Iranian Journal of Chemical Engineering (IJChE)

Abstract The study examines the operational lifespan and catalytic efficiency of the acetylene hydrogenation reactor at Amirkabir Petrochemical Company in Iran, a critical component in industrial olefin production. Acetylene, an undesirable by-product in olefin synthesis, adversely impacts profitability and polymer product quality. To mitigate these effects, the acetylene concentration in the feed stream must be reduced to below 0.5 ppm through catalytic hydrogenation. However, excessive conversion leads to ethane production, thereby reducing ethylene yield. This research uses a modeling approach, supported by industrial data, to investigate the reactor’s behavior under various conditions. A major focus is placed on the reaction kinetics to optimize operational parameters and minimize ethane production, which is less desirable than ethylene. The analysis includes key variables such as temperature, pressure, and the hydrogen-to-hydrocarbon ratio. Moving average method was used to smoothing 78 operational data in this work. Results showed the average absolute selectivity is less than 10%. Additionally, the study evaluates the role of carbon monoxide (CO) as a selective agent that enhances ethylene yield while reducing operational risks. The results showed that the main conversion takes place in the beginning of the reaction (first 1 m of the bed). Additionally, findings indicate that optimal management of these parameters can greatly improve reaction selectivity and the efficiency of the hydrogenation process. The results provide significant insights for refining practices in acetylene hydrogenation, suggesting strategies for improving product quality and operational efficiency in the petrochemical industry.

Abstract This research presents the performance of bladeless wind turbines. It also familiarizes readers with the phenomenon of eddy current, which serves as the foundation for bladeless turbines. In this direction, these kinds of bladeless turbines have been designed, modeled, and simulated. Firstly, a two-dimensional vibrational movement of the cylinder with a natural frequency of 2 Hz was modeled at Re = 51000. Additionally, it was noted that the values of the displacement amplitude, and lift coefficient are -0.1-0.1, and -1.5-1.5  respectively. After that, using 2D simulation, the impacts of two different geometries, horizontal and vertical ellipsoids, on displacement amplitude are examined. Investigations were conducted on important factors such as lift coefficients and displacement amplitude, as well as the vortex flow pattern formed behind these shapes. It was discovered that the vertical ellipsoid shape had the maximum values for the height of the displacement amplitude, and lift coefficient. The most important factor influencing the performance of this type of geometry was examined, namely the dimensionless Reynolds number, which ranges from 15000 to 90000. It was determined that the intended geometry exhibited a larger displacement response as the Reynolds number increased.

Abstract The purpose of this research is CFD modeling of the fluid flow inside an industrial valve in order to discover the areas with high shear stress and to determine the effect of hydrodynamic on the erosion rate. CFD results are compared with the existing experimental data in a valid reference and the model is verified with high accuracy. The impact of the pressure at inlet and the disc angle on the erosion is investigated. By increasing inlet pressure, maximum velocity, turbulence intensity, wall shear stress and particle erosion increased. However, the wall shear stress, turbulence intensity, and particle erosion are clearly reduced as the disc angle decreases. When the disc angle is less than 50o, the range of dependent parameters changes has a small value. Reducing the disc angle or increasing the inlet pressure led to an increase in cavitation. Therefore, to prevent the erosion of the butterfly valve, it is necessary to increase the disc angle or reduce the pressure at inlet. Erosion of the butterfly valve significantly occurred at the front and rear of the disc. Depending on the disc angle, the shear stress of wall for the modified configuration is 10 to 80 times lower than the original butterfly valve. Therefore, it can be stated that the modified geometry can reduce the wall shear stress and consequently the erosive for all the disc angles of the studied butterfly valve.

Abstract In this work, zeolite 13X with porosity structure has been used as an adsorbent for adsorption of CO2 flue gas. The effect of operating conditions including pressure and time on adsorption capacity were investigated. The experiments conditions are constant temperature, the range of pressure 1 - 9 bar and the registration of adsorption capacity with passing of time. Experimental data were adjusted with adsorption isotherm models including two and three parameters isotherm. Also the process was studied in terms of kinetic models and after the implementation of the experimental data with kinetic models, the speed of this process equations were obtained. The best kinetic model for this process was selected first order equation. The results showed that adsorption capacity of 13X is 71.5 mg/g at pressure of 8 bars. Also the result indicate that 13x has high capacity at low pressures. With regard to achieved results for adsorption isotherm modeling, the adsorption isotherm followed of the three-parameter and among three-parameter models, Toth isotherm can be interpreted the process. Also the results of the fixed bed indicate a very high adsorbent selectivity to carbon dioxide adsorption and there was little oxygen and nitrogen adsorption.

Abstract In the present research, three different architectures were investigated to predict the coefficients of the Daubert and Danner equation for calculation of saturated liquid density. The first architecture with 4 network input parameters including critical temperature, critical pressure, critical volume and molecular weight, the second architecture with 6 network input parameters including the ones in the first architecture with acentric factor and compressibility factor. The third architecture contains 12 network input parameters including 6 input parameters of the second architecture and 6 structural functional groups of different hydrocarbons. The three different architectures were trained and tested with the 160 sets of Daubert and Danner coefficients gathered from the literature. The trained neural networks were also applied to 15 un-known hydrocarbons and the outputs (Daubert and Danner coefficients) were used to predict the saturated liquid densities. The calculated liquid densities were compared with the experimental values. The Results indicated that the coefficients obtained from the second architecture produced more precise values for the liquid densities of the 15 selected hydrocarbons.

