On the Direct Reduction Phenomena of Bauxite Ore Using H2 Gas in a Fixed Bed Reactor

Lazou, Adamantia; Eijk, Casper van der; Balomenos, Efthymios; Kolbeinsen, Leiv; Safarian, Jafar

doi:10.1007/s40831-020-00268-5

Cited by 19 publications

(10 citation statements)

References 19 publications

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“…Lazou et al [22] Studied the CO 2 reduction in the conventional Pedersen Process by reducing iron or bauxite ore at temperatures below and above 560 • C. At temperatures above 860 • C, the formation of FeAl 2 O 4 retards the reduction to metallic iron.…”

Section: Mixed/moving and Fluidized Bed Direct Reduction Reactorsmentioning

confidence: 99%

The Direct Reduction of Iron Ore with Hydrogen

Zhang

Nie

et al. 2021

Sustainability

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The steel industry represents about 7% of the world’s anthropogenic CO2 emissions due to the high use of fossil fuels. The CO2-lean direct reduction of iron ore with hydrogen is considered to offer a high potential to reduce CO2 emissions, and this direct reduction of Fe2O3 powder is investigated in this research. The H2 reduction reaction kinetics and fluidization characteristics of fine and cohesive Fe2O3 particles were examined in a vibrated fluidized bed reactor. A smooth bubbling fluidization was achieved. An increase in external force due to vibration slightly increased the pressure drop. The minimum fluidization velocity was nearly independent of the operating temperature. The yield of the direct H2-driven reduction was examined and found to exceed 90%, with a maximum of 98% under the vibration of ~47 Hz with an amplitude of 0.6 mm, and operating temperatures close to 500 °C. Towards the future of direct steel ore reduction, cheap and “green” hydrogen sources need to be developed. H2 can be formed through various techniques with the catalytic decomposition of NH3 (and CH4), methanol and ethanol offering an important potential towards production cost, yield and environmental CO2 emission reductions.

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Section: Mixed/moving and Fluidized Bed Direct Reduction Reactorsmentioning

confidence: 99%

The Direct Reduction of Iron Ore with Hydrogen

Zhang

Nie

et al. 2021

Sustainability

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“…13-SEM-BSE images of slag 3 (b) with the EDS point on both (a) the bright phase, which is number 886 to 893, and (b) the matrix, which is number 894 to 903. buoyancy effect at high temperatures becomes negligible. [49,50] It is also noted here that the TG-DTA results in the current study have been subtracted by each of the same experimental conditions without the sample. The correction runs were performed before each sample analysis.…”

Section: Raman Spectroscopymentioning

confidence: 99%

Synthesis and Characterization of 12CaO·7Al2O3 Slags: The Effects of Impurities and Atmospheres on the Phase Relations

Azof

Tang

You

et al. 2020

Metall Mater Trans B

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Synthesis of crystalline slags of 12CaO·7Al2O3 phase from the corresponding melt compositions in different atmospheric conditions and different purities is investigated. Observations using a thermogravimetry coupled with differential thermal analysis showed that the dehydration of a zeolitic 12CaO·7Al2O3 phase occur at 770 °C to 1390 °C before it congruently melts at 1450 °C. The X-ray diffraction pattern of the slag showed that a single 12CaO·7Al2O3 phase is produced from a mixture, which has small SiO2 impurity with a 49:51 mass ratio of CaO to Al2O3. A scanning electron microscope and electron probe micro-analyzer showed that a minor Ca-Al-Si-O-containing phase is in equilibrium with a grain-less 12CaO·7Al2O3 phase. Moreover, 12CaO·7Al2O3 is unstable at room temperature when the high-purity molten slag is solidified under oxidizing conditions contained in an alumina crucible. On the other hand, a high-temperature in-situ Raman spectroscopy of a slag that was made of a higher purity CaO-Al2O3 mixture showed that 5CaO·3Al2O3 phase is an unstable/intermediate phase in the the CaO-Al2O3 system, which is decomposed to 12CaO·7Al2O3 above 1100 °C upon heating in oxidizing conditions. It was found that 5CaO·3Al2O3 is present at room temperature when the 12CaO·7Al2O3 dissociates to a mixture of 5CaO·3Al2O3, 3CaO·Al2O3, and CaO·Al2O3 phases during the cooling of the slag at 1180 °C ± 20 °C in reducing atmosphere. It is proposed that low concentrations of Si stabilize 12CaO·7Al2O3 (mayenite), in which Si is a solid solution in its lattice, which is named Si-mayenite. Regarding the calculated CaO-Al2O3-SiO2 diagram in this study, this phase may contain a maximum of 4.7 wt pct SiO2, which depends on the total SiO2 in the system and the Ca/Al ratio.

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“…Part of the utilized CB (148 g) was reduced by 50 vol.-%H 2 and 50 vol.-%Ar mixture to obtain reduced bauxite, RB, with 2 Nl/min total flow rate at 900 • C for 120 min, using a thermogravimetric (TGA) technique. Details of the equipment can be found in our previous publication [26]. The main purpose being the reduction of the iron oxides in bauxite to metallic iron prior to the smelting and the subsequent comparison with the smelting-reduction of the calcined bauxite.…”

Section: Preparation and Analytical Techniquesmentioning

confidence: 99%

Evaluation of Calcium Aluminate Slags and Pig Irons Produced from the Smelting-Reduction of Diasporic Bauxite

2021

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This work evaluates the characteristics of calcium aluminate slag and pig iron samples obtained from the smelting of calcined and reduced diasporic bauxite ore. The study is conducted in the Pedersen process framework, which is a method to produce alumina from low-grade resources. Parameters such as the effect of crucible type, lime addition, and atmospheric conditions are studied considering the characteristics of the product pig irons and calcium aluminate slags for further uses. The behavior of the bauxite and distribution of the species between slag and metal was assessed based on the applied analytical techniques and thermodynamic calculations. Iron was reduced and separated from the slags in the presence of carbon (graphite crucible) for both the reduced and calcined bauxite. Si and Ti were mainly concentrated in the slags. Iron was separated from the slag in the absence of carbon (alumina crucible) for the H2-reduced bauxite. The results show that slags with increased lime additions are composed mainly of 5CaO.Al2O3 and CaO.Al2O3, that are considered highly leachable compounds. An optimum CaO/Al2O3 mass ratio of 1.12 was suggested. The presence of O2 and/or OH- in the furnace atmosphere will result in the formation of 12CaO.7Al2O3.

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On the Direct Reduction Phenomena of Bauxite Ore Using H2 Gas in a Fixed Bed Reactor

Cited by 19 publications

References 19 publications

The Direct Reduction of Iron Ore with Hydrogen

The Direct Reduction of Iron Ore with Hydrogen

Synthesis and Characterization of 12CaO·7Al2O3 Slags: The Effects of Impurities and Atmospheres on the Phase Relations

Evaluation of Calcium Aluminate Slags and Pig Irons Produced from the Smelting-Reduction of Diasporic Bauxite

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