Title:
Investigation of Sour Natural Gas Decomposition in a Nozzle-type Solar Reactor for Hydrogen Production
Author(s):
M. Javadi , M. Moghiman , F. Faridnia
Paper language: English
Abstract:
Eventual realization of a hydrogen economy requires cheap and readily available hydrogen sources and a technology to convert them into pure hydrogen in an efficient and sustainable manner. The objective of this paper is the computational investigation of the hydrogen production through thermal decomposition of sour natural gases containing CH4 and H2S inside a solar reactor. In this study a solar reactor has been used to absorb solar power and allow it to concentrate in a graphite nozzle in the middle of the reactor and transfer it to a flow reactant thereafter. From an economical standpoint, the main issue is the production of two valuable products, hydrogen (H2) and a high-value nano-material of carbon. The effects of H2S to CH4 feed ratio and reactor temperature on hydrogen, carbon black, S2 and CS2 formation are investigated. The results show complex behavior in the products because of the difference in CH4 and H2S pyrolysis temperatures. It can be seen that for H2S/CH4>2, the yields of H2 and CS2 reach a local and global maximum at H2S/CH4=5, respectively. A comparison performed between the presented results and the results of Towler and Lynn, and Abanades demonstrates a good agreement.
Keywords:
Hydrogen Sulfide, Pyrolysis, Solar Reactor, Hydrogen, Sulfur Compound
Title:
Kinetic Modeling of Sunflower Oil Methanolysis Considering Effects of Interfacial Area of Reaction System
Author(s):
S. Farajzadeh Bibalan , S. M. Sadrameli
Paper language: English
Abstract:
In this study, a kinetic model is proposed for Sunflower oil methanolysis in which the effect of the interfacial area on the reaction system has been investigated. The model is based on the combination of mass transfer and kinetics. Rate constant of the reaction is obtained by fitting of the experimental data with the model. Based on this model, activation energy is equal to E/R=3390 K. This model was applied to the transesterification of soybean oil with some modifications on Misek’s equation and interfacial tension correlation. Methyl ester production at two different mixing intensities was evaluated. By using this model, theoretical conversion is calculated and is compared with the experimental data taken from literature. An acceptable agreement has been obtained between two sets of data. Based on the experimental data shown in the paper, agitator speed has no significant effect on the conversion. Therefore, it can be concluded that at a temperature of 55C or higher, the model parameter approaches to the rate constant of reaction and the agitation speed does not affect the kinetics.
Title:
Creep and Stress Relaxation Behavior of Polypropylene, Metallocene-Prepared Polyethylene and their Blends
Author(s):
M. Razavi , Nouri
Paper language: English
Abstract:
Creep and stress relaxation of a polypropylene (PP)-based copolymer, a metallocene-prepared linear low density polyethylene (m-LLDPE) and their m-LLDPE/PP blends have been investigated. Struik and Nutting relationships were used for fitting the data obtained from the creep experiments. A relatively good agreement was found between the Struik model and the experimental data obtained from PP and the 50/50 blend, however, the results showed that the validity of the model is less for the m-LLDPE itself. A good correlation was also found for the Nutting relationship and the experimental data. Maxwell and Kohlrausch-Williams-Watts (KWW) equations were used to fit the data obtained from stress relaxation experiments. The results indicated that while the Maxwell model was not good enough to predict the stress relaxation time, KWW model could fit the data much better. Analysis of the data with KWW equation revealed that the relaxation time increased with m-LLDPE content, but not significantly. However, the factor that describes the width of relaxation time distribution reduced with m-LLDPE, showing that m-LLDPE had the broadest relaxation time distribution compared to that of PP and the blends.
