Introduction
Sources | Method | Type of Reductants | Slag System | T (˚C) | E (kJ/mol) | Findings |
---|---|---|---|---|---|---|
Bafghi et al.[5] | ethylenediaminetetraacetic acid titration (EDTA) | graphite crucible | SiO2–CaO–Li2O–Al2O3–FeO FeO: 10 wt pct basicity: 1–2 | 1300 | — | the reduction rate is significantly influenced by the slag basicity. The reaction is controlled by mass transfer in the slag phase, when the basicity is 2, whereas the chemical reaction resistance is dominant at lower basicity |
Sarma et al.[6] | sensitive pressure transducer of CO evolution | graphite coke coal char | CaO–SiO2–Al2O3–FeO FeO: < 10 wt pct | 1400 to 1450 | — | the study claims that the reaction rate is non-lineraly dependent on the FeO contents in slag. The reduction rate could be improved by additional factors such as external stirring of the carbon rod, encouraging faster diffusion of FeO in slag |
Min et al.[7] | mass spectrometer technique | graphite rod | CaO–SiO2–Al2O3–FeO FeO: 1 to 70 wt pct | 1450 | 251 | the rate limiting step is dependent on the FeO content in slag. It is claimed that the gasification reaction could be the limiting step when the activity of FeO is higher than 0.5, whereas a mixed step of gasification reaction with mass transfer of FeO in liquid phase could be considered as the rate-determining step of the reaction at activity of FeO lower than 0.5 |
Soe and Fruehan[8] | constant volume pressure increase (CVPI) | coal chars | CaO–SiO2–FeO–Al2O3 FeO: 1&3 wt pct basicity: 1.2 | 1450 | — | the reduction of FeO is independent of the type of coal used regardless of the components ie., volatile matter and ash. The overall reduction rate is controlled by a series of processes such as liquid phase mass transfer of FeO in slag and gas phse mass transfer, gasification reaction, direct and indirect reaction between FeO, C, and CO |
Siddiqi et al.[9] | sessile drop technique IR CO-CO2 analyser | graphite substrate | SiO2–CaO–Al2O3–MgO–FeO FeO: 0.22 to 9.26 wt pct | 1500 to 1600 | 112.18 | the reduction rate is directly depending on the FeO wt pct in the molten slag and temperature |
Jouhari et al.[10] | slag chemical analysis | graphite crucible | CaO–MgO–SiO2–Al2O3–FeO FeO: 25 to 50 wt pct | 1550 \(\pm \) 25 | 153 | the reduction reaction follows 1st order reaction. The reaction rate is directly proportional to FeO concentration, temperature, and reaction surface area |
Teasdale and Hayes[11] | sessile drop technique | graphite coke bituminous coal anthracitic chars | FeO–CaO–Al2O3–SiO2 FeO: 10.5 wt pct | 1400 to 1600 | — | it is claimed that the reduction rate is influenced by the carbon type; faster reaction rate is achieved by graphite and coke than coal chars. The rate of reduction is controlled by mass transfer in the slag phase |
Bhoi et al.[12] | slag chemical analysis | graphite crucible | SiO2–CaO–Al2O3–MgO–Fe2O3 Fe2O3: 20 to 40 wt pct basicity: 1 to 1.8 | 1400 to 1600 | 118 | the reaction follows first order reaction, and the rate is increased with increasing FeO cotent in the slag, and temperature. Hence, the overall reduction is mainly controlled by liquid phase mass transfer of FeO |
Maroufi et al.[13] | IR gas analyser SEM–EDS | coke rubber-derived carbon (RDC) coke-RDC blend | Fe2O3–SiO2–Al2O3–CaO–MgO–MnO Fe2O3: 36.2 wt pct | 1550 | overall reduction rate is influenced by the gasification of carbonaceous material | |
Leuchtenmueller et al.[14] | XRF SEM/EDX ICP-OES spark spectrometer (SPECTROMAXX) | pig iron (liquid) | MgO–Al2O3–SiO2-CaO–FeO–ZnO | 1320 to 1475 | 216 (ZnO) 191 (FeO) | reduction kinetics model is developed for the carbothermic reaction rate of FeO and ZnO in liquid slag; assuming that the reaction mainly takes place within the metal-slag boundary. It is found that higher reduction rate of ZnO is achieved compared to FeO |
Khasraw et al.[15] | drop tube furnace coupled with a quadrupole mass spectrometer (DTF-QMS) X-ray Fluorescence (WDXRF) | thermal coal (TC) Charcoal (CC) Bana grass Char (BGC) | CaO–SiO2–Al2O3–MgO–FeO FeO: 6 wt pct | 1450 to 1525 | first stage: 290 (TC), 229 (CC), 267 (BGC) Second stage: 265 (TC), 369 (CC), 282 (BGC) | the overall reduction involves two stages: Chemical reaction at solid/gas interface is dominant during the first stage, whereas mixed control i e., gas diffusion, liquid phase mass transfer, chemical reaction, and carbon diffusion |
Yu et al.[16] | XRD SEM/EDS | graphite powder | CaO–SiO2–FeO–P2O5 FeO: 20, 33 wt pct P2O5: 5, 17 wt pct | 1300 | FeO reduction stopped within 1 h of reaction due to FeO existing in the C2S-C3P solid solution. In contrary, P2O5 is continuously reduced even after 7 h |
Experimental
Materials Preparation
CaO | SiO2 | Al2O3 | MgO | FeO |
---|---|---|---|---|
41.66 | 33.33 | 13.00 | 6.00 | 6.00 |
Sample | Proximate Analysis (Wt Pct) | Ultimate Analysis (Wt Pct) | ||||||
---|---|---|---|---|---|---|---|---|
Volatile | Fixed Carbon | Ash | H | O | N | S | C | |
CC | 12.1 | 81.5 | 1.8 | 3.1 | 6.9 | 0.57 | 0.1 | 89.4 |
TC | 22.2 | 60.1 | 8.8 | 4.3 | 11.4 | 2.2 | 0.2 | 81.9 |
Elemental Carbon | Ash Content | Organic | ||||
---|---|---|---|---|---|---|
CB | > 97 pct | < 1 pct | < 1 pct |
Apparatus
Experimental Procedure
Results and Discussion
Off-Gas Analysis
Kinetic Study
Kinetic models
Model fitting
Reductants | Temperature (°C) | Avrami_Erofeev Model (Region I) | Three-Dimensional Diffusion Model (Region II) |
---|---|---|---|
k (s−1 × 10–3) | k (s−1 × 10–5) | ||
CC | 1450 | 3.1 | 7.5 |
1475 | 3.3 | 9.0 | |
1500 | 3.4 | 10.0 | |
TC | 1450 | 2.8 | 3.0 |
1475 | 3.2 | 5.0 | |
1500 | 3.3 | 7.0 | |
CB | 1450 | 2.6 | 5.5 |
1475 | 2.8 | 6.5 | |
1500 | 3.1 | 7.0 |