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1.
Japan started the national project “COURSE 50” for CO2 reduction in the 2000s. This project aimed to establish novel technologies to reduce CO2 emissions with partially utilization of hydrogen in blast furnace-based ironmaking by 30% by around 2030 and use it for practical applications by 2050. The idea is that instead of coke, hydrogen is used as the reducing agent, leading to lower fossil fuel consumption in the process. It has been reported that the reduction behavior of hematite, magnetite, calcium ferrite, and slag in the sinter is different, and it is also considerably influenced by the sinter morphology. This study aimed to investigate the reduction behavior of sinters in hydrogen enriched blast furnace with different mineral morphologies in CO–CO2–H2 mixed gas. As an experimental sample, two sinter samples with significantly different hematite and magnetite ratios were prepared to compare their reduction behaviors. The reduction of wustite to iron was carried out at 1000, 900, and 800°C in a CO–CO2–H2 atmosphere for the mineral morphology-controlled sinter, and the following findings were obtained. The reduction rate of smaller amount of FeO led to faster increase of the reduction rate curve at the initial stage of reduction. Macro-observations of reduced samples showed that the reaction proceeded from the outer periphery of the sample toward the inside, and a reaction interface was observed where reduced iron and wustite coexisted. Micro-observations revealed three layers, namely, wustite single phase in the center zone of the sample, iron single phase in the outer periphery zone of the sample, and iron oxide-derived wustite FeO and iron, or calcium ferrite-derived wustite 'FeO' and iron in the reaction interface zone. A two-interface unreacted core model was successfully applied for the kinetic analysis of the reduction reaction, and obtained temperature dependent expressions of the chemical reaction coefficients from each mineral phases.  相似文献   

2.
NH4HCO3 conversion followed by HCl leaching was performed and proven to be effective in extracting Pb and Sr from zinc extracted residual. The mechanism and operating conditions of NH4HCO3 conversion, including molar ratio of NH4HCO3 to zinc extracted residual, NH4HCO3 concentration, conversion temperature, conversion time, and stirring velocity, were discussed, and operating conditions were optimized by the orthogonal test. Experimental results indicate that NH4HCO3 conversion at temperatures ranging from 25 to 85°C follows the shrinking unreacted core model and is controlled by inner diffusion through the product layer. The extraction ratios of Pb and Sr under optimized conditions reached 85.15% and 87.08%, respectively. Moreover, the apparent activation energies of Pb and Sr were 13.85 and 13.67 kJ·mol?1, respectively.  相似文献   

3.
《矿物冶金与材料学报》2021,28(12):2001-2007
Graphene oxide (GO) wrapped Fe3O4 nanoparticles (NPs) were prepared by coating the Fe3O4 NPs with a SiO2 layer, and then modifying by amino groups, which interact with the GO nanosheets to form covalent bonding. The SiO2 coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets. The effect of the amount of SiO2 on the morphology, structure, adsorption, and regenerability of the composites was studied in detail. An appropriate SiO2 layer can effectively induce the GO nanosheets to completely wrap the Fe3O4 NPs, forming a core-shell Fe3O4@SiO2@GO composite where Fe3O4@SiO2 NPs are firmly encapsulated by GO nanosheets. The optimized Fe3O4@SiO2@GO sample exhibits a high saturated adsorption capacity of 253 mg·g?1 Pb(II) cations from wastewater, and the adsorption process is well fitted by Langmuir adsorption model. Notably, the composite displays excellent regeneration, maintaining a ~90% adsorption capacity for five cycles, while other samples decrease their adsorption capacity rapidly. This work provides a theoretical guidance to improve the regeneration of the GO-based adsorbents.  相似文献   

4.
In this work, different magnesium silicate mineral samples based on antigorite, lizardite, chrysotile (which have the same general formula Mg3Si2O5(OH)4), and talc (Mg3Si4O10(OH)2) were reacted with KOH to prepare catalysts for biodiesel production. Simple impregnation with 20wt% K and treatment at 700–900°C led to a solid-state reaction to mainly form the K2MgSiO4 phase in all samples. These results indicate that the K ion can diffuse into the different Mg silicate structures and textures, likely through intercalation in the interlayer space of the different mineral samples followed by dehydroxylation and K2MgSiO4 formation. All the materials showed catalytic activity for the transesterification of soybean oil (1:6 of oil : methanol molar ratio, 5wt% of catalyst, 60°C). However, the best results were obtained for the antigorite and chrysotile precursors, which are discussed in terms of mineral structure and the more efficient formation of the active phase K2MgSiO4.  相似文献   

5.
《矿物冶金与材料学报》2021,28(9):1397-1412
As the world’s second largest economy experiencing rapid economic growth, China has a huge demand for metals and energy. In recent years, China ranks first, among all the countries in the world, in the production and consumption of several metals such as copper, gold, and rare earth elements. Bioleaching, which is an approach for mining low grade and refractory ores, has been applied in industrial production, and bioleaching has made great contributions to the development of the Chinese mining industry. The exploration and application of bioleaching in China are reviewed in this study. Production and consumption trends of several metals in China over the past decade are reviewed. Technological processes at key bioleaching operations in China, such as at the Zijinshan Copper Mine and Mianhuakeng Uranium Mine, are presented. Also, the current challenges faced by bioleaching operations in China are introduced. Moreover, prospects such as efficiency improvement and environmental protection are proposed based on the current situation in the Chinese bioleaching industry.  相似文献   

