Iranian Journal of Chemical Engineering (IJChE)

Abstract Analytical gas-permeation models for predicting the separation process across  membranes (exit compositions and area requirement) constitutes an important and necessary step in understanding the overall performance of  membrane modules. But, the exact (numerical) solution methods suffer from the complexity of the solution. Therefore, solutions of nonlinear ordinary differential equations that govern the performance of the membrane modules for gas separations by approximate and asymptotic methods are useful in the design and comparison of processes. In this work, the asymptotic methods were applied for predicting the performance of nanometric tubular ceramic membranes in the separation of binary gas mixtures with cocurrent and countercurrent flow patterns. Also, the exact (numerical) solutions of the governing equations using the fourth order Rung-Kutta technique were proposed. The comparison of the results showed a good agreement between the exact solution and asymptotic analysis methods over the whole range of selectivities (). Because, the asymptotic curves into the former () and latter () boundaries had a suitable overlap with each other to cover the whole range of selectivities. The accuracy of this method was verified by a comparison of the predicted results with different literature experimental data and mathematical models. This result suggests the use of the asymptotic analysis method to provide excellent shortcut, preliminary design information.
 
 
 

Abstract > The motion and shape of a flattened drop and bubble through another continuous liquid phase (conveying phase) are investigated experimentally, using a narrow gap HeleShaw cell. Seven different liquid-liquid systems were tested. In all cases the continuous phase was the more viscous wetting phase. A number of observations on the shape and motion of the elongated flattened drops are noted and discussed. In the capillaritydominated (Ca<1.69×10-6) region, the irregular shape of the discontinuous phase drops changed with time and position, and the drop velocity was much lower than that of the conveying phase. Three different shapes of stabilized elongated drops were observed at higher Capillary numbers. The conditions that lead to the appearance of stabilized elongated drops are discussed. The velocities of these stabilized elongated flattened drops were 2 to 4.7 times higher than that of the conveying liquid. A correlation to predict the elongated flattened drop shape as a function of the dimensionless parameters governing the system is developed based on the experimental results.

Abstract The ternary system of Portland cement-microsilica-limestone has been studied by investigating its set and strength behaviours. A number of different cementitious systems comprised of 0, 10, 15, 20, 25, and 30% limestone powder and 0, 4, 6, 8, 10, 12, 14, and 16% microsilica were designed and prepared. The cementitious systems were then characterized by determining their relative workability and measuring their initial and final setting times and also their 7- and 28-day compressive strengths using paste specimens prepared at a constant W/C-ratio of 0.38. Total 77-day shrinkage of the systems was also measured. The obtained results reveal that both 7- and 28-day compressive strengths increase with increasing microsilica up to 12% and decrease with increasing the percentage of limestone powder. A comparison of the results confirms the possibility of replacing Portland cement by a proportioned mixture of microsilica and limestone powder for enhancing the strength behaviour or producing composite cements containing relatively high proportions of limestone powder with no loss in 7- and 28-day compressive strengths compared to plain cement.

Abstract A mathematical model is developed for describing the dynamic behavior of the gas phase ethylene polymerization reactor. The model is based on the dynamic two-phase concept of fluidization in which the bubbles may contain solid particles and the emulsion is capable of containing more gas than that of minimum fluidization. The fluidized bed reactor is divided into several serial sections consisting of bubble and emulsion phases. Flow of the gas is considered as plug flow through the bubbles and perfectly mixed through the emulsion phase. Polymerization reactions occur in both emulsion and bubble phases. Variation of the process variables as well as the polymer properties were studied as a function of operating time. The bed height was controlled by the product withdrawal rate with a PID controller. The results of the model were compared with the experimental data and a good agreement was observed between the model prediction and actual data. The simulation results indicate that a significant amount of polymer production (roughly 12%) takes place in the bubbles.

Abstract
Uncontrolled release of light non aqueous phase liquids (LNAPL) such as diesel, gasoline, fuel oils and lubricating oils from transporting vehicles, pipeline and underground storage tanks (UST) could lead to the migration of contaminants to the subsurface soil and ground water. There is a high interfacial tension (IFT) between LNAPL molecules and water molecules that makes water a non-efficient cleaning material for removing LNAPL from the soil. Nowadays, surfactants (surface active agents) can promote the enhanced removal of LNAPL from the subsurface through mobilization and solubilization. Encouraging results were achieved from laboratory and field results. The aim of this study is to improve the clean up efficiency of surfactant-flooding for two different surfactants; Triton X-100 and Sodium Dodecyl Sulfate which are known as mobilizing and solubilizing surfactants, respectively, by adding alkaline (increasing pH) and foam producing substances. It is shown here that adding alkaline improves the performance of Triton X-100 in removing LNAPL from the contaminated soil by about 8 percent, but spoils the remediating capability of Sodium Dodecyl Sulfate by about 3 percent. Also, adding a foaming agent helps the surfactant solution in removing the LNAPLs out of the soil by more than 5 percent.

