Particle Shape,Density, and Size Effects on the Distribution of Phase Holdups in an LSCFB Riser

Electrical resistance tomography (ERT) as a non‐invasive technique based on conductivity measurement of the continuous phase was employed for the study of phase holdup in a liquid‐solid circulating fluidized bed (LSCFB). Local solid holdup was also measured by an optical fibre probe and pressure transducers to compare and verify the results obtained by ERT. Good agreement was observed among the three methods. Tap water was used as the continuous and conductive phase and glass beads (spherical shape) and lava rocks (irregular shape) of two different sizes were used as the solid and non‐conductive phase. Radial non‐uniformities of solid holdups were observed for all four types of particles under different superficial liquid velocities in different axial locations. The solid holdup was higher in regions close to the wall and low in the central region. Non‐uniformity in the phase holdup decreased with increasing liquid velocity. The axial flow profile was found uniform along axial locations of the riser except at the lower location closer to the distributor zone.     

Dielectric behavior of insulating materials under liquid nitrogen

Measurements were made to assess the AC breakdown voltages in liquid nitrogen (LN/sub 2/) with different electrode configurations such as sphere-sphere, needle-needle, hemisphere-hemisphere, plane-plane, sphere-needle, etc. Experimental results reveal that the breakdown voltage is a function of electrode geometry and gap length. This study also addresses the effect on the breakdown strength of solid insulating materials under LN/sub 2/ environment with a sphere-sphere electrode configuration. In this paper, special emphasis has been attributed to the effect on loss index of a variety of dielectrics dipped in LN/sub 2/. The measured values of breakdown strength and loss index have been compared with those obtained under atmospheric condition. The study reveals that the breakdown strength of cellulosic materials like paper or pressboard increases manifold while the loss index decreases significantly when dipped in LN/sub 2/ with variations of the order of 50% to 90%. However, for impervious noncellulosic materials like Perspex (acrylic glass) or presspahn, the increase in breakdown strength is not that pronounced and the decrease in loss index is of the order of 2 to 30%.     

Study of the Theta Pinch Plasma Numerically by Varying β Parameter and Applied Current

The implosion dynamics of theta pinch is studied by simulation technique through snow plow model with the help of MATHEMATICA software. The differential equation of motion for plasma implosion is derived and solved numerically by using this software. The variation effects of β parameter (plasma kinetic pressure to plasma magnetic pressure ratio) and applied current is examined on normalize radius of imploded plasma by variations in normalized time. The graphs between normalized radius and normalized time of imploded plasma indicates that theta pinching effect can be improved by decreasing β value and increasing in the magnitude of applied current.     

A hydrodynamic model of a circulating fluidised bed with low‐density particles

In this study, a two‐dimensional mathematical model was developed considering the hydrodynamic behaviour of a circulating fluidised bed biomass gasifier (CFBBG), which is also applicable for other low‐density particles. In the modelling, the CFB riser was divided into two regions: a dense region at the bottom and a dilute region at the top of the riser. Kunii and Levenspiel's [Kunii and Levenspiel, Powder Technol. 61, 193‐206 (1990)] model was adopted to express the vertical solids distribution with some other assumptions. Radial distributions of bed voidage were taken into account in the upper zone by using Zhang et al.'s [Zhang et al., Chem. Eng. Sci. 46(12), 3045‐3052 (1991)] correlation. For model validation purposes, a cold model CFB was employed, in which sawdust was transported with air as the fluidising agent. The column is 10 m in height and 280 mm in diameter, and is equipped with pressure transducers to measure axial pressure profile and with a reflective optical fibre probe to measure local solids holdup. A satisfactory agreement between the model predictions and experimental data was found. © 2011 Canadian Society for Chemical Engineering     

Crystallization analysis fractionation of poly(ethylene-co-styrene) produced by metallocene catalysts

