فهرست مطالب احد قائمی

In this study, we developed artificial neural network-based model for prediction of equilibrium solubility of carbon dioxide in the amine solvent system of (triethanolamine + piperazine + water) for the purpose of carbon dioxide uptake. In the MLP model, the solubility data (CO2 loading in the amine solution) were investigated as functions of CO2 partial pressure, system temperature, and amine composition. The Levenberg–Marquardt back-propagation (LMP) algorithm was used to predict the partial pressure of carbon dioxide. The final ratio of training, validation, and test datasets was approximately 70:15:15. The optimum multilayer perceptron (MLP) structure in Levenberg-Marquardt algorithm for CO2 partial pressure is created with 20 neurons in the first hidden layer and 10 neurons in the second hidden layer. There was a 0.99546 correlation coefficient between the experimental results and the artificial neural network (ANN) calculations, demonstrating excellent compatibility between them. The best validation performance was 0.0043497 from epoch 13. In general, the results show that the applied model can provide an accurate prediction of partial pressure or solubility for different operating conditions.

In the present study, carbon dioxide mass transfer flux in the reactive absorption process was modeled by three solutions of methyldiethanolamine (MDEA), monoethanolamine (MEA), and piperazine (PZ) using the film theory model and all governing equations solved simultaneously. The effects of all components' concentration during film and mass transfer flux with and without film displacement were investigated and predicted values were compared with experimental data of the carbon dioxide absorption process in the desired solutions. The influence of various dimensionless parameters including film and loading parameters as well as the effects of reaction, diffusion, film velocity, and eddy on mass transfer in the proposed model has been studied. The deviations were calculated from the experimental data for the mass transfer flux by calculating the average relative deviation (ARD). The values of ARD were obtained at about 5.30%, 8.24%, and 6.56% for PZ, MEA, and MDEA solutions respectively. Moreover, based on the film displacement, the mass transfer flux was affected and the average relative deviations decreased. For PZ solution, 0.1% and for MEA and MDEA solutions, 0.6% and 1.1% error reductions were observed, respectively. Furthermore, the results show that the effects of reaction and diffusion on the mass transfer flux are on average more than 35% than the effects of film velocity and eddy influence.

Cu(II) is one of the pollutants that exist in the produced wastewater by many industries. According to the World Health Organization (WHO), its concentration should be less than 2 mg/L. In this study, Phosphorus Slag (PS) and Ground Granulated Blast-Furnace Slag (GGBFS) as industrial wastes with the properties of abundant and low cost are used to remove Cu(II). The effects of the shaker rotation rate, initial concentration of Cu(II), and amount of adsorbent on the adsorption process are investigated. The adsorption capacity was maximized at a shaking rate of 150 rpm, initial concentration of 50 mg/L, 0.2 g GGBFS per 0.03 liter, and 0.5 g PS per 0.03 liter. At various temperatures, the values of thermodynamic parameters were calculated by measuring the equilibrium data. The results showed that the adsorption process was exothermic using both GGBFS and PS adsorbents. The experimental data of Cu(II) adsorption by GGBFS and PS was fitted well by Langmuir and Freundlich isotherm models, respectively. The maximum adsorption capacity was obtained 156.30 and 151.52 mg/g for GGBFS and PS, respectively. Also, the kinetic modeling indicated that the adsorption process is achieved to the equilibrium state using both adsorbents at less than 5 min.

In this study, gas phase holdup in a gas-liquid bubble column reactor was experimentally studied. To conduct experiments, a bubble column with a height of 54 cm and a diameter of 10.4 cm was applied. The studied systems include water-air, Gasoline-air, and Behran oil-air. Experiments were carried out in the range of 400-50 rpm agitator. Based on the Buckingham π theorem, a semi-experimental model for gas phase holdup was presented. The results showed that with increasing viscosity from 0.001 to 0.0136 gas phase holdup loss due to high adhesion of bubbles at high viscosity and also the increase of bubble size at the output from the distributor decreases from 0.41 to 0.333. Among the selected systems, the gas phase holdup of the gas-air system was maximized. The results also showed that in materials with low viscosity, the gas phase reduction was due to the formation of liquid vortex movement and air canalization by the agitator. The best agitator speed to increase the gas phase holdup at water and oil are 150 and 400 rpm, respectively.

