Regular Article
Energy
Z. Rahimi-Ahar; M. Sadegh Hatamipour
Abstract
Humidification-dehumidification (HD) desalination has been identified as a sustainable, reliable, and energy-efficient technology for producing freshwater on a small scale. VP-HD systems operated at one-stage, multi-stage, and multi-feeding vacuum humidification-over atmospheric pressure dehumidification ...
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Humidification-dehumidification (HD) desalination has been identified as a sustainable, reliable, and energy-efficient technology for producing freshwater on a small scale. VP-HD systems operated at one-stage, multi-stage, and multi-feeding vacuum humidification-over atmospheric pressure dehumidification arrangements can be the recent modifications of an HD system. The present study offers a theoretical investigation and experimental verification of two VP-HD systems, encompassing both sub-atmospheric pressure humidification and over-atmospheric dehumidification. Two designs are evaluated, one comprising a three-stage humidification setup and the other featuring a three-feeding one-stage humidification apparatus. The results show which design has better performance than previous conventional and variable pressure HD systems. The parametric analysis reveals that an upsurge in freshwater generation is observed with an increase in air temperature, feed salinity, and a decrease in humidifier pressure. Additionally, an optimal water-to-air ratio is identified. The study further highlights that multi-stage humidification yields better results concerning freshwater productivity and specific power consumption. Three-stage humidification is found to be the most efficient in terms of freshwater production and specific power consumption, achieving the highest values of 1.93 L h-1 m-2 and 0.21 kWh L-1, respectively. The agreement between theoretical and experimental outcomes is deemed satisfactory.
Regular Article
Modeling and Simulation
ehsan salehi; Golara Nikravesh; Masoud Mandooie
Abstract
Metal-organic frameworks have emerged as extended-network, tunable, crystalline hydrogen storage adsorbents. The uptake of H2 on Zn4O-based MOFs with different linkers was studied in the current work. The binding energies, consecutive binding energy and step energy of H2-adsorption on MOF-177, MOF-200 ...
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Metal-organic frameworks have emerged as extended-network, tunable, crystalline hydrogen storage adsorbents. The uptake of H2 on Zn4O-based MOFs with different linkers was studied in the current work. The binding energies, consecutive binding energy and step energy of H2-adsorption on MOF-177, MOF-200 and a newly defined MOF (NEW-MOF) have been calculated on different possible sorption sites, using DFT/Dmol3/PBE. The linkers have the same benzene ring in center, but different numbers of phenyl rings, including 3, 6 and 9 phenyl rings in MOF-177, MOF-200 and NEW-MOF around the center ring, respectively. Our study results showed that the binding energy of the H2 molecules with the linker NEW-MOF was -4.165 kcal/mol, more negative than those obtained for MOF-177 (-3.276 kcal/mol) and MOF-200 (-3.438 kcal/mol). The obtained thermo-favorability may be attributed to the less steric hindrance for adsorption of H2 on the MOF with the larger linker. Step energy results showed that the linkers of MOF-177, MOF-200 and NEW-MOF could adsorb 7, 9 and 12 number of H2 molecules, respectively. Results also disclosed adsorbed moles of H2 per 1×1×1 unit cell of the MOFs decreases with increasing the linker length according to the order of 0.263 (for MOF-177), 0.16 (for MOF-200) and 0.137 (for NEW-MOF), mainly due to reduced packing density of the active sites in the MOFs with larger linkers. The most negative binding energy was also tabulated for the perpendicular approaching of H2 molecules to the node of the central phenyl ring with the bonding distance of 3.19 Å from the linker.
Regular Article
Reaction Engineering, Kinetics and Catalysts,
Abdullah Irankhah; Sepideh Ghafoori; atieh ranjbar
Abstract
In the present work, the effect of synthesis method (simultaneous impregnation and coprecipitation) and copper to nickel active phases loading were investigated in Ni-Cu-Al catalysts. The water/ethanol molar ratio of 6 and gas hourly space velocity (GHSV) of 20000 hr-1 were used in all the experiments. ...
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In the present work, the effect of synthesis method (simultaneous impregnation and coprecipitation) and copper to nickel active phases loading were investigated in Ni-Cu-Al catalysts. The water/ethanol molar ratio of 6 and gas hourly space velocity (GHSV) of 20000 hr-1 were used in all the experiments. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques. The catalytic activity results revealed that 13Ni-6Cu/γ-Al2O3 impregnated catalyst was more active than co-precipitated one (13NiO-6CuO-81Al2O3) in the same amount of compositions of active metals and Al2O3, but by increasing the active phases (Cu and Ni) loading in co-precipitated catalysts (24NiO-31CuO-45Al2O3, 31NiO-24CuO-45Al2O3, 40NiO-15CuO-45 Al2O3 and 47NiO-8CuO-45Al2O3), they achieved a better performance than 13NiO-6CuO-81Al2O3 catalyst. The 40NiO-15CuO-45Al2O3 catalyst showed 99% ethanol conversion, as well as 303 hydrogen yield and 4% CO selectivity at 470oC. SEM images revealed agglomerated particles for the samples with high Al2O3 content and with increasing the active phase content in the catalyst the particle sizes decreased. The 40NiO-15CuO-45Al2O3 showed smallest particle size among the catalysts.
