1. Interior Modification of Nano-Porous Fillers to Fabricate High Performance Mixed Matrix Membranes

H. Sanaeepur; A. Ebadi Amooghin; A. Kargari; Mohammadreza Omidkhah; A. Fauzi Ismail; S. Ramakrishna

Volume 16, Issue 2 , Spring 2019, , Pages 70-94

Abstract

  A new method is developed to enhance the gas separation properties of mixed matrix membranes (MMMs) by interior modification of an inorganic nano-porous particle. Ship-in-a-bottle (SIB), ...  Read More A new method is developed to enhance the gas separation properties of mixed matrix membranes (MMMs) by interior modification of an inorganic nano-porous particle. Ship-in-a-bottle (SIB), as a novel synthesis strategy, is considered to encapsulate a polyaza macrocyclic Ag-ligand complex into the zeolite Y, which is resulted in a new host-guest nano-composite. It is consequently incorporated into a glassy polymer matrix to fabricate a novel MMM for CO2 separation. Accordingly, cellulose acetate (CA) with relatively low gas permeability is selected as the membrane polymeric matrix to provide an appropriate opportunity for better tracking the effect of incorporating the new synthesized nano-porous hybrids. The results showed a promising increase in both the CO2 permeability (45.71%) and CO2/N2 selectivity (40.28%) of the prepared MMM over its pristine CA membrane. It can be concluded that the proposed method makes it possible to fabricate novel MMMs with significant intensification in performance of the current MMMs.

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2. Biofouling Behavior on Forward Osmosis Using Vertically Aligned CNT Membrane on Alumina

M.R Omidkhah; H. Azami; L. Ghaheri

Volume 16, Issue 2 , Spring 2019, , Pages 1-13

Abstract

  Nowadays, forward osmosis (FO) with many advantages in water treatment, are so attractive for researchers and investigators that the studies are going to optimize and increase its efficiency. ...  Read More Nowadays, forward osmosis (FO) with many advantages in water treatment, are so attractive for researchers and investigators that the studies are going to optimize and increase its efficiency. However one of the most controversial operating malfunctions of FO process is fouling that limits the FO global application. In the following research, vertically aligned carbon nanotube (VACNT) on alumina membrane is introduced with high water permeability and less biofouling potential in forward osmosis for seawater osmotically dilution systems. VACNT membranes were prepared via pyrolysis of polymer into the pores of alumina. The effect of the temperature of pyrolysis process on CNT’s structure are assessed which indicated crystallinity of the CNTs increase in higher pyrolysis temperature of 800 °C. A small scale setup is designed for FO analysis and measurements of biofouling, flux and the effect of osmotic pressure were measured. Furthermore, all analysis were compared with commercial TFC membrane and results demonstrated that VACNT membrane has 40% less biofouling potential and 2 times better flux results.

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3. Comparison the performance of different reverse osmosis membrane modules by CFD modeling

M. Bahoosh; E. Kashi; S. Shokrollahzadeh; Kh. Rostami

Volume 16, Issue 1 , Winter 2019, , Pages 101-116

Abstract

  Reverse osmosis is a commonly used process in water desalination. Due to the scarcity of freshwater resources and wastewater problems, a lot of theory and experimental studies have ...  Read More Reverse osmosis is a commonly used process in water desalination. Due to the scarcity of freshwater resources and wastewater problems, a lot of theory and experimental studies have been conducted to optimize this process. In the present study, the performance of reverse osmosis membrane module of salt–water separation was simulated based on computational fluid dynamics technique and solution-diffusion theory. Eight geometries of membrane modules four flat sheets, and four tubular membranes were investigated. It was found that if the membrane surface area and inlet flow rate were kept constant for the eight modules, the pressure drop and permeated flow rate would be approximately similar for some geometries (such as the performance of primary flat sheet channel is same as 3 tubular membranes with R=1/3 Rref). The results also showed that because of the phenomenon of concentration polarization, if it is possible to use more membranes with a smaller length, it can reduce the pressure drop and increase the permeation flux of water. Furthermore, the results showed that in similar conditions between the tubular and the plate membranes; the tubular one is more suitable for the water permeation due to its ease of construction and its ability to withstand ECP.

