As a type of industrial solid waste with huge emission and heap stock, high-aluminum pulverized coal ash has a significant negative impact on resources and the environment. At the same time, as a secondary resource, its aluminum content can reach 50%, which is close to that of medium-grade bauxite; thus, it can be used as a substitute for bauxite resources. We propose a new method for extracting aluminum from fly ash via leaching. By designing the thermal reaction system of the molten brine, high-purity hydroxyl sodalite (90.2%) was prepared from fly ash. In this study, aluminum and other valuable elements were extracted using a hydrochloric acid leaching method from prepared high-purity hydroxyl sodalite in the form of ions by converting fly ash into a fixed hydroxyl sodalite solid product system. The major factors affecting the leaching rate are the hydrochloric acid concentration, liquid–solid product quality ratio, reaction temperature, and reaction time. Through analysis and calculation, within the scope of study, the leaching rate of aluminum reached more than 90%. The optimal experimental conditions are a leaching concentration of 1.5 mol/L, a liquid–solid volume–mass ratio of 20, a leaching time of 120 min, and a leaching temperature of 85 °C. Aluminum exists in the leaching solution in the form of Al³⁺, while the silica is partly dissolved in the hydrochloric acid solution; the other part remains in the solid phase as the main part of the hydrochloric acid leaching residue in the form of silica gel. In addition, this method not only can treat high-alumina fly ash, but also can be applied to other types of fly ash.

The sulfur content of hot metal in a blast furnace is an important index that reflects the production effects and quality of the hot metal. Establishing an accurate prediction model for hot metal sulfur content can guide the production process. In the present study, the blast furnace production data were collected and then preprocessed using box plotting. Cross-validation was used in the training process of the model to improve the generalization performance and robustness of the model. Two models for predicting the sulfur content in hot metal were established based on extreme gradient boosting (XGBoost) and multilayer perceptron (MLP) algorithms. The results show that coal consumption (CC), coal ratio (CLR), and sinter consumption (SC) are all positively correlated with hot metal sulfur content. The oxygen enrichment rate (OER) was negatively related to hot metal sulfur content. Both the extreme gradient boosting (XGBoost) and multilayer perceptron (MLP) models predicted hot metal sulfur content effectively; however, the extreme gradient boosting (XGBoost) model had a higher hit rate, accuracy, and stability, with the hit rate achieving 95.07%.

In this study, SiO₂–Al₂O₃–CaO–MgO steel slag ceramics containing 5 wt % MgO were used for the preparation of ceramic bodies, with the replacement of 5–20 wt % quartz and feldspar by fly ash. The effect of the addition of fly ash on the sintering shrinkage, water absorption, sintering range, and flexural strength of the steel slag ceramic was studied. Furthermore, the crystalline phase transitions and microstructures of the sintered samples were investigated by XRD, Fourier transform infrared (FTIR), and SEM. The results showed that the addition of fly ash affected the crystalline phases of the sintered ceramic samples. The main crystal phases of the base steel slag ceramic sample without fly ash were quartz, diopside, and augite. With increasing fly ash content, the quartz diffraction peak decreased gradually, while the diffraction peak intensity of anorthite became stronger. The mechanical properties of the samples decreased with the increasing amount of fly ash. The addition of fly ash (0–20 wt %) affected the optimum sintering temperature (1130–1160 °C) and widened the sintering range. The maximum addition amount of fly ash should be 15 wt %, for which the optimum sintering temperature was 1145 °C, water absorption was 0.03%, and flexural strength was 43.37 MPa higher than the Chinese national standard GBT 4100-2015 requirements.

A new tuyere small sleeve coating structure that balances the high thermal conductivity of the copper substrate with the high wear resistance of the protective layer was developed in this paper. This structure can achieve a low-carbon blast furnace by reducing the heat loss from the tuyere. The 3D model was established via Solidworks for modeling and Ansys for numerical simulation, the temperature field of the annular wear-resistant layer structure tuyere small sleeve with different widths of the wear-resistant layer was analyzed and compared with the temperature and stress field of traditional tuyere small sleeve. The results show that the design of the annular wear-resistant layer structure of the tuyere small sleeve is more effective. The new annular wear-resistant layer structure for the tuyere small sleeve results in a decrease of 24 K in the average temperature of the wear-resistant coating. The comparison of this structure with tuyere sleeves without wear-resistant coatings shows a 16.7% reduction in heat loss, improves the wear resistance of the tuyere, providing new technological ideas for low-carbon blast furnace production. Compared with the tuyere sleeve completely covered with a wear-resistant coating, the maximum thermal stress of this structure decreased from 624.98 Mpa to 427.99 Mpa, resulting in a reduction of 31.5%, which is beneficial for the service life of the tuyere sleeve. The copper surface temperature of the new tuyere small sleeve is in a safe range when the temperature is below 2273 K.

Steel slag, clay, quartz, feldspar, and talc were mixed to prepare steel slag ceramics. Crystalline phase transitions, microstructures, and the main physical-mechanical properties (water absorption, linear shrinkage, and flexural strength) of steel slag ceramics for various MgO/Al₂O₃ ratios were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and mechanical testing. The results indicated the significant effect of the MgO/Al₂O₃ ratio on these properties. A decrease in the MgO/Al₂O₃ ratio resulted in a major crystalline phase transformation from quartz and pyroxene phases to quartz and anorthite phases. High MgO content facilitated production of pyroxene phases. High Al₂O₃ content favored production of anorthite phases. The water absorption of all the samples (below 0.5%) met the Chinese national standard requirements. Samples with an MgO/Al₂O₃ ratio of 0.6 exhibited excellent flexural strength, reaching 62.20 MPa. FactSage software was used to predict batch viscosity, which increased with decreasing MgO/Al₂O₃ ratios.