Nashrieh Shimi va Mohandesi Shimi Iran
Year:2011 | Volume:29 | Issue:4 (59)|Papers Count:16

A new method based on modifying the McCain method for preparing an equation of state for use in a combinatorial simulation is presented. The method consists of three steps: Breaking down the heavy component and getting agreement with saturation pressure data, grouping, and getting agreement with volumetric data. The heavy component is broken down into 45 single carbon numbers using the gamma function. The critical temperature, the critical pressure and the acentric factor are determined for each single carbon number using the best available correlations. Agreement with the experimental saturation pressure is the obtained by adjusting the molecular weight of the heavy component. The extended composition is the grouped into three multi carbon numbers. The critical properties for the grouped components are the determined in such a way that the original a and b coefficients that were used to get a good fit with the saturation pressure data are maintained. The little deviation caused in calculating the adjusted saturation pressure, as a result of grouping, is corrected by adjusting the critical temperature of the heaviest single carbon number. In the end, volumetric data are fitted using a volume translation parameter as the adjusting parameter. The error obtained in the calculation of the relative volume and the gas phase compressibility factor in the CCE experiments for four samples whose experimental data were ayailable was less than 5%. The errors in obtaining the two phase compressibility factor and the liquid saturation volume in the CVD experiments for the same four samples were under 4% and 15%, respectively. The errors obtained using the original McCain method for the latter two quantities were 8% and 19%, respectively.

The up-flow Sludge Blanket Filtration (USBF) is a novel and efficient wastewater treatment process which is a modification of conventational activated sludge system. The purpose of this study was to determine the efficiency of USBF process in biological phosphorus removal and to achieve the optimized hydraulic retention time according to the maximum phosphorus removal in the system. The experiments were carried out using a pilot scale USBF plant with a total volume of 60 liters by operating in different hydraulic retention times with flow rates of 0.57, 0.67, 0.8, 1.0, 1.33 and 2L per hour and the COD/P ratio around 50 at pH from 6.5 to 7.8 and room temperature (i.e.20±2oC). The experiments results according to the phosphorus removal showed that the system could commonly achieve steady state in a short time in flow rates of 0.8 and 0.67, and the phosphorus removal efficiency of more than 90 percent, but in the flow rates of 1.0, 1.33 and 2L per hour it would take a longer time to achieve the steady state and the desired phosphorus removal rate. At the end statistical analysis were carried out to determine an economical option for the hydraulic retention time for the biological phosphorus removal in this process, that it was 10 h for the hydraulic retention time in the clarifier.

Environmental concern regarding the formation and accumulation of greenhouse gases, in particular, carbon dioxide has persuaded the individual researchers and scientific institution to perform extensive studies on reduction and elimination of the latter gas. Recently, application and continuous recycle of carbon dioxide in a special power generation cycle has attracted a considerable attention. In such as cycle, Called Continuous CO2 Recycle (CCR), carbon dioxide is first hydrogenated to methane and water. Methane is thena applied either in a fuel cell or in a gas turbine cycle to generate electrical energy. A part of the generated power is allocated to the electrolysis of water and the resulting hydrogen gas is consumed in hydrogenation step which may be regarded as the key reaction in CCR processes. In the present study, catalytic hydrogenation of carbon dioxide has been conducted in a packed bed reactor. Formulation of an active catalyst and the determination of optimum operating parameters have been achieved within a research frame work applying Taguchi experimental design method. It was found that the catalyst consisted of 3% nickel supported on Na-Y zeolite demonstrated the highest activity 20 bar; molar feed³ and the optimum operating conditions were established as, T=230oC; P in addition, a mechanism for hydrogenation of CO2, based on ratio (CO2 /H2) =65/35. Langmuir-Hinshelwood formulation, was presented from which, a kinetic model was derived and the kinetic parameters were determined as functions of temperature.

During current years, the most of zinc has been produced from zinc sulphide ores by employing RLE (Roasting - Leaching - Electrowining) processing. Due to the SO2 emission and high cost of this process, researches are attempting to find an alternative for this process. In this research kinetic of alkaline leaching of sphalerite concentrate from BAMA plant has been studied using sodium hydroxide in presence of lead nitrite. Effective parameters such as temperature, sodium hydroxide concentration, lead nitrite concentration, steering speed, particle size and solid/liquid ratio were studied. It was determined that the dissolution rate increased with increasing lead nitrate, sodium hydroxide concentrations or temperature, but decreased with increasing particle size or solid/liquid ratio. Also steering speed has significant effect in leaching rate.In optimum conditions at 150min about 73% of zinc was obtained. The kinetic data were analyzed with the shrinking particle and shrinking core models. A new variant of the Shrinking Core Model (SCM) was properly fitted by the kinetic data. In temperature of 70oC, the value of R2 in surface chemical reaction and diffusion were 0.8 and 0.91 respectively. While in new model it was found to be 0.99.The orders of reaction with respect to [NaOH], [Pb (NO3) 2], (S/L) and particle size were 3.6122, 2.796, - 0.541 and -2.097, respectively. The activation energy for the dissolution was found to be 28.15 kJ/mol. Finally the validity of the results was estimated to be less than 9%. This model can be written as follows:1/5(1-x)-5/3-1/4 (1-x)-4/3+1/20=1.66x104[NaOH]3.612 [pb(NO3)2]2.796[S/L]-0.541 r0-2.097 exp (-28150.836/RT) t.

