Formation and Phase Behavior of Winsor Type III <Emphasis Type="Italic">Jatropha curcas</Emphasis>-Based Microemulsion Systems

The formation and phase behavior of Jatropha curcas-based microemulsion systems, which could potentially be used in enhanced oil recovery applications, has been investigated. Winsor type III microemulsions were obtained by adding n-octane to Winsor type I microemulsion systems prepared using various concentrations of alkyl polyglucoside (APG). To optimize the formulation of type III microemulsion systems, five different types of co-surfactants, i.e. normal butyl alcohol (NBA), isobutyl alcohol, isopropyl alcohol, fatty acid alcohol C8 (FAC8) and fatty acid alcohol C8/C10 (FAC8/C10) were used. The microemulsion phase behavior was determined along with particle size distributions by dynamic light scattering measurements. Results show that the optimum Winston type III system can be achieved by mixing 3 wt% of NBA, 1 wt% APG and 3 wt% NaCl. At the optimum formulation, the IFT reached a minimum value (0.016 mN/m) and formed very small emulsion droplets with a narrow particle size distribution.     

Experimental evaluation of quinolinium and isoquinolinium derivatives as corrosion inhibitors of mild steel in 0.5 M H<Subscript>2</Subscript>SO<Subscript>4</Subscript> solution

The 1-methylquinolinium iodide (I) Qui⁺, I^– and 2-methylisoquinolinium iodide isoQui⁺, I^– were investigated as a corrosion inhibitors for mild steel in sulfuric acid using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The results indicated that the corrosion inhibition efficiency and extent of surface coverage were increased with increase in inhibitors concentrations. Polarization curves revealed that both inhibitors acted as a mixed-type inhibitor. The thermodynamic parameters were evaluated for corrosion inhibition process. The adsorption of both inhibitors on mild steel surface obeyed Langmuir adsorption isotherm.     

Advances in reduction of NOx and N2O1 emission formation in an oxy-fired fluidized bed boiler

Fossil fuel combustion is one of the major means to meet the mounting global energy demand. However, the increasing NO_x and N₂O emissions arising from fossil fuel combustion process have hazardous effects. Thus, mitigating these gases is vital to attain a sustainable environment. Interestingly, oxy-fuel combustion in fluidized bed for carbon capture and minimized NO_x emissions is strongly sustainable compare to the other approaches. It was assessed that NO_x formation and fuel-N conversion have significant limitation under oxy-fluidized bed compared to air mode and the mechanism of NO_x formation is still deficient and requires further development. In addition, this review paper discussed the potential of primary measure as low emission process with others supplementary techniques for feasible NO_x reduction. The influences of combustion mode, operating parameters, and reduction techniques such as flue gas recirculation, oxygen staging, biomass co-firing, catalyst, influence of fluidized bed design and structure, decoupling combustion and their merges are respectively evaluated. Findings show that significant minimization of NO_x emission can be achieved through combination of primary and secondary reduction techniques.     

Quartz Ore Beneficiation by Reverse Flotation for Silicon Production

Silicon - In this work the reverse flotation as beneficiation process for high-purity silica valorization from Draissa quartz deposits (Algeria) is studied as a potential raw material for...     

Ultrasound-Assisted Aromatisation with Condiments as an Enabling Technique for Olive Oil Flavouring and Shelf Life Enhancement