Hyperlinked polymers (HCPs) are one of a variety of microporous polymers with a pore size of about nm, which is very important for the capture and storage of carbon dioxide. In this work, benzene-based HCP adsorbents synthesized on the basis of the Friedl-Kraft reaction have been investigated experimentally for the capture of carbon dioxide. The surface-response method was used to optimize process parameters to increase the carbon dioxide absorption capacity. The pressure, temperature, Kraselinker to benzene ratio, and synthesis time as process parameters and absorption capacity are also considered as the response of this method. The optimal values of pressure, temperature, Kraselinker to benzene ratio, and synthesis time, which maximize absorption capacity, are 5.857 bar, 21.331 ° C, 2.189, and 14.357 h, respectively. According to the optimum condition, the absorption capacity of carbon dioxide was calculated as 244.43 mg/g of adsorbent.

In the present study, active carbon and active alumina adsorbents were improved using sodium hydroxide and potassium hydroxide solutions in order to increase the absorption of carbon dioxide. The effect of different operating parameters including the amount of adsorbent, concentration of hydroxide solution, temperature, and pressure on the adsorption process were investigated. The results of the adsorption experiments showed that the carbon dioxide absorption capacity increases by decreasing the temperature and increasing the pressure. The optimum conditions were 20 ° C, 6 bar, 2 g of adsorbent with 30% weight sodium hydroxide and potassium hydroxide. The maximum carbon dioxide absorption capacity for activated carbon modified with sodium hydroxide and potassium hydroxide solutions were 104.42 mg/g and 84.8 mg/g, respectively, which indicates 83 and 48 percent increase for modified activated carbon in comparison with unmodified ones. The carbon dioxide absorption capacity for activated alumina modified with sodium hydroxide and potassium hydroxide solutions were 146.70 and 130.84 mg/g, respectively, which indicates 47 and 65 percent increase for modified activated carbon in comparison with unmodified ones. As a result, generally, the modified activated alumina adsorbent revealed higher carbon dioxide absorption capacity carbon in comparison with the modified activated carbon.

According to the greenhouse gas emission and the importance of CO2 capture as one of the most important greenhouse gases with extreme emission, nanofluids have been suggested and studied as fluids with higher mass transfer coefficients in order to enhance gas absorption. In this study, water-Al(OH)3 nanofluid which is made by dispersing hydrophilic nanoparticles capable of enhancing nanofluids stability are used and investigated by enhancing the nanoparticles' solid loading. This enhancement increases and decreases mass transfer which is assumed to be a reason for Brownian motion, Shuttle effect, and hydrodynamic effect as enhancers and viscous effects as the reducer. Selecting the optimum values by considering nanoparticles solid loadings effect on enhancement’s case study, pressure, mixing index and solid loading’s effects have been studied in detail and results represent the negative effect of pressure and enhancing and then reducing the effect of mixing index and solid loading on absorption as the maximum enhancement factor reaches the 39.012 value.

The chemical absorption technology is widely used in the industry to remove carbon dioxide post-combustion. It is necessary to develop and identify optimal chemical solutions to absorb more and reduce the absorption energy. The aqueous solutions of alkali metal hydroxides are considered by the researchers due to their low energy requirement and their compatibility with the environment in comparison with amine absorbers. In this research, hydroxide solutions, especially potassium hydroxide, have been used to absorb carbon dioxide. In absorption experiments, the effect of stirring and temperature on the absorption of carbon dioxide by aqueous hydroxide potassium in a laboratory-scale reactor has been studied. The results showed that with increasing stirring of the mixer from 50rpm to 150 rpm, the loading, absorption, and mass transfer flux of carbon dioxide increased 33%, 32%, and 36 respectively but the increase in the agitator over this amount would not have an effect on the absorption rate. The temperature increase was carried out in the range of 25-65°C with a 6 bar pressure, a concentration of 1.5 mol/L, and a stirring speed of 150 rpm. It was observed that increasing the temperature to half the absorption process increased the loading, absorption rate, and absorption flux of carbon dioxide, but the equilibrium parameters decreased slightly with increasing temperature. In fact, with temperature increasing from 22°C to 65°C, the equilibrium loading, adsorption rate and absorption flux of carbon dioxide decreased 15%, 2.4%, and 13%, respectively.

