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Effect of reagents on flotation kinetics of differently sized feeds
No full textThe particle size and reagents are the most important parameter in flotation performance. Flotation kinetics models are used to define the rate of flotation and ultimate recovery. In this paper, flotation kinetics studies on a composite feed of -0.5 mm and three split-sized feeds including -0.5+0.25, -0.25+0.1, and -0.1 mm were conducted by using four different reagent combinations. The experimental data in terms of both combustible recovery - time and ash recovery - time were fitted with six different kinetic models to evaluate the best-fitted kinetics model. The feeds of different sizes responded differently to flotation kinetics with different reagent combinations. The combustible particles for all the sized feeds followed only first-order kinetics, whereas ash-bearing particles followed the second-order kinetics. Although coarsest particles have the lowest kinetics reported in the literature, synthetic collector and synthetic frother exhibited the highest kinetics by coarsest feed and lowest by intermediate-sized feed. Other reagent combinations show the highest kinetics by intermediate-sized feed. The selectivity of a particular reagent combination was found to be different for different sized feeds
Distribution of Rare Earth Elements in Coal and Coal Fly Ash
No full textCoal fly ash is one of the potential resource
for the recovery of REEs from it. Coal fly ash is obtained as a by-product after combustion of coal in thermal power plant. On an average, the coal-based fly
ash throughout the world contains around 400 mg/kg of REEs. As we know that energy is the basic requirement for the overall development of nations, it plays a very crucial role in their economic development. Developing countries are dependent on coal as natural resources for electricity production by thermal power
plant which generate large amount of coal fly ash as a secondary product. About 70–75% of India’s and 40–45% of global energy requirement are fulfilled by coal-based thermal power plant which eventually
produces a large amount of fly ash. India utilizes
60–70% and world utilizes about 45–50% of coal fly ash in different areas like
cement industry, in roads and embankment construction, Mine filling, making
bricks, and tiles. The rest amount of fly ash remains unutilized and is
a global concern to address. Abundance of REEs in coal fly across the world is about
5–10 times more than the concentration of REEs in coal. CFA is a very potential
source of rare earth elements. This chapter reviews the detailed study of coal and
coal fly ash, distribution of REEs in coal, coal-based fly ash, and different methods
for the recovery of REEs from coal fly ash
Resistance of Alkali-Activated Blended Volcanic Ash-MSWI-FA Mortar in Sulphuric Add and Artificial Seawater
No full textThis paper investigates the resistance of alkali-activated binder from volcanic ash (VA) + Municipal Solid Waste Incinerator Fly Ash (MSWI-FA) system exposed into sulphuric acid solution and artificial seawater at 56 days. The effect of these aggressive media on the physical, structural, mechanical and microstructural properties of alkali-activated mortars was discussed. The degradation was studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The decrease of compressive strength after 56 days was 9.10%, 22.08%, 32.5% in artificial seawater, 2% H2SO4 and 4% H2SO4, respectively. The loss of strength in both media is primarily due to the fact that the water molecules present in these media penetrated into the pore cavities between binders and aggregates, making them weak. In an acidic medium, it is also due to the decalcification and depolymerization reactions whereas in seawater medium, it is attributed to the movement of content ions and probable formation of Friedel's salt. The results disclose that VA + MSWI-FA based alkali activated materials resist better in seawater than in sulphuric acid solution. Synergistic use of volcanic ash and MSWI-FA for construction materials through alkaline activation looks like the upcoming trend to valorize these wastes
Charge Transport through Functionalized Graphene Quantum Dots Embedded in a Polyaniline Matrix
No full textNitrogen-functionalized graphene quantum dots embedded in a polyaniline matrix (NGQD-PANI) are extremely promising candidates for the development of next-generation sensors and for thermoelectric materials design with the distinct advantage of tunability of electronic properties by controlled doping and/or by controlling the inherent disorder in the microstructure. While their application is increasing in photovoltaics, energy storage, and sensing technologies, a clear understanding of conduction in these hybrid systems is lacking. Here, we report a comprehensive study of NGQD-PANI composites with varying NGQD doping levels over a wide range of temperature. We show distinct regimes of conduction as a function of temperature, which include: a transition from Efros-Shklovskii and Larkin-Khmelnitskii variable range hopping at low temperatures to thermally driven electron transport at higher temperatures. Importantly, we find a remarkable 50-fold enhancement in conductivity for 10% NGQD-doped samples and tunability of the crossover temperature between different regimes as a function of the applied voltage bias and doping. Our work provides a general framework to understand the interplay of extrinsic parameters like temperature and voltage bias with intrinsic material properties like doping, which drives the electronic properties in these hybrid systems of technological importance
Significance of washability on heat-altered coal from Jharia and Raniganj Coalfields, India
No full textThe present investigation was aimed to characterise the natural coke-coal (NCC) or heat-altered coal products through washability, technological property and petrography. NCC of Permian age from Jharia and Raniganj coal basins, India were subjected to beneficiate and the microscopy was performed on the different specific gravity fractions. The yield of washed coals and contents of macerals showed many variations in both the case studies due to the influence of igneous intrusion. However, we can use both NCC products in the different industrial application such as metallurgy, carbon artefact, power plant, fluidised bed combustion (FBC) and for blending purpose despite of their mutual differences
Blast Furnace Flue Dust as a Potential Carbon Additive in Hematite Ore Pellet
No full textCoke or anthracite coal is traditionally used as the carbon source in the hematite ore pellet for providing
in-situ heat and enhancing diffusion bonding and slag bonding. Blast furnace flue dust (BFD) is a waste
material, which contains a significant quantity of carbon may be another possible option of carbon source.
