Biomass hydrochar injection into blast furnace is one of the important research topics in the current low-carbon ironmaking process. However, its co-combustion behavior with anthracite in front of blast furnace tuyere and its CO2 emission reduction effect during blast furnace injection are still unclear. In this paper, the elemental composition, microstructure, specific surface area and carbonaceous structure order of biomass hydrochar and anthracite are characterized. The combustion and conversion process of biomass hydrochar and anthracite is studied by thermogravimetric analysis and reaction kinetics model. The results show that compared with anthracite, biomass hydrocahr has the characteristics of higher volatile content, larger specific surface area and lower carbonaceous structure order. With the increase of the biomass hydrochar addition, the combustion curve of the mixture gradually moved to the high temperature region, and the R0.5 increased from 1.53 x 10- 4 to 2.98 x 10-4 s- 1. Among them, the linear relationship between carbonaceous structure order and R0.5 has the highest fitting degree. The Flynn-Wall-Ozawa (FWO) model has a high fit grade, with a maximum activation energy of 195.82 kJ/mol, and the corresponding biochar addition amount is 80 %. Using a mixture of hydrochar (60 %) and anthracite (40 %) in blast furnace injection process can reduce CO2 emissions by about 247.13 kg/tHM. Therefore, the addition of biomass not only effectively promotes the combustion of anthracite, but also achieves the reduction of CO2 emissions.

In this paper, the characteristics of low-rank coal for blast furnace injection after hydrothermal carbonization treatment was studied. The impact of the hydrochar injection on human health, energy, environment and other factors was discussed through the life cycle assessment method. Compared with pulverized coal injection, the hydrochar can improve the sustainability of the ecosystem and the healthy development of human beings. The impact on human health dropped from 24.61Pt to 23.73Pt, the ecosystem dropped from 0.53Pt to 0.51Pt, and the energy utilization rate dropped from 0.31Pt to 0.3Pt. Human carcinogenic toxicity, global warming, freshwater ecotoxicity and mineral resource scarcity are the most significant impacts. After using hydrochar, due to the increase of heat in front of the tuyere raceway and the improvement of pulverized coal utilization, the effects of optimizing coal gas flow distribution, improving reduction efficiency and strengthening smelting are achieved, thus reducing the impact of toxicity and greenhouse effect. Changes in freshwater ecotoxicity are mainly related to the sintering process and chemical reactions. The injection of hydrochar can make a positive contribution to the impact of ore resources. Moreover, the uncertainty analysis results show that the accuracy of the current model calculation can eliminate potential error risks. Thus, the application of hydrochar provides a better solution for the innovative, sustainable development and low-carbon production of iron-making process.

Large quantities of polyvinyl chloride (PVC) and waste tires generated daily have the disadvantage of high content of harmful elements. They cannot be directly applied to blast furnace ironmaking. In this study, Cl in PVC and Zn in pyrolysis products of waste tires (pyrolysis carbon black, CB) were effectively removed by co-hydrothermal carbonization (co-HTC). The results indicated the dechlorination and dezincification efficiencies of co-HTC were improved by 2.78 % and 64.69 %, respectively, compared to HTC. Compositional analysis shows that the ash content of co-HTC is reduced by at least 7.67 % compared to conventional HTC. The hydrochar produced by co-HTC has an higher heating value (HHV) ranging from 30.67 to 34.13 MJ/kg. Results of physical and chemical characteristics analysis showed increasing the proportion of CB can reduce the C–H and -CHCl- functional groups and improve the carbon orderliness of the hydrochar. Combustion characteristics and kinetic analyses show that the combustibility of hydrochar increases with an increase in the proportion of PVC added to the co-HTC. The thermal stability and activation energy of the hydrochar increase with the addition of CB. Overall, this study has removed major harmful elements from PVC and CB through co-HTC, converting both into high-quality solid fuels that can be utilised in blast furnace ironmaking.