The extraction of uranium from a solid waste by using the resin ion exchange process is the subject of this study. For this purpose, the solid waste of the fluorination reactor was selected. In order to uranium recovery from this solid waste, sulfuric acid was used as a solvent and IRA-910 amberite resin was used for adsorption by ion exchange process. The results showed that uranium was adsorbed by this resin with 80-90 % efficiency. The optimum mass of resin for adsorption from sulfuric acid medium with initial concentrations of 180, 270 and 450 mg / l uranium were 0.15, 0.3 and 0.5 g, respectively. The effect of uranium initial concentration, contact time and temperature on adsorption was investigated. The optimum contact time was 2 hours. The thermodynamic parameters of enthalpy change, entropy, and Gibbs energy change for the initial uranium concentration of 370 mg / l were calculated and it was determined that this process is endothermic. Experimental data for the initial uranium concentration of 185 mg / l and the sulfuric acid concentration of 0.09 and 0.02 M are in excellent agreement with the Freundlich isotherm absorption. The kinetic parameters of uranium uptake on IRA-910 for Lagergren and pseudo second order adsorption kinetics were calculated.

In this research, the separation of silica particles was experimentally investigated using a cyclonic separator with two feed inlets and a rotating body. Experimental experiments were performed using a laboratory-scale cyclone. In the experiments, the effect of operating parameters including particle size ranging from 15 to 40 microns, air velocity of 30 to 70 cubic meters, and cyclone body velocity from zero to 1900 rpm on cyclone efficiency were evaluated. Experimental results showed that the particles grew by about 1 to 2%, an increase of about 3% by 5% and an increase in the body velocity of about 10% by 13% resulted in improved cyclone efficiency. The results also showed that the body time in the direction of the flow of the input stream would reduce about 48% of the cyclone efficiency. The cyclone pressure drop during the period indicated that this number is more in a rotary state than the steady state of the body, but the uniform distribution of pressure does not cause the effect of the pressure drop on the tangible efficiency. The experimental results also show that increasing the discharge and the speed of the cyclone body increases the tangential velocity and, as a result, increases the centrifugal force, which results in increased cyclone efficiency.

In this research, the process of desalting and water removal from crude oil by ultrasonic laboratory scale has been investigated. The effect of main parameters including ultrasonic radiation parameters, the input power of radiation, and radiation time, as well as functional parameters such as temperature and injection rate of emulsion breaker, have been investigated on the removal efficiency of salt and water. The results showed that using ultrasonic waves, the amount of Ahwaz crude oil decreased by 40 ppm emulsion breaker from 471 mg/L to 76.18 mg / l, and water content decreased from 9.19% to 1.1%. The rate of desalinization was 83.38% and the rate of dehydration was 88.03%. The amount of Ahwaz 4 crude oil was reduced by injection of 30 ppm emulsion breaker from 353 mg/L to 49.2 mg/L, and water content decreased from 11.36% to 2%, with a desalting rate of 86.06% and a water abstraction of 82.4% have been. These results were obtained at the highest test temperature of 80 °C and 10 KHz, which, with a near approximation to unit efficiency, reduced the use of the demulsifier. In optimal operating conditions, the results show that ultrasonic radiation can be effective in reducing the desalination of crude oil by reducing the amount of emulsion breaker and increasing process efficiency. Also, the results of the research show that the combination method of ultrasound and emulsion breaker is the best way to use emulsion breaker.

In this research, zeolite and active alumina adsorbents were modified to increase the absorption of carbon dioxide using piperazine solution. The effect of different operating conditions including temperature, pressure, amount of adsorbent, particle size, and concentration of piperazine solution on the adsorption process were investigated. The results of the adsorption experiments showed that, with increasing pressure and decreasing temperature, the adsorption rate increased, and the highest amount of carbon dioxide absorption was at 25 ° C, 8 bar, 1 g of adsorbent, 200 micron particles, and 2% concentration weight is piperazine. Absorption capacity for active alumina increased from 166.516 to 222 mg/g, absorbent for zeolite 13X from 194.844 to 244.084 mg/g. In general, the modified 13X zeolite adsorbent has a higher absorbance compared to modified activated alumina, but it also increases the level of absorption of active alumina. Thus, according to the results of this study, modified adsorbents with piperazine have a good effect on carbon dioxide absorption. At high temperatures, it also increases the absorption rate of the absorbent material.