Ethylene homo polymer and ethylene–styrene copolymers were synthesized using Cp₂ZrCl₂ (1)/methyl aluminoxane (MAO) and rac-silylene-bis (indenyl) zirconium dichloride (2)/MAO catalyst systems by varying styrene concentration and reaction conditions. Crystallization analysis fractionation (CRYSTAF), DSC, FTIR and ¹H NMR spectroscopy were used for characterizing the synthesized polymers. Interestingly, styrene was able to increase the activity of 1/MAO and 2/MAO catalyst systems at low concentrations, but at higher concentrations the activity decreases. The 1/MAO system at low and high pressure was unable to incorporate styrene, and the final product was pure polyethylene. On the other hand, with 2/MAO polymerization of ethylene and styrene yielded copolymer containing both styrene and ethylene. Results obtained from CRYSTAF and DSC reveal that on using 1/MAO system at high pressure, the resulting polymer in the presence of styrene has similar crystallinity as the polymer produced without styrene. Using both 1/MAO at low pressure and 2/MAO leads to decrease in crystallinity with increase in styrene concentration, even though the former does not incorporate styrene.     

The role of Zr-rich cores in strength differential effect in an extruded Mg–Zn–Zr alloy

This work examines the effects of extrusion parameters namely ratio and temperature on recrystallization behavior of a Mg–Zn–Zr alloy, and their consequent effects on anisotropy in the mechanical properties. Upon extrusion, the characteristic Zr-rich cores that do not recrystallize form the so-called “soft stringers” which are deformed bands elongated in the extrusion direction and curled around the extrusion axis. At higher extrusion ratio, there is more twinning contribution and the DRX response is improved, making the recryatallized grains finer and increasing the proportion of recrystallized Zr-rich cores. A basal texture after extrusion and the directional activation of tensile twinning cause anisotropy in the mechanical properties. In addition, the microstructural features such as large unrecrystallized regions and coarse crystallized grains also contribute in the strength differential effect. Further slip in the strain-hardened unrecrystallized grains is inhibited while twin activation under favorable orientation becomes easier in the coarse recrystallized grains. A higher proportion of large unrecrystallized and coarse crystallized gains in the case of lower extrusion ratio result in a much higher strength differential effect (100 MPa) in comparison to the one caused by the crystallographic texture only (25 MPa).     

Agglomeration of Makarwal coal using soybean oil as agglomerant

The study was carried out for beneficiation of Makarwal coal using soybean oil as agglomerant. The effect of six parameters – pH, mesh size of coal particles, slurry ratio, stirring speed, soybean oil concentration, and time of agglomeration – was investigated to reduce ash and sulfur from Makarwal coal and to enhance the gross calorific value. In the cleaned product obtained after the agglomeration process, the gross calorific value was increased from 4900 to 7115 Kcal/kg. The ash of agglomerates was reduced from 30% to 7.5% and sulfur was reduced from 5.4% to 2.0% The optimum operating conditions were concentration of soybean oil 10 mL, pH 9, stirring speed 2800 rpm, mesh size 200, coal to water ratio of 15:450 (W/V), and time of agglomeration 20 min. Significant reduction in ash and sulfur showed the effectiveness for agglomeration of Makarwal coal using soybean oil as the agglomerant. The final product thus obtained may be used efficiently in various energy recovery schemes.     

Controlled release of Montelukast Sodium from pH-sensitive injectable hydrogels

pH sensitive hydrogels showed excellent drug release properties, with promise for other biomedical applications. Also, the impact of molecular weight (MW) and degree of deacetylation (DDA) of chitosan on the fabricated chitosan/poly (vinyl alcohol) (3:1 mol ratio) hydrogel with selective silane crosslinker amount was evaluated for controlled drug delivery. The FTIR spectroscopy confirmed the incorporated components and the developed interactions among the polymer chains. The hydrogel characteristics were expressed by their responsive behaviour in different environments (water, ionic media and pH). The hydrogel sample (CH1000) having chitosan with higher MW and DDA exhibited more thermal stability and bacterial growth inhibition against E.coli. All hydrogels exhibited maximum swelling at basic and neutral pH and less swelling was observed in acidic media. For drug release analysis performed in simulated gastric fluid, hydrogel showed controlled drug release in 2 h but it was more than 10%, consequently cannot be used for oral purpose. In simulated intestinal fluid, hydrogels exhibited more than 80% release within 90 min. This characteristic phenomenon at neutral pH empowered hydrogel appropriate towards injectable and targeted controlled release of applicable drug. It was concluded that the prepared hydrogel can be administered directly into the venous circulation through syringe and can be used with better results for biomedical applications.