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4. Removal of Pb (II) From Wastewater Using Henna; Optimization of Operational Conditions

M. Shafiee; A. Akbari; B. Ghiassimehr

Volume 15, Issue 4 , Autumn 2018, , Pages 17-26

Abstract

  At this work, removal of Pb (II) using Lawsonia inermis (Henna) was studied. In recent years, use of low price adsorbent is taken into consideration. Adsorption experiments were performed ...  Read More At this work, removal of Pb (II) using Lawsonia inermis (Henna) was studied. In recent years, use of low price adsorbent is taken into consideration. Adsorption experiments were performed in batch system at ambient temperature (25℃). The influence of some parameters such as time, initial metal concentration, pH and adsorbent dose were investigated. The optimum conditions was obtained at pH of 6, 10 ppm of initial metal concentration, 80 min of contact time and 0.75 g/L of adsorbent dose. To study the adsorbent morphology, Scanning Electron Microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) was used before and after adsorption of Pb (II) ions. Sorption of Pb (II) was evaluated by Freundlich and Langmuir isotherms. The results indicate that the Freundlich isotherm model is better described the adsorption of Pb (II) than Langmuir isotherm model. Also, it is observed that, the pseudo-second-order kinetic model well fitted to experimental data .

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5. Design and Fabrication of an Improved Single-Column Chromatographic Separation Process

B. Medi; M.-K. Kazi

Volume 15, Issue 4 , Autumn 2018, , Pages 81-92

Abstract

  In this work, an improved single-column chromatographic (ISCC) separation process is proposed. The term `improved' refers to both conceptual and physical modifications compared to the ...  Read More In this work, an improved single-column chromatographic (ISCC) separation process is proposed. The term `improved' refers to both conceptual and physical modifications compared to the available single-column processes, including a novel fraction collection scheme and allowing overlapped peaks from adjacent cycles. Also the fraction collection mechanism was modified in order to facilitate online monitoring. Another advantage of the ISCC process is its large degree of freedom as injection volume, cycle time, solvent flow rate, feed concentration, and fraction-collection intervals can all be decision variables in this process. The experimental implementation and validation is covered in this work. The results indicate successful operation of the ISCC process and accompanying peripherals for the separation of guaifenesin enantiomers. In particular, the tests confirmed the integrity of the online monitoring system and proved the capability of the process for 98% purification of the tested enantiomers with an advantageously shorter cycle time, which results in higher productivity.

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6. Optimization of solvothermally synthesized ZIF-67 metal organic framework and its application for Cr(VI) adsorption from aqueous solution

N. Mostafazadeh; A.A. Ghoreyshi; K. Pirzadeh

Volume 15, Issue 4 , Autumn 2018, , Pages 27-47

Abstract

  In this study, ZIF-67 was synthesized through solvothermal method to remove Cr(VI) ions from aqueous solution. To improve the structural properties of ZIF-67 and its adsorption capacity, ...  Read More In this study, ZIF-67 was synthesized through solvothermal method to remove Cr(VI) ions from aqueous solution. To improve the structural properties of ZIF-67 and its adsorption capacity, optimization of the synthesis conditions was carried out based on maximum Cr(VI) uptake. From experiments, the optimum condition was revealed as solvent: metal ion molar ratio of 4.6:1, ligand: metal ion molar ratio of 318:1 and temperature of 23℃. The physio-chemical properties of as-synthesized ZIF-67 were investigated by BET, XRD, FTIR and FESEM analyses. Effect of adsorption pH, adsorbent dosage, initial concentration and contact time on adsorption process was investigated. Based on the results, the maximum adsorption capacity of Cr(VI) was 26.27 mg/g which was obtained at 35℃, pH= 5, adsorbent dosage of 3 g/l and initial concentration of 107.82 mg/l. The equilibrium time for Cr(VI) adsorption varied from 180 min for low initial concentration of 9 mg/L to 240 min for a high initial concentration of 90 mg/L. For the synthesized ZIF-67, maximum uptake capacity was reported 26.27 mg/g at initial concentration of 107.82 mg/l. The equilibrium data were described better by Langmuir-Freundlich isotherm model than the other models at three different temperatures. Pseudo-second-order model fitted the experimental data better than pseudo-first-order one. Adsorption thermodynamics indicated that the adsorption process was endothermic and spontaneous in nature. The regenerability of ZIF-67 was also studied in three sequential cycles and the Cr(VI) adsorption was almost retained after two cycles.

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7. Propionic acid extraction in a microfluidic system: simultaneous effects of channel diameter and fluid flow rate on the flow regime and mass transfer

F. Hosseini; M. Rahimi; O. jafari

Volume 15, Issue 4 , Autumn 2018, , Pages 48-62

Abstract

  In this work, extraction of propionic acid from the aqueous phase to the organic phase (1-octanol) was performed in T-junction microchannels and effects of channel diameter and fluid ...  Read More In this work, extraction of propionic acid from the aqueous phase to the organic phase (1-octanol) was performed in T-junction microchannels and effects of channel diameter and fluid flow rate on the mass transfer characteristics were investigated. The two-phase flow patterns in studied microchannels with 0.4 and 0.8 mm diameters were observed. Weber ‎ number and surface-to-volume ratio were calculated for evaluating flow patterns. Moreover, the effect of volumetric flow rates on the extraction ‎efficiency, volumetric mass transfer coefficient, and pressure drop was examined. Results showed that the pressure drop in the microchannel with 0.4 mm diameter is 2-2.7 times higher than that in the microchannel with 0.8 mm diameter. In both microchannels, with increase in flow rate, the extraction ‎efficiency first increases and then decreases. In addition, at high flow rates (2.4, 4.5 and 6 mL/min), the extraction ‎efficiency in the microchannel with 0.8 mm diameter increased up to the range of 7-14.9 % compared with that in the microchannel with 0.4 mm diameter.