Abstract The boundary layer convective heat transfer equations with low pressure gradient over a flat plate are solved using Homotopy Perturbation Method (HPM), which is one of the semi-exact methods. The nonlinear equations of momentum and energy solved simultaneously via HPM are in good agreement with results obtained from numerical methods. Using this method, a general equation in terms of Pr number and pressure gradient (λ) is derived which can be used to investigate velocity and temperature profiles in the boundary layer.

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.

Abstract Carbon black or soot is a carbon rich material which is widely used as a modifier and filler. Usually carbon black is produced via thermal decomposition of heavy hydrocarbons. This process is too complex to be modelled fundamentally. In this study, the effect of reaction feed composition on the soot production yield was studied experimentally in a lab-scale reactor. The soot production was optimized based on feed Composition and economical aspects. The effects of reaction time and temperature on the product particle size produced using the optimized feed were also investigated experimentally. Then a semi-empirical model was developed to predict soot particle size as a function of reaction time and temperature. The model has been validated upon the experimental data successfully.

Abstract This research work is concerned with the bioconversion of a heavy hydrocarbon cut from a petroleum refinery using native anaerobic consortia. The heavy cut is taken from one of the end-cuts of the vacuum distillation column of Tehran refinery which is normally fed into Isomax unit (a catalytic cracking process) called Isofeed. The consortia for this study were prepared from the petroleum-contaminated sludge and soils from Abadan, Shiraz, Isfahan and Tehran petroleum refineries of Iran. Nine microbial samples were collected (A, B, C, and I) and examined. Microorganisms were cultivated in an anaerobic medium to which Isofeed from Tehran refinery was added under anaerobic conditions. After twice sub-culturing the samples, the oil was separated from the liquid and examined to identify its bioconversion extent. For this
purpose, a column chromatograph method was used to separate saturates, aromatics and resins content of the oil. The results demonstrate that consortia A and C were able to increase the saturated and aromatics fractions of the oil and reduce the resins content of the oil. The saturated fractions of the bio-treated oil were also analyzed by a GC-MS analytical instrument. The GC-MS results revealed that the amount of normal chain hydrocarbons are reduced and the branched and cyclic hydrocarbons are increased.

Abstract Surfactants are one of the major components (10- 18%) of detergents and household cleaning products and are used in high volumes in developed countries. In the present research work, the ability of rice husk as a low cost adsorbent for anionic and nonionic surfactants in wastewater has been studied.
The maximum removal efficiency for anionic surfactants was 97%, in an aqueous solution that contains 10mg/lit sodium linear alkyl benzene sulphonate in pH 2 and for nonionic surfactants was up to 75% in an aqueous solution that contains 20mg/lit nonyl phenol ethoxylate in pH 6-7.
The mechanism of surfactant removal by rice husk was attributed to the physicochemical characteristics of rice husk. In addition, the size of micelles and critical micelle concentration are two important factors in the removal yield.
 
 
 
 

Abstract Composites of polyaniline with calcium carbonate particles (PANI/CaCO3) with different CaCO3 content (0-40 %w/w) were prepared. Two different methods of in situ polymerization and solution mixing were used for PANI/CaCO3 composite preparation. The composite was characterized using FT-IR, SEM, electrical conductivity measurement and cyclic voltammetry techniques. The incorporation of CaCO3 particles in polyaniline matrix in both methods of composite preparation was confirmed by FTIR results. Electrical conductivity measurements showed that the conductivity of the composite decreases by increasing the CaCO3 loading in polyaniline. Also, the anticorrosive property of the PANI/CaCO3 composite coating on iron samples was investigated in various corrosive environments. According to the results, the corrosion rate or corrosion current of PANI/CaCO3 composite coated iron coupons was much lower (96.75%) than polyaniline coated samples. Also, results showed that the corrosion current of composite coated samples varies with the variation of the CaCO3 content in composite coating, and the optimum CaCO3 content of composite coating to achieve the best anticorrosive performance on iron is 10 %w/w.

Abstract In this research, photocatalytic degradation method has been introduced to clean up Spent Caustic of Olefin units of petrochemical industries (neutralized Spent Caustic by means of sulfuric acid) in the next step, adaptable method and effective parameters in the process performance have been investigated. Chemical oxygen demand (COD) was measured by the commercial zinc oxide that synthesized with precipitation synthesis method in a two-shell photoreactor. The percent of reduction of COD in the photocatalytic process was modeled using Box–Behnken design and artificial neural network techniques. It was concluded that the ANN was a more accurate method than the design of experiment. The effect of important parameters including oxidant dosage, aeration rate, pH, and catalyst loading was investigated. The results showed that all of the parameters, except pH, had positive effects on increasing COD removal. According to the obtained results, adsorption and photolysis phenomena had a negligible effect on COD removal.

