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Converter steel slag, currently underutilized crystalline metallurgical residue, was investigated for use as a precursor for alkali activation. Water glass solution with various moduli (0.5, 1.0, 1.5 and 2.0) was used at the same Na 2 O dosage of 4% in order to investigate effect of modulus on hydration. Pure cement paste with the same ratio of water to binder was selected as the control sample. Results show that modulus has a significant impact on the hydration and mechanical strength development of alkali-activated steel slag. Similar to pure cement paste, alkali-activated steel slag paste has C–S–H gel and Ca(OH) 2 as its main hydration products. However, alkali-activated steel slag pastes have lower hydration heat and fewer amounts of hydration products. Additional silicate has a retarding effect on the hydration of steel slag. Hydration heat, Ca(OH) 2 contents and non-evaporable water contents reduce with increasing modulus. In addition, high silicate modulus fines the pore structure and improves compressive strength of the hardened paste.

Chemical-looping combustion (CLC) is a combustion process with inherent separation of carbon dioxide (CO2), which is achieved by oxidizing the fuel with a solid oxygen carrier rather than with air. As fuel and combustion air are never mixed, no gas separation is necessary and, consequently, there is no direct cost or energy penalty for the separation of gases. The most common form of design of chemical-looping combustion systems uses circulating fluidized beds, which is an established and widely spread technology. Experiments were conducted in two different laboratory-scale CLC reactors with continuous fuel feeding and nominal fuel inputs of 300 Wth and 10 kWth, respectively. As an oxygen carrier material, ground steel converter slag from the Linz–Donawitz process was used. This material is the second largest flow in an integrated steel mill and it is available in huge quantities, for which there is currently limited demand. Steel converter slag consists mainly of oxides of calcium (Ca), magnesium (Mg), iron (Fe), silicon (Si), and manganese (Mn). In the 300 W unit, chemical-looping combustion experiments were conducted with model fuels syngas (50 vol% hydrogen (H2) in carbon monoxide (CO)) and methane (CH4) at varied reactor temperature, fuel input, and oxygen-carrier circulation. Further, the ability of the oxygen-carrier material to release oxygen to the gas phase was investigated. In the 10 kW unit, the fuels used for combustion tests were steam-exploded pellets and wood char. The purpose of these experiments was to study more realistic biomass fuels and to assess the lifetime of the slag when employed as oxygen carrier. In addition, chemical-looping gasification was investigated in the 10 kW unit using both steam-exploded pellets and regular wood pellets as fuels. In the 300 W unit, up to 99.9% of syngas conversion was achieved at 280 kg/MWth and 900 °C, while the highest conversion achieved with methane was 60% at 280 kg/MWth and 950 °C. The material’s ability to release oxygen to the gas phase, i.e., CLOU property, was developed during the initial hours with fuel operation and the activated material released 1–2 vol% of O2 into a flow of argon between 850 and 950 °C. The material’s initial low density decreased somewhat during CLC operation. In the 10 kW, CO2 yields of 75–82% were achieved with all three fuels tested in CLC conditions, while carbon leakage was very low in most cases, i.e., below 1%. With wood char as fuel, at a fuel input of 1.8 kWth, a CO2 yield of 92% could be achieved. The carbon fraction of C2-species was usually below 2.5% and no C3-species were detected. During chemical-looping gasification investigation a raw gas was produced that contained mostly H2. The oxygen carrier lifetime was estimated to be about 110–170 h. However, due to its high availability and potentially low cost, this type of slag could be suitable for large-scale operation. The study also includes a discussion on the potential advantages of this technology over other technologies available for Bio-Energy Carbon Capture and Storage, BECCS. Furthermore, the paper calls for the use of adequate policy instruments to foster the development of this kind of technologies, with great potential for cost reduction but presently without commercial application because of lack of incentives.

