Empirical reduction diagrams for reduction of iron ores with H<sub>2</sub>and CO gas mixtures considering non-stoichiometries of oxide phases

361

161

This review focuses on the reduction of iron oxides using hydrogen as a reducing agent. Due to increasing requirements from environmental issues, a change of process concepts in the iron and steel industry is necessary within the next few years. Currently, crude steel production is mainly based on fossil fuels, and emitting of the climate‐relevant gas carbon dioxide is integral. One opportunity to avoid or reduce greenhouse gas emissions is substituting hydrogen for carbon as an energy source and reducing agent. Hydrogen, produced via renewable energies, allows carbon‐free reduction and avoids forming harmful greenhouse gases during the reduction process. The thermodynamic and kinetic behaviors of reduction with hydrogen are summarized and discussed in this review. The effects of influencing parameters, such as temperature, type of iron oxide, grain size, etc. are shown and compared with the reduction behavior of iron oxides with carbon monoxide. Different methods to describe the kinetics of the reduction progress and the role of the apparent activation energy are shown and proofed regarding their plausibility.

Section: Thermodynamics Of Iron Oxide Reduction With Hydrogenmentioning

confidence: 99%

Reduction of Iron Oxides with Hydrogen—A Review

Spreitzer

Schenk

2019

361

161

“…Former research was mainly focused on the influence of process conditions on the materials performance during fluidized bed reduction. By the change of temperature, gas flow rate and gas oxidation degree (GOD) iron ore usually shows differences in reduction behavior . For instance, a higher temperature (temperature range 700–950 °C) or partial pressure of H 2 + CO leads to higher reducibility and higher reduction degrees (RDs).…”

Section: Introductionmentioning

confidence: 99%

Reduction Behavior and Structural Evolution of Iron Ores in Fluidized Bed Technologies—Part 2: Characterization and Evaluation of Worldwide Traded Fine Iron Ore Brands

Pichler

Mali

Plaul

et al. 2015

The reduction of iron ore fines by means of fluidized bed technology has become an alternative route of ironmaking. To investigate the reduction behavior of fine ores and to improve fluidized bed processes, a lab scale fluidized bed facility is installed. The reactor is charged with different kinds of fine ores. The reactors get fluidized by a reducing gas mixture containing H2, H2O, CO, CO2, CH4, and N2 in variable range. Additionally, a sampling system is installed, which enables the sampling of bed material during reduction. All samples are analyzed regarding their grain size distribution, chemistry, and morphology. The comparison of the raw input ore with the reduced ore—bed samples during the tests and final material—leads to a new way of fine ore characterization. After the determination of a standardized process, globally traded iron ore fines are tested under the same process conditions. The results enable the validation of the morphological evolution of different iron ore types and brands (hematitic, magnetitic, and limonitic) during the reduction with CO‐rich reducing gas in fluidized bed processes. Further investigation on the structure and porosity of the different phases is done to evaluate the relation to reduction rate and final reduction degree.

“…In general, moderate temperatures for all tests were preferred, to enhance chemical reaction as the rate limiting step 21. In Figure 2a the process conditions of single‐stage tests and in Figure 2b the process conditions of two‐stage tests are depicted in reduction Diagrams 22.…”

Section: Methodsmentioning

confidence: 99%

“… Reduction Diagrams 22 for reduction tests at process conditions according to Table 2. (a) Single‐stage tests and (b) Two‐stage tests.…”

Section: Methodsmentioning

confidence: 99%

Experimental and Morphological Investigations of the Reduction from Coarse Hematite to Magnetite and Wüstite under Fluidized Bed Conditions

Weiss

Sturn

Voglsam

et al. 2010

Self Cite

For optimization of iron ore fines reduction processes, fundamental knowledge of the reduction kinetics under industrial operating conditions is required. Reduction tests with coarse hematite iron ore were performed in H2‐rich reduction gas atmospheres of H2, H2O, CO, CO2 and CH4 considering elevated pressures similar to industrial process conditions. The reaction kinetics of the reactions hematite to magnetite, magnetite to wüstite and hematite to wüstite were investigated in a laboratory‐scale pressurized fluidized bed reactor. To facilitate kinetic measurements, the laboratory‐scale fluidized bed reactor is equipped with a sampling system, which allows sampling of the bed material at operating conditions. Process conditions were chosen close to industrial plants in a temperature range from 400 to 700 °C. Significant influence of temperature on the rate of reduction was found in all tests. Variation of reduction gas composition showed no influence on the rate of reduction in the range of concentrations investigated. Results presented herein proved the feasibility of depicting industrial process conditions in laboratory scale. For the reduction of hematite to magnetite and magnetite to wüstite topochemical phase growth were observed. In the single step reduction of hematite to wüstite, magnetite appeared as intermediate product formed by topochemical reaction while progressive conversion of magnetite to wüstite was found.