فصلنامه مهندسي شيمي داراي رتبه علمي - پژوهشي (فني مهندسي) به زبان انگليسي
سال نهم، شماره 2 (پياپي 27)، Spring 2012
Title:
Application of a Kinetic Model for Studying Impurities Effect on Crystallization of NaCl, KBr, ADP and Sucrose Solutions
Author(s):
Gh. Sodeifian , M.H. Niknam
Paper language: English
Abstract:
Addition of impurities has an important role on the kinetic crystallization. Therefore, influence of impurities on the crystallization kinetics of NaCl, KBr, ADP and Sucrose solutions was investigated in a fluidized bed crystallizer. The growth and dissolution rates were related to the super saturation and impurity concentration. A strong mathematical model is applied to describe crystal growth rates within aqueous solutions as a function of impurity concentration. The model tries to relate the step velocity to the useful parameters such as the surface coverage (θeq), as well as the effectiveness factor of impurity, α. When α>1, the step velocity is stopped at θeq <1 (incomplete coverage of the active sites for adsorption). In the case of α=1, the velocity reaches zero just at θeq=1 (complete coverage) but approaches a limiting value. The value of α is changed by stereo chemical factors and decreases as the supersaturation is increased. The Langmuir adsorption isotherm is used to relate the relative step velocity with the impurity concentration in solution. Experimental results show that increasing the amount of impurity concentration leads to a decrease in the step velocity. Experimental data and model predictions have been compared to show that the agreement between them is very good. The obtained results are suitable for designing and quality control of the crystallization processes in chemical industries.
Title:
Using PERVAP 2201 Membrane in Vapor Permeation Facilitated Isopropyl Propionate Production through Esterification Reaction
Author(s):
E. Ameri , A. Moheb
Paper language: English
Abstract:
A commercial flat polymeric membrane (PERVAP 2201) was employed in vapor permeation process to selectively remove water from the reaction atmosphere during the synthesis of isopropyl propionate from iso-propanol and propionic acid. The reaction was carried out in a bench scale batch reactor at three different values of alcohol/acid molar ratio (1:1, 1.5:1 and 3:1) with 3 wt% para toluene sulfonic acid (with respect to acid) as catalyst.. The polymeric membrane was in contact with only the volatile components, namely water and isopropanol, for a long period of time with no detectable defect. The conversion of the reversible esterification reaction was enhanced by simultaneous employing of the chemical reaction and the vapor permeation process, where in a set of experiments almost complete conversion was achieved after only 140 minutes. Also, results revealed that initial molar ratio of the reactants had strong effects on the acid conversion and water permeation flux through the membrane.
Title:
Manganese Oxide Promoted LaCoO3 Nano-Perovskite for Oxidation of a Model Exhaust Gas
Author(s):
S. Farhanian Moghadam , A. Malekzadeh , M. Ghiasi , F. Karimi , Y. Mortazavi
Paper language: English
Abstract:
Catalysts with the formula of LaCoMnxO(3+δ), where x is 0.0, 0.2, 0.3 and 0.5 were studied for CO and C2H6 oxidation. Ethane was selected as a model for hydrocarbon combustion. Samples were prepared by the citrate method and calcined at 600oC for 8 h. Prepared catalysts were characterized by FT-IR, XRD, SEM, TEM, TPR and EDS analyses. Structural studies show that the manganese oxide addition up to 0.5 mol, i.e. 50%, has no effect on the LaCoO3 perovskite phase formation. Crystallite size of different phases, comprising perovskite and manganese oxide, was determined by the Scherrer equation. Addition of 0.3 mol manganese was observed to improve the catalytic property of the lanthanum cobaltite; oxidizes the CO and hydrocarbons at lower temperature.
Title:
New Perturbation Model for Prediction of Amino Acid and Peptide Activity Coefficients
Author(s):
M. R. Dehghani , E. Salehi , A. R. Fazlali
Paper language: English
Abstract:
In this work, a new thermodynamic model based on the perturbation theory is presented. A new hard spheres equation of state as a reference term is applied to correlate the activity coefficient of amino acids and peptides in binary aqueous solutions. The new hard sphere equation of state has been recently proposed by Dehghani and Modarress [11] and has been applied for different theories and showed excellent capability. In this model dipole-dipole and Lennard-Jones interactions are considered. The results have been compared with similar models and it is shown that application of the new hard spheres equation of state has caused an improvement in the results of perturbation model.