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8. Evaluation of Cr (VI) ion removal from aqueous solution by bio-inspired chitosan-clay composite: Kinetics and isotherms

Sh. Biswas; Md. M. Islam; M. M. Hasan; S.H. Rimu; M. N. Khan; P. Haque; M. M. Rahman

Volume 15, Issue 4 , Autumn 2018, , Pages 63-80

Abstract

  This paper reports the evaluation of adsorbing Cr (VI) ions on sorbent prepared from chitosan (CHT), a versatile derivative of chitin, and dodecyl amine modified locally available kaolinite ...  Read More This paper reports the evaluation of adsorbing Cr (VI) ions on sorbent prepared from chitosan (CHT), a versatile derivative of chitin, and dodecyl amine modified locally available kaolinite clay (Bijoypur clay) (MC) that has excellent mechanical properties and great resistance to chemical and biological attack. The effect of the initial metal ion concentration, solution pH, contact time, and adsorbent dosages on the adsorption capacity of the composites was investigated. pH 4 is selected for better adsorption by the adsorbents. The adsorption abilities were studied over Cr (VI) ions using different adsorption isotherm such as Langmuir, Freundlich, and Dubinin-Radushkevich respectively. Langmuir isotherm is found better fitted with maximum adsorption capacity of 73 mg/g by composite SB-1. R2 obtained from Langmuir isotherm is 0.999 which indicates a monolayer adsorption on the adsorbent surface. The adsorption kinetics was also well described by the pseudo-second-order equation with a rate constant of 0.000302 g mg−1 min−1 at 25 ppm Cr(VI) concentration. The adsorption of Cr (VI) ions by the adsorbent were confirmed by FT-IR and X-RD analysis of the composites before and after Cr (VI) ion adsorption. The desorption percentage of the metal ion and the second cycle metal adsorption by regenerated (regenerated after the first adsorption by fresh adsorbent) adsorbent processed with 0.01N sulphuric acid shows a value of 78.23% and 68.12% respectively.

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9. Microfluidic extraction of tannic acid from Quercus leaves

M. Yasemi; M. Rahimi; A. Heydarinasab; M. Ardjmand

Volume 15, Issue 3 , Summer 2018, , Pages 15-33

Abstract

  In this study, extraction of tannic acid using microchannel was investigated. Affective parameters were optimized. Different solvents including buthanol, ethylacetate and n-hexane as ...  Read More In this study, extraction of tannic acid using microchannel was investigated. Affective parameters were optimized. Different solvents including buthanol, ethylacetate and n-hexane as organic phase, methanol, propanol, ethanol and water as aqueous phase investigated. Microchannels with different confluence angles and diameters were examined. Microchannels with different confluence angles and diameters were examined. The effects of pH, temperature, and volumetric flow ratio and contact time of the two phases were investigated. The response surface methodology was used to optimize extraction yield of tannin from Quercus leaves in the employed microchannels. Based on this optimization, maximum yield was achieved at pH=2, temperature=33.1℃, volumetric flow ratio =1.2 and contact time of 25.35s. Results show that extraction-using microchannel has many advantages over traditional methods, including shorter time and higher economic efficiency. Moreover, microchannel provides smaller volume of fluids resulting in lower solvent consumption, lower waste production, shorter analytical times, smaller space requirements, and lower energy consumption.

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10. Fabrication of Chitosan-Polyethylene Oxide Electrospun Nanofibrous Mats Containing Green Tea Extract

