Regular Article
Separation Technology,
S. Ghasemi; A. Behnamfard; R. Arjmand
Abstract
The thickening of the iron ore tailings allows process water to be partially recovered and recirculated, also it reduces the fresh water consumption, which results in lower operating costs and less environmental impacts. The settling characteristics of the mineral components of an iron ore tailing in ...
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The thickening of the iron ore tailings allows process water to be partially recovered and recirculated, also it reduces the fresh water consumption, which results in lower operating costs and less environmental impacts. The settling characteristics of the mineral components of an iron ore tailing in the thickening process may be different under various pulp conditions. Hence, the study of the characteristics of the mineral components of the iron ore tailings separately can provide very useful information about the thickening of an iron ore tailing. In this research, the settling behavior of the main mineral components of iron ore tailings including quartz and magnetite have been investigated under various operational conditions. The quartz and magnetite showed different settling behaviors, so as the maximum settling rate of quartz was achieved under different pulp conditions than that of magnetite was. There was a big difference between the maximum settling rates of quartz and magnetite, as the maximum settling rates of quartz and magnetite were 197 and 873 m/h respectively. In the thickening of an iron ore tailing, the pulp conditions must be set based on the settling behavior of the mineral component with the lowest settling rate.
Regular Article
Reaction Engineering, Kinetics and Catalysts,
M. Takht Ravanchi; S. Sahebdelfar; M. Rahimi Fard; H. Moosavi
Abstract
The impregnation of the alumina support with the PdCl2 solution was investigated in batch and semi-batch operation modes using a recycle packed-bed reactor. The UV-visible analysis was used to evaluate the kinetics of the adsorption of Pd on the alumina support. The adsorption data related to transient ...
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The impregnation of the alumina support with the PdCl2 solution was investigated in batch and semi-batch operation modes using a recycle packed-bed reactor. The UV-visible analysis was used to evaluate the kinetics of the adsorption of Pd on the alumina support. The adsorption data related to transient palladium showed that the adsorption of Pd was very rapid and completed within few minutes. Bi-metallic Pd-Ag/Al2O3 catalysts were synthesized by the sequential impregnation method. CO-chemisorption, CO-TPD and FE-SEM tests were used to characterize the synthesized bi-metallic samples. The catalytic performance of the samples was evaluated for the tail-end acetylene selective hydrogenation process in a fixed-bed reactor. Moreover, the deactivation of the catalysts was evaluated mathematically by the integral method of analysis, considering reaction kinetics as power laws in terms of nth orders in H2 and C2H2 partial pressures. It was observed that by the batch-wise addition of the Pd precursor solution, a sample, with the lowest amount of Pd dimmers that had the highest ethylene selectivity and lowest hydrogenation reaction rate, was obtained.
Regular Article
Thermodynamics,
Gh. Moradi; H. Hemmati
Abstract
The Dry Reforming of Methane, which uses methane and carbon dioxide, the two greenhouse gasses, to produce synthesis gas, has received considerable attention recently. In this work, the equilibrium conversion that is the maximum possible conversion has been obtained experimentally and theoretically. ...
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The Dry Reforming of Methane, which uses methane and carbon dioxide, the two greenhouse gasses, to produce synthesis gas, has received considerable attention recently. In this work, the equilibrium conversion that is the maximum possible conversion has been obtained experimentally and theoretically. The equilibrium concentration for the Dry Reforming of Methane (DRM) has been calculated using Thermodynamic equilibrium and compared with the experimental equilibrium concentration. The reaction coordinate (ε), Gibbs free energy (G), reaction equilibrium constant (K), and reaction stoichiometric coefficients are used for the calculation of the reaction progress and the equilibrium composition in DRM at different temperatures. These parameters have been calculated by two primary methods, direct and Lagrange, and compared with an empirical equilibrium that has been revealed by the activity test on Ni/Al2O3 catalyst. The result shows that none of those can’t make an exact determination of empirical equilibrium compositions, but there was a relatively good agreement between the Lagrange method and the empirical equilibrium. No significant difference has been observed between these methods and empirical conditions at high temperature.
