Reduction Kinetics of Compact Hematite with Hydrogen from 600 to 1050 °C
Reduction of iron ores with hydrogen is a solution to replace fossil fuels. For this reason, it is important to discuss previous discrepancies. Some previous studies suggest a rate minimum with respect to temperature. Our research work indicates that a rate minimum can be avoided. Thermogravimetric...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2023-02-01
|
| Series: | Metals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2075-4701/13/3/464 |
| _version_ | 1797610156056379392 |
|---|---|
| author | Junguo He Kejiang Li Jianliang Zhang Alberto N. Conejo |
| author_facet | Junguo He Kejiang Li Jianliang Zhang Alberto N. Conejo |
| author_sort | Junguo He |
| collection | DOAJ |
| description | Reduction of iron ores with hydrogen is a solution to replace fossil fuels. For this reason, it is important to discuss previous discrepancies. Some previous studies suggest a rate minimum with respect to temperature. Our research work indicates that a rate minimum can be avoided. Thermogravimetric isothermal reduction experiments were carried out from 600 to 1050 °C with pure reagent ferric oxide and hydrogen using a tubular furnace. The morphology and chemical composition of the initial sample, consisting of particulate hematite (Fe<sub>2</sub>O<sub>3</sub>), and the final product, consisting of metallic iron (Fe°), was defined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The reduction rate for the conversion from hematite to magnetite (Fe<sub>2</sub>O<sub>3</sub> to Fe<sub>3</sub>O<sub>4</sub>) was the highest, around 5 %/min, decreasing to around 2–5%/min for the second stage of conversion from magnetite to wüstite (Fe<sub>3</sub>O<sub>4</sub> to FeO). This reduction rate remains almost constant from about 20–80% reduction, decreasing to 0.3–1%/min for the completion of reduction from wüstite to metallic iron (FeO to Fe°). The reduction controlling mechanism was evaluated based on the calculated apparent activation energy and fitting the experimental data to one gas-solid reaction equation. Under the experimental conditions in this work, the reduction rate of pure hematite with hydrogen linearly increased with temperatures from 600 to 1000 °C, without a rate minimum in this temperature range. Above 1000 °C, the reduction rate decreased due to sintering phenomena. This result suggests a maximum reduction temperature of 1000 °C using pure hematite and hydrogen as the reducing gas. The reduction controlling mechanisms identified using hydrogen as a reducing gas were chemical reaction for the conversion from hematite to wüstite and diffusion control for the final reduction from wüstite to metallic iron. Since the reduction rate from wüstite to metallic iron is the one that affects the overall rate of reduction, overall changes in porosity were also evaluated. Finally, the reduction of wüstite is schematically described. |
| first_indexed | 2024-03-11T06:11:33Z |
| format | Article |
| id | doaj.art-b0b11230d51945b9831e8ded6dfd3531 |
| institution | Directory Open Access Journal |
| issn | 2075-4701 |
| language | English |
| last_indexed | 2024-03-11T06:11:33Z |
| publishDate | 2023-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Metals |
| spelling | doaj.art-b0b11230d51945b9831e8ded6dfd35312023-11-17T12:38:08ZengMDPI AGMetals2075-47012023-02-0113346410.3390/met13030464Reduction Kinetics of Compact Hematite with Hydrogen from 600 to 1050 °CJunguo He0Kejiang Li1Jianliang Zhang2Alberto N. Conejo3School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, ChinaSchool of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, ChinaSchool of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, ChinaSchool of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, ChinaReduction of iron ores with hydrogen is a solution to replace fossil fuels. For this reason, it is important to discuss previous discrepancies. Some previous studies suggest a rate minimum with respect to temperature. Our research work indicates that a rate minimum can be avoided. Thermogravimetric isothermal reduction experiments were carried out from 600 to 1050 °C with pure reagent ferric oxide and hydrogen using a tubular furnace. The morphology and chemical composition of the initial sample, consisting of particulate hematite (Fe<sub>2</sub>O<sub>3</sub>), and the final product, consisting of metallic iron (Fe°), was defined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The reduction rate for the conversion from hematite to magnetite (Fe<sub>2</sub>O<sub>3</sub> to Fe<sub>3</sub>O<sub>4</sub>) was the highest, around 5 %/min, decreasing to around 2–5%/min for the second stage of conversion from magnetite to wüstite (Fe<sub>3</sub>O<sub>4</sub> to FeO). This reduction rate remains almost constant from about 20–80% reduction, decreasing to 0.3–1%/min for the completion of reduction from wüstite to metallic iron (FeO to Fe°). The reduction controlling mechanism was evaluated based on the calculated apparent activation energy and fitting the experimental data to one gas-solid reaction equation. Under the experimental conditions in this work, the reduction rate of pure hematite with hydrogen linearly increased with temperatures from 600 to 1000 °C, without a rate minimum in this temperature range. Above 1000 °C, the reduction rate decreased due to sintering phenomena. This result suggests a maximum reduction temperature of 1000 °C using pure hematite and hydrogen as the reducing gas. The reduction controlling mechanisms identified using hydrogen as a reducing gas were chemical reaction for the conversion from hematite to wüstite and diffusion control for the final reduction from wüstite to metallic iron. Since the reduction rate from wüstite to metallic iron is the one that affects the overall rate of reduction, overall changes in porosity were also evaluated. Finally, the reduction of wüstite is schematically described.https://www.mdpi.com/2075-4701/13/3/464hydrogen reductionactivation energyrate of reductionporositycontrolling mechanism |
| spellingShingle | Junguo He Kejiang Li Jianliang Zhang Alberto N. Conejo Reduction Kinetics of Compact Hematite with Hydrogen from 600 to 1050 °C Metals hydrogen reduction activation energy rate of reduction porosity controlling mechanism |
| title | Reduction Kinetics of Compact Hematite with Hydrogen from 600 to 1050 °C |
| title_full | Reduction Kinetics of Compact Hematite with Hydrogen from 600 to 1050 °C |
| title_fullStr | Reduction Kinetics of Compact Hematite with Hydrogen from 600 to 1050 °C |
| title_full_unstemmed | Reduction Kinetics of Compact Hematite with Hydrogen from 600 to 1050 °C |
| title_short | Reduction Kinetics of Compact Hematite with Hydrogen from 600 to 1050 °C |
| title_sort | reduction kinetics of compact hematite with hydrogen from 600 to 1050 °c |
| topic | hydrogen reduction activation energy rate of reduction porosity controlling mechanism |
| url | https://www.mdpi.com/2075-4701/13/3/464 |
| work_keys_str_mv | AT junguohe reductionkineticsofcompacthematitewithhydrogenfrom600to1050c AT kejiangli reductionkineticsofcompacthematitewithhydrogenfrom600to1050c AT jianliangzhang reductionkineticsofcompacthematitewithhydrogenfrom600to1050c AT albertonconejo reductionkineticsofcompacthematitewithhydrogenfrom600to1050c |