A. Barzegari; Z. Shariatinia

Volume 15, Issue 2 , Spring 2018, , Pages 65-77

Abstract

  Novel electrospun nanofibrous CS-PEO nerve conduits containing 0, 2.5 and 5% of green tea methanolic extract were developed and characterized by FE-SEM, FT-IR, TGA/DSC as well as tensile ...  Read More Novel electrospun nanofibrous CS-PEO nerve conduits containing 0, 2.5 and 5% of green tea methanolic extract were developed and characterized by FE-SEM, FT-IR, TGA/DSC as well as tensile strength analysis. The FE-SEM images revealed that all of the nanofibers had an average diameter of ∼80nm. The swelling degree was decreased by increasing the GT amount from 2.5 to 5% and this might be attributed to the enhanced interactions of the NH2, C(O)NH2 and OH groups of chitosan and PEO polymers with the OH groups of GT leading to a less hydrophilic mat surface, thus reducing the attraction by the aqueous medium. Moreover, the swelling was the highest in acidic medium but it was decreased in the neutral environment and it had the least value within the alkaline medium. The CS-PEO-5%GT exhibited the highest antibacterial activity among three samples examined against both S. aureus and E. coli microorganisms. The CS-PEO-5%GT was proved to be a very suitable candidate to be used as nerve conduit due to its improved tensile and antibacterial activities.

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11. Extraction of pectin from sour orange and its application as the adsorbent for removal of nickel from aqueous solution: Kinetic and equilibrium study

N. Kakoui; M. Nikzad; A. A. Ghoreyshi; M. mohammadi

Volume 15, Issue 2 , Spring 2018, , Pages 3-21

Abstract

  The present study investigates the potential applicability of the extracted pectin from sour orange pomace as adsorbent for Ni (II) removal from aqueous solution. Pectin extraction ...  Read More The present study investigates the potential applicability of the extracted pectin from sour orange pomace as adsorbent for Ni (II) removal from aqueous solution. Pectin extraction from the pomace was carried out using HCl and the highest pectin extraction yield of 26.75% was obtained. The Fourier transform infrared (FTIR) spectroscopy analysis confirmed that the structure of the extracted pectin was similar to the commercial one. The morphology and chemical characteristics of pectin beads were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX) techniques. The influence of several parameters including pH, initial metal concentration, adsorption temperature and time was studied to optimize nickel removal. The maximum Ni (II) removal of 85.1% was obtained at initial concentration of 20 mg/L and the highest adsorption capacity of 19.76 mg/g was achieved at nickel concentration of 100 mg/L. Kinetic and equilibrium studies were done to evaluate Ni (II) sorption from aqueous solution by the synthesized beads. Results showed that the sorption process follows a pseudo- second- order kinetic model. The equilibrium data were well correlated with Langmuir and Redlich-Peterson models by high regression coefficients.

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12. Design and construction of a helium purification system using cryogenic adsorption process

A. Saberimoghaddam; V. Khebri

Volume 15, Issue 1 , Winter 2018, , Pages 89-101

Abstract

  One of the most appropriate methods for elimination of trace impurities in helium is cryogenic adsorption process. So, in this study design and construction of cryogenic adsorption ...  Read More One of the most appropriate methods for elimination of trace impurities in helium is cryogenic adsorption process. So, in this study design and construction of cryogenic adsorption helium purification system (3 Nm3.hr-1, 80 bar) carried out using activated carbon as adsorbent at 77K. To evaluation of adsorption dynamics and effect of pressure on elimination of trace impurities, helium purification was performed from 10 to 70 bar. Results showed that helium can be purified from 99.95 % to 99.99999% at pressure of 60 bar using cryogenic adsorption process. Effect of regeneration condition on helium purity and recovery was investigated by three different regeneration methods: regeneration by helium at 40 °C and at 180 °C as purge gas, countercurrent to feed direction, and regeneration via vacuum. Results showed that regeneration of bed by vacuum can be proposed as most appropriated method because of maximum helium purity and high recovery of helium (98%).

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13. Assessment of effective factors on bacterial oxidation of ferrous iron by focusing on sweetening natural gas

A. Zabihollahpoor; P. Hejazi

Volume 15, Issue 1 , Winter 2018, , Pages 18-34

Abstract

  In this study, the effects of some factors on bacterial growth and ferrous oxidation rates were investigated by Acidithiobacillus ferrooxidan in 250 ml shake flasks. One factor at a ...  Read More In this study, the effects of some factors on bacterial growth and ferrous oxidation rates were investigated by Acidithiobacillus ferrooxidan in 250 ml shake flasks. One factor at a time (OFAT) design approach was used for preliminary evaluation of various factors affecting the process, such as pH, initial ferrous and elemental sulfur concentrations, shaker agitation rate, and liquid to flask volume ratio. After that, optimal levels of effective last three factors to achieve high oxidation rate and cell growth rate were investigated using a full factorial design. It was obtained that agitation rate and liquid to flask volume, as well as their binary interaction, are significant factors on ferrous iron bio-oxidation rate. In contrast, initial high ferrous iron concentration was the only effective factor on the cell growth rate. Maximum bio-oxidation rate of 0.417 g/L was achieved at the media with Fe2+ ion concentration of 30 g/l, agitation rate of 200 rpm, and liquid to flask volume ratio of 20% by full factorial optimization, which is an about 40% increase compared to the result obtained in OFAT method. Then, the effect of step-wise adaptation of A. ferrooxidans to in high Fe2+ concentration was studied, and about 40% reduction in bacterial lag phase time, and 36 and 86% increase in bacterial growth rate and bio-oxidation rate were acquired, respectively.

