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In hydrometallurgical and mineral processing operations, slurries are often prepared at very small grind sizes and high solids concentrations. The presence of yield stress or flow limits results in flow anomalies as the slurry tends to stagnate close to vessel bottom, walls, and at any internal surface. The preparation of high-concentration slurries preferably in low shear rate ranges consuming less power is an integral part of high-concentration slurry transportation systems. Therefore, during mixing of such concentrated slurries, the selection of appropriate agitation equipment for preparation of a homogeneous suspension requires a thorough investigation. The rheological behavior of ground manganese nodule samples in solids concentration range of 55–65% by weight using both distilled water and sea water as mediums have been evaluated and the discrepancy in yield stress and plastic viscosity values affected by solids concentration and medium has been discussed and presented in the paper. The performance characteristics of a helical ribbon mixer influenced by fluid rheology, medium, and agitator rotational speed were evaluated. The appropriateness of the agitator for preparation of high-concentration manganese nodule slurry was further substantiated by comparing the experimental power consumption data with the theoretical power consumption values computed using Bakker and Gates correlations. [ABSTRACT FROM AUTHOR]

Mine backfilling with power plant ash is gaining increasing attention from the power and mining industries for its bulk disposal. In the USA and other countries, mine backfilling with ash is considered as a viable option for stability improvement, subsidence control, and mine site rehabilitation. This paper presents the results of rheological studies conducted on fly ash and mixtures of fly ash and bottom ash samples collected from NTPC Talcher, Odisha. The complex hydro-mixture slurry indicated non-Newtonian pseudo-plastic behavior in the mass concentration range of 60–67.5%. A non-Newtonian power law head loss model was used to evaluate the head loss of ash slurry in pipelines having nominal bores in the range of 100–300 mm. The results indicated that the addition of bottom ash to fly ash slurry at a given solids concentration has a beneficial effect in reducing the pumping power requirement. A design chart for the fly ash mixture slurry has been formulated indicating the variation in backfilling rate with relative head requirements for a given length of pipeline for a range of pipe sizes and transport velocities. This is expected to provide relevant pipe flow and operational conditions for bulk disposal of fly ash for mine backfilling purpose. [ABSTRACT FROM AUTHOR]

This study illustrates a density functional theory (DFT) based approach to design the amine collectors with regards to their interaction with the quartz surface. Mechanism of interaction of primary aliphatic amines and their ether and ester derivatives with the quartz surface has been established. Hydrogen bond geometries and adsorption energies as calculated using DFT reveal that ester amines are stronger surfactants compared to the ether amines and primary alkyl amines. Simulation studies carried out for the different amines with number of carbon atoms varying from 10 to 18 suggest that increasing the number of carbon atoms in the alkyl chain enhances the interaction, but not beyond C 14 for primary amines and C 16 for its ether and ester derivatives. Presence of both ether and ester group in the alkyl chain facilitates its interaction strength. Adsorption strength of C 12 amine containing both ether and ester amine is almost equivalent to that of C 16 ester amine. [ABSTRACT FROM AUTHOR]

This paper presents the application of the Taguchi experimental design in developing nanostructured yittria stabilized zirconia (YSZ) coatings by plasma spraying process. This paper depicts dependence of adhesion strength of as-sprayed nanostructured YSZ coatings on various process parameters, and effect of those process parameters on performance output has been studied using Taguchi's L16 orthogonal array design. Particle velocities prior to impacting the substrate, stand-off-distance, and particle temperature are found to be the most significant parameter affecting the bond strength. To achieve retention of nanostructure, molten state of nanoagglomerates (temperature and velocity) has been monitored using particle diagnostics tool. Maximum adhesion strength of 40.56 MPa has been experimentally found out by selecting optimum levels of selected factors. The enhanced bond strength of nano-YSZ coating may be attributed to higher interfacial toughness due to cracks being interrupted by adherent nanozones.

A series of experiments were carried out with three native strains of microalgae to measure growth rates, biomass, and lipid productivities. Scenedesmus sp. IMMTCC-6 had better biomass growth rate and higher lipid production. The growth, lipid accumulation, and carbon dioxide (CO2) consumption rate of Scenedesmus sp. IMMTCC-6 were tested under different NaOH concentrations in modified BBM. The algal strain showed the maximum specific growth rate (0.474/day), biomass productivity (110.9 mg l(-1) d(-1)), and CO2 consumption rate (208.4 mg l(-1) d(-1)) with an NaOH concentration of 0.005 M on the 8(th) day of cultivation. These values were 2.03-, 6.89-, and 6.88-fold more than the algal cultures grown in control conditions (having no NaOH and CO2). The CO2 fixing efficiency of the microalga with other alternative carbon sources like Na2CO3 and NaHCO3 was also investigated and compared. The optimized experimental parameters at shake-flask scale were implemented for scaling up the process in a self-engineered photobioreactor. A significant increase in lipid accumulation (14.23% to 31.74%) by the algal strain from the logarithmic to stationary phases was obtained. The algal lipids were mainly composed of C16/C18 fatty acids, and are desirable for biodiesel production. The study suggests that microalga Scenedesmus sp. IMMTCC-6 is an efficient strain for biodiesel production and CO2 biofixation using stripping solution of NaOH in a cyclic process.