Abstract Examination of the available ignition delay time data and correlations in the case of methane, butane, heptane, decane, kerosene, Jet-A and ethylene fuels, allowed the derivation and recommendation of standard equations for this property. In this study, a new accurate substance dependent equation for ignition delay time as a function of pressure, number of carbon atoms, mixture equivalence ratio, fuel mole fraction and temperature has been developed to estimate ignition delay time of some hydrocarbon fuels. With the presented model, ignition delay time has been calculated and compared with the data reported in literature. The accuracy of the obtained model has been compared to the mostly used predictive models and the comparison indicated that the proposed correlation provides more accurate results than other models used in the previous works.

Abstract The distillation process remains as the most common method ofseparation in chemical process industries. The energy used from this process accounts for an estimated 3% of the world energy consumption. The Dividing-Wall Column (DWC) for separation of multi-component mixtures has recently become a major concern ofindustries. The design ofDWC is based on Thermally Coupled Distillation System (TCDS) eliminating some of the operational equipment. This paper presents the results of simulation of a DWC by using 3-simple sequence column model based on shortcut method by a commercial chemical Engineering software for purification of1,3 butadiene unit. From the results, it is shown, by using a DWC instead of two conventional sequential column, the heat duties ofboth the condenser and the reboiler are reduced about 28.5% and also desirable purity ofthe key-components for the case ofstudy have been achieved.

Abstract Solid transport phenomena drastically affect rotary drying process. A change in any solid movement variable such as particle hold up or input flow rate results in a significant variation of heat and mass transfer rates. Therefore, in this research dynamic study of these phenomena was conducted both experimentally and theoretically. Several experiments was performed employing an industrial granule dryer. The dryer length and diameter were 5 and 1 m, respectively. In each experiment one of the solid movement variables was changed and the resulting dynamic change on the process was measured. The data was used to estimate the parameters of a dynamic distributed parameter model of the system using dynamic optimization method. The data were also employed to evaluate the model. The model predictions for solid hold up and outlet flow rate were compared with those of the experimental data. The average model error for solid hold up and outlet flow rate were 5.6% and 5.4 %, respectively.

Abstract This article describes kinetic modeling of the reduction of barium sulfate by methane based on experimental data obtained by thermogravimetric technique. The conversion- time data have been interpreted by using the grain model for gas-solid reactions and the effect of catalyst on the kinetic parameters has been elucidated. It was found that
zinc oxide acted as a fairly strong catalyst for the reaction, especially at higher temperatures. For example, at about 950°C the reaction rate constant was increased more than 8 times by using only 2 percent of zinc oxide. Orthogonal collocation method was used for solving coupled partial differential equations of gas-solid reaction. There is a good agreement between the experimental data and results obtained from simulation. This research offers a clean method for barium carbonate production with methane as a reducing agent, decreasing CO2 emission significantly. Also, a new process for converting sulfur dioxide to elemental sulfur by a cyclic process involving barium sulfide and barium sulfate has been proposed.

Abstract The separation of hydrocarbon mixture using facilitated transport membrane (an immobilized liquid membrane type) was investigated. A 50:50 (vol. %) propylene- propane mixture was used as a sample of the hydrocarbon mixture. The effect of trans-membrane pressure (in the range of 50-120 kPa) and carrier concentration (in the range of 0-20 wt.% AgNO 3 ) on separation performance was studied experimentally and mathematically. It was observed that increasing trans-membrane pressure and carrier concentration supports the separation factor and propylene permeation rate. On the other hand, increasing trans-membrane pressure and decreasing carrier concentration supports the propane permeation rate. Hence, the greater the trans-membrane pressure and carrier concentration, the more purified the product obtained. It was found that at trans-membrane pressure of 120kPa and carrier concentration of 20wt. %, the highest separation factor (270) and propylene permeation rate (7*10-7 mol/s) was obtained. The average deviation between the experimental and modeling results was found to be 5.3% for propylene permeation rate and 0.03% for propane permeation rate.

Abstract In this work, the effects of air stream direction in the channels of indirect evaporative cooler (IEC) on system performance have been investigated. In addition, the dependence of system performance on outdoor air temperature and relative humidity has been studied to determine the allowable conditions for proper operation of the system, with respect to thermal comfort criteria. For this; the different types of IECs were investigated using the CFD technique. Several codes were defined in MATLAB for modeling the parallel flow, counter flow and cross flow layout. The CFD program was validated against theoretical data from the literature and good agreement between the prediction and measurement was achieved. The calculated results show that when the air relative humidity is lower than 70%, the system can prepare a good indoor condition even at 50oC, and a higher performance is achieved by using the IEC with counter current configuration. The results showed that IECs can be successfully used in hot and humid climates to fulfill the indoor thermal comfort conditions.

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 n this paper, a mathematical model has been derived to predict the granulation time of anaerobic sludge in UASB reactors. In the proposed model, some physical, chemical and biological parameters affecting the granulation phenomena have been considered. To validate the model, 12 pilot-scale experiments in 4 UASB reactors are carried out and the results are discussed here. The reactors are started up at different environmental conditions and the granulation time in each experiment is determined. The results show that the model is able to explain different mechanisms involved in the granulation process.