Effect of the Ratio of Magnetite Particle Size to Microwave Penetration Depth on Reduction Reaction Behaviour by H2

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Abstract

In this study, we investigated reduction of magnetite by H2 during microwave irradiation. This process combines the advantages of microwave irradiation and using H2 as a reducing agent to mitigate CO2 emissions during the ironmaking process. Weight change measurements showed that a reduction of 75% was achieved after treatment under H2 for 60 min. For better understanding of the effective parameters in microwave chemistry, scanning electron microscopy, combined with energy-dispersive X-ray spectroscopy (SEM-EDX), was performed, which demonstrated a greater reduction of large particles (>40 μm) than small particles. This behaviour could be attributed to the higher microwave absorption capability of large particles with a higher ratio of particle size to penetration depth (d/δ). Small particles behave as transparent material and are heated via conduction and/or convection; thus, there is no contribution from the catalytic effect of microwaves to the reduction reaction. Moreover, the reduction of Fe3O4 to Fe0.94O, followed by transformation to Fe, seems to proceed from the surface toward the centre of the particle despite the volumetric microwave heating. This could be due to the higher gas accessibility of iron oxide on the particle surface than in the particle centre.

Original languageEnglish
Article number15023
JournalScientific reports
Volume8
Issue number1
DOIs
Publication statusPublished - Dec 1 2018

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Ferrosoferric Oxide
Microwaves
Particle Size
X-Ray Emission Spectrometry
Convection
Reducing Agents
Electron Scanning Microscopy
Heating
Gases
Weights and Measures

All Science Journal Classification (ASJC) codes

  • General

Cite this

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title = "Effect of the Ratio of Magnetite Particle Size to Microwave Penetration Depth on Reduction Reaction Behaviour by H2",
abstract = "In this study, we investigated reduction of magnetite by H2 during microwave irradiation. This process combines the advantages of microwave irradiation and using H2 as a reducing agent to mitigate CO2 emissions during the ironmaking process. Weight change measurements showed that a reduction of 75{\%} was achieved after treatment under H2 for 60 min. For better understanding of the effective parameters in microwave chemistry, scanning electron microscopy, combined with energy-dispersive X-ray spectroscopy (SEM-EDX), was performed, which demonstrated a greater reduction of large particles (>40 μm) than small particles. This behaviour could be attributed to the higher microwave absorption capability of large particles with a higher ratio of particle size to penetration depth (d/δ). Small particles behave as transparent material and are heated via conduction and/or convection; thus, there is no contribution from the catalytic effect of microwaves to the reduction reaction. Moreover, the reduction of Fe3O4 to Fe0.94O, followed by transformation to Fe, seems to proceed from the surface toward the centre of the particle despite the volumetric microwave heating. This could be due to the higher gas accessibility of iron oxide on the particle surface than in the particle centre.",
author = "Ahmadreza Amini and Ko-Ichiro Ohno and Takayuki Maeda and Kazuya Kunitomo",
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AU - Amini, Ahmadreza

AU - Ohno, Ko-Ichiro

AU - Maeda, Takayuki

AU - Kunitomo, Kazuya

PY - 2018/12/1

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N2 - In this study, we investigated reduction of magnetite by H2 during microwave irradiation. This process combines the advantages of microwave irradiation and using H2 as a reducing agent to mitigate CO2 emissions during the ironmaking process. Weight change measurements showed that a reduction of 75% was achieved after treatment under H2 for 60 min. For better understanding of the effective parameters in microwave chemistry, scanning electron microscopy, combined with energy-dispersive X-ray spectroscopy (SEM-EDX), was performed, which demonstrated a greater reduction of large particles (>40 μm) than small particles. This behaviour could be attributed to the higher microwave absorption capability of large particles with a higher ratio of particle size to penetration depth (d/δ). Small particles behave as transparent material and are heated via conduction and/or convection; thus, there is no contribution from the catalytic effect of microwaves to the reduction reaction. Moreover, the reduction of Fe3O4 to Fe0.94O, followed by transformation to Fe, seems to proceed from the surface toward the centre of the particle despite the volumetric microwave heating. This could be due to the higher gas accessibility of iron oxide on the particle surface than in the particle centre.

AB - In this study, we investigated reduction of magnetite by H2 during microwave irradiation. This process combines the advantages of microwave irradiation and using H2 as a reducing agent to mitigate CO2 emissions during the ironmaking process. Weight change measurements showed that a reduction of 75% was achieved after treatment under H2 for 60 min. For better understanding of the effective parameters in microwave chemistry, scanning electron microscopy, combined with energy-dispersive X-ray spectroscopy (SEM-EDX), was performed, which demonstrated a greater reduction of large particles (>40 μm) than small particles. This behaviour could be attributed to the higher microwave absorption capability of large particles with a higher ratio of particle size to penetration depth (d/δ). Small particles behave as transparent material and are heated via conduction and/or convection; thus, there is no contribution from the catalytic effect of microwaves to the reduction reaction. Moreover, the reduction of Fe3O4 to Fe0.94O, followed by transformation to Fe, seems to proceed from the surface toward the centre of the particle despite the volumetric microwave heating. This could be due to the higher gas accessibility of iron oxide on the particle surface than in the particle centre.

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