The disposal of waste oil, paint and coating barrels (WOPCBs) after use is an ongoing social and environmental problem. In this paper, a novel technological scheme using steel converter co-processing is proposed for the safe disposal and resource utilization of WOPCBs. The scheme is mainly composed of WOPCBs pretreatment and converter disposal, focusing on the impact of converter co-processing WOPCBs on the environment and production process. Compared to the traditional technology, the scheme presented takes full advantages of the production process and environmental protection facilities of steel converter, and has many advantages, such as a large disposal capacity, low cost, highly efficient and environmentally friendly. The industrial trials results show that after adding 180–540 kg WOPCBs to each furnace load (nominal capacity 250 t), the converter operation is safe and controllable, and all the pollutant emission indicators generated in the process meet the Chinese national standards. In addition, WOPCBs are suitable to be used as a supplementary material for scrap steel. Therefore, this study provides important insights for sustainable resource utilization from WOPCBs.

Hydrogen metallurgy is a technology that applies hydrogen instead of carbon as a reduction agent to reduce CO 2 emission, and the use of hydrogen is beneficial to promoting the sustainable development of the steel industry. Hydrogen metallurgy has numerous applications, such as H 2 reduction ironmaking in Japan, ULCORED and hydrogen-based steelmaking in Europe; hydrogen flash ironmaking technology in the US; HYBRIT in the Nordics; Midrex H 2 ™ by Midrex Technologies, Inc. (United States); H 2 FUTURE by Voestalpine (Austria); and SAL-COS by Salzgitter AG (Germany). Hydrogen-rich blast furnaces (BFs) with COG injection are common in China. Running BFs have been industrially tested by AnSteel, XuSteel, and BenSteel. In a currently under construction pilot plant of a coal gasification-gas-based shaft furnace with an annual output of 10000 t direct reduction iron (DRI), a reducing gas composed of 57vol% H 2 and 38vol% CO is prepared via the Ende method. The life cycle of the coal gasification—gas-based shaft furnace—electric furnace short process (30wt% DRI + 70wt% scrap) is assessed with 1 t of molten steel as a functional unit. This plant has a total energy consumption per ton of steel of 263.67 kg standard coal and a CO 2 emission per ton of steel of 829.89 kg, which are superior to those of a traditional BF converter process. Considering domestic materials and fuels, hydrogen production and storage, and hydrogen reduction characteristics, we believe that a hydrogen-rich shaft furnace will be suitable in China. Hydrogen production and storage with an economic and large-scale industrialization will promote the further development of a full hydrogen shaft furnace.

In top–bottom combined blown converter-steelmaking process, cavity shape created by oxygen jet of top lance impacting liquid metal surface and gas–liquid flow caused by bottom gas blowing play an essential role in its metallurgical efficiency. In present work, Eulerian-multifluid VOF with user‐defined functions (UDF) is adopted to study impact cavity shape and gas–liquid flow in top–bottom-blown converter, and effects of interphase force are investigated, containing drag force, turbulent dispersion force, and bubble-induced turbulence. Bubble-induced turbulence is added to the k-ε equation via UDF. The prediction ability of the optimized Eulerian-multifluid VOF is compared with that of the VOF-DPM. The simulation results of liquid velocity, impact cavity diameter, and depth are compared with experimental measurement data that are most accurately predicted with optimized Eulerian-multifluid VOF. The results show that drag force powerfully influences impact cavity shape, while turbulent dispersion force has less influence, but it dominates bottom-blowing flow direction. The stirring bath behavior can be adequately described by considering bubble-induced turbulence, and dispersed turbulence model exhibits a stronger capability than that of mixture turbulence model for prediction of liquid velocity. Top-blowing flowrate is more sensitive to the impact cavity shape than top lance height. Eulerian-multifluid VOF performs better prediction on gas–liquid two-phase flow than VOF-DPM.