The substitution of fossil coal with biocarbon in the metallurgical processes can help to decrease fossil CO₂ emissions. Biocarbon’s characteristics, such as high volatile matter contents and high reactivities with CO₂, are beneficial for increasing the reduction degrees and reduction rates of iron oxides in carbon composite agglomerates (CCA). This study compared the reduction of hematite by of two types of carbonaceous materials (CM): hydrochar (high-volatile biocarbon) and anthracite (a low-volatile coal) in the form of CCA. CM, hematite, and binder (starch) were mixed together to obtain mixtures with C/O molar ratios equal to 0.4–1.2. The mixtures were reduced non-isothermally in nitrogen atmosphere up to 1003 K or 1373 K. Up to 1003 K, the volatiles released from CMs and starch reduced hematite by 18–35%. Between 1003 K and 1373 K, both hydrochars (produced from lemon peels and rice husks) reacted with iron oxides more rapidly than anthracite below 1360 K, when the samples had C/O ratios in the range of 1.0–1.2. In this temperature range, rice husk hydrochar promoted a slower reaction with iron oxides than lemon peel hydrochar, which was possibly influenced by its higher ash content which decreased the rate of Boudouard reaction. Samples with C/O ≥ 1.0 achieved complete reduction at 1373 K, regardless of the type of CM used, whereas samples with C/O equal to 0.4–0.5 achieved 63–86% reduction. It can be concluded from this study that hydrochar can fully substitute anthracite for direct reduction of iron oxide to decrease fossil CO2 emissions during ironmaking processes.

As the sole carbonaceous renewable energy source, biomass is distinguished by its abundant yield, widespread distribution, and carbon neutrality. It is integral to the achievement of zero and negative carbon production via conventional carbonaceous pellet technology. This study introduces a cradle-to-gate life cycle assessment methodology for biomass preparation in carbonaceous pellets. We prepare high-quality biochar through a process combining hydrothermal carbonization and pyrolytic carbonization. Biomass high molecular weight extracts are obtained via organic pyrolytic extraction, while biomass high-temperature binders result from the modification and treatment of biochar. Biomass carbonaceous pellets are then formed using hot press technology. The ReCiPe model facilitates a comprehensive life cycle assessment of biomass carbonaceous pellets used in blast furnace production. The study leverages two comprehensive evaluation indicators - renewability, and environmental performance - to enhance the environmental performance of the process system and to maximize energy-saving and emission reduction potential.

In this study, we performed a comprehensive analysis of the molecular structural characteristics of low-rank coal and predicted its chemical properties. Using quantum chemistry and wave function analysis, we extensively discussed electrostatic potential surfaces, spectral characteristics, electronic structure, and orbital composition of coal. Our findings reveal that regions exhibiting negative electrostatic potential display increased reactivity during reactions. Oxygen-containing groups in coal molecules exhibit strong hydrophilicity upon interaction with water, primarily through medium-strength and weak hydrogen bonds. Hydrophobic sites are predominantly located near the aliphatic side chains and aromatic core groups of the coal molecules. Additionally, oxygen and carbon atom orbitals dominate regions of lower energy density, correlating with volatile substances that undergo initial decomposition during coal heating. These results provide fundamental insights into the physical and chemical properties of low-rank coal from a molecular perspective.

