•Carbonation pathways and carbon capture mechanisms of steel-making slags were summarized.•Effects of carbonation pathways on the carbonation capacity of steel-making slags were ...evaluated.•Carbonation products obtained from different carbonation pathways were analyzed and compared.•Scale-up applications and main challenges of steel-making slags carbonation technology are summarized and prospected.
With the rapid development of economy and industrialization, the consumption of natural resources has risen sharply. A large number of greenhouse gases and industrial solid waste emissions have exacerbated global warming, resulting in a series of environmental degradation problems. Using natural minerals or industrial solid waste for carbon dioxide capture and utilization (CCU) is considered to be a feasible and promising technology. From the perspective of circular economy, steel-making slag as carbon dioxide storage material has great economic and environmental value. This paper summarized the main carbonation pathways and carbon capture mechanisms of industrial solid wastes. The carbonation processes of the most representative solid waste of steel-making slags were compared, the effects of different carbonation pathways on the carbonation capacity of steel-making slags were evaluated, and the characteristics of carbonation products obtained from different carbonation pathways were also compared. In addition, the industrial application status of carbon dioxide carbonation technology of steel-making slags was analyzed, and the main challenges it faces were summarized and prospected. We hope that this review can attract extensive attention of scholars and promote the further development of carbon dioxide storage technology by mineralization of steel-making slag.
Nb-based alloys are regarded as a vital high temperature structural material. Unfortunately, the low oxidation resistance of the alloys limits their application under aerobic conditions at high ...temperature. Surface coating technology is considered to be an ideal method to solve this problem. This paper reviewed recent progress on silicide coatings on Nb and Nb-based alloy, and focused on different types of modification techniques. The microstructure, phase composition and oxidation properties of various silicified coatings are analyzed. The effects of modified elements and second phase on the oxidation mechanism of silicide coatings are also summarized. Finally, the existing problems and future development direction of various silicide coatings are pointed out.
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A coal-based direct reduction process was used to recover the ferronickel from low-grade nickel laterite ore. The effects of basicity on the compressive strength, metallization rate, microstructure, ...and reduction characteristics of carbon-bearing nickel laterite ore pellets were investigated. The results show that the metallization rate of iron and the compressive strength of metallized pellets follow a parabolic function with increasing basicity. The optimal reduction temperature of the rotary kiln should be controlled at 1150 °C to 1250 °C with pellet basicity of 0.56 to prevent the ring-forming phenomenon. Under optimum process conditions, the metallized pellets mainly consist of ferronickel (Fe,Ni), forsterite ferroan (Mg1.38Fe0.61Ca0.01SiO4), and pigeonite ((Ca0.06Mg0.68Fe0.26)SiO3). The particle size of ferronickel can reach to 30 μm with a high nickel‑chromium concentrations. The compressive strength of metallized pellets is 5220 to 7223 N·Pellet−1, and the metallization rates of iron and nickel are 95.28% to 98.45%, 94.75 to 96.33%, respectively.
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•Producing a high value-added Fe-Ni-Cr alloy is a new idea for the utilization of low-grade nickel laterite ore.•The high basicity is negative to reduction of iron, but can promote the reduction of nickel.•The reduction temperature and pellet basicity are the main factors contributing to the Ni and Cr contents in ferronickel.•The coal-based direct reduction process is a feasible method to obtain the ferronickel from low-grade nickel laterite ore.
Nb-Si based alloys are considered as a potential candidates to substitute for Ni-based super alloys. However, its poor mechanical properties and high temperature oxidation resistance greatly limit ...its development and application. Alloying can effectively improve the mechanical properties and oxidation resistance of Nb-Si based alloy. In this work, the effects of Al, Cr, B elements addition on the mechanical properties and oxidation resistance of niobium-silicon ternary alloys are summarized. The microstructure, oxidation behavior and mechanical properties of various alloys were analyzed and compared. Moreover, the fracture and oxidation failure mechanism of the alloys are also summarized. Finally, the development trend of ternary Nb-Si based oxidation-resistant alloys in the future has been prospected.