However, the feasibility of using this material for the preparation of blast furnace quality pellet from
hematite ore needs to be studied. In the present study, the burning characteristics of BFD in pellet have
been studied and compared with that of coke fines. The characteristics of the pellets prepared with the
above two carbon sources have been compared to assess the feasibility of using BFD as a carbon source in
the hematite pellet. While 1% C level in BFD-added pellet shows the optimum result, 1.5% C level in cokeadded pellet shows that. All properties of pellets improve significantly by the addition of carbon in form of
either BFD or coke both in acidic and basic conditions. Induration temperature could be reduced by
50–75 K in both cases. However, better pellet properties in terms of cold crushing strength (277 kg/pellet)
and reducibility index (81%) have been observed in using BFD. This study optimizes the process
parameters to utilize the BFD as a carbon additive in hematite pellet both in acidic and basic condition
replacing coke fines and establishes that BFD is a potential carbon source to achieve better pellet
properties without any adverse effect
Electrical transport through pelletized tablet of silicene like quasi 2D crystalline silicon
No full textSilicene, the silicon-based 2D analogue of graphene, is predicted to have many exotic properties. However, most of the theoretically predicted phenomena have not yet been experimentally verified. In this work, we have prepared silicene-like, quasi 2D nanostructures via topochemical exfoliation of layered silicide and hot-pressed the dried powders to form bulk pellets. Temperature dependent electrical transport characteristics of pelletized silicene were investigated and found to exhibit evidence of some theoretically predicted features. The current–voltage (I-V) characteristics of the pelletized samples are non-linear, asymmetric about V = 0 and bears clear signature of negative differential resistance (NDR). The heuristic study provides interesting insights into the transport properties of bulk pellets of silicene and opens up the possibility of many applications
Evaluation of bond interface characteristics of rotary friction welded carbon steel to low alloy steel pipe joints
No full textIn the present investigation, rotary friction weld joints were prepared between carbon steel and low alloy steel pipes. These types of similar and dissimilar configurations are in general, used for drill pipe joining. Low alloy steel for the friction welding in dissimilar configurations were used in two different microstructure state; a) as-received and b) quenched and tempered. The friction weld joints showed three distinct weld microstructure characteristics; a) radial plastic flow, b) axial plastic flow and, c) partial heat affected zone, for joining configurations. In general, microstructure characterization revealed grain size refinement and carbide precipitation in the vicinity of bond interface for all types of similar and dissimilar steel joining conditions. A characteristic bond layer width of ~2 μm was developed between the dissimilar steel weld joints whereas it was found to be absent for the similar weld joints. These weld joints were evaluated for their mechanical properties by using conventional tensile tests and furthermore by automated ball indentation technique. The study has also shown that in the case of dissimilar steel joints the mechanical properties of the bond interface can be obtained aptly by using an automated ball indentation technique. The quench and temper treatment given to the low alloy steel resulted in the improved bond interface strength. The improvement of the mechanical properties of the weld joints was attributed to the synergistic effect of grain size refinement and tempered martensite microstructure
Beneficiation of Low-Grade Rare Earth Ore from Khalzan Buregtei Deposit (Mongolia) by Magnetic Separation
No full textThe global demand for rare earth elements (REEs) is expected to increase significantly because of their importance in renewable energy and clean storage technologies, which are critical for drastic carbon dioxide emission reduction to achieve a carbon-neutral society. REE ore deposits
around the world are scarce and those that have been identified but remain unexploited need to be developed to supply future demands. In this study, the Khalzan Buregtei deposit located in western Mongolia was studied with the aim of upgrading low-grade REE ore via magnetic separation
techniques. The total REE content in this ore was ~6720 ppm (~3540 ppm light REE (LREE) + ~3180 ppm heavy REE (HREE)) with bastnaesite, pyrochlore, synchysite, and columbite-(Fe) identified as the main REE-bearing minerals. As the particle size fraction decreased from 4.0 + 2.0 mm to
0.5 + 0.1 mm, the recovery by dry high-intensity magnetic separation (DHIMS) increased from 20% to 70% of total rare earth oxide (TREO) while the enrichment ratio reached 2.8 from 1.3. Although effective, gangue minerals such as quartz and aluminosilicates were recovered (~22%) due most
likely to insufficient liberation. Meanwhile, the wet high-intensity magnetic separation (WHIMS) could produce a magnetic concentrate with TREO recovery of ~80% and enrichment ratio of 5.5 under the following conditions: particle size fraction, 106 + 75 m; feed flow rate, 3.2 L/min; magnetic induction, 0.8 T. These results indicate that combining DHIMS and WHIMS to upgrade the low-grade
REE ore from the Khalzan Buregtei deposit is an effective approach
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