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14. DESULFURIZATION AND DEMETALIZATION OF USED ENGINE OIL IN LABORATORY SCALE

N.A. Kostic; M.M. Milosavljevic; L.S. Pecic; S.Z. Babic; B.L. Milosavljevic; D.L. Milosevic; S.S. Krstic; B.V. Krstić

Volume 15, Issue 1 , Winter 2018, , Pages 73-88

Abstract

  This paper describes a laboratory method for treatment of used engine oil FENIX SUPERIOR SAE 15W-40 with intention to decrease of sulfur and selected metal content at acceptable level. ...  Read More This paper describes a laboratory method for treatment of used engine oil FENIX SUPERIOR SAE 15W-40 with intention to decrease of sulfur and selected metal content at acceptable level. FENIX SUPERIOR SAE 15W-40, produced by manufacturer Joint Stock Company FAM Krusevac, is used for lubrication of the most modern four-stroke diesel and gas engines of passenger and commercial vehicles, engine construction, mining and agricultural machinery, as well as stationary power aggregates including highly overloaded engines working in harsh environmental conditions. Exhausted oil samples was obtained from the three sources: diesel and gas engines of passenger cars and agricultural machines – tractors were treated according to novel two step technology. In first step physical operations such as centrifugation, filtration and separation was applied in order to remove mechanical impurities (sludge), condensed material and water. In the second step chemical oxidation, using three agents: hydrogen peroxide, sodium hypochlorite, and potassium persulfate was applied to achieve removal of the sulfur containing compounds. Based on obtained results at laboratory level, a technology at semi-industrial level for the treatment of waste oil was proposed. New ecologically friendly technology developed for treatment of waste oil offer appropriate advantages in comparison to commercially available technologies.

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15. Application of Turbo-Expander for Greenhouse Gas and Air Pollutant Emissions Reduction Using Exergy and Economical Analysis

E. GhasemiKafrudi; M. Amini; M. R. Habibi

Volume 14, Issue 4 , Autumn 2017, , Pages 32-47

Abstract

  The effects of greenhouse gases (GHG) on the growth of global warming, and increase of GHG and air pollutant emissions for energy production have forced the need of energy recovery ...  Read More The effects of greenhouse gases (GHG) on the growth of global warming, and increase of GHG and air pollutant emissions for energy production have forced the need of energy recovery which is normally wasted in industrial plant. The present research work focused on the GHG and air pollutant emissions reduction employing pressure waste energy recovery. Pressure break-down via Joule-Thomson valve is a neat potential for waste energy recovery in gas refineries, which may also be provide by using a turbo-expander instead of commercial valves. Based on this ground, an exergy analysis is carried out for Joule-Thomson valve. The results showed that the exergy loss is higher than 6.5 MW and it is possible to recover about 1.9 MW of exergy loss. On the other hand, it was found that about 16900MWh of electrical energy can be produced by recovering the energy of waste pressure, which may leads to less consumption of the load and gas in refinery power unit. Consequently, equal the gas consumption reduction, 12056 ton CO2e of GHG and 54.6 ton of air pollutant emissions is reduced annually. Economical evaluation of utilizing a turbo-expander instead of a valve proved that this altering scenario is deducible and practical. Economical indexes, namely, IRR and NPV are found to be equal to 25.51% and 929571 US$, respectively. Moreover, sensitivity analysis conducted on each specific state certified the obtained results.

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16. Waste water ammonia stripping intensification using microfluidic system

Mo. H. Almasvandi; M. Rahimi

Volume 14, Issue 4 , Autumn 2017, , Pages 17-31

Abstract

  This paper reports the results of experimentally removing ammonia from synthetically prepared ammonia solution using a micro scale mixing loop air stripper. Effects of various operational ...  Read More This paper reports the results of experimentally removing ammonia from synthetically prepared ammonia solution using a micro scale mixing loop air stripper. Effects of various operational parameters (such as: pH, air flow rate, wastewater flow rate and initial ammonia concentration) were evaluated. By increasing the pH from 10 to 12.25 the amount of KLa increased from 0.26 to 0.73 hr-1. A considerable enhancement, about 150%, can be found for KLa by changing the air flow rate from 280 to 700 mL/min under fixed condition. The wastewater flow rate can also the value of KLa from 0.22 to 0.59 hr-1. The values of KLa increased only about 20% by changing the initial concentration of ammonia in the range between 50 and 500 mg/L. The results showed that improving in air stripping using microchannel was successfully carried out with enhancing overall volumetric mass transfer coefficient (KLa) and providing higher mass transfer capabilities compared with other types of strippers, even for lower amounts of used air. The enhancement of mass transfer is happened by efficient mixing induced by the employed microchannel. It has been demonstrated that wastewater flow rate and air flow rate have significant effects on KLa. The optimal stripping conditions and mathematical modeling for ammonia removal and the relation between the parameters were determined using Response Surface Methodology (RSM) with Central Composite Design (CCD) method. The results demonstrate the advantages the proposed system over convention stripper types.