6.
《矿物冶金与材料学报》2021,28(12):1940-1948
The evolution of inclusions and the formation of acicular ferrite (AF) in Ca–Ti treated steel was systematically investigated after Mg and La addition. The inclusions in the molten steel were Ca–Al–O, Ca–Al–Mg–O, and La–Mg–Ca–Al–O after Ca, Mg, and La addition, respectively. The type of oxide inclusion in the final quenched samples was the same as that in the molten steel. However, unlike those in molten steel, the inclusions were Ca–Al–Ti–O + MnS, Ca–Mg–Al–Ti–O + MnS, and La–Ca–Mg–Al–Ti–O + MnS in Mg-free, Mg-containing, and La-containing samples, respectively. The inclusions distributed dispersedly in the La-containing sample. In addition, the average size of the inclusions in the La-containing sample was the smallest, while the number density of inclusions was the highest. The size of effective inclusions (nucleus of AF formation) was mainly in the range of 1–3 μm. In addition, the content of ferrite side plates (FSP) decreased, while the percentage of AF increased by 16.2% due to the increase in the number of effective inclusions in the La-containing sample in this study.  相似文献   

7.
The butt welds of 4-mm thick 5A06 aluminum alloy plates were produced by adjustable-gap bobbin-tool friction stir travel with travel speeds of 200, 300, and 400 mm/min in this study. The microstructure was studied using optical microscopy and electron backscatter diffraction (EBSD). Tensile tests and microhardness measurements were performed to identify the effect of the travel speed on the joint mechanical properties. Sound joints were obtained at 200 mm/min while voids were present at different positions of the joints as the travel speed increased. The EBSD results show that the grain size, high angle grain boundaries, and density of geometrically necessary dislocations in different regions of the joint vary depending on the recovery and recrystallization behavior. Specific attention was given to the relationship between the local microstructure and mechanical properties. Microhardness measurements show that the average hardness of the stir zone (SZ) was greater than that of the base material, which was only affected slightly by the travel speed. The tensile strength of the joint decreased with increasing travel speed and the maximal strength efficiency reached 99%.  相似文献   

8.
Coalfield fires are considered a global crisis that contributes significantly to environmental destruction and loss of coal resources and poses a serious threat to human safety and health. In this paper, research related to the initiation, development, and evolution of coalfield fires is reviewed. The existing detection and control techniques of coalfield fires are also reviewed. Traditional firefighting is associated with waste of resources, potential risks of recrudescence, potential safety hazards, extensive and expensive engineering works, and power shortages. Recently, coalfield fires have been recognized as having significant potential for energy conservation and heat energy recovery. Thermoelectric power generation is regarded as a suitable technology for the utilization of heat from coalfield fires. The extraction of heat from coalfield fires can also control coalfield fires and prevent reignition leading to combustion. Technologies for absorbing heat from burning coal and overlying rocks are also analyzed. In addition, the control mode of “three-region linkage” is proposed to improve firefighting efficiency. Integrating heat energy recovery with firefighting is an innovative method to control coalfield fires.  相似文献   

9.
A high-building multi-directional pipe joint (HBMDPJ) was fabricated by wire and arc additive manufacturing using high-strength low-alloy (HSLA) steel. The microstructure characteristics and transformation were observed and analyzed. The results show that the forming part includes four regions. The solidification zone solidifies as typical columnar crystals from a molten pool. The complete austenitizing zone forms from the solidification zone heated to a temperature greater than 1100°C, and the typical columnar crystals in this zone are difficult to observe. The partial austenitizing zone forms from the completely austenite zone heated between Ac1 (austenite transition temperature) and 1100°C, which is mainly equiaxed grains. After several thermal cycles, the partial austenitizing zone transforms to the tempering zone, which consistes of fully equiaxed grains. From the solidification zone to the tempering zone, the average grain size decreases from 75 to 20 μm. The mechanical properties of HBMDPJ satisfies the requirement for the intended application.  相似文献   

10.
Nano graphene platelet (Gr) reinforced nano composites with a zinc–aluminum alloy (ZA27) matrix were produced by powder metallurgy at four different mass ratios (0.5wt%, 1.0wt%, 2.0wt% and 4.0wt%) and three different sintering temperatures (425, 450, and 475°C). In order to investigate the effect of sintering temperatures and nano graphene reinforcement materials on the composite structure, the microstructures of the composite samples were investigated and their densities were determined with a scanning electron microscope. Hardness, transverse rupture, and abrasion wear tests were performed to determine the mechanical properties. According to the test results, the porosity increased and the mechanical strength of the nano composites decreased as the amount of nano graphene reinforcement in ZA27 increased. However, when the composites produced in different reinforcement ratios were evaluated, the increase in sintering temperature increased the mechanical structure by positively affecting the composite structure.  相似文献   

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