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A comparative study on the characterisation and combustion behaviour of high ash coals from two different geographical origins
No full textThe ultimate use of coal is primarily dependent on the composition, distribution, modes of occurrences of the minerals and their association with the organics. Therefore, an adequate knowledge of the minerals, macerals and their ignition behaviour is inevitable for the subsequent utilisation of coal in various aspects. Here, we present a comparative characterisation and combustion study of two high ash non-coking coals (AH and BL) with ash yield of 42.42 and 45 wt% on dry basis and gross calorific value of 3620 and 3363 kcal/kg respectively. Both coals are rich in vitrinite with moderate liptinite and the volume percentage of inertinite is comparatively lower than the vitrinite. Both coals are rich in alumino-silicate minerals and Fe and Ti oxide are present in moderate concentrations. They have crystalline forms with discrete grain boundaries which make them susceptible for beneficiation. The fractionation characteristics like low slagging and fouling potential, high silica ratio and low base to acid ratio suggest that the two coals are feasible for their successive utilisation in thermal power plants. Concerning the macerals's reactivity; BL coal has a comparatively lower TG peak temperature and burnout temperature than the AH. Also BL sample has relatively more volatile matter. Both coals have high ash fusion temperatures but BL coal ash consists of high proportion of refractory minerals e.g. SiO2, Al2O3 and TiO2. Hence, BL coal has better amenability for easy ignition and its combustion characteristics are expected to be improved than the AH
Asymmetric cyclic loading behavior of micro-alloyed 2.25 Cr–Mo steel at room temperature
No full textRatcheting fatigue tests were carried out on the micro-alloyed 2.25Cr–Mo steel with variable mean stress (σm), stress amplitude (σa) and stress rate () at room temperature. Increase in the σm and σa resulted in higher plastic strain accumulation and caused a reduction in fatigue life; however, rise in the enhanced the fatigue life. Hysteresis loop analysis showed variation in plastic strain range under the different test variables. Transmission electron microscopy (TEM) was carried out to understand the lower plastic strain accumulation resulting from the high . It was observed that at high there was formation of stacking-faults/micro-twins in the M23C6 carbides, due to which there was strain partitioning between the matrix and the carbide particles, consequently, the effective strain in the matrix was reduced. Using mathematical modeling, experimental fatigue life was predicted by the trial and error method. The predicted fatigue life was found within the 1.55X scatter band and there was a reasonable estimation of ratcheting fatigue life
Investigation on Multifunctional Properties of Sputtered Ti-Si-B-C Coating with Varied Thickness over Targeted Surface
No full textA nanocomposite coating of titanium, silicon, boron and carbon (Ti-Si-B-C) with variable width (3 to 25 mu m) has been deposited on stainless steel 304 grade (SS-304) surface using magnetron sputtering. The variation in coating thickness of Ti-Si-B-C onto SS-304 was investigated to systematically explore its structural, mechanical, oxidation properties and electrical resistivity. The study of mechanical properties revealed high hardness and elastic modulus of surfaces for lower thickness Ti-Si-B-C film. Analysis of adhesion behavior of coated surfaces with higher thickness exhibited no spallation at 30 N loads. The isothermal oxidation kinetics studies for higher thickness coatings (>= 15 mu m) using thermogravimetric analysis showed excellent thermal stability at similar to 800 degrees C. Furthermore, electrical property measured by four point probe exhibited low resistivity with increase in thickness at room temperature. Surface properties such as microstructure, phases and elemental analysis of the deposited films were carried out by using field emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX), respectively. All these obtained experimental results showed the attainment of perfect coating width of Ti-Si-B-C which can one step ahead be successfully applied in diverse fields
Role of Cerium on Transformation Kinetics and Mechanical Properties of Low Carbon Steels
No full textThe present study has focused on the detailed dilatometric and electron microscopic analysis of the formation of austenite and its decomposition in two Cerium (Ce) modified steels containing 0.6 and 0.03 wt pct Ce. Despite a long incubation time, the austenite formation is very fast in the high-Ce steel (0.6 wt pct Ce) during heating. Whereas, the low-Ce steel (0.03 wt pct Ce) promotes early nucleation of austenite but shows a significant delay in the completion of the transformation. Similar trend has been observed for the decomposition of austenite during cooling; the low-Ce steel shows early start of transformation with a sluggish kinetics. The role of Ce on the overall transformation kinetics of austenite during the heating-cooling cycle has been investigated and discussed from thermodynamic viewpoint and nucleation probability. Engineering stress-strain curves have shown a better combination of strength and ductility in the low-Ce steel compared to the high-Ce one. Coarse and spherical Ce2O3 particles (average dia. similar to 4 mu m) in grain interior along with the brittle and grain boundary elongated Ce-C/Ce-Fe intermetallic phases (length similar to 8 mu m and width similar to 3 mu m) are responsible for the lower strain hardening as well as an early failure of the high-Ce steel. Finally, the microstructure-tensile property correlation has been established using chemical composition and fractographic analysis. (C) The Minerals, Metals & Materials Society and ASM International 202
