• Energy Research

High reactivity coke is beneficial for achieving low carbon emission blast furnace ironmaking. Therefore, the preparation of highly reactive ferro-coke has aroused widespread attention. However, the effects of the particle size of iron ore on the pyrolysis behaviour of a coal-iron ore briquette are still unclear. In this study, the effect of three particle sizes (0.50–1.00 mm, 0.25–0.50 mm and <0.74 mm) of iron ore on the thermal and kinetic behaviours of coal-iron ore briquettes were investigated by non-isothermal kinetic analysis. The results showed that the synergistic effect of iron ore and coal during coking mainly occurred during the later reaction stage (850–1100 °C) and smaller particle sizes of iron ore have a stronger synergistic effect. The addition of iron ore had little effect on T0 (the initial temperature) and Tp (the temperature at the maximum conversion rate) of briquette pyrolysis, however itgreatly affected the conversion rate and Tf (the final temperature) of the briquettes. T0 decreased with the decrease of iron ore particle sizes, while Tp and Tf showed opposite trends. After adding iron ore into the coal briquette, the reaction kinetics at all stages of the coal-iron ore briquettes changed. The weighted apparent activation energy of the caking coal (JM) briquette was 35.532 kJ/mol, which is lower than that of the coal-iron ore briquettes (38.703–55.627 kJ/mol). In addition, the weighted apparent activation energy gradually increased with decreasing iron ore particle sizes.

The imperative to achieve a climate-neutral industry necessitates CO2-free alternatives for H2 production. Recent developments suggest that plasma technology holds promise in this regard. This study investigates H2 production by methane pyrolysis using a lab-scale plasma furnace, with the primary objective of achieving a high H2 yield through continuous production. The plasma furnace features a DC-transferred thermal plasma arc system. The plasma gas comprises Ar and CH4, introduced into the reaction zone through the graphite hollow cathode. The off-gas is channeled for further analysis, while the plasma arc is recorded by a camera installed on the top lid. Results showcase a high H2 yield in the range of up to 100%. A stable process is facilitated by a higher power and lower CH4 input, contributing to a higher H2 yield in the end. Conversely, an increased gas flow results in a shorter gas residence time, reducing H2 yield. The images of the plasma arc zone vividly depict the formation and growth of carbon, leading to disruptive interruptions in the arc, hence declining efficiency. The produced solid carbon exhibits high purity with a fluffy and fine structure. This paper concludes that further optimization and development of the process are essential to achieve stable continuous operation with a high utilization degree.

This paper is devoted to studying the thermochemical properties of carbon sources (laboratory-scale conventional coke, biocoke with 5 wt.%, and 10 wt.% wood pellet additions) and the influence of these properties on foamy slag formations at 1600 °C. Thermogravimetric analysis (TGA) conducted under air unveiled differences in mass loss among carbon sources, showing an increasing order of coke < biocoke with 5 wt.% wood pellets < biocoke with 10 wt.% wood pellets. The Coats–Redfern method was used to calculate and reveal distinct activation energies among these carbon sources. Slag foaming tests performed using biocoke samples resulted in stable foam formation, indicating the potential for biocoke as a carbon source to replace those conventionally used for this process. Slag foaming characters for biocoke with 5 wt.% wood pellets were improved more than coke. Using biocoke with 10 wt.% wood pellets was marginally worse than coke. On the one hand, for biocoke with 5 wt.% wood pellets, due to increased reactivity, the foaming time was reduced, but it was sufficient and optimal for slag foaming. Conversely, biocoke with 10 wt.% wood pellets reduced foaming time, proving insufficient and limiting the continuity of the foaming. This study highlights that thermochemical properties play a significant role, but comprehensive assessment should consider multiple parameters when evaluating the suitability of unconventional carbon sources for slag foaming applications.

This paper investigates the influence of biochar, either as an individual component or in combination with high-temperature coke, on the slag foaming behavior. High-temperature coke serves as a reference. Three scenarios were considered to study the slag foaming behavior, each characterized by different slag chemical compositions. The results indicate that biochar can promote steady foaming for specific slags when the basicity (CaO/SiO2) falls within a range of 1.2 to 3.4. Experimental findings also reveal that stable foaming can be achieved when a mixture containing biochar and coke with a ratio of 1:1 is employed, with a minimum slag basicity of 1.0 and FeO content of 25 wt.%. The foaming range obtained using different FeO contents (15 wt.% to 40 wt.%) in the mixture surpasses the range observed with the individual application of coke or biochar. The X-ray diffraction (XRD) analysis showed that unrelated to the carbon source applied, the general pattern was that the phases larnite (Ca2SiO4) or dicalcium silicate were detected for slag foams with high basicity. Monticellite (CaMgSiO4) and magnesium iron oxide (Fe2MgO4) were predominant in slag foam samples, with the highest MgO content. The presence of monticellite and merwinite (Ca3MgSi2O8) occurred in samples with the lowest basicity. Eventually, the application of the mixture of coke and biochar showed the potential to obtain stable foaming across a wide range of slag compositions.

