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Development and Assessment of Different Hydrometallurgical Processes for Sustainable Recovery of Rare Earths from Spent NdFeB Magnets
No full textThe utilization of NdFeB magnets is extensive in cutting-edge technologies such as hybrid electric vehicles and wind turbines. These magnets possess a substantial REE (Rare Earth Elements) content, approximately 30%, which significantly surpasses the concentration found in natural REE ores. Due to their pronounced economic significance and the associated supply risks stemming from limited primary resources, REEs are classified as critical metals. With the NdFeB permanent magnet sector experiencing an annual growth rate of 20%, the recycling of end-of-life magnets emerges as a highly effective strategy for mitigating challenges related to the supply of essential raw materials. In the current investigation, three distinct processes have been developed to recover REEs from spent wind turbine magnets. These processes encompass (1) oxidation roasting-acid leaching, (2) chlorination roasting-water leaching, and (3) electrochemical dissolution. Optimization of process parameters has been meticulously undertaken for each of these methods to achieve the production of high-purity rare earth oxide (>99%). Furthermore, a comparative evaluation has been conducted, taking into account energy efficiency and environmental sustainability, to determine the most viable approach for the sustainable recovery of REEs from spent NdFeB magnets
Low-Energy Processing of a Local Boltwoodite Ore as Intermediate in Nuclear Fuel Cell
No full textThe industrial demand for pure uranium and uranium compounds is tremendously increasing due to its wide array of utilities most especially in nuclear industries. Consequently, the treatment of a local boltwoodite ore containing albite (Na2.00Al2.00Si6.00O16.00: 96-900-1634), boltwoodite (Na2.00K2.77U3.00Si6.00O9.00H4.00: 96-900-7219), thorite (Th4.00Si4.00O16.00: 96-9007625), and quartz (Si6.00O6.00: 96-900-5019) was examined in sulphuric acid media. The experimental parameters such as leachant concentration, reaction temperature, and particle size on uranium ore dissolution were investigated. At optimal leaching conditions (2.5 mol/L H2SO4, 75 degrees C, and 75 mu m), an 89.1% dissolution rate was achieved within 120 min. The estimated activation energy of 20.70 kJ/mol supported the diffusion control reaction mechanism as the rate-determining step. The leach liquor obtained at established conditions was further beneficiated to produce an industrial grade sodium diuranate (Na2U2O7: 00-064-0473, density = 6.51 g/cm(3), melting point = 1654 +/- 2 degrees C) proposed to serve as intermediate raw-material in a nuclear fuel cell
Enhancing Recycling Potential: Exploring Reduction and Metal Separation Behavior of Iron-Rich Slag in Electric Arc Furnace Smelting for a Sustainable Future
No full textThe electric arc furnace steelmaking route is essential for sustainable steelmaking through hydrogen-based direct reduced iron. About 30% of the global steel production currently follows the scrap/direct reduced iron-electric arc furnace (DRI-EAF) route, which is bound to increase given decarburization efforts by the steel industry. We investigated DRI-EAF slag recycling simulated in laboratory EAF smelting tests to lower its environmental impact. Several aspects of process development were explored, such as process conditions, specific energy consumption, and the settling behavior of iron particles. Significant reductions occur in the first 15 min, ranging from 73.4% to 83.34%. About 97% iron was recovered under optimum conditions: basicity-1.2, carbon/oxygen ratio-1, and time-40 min. The settling velocities of iron particles decreased with increasing slag basicity, reaching values of 3.13 x 10-5 m/s, 1.95 x 10-5 m/s, and 0.89 x 10-5 m/s for basicities 0.9, 1.2, and 1.5, respectively. The effects of basicity on slag viscosity, phase formation, and energy consumption are critically discussed. Compared to 0.9, basicities of 1.2 and 1.5 increase power consumption by 17.6% and 23.5%, respectively. The findings potentially contribute to managing DRI-EAF-based slag, repositioning it as a potential resource, and reducing associated pollution
Metallurgical Failure Analysis of Economizer Tube of Thermal Power Plant
No full textIn present investigation, failure investigation of
failed economizer tube of boiler of the thermal power plant
was analyzed through visual inspection, dimensional
measurement, bulk chemical analysis, mechanical properties evolution and metallurgical analysis. Failure of the
economizer tube was occurred in the form of cavity having
one longitudinal hairline crack passing through the cavity
on the external surface of economizer tube. Metallurgical
failure analysis of an economizer tube was carried out by
visual observation, chemical analysis, optical microscopy
(OM), scanning electron microscopy, SEM-EDS analysis,
x-ray diffraction (XRD) and mechanical properties evaluation. Ash deposit and surface corrosion were on outer
surface were observed. Severe corrosion and thinning were
observed on the external surface of economizer tube. SEMEDS analysis on the fractographic samples near failure
zone showed good amount of Cu deposition on the inner
surface of the tube and ash-related corrosion products on
the outer surface of the tube. Localized reduction/thinning
of wall thickness of the economizer tube happened due to
combined effect of ash corrosion-erosion from outside and
pitting/galvanic corrosion from inner surface due to Cu
deposition and finally resulted in failure of the tube.
However, outer corrosion on the tube is significantly
dominant due to ash corrosion. Therefore, ash corrosion is
major cause of failure of economizer tube. Ash corrosion
was due to use of poor-quality coal. To mitigate the
problem, removal of ash deposition on outer surface and
Cu deposition on inner surface of tube should be carried
out by periodically by proper cleaning and use of good
quality coal is suggested
An investigation into the effect of various parameters on oilagglomeration process of coal fines
No full textIn the present study, the authors have performed oil agglomeration of coal fines using castor oil and combination of castor oil and turpentine oil in various proportions. The coal samples were collected from three different mines of Mahanadi Coalfields Limited having high ash content(27–39%). From the post proximate analysis it was revealed that in caseof Mine 1 coal, the moisture content reduced by 83%, for Mine 2 it was94% and for Mine 3 the moisture reduced by 90% from the initial values. Grade achieved after oil agglomeration process was G5 grade for Mine 2coal and G3 grade for Mine 1 & 2 coal. The effect of various parameters such as oil dosage, pulp density, pH, on yield, ash rejection and organic matter recovery were studied. The parameter with the highest relative importance was found to be oil dosage (normalized importance of100%) whereas agitation time and pulp density were found to have normalized relative importance of 74% and 70%, respectively. A non-linear regression model in the form of quadratic equation has also been proposed for ash rejection (%) based on the independent variables such as pulp density, oil dosage and agitation time
Structural phase transformation in single-crystal Fe–Cr–Ni alloy during creep deformation using molecular dynamics simulation and regression-based machine learning methodology
No full textManipulation of creep properties and microstructural transformations at different temperatures and applied stresses depicts huge importance for the design and development of various grades of metals and alloys. Therefore, we have considered nano-size face-centered cubic (FCC) single crystal of Fe–Cr–Ni alloy to investigate creep response under a wide range of temperatures and pressure through molecular dynamics (MD) simulation and regression-based machine learning methodologies. From MD simulation, we have found the evolution of multiple rectangular blocks of body-centered cubic (BCC) crystal and layered FCC and HCP crystal during creep deformation under externally applied tensile load. Rectangular blocks and layered crystal structures corroborated with the secondary and tertiary stages of creep curves of Fe–Cr–Ni alloy, respectively. Machine learning methodology provides information to predict the creep properties and correlates data obtained from MD simulations. The results of this investigation will provide an understanding of the creep properties during thermal and mechanical processing, which will help to improve the performance of various grades of steel and other alloy
Determinant analysis of oil agglomeration of coal fines using multiple regression and neural network models
No full textOil agglomeration has gained importance owing to its simplicity and efficiency in beneficiating coal fines. In this study, high ash coal samples taken from six mines in India were put through an oil agglomeration process to investigate the usage of castor oil or blend of castor and turpentine for recovery of coal fines from coal-water slurry. The performance of the process has been evaluated based on ash rejection [AR (%)] and yield (%). Various Statistical analyses were carried out to investigate the role of various process parameters, such as PD, OD, AT, and oil-type on AR (%) and yield (%). Step-wise regression was performed for development of prediction model for AR (%) and yield (%). Determinant analysis was performed using general linear model (GLM). Our findings indicate that pulp density was the strongest determinant for AR (%), followed by oil dosage and agitation time. Similarly, oil dosage was the primary determinant for yield (%), followed by pulp density and agitation time. Sensitivity analysis was also carried out using artificial neural network (ANN) and the results in respect AR (%) revealed that agitation time was the most important predictor followed by pulp density and oil dosage
Measurement of Mid Spatial Frequencies of Diamond Turned Optics by using Dual-mode Snapshot Interferometry
No full textThe measurement of mid-spatial frequency (MSF) in ultra-precision machining is crucial for assessing the quality and performance of machined surfaces. MSF refers to the frequency range of surface irregularities between low-frequency form errors and high-frequency roughness. The sources that contribute to MSF errors during diamond turning are vibrations and dynamic instabilities, tool wear and deflection during cutting, inconsistent feed rates, variation in material properties, incorrect machine settings/process parameters, material removal mechanism employed (e.g., ductile or brittle removal). Controlling & measuring mid-spatial frequencies in the diamond-turning process is essential for meeting stringent optical specifications in various applications, such as lens manufacturing for imaging systems, telescopes, laser systems, etc. Inspecting MSF errors offline or after the manufacturing process is a common practice in the quality control of optical surfaces. However, there is a growing interest in incorporating on-machine metrology to detect and address MSF errors. One of the latest developments is a dual-mode on-machine metrology (OMM) system that simultaneously measures surface form and roughness without requiring the optical path's reconfiguration to switch between laser interferometer mode and LED interference microscopy mode. This study uses OMM to study the influence of process parameters and their impact on the mid-spatial frequencies during diamond turning. OMM provides real-time feedback, which helps in adjusting machining parameters to correct deviations and maintain the desired mid-spatial frequencies
Production and recycling of blast furnace slag: A life cycle assessment approach in India
No full textThis article investigated the cradle-to-gate environmental impact of granulated blast furnace slag (GBFS) produced in the steel industry and replacement of blast furnace (BF) slag (50%) in place of clinker in Portland slag cement using GaBi software (Indian extension database). In case of GBFS production, maximum burden on the environment is due to BF slag production and the amount of electricity consumed (161 MJ/ton) during the granulation process. The influence of electricity sources on GBFS production was studied via scenario analysis. For investigation, solar and thermal electricity mixes were considered in 50:50 and 75:25 ratios. For the 75:25 ratios, the abiotic depletion potential (fossil), acidification, eutrophication, global warming, and human toxicity potential show a decreasing trend of approximately 45%, 49%, 48%, 46%, and 41%, respectively. The scenario analysis of BF slag transportation (from 100 to 750 km) demonstrates a negative impact due to fuel. The results quantitatively confirm that the addition of GBFS can lower the overall impact for construction and steel industries
Effect of hold-type on cyclic life and microstructural evolution of an austenitic stainless steel
No full textThe present work investigates the effect of different type of hold on the change in microstructure and cyclic life. i.
e., number of cycles to failure of the 304LN grade austenitic stainless steel at an elevated temperature. The straincontrolled low cycle fatigue and creep-fatigue interaction tests were carried out in air at 540 ◦C for constant total
strain amplitude levels of ± 0.5 % and ± 0.7 %. The duration of hold-time was maintained at a constant level of
600 s at peak tensile, compressive and both peak tensile-compressive strain during different creep-fatigue
interaction tests. Due to incorporation of creep damage, the cyclic life of the creep-fatigue interaction-tested
samples has been found to be lower than that of the low cycle fatigue-tested samples. The tensile-hold appears to
have maximum impact on reduction in cyclic life during creep-fatigue interaction tests followed by tension compression hold and compressive hold. The scanning electron microscopy and electron back scattered
diffraction analyses of creep-fatigue interaction-tested samples have revealed that the grain size coarsening,
reduction in twin boundary fraction and increase in average Kernel Average Mis orientation are the key factors in
reduction of cyclic lif