IRANIAN JOURNAL OF CHEMICAL ENGINEERING
Year:2013 | Volume:10 | Issue:4|Papers Count:7

In this study, the Langmuir adsorption isotherm has been coupled with activity coefficient models for prediction of surface tension of single and mixed electrolyte solutions. Various activity models such as Meissner, Pitzer and extended UNIQUAC have been used and coupled with Langmuir adsorption isotherm. The model parameters were determined through mathematical optimization using experimental surface tension data of single electrolyte solutions. Absolute average deviation was used as objective function in optimization procedure. The results showed that in the case of single electrolyte solutions different activity coefficient models have similar capability while in the case of mixed electrolyte solutions, extended UNIQUAC model gives better results.

A series of experiments were carried out by mixture of methanol and water as feed of the methanol to propylene (MTP) process in temperature range of 623-823 K. The HZSM5 catalyst with the Si/Al ratio of 200 was applied for carrying out the experiments. A novel lumped kinetic scheme was proposed for methanol to propylene (MTP) process. The reactor was mathematically modeled by assumptions of being isothermal, fixed bed, plug flow and the hybrid genetic algorithm was applied for estimating the kinetic parameters. The temperature dependency of the kinetic parameters was determined, using the modified Arrhenius relation. A good agreement was observed between the experimental and the calculated data. Effect of temperature on propylene and ethylene selectivity was investigated. It was found that the propylene selectivity increases with temperature until 773.15 K, but after that it decreases.

In this work, recovery of uranium from industrial waste was investigated experimentally using solvent extraction technique. Di 2-ethyl hexyl phosphoric acid (D2EHPA), tri-noctyl phosphine oxide (TOPO) and their synergetic mixture was used as extractant in the experiments. Nitric acid solution was selected the best medium for extraction of uranium from the industrial waste. The extraction process has been investigated as a function of extractant concentration, diluents type, nitride acid pH, contact time, initial uranium concentration and temperature. The experiments were performed in batch mode. Kerosene was selected as the best diluent for the extractants. In the experiments it was found that, high temperature is beneficial for TOPO or D2EHPA extraction but low temperature is profitable for their synergistic effect. The results indicate that the extraction rate for uranium was controlled by diffusion. The best stripping agent for TOPO 0.05M or D2EHPA 0.15M and their mixture were Na2CO3 2M, by 96.2%, 54.3% and 57% uranium recovery respectively. McCabe curve showed that single theoretical stage is sufficient for uranium extraction more than 95 percent.

In this paper, the thermal properties including molar heat capacity, CP, thermal conductivity, λ, and thermal diffusivity, αD, of the pure physical solvents sulfolane (SFL), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), ethylene glycol (ETG), choloroform (CCL3H), acetonitrile (CH3CN), and pure chemical solvents monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP) which all are extensively used in natural gas refinery processes were measured at temperatures ranging from (303.15 to 353.15) K and atmospheric pressure. All experimental measurements were carried out by using a PSL Systemtechnik instrument in which transient hot-wire method was employed to measure transport properties, λ and αD. All obtained data were correlated by using empirical linear temperature function with a very good correlation coefficient, better than R2=0.99. Among the solvents tested in this paper, except for TEA, the thermal diffusivity decreased by increasing temperature and also except for TEA and ETG, thermal conductivity decreased with temperature.

In this study, we suggest proceeding to an experimental study concerning the synthesis of new organo metallic product xanthate (KIBX) by intermittent method and their use in the processes of sulphides flotation.The adsorption of potassium isobutyl xanthate (KIBX 3⋅10-3M) on sphalerite has been studied using electrochemical potential, FTIR technique and SEM. Non activated minerals and minerals activated with copper sulfate (10-4 M) and copper nitrate (10-4 M) have been investigated at pH 7.5. Surface species have been identified by FTIR and correlated with SEM. After copper sulfate activation, copper xanthate exists on all of the minerals studied.Neutral pH is the most suitable for potassium isobutyl xanthate adsorption on sphalerite.

In this work, five different thermodynamic models for correlating the fugacity of water and Tetrahydrofuran (THF) in liquid phase in equilibrium with hydrogen hydrate phase, based on the van der Waals-Platteeuw (vdW-P) statistical thermodynamic model are used and the equilibrium pressures of hydrogen hydrate at different temperatures are calculated. The dissociation pressure of binary hydrogen hydrates is determined by using the Zele-Lee-Holder cavity distortion model. The studied models in liquid phase are NRTL excess Gibbs energy, Peng-Robinson (PR) equation of state (PR EOS), Peng-Robinson-Steryjek-Vera EOS with the Wong-Sandler mixing rule (PRSV-WS), Dashtizadeh EOS (DPTG), and Ghotbi-Vera Simple SAFT (GV-SSAFT) EOS. The results show that the GV-SSