Grinding characteristics of coal and petroleum coke/coal blends on utilization for combustion

ABSTRACT

Petroleum coke (PC) blend with coal is an attractive feedstock for combustion process. The present work investigates the grinding characteristics of PC blend with coal in a laboratory ball mill to meet an industrial tube mill conditions. Tests were carried out using a laboratory batch ball mill for optimal production of ?200 mesh size product. The ground products at different combinations were subjected to sink-float tests. Experimental results suggested that the petcoke with coal at 5.0% blend ratio was optimum for generation of ?200 mesh size product. It was also observed that increasing coal/petcoke blend ratio beyond 5.0% leads to a decrease in ?200 mesh size generation. The better performance could be achieved at the blending ratio of 5%, perhaps resulting from the synergistic effect of the blends. With the aforementioned blend ratio, the optimal condition of the milling time was found to be 3 h. The percentage of coal to the total charge and percentage of petcoke to the total charge of the ball mill product at various blends were also calculated for all the blends and at all grinding time intervals. The results obtained could provide a useful insight to predict the industrial mill performance.     

Milling and Classification of Printed Circuit Boards for Material Recycling

Recycling of waste electric and electronic equipment (WEEE) is an emerging issue due to its hazardous nature. It is important to identify an appropriate environment-friendly process to recover the valuables and for safe disposal. The present work deals with the two-stage crushing process followed by a circulating air classifier for the separation of metals and nonmetals from the printed circuit boards (PCB). The two-stage crushing process is deployed to liberate the valuables for an appropriate progeny size distribution. The metal content decreases as the particle size decreases below 0.5 mm. However, it increases metal content above 500 µm up to 1,800 µm. It is concluded that the metals primarily enriched in the size range of ?1.8 + 0.5 mm. The amount of metals and plastics present in each fraction is estimated. Among the classifier parameters, air flow velocity played a dominant role in metal enrichment. The material feed rate and rotating guide vane angle have no a significant effect on the enrichment of metals and nonmetals. The air flow velocity found was to be one of the crucial parameters for enrichment of metals. The superficial air flow velocity is optimized for efficient separation of metals and nonmetals of PCBs.     

Experimental and Simulation Studies on Milling of Rice Husk

A study was conducted to investigate the size reduction characteristics of rice husk in a batch ball mill. The most popular population balance model was chosen for the analysis. The model parameters are the breakage distribution function (β) and breakage rate function (α). Experiments are conducted with three different feed sizes of rice husk at three different ball charges. From the experimental data, the best fitting breakage distribution function parameter is found. The breakage rate function parameters with process variables such as feed size, ball charge were calculated. The best correlation for the parameter with process variables was obtained by multiple linear regression analysis. Additional experiments were also conducted at different process conditions to verify the correlation. The accuracy of the correlation is also verified for pet coke data of Ray (2000 Ray , P. 2000 . Studies on size reduction characteristics of petcoke using a ball mill. M.Tech. thesis, Indian Institute of Technology Madras, India.  [Google Scholar]). The correlation describes the experimental data with acceptable accuracy for rice husk and also for pet coke data within the range of process variables studied in this investigation. The calculated values of the breakage rate obtained through the developed correlations have been compared with the respective experimental values with root mean square error of 1.25% and correlation coefficient of 0.95. It is also found that the calculated values agree well with the experimental values.     

Inorganic nanotubes reinforced polyvinylidene fluoride composites as low-cost electromagnetic interference shielding materials

Novel polymer nanocomposites comprising of MnO₂ nanotubes (MNTs), functionalized multiwalled carbon nanotubes (f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f-MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10^-16S/m to 4.5 × 10^-5S/m (3.2 × 10^-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region.     