Keywords:
Activity Coefficient, Hard Sphere, Perturbation Model, Amino Acid
Title:
CFD Investigation of Hydrodynamics in an Industrial Suspension Polymerization Mixing Reactor
Author(s):
M. H. Vakili , M. Nasr Esfahany
Paper language: English
Abstract:
Turbulent flow field in a 200 m3 industrial suspension polymerization reactor, which is a baffled agitated vessel, was simulated using CFD. Multi-reference frame (MRF) methods and k-ε turbulence model were used to solve turbulent flow equations. It was found that turbulent flow field in reactor is non-homogenous. This non-homogeneity is especially common among three compartments of a reactor based on turbulent kinetic energy (TKE) dissipation rate. A compartment around the impeller with very high rate of TKE dissipation (impeller zone), a compartment around the baffles with a relatively high rate of TKE dissipation (baffle zone) and a relatively big compartment in bulk of flow with low TKE dissipation rate (circulation flow). Therefore a three-compartment model was used to explain the non-homogeneity of turbulent flow field. The parameters of this model are compartment volume ratios (μi and μb), compartment energy dissipation ratios (λb and λi) and exchange flow rates (Qi and Qb), which were obtained from simulations for different agitation rates.
Title:
Mean Drop Size and Drop Size Distribution in a Hanson Mixer-Settler Extraction Column
Author(s):
M. Torab , Mostaedi , J. Safdari , M. Asadollahzadeh
Paper language: English
Abstract:
Drop size distribution and Sauter-mean drop diameters have been measured in a pilot scale Hanson mixer-settler extraction column for two different liquid-liquid systems. The experiments were carried out for both mass transfer directions. The effects of agitation speed and dispersed phase and continuous phase flow rates have been investigated under a variety of operating conditions. Mean drop diameter axial profiles show a strong nonuniformity, while drop size distribution does not change significantly with the column height. Sauter mean diameter and drop size distribution are strongly affected by agitation speed and interfacial tension. Significant, but weaker are the effects of continuous phase and dispersed phase flow rates. An empirical correlation for mean drop size as a function of Weber number, dispersed phase holdup, and viscosities ratio is suggested. In a further correlation, the dispersed phase holdup is replaced by flow rates which will certainly be known in a practical case.
Keywords:
Sauter, mean Diameter, Drop Size Distribution, Hanson Mixer, settler, Dispersed Phase Holdup
Title:
Solution of Noncatalytic Packed Bed Reactors Equations by Finite Element Method
Author(s):
A. Afshar Ebrahimi , H. Ale Ebrahim
Paper language: English
Abstract:
The partial differential equations describing reaction of a trace component in the gas stream in a packed bed of solid reactant or adsorbent are solved by Rayleigh-Ritz finite element method. These equations consist of a PDE along the reactor which is accompanied with semi time dependent diffusion-reaction equation in each pellet. Two gas-solid reaction models have been considered as the reaction rate expression of the pellets in this work. These reaction rates provide nonlinearity in the PDEs of the pellets. Reactions with considerable structural changes such as sulfation of calcined limestone in packed column have been considered too. The finite element method analyzed the PDEs equations, even in the presence of steep gradients associated with nonlinearities along the packed column and the pellets equations.