Turbulent air flow through a 90 degree bend under both stationary and oscillating cases, were investigated numerically in this paper. The well known k-· model was used for turbulence modeling while universal wall function was used for wall region. Steady developing turbulent air flow through stationary 90o circular-sectioned curved pipe was investigated numerically first and computational results were compared with previously published experimental data showing excellent agreement. Contours of the mean velocity and static pressure for both stationary and oscillating bend are plotted along the bend length. Results show that at the inlet plant of the bend, the primary flow accelerates near the inner wall, due to secondary flow generated from centrifugal force. In general, the velocity contours through stationary and oscillating bends show the same behaviour.

In this research, a series of cationic gemini surfactants with methylene chain spacer was synthesized and after purification their physico-chemical properties such as Critical Micelle Concentration (CMC) by surface tension measurements and conductometery, Kraft temperature and melting point were studied. The retarding effect of these cationic gemini surfactants in adsorption of C.I. Basic Red 27 onto polyacrylonitrile (acrylic) at boiling temperature was compared to their monomeric counterparts, Dodecyl Trimethyl Ammonium Bromide (DTAB). Adsorption kinetic of the basic dye onto acrylic in the presence of different concentrations of surfactants was evaluated by UV-VIS spectrophotometer. Results showed that retarding action of cationic gemini surfactants was higher than their monomeric surfactant. The retarding effect increased with increasing concentration for all surfactants. There was no significant correlation between spacer length and retarding effect of gemini surfactants.

Gas absorption process with chemical reaction by liquid solvents is widely used in the treatment of acid gases, gas purification and the chemical and petroleum industries.In this study, modeling of the volumetric overall mass-transfer coefficient (KGa) is developed for CO2 chemical absorption process by solvents of sodium hydroxide (NaOH), Mono Ethanol Amine (MEA) and 2-Amino-2-Mmethyl-1-Propanol (AMP) in packed columns for five systems with different packings. The presented empirical model for these systems is as a function of the process operating variable parameters. These parameters are liquid volumetric flux, initial concentration of absorption solution, CO2 loadings in solution and mole fraction of CO2 in input gas stream. In this paper, the Eviews software is used for modeling and the obtained experimental results from CO2 absorption experiments by different solvents of NaOH, MEA and AMP with different packings in packed columns. Finally, parameters of predicted model are determined for five systems in this study. Modeling results denotes thatvery good agreement was found between the experimental results and the predicted model for these systems. Also the effects of solvent type and packing type are investigated on performance of CO2 absorption process and mass transfer coefficient.

Due to sensitivity of organic compound in milk to heat and evaporation process, milk usually concentrates in equipments with low residence time and high efficiency such as falling film evaporator. Generally, in this process due to large time delay and disturbances, the tight exact and proper control of product concentration is difficult and important. In this study, to improve the controller performance in falling film evaporator process and elimination of controller offset, a proper structure consists of LMPC and PI controller is proposed. First, a three-effect falling film evaporator is modeled and simulated at dynamic state and then, the proposed control algorithm is applied on process and results of proposed hybrid method are compared with results of conventional PID control. The Simulation results showed that the proposed structure is significantly capable in control of outlet concentration from multi effect falling film evaporators.

Since the pressure of hydrocarbon reservoirs drops due to production, in order to keep the production rate constant or increase enhanced recovery, few methods are used. One of which is gas injection to the reservoir. On the other hand, due to reduction in oil production potential of Aghajari oil field, gas injection is highly required to pressurize and enhance oil recovery. There is a possibility to transfer a part of South Pars Common field produced gas to Aghajari oil district via pipeline to inject it into that reservoir. Produced gases of phases 6, 7 and 8 of South Pars gas reservoir contain impurities such as carbon dioxide (CO2), nitrogen (N2), hydrogen sulfide (H2S) and water vapor (H2O). In this research, the effect of injection of the produced sour gas from phases 6, 7 and 8 of South Pars Complex, on minimum miscibility pressure is investigated by compositional simulation method and using CMG software, considering sour gas composition. The yielded results show that minimum miscibility pressure will increase considerably if both acidic gases, H2S and CO2 are stripped from the injected gas.