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17. Mathematical simulation of thermal behavior of moving bed reactors

L. Mahmoodi; B. Vaferi; M. Kayani

Volume 14, Issue 4 , Autumn 2017, , Pages 48-58

Abstract

  Temperature distribution is a key function for analyzing and optimizing the thermal behavior of various process equipments. Moving bed reactor (MBR) is one of the high-tech process ...  Read More Temperature distribution is a key function for analyzing and optimizing the thermal behavior of various process equipments. Moving bed reactor (MBR) is one of the high-tech process equipment which tries to improve the process performance and its energy consumption by fluidizing solid particles in a base fluid. In the present study, thermal behavior of MBR has been analyzed through mathematical simulation. Good agreement between the obtained results and both experimental data and analytical solution by self-adjoint method is observed. Mathematical results confirm that the average particle temperature linearly increases across the reactor length. Fluid temperature changes in a parabolic manner, and then it changes linearly. Increasing the Biot number ( ) results in increasing the temperature gradient inside the particle to a maximum value, and thereafter a decreasing pattern is observed. The numerical results confirmed that the finite difference method can be used for thermal analysis of the moving bed reactor.

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18. Stochastic Comparisons of Probability Distribution Functions with Experimental Data in a Liquid-Liquid Extraction Column for Determination of Drop Size Distributions

Sh. Houshyar; M. Torab-Mostaedi; S. M. A. Moosavian; Seyed Hamed Mousavi; M. Asadollahzadeh

Volume 14, Issue 3 , Summer 2017, , Pages 82-95

Abstract

  The droplet size distribution in the column is usually represented as the average volume to surface area, known as the Sauter mean drop diameter. It is a key variable in the extraction ...  Read More The droplet size distribution in the column is usually represented as the average volume to surface area, known as the Sauter mean drop diameter. It is a key variable in the extraction column design. A study of the drop size distribution and Sauter-mean drop diameter for a liquid-liquid extraction column has been presented for a range of operating conditions and three different liquid-liquid systems. The effects of rotor speed, and dispersed and continuous phase velocities on drop size are investigated. Drop size distribution are appropriately described using the normal and log-normal probability density functions. The mathematical approach is used to determine the constant parameters in these functions and to provide the fit of the experimental data with them. and empirical expressions are derived to predict the parameters of the distribution curve as a function of operating variables, and physical properties of the systems. Good agreement between the prediction and experiments was achieved for all investigated operating conditions. An empirical correlation is also proposed to predict the Sauter-mean drop diameter with mean deviation of 9.8%.

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19. Methanol crossover and selectivity of nafion/heteropolyacid/montmorillonite nanocomposite proton exchange membranes for DMFC applications

M. Azimi; S.J. Peighambardoust

Volume 14, Issue 3 , Summer 2017, , Pages 65-81

Abstract

  In this work, we prepared the nafion/montmorillonite/heteropolyacid nanocomposite membranes for direct methanol fuel cells (DMFCs). The analyses such as X-ray diffraction (XRD), Fourier ...  Read More In this work, we prepared the nafion/montmorillonite/heteropolyacid nanocomposite membranes for direct methanol fuel cells (DMFCs). The analyses such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) were conducted to characterize the filler dispersion and membrane structure in prepared nanocomposite membranes. XRD patterns of nafion-CsPW-MMT nanocomposites membranes showed the exfoliated structure of membranes by adding MMT and CsPW. SEM-EDXA results showed proper dispersion of nanoparticles in the membrane matrices. Addition of CsPW-MMT to nafion membranes increases water uptake and IEC due to increase hydrophilic groups in membranes. The proton conductivity results showed that proton conductivity increases by increasing amount of CsPW and decreasing of clay content in the membrane. Methanol crossover through polymer electrolyte membranes is a critical issue and causes an important reduction of performance in DMFCs. The developed intercalated nafion/CsPW/MMT nanocomposite membranes have successfully improved the membrane barrier properties due to the unique feature of MMT which contributed to the formation of a longer pathway towards methanol across the membrane. The lowest methanol crossover of the developed membranes in this study was 1.651×10-6 cm2 s-1 which was lower than re-cast nafion membrane (2.078×10-6 cm2 s-1). The methanol permeability was significantly reduced by the incorporation of MMT and increased by addition of CsPW in the nafion membrane. Finally, according to the selectivity results, the nafion-MMT-CsPW nanocomposite membrane with MMT mass fraction of 2.5% and CsPW mass fraction of 8% shows the best membrane selectivity and this nanocomposite membrane could be suitable for application in DMFCs.