Regular Article
Environmental Engineering,
Azadeh Hemmati; Hayede Nafasi; Fatemeh aghamohammadi; Ali Afrous
Abstract
Constructed wetlands have been increasingly used as an effective method for removing heavy metals from wastewater. This study aimed to investigate the combined effect of sawdust and Hydraulic Retention Time (HRT) on the performance of vertical-flow constructed wetlands cultivated with Phragmites Australis ...
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Constructed wetlands have been increasingly used as an effective method for removing heavy metals from wastewater. This study aimed to investigate the combined effect of sawdust and Hydraulic Retention Time (HRT) on the performance of vertical-flow constructed wetlands cultivated with Phragmites Australis to remove Pb and Co from oily wastewater. To this end, nine barrels were used to construct the wetlands, which were filled with coarse gravel, polluted soil, and varying percentages of sawdust (0%, 20%, and 40%). Phragmites Australis cuttings were then cultured inside the barrels and irrigated with heavy metal-contaminated oily wastewater for three different hydraulic retention times (5, 10, and 15 days). After the vegetation period, plant, soil, and wastewater samples were collected and analyzed for Co and Pb concentrations, from which transfer factor (TF), bioconcentration factor (BCF), and removal efficiency (%) were derived. Results showed that while both Pb and Co removal efficiencies were affected by HRT and sawdust, the removal efficiency of Pb (36.66%) was higher than that of Co (30.83%). TF<1 and was not affected by HRT and sawdust, but the effect of HRT and sawdust on increasing BCF was significant. However, Phragmites Australis demonstrated suboptimal performance in the uptake and transfer of metals from root to stem.
Regular Article
Modeling and Simulation
Yaser Kazemi; Abdullah Irankhah
Abstract
Most of the reactions that occur in microreactors take place on the surface, so it is important to keep the reactants close to the reactive wall. One effective technique in this field is single-phase hydrodynamic focusing. However, this method has a drawback: a high percentage of reactants penetrate ...
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Most of the reactions that occur in microreactors take place on the surface, so it is important to keep the reactants close to the reactive wall. One effective technique in this field is single-phase hydrodynamic focusing. However, this method has a drawback: a high percentage of reactants penetrate into the sheath fluid. To address this issue, the concept of two-phase hydrodynamic focusing is introduced in this study. The main idea is to use a highly viscous sheath fluid to create a barrier against reactant penetration into the sheath flow. To demonstrate the effectiveness of this method, a 3D numerical simulation was performed with an irreversible second-order reaction. The results show that two-phase hydrodynamic focusing increases reaction rates, particularly in downstream regions where the Sherwood number can increase by several orders of magnitude with the use of a highly viscous sheath of liquid. Additionally, it was observed that the use of two-phase hydrodynamic focusing improves efficiency, which is defined as the ratio of solute in the sample flow to the total solute in each cross-section.
Regular Article
Thermodynamics,
Gabriela Lisa; Iuliana Bîrgăuanu; Catalin Lisa; Alexandra Bargan; Silvia Curteanu
Abstract
This paper evaluates the following properties: surface tension and refractive index in an area of composition influenced by component miscibility, four temperatures: 293.15, 303.15, 313.15 and 323.15 K and atmospheric pressure (0.1 MPa), for binary and ternary systems of benzyl alcohol, n-hexanol and ...
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This paper evaluates the following properties: surface tension and refractive index in an area of composition influenced by component miscibility, four temperatures: 293.15, 303.15, 313.15 and 323.15 K and atmospheric pressure (0.1 MPa), for binary and ternary systems of benzyl alcohol, n-hexanol and water, less studied in the literature. There was an increase in surface tension with increasing temperature for the n-hexanol-water binary system and the ternary system. Given that the refractive index is determined much easier and with a lower consumption of substances than the surface tension, in this paper the statistical processing of experimental data with multiple linear regression method (MLR) was applied and the following model was obtained: exc= 478.5+101.514⸱X1+58.389⸱X2+ 47.083⸱(T/273.15)-416.897⸱n. It correlates the excess surface tension (exc) with the composition (X1 and X2), the normalized temperature and the refractive index (n). Modelling with neural networks was also performed. The multilayer perceptrons (MLP) neuronal model (4:20:12:1) performs better than the MLR model, but the advantage of the latter is that it provides a mathematical expression that can be easily used by chemical engineers to predict excess surface tension based on experimental measurements of refractive index.