Seeded growth on alumina support is one of the most important steps in synthesis of zeolite membrane process that typically perform with frictional contact, immersion and electrophoresis method. In this study, to evaluate and compare these methods, zeolite seeds growed on alpha-alumina support by two methods: Frictional contact and immersion in suspension and then heated using the hydrothermal method at 180oC to prepare zeolite membranes.Finally influence of these methods on the performance of membrane was evaluated by evaporation of xylene isomers. P-xylene due to the smaller molecular size than the two other isomer in the membrane pore size can be too easily absorbed in the zeolite pores and penetrated the surface and this may be a good measure to evaluate synthesis of zeolite membrane. Results showed that the membrane of the immersion method used for seed growth with separation factor 2.66 had best performance than other two membranes.

In this paper, a model has been proposed for hydrogen permeation through palladium/alumina nanocomposite membranes. With regards to H2 /N2 binary gas mixture as feed and also thickness of the palladium nanocomposite layer, among different six stages of hydrogen transport through membrane, three stages; desorption of H2 from palladium surface, diffusion of H2 through metal layer and H2 transport through ceramic porous layer because of their effectiveness in total hydrogen permeation, were considered in the proposed model and their mechanisms were studied with more details. Adjustable variables of model which are effective on hydrogen permeation were determined based on the literature experimental and theoretical works. Finally, a general model for hydrogen flux through palladium/alumina nanocomposite membranes was proposed by considering the resistance of each stage. The proposed model was verified by comparing the model results with literature which were in a good agreement. The obtained results illustrated that at higher temperatures, diffusion through palladium metal layer and at lower temperatures, desorption of hydrogen atoms from palladium surface are controlling stages for hydrogen transport through palladium nanocomposite membranes.

In this paper a new graphical method as “Hydraulic Pinch” has been proposed for optimal design of water distribution network point of view of energy consumption. Name Pinch Technology is the known and familiar name for researchers and scientists active in the field of energy.This technology, first were used for analysis and optimizing of heat exchanger network to reduce energy consumption. Then researcher developed this approach as optimization method in different engineering fields such as hydrogen pinch in order to reduce the required hydrogen in refinery industry, Oxygen Pinch in water treatment field, Water Pinch in water reuse systems and etc.we have developed a new application of pinch method. This approach is used for factories and plants, cities, regions and countries that have considerable resources of water for transfer to consumers.The proposed method determines the minimum number of equipment and lowest necessary energy to the pumping operation. In the first phase innovative pinch method suggests transferring of water from resources to consumers by using the gravity force. Then optimal position and head of required pumps that transfer the remaining water needed to be used in consumers are discovered by using graphical decision maker of Hydraulic Pinch. In this way, the height differences between water resources and consumers are the important key parameters. The investigation conducted in this article, over 80 percent of the water needed by consumers has been transferred by gravity force and the remaining 20 percent have transferred by using the pumping devices that have optimal position and characterization of energy consumption viewpoints. The results of this analysis introduce the Hydraulic Pinch as efficient and suitable method for optimal designing of water distribution network.

Decision on the location of new wells through infill drilling projects is a complex problem that depends on the reservoir rock and fluid properties, well and surface facilities specifications, and economic measures. Various methods to deal with this have been suggested.Direct optimization methods which use the numerical flow simulation are exact. However, these are not practical as they are computationally very extensive. In this study we use a Hybrid Genetic Algorithm optimization technique (HGA) based on the Genetic Algorithm (GA) with helper functions based on the polytope algorithm and the neural network. This hybridization introduces hill-climbing into the stochastic search and makes use of proxies created and calibrated iteratively throughout the run.It is emphasized that the numerical models are constructed based on scarce data, hence the simulation forecasts are uncertain and consequently the deterministic global solution is not achievable.To resolve this we use Fuzzy Inference System (FIS). The output of such system evaluates the selected point given the conditions. For economic evaluation we use Net Present Value (NPV). Therefore, the FIS output is incorporated into the NPV, and a new objective function called Corrected NPV (CNPV) is constructed. We validate the method by optimizing the placement of water injection wells in a section of an oil reservoir located in the west of Iran by maximizing the CNPV. The suggested algorithm was used to find the points for drilling water injection in a reservoir located in the south of Iran. It was observed that the number of simulations required to find the optimal well configurations were reduced significantly by using HGA. Moreover, the positions and the injection rates for four injection wells has been suggested.