Energy-Saving and Emission Reduction in Metallurgy

KR (Kanbara Reaction) desulfurization slag is a solid waste that is not sufficiently utilized. This is because the KR desulfurization slag contains 1–2.5% sulfur, which is directly used in steel smelting to increase the sulfur content in molten steel. Therefore, the possibility of oxidation desulfurization of KR desulfurization slag was studied in this study. Experiments were conducted to investigate the possibility of removing sulfur from used KR (Kambara Reaction) slag with oxidation. The KR slag samples were treated with oxidative desulfurization in the oxygen partial pressure range of 0.05 bar–1.00 bar, with a gas flow rate ranging from 2 L min⁻¹ to 6 L min⁻¹, and at a temperature of 1420 °C. X-ray diffraction (XRD), an infrared carbon sulfur analyzer, and scanning electron microscopy–energy dispersive X-ray spectrometry (SEM–EDS) analysis were used to reveal the oxidative desulfurization mechanism of KR desulfurization slag. At low oxygen pressure ($P_{{\mathrm{O}}_2}$ < 0.20 bar), the desulfurization rate of slag oxidized for 120 min increased with the increase in oxygen partial pressure. At high oxygen pressure ($P_{{\mathrm{O}}_2}$ ≥ 0.20 bar), the desulfurization rate of slag samples did not change with the change in oxygen partial pressure, and the desulfurization rate was higher than 93.5%. At low oxygen pressure ($P_{{\mathrm{O}}_2}$ < 0.20 bar), the residual sulfur in the slag after oxidation still existed in the slag as the CaS phase. At high oxygen pressure ($P_{{\mathrm{O}}_2}$ ≥ 0.20 bar), the residual sulfur in the slag oxidized from the CaS phase to the 11CaO·7Al₂O₃·CaS phase in the slag. The sulfur removal rate was directly correlated with the slag surface area and the flow rate of the reaction gas, and it increased with an increase in both surface area and gas flow rate. Full article

According to physical property tests of lead-containing slag, the volatilisation behaviour of lead slag will have adverse impacts on test accuracy and further affect the control of chemical reactions, solidification and removal of inclusions during smelting. To analyse the volatilisation characteristics of lead slag, in this paper, four kinds of lead slags from lead direct reduction smelting with different PbO and ZnO content are taken. thermogravimetry, ISP-TOF were used. Additionally, the changes in volatiles and slag composition and phases were analysed with XRD and ICPS, and the volatilisation reaction mechanism was discussed. The results indicated that the volatilisation of lead slag can lead to a big weight loss of about to the slag with higher PbO content. The weight loss increases with the PbO content in slag increases. The volatile corresponding to the weight loss above 900 °C is mainly PbO and less ZnO. The higher the temperature is, the stronger the volatilisation is. With the increase in temperature and keeping time, most of the PbO can be evaporated and leaves little PbO in the residual slag. This will has great effect to physico-chemical property measurement of the slag with higher PbO content, especially to the property measurement that be kept at high temperature for a long time. Because the volatiles is trend to condense with the temperature decrease, mass spectrometer is limited by the condensation of volatiles, i.e., PbO, ZnO and so on, in the connection pipeline. The device should be modified for this use. Full article

The EU steel industry accounts for a crude steel production of 140 Mt/y, provided by the integrated (57%) and electric (43%) routes, which respectively require up to 6.0 and 0.6 MWh/t_CrudeSteel of energy input, and emits on average 1.85 and 0.4 t_CO2/t_CrudeSteel. The mitigation of such CO₂ emissions is crucial, and would involve the direct avoidance of carbon, improvement of energy efficiency, and carbon capture. However, the environmental burden of the steel industry cannot be limited to this, given the very large amount (approximately 5 Mt) of residues landfilled every year in the EU. This practice cannot be sustained anymore, since it represents a detrimental waste of resources and burden to the environment. These aspects require prompt action to meet the Green Deal goals envisioned for 2030. This review paper aims to provide an overview of the main state-of-the-art technologies commercially (and not) available for the effective treatment of a wide variety of residues. To enrich this overview with further potential candidates towards a more sustainable steel manufacturing process, the combined application of two technologies (a plasma reactor and a RecoDust unit for the recovery of metals and minerals, respectively) at TRL 5-6 is also investigated here. Full article