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20. investigation of mercaptan removal from Kerosene using passive mixing tools: Experimental study and CFD modeling

A. Parvareh; . Parvizi

Volume 14, Issue 3 , Summer 2017, , Pages 55-64

Abstract

  Abstract In this work, the role of appropriate mixing for mercaptan removal from Kerosene using caustic soda has been investigated in the pilot scale. Static mixer at different condition ...  Read More Abstract In this work, the role of appropriate mixing for mercaptan removal from Kerosene using caustic soda has been investigated in the pilot scale. Static mixer at different condition has been used as a passive mixing tool to achieve proper mixing and consequently high performance of mercaptan removal. Two lengths of static mixer including 20 and 40 cm as well as two pitches 1 and 3 mm were considered in a straight line. NaOH was injected to the Kerosene line to remove ( convert it to disulfide) the mercaptan. The effect of mixer length, mixer element pitch at different flow rates of Kerosene, including 2, 18 and 30 mL/s was investigated on the mercaptan removal. The experimental results showed that the concentration of mercaptan in the pilot line outlet will decrease as the flow rates of Kerosene decreases. Also, at a fixed flow rate of Kerosene, increasing the length of the static mixer and decreasing its element pitch caused the mercaptan to decrease due to proper mixing. Computational Fluid Dynamics (CFD) modeling technique was employed to describe the experimental results, fluid flow pattern, and mixing performance. Qualitative predicted results of CFD modeling show a good agreement with the experimental data.

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21. Adsorption and Desorption Process of Chromium Ions Using Magnetic Iron Oxide Nanoparticles and Its Relevant Mechanism

M. Jadidi; N. Etesami; M. Nasr Esfahany

Volume 14, Issue 3 , Summer 2017, , Pages 31-40

Abstract

  In this study adsorption of Cr(VI) from aqueous solution by Fe3O4 nanoparticles was investigated. Desorption process and recovery of nanoparticles using different solutions were then ...  Read More In this study adsorption of Cr(VI) from aqueous solution by Fe3O4 nanoparticles was investigated. Desorption process and recovery of nanoparticles using different solutions were then carried out, and it was observed that NaOH (0.5M) can remove 90% of adsorbed chromium ions. Following the completion of adsorption/ desorption cycles, it was determined that nanoparticles have still had a high ability of chromium ions adsorption after 4 cycles. In addition, it was found that when iron oxide nanoparticles were washed with NaOH solution, the adsorption efficiency increases in the next cycle. FTIR spectra and zeta potential analysis, demonstrated the increased in surface positively charged of nanoparticles leads to increased electrostatic attraction forces between the iron oxide nanoparticles and chromium ions which finally resulted in adsorption increasing. So in this research, pretreatment of nanoparticles with NaOH solution modifies the surface of Fe3O4 nanoparticles by increasing surface positively charged mechanism and the adsorption efficiency has improved in the next cycle.

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22. Improvement of gas separation properties of polyurethane membrane using plasma grafting

P. Azadi; Sh. Hassanajili

Volume 14, Issue 3 , Summer 2017, , Pages 19-30

Abstract

  In recent years, plasma treatments have given good results since they offer high technological efficiency with low waste generation. One of the most important characteristics of plasma ...  Read More In recent years, plasma treatments have given good results since they offer high technological efficiency with low waste generation. One of the most important characteristics of plasma methods is their action only on a thin surface layer, whereas the bulk of sample remains unchanged and the modified material keeps its chemical and mechanical properties. In this research, polyurethane membrane surface was modified by low frequency plasma grafting with methacrylic acid and acrylamide monomers to alter solution-diffusion mechanism. We chose different parameters of plasma treatment and studied their effects toward maximum solubility, permeation and selectivity. The grafting on the surfaces was characterized by water contact angle measurement and atomic force microscopy. After confirming a successful grafting, we studied the effect of surface modification on permeation of CH4 and CO2. Significant increase in CO2 permeation and about 32 percent increase in CO2/CH4 selectivity was observed. Better results were obtained for low powers and acrylamide grafted surface.