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 CH 4 and H 2S 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 (H 2) and a high-value nano-material of carbon. The effects of H 2S to CH 4 feed ratio and reactor temperature on hydrogen, carbon black, S2 and CS 2 formation are investigated. The results show complex behavior in the products because of the difference in CH 4 and H 2S pyrolysis temperatures. It can be seen that for H2S/CH 4>2, the yields of H2 and CS 2 reach a local and global maximum at H2S/CH 4=5, respectively. A comparison performed between the presented results and the results of Towler and Lynn, and Abanades demonstrates a good agreement.

Abstract Ibuprofen solubility in supercritical carbon dioxide was measured using a dynamic apparatus at a pressure between 80 and 140 bars at three different temperatures, 308.15, 313.15 and 318.15 K. The mole fraction of Ibuprofen in fluid phase was in the range of 0.015 × 10 -3 - 3.261 × 10 -3 at the mentioned operational condition. Modified Mendez-Santiago and Teja equation were used to check the consistency of the experimental data. Results were correlated using the Stryjek and Vera equation of state with the van der Waals 1-parameter (vdW1) and 2-parameters (vdW2) mixing and combining rules. Interaction parameters along with the percentage of the average absolute relative deviation (%AARD) were displayed. Also, the Lydersen group contribution methods were used for predicting the physicochemical and critical properties of the Ibuprofen.

Abstract Migration of styrene monomer from polystyrene (PS) dishes was conducted during this research at temperatures of 5, 20, and 40 °C. According to the Food and Drug Administration (FDA) regulations, these experiments were performed in contact with 10%ethanol as a food simulant for the oil in water (o/w) emulsions. The dishes were filled in each of the defined temperatures and stored for 35 days. In relatively close intervals (1, 7, 15, 24, and 35 days) the amount of migration which occurred was determined by means of Head Space Gas Chromatography Mass Spectrometry (HS-GC-MS). By increasing storage time and temperature, the amount of migration was increased and in all times and temperatures styrene monomer was detected. In addition, a mathematical model based on the Fick’s second law was validated to predict migration from packaging material into the 10% ethanol. The resulted diffusion coefficients were 3.6×10-18, 4.9×10 -18, and 6×10 -18 (m2/s) in 5 ,20 and 40 °C respectively.

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-Â 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 (Ïi and Ïb), compartment energy
dissipation ratios (Îb and Îi) and exchange flow rates (Qi and Qb), which were obtained from simulations for different agitation rates.

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.

Abstract The hydrocarbon plus fractions that comprise a significant portion of naturally occurring hydrocarbon fluids create major problems when determining the thermodynamic properties and the volumetric behavior of these fluids by equations of
state. These problems arise due to the difficulty of properly characterizing the plus fractions (heavy ends). Proper characterization of the heavier components is important when cubic equations of state and/or solid formation thermodynamic models are used to describe complex phase behavior of reservoir fluids. The effect of heavy fractions
characterization on thermodynamic modeling of wax precipitation has been investigated using different models including Won, Pan and Proposed Models. In order to characterize the plus fraction (heavier part) as a series of pseudocomponents, a probability model that expresses the mole fraction as a continuous function of the
molecular weight has been used. The study has been conducted using several mixtures. Two different SCNs (Single Carbon Number), C 7+ and C10+, were chosen. The chosen SCNs were distributed to multicomponents of five, six, and/or ten using continuous method. The results showed that the fractioning is required to be able to predict wax precipitation. Distribution of C 10+ using a proper distribution function has shown improvement in predictions of WAT and the amount of wax deposited in comparison with the characterization of C7+ using semi-continuous approach. In predicting WAT and the amount of wax build up the developed model showed superiority over the others.

Abstract > In this paper a chemical method applied to synthesize exfoliated graphite (EG) is presented. In this method graphite intercalation compound (GIC) was firstly synthesized by chemical treatment of graphite flakes using a mixture of sulfuric and nitric acids followed by thermal shock of GIC at 1000°C to produce EG. The bulk density of synthesized EG was found to be as low as 4.5 kg/m3. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used for identification and characterization of different materials. According to the XRD observations, the GIC was identified as graphite bisulfate with stage 2, and residue GIC and EG had nearly the same diffraction pattern, but with distinctly lower intensity. In accordance with SEM results the residue graphite bisulfate was swelled in comparison with the graphite flake. The oil sorption capacity of synthesized EG in this work was studied by common static and dynamic tests and compared with other sorbents. The results show the superior capability of EG for oil spill cleanup.