Gas-metal-slag interaction with traditional oxygen lance and single-flow postcombustion (PC) lance is compared by fluid volume method (VOF). Then, the industrial trials are carried out in a 120-ton top-blown converter to evaluate their metallurgical effects. Simulation results indicate that oxygen jet is injected to the liquid bath, generating a cavity. The liquid bath appears to have an unstable flow condition. Compared with the traditional lance, the PC lance is more helpful for stirring and mixing of liquid bath. The cavity diameter and depth with the PC lance are increased by 5.8% and 4.3%, respectively. Additionally, an improved model is proposed, which considers the momentum superposition of secondary flow and modifies the value of K characterizing the velocity attenuation. Industrial tests show that many metallurgical properties have been optimized by the PC lance, for example, the blowing time shortens by 93 s, the dephosphorization rate increases by 1.67%, and the scrap ratio increases by 1.3%.

In 2023, China’s crude steel production amount reached 1.019 billion tons, and the energy consumption of China’s steel industry amount reached 561 million tons of coal. China’s steel industry, with its dominant reliance on coal for energy and the primary use of blast furnaces and converters in production processes, as well as its massive output, has become the main field for achieving China’s “carbon peaking” and “carbon neutrality” goals. Firstly, this article summarizes the current production status of the steel industry and the situation of carbon emissions in the steel industry. Secondly, it discusses the dual-carbon policies based on the national and steel industry levels and outlines the future directions for China’s steel industry. Subsequently, it analyzes the current state of research and application of mature and emerging low-carbon technology in China’s steel industry and details the low-carbon plans of China’s steel companies using the low-carbon technology roadmaps of two representative steel companies as examples. Finally, the article gives policy suggestions for the further carbon reduction of China’s steel industry. The purpose of this paper is to show the efforts and contributions of China’s steel industry to the early realization of its “carbon peaking” and “carbon neutrality” goals.

A regression model is developed for determining the carbon content in steel during oxygen injection in the converter. The model proves highly effective.

The basic oxygen furnace (BOF) is the dominating primary steelmaking process. It is an autothermal process where hot metal and scrap are used as charging materials. The decarbonization and transformation of integrated BOF steelmaking will be the most important challenge in the coming years. Steel scrap is a charge material without new CO2 emissions, whose availability is expected to grow significantly and will play a key role in this decarbonization process. Several solutions have been developed by Primetals Technologies to provide additional energy for processing higher scrap rates in integrated BOF steelmaking. Such solutions include simple upgrade packages installed on existing converters such as process models for heat optimization, post-combustion, and scrap preheating lances. For higher scrap rates from 30% to 50%, a combination blowing converter and JET converter is required to provide sufficient mixing during scrap melting and the highest heat transfer from the increased post-combustion. Hybrid EAF–BOF operation and limitations regarding scrap quality also need to be considered for the transformation of steelmaking. Scrap sorting and processing can be a solution to reduce residual levels in crude steel for high scrap rates. Based on reference plant data, the CO2 reduction potential of the presented solution versus the effort and complexity of implementation is compared.

The end-point determination of the slag- and copper-making periods in copper converting directly affects the quality of copper, stability of the furnace condition, and efficiency of converting. However, existing end-point determination methods such as manual experience, sampling analysis and detection, and flame image recognition have problems such as poor accuracy, high cost, and lagging judgment. In this paper, target detection is used to determine the end point of copper converting. By integrating the efficient-channel attention (EGA) mechanism and Res2Net module into the You-Only-Look-Once-v5s (YOLOv5s) target detection algorithm and using Alpha Intersection-OverUnion to replace the Intersection-Over-Union loss function, we constructed a copper-converting end-point determination model based on the YOLOv5sRes2Net-ECA collaboration. The results show that the high-temperature melt cooling image data from 11 time points during the blowing process of ten copper-converting furnaces were used as samples for training. Then, end-point determination prediction was carried out. Compared with YOLOv5s, the average accuracy of the constructed model was improved by 4.94%, reaching 89.25%. The average accuracy of the end-point determination of the slagmaking and copper-making periods was 97.4% and 98.4%, respectively. The results lay a foundation for the intelligent determination of the end point of copper converting.