To investigate the evolution of inclusions in high‐Al steel with addition of La, a series of laboratory experiments and thermodynamic calculations are performed, considering the reaction time and amount of La added. The main inclusions in the high‐Al steel without the addition of La are Al2O3, MnS, and Al2O3–MnS. The La treatment can efficiently modify Al2O3 to La–Al–O or La–O–S inclusions. For La additions less than 0.0041 wt%, the evolution route for the inclusion in high‐Al steel is Al2O3 → LaAl11O18 → LaAlO3 with an increase in reaction time. For high La additions, the evolution route for the Al2O3 inclusion is Al2O3 → LaAl11O18 → LaAlO3 → La2O2S → La2S3. The experimental results correlate with those of the thermodynamic analysis. Notably, excess La in high‐Al molten steel may consume O and S to form La oxysulfide and sulfide, respectively, which prevents the precipitation of MnS inclusion and promotes the formation of AlN inclusion during solidification.

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The metallurgical properties and the microstructure of coke after gasification reaction with pure H2O and pure CO2 were investigated in this study. Moreover, the first-principles calculation was conducted to study the reaction process of the carbon with pure H2O and pure CO2. The results show that the CRI (coke reaction index) increases sharply and the CSR (coke strength after reaction) decreases sharply, when the cokes are gasified with H2O as compared to CO2. The scanning electronic microscopy images and the coke panoramagrams show that H2O more easily leads to the generation of large pores (>500 μm) and destroys the coke structure than CO2. The X-ray diffraction results indicate that the arrangement of carbon atoms of coke becomes regular and the ordered degree of coke increases after reaction with CO2 and H2O; however, after being gasified with H2O, the cokes have a higher ordered degree than with CO2. The results of the first-principles calculation show that the H2O molecule is more likely to react with carbon as compared to the CO2 molecule due to the lower energy barriers of H2O adsorption and H2 formation. The M2 → FS reaction process is the controlled step of the C-H2O reaction process, as well as in the C-CO2 reaction system.

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The briquette volume evolution during the coking process is very important for the operation and health of a coke oven. The strength and CO2 gasification of formed ferro-coke determine its utilization as well as its effects on the blast furnace status. To enhance ferro-coke better performance during fabrication and utilization, a better understanding of the influence of iron minerals on the volume, strength, and CO2 gasification of ferro-coke is necessary. This study investigated the effects of different iron mineral fines (oolitic hematite, hematite, and limonite) on the volume evolution of blended briquettes (iron ore and coal) during the carbonization process using thermal-platform microscopy. Drum tests, diametral compression tests, and gasification tests were conducted on the formed ferro-coke. The microstructure and crystal structure of ferro-coke were characterized using SEM and XRD, respectively. This study reveals that the iron mineral type has little effect on the swelling behavior of blended briquettes but will strongly suppress the shrinkage behavior of the briquettes during the coking process, especially in the case of high iron mineral additions. The added amount of iron mineral has a greater influence on the volume change than does the iron mineral type. With increasing amounts of iron mineral, the strength of the ferro-coke strongly decreases. The impact of hematite, limonite, and oolitic hematite on the strength of formed ferro-coke gradually becomes weak. The influence of iron mineral on the gasification of formed ferro-coke decreases from hematite to oolitic hematite to limonite. The type and added amount of iron mineral fine have no influence on the gasification mechanism of ferro-coke. The minimum weighted mean activation energy of ferro-coke prepared by hematite contributes to its highest gasification reactivity.

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