In the robot contact operation, the robot relies on the multi-dimensional force/torque sensor installed at the end to sense the external contact force. When the effective load and speed of the robot ...are large, the gravity/inertial force generated by it will have a non-negligible impact on the output of the force sensor, which will seriously affect the accuracy and effect of the force control. The existing identification algorithm time is often longer, which also affects the efficiency of force control operations. In this paper, a self-developed multi-dimensional force sensor with integrated gravity/inertial force sensing function is used to directly measure the resultant force. Further, a method for the rapid identification of payload based on excitation trajectory is proposed. Firstly, both a gravity compensation algorithm and an inertial force compensation algorithm are introduced. Secondly, the optimal spatial recognition pose based on the excitation trajectory was designed, and the excitation trajectory of each joint is represented by a finite Fourier series. The least square method is used to calculate the identification parameters of the load, the gravity, and inertial force. Finally, the experiment was verified on the robot. The experimental results show that the algorithm can quickly identify the payload, and it is faster and more accurate than other algorithms.
Erosion of the refractory materials in blast furnaces (BFs) greatly limits their campaign life, which seriously reduces the economic benefits of iron and steel plants and endangers workers. ...Therefore, it is important to detect and monitor the erosion process of refractory materials in the BF hearth. In this review, the mechanisms of physical damage, chemical corrosion, and mechanical erosion of BF hearths during BF operation are analyzed and summarized. In addition, the effects of hearth structure, refractory type, and protective layer on hearth erosion behavior and hearth life are analyzed and discussed. Some longevity technologies of BF hearths are analyzed and compared, such as reasonable hearth structure design, refractory selection, and technologies to form protective layers. Finally, some suggestions and prospects for the future development of long campaign life BF hearths are discussed.
The burn through of blast furnace (BF) hearths occurs for complex reasons, including corrosion of the refractory materials, high smelting strength, excessive content of harmful impurities, and defective design of the BF structure. Various technologies aimed at improving the longevity of BFs is emphasized, including reasonable hearth structure design, refractory material selection, salamander depth, and the formation of protective skull layers.
Chromium-containing refractories have excellent high-temperature corrosion resistance. In this work, Cr2O3 reinforced Al2O3–SiO2 composite refractories were prepared by reaction sintering process. ...The microstructure, phase composition, mechanical properties and strengthening mechanism of the Cr2O3 reinforced Al2O3–SiO2 composite refractories were investigated. The results show that when the Cr2O3 content is 10–20 wt%, the composites are mainly composed of Cr-mullite (Al3.94Cr0.50Si1.56O10.44), (Al, Cr)2O3, and a small amount of SiO2 phase. When the Cr2O3 content exceeds 20%, the composite refractories mainly consist of (Al, Cr)2O3 and SiO2 phases. The appropriate amount of Cr2O3 can effectively enhance the mechanical properties and compactness of the Cr2O3 reinforced Al2O3–SiO2 composites. This is mainly due to the formation of Cr doped mullite and SiO2 phases, which reduces the sintering temperature of mullite ceramics and improves its density and mechanical properties. The highest hardness (27.03 GPa), flexural strength (213.21 MPa) and compressive strength (528 MPa) values are observed at a Cr2O3 content of 20 wt%. However, excessive addition of Cr2O3 will deteriorate the mechanical properties of the composites. The formation of a large amount of (Al, Cr)2O3 solid solution phase will increase the porosity of the composites, and reduce the compactness and sintering properties of the composites.