Effect of cold deformation extent and ART annealing duration on the microstructure and mechanical properties of a medium manganese steel
No full textThe effect of cold rolling reduction extent and austenite reverted transformation (ART) annealing duration on the microstructure evolution and the ensuing mechanical properties of a medium Mn steel was investigated. Cold rolling reduction was varied from 18.18% to 72.72% followed by ART annealing for different time duration (2-6 h) at a pre-determined temperature of 650 degrees C. The retained austenite fraction was found to increase with cold deformation extent as well as with the ART annealing duration. With increase in the extent of cold reduction the morphology of microstructure gradually shifted from a lamellar structure to globular, owing to recrystallization of the heavily deformed sample. Cold reduction level of similar to 36.36% was found to be the threshold limit for morphology transition from lamellar to globular. A two-fold increase in the dislocation density of the retained austenite phase was observed after 6 h of ART annealing of the 18.18% cold deformed specimen in comparison to the 72.72% cold deformed specimen. The higher dislocation density in the less deformed specimen was associated with the recrystallization and a higher austenite to martensite transformation during the quenching post ART annealing process. A greater yield point elongation in samples deformed to a higher extent was revealed, which was completely absent in samples deformed to a lesser extent. Variation in strength-ductility combination was correlated with the retained austenite content and its stability, both of which varied with cold deformation and the duration of ART annealing
Multi-response and Misplacement Optimization of Upgrading BMQ Ore in Liquid-Solid Fluidized Bed Separator Using Taguchi-based Grey Relational Analysis
No full textLiquid-solid fluidized bed separators (LSFBS) are particles handling equipment where solid particles are caused to exhibit liquid-like behavior. Segregation and separation of suspended particles are achieved by maintaining superficial velocity of upward flowing fluid between settling velocity and terminal velocity of particles. Rapid increase in the consumption rate of metals and ores in the last few decades necessitates effective utilization of marginal, low-grade ores. This work focuses on the ability of LSFBS in upgrading lean-grade banded magnetite quartzite (BMQ) ore. To gain an understanding of segregation, separation, and layer inversion phenomena inside the fluidization column, hydrodynamics characteristics, process efficiency, and misplacement of solid particles have been studied qualitatively and quantitatively. Feed, concentrate, and tailing samples were analyzed using wet chemical method, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. Taguchi-based grey relational analysis (GRA) and one-way ANOVA were employed to statistically analyze the fluidization process and provide ranking of input parameters for individual and multiple responses synchronically. In order to characterize misplacement, fractions of iron-phase minerals and gangue minerals reporting in overflow (tailings) and underflow (concentrate) have been calculated. The best rank indicating multi-response optimization and the highest normalized misplacement index were obtained at superficial velocity: 1.41 cm/s, mean particle size: 125 mu m, overflow tap height: 62 cm, and bed height: 20 cm. The highest values of normalized misplacement index and misplacement index obtained are 28.82975% and - 0.5979, respectively. This suggests that minimum misplacement and maximum process efficiency can be achieved at this optimized set of experimental conditions
Artificial neural network-based sensitivity analysis and experimental investigation of liquid-solid fluidization technique for low-grade coal upgradation