Olive oil flavour represents the most important factor that influences customer’s perception for quality. In this study, an innovative aromatisation approach that enhanced quality and shelf life of olive oil is tested by means of in situ ultrasound-assisted extraction of Carum carvi L. seeds in olive oil. After the flavouring process, carvone and limonene, representing 99 % of caraway essential oil, were identified in virgin olive oil as revealed by headspace solid-phase microextraction gas chromatograph coupled to mass spectrometer (HS-SPME gas chromatograph (GC)/mass spectrometer (MS)) analyses. Furthermore, kinetic studies indicate that flavouring rate in ultrasound-assisted system is faster than conventional aromatisation producing very stable aromatised oil with no changes in quality. This fact is attributed to ultrasound contribution to mass transfer intensification of essential oil components from seeds to the bulk medium, confirmed by scanning electron micrograph (SEM) micrographs in which cell damage and exudation of its main content are illustrated. However, it is important to note that ultrasound-treated samples produce higher degrees of conjugated dienes and conjugated trienes compared to conventional maceration. Nevertheless, this increase is not alarming and remains within permitted values of the European Community and the International Olive Oil Council (IOOC). Ultrasound-flavouring system stands as a fast alternative aromatisation method, which allows on top shelf life enhancement and olive oil quality preservation.     

Effect of Inclination on Heat Transfer and Fluid Flow in a Finned Enclosure Filled with a Dielectric Liquid

The problem of two-dimensional natural convection flow of a dielectric fluid in a square inclined enclosure with a fin placed on the hot wall is investigated numerically. The fin thickness and length are 1/10 and 1/2 of the enclosure side, respectively. The Rayleigh number is varied from 10³ to 5 × 10⁵ and the solid to fluid thermal conductivity ratio is fixed at 10³. The enclosure tilt or inclination angle is varied from 0° to 90°. The streamlines and isotherms within the enclosure are produced and the heat transfer is calculated. It is found that for 2.5 × 10⁴ ≤ Ra ≤ 2.5 × 10⁵, the average Nusselt number is maximum when γ = 0° and minimum when γ = 90°. For Ra = 5 × 10⁵, the values of enclosure tilt angle for which the average Nusselt number is maximum or minimum are completely different due to the transition to unsteady state. In this case, the maximum heat transfer is obtained for γ = 60°, while the minimum heat transfer is predicted for γ = 0°. Monomial correlations relating the average Nusselt number with the different values of the Rayleigh number from 10⁴ to 10⁵ are determined for two different angles, γ = 0° and γ = 90°.     

Stability of Swirling Flows with Heat Transfer in a Cylindrical Enclosure with CO/Counter-Rotating End Disks Under an Axial Magnetic Field

In this article, a numerical study of swirling flows with heat transfer generated by two rotating end disks (co- and counter-rotating) inside a cylindrical enclosure having an aspect ratio equal to 2, filled with a liquid metal, and submitted to a vertical temperature gradient and an axial magnetic field is studied. The governing Navier-Stokes, energy, and potential equations along with appropriate boundary conditions are solved by using the finite-volume method. The flow and temperature fields are presented by stream function and isotherms, respectively. This flow is very unstable and reveals a great richness of structures. In an oscillatory regime, results are presented for various values of the Hartmann number, Ha = 5, 10, 20 and 30, and Richardson numbers, Ri = 0, 0.5, 1, 2 and 4, in order to see their effects on the value of the critical Reynolds number, Re_cr. Stability diagrams are established according to the numerical results of this investigation. These diagrams show the dependence of Re_cr with the increase of Ha for various values of Ri. The flow between co-rotating end disks is very different from the flow between counter-rotating end disks. Finally, this study confirms the possibility of stabilization of a liquid metal flow by application of an axial magnetic field.     

Tetragonal Tungsten Bronze Niobate, K0.2Sr0.4NbO3: A New Material for Capacitors with Flat Dielectric Curves

A new ceramic for capacitors, which exhibits flat dielectric curves with relative permittivity values (ɛ) as high as 3000 (Y7R or X7R class), has been synthesized. Use of a niobate, K_0.2Sr_0.4NbO₃ (KSN), with a tetragonal tungsten bronze structure (TTB), as a major phase for the fabrication of such ceramics is shown for the first time. Nevertheless, the addition of perovskites as minor agents—PbMg_1/3Nb_2/3O₃ (PMN)—is necessary to obtain stable temperature. Moreover, the use of lithium salts as sintering agents has been shown to be important for the fabrication of these ceramics.