Regular Article
Modeling and Simulation
M. Hosseini; A. H. Oudi; Y. Davoodbeygi
Abstract
The fully mixed continuous stirred tank reactor is an important type of industrial reactors mainly used to produce high volume products such as petrochemicals, detergents, sanitary products and products that are in demand in the market. Knowing the dynamic behavior of chemical reactors is of great importance ...
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The fully mixed continuous stirred tank reactor is an important type of industrial reactors mainly used to produce high volume products such as petrochemicals, detergents, sanitary products and products that are in demand in the market. Knowing the dynamic behavior of chemical reactors is of great importance in setting up, designing, controlling and stopping reactors. In this paper, the effect of non-dimensional numbers Damkohler and Stanton on the stability of a continuous stirred tank reactor in which a first-order exothermic reaction takes place is investigated. First, a mathematical model of the system's dynamic behavior was presented. Then, by simultaneous solving of the equations of mass and energy around the fixed point in MATLAB software, the effect of the mentioned numbers was investigated. The results show that the continuous stirred tank reactor shows different behaviors in different ranges of Damkohler and Stanton numbers. This reactor behaves unstable in small and large ranges of Damkohler and Stanton numbers due to the presence of mixed or positive and negative eigenvalues. The best range for Damkohler and Stanton numbers is close to 1, because in this range the reactor shows stable behavior due to having two negative eigenvalues. In this range, in addition to the stability, the conversion is also 100%. Finaly the ratio of Stanton to DamKohler was investigated as St / Da˃1 and St / Da = 1. If St / Da = 1, the system is in steady state, but in St / Da˃1, the system moves away from steady state.
Regular Article
Polymer Engineering and Technology,
S. Ghazanchaie; F. Derakhshanfard; L. Amirkhani
Abstract
The synthesized polystyrene has weaknesses in terms of mechanical, physical and thermal properties which limit the use of this polymer. Therefore, the use of the mixtures of polymers can improve these properties. Different parameters like the mixing speed can affect the quality of the properties of the ...
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The synthesized polystyrene has weaknesses in terms of mechanical, physical and thermal properties which limit the use of this polymer. Therefore, the use of the mixtures of polymers can improve these properties. Different parameters like the mixing speed can affect the quality of the properties of the polymer being prepared from the mixture of several polymers. In this study, different percentages of nanocomposites in different stirring speeds have been added to polystyrene. Different tests have been performed on the prepared polymer and investigating the tests shows that in different stirring speeds the values of the tensile strength and impact resistance of the prepared polymer can be increased while the values of the Vicat Softening Temperature (vicat) and Melt Flow Index (MFI) test numbers remain constant. The obtained results from the laboratory data have been simulated by Artificial Neural Networks (ANNs) in order to predict the results for the points which have not been tested and the simulated results show that the laboratory data covered the simulated data perfectly. The results of tests show that by increasing nanoparticles, the resistance of the polymer against impacts will be increased and in addition, increasing the rate of the stirrer causes all other values of tests to increase.
Short Paper
Polymer Engineering and Technology,
F. Ader; E. Sharifzadeh
Abstract
In this study, the main purpose has been to investigate the behavior of the nanoparticles with different structures and similar based materials in polymer nanocomposites. To this end, different samples, containing PS as the matrix, and layered graphene oxide (GO) and/or hollow graphene oxide nanoparticles ...
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In this study, the main purpose has been to investigate the behavior of the nanoparticles with different structures and similar based materials in polymer nanocomposites. To this end, different samples, containing PS as the matrix, and layered graphene oxide (GO) and/or hollow graphene oxide nanoparticles (HGO), were prepared via the melt mixing process and were subjected to heat conduction and tensile tests. To evaluate all features of the interaction between the polymer phase and the nanoparticles, a thermal/mechanical analytical model was proposed and the results were used to simulate the behavior of specific geometrical structures, corresponding to the real samples, under different thermal/mechanical conditions. The results showed good agreement between the obtained experimental data and simulation/analytical model interpretations. In addition, it was found that the HGO nanoparticle had such a good performance in enhancing the thermal and mechanical properties of the nanocomposite, due to its unique structure.