No full textLiquid-solid fluidization technique is being applied where low-grade coal or minerals enrichment is mostly density-based. Static and dynamic behavior of particles in a fluid medium has been extensively investigated over the years because of its dynamic applications across various industries. In this work, bed characterization studies and experiments have been conducted to study coal washing ability of the liquid-solid fluidized bed separator. Results have been recorded in terms of ash rejection%, combustible recovery% and separation efficiency%. Minimum fluidization velocity and pressure drop values have been predicted using existing theoretical correlations and compared with the experimental values. A three-layered (4:5:3) feedforward back-propagation (FFBP) neural network model was developed using Levenberg-Marquardt algorithm, LOGSIG and MSE as training, transfer and performance functions respectively. Garson's algorithm and connection weight approach have been employed for sensitivity analysis to interpret the neural network results physically. Coefficients of correlation, all R (including training, validation & testing datasets) obtained for outputs ash rejection (R = 0.9960), combustible recovery (R = 0.9952) and separation efficiency (R = 0.9944) suggest that predicted values are in agreement with the experimental values and the developed model is a good fit
Corrosion behavior of AlCuFeMn alloy in aqueous sodium chloride solution
Get PDFMedium Entropy Alloy AlCuFeMn possesses high room temperature strength and oxidation endurance. In present
work, the aqueous corrosion resistance of the as-cast as well as low temperature oxidized AlCuFeMn alloy in 3.5
wt% NaCl solution, is explored. Equimolar proportions of high purity copper, manganese, iron, and aluminum
were arc melted and cast in a copper mold. The alloy primarily consists of a face-centered cubic and a bodycentered cubic phase. Potentiodynamic polarization tests on the alloy after low temperature surface oxidation
reveal an aqueous corrosion resistance comparable to AISI 304 steel and CoCrFeMnNi high entropy alloy. The Xray photoelectron spectroscopic studies confirmed that the free surface in the as-cast alloy is in partially oxidized
state. The same completely oxidizes after low-temperature surface oxidation. Such low temperature surface
oxidation improves pitting corrosion resistance in AlCuFeMn alloy due to increased metal/oxide layer resistance.
The electrochemical impedance spectroscopy tests coupled with microscopy confirmed that the principal
corrosion mechanisms in the alloy are of the uniform and pitting type. The energy dispersive spectroscopy experiments indicate that a copper oxide enriched layer is formed on the surface oxidized specimen during
corrosion
Characterization and analysis of the triglyceride transesterification process
No full textNuclear magnetic resonance (NMR) spectroscopy has been employed to study the triglyceride transesterification process and characterizes the triglyceride, fatty acid methyl esters, and valorized products from biodiesel waste. Detailed NMR studies such as 1H, 13C, DEPT-135, HMBC (1H-13C), HMQC (1H-13C), and COSY (1H-1H) have been performed to analyze the transesterification reaction mixture and the products. Both unused sunflower oil and used sunflower oil (waste cooking oil) were used as a triglyceride source for transesterification reaction. Zero-waste valorization of biodiesel waste is successfully demonstrated and the low-value byproduct is purified into a high-value glycerol product. Neutralization of the byproduct with hydrochloric acid produces a significant amount of salt that has been separated, washed with an organic solvent, and recrystallized to white crystalline potassium chloride. Free fatty acids and fatty acid esters have also been isolated from the acidified byproduct and utilized for surfactant preparation. Reduced pressure distillation of the aqueous glycerol layer followed by passing the distilled liquid through the resin column resulted in an odorless transparent viscous liquid. The zero-waste valorization of biodiesel waste realizes a holistic approach for resource management and sustainable development for future generations
A comparative study on flotation of coal using eco-friendly single reagent and conventional dual-reagent system
No full textThe continuous depletion of low ash coals and raising demand of clean coal due to increase in consumption in various sectors such as iron and steel industries, the washing of high ash coal has become inevitable. Froth flotation is one of the beneficiation methods in coal washing that exploits the surface hydrophobicity difference between coal, that is naturally hydrophobic, and its associated ash forming minerals that are commonly hydrophilic in nature. This natural hydrophobicity of coal surface acts as an advantage in reducing the ash content of coal by flotation as it is a surface-phenomenon based separation technique. In this study, a coking coal with 25.75% ash was subjected to beneficiation by flotation at two different size fractions of 100% passing 0.5mm and 0.25mm. The flotation studies on these two size fractions was studied using commercially used collector and frother. A newly developed reagent, Collector AB, synthesized from natural percussor was used as as coal collector. The collectors AB is environmentally non-hazardous and safe to use in coal washeries unlike most commercial coal collectors and hydrocarbon oils that are being used at large scale. The process optimization of the flotation reagents was studied at two different size fractions of the coal sample and the flotation efficacy was found to be comparable. Hence, this developed reagent would be alternative to commercially available flotation reagents and other hydrocarbon oils presently being used for coal flotation