Al2O3–Cr2O3 refractories have excellent slag corrosion resistance and can adapt to the oxidation/reduction atmosphere in the smelting reduction ironmaking furnace. Improving the corrosion resistance ...of chrome corundum refractories is of great significance for extending the life length of industrial kilns and decreasing carbon emissions. In this work, the influences of ZrO2 content on the phase evolution, microstructure, physicochemical properties, mechanical properties and slag corrosion resistance of the ZrO2 reinforced Al2O3–Cr2O3 composite refractories were investigated. The results show that the ZrO2 reinforced Al2O3–Cr2O3 composites are primarily composed of (Al, Cr)2O3 solid solution and m-ZrO2. The compressive strength, flexural strength and hardness of the composite refractories can be improved by adding 2.5 wt% ZrO2. However, adding more ZrO2 will reduce its mechanical properties. This is due to ZrO2 excessive content will augement the porosity of the composite refractories, and the phase transformation of ZrO2 will also lead to the formation of microcracks during the cooling process. It is worth noting that higher ZrO2 content improves the thermal shock resistance of the composites, which is primarily put down to the microcrack toughening mechanism of ZrO2. The corrosion tests show that the thicknesses of the corrosion and infiltration layers of composite refractories are significantly decreased accompanied by ZrO2 content increase. This is because the formation of high melting point CaZr4O9 reduces the CaO content and slag alkalinity, and inhibits the dissolution of Al2O3 into the slag to a certain extent. Therefore, the slag corrosion/penetration resistance of the of the composites are obviously improved with the increase of ZrO2 addition.
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Hyper-redundant manipulators with multiple degrees of freedom have special application prospects in narrow spaces, such as detection in small spaces in aerospace, rescue on-site disaster relief, etc. ...In order to solve the problems of complex obstacle avoidance planning and inverse solution selection of a hyper-redundant robot in a narrow space, a cubic B-spline curve based on collision-free trajectory using environmental edge information is planned. Firstly, a hyper-redundant robot composed of four pairs of double UCR (Universal-Cylindrical-Revolute) parallel mechanisms (2R1T, 2 Rotational DOFs and 1 Translation DOF) in series to realize flexible obstacle avoidance motion in narrow space is designed. The trajectory point envelope of a single UCR and the workspace of a single pair of UCR in Cartesian space based on the motion constraint boundaries of each joint are obtained. Then, the constraint control points according to the edge information of the obstacle are obtained, and the obstacle avoidance trajectory in the constrained space is planned by combining the A* algorithm and cubic B-spline algorithm. Finally, a variety of test scenarios are built to verify the obstacle avoidance planning algorithm. The results show that the proposed algorithm reduces the computational complexity of the obstacle avoidance process and enables the robot to complete flexible obstacle avoidance movement in the complex narrow space.
TiO2 is a sintering additive that can significantly improve the sintering and mechanical properties of Cr2O3–Al2O3 refractory materials with high Cr2O3 contents. In this study, TiO2-reinforced ...Cr2O3–Al2O3 composite refractories were prepared using a reaction-sintering process. The microstructure, phase composition, mechanical properties, and strengthening mechanism of the TiO2-reinforced Cr2O3–Al2O3 composite refractories were investigated. The results indicated that the Al2O3–Cr2O3–TiO2 composite refractory with a TiO2 content of 3.0–4.5 wt% had good compactness (porosity of 5.89%), hardness (17.21 GPa), wear resistance (wear rate of 0.4 mm3/Nm), flexural strength (101.10 MPa), and compressive strength (420.90 MPa). This is mainly because when the added amount of TiO2 was <3.0 wt%, TiO2 was solidly soluble in the matrix, forming a Ti3+-doped (Cr, Al)2O3 solid solution, inhibiting abnormal grain growth, rapidly increasing the sintering shrinkage of the sample, rapidly increasing the bulk density, rapidly decreasing the apparent porosity, and improving the sintering and mechanical properties of the composite resistant material. When the TiO2 addition exceeded 4.5 wt%, a large amount of (Cr, Al)2TiO5 phase was distributed between the grain boundaries of the solid solution, and its bulk density started to decrease. The sintering shrinkage and apparent porosity did not change significantly, and the bonding between the solid solution was not improved. Thus, the sintering and mechanical properties of the composite resistant material deteriorated. Taking into account the slag resistance and mechanical properties of the material, Al2O3–Cr2O3–TiO2 with a TiO2 content of 3.0–4.5 wt% can meet the service requirements for mechanical properties of the lining of smelting reduction ironmaking furnaces.
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