Abstract Lennard-Jones-Devonshire equation of state is an old but theoretical based EOS. The concept of the nearest neighboring molecules or coordination number is proposed to be a function of temperature and volume, whereas it is a constant in the original. The dilute gas and hard sphere limits of molecules are employed to determine this function. Improvement of this modification is demonstrated by property calculations for Lennard-Jones fluid. Results of the modified LJD equation of state offer senior accord with simulation data of Lennard-Jones fluid than those of the original version.    

Abstract "> Phase inversion phenomenon occurs in many industrial processes including liquidliquid dispersions. Some parameters such as energy input or the presence of mineral compounds in the system affect this phenomenon. The aim of this research is to study the speed of rotation or energy input at a range of 400 to 800 rpm in a batch liquid-liquid system containing toluene and water. The presence of sodium chloride and magnesium sulphate in the system was also studied. It was shown that the increase of energy input had a more obvious effect on oil in water (O/W ) dispersion at lower values of holdup. It was also shown that the ambivalence (o/w → w/o) region of the phase inversion curve shifted downward and became wider as a result of the decrease in interfacial tension. It was observed that inorganic salt, used in both single and dual (mixed) shapes, enhanced phase inversion for O/W dispersion. Therefore, the greater the ionic strength of salt, the greater the tendency to phase inversion is.

Abstract The effect of temperature (25, 40, 55 and 70°C) and weight fraction of MWCNTs (0.125, 0.25 and 0.5 %wt) on the viscosity of nanofluids containing pristine and functionalized MWCNTs have been investigated. For this purpose, all of the measurements were carried out in triplicate and were analyzed using two factors completely randomized design and comparison of data means is carried out with Duncan’s multiple range test. The level of statistical significance was determined at 95%. The experimental and statistical results show that the viscosity of the both nanofluids increases with respect to the weight fraction and by decreasing the temperature. Statistical analysis of viscosity shows that temperature, weight fraction and interaction effect of them have a significant influence on the viscosity of nanofluids containing pristine and functionalized MWCNTs (α=0.05). Meanwhile, the results show that there was a significant difference at different levels of temperature on the viscosity of the both nanofluid.

Abstract Solubility data of solid in aqueous and different organic solvents are very important physicochemical properties considered in the design of the industrial processes and the theoretical studies. In this study, experimental solubility data of 666 pharmaceutical compounds in water and 712 pharmaceutical compounds in organic solvents were collected from different sources. Three different artificial neural networks including multilayer perceptron, radial basis function and support vector machine were constructed to predict the solubility of these different pharmaceutical compounds in water and different solvents. Molecular weight, melting point, temperature and the number of each functional group in the pharmaceutical compound and organic solvents were selected as the input variables of these three different neural network models. The neural network predictions were compared with the experimental data and the SVR-PSO model with the Average Absolute Relative Deviation equal to 0.0166 for the solubility in water and 0.0707 for solubility in organic compounds was selected as the most accurate model.

Abstract The optimization of adsorption-based operations requires an accurate model to represent the separation process. In the present study, single-component adsorption data of L-lysine on its imprinted polymer were fitted to Freundlich, Langmuir-type and Jovanovic-type models. L-Lysine imprinted polymer (LLIP) was prepared by free radical solution polymerization. The best estimate of the parameters of these models by regression analysis was obtained. The statistical analysis of results showed that the experimental data fit the Jovanovic-Freundlich mode, better than other models in terms of f value. The best prediction of retention capacity equal to 0.186 mmol lysine per g of LLIP, which is the nearest value to the experimental data, was obtained by applying the Jovanovic model.
 
 
 
 

Abstract In this contribution Artificial Neural Network (ANN) modeling of the hydrocracking process is presented. The input–output data for the training and simulation phases of the network were obtained from the Tehran refinery ISOMAX unit. Different network designs were developed and their abilities were compared. Backpropagation, Elman and RBF networks were used for modeling and simulation of the hydrocracking unit. The residual error (root mean squared difference), correlation coefficient and run time were used as the criteria for judging the best network. The Backpropagation model proved to be the best amongst the models considered. The trained networks predicted the yields of products of the ISOMAX unit (diesel, kerosene, light naphtha and heavy naphtha) with good accuracy. The residual error (root mean squared difference) between the model predictions and plant data indicated that the validated model could be reliably used to simulate the ISOMAX unit. A four-lumped kinetic model was also developed and the kinetic parameters were optimized utilizing the plant data. The result of the best ANN model was compared to the result of the kinetic model. The root mean square values for the kinetic model were slightly better than the ANN model but the ANN models are more versatile and more practical tools in such applications as fault diagnosis and pattern recognition.