The metallurgical industry is a key sector for carbon emissions, and in recent years, there has been widespread attention on the use of biomass resources as a green, renewable, and carbon–neutral energy source material for low carbon ironmaking processes. The waste wood after hydrothermal-pyrolysis carbonization has the characteristics of low content of harmful elements and high content of fixed carbon. In this study, the waste wood after hydrothermal-pyrolysis two-step carbonization treatment was used as a reducing agent for the reduction of iron ore to prepare iron ore powder- green carbon composite briquettes (ICCB) with two carbon–oxygen ratios. The study investigated the effects of reduction behavior and reaction temperature on the reduction performance of the ICCB. The results indicate that with the increase in reaction temperature, the volume of the ICCB gradually contracts, leading to a reduction in mass. The shrinkage rate of the ICCB during self-reduction at 1200℃ is significantly higher than during co-reduction, and the shrinkage effect of the C/O 0.5 ICCB is more pronounced than that of the C/O 0.8 ICCB. Due to the excessive carbon content in the C/O 0.8 ICCB, the carbon cannot be fully consumed during the reaction process, resulting in consistently low compressive strength of the ICCB, with a compressive strength of 12 N after reduction at 1200℃. In contrast, the iron phase in the C/O 0.5 ICCB gradually recrystallizes during the reduction process, ultimately yielding plastic iron briquettes with compressive strengths exceeding 3000 N after different reaction behaviors at 1200℃. In summary, reducing the carbon-to-oxygen ratio and increasing the reaction temperature contribute to the volume contraction and enhanced compressive strength of the ICCB during the reduction process.

Biocarbon will play an important role to achieve a carbon neutral and sustainable steel industry. In this study, three hydrochars (one type of biocoal produced via the hydrothermal carbonization process) derived from orange peel, green waste and rice husk were tested in a 10-ton test-bed EAF (electric arc furnace). These hydrochars were added to EAF via injection and top-charge as carburizer to substitute anthracite. The obtained liquid slag composition after scrap meltdown is favorable for the desulphrization process. Moreover, a higher carburization yield was achieved by top charging of hydrochar into EAF at the beginning of the heat. The final P and S of liquid steel with addition of hydrochars were controlled to acceptable levels. Some perspectives of using hydrochar for EAF steelmaking are also presented.

The low energy density of biomass is a crucial limitation for their application in the steel industry. This study used catalyst-catalysed hydrothermal carbonization (HTC) to prepare higher-quality hydrochar from biomass. The effects of acid-base homogeneous catalysts (Fe(NO3)3·9H2O and CaO), liquid phase product (circulating water) and carbonization temperatures on the physicochemical properties and microscopic morphology of hydrochars were investigated. The results showed that higher carbonization temperature, circulating water and Fe(NO3)3·9H2O all raised the higher heating value (HHV) of hydrochar. When 4% of Fe(NO3)3·9H2O was added, the HHV of hydrochar reached 30.05 MJ/kg, which was 1.15 times higher than without catalysts. The above three conditions can also make the ordering degree in the carbonaceous structure lower ordered and enhance the reaction performance of the hydrochar. Meanwhile, the addition of Fe(NO3)3·9H2O at 240 °C can reduce the hydrochar ignition and burnout temperatures and enhance the combustion performance. Moreover, it was demonstrated that circulating water promoted the HTC more than deionized water. In conclusion, adding Fe(NO3)3·9H2O or circulating water to the HTC process can produce higher-quality hydrochar.

Hydrothermal carbonization (HTC) technology upgrades combustible waste (CW) to high-quality fuel known as hydrochar. However, there is a research gap regarding the application limit of hydrochar instead of fossil fuels in blast furnaces. In this study, the physical, chemical, and metallurgical properties of hydrochar were thoroughly analyzed. The results showed that gross calorific value, grindability, ignition temperature, explosivity, combustion and gasification all improved by HTC process compared with the waste feedstocks. Moreover, the HTC process can effectively remove harmful elements (K, Na, Cl, and S) from feedstocks into liquid and gas phase without adding other reagents, reducing harmful effects in the blast furnace. Removal rates by HTC were >80% for alkali metals and >73.9% for Cl (reaching 98.18% for polyvinyl chloride hydrochar). The environmental benefit calculation shows that the CO2 emission reduction of replacing bituminous coal with 40% HTC-treated maize straw can reach 94.7 kg/tHM. The annual CO2 reduction can reach 1.7 x 107 kg and the annual coal reduction is 1.5 x 107 kg of a blast furnace. The results showed that hydrochar is a clean energy source compared with fossil fuel alternatives and meets the blast furnace injection requirements.