Keywords:
Finite Element Method, Rayleigh, Ritz, Nonlinear Partial Differential Equations, Non, catalytic Packed Bed Reactors
فصلنامه مهندسي شيمي داراي رتبه علمي - پژوهشي (فني مهندسي) به زبان انگليسي
سال نهم، شماره 3 (پياپي 28)، Summer 2012
Title:
Production of 1-Butene via Selective Ethylene Dimerization by Addition of Bromoethane as a New Promoter to Titanium-Based Catalyst in the Presence of Tetrahydropyran Modifier and Triethylaluminum Co-Catalyst
Author(s):
S. H. Mahdaviani , M. Parvari , D. Soudbar
Paper language: English
Abstract:
The quantity of by-products and polymeric compounds produced in the ethylene dimerization reaction is a critical factor from the industrial viewpoint. It may lead to the shutting down of 1-butene reactors. It is, therefore, highly desirable to identify the factors that are responsible for the formation of polymeric materials and how the formation of these heavy compounds can be minimized or prevented. A significant way to overcome this drawback is by judicious choice of the catalyst and reaction conditions. In this regard, a systematic study has been carried out on a titanium-based catalyst using tetrahydropyran (THP) and tetrahydrofuran (THF) as modifiers, and bromoethane as a new efficient accelerator in combination with triethylaluminum (Et3Al) activator. The addition of bromoethane led to dramatic increases in the rate of reaction and yield, and remarkable decreases in the amounts of heavy and polymeric compounds. It is proposed that specific weak coordination of the halide to the dimeric Et3Al may result in breakage of the Et3Al dimer and the release of monomeric Et3Al. The latter is more reactive than Et3Al dimer and leads to the facile generation of an increased number of the active metal sites that are responsible for the dimerization reaction. Finally, the catalytic performance of the novel homogeneous system [titanium tetrabutoxide Ti(OC4H9)4)/THP/Et3Al/bromoethane] has been examined under various operating conditions.
Keywords:
Ethylene dimerization, Heavy Compounds, THP, Promoter, Bromoethane
Title:
Compartment Mixing Model in a Stirred Tank Equipped Dual Rushton Turbine
Author(s):
F. Fakheri , J. Moghaddas
Paper language: English
Abstract:
Knowledge of mixing time is of fundamental importance for investigation of mixing efficiency in agitation systems. The mixing time obtained by using the correlation and formula in large scale mixing systems was incorrect. Again, the number of available correlations in this scale of mixing systems is limited. To predict the mixing time of stirred tanks with dual impellers commonly used in industry, a third-compartment mixing model was used. The time of homogenization of the charge (mixing time) was calculated from the time dependency of the local concentration of tracer measured at various locations. Experimental data on mixing time were obtained with a conductivity technique. In the present study distribution of tracer in the bulk of the liquid was described by compartment model (CM) as well as for stirred vessel with dual Rushton impellers. As for the model, a good agreement between the experimental data and the calculated values was apparent.
Keywords:
Mixing Time, Compartment Model, Rushton Turbine, Tracer, Conductivity
Title:
Dielectric Study on Polar Binary Mixtures of (Ester-Alcohol) at 298.2 K
Author(s):
A. Ghanadzadeh , H. Ghanadzadeh , M. Alinejad
Paper language: English
Abstract:
Dielectric constant measurements were made on binary mixtures of ethyl acetate (EA) and butyl acetate (BA) with the two amyl alcohols (iso-amyl alcohol (IAA) and tert-butyl alcohol (TBA)) for various concentrations at T = 298.2 K and in a frequency of 100 kHz. In order to obtain valuable information about heterogeneous interaction (interactions between the unlike molecules), the Kirkwood correlation factor, the Bruggeman dielectric factor and the excess permittivity were calculated.
Title:
Methane Combustion and CO Oxidation on Ag-Doped LaMn0.8Cu0.2O3 Mixed Oxides Prepared by Pechini and Sol–Gel Methods
Author(s):
M. Abdolrahmani , M. Parvari , M. Habibpoor
Paper language: English
Abstract:
Lanthanum in the A-site of LaMn0.8Cu0.2O3 perovskite was partially substituted by silver. La1–xAgxMn0.8Cu0.2O3 samples (x=0, 0.1, 0.2, 0.3) were prepared by the two Pechini and sol–gel methods and their catalytic activity was evaluated for CH4 combustion and CO oxidation reactions. FT-IR analysis of different samples before calcination confirmed the formation of different complexes between the elements. Calcined samples were characterized using XRD, TPR, BET, SEM and XRF techniques. XRD results revealed that the Pechini method led to perovskite structures with higher purity and that segregation of Ag in samples prepared by the sol–gel method was higher. SEM images and EDS results for samples before and after catalytic tests showed that the Pechini samples had a lower particle size and better distribution of the elements. The catalytic results indicate that the oxidation activity increased with the amount of Ag in the oxide, but the stability of the structure decreased.
