets and its kinetics in RHF experimentally as well as mathematical modeling. [3][4][5][6][7][8][9][10][11][12][13] But only few work has been reported on modeling of RHF for arriving at energy requirements and CO 2 emission (kg-CO 2 /ton product iron) of RHF process routes like Fastmelt and ITmk3. It is reported that energy consumptions and emissions of CO 2 from RHF are lower than in the blast furnace route.…”

Study of the Deposition Formation Mechanism in the Heat Exchanger System of RHF

“…The production of RHF is affected, because the occurrence of deposition reduces the heat transfer efficiency and increases the furnace pressure. In the past, regarding the RHF process study, researchers were often concerned about the metal element reduction and energy efficiency [8][9][10][11][12], while the effect of deposition on the heat transfer system for RHF was ignored. In this study, the deposition was…”

Investigation on the Reduction Behavior of Coal Composite Pellet at Temperatures between 1373 and 1573 K

“…Commercial plants of coal‐based rotary hearth furnace (RHF) have achieved some success, where high quality iron ore and coal feeds are readily available. This RHF has also been frequently used in the production of direct reduced iron (DRI) from iron and steelmaking by‐products of dust, sludge, and mill scale, but the DRI results in slightly lower metallization and higher gangue material . Pulverized coal is widely available in Australia or China, which is a common by‐product of coal mining process.…”