CO–H₂ Gas-Based Reduction Behavior of Cr-Rich Electroplating Sludge Mixed with Iron Ore Powder

Cr-rich electroplating sludge (CRES) is a complicated solid waste with high contents of chromium and iron. It can be used as a main feed of the FINEX ironmaking process, which requires gas-based reduction before smelting reduction to produce molten iron with the proper addition of iron ore powder. In this study, the CO–H2 gas-based reduction behavior of CRES mixed with iron ore powder was evaluated between 700 °C and 850 °C, with a focus on the variations of key components containing Fe, Cr, and S with reduction temperature and time. It was found that the iron oxides in CRES had stepwise conversions to metallic iron as the reduction reaction proceeded. The iron metallization degree of the mixture of CRES and iron ore powder increased obviously below 750 °C and then grew minorly with the further increase of temperature. Moreover, this index varied similarly with an extension of reduction time up to 80 min. After reduction at 750 °C for 60 min with the volume concentration of H2 of 30% and flow rate of 160 mL/min, the iron metallization degree reached 79.08%. The rate in the process was limited by a chemical reaction with an activation energy of 41.32 kJ/mol. Along with the stepwise reduction of iron oxides to metallic iron, the chromium hydroxide and sulfates in CRES were reduced to Cr2O3 and sulfites and sulfides, respectively

Conference Proceedings of the 10th International Symposium on Project Management, China

The aim of the current study was to explore the effect of risk attitude on commercial insurance consumption decisions, using data from the China Household Financial Survey (2017). Logistic regression analysis was used to test the relationship above-mentioned, while variables such as gender, age, education level, and total household income were controlled. Results suggest that risk choice can positively predict commercial insurance purchasing behavior, and individuals with risk preferences are more likely to purchase commercial insurance. The finding provides behavioral scientific support for improving residents&#39; purchasing of commercial insurance.</p

Microwave Drying Kinetics of Chromium-Rich Electroplating Sludge

Chromium-rich electroplating sludge (CRES) is a hazardous solid waste with a high content of moisture requiring efficient drying before subsequent treatment. In this study, the microwave drying kinetics of CRES were examined. The results showed that CRES had good microwave absorptivity, contributing to a much shorter drying time and better drying performance compared with conventional drying. In comparison with conventional drying at 105 °C, the time of microwave drying at 600 W for total moisture removal was reduced by 98.5%. Compared to load mass and particle size, microwave power played a more important role in microwave drying. Based on the kinetics analysis, the microwave drying process of CRES could be divided into three successive stages, in which the drying rates were limited by external diffusion (before 110 s), both external diffusion and chemical reaction (between 110 s and 160 s), and chemical reaction (after 160 s), respectively. The Danish model was found to have the best fit with the microwave drying process of CRES

Porous Materials from Thermally Activated Kaolinite: Preparation, Characterization and Application

In the present study, porous alumina/silica materials were prepared by selective leaching of silicon/aluminum constituents from thermal-activated kaolinite in inorganic acid or alkali liquor. The correlations between the characteristics of the prepared porous materials and the dissolution properties of activated kaolinite were also investigated. The results show that the specific surface area (SSA) of porous alumina/silica increases with silica/alumina dissolution, but without marked change of the BJH pore size. Furthermore, change in pore volume is more dependent on activation temperature. The porous alumina and silica obtained from alkali leaching of kaolinite activated at 1150 °C for 15 min and acid leaching of kaolinite activated at 850 °C for 15 min are mesoporous, with SSAs, BJH pore sizes and pore volumes of 55.8 m2/g and 280.3 m2/g, 6.06 nm and 3.06 nm, 0.1455 mL/g and 0.1945 mL/g, respectively. According to the adsorption tests, porous alumina has superior adsorption capacities for Cu2+, Pb2+ and Cd2+ compared with porous silica and activated carbon. The maximum capacities of porous alumina for Cu2+, Pb2+ and Cd2+ are 134 mg/g, 183 mg/g and 195 mg/g, respectively, at 30 °C

Alumina-enhanced valorization of ferronickel slag into refractory materials under microwave irradiation