Title:
Experimental Investigation on the Effect of Parameters Influencing the Performance of a Horizontal Styrene-Water Separator
Author(s):
Y. Jafarzadeh , S. Shafiei , A. Ebadi , M. Abdoli
Paper language: English
Abstract:
The separation of immiscible liquids plays an important role in the oil and petrochemical industries. In the outlet stream of a catalytic reactor of dehydrogenation of ethyl benzene to styrene monomer, water is present because it is used as high pressure steam to provide reaction heat. Therefore, aqueous and immiscible organic phases should be separated in a horizontal separator before fractionation. The objective of this work is to study the separation of ethyl benzene, styrene, and water in a horizontal pilot scale separator. Experiments showed that the performance of the separator is affected by feed flow rate and composition. Furthermore, the thickness of mesh installed in the inlet zone of the separator has an effect on the hydrodynamic behavior of the separator and its performance.
Keywords:
Horizontal Separator, Phase Separation, Immiscible Liquids, Styrene Production
Title:
Analysis of the Effective Parameters on Potato Powder Quality Produced by a Spray Dryer
Author(s):
D. Saydi , M.S. Hatamipour
Paper language: English
Abstract:
Spray dryer was used to produce potato powder from potato juice. Turning potatoes into powder will increase its substance durability, ease of transportation and the storage. The important factors affecting the powder produced by spray dryer include inlet air temperature, volumetric flow rates of feed and air. Experiments were conducted according to Taguchi’s method by considering 3 levels for each one of the mentioned parameters and 2 levels for atomizer’s nozzle diameter. The objective was to obtain the optimized process conditions for producing potato powder with desirable color. By analyzing the experimental results, the optimized conditions for producing potato powder by spray dryer were determined. It was also revealed that by adding 1 percent maltodextrin (dry mass basis) to the feed, the product’s adhesion will decrease significantly and the amount of product will be increased.
Title:
Investigation of Hydrogen Sulfide Oil Pollution Source: Asmari Oil Reservoir of Marun Oil Field in the Southwest of Iran
Author(s):
A. Telmadarreie , S. R. Shadizadeh , B. Alizadeh
Paper language: English
Abstract:
Marun oil field is located in the southwest of Iran and consists of two oil reservoirs named Asmari and Bangestan. Asmari oil reservoir has been producing sweet oil and gas since 1964, but for the first time a high amount of hydrogen sulfide gas was observed in one well of this reservoir in 1980. Moreover, the Bangestan oil reservoir is located deeper than the Asmari oil reservoir and has been producing sour oil and gas since 1972. This paper represents the conducted study on the determination of hydrogen sulfide oil pollution sources in the Asmari oil reservoir. There are two hypotheses for sources of hydrogen sulfide oil pollution in the Asmari oil reservoir; first, hydrogen sulfide gas migration from Bangestan oil reservoir and second, sour gas injection migration. Data of well souring history, hydrogen sulfide gas concentration of wells, volume of gas injection and RFT analysis were used to investigate these hypotheses. The results showed a similar trend of gas injection volume and hydrogen sulfide gas concentration of wells, which decreased over time. Also, the results demonstrated that the migration of gas injection is a source and cause of spreading of hydrogen sulfide gas in the Asmari oil reservoir.
Keywords:
Marun, Asmari, Hydrogen Sulfide, Reservoir souring, Sour gas injection