Praseodymium (Pr) and neodymium (Nd) are among the rare earth elements that have received significant attention due to their many applications. In this research, the separation of Pr and Nd from simulated NdFeB magnet leaching solutions with Cyanex 272/kerosene was modeled and optimized. Response surface methodology (RSM) based on the central composite design (CCD) was applied to fit the polynomial equation to the experimental data. The effects of variables such as concentration of Cyanex 272 (0.23-0.57 mol.L-1), pH (2.0-5.0) and O/A (1-3) on the extraction efficiency and separation factor of Pr and Nd were studied. The order of the effect of the variables on the extraction efficiency was opposite to the effect of the variables on the separation factor. The numerical optimization was performed to maximize the operational selectivity of the studied system. The calculated results for Nd and Pr extraction percentages were 71.7% and 62.5%, respectively and the separation factor was 1.54. Also, it was found the stripping of Pr and Nd ions from the loaded organic phase can be effectively conducted under the 0.1 mol/L hydrochloric acid solution within a contact time of 5 min conditions. The studied system showed an efficient performance in both extraction and striping processes of Pr and Nd at investigated condition.

In this research, the adsorption potential of carbon dioxide and hydrogen sulfide storage in metal organic frameworks has been studied and modeled. Studying four different type of micro porous coordination polymer adsorbents metal organic frameworks including MOF-2 (Zn2 (BDC)2), MOF-74 (Zn2 (DHBDC)), IRMOF-1 (Zn4O (BDC)3) and MOF-177 (Zn4O (BTB)2) showed that the adsorbent have different structure caused different performance in gases adsorption. For adsorption isotherm modeling of these adsorbents used two parameters isotherm models. For calculation parameters of the models was used nonlinear regression technique. The results showed that the models have good agreements with experimental data. Hill model has high accuracy to compare with other models. The parameter values of D-R model for all adsorbents showed that the processes were physical adsorption and IRMOF-1 for H2S and MOF-74 and MOF-2 for CO2 adsorption were suitable.

In this research, a film model, considering forward mixing for the prediction of mass transfer behavior of a pulsed sieve-plate extraction column was applied.  For modeling the column hydrodynamic, a dynamic droplet population balance model (DPBM) has been used. The model equations, including disperse phase droplet and partial differential equations, were solved simultaneously using central differential and method of lines methods. The model was studied with water-ethyl acetate as a working system. The mean drop size and its distribution (in both volume and number) were calculated by the model. The model error for mean drop size is 0.65 % whereas the error of the correlation model for the same data is 8.36 %. The exact modeling of the column applying droplet size variations by droplet mass balance during the extraction column showed that the model has good agreement with experimental data.

In this study, the chemical adsorption modeling of CO2 in the fixed bed column is determined. In the adsorbent modeling, the granules are assumed to be spherical, and by writing the mass balance around a radial element, a partial differential equation has obtained that shows the variation in adsorption versus the direction of radius and time. By applying the boundary conditions and initial condition in terms of the physics of the problem, this equation can be solved, but due to the complexity of its analytical solution, the equations were solved using a combination of the method of lines and finite difference methods. For the modeling of the fixed bed column, the column is aligned along with the height, and by writing the mass balance around it, the partial differential equation is obtained. In order to ensure the modeling process, the model has been verified using experimental data and numerical modeling of the Kelvin Odafe Yoro model. Finally, parametric studies have been done on the chemical adsorption of CO2 in the fixed bed column. The amount of R2 in the CO2 breakthrough curves on polyaspartamide and in the experimental and simulated equilibrium amount of CO2 adsorbed by polyaspartamide at the time is 0.99 and RMSE is approximately 10% for them.

In this research, the biosorption process of copper metal from industrial wastewater by Rhizopus Arrhizus has been modeled in a fixed bed column. The performances of the three isotherms of Langmuir, Freundlich, and BET were compared to calculate the adsorption rate. Based on the modeling results, the Freundlich model with a correlation coefficient of 0.974 showed better agreement with the experimental results than the other models. The highest agreement of Freundlich model with experimental data was obtained at k=0.991 and n= 0.8551. Then, the effect of the selected model parameters on the adsorption rate was investigated, and it was found that at a constant Freundlich coefficient, an increase in the power of the model enhances the available adsorption capacity for low solute concentrations. The effects of operating conditions in the column include volume flow, column diameter, column length, initial concentration, and adsorbent density on the adsorption rate were also investigated. In general, it can be stated that the modeling of biological processes for metal removal is one of the important tools in understanding the behavior of these processes with the least cost, and also the performance of the process can be evaluated at different operating conditions.