Based on the three-dimensional (3D) steady-state CFD numerical simulations conducted previously on an industrial Kalugin top combustion hot blast stove, a two-dimensional (2D) transient CFD numerical model for a single channel (hole) of a column of checker bricks in the regenerator of the same hot stove was established in the present work. The average mass flowrate and temperature of the flue gas flowing into the checker brick holes during the combustion period predicted by the 3D model were used as the inlet boundary conditions of the 2D model. Inside the hole of the checker bricks, processes of fluid flow and heat transfer of the flue gas during the combustion period and those of cold air during the hot-air-supply period were simulated using the 2D model for multiple operation cycles (combustion and hot-air-supply periods) of the hot stove, enabling rapid predictions of hot-air temperature under different operating conditions. The simulation results show that when the fuel gas flowrate and air consumption coefficient during the combustion period are controlled within the range of 80,000–100,000 Nm³/h and 1.02–1.28, respectively, a hot-air temperature in the range from 1273 °C to 1295 °C can be obtained during the hot-air-supply period. Applying this optimized operating condition to the industrial hot stove investigated in this study can achieve significant effects of reducing fuel gas flowrate by 8.6% and increasing hot-air temperature by 32 °C. In addition, a regression analysis on the numerical simulation results and the data measured from the industrial hot stove yields a roughly linear relationship between the dome temperature during the combustion period and the hot-air temperature during the hot-air-supply period, that is, the hot-air temperature would be increased by about 16 °C for every increment of 10 °C in the dome temperature, for instance. Therefore, the influences of the operating parameters on heat transfer characteristics in the regenerator and on hot-air temperature obtained in the present work provide a useful reference for guiding the hot stove operation optimization to achieve significant energy saving and emission reduction through facilitating more efficient combustion to minimize fuel gas consumption in steel plants. Full article

Blast furnace ironmaking is one of the most serious carbon dioxide emission processes. To reduce energy consumption and CO₂ emissions, fluidized bed ironmaking technology with hydrogen as a reducing agent has attracted more and more attention. An inclined agitator was added to the fluidized bed reactor to address the sticking issue in the conventional fluidized bed ironmaking process. In this research, numerical simulation was used to examine the impacts of reducing gas composition and agitation speed on the gas-solid fluidization quality in the cold fluidization of iron ore powder in the fluidized bed with an inclined agitator. The results indicate that the fluidization effect of iron ore powder is better when the volume ratios of H₂ to CO and H₂ to N₂ are 1:1. Under the intensive shear action of the agitator, the standard deviation of pressure drop constantly decreases with the increase in agitation speed, and the decreasing range is smaller and smaller. The fluidization state of the iron ore powder particles in the bed stabilized when the agitation speed reached 160 rpm. Full article

Aiming at the melt splashing behavior in the smelting process of an oxygen-enriched side-blowing furnace, the volume of fluid model and the realizable $k$−$\epsilon$ turbulence model are coupled and simulated. The effects of different operating parameters (injection velocity, immersion depth, liquid level) on splash height are explored, and the simulation results are verified by water model experiments. The results show that the bubbles with residual kinetic energy escape to the slag surface and cause slag splashing. The slag splashing height gradually increases with the increase in injection velocity, and the time-averaged splashing height reaches 1.01 m when the injection speed is 160 m/s. Increasing the immersion depth of the lance, and the slag splashing height gradually decreases. When the immersion depth is 0.12 m, the time-averaged splashing height is 0.85 m. Increasing the liquid level is beneficial to reduce the splash height, when the liquid level is 2.7 m, the splash height reduces to 0.77 m. With the increase in the liquid level, the slag splashing height gradually decreases, and the time-averaged splashing height is 0.77 m when the initial liquid level is 2.7 m. Full article

In the present study, the isothermal decomposition of austenite to bainite in 1.0 wt% carbon, 0.21% silicon steel during the partitioning step of a quenching and partitioning (Q&P) heat treatment has been investigated in a dilatometer in the temperature range of 200 to 350 °C and compared to conventional austempering heat treatment. The bainite transformation was shortened by about 75% in the presence of pre-existing martensite (QP). The kinetics of bainite transformation is described by the well-known Avrami equation. The calculated parameter ‘n’ in the Avrami equation shows that bainite forms in the absence of pre-existing martensite (TT) at a constant nucleate rate, while in the presence of pre-existing martensite, nucleation is interface controlled. The overall bainite transformation activation energy, calculated by the Avrami equation, ranges from 64 to 110 kJ/mol. The outcomes of this investigation provide guidelines for the development of multiphase microstructures, including pre-existing martensite and bainite in high-carbon low-silicon steel, within an industrially acceptable time scale and mechanical performance. Full article

It is important to clarify the reaction behavior of 2CaO·SiO₂ (C₂S) during hot metal dephosphorization. In this study, C₂S was prepared and added to steel slag to investigate the reaction of C₂S particles with CaO–SiO₂–FeO–P₂O₅ slag at 1723 K. The diffusion coefficient of phosphorus in C₂S was calculated. In addition, the influence of the addition of BaO to C₂S was discussed. The results show that the diffusion coefficient of phosphorus in C₂S is 9.23 × 10⁻¹⁴ m²·s⁻¹. The Ca in C₂S can be replaced by Ba. Small particles in the solid solution were easily generated from the C₂S body by the addition of BaO, which is beneficial for improving the phosphorus partition between the C₂S solid phase and the liquid phase of the slag. Full article