This study presents a new approach to enhance preparation of superior-quality refractory materials by microwave sintering of the mixture of ferronickel slag and sintered magnesia with addition of alumina up to 10 wt %. It was shown that in the process of microwave sintering, the proper addition of alumina could contribute to formation of forsterite with fine and relatively uniform particle size. It also promoted the generations of high melting point magnesium aluminate spinel (MgAl2O4), magnesium iron aluminate spinel (MgFe0.6Al1.4O4), and magnesium aluminum chromate spinel (MgAl0.5Cr1.5O4) which replaced magnesium chromate spinel (MgCr2O4) formed during sintering without addition of alumina, eventually improving refractoriness and other properties of the resulting refractory material. By adding 4 wt % alumina to the mixture of slag and 25 wt % sintered magnesia for sintering at 1250 °C in only 20 min, the resulting refractory material obtained refractoriness of 1790 °C. Compared with that prepared in the absence of alumina, the refractoriness was increased by 156 °C. The method proposed in this study has good potential in improving valorization of ferronickel slag into value-added materials, exhibiting both apparent economic and environmental benefits

Energy Saving of Composite Agglomeration Process (CAP) by Optimized Distribution of Pelletized Feed

The composite agglomeration process (CAP) aims at sintering a pelletized feed and a matrix feed together to produce a high-quality burden for a blast furnace. The pelletized feed is balled from fine iron concentrate or refractory iron-bearing resources, while the matrix feed is granulated from iron ore fines, fuels, fluxes and so on. Through mathematical calculation, heat accumulation regularity and heat-homogenizing of the sinter bed are acquired in CAP when pelletized feed is uniformly distributed. Then they are studied in the composite agglomeration process with optimized pelletized feed distribution, which is a novel and perfect sinter bed structure. Results show that large heat input gaps exist in the sinter bed under condition of even sinter mixture distribution, and it is very difficult to realize bed heat-homogenization by directly varying the solid fuel dosage among each layer. An optimized pelletized feed distribution realizes more heat in the upper layer together with heat-homogenization of the middle-lower layer when the proportions of pellets increase first in the middle-upper layer and then decrease in the middle-lower layer of the sinter bed. Under these circumstances, the sinter bed has much better available accumulation ratios with a maximum value of 78.29%, and possesses a greater total heat input of 6754.27 MJ when the coke breeze remains at the original dosage. To make full use of the available heat accumulation and adjust the pellet distribution, a good energy saving effect is obtained because the coke breeze mass declines by 13.91 kg/t-sinter. The current gross heat inputs of each unit are reduced remarkably, leading to a total heat input decrease of 25.95%. In pot tests of CAP, the differences of thermal parameters in whole bed are obviously reduced with the optimized pelletized feed distribution, which contributes to sinter homogeneity and energy savings

Utilization of the MgO-Rich Residue Originated from Ludwigite Ore: Hydrothermal Synthesis of MHSH Whiskers

In this work, from the MgO-enriched residue originated from ludwigite ore, value-added magnesium hydroxide sulfate hydrate (MHSH) whiskers were prepared via sulfuric acid leaching and leachate purification, followed by hydrothermal synthesis. During sulfuric acid leaching, 98.2% magnesium and 99.6% silica were removed under the optimal leaching conditions: sulfuric acid concentration of 40%, leaching temperature of 80 °C, leaching time of 90 min, and liquid to solid ratio of 4 mL/g. After purification of the acidic leachate via oxidation and precipitation to remove impurities including iron and aluminum, the Mg2+-rich solution was used to prepare magnesium hydroxide sulfate hydrate whiskers (5Mg(OH)2·MgSO4·2H2O, abbreviated as 512MHSH) via hydrothermal synthesis. Finally, 512MHSH whiskers were obtained with 30–100 μm in length, 0.5–1.0 μm in diameter and aspect ratio of approximately 100. The physicochemical characteristics of whiskers were further characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), Fourier Transform Infrared Spectroscopy (FT-IR) and Thermogravimetry-Differential Scanning Calorimetry (TG-DSC)