2016-Sustainable Industrial Processing Summit
SIPS 2016 Volume 6: Yagi Intl. Symp. / Metals & Alloys Processing
| Editors: | Kongoli F, Akiyama T, Nogami H, Saito K, Fujibayashi A |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2016 |
| Pages: | 480 pages |
| ISBN: | 978-1-987820-46-1 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Multistep reduction kinetics of hematite (Fe2O3) to iron in a micro fluidized bed reactor by hydrogen at low temperatures
Hongsheng Chen1; Zhong Zheng1; Zhiwei Chen2; Xu He1; Kun He3;1CHONGQING UNIVERSITY, Chongqing, China; 2UNIVERSITY OF BRITISH COLUMBIA, Vancouver, Canada; 3, Chongqing, China;
Type of Paper: Regular
Id Paper: 50
Topic: 3
Abstract:
The production of direct reduced iron (DRI) using hydrogen instead of carbon monoxide helps to reduce CO2 emission and slows down global warming. The reduction of hematite occurs in two-step as Fe2O3-Fe3O4-Fe when temperatures are below 570 ¡æ.A better understanding of the two-step reduction kinetics of hematite with hydrogen will reveal useful fundamental information for the industrial applications and promotes the development of energy-saving technologies for iron making. The reduction of iron oxides into iron is complex because the process is heterogeneous and several elementary reactions take place simultaneously. It is hard to figure out the reduction kinetics under fluidization in a fixed bed reactor such as in a thermogravimetry analyzer (TGA) which suffers from the limitations of heating rate, external diffusion, thermal pretreatment before a reaction occurs. In this study, the reduction kinetics of hematite to metallic iron with hydrogen at temperature 300¡æ-550¡æ are experimentally investigated in a micro-fluidized bed reaction analyzer (MFBRA), developed by the Institute of Process Engineering (IPE), Chinese Academy of Sciences (CAS) to study the kinetics of fast gas-solid reactions. Results indicate that the low-temperature reduction of hematite with hydrogen can be well captured by a two-step kinetics method based on Johnson-Mehl-Avrami (JMA) model using statistical analysis tools in the Statistical Product and Service Solutions (SPSS). It shows that the reduction process can be interpreted as two elementary reactions (i.e. hematite-magnetite and magnetite-iron), which proceed in parallel with different controlling mechanisms as well as with different time dependencies. The kinetics parameters, i.e. activation energy and pre-exponential factor, are determined for each elementary reaction. The contribution of each individual reaction to the whole reduction process is further discussed. The results also suggest that the reduction of hematite to magnetite takes place fast and dominates the initial part of the entire reduction while the reduction of magnetite to iron plays a less important role in the initial stage but controls the whole reduction in the late stage. The conclusions obtained in this study are comparable with that in the literature and indicate that the two-step kinetics model is able to capture the properties of both elementary reactions and the integrated reduction process, providing an analysis strategy for revealing detail characteristics of the low-temperature reduction of iron oxides.
Keywords:
Micro fluidized bed; Multistep reduction kinetics; Iron oxide reduction; Hydrogen.References:
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