Carbon dioxide gas is one of the main environmental pollutants that can cause irreparable damage by changing the climate, so solving this problem requires serious attention. Chemical absorption of CO2 with alkanoamine aqueous solutions is currently the most common commercial method of high-efficiency separation in the industry. Among the various methods of removing carbon dioxide from flue gases, the monoethanolamine (MEA) aqueous solvent absorption process has been the most important option for industrial applications in recent years. In this research, MEA solvent has been used to evaluate the amount of CO2 absorption. The experimental range of the studied parameters includes temperature of 20-60 C, pressure of 3.5-9.5 bar and solvent concentration of 2.5-8.5% w. Loading and CO2 absorption percent in MEA aqueous solution were obtained in the range of 0.70-2.615 and 17.81-48.65%, respectively. To analyze the results, the quadratic polynomial model using the response surface method (RSM) has been used. Numerical optimization has also been used to find the maximum loading and absorption percent under optimal conditions. Under optimal conditions, the maximum loading and absorption percent are estimated to be 0.552 and 44.17%, respectively.

Uranium is the most important material in the nuclear fuel cycle that produces in the various stages of uranium production and processing research and after-use in reactors, as well as laboratory researches as uranium wastage. The uranium in these wastages is valuable and may cause radiation problems if they enter the environment, so their separation is essential. The solvent extraction method is one of the most important separation methods in the nuclear industry that produced uranium components from wastages is recovered using this method in the current study. After identifying the presented components in the wastage, the amount of each component was determined by using Inductively Coupled Spectrometry (ICP) analysis and finally the type of present uranium compound in the wastage was specified. According to the desired compound, the extraction experiments were performed with two different solvents of trioctylamine (TOA) and di-2-ethylhexyl phosphoric acid (D2EHPA) which the extraction percentages were achieved 96.12% and 99.01%, respectively. Also, the effects of extractant type, extraction temperature, acid concentration, extractant concentration, initial uranium concentration, diluent type, aqueous to organic phase ratio, phase mixing time on extraction percentage as well as the effect of various rinses on the reverse process were investigated.

In this work, a film model has been developed to describe unsteady state simultaneous absorption of two gases. Film modeling of reactive absorption results in initial boundary-value problem. The analytical solution applied in this work is a combination of the superposition principles and the separation of variables methods. The concentration equations obtained in the model contain two independent variables of time and film width. Therefore, solving the model gives component concentrations at any time or film length. In addition, the partial differential equations were solved numerically. The experimental data were obtained using laboratory packed column. The model results were validated using experimental data. A comparison between the model results and experimental data indicates that the model has good agreement with experimental data.

Phenol presence and its derivatives in water and waste water on human health and the environment is one the major concerns. Because of the toxicity of phenol and also because of the presence of even low concentrations in natural resources, water disinfection and oxidation processes can lead to the formation of additional components. This material is one of the most common organic pollutants in water. In this research, adsorption of phenol from wastewater by sawdust was simulated using intelligent techniques. Intelligent techniques including multi-layer Perceptron, radial basis functions network and support vector regression were used. To design the network structure as well as the training and testing of 125 sets of experimental data is used. Performance evaluation criteria and stop network consists of % AARE and, which is used for all three models. All models compared results showed that the support vector regression with 0.5132 and 0.979, respectively, for %AARE and  is the best model. All models are better results than the quadratic polynomial model showed. Models showed good agreement with experimental data. The optimum conditions for the removal of phenol were 127.6 mg/l of initial phenol concentration, 0.84 g/l of adsorbent dose, natural pH value of 3.62 and 146.9 min of contact time, under these conditions the maximum removal efficiency was 91.23%.

  In this research, the modeling and simulation of hydrogenation reactor of Amirkabir petrochemical acetylene unit was carried out. The reaction processes are elementary and in this process acetylene was converted to ethylene. The modeling process was happed with introducing mathematical equations of mass transfer. The set of process equations were solved simultaneously using method of lines and finite difference techniques. The results showed that simulation with 80 elements has minimum deviation with experimental data. The results showed that the simulation result has good agreement with experimental data. The maximum relative error of this mathematical model is well under about 1%. After model validation, various variable profiles along the reactor are discussed. Then, the effects of effective parameters such as inlet temperature, total inlet mass flow rate and CO flow rate are investigated in detail. The optimum value of carbon monoxide to get highest selectivity is 700 ppm. Also the results showed that the process has good selectivity at temperature 77oC.