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23. Fabrication and characterization of polycarbonate/titanium oxide nanotubes mixed matrix membranes for efficient removal of cadmium and copper from aqueous solution

M. Delavar; Gh. Bakeri; M. Hosseini

Volume 14, Issue 2 , 2017, , Pages 59-73

Abstract

  In this study, novel polycarbonate-titanium oxide nanotubes (PC-TNT) ultrafiltration mixed matrix membranes (MMMs) were fabricated for decontamination of Cd2+ and Cu2+ metal ions from ...  Read More In this study, novel polycarbonate-titanium oxide nanotubes (PC-TNT) ultrafiltration mixed matrix membranes (MMMs) were fabricated for decontamination of Cd2+ and Cu2+ metal ions from aqueous solution. The weight percent of TNTs in the polycarbonate membrane matrix was changed from 0 to 15. The synthesized neat PC membrane and PC-TNTs MMMs were characterized with respect to structural morphology and hydrophilicity using scanning electron microscopy (SEM) and water contact angle, respectively. The effects of TNTs loadings on the pure water flux, mean pore size, porosity and water contact angle of fabricated membranes and Cd2+ and Cu2+ heavy metal ion rejection were also studied. By increasing the loading of TNTs nanoparticles in the membrane matrix, the membrane mean pore size tended to increase, while the porosity decreased. Also, the increase in TNTs loading resulted in an increase in membrane water flux which was mainly attributable to the enhancement in mean pore size and partly caused by the decreased contact angle value (more hydrophilic). Of all the membranes studied, it was found by UF experiments that PC-TNT MMM was the most efficient material in heavy metal ions removal due to the superior adsorption capacity of TNTs material. The generic results revealed that TNTs material can be favorite candidates for MMMs preparation in order to be conveniently used in the Cd2+ and Cu2+ heavy metal ions decontamination from polluted water resources.

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24. Simulation, Control and Experimental Analysis of 1,3Butadiene Purification Unit

Rahbar Rahimi; Shirin Boulaqhi; Amir Ziarifar

Volume 13, Issue 4 , Autumn 2016, , Pages 33-45

Abstract

  Simulation of a process and analysis of its resulting data in both dynamic and steady-state conditions are fundamental steps in understanding the process in order to design and efficient ...  Read More Simulation of a process and analysis of its resulting data in both dynamic and steady-state conditions are fundamental steps in understanding the process in order to design and efficient control of system as well as implementing operational cost reduction scheme. In the present paper, steady and unsteady state simulation of Amir Kabir1, 3 butadiene purification units has been done by using Aspen and Aspen Dynamic software together with the Peng- Robinson equation of state to investigate the system responses to the disturbances. In the unsteady state simulation mode; the flow rates, pressure, temperature and level (FPTL) were controlled by Proportional-Integral-Derivative (PID) controllers in the unit. Finally, transient responses to changes such as feed temperature, feed flow rates, steam flow rates and the duties of the re-boiler of columns in unit were gained. For reaching to purified 1,3 butadiene, sensitivity of the process to the fluctuations of feed temperature and on the duties of the re-boilers of the columns is noticeable .

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25. Simultaneous high hydrogen content-synthesis gas production and in-situ CO2 removal via sorption-enhanced reaction process: modeling, sensitivity analysis and multi-objective optimization using NSGA-II algorithm

Malihe Heravi; Mahdi Bayat; Mohammad Reza Rahimpour

Volume 13, Issue 4 , Autumn 2016, , Pages 71-95

Abstract

  The main focus of this study is improvement of the steam-methane reforming (SMR) process by in-situ CO2 removal to produce high hydrogen content synthesis gas. Sorption-enhanced (SE) ...  Read More The main focus of this study is improvement of the steam-methane reforming (SMR) process by in-situ CO2 removal to produce high hydrogen content synthesis gas. Sorption-enhanced (SE) concept is applied to improve process performance. In the proposed structure, the solid phase CO2 adsorbents and pre-reformed gas stream are introduced to a gas-flowing solids-fixed bed reactor (GFSFBR). One dimensional mathematical model is developed to evaluate the effect of adsorbents on the efficiency of SMR at steady-state condition. To prove the accuracy of the considered model, simulation results are compared against available industrial plant data. Modeling results represent that application of SE method in SMR enhances syngas production and reduces CO2 content. The reported data indicate that by overcoming thermodynamic limitations and controlling coke formation, CH4 conversion and H2 yield improve about 23% and 29%, respectively. For more investigation, sensitivity analyses of some related parameters of the pre-reformed gas are performed to predict optimum conditions. Finally, the proposed GFSFBR for the SMR process leads to higher hydrogen production and H2/CO ratio. As the last part, non-dominated sorting genetic algorithm-II is applied to perform multi-objective optimization of the SE-SMR.

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