Abstract Adding 5 mass% wood pellets in a coal blend affects the reactivity with CO2 and microstructural properties of the coke at different final coking temperatures of 950 and 1100 °C. A correlation between coke reactivity index (CRI) and BET specific surface area was found. The reactivity of coke and biocoke decreases with a decrease in the specific surface area, as well as with an increase in the carbonization temperature. Raman spectroscopy results indicate that the higher carbonization temperature of biocoke mitigates the effect of 5 mass% of biomass addition. The X-ray diffraction-based interlayer spacing of carbon crystallite (d002) decreases slightly with increasing carbonization temperature, and crystallite height (Lc) increases with rising coking temperature for both coke and biocoke. Additionally, the lower the d002 value, the lower the CRI of the cokes and biocokes. A good correlation between CRI and d002 is observed. Carbon crystallite width (La) values increased with a rising carbonization temperature, indicating the intensive growth of carbon crystallites in all directions. However, these values for biocokes are lower due to the presence of charcoal particles.

In order to use pellet feed, particularly iron ore with size distributions from 10 to 100 µm, in fluidized bed reactors, different binding systems for an agglomeration are evaluated. The micro agglomerates differ from each other in chemical compositions, contents, and thermal treatments. Crucial indicators for an application in a fluidized bed are reducibility as well as compressive strength. In pressure thermo gravimetric analyzer tests, micro agglomerates with lime hydrate and acid binder show the best reduction behavior, whereas micro agglomerates with inorganic binding systems reached the highest compressive strength before and after a three-step reduction process.

In this article, the impact of conventional carbon sources, alongside potential carbon bio‐sources, on slag‐foaming behavior is investigated. It highlights the complex relationship between these carbon sources and their properties, such as fixed carbon (FC), volatile matters (VMs), mineral composition in ash, reactivity, and wetting, which ultimately influence the slag foaming efficiency. The challenges associated with biochar and the significant differences in foaming behavior are addressed. For biochar to achieve effective slag foaming, it is essential that it contains an FC of at least 60 wt% and ash of less than 5 wt%. Though less impactful than CO generation from iron (II) oxide reduction, VMs from carbon sources, especially with high‐VM biochar, show secondary effects on reaction courses. The disadvantages associated with the high reactivity of biochar can be overcome by improving its physicomechanical and physicochemical properties. Despite the potential of biochar–coke mixtures to benefit slag foaming without enhancing biochar properties directly, challenges such as biochar floatation on the liquid slag surface and rapid burn‐off exist. Biocoke offers foaming results comparable to those of conventional sources. Despite the benefits of biocoke over other carbon sources, the review underscores its relatively unexplored status in the context of slag‐foaming applications.

The influence of different carbon sources, including anthracite, calcined petroleum coke, three samples of high-temperature coke, biochar, and a mixture of 50 wt.% biochar and 50 wt.% coke, on slag foaming behavior was studied. The slag’s composition was set to FeO-CaO-Al2O3-MgO-SiO2, and the temperature for slag foaming was 1600 °C. The effect of the carbon sources was evaluated using foaming characteristics (foam height, foam volume, relative foaming height, and gas fraction), X-ray diffraction (XRD), chemical analysis of the slag foams, Mossbauer spectroscopy, observation by scanning electron microscope (SEM), and energy-dispersive spectroscopy (EDS) mapping. Different foaming phenomena were found among conventional sources, biochar as a single source, and the mixture of coke and biochar. Biochar showed the most inferior foaming characteristics compared to the other studied carbon sources. Nevertheless, the slag foaming process was improved and showed slag foaming characteristics similar to results obtained using conventional carbon sources when the mixture of 50 wt.% coke and 50 wt.% biochar was used. The XRD analysis revealed a difference between the top and bottom of the slag foams. In almost all cases, a maghemite crystalline phase was detected at the top of the slag foams, indicating oxidation; metallic iron was found at the bottom. Furthermore, a difference in the slag foam (mixture of coke and biochar) was found in the presence of such crystalline phases as magnesium iron oxide (Fe2MgO4) and magnetite (Mg0.4Fe2.96O4). Notwithstanding the carbon source applied, a layer between the foam slag and the crucible wall was found in many samples. Based on the SEM/EDS and XRD results, it was assumed this layer consists of gehlenite (Ca2(Al(AlSi)O7) and two spinels: magnesium aluminate (MgAl2O4) and magnesium iron oxide (Fe2MgO4).

Pulverized coal injected into a blast furnace (BF) burns incompletely in a very limited amount of time. A considerable amount of unburned pulverized coal (UPC) escapes from the raceway to the coke layer. The unburned pulverized coal reacts with CO2 in the coke layer, and this has a very significant impact on the operation of the BF. The gasification reaction characteristics of the UPC with CO2 were assessed by thermogravimetric analysis. The microstructure and specific surface area of the pulverized coal and UPC were characterized by scanning electron microscopy (SEM), and a specific surface area testing apparatus together with the Brunauer-Emmett-Teller (BET) method, respectively. The results showed that Qingding UPC requires a higher temperature to complete the gasification reaction. At the same heating rate, the Tm (maximum reaction rate temperature) of the Shenhua UPC is much lower and the reaction rate is larger than those of the Qingding UPC. An increased heating rate is beneficial for the gasification reaction of the two UPCs. The kinetics analysis results showed that the optimal mechanism function models for the Shenhua and Qingding UPCs are chemical reaction models. The apparent activation energies of gasification of the Shenhua UPC and Qingding UPC under different conditions were 269.89–223.41 KJ/mol and 266.70–251.54 KJ/mol, respectively.