Computational Fluid Dynamics Simulation of a Quadrupole Magnetic Sorter Flow Channel: Effect of Splitter Position on Nonspecific Crossover

In the Quadrupole Magnetic Sorter (QMS) magnetic particles enter a vertical flow annulus and are separated from non-magnetic particles by radial deflection into an outer annulus where the purified magnetic particles are collected via a flow splitter. The purity of magnetically isolated particles in QMS is affected by the migration of nonmagnetic particles across transport lamina in the annular flow channel. Computational Fluid Dynamics (CFD) simulations were used to predict the flow patterns, pressure drop and nonspecific crossover in QMS flow channel for the isolation of pancreatic islets of Langerhans. Simulation results were compared with the experimental results to validate the CFD model. Results of the simulations were used to show that one design gives up to 10% less nonspecific crossover than another and this model can be used to optimise the flow channel design to achieve maximum purity of magnetic particles.     

Black Phosphorus Nanosheets: Synthesis,Characterization and Applications

Black phosphorus (BP) is an emerging two‐dimensional (2D) material with a natural bandgap, which has unique anisotropy and extraordinary physical properties. Due to its puckered structure, BP exhibits strong in‐plane anisotropy unlike other layered materials. The bandgap tunability of BP enables a wide range of ultrafast electronics and high frequency optoelectronic applications ranging from telecommunications to thermal imaging covering the nearly entire electromagnetic spectrum, whereas no other 2D material has this functionality. Here, recent advances in the synthesis, fabrication, anisotropic physical properties, and BP‐based devices including field effect transistors (FETs) and photodetectors, are discussed. Recent passivation approaches to address the degradation of BP, which is one of the main challenges to bring this material into real world applications, are also introduced. Finally, a comment is made on the recent developments in other emerging applications, future outlook and challenges ahead in BP research.     

Particle Classification Optimization of a Circulating Air Classifier

ABSTRACT

Undoubtedly, wet processing of ores requires huge quantity of water. This provides enough incentive for dry beneficiation of ores which has great promise predominantly from an environmental standpoint and water scarcity in the mining and processing industries. Therefore, the present investigation made an attempt to effectively address the issues related to dry classification of minerals. In this study, a three-factor-three-level Box–Behnken factorial design combined with response surface methodology (RSM) was employed for modeling and optimization of operational parameters of a circulating air classifier. The three main operating parameters studied were air flow rate, feed rate, and guide vane angle. The primary and interaction effects of operating variables were evaluated using RSM while generating the second-order response functions for both the responses, cut size and size selectivity increment. The values of cut size and size selectivity increment obtained using predictive models were in excellent agreement with the observed values. The optimization of these predictive response models resulted in the optimal values of air flow rate, feed rate, and guide vane angle for achieving better classification efficiency. This study establishes that the Box–Behnken factorial design combined with RSM effectively model the performance of circulating air classifier.     

Improving Strength of Stainless Steel/Aluminum Alloy Friction Welds by Modifying Faying Surface Design

Conventionally in friction welding, the rubbing or faying ends of the base material rods are square turned. For the case of dissimilar friction welding, this design is not optimum because of differential flow behavior of the materials. When, only one of the materials deforms preferentially, the actions of cleaning and expulsion of oxides and impurities from the interface would not be as effective. This will adversely affect the joint properties. In this study, alternate designs of faying surfaces such as providing taper (external and internal) and smoother surfaces are compared with the square cut design. The aim was to study how the faying surface conditions of the stronger material affect the flow behavior of the weaker material. By affecting better flow behavior, the intention was to expel intermetallics and other impurities from the interface, and thereby improve joint properties. Friction welding of stainless steel with aluminum alloy (aluminum-magnesium-silicon) was studied. The joints were evaluated for strength and it is found that the external tapered system has the best strength. Different characterization techniques such as optical microscopy, scanning electron microscopy, x-ray diffraction were carried out to observe different phases, microstructure zones, etc., at the interface. Finally, possible reasons for the better strength of tapered system were discussed.     

Settling characteristics of ultrafine iron ore slimes

The slurry settling characteristcs are the most important to design a thickener in process industries.In this work,the iron ore slurry from the screw classifier overflow was used for the settling study...     

Fruit recognition from images using deep learning applications

Multimedia Tools and Applications - Smart imaging devices have been used at a rapid rate in the agriculture sector for the last few years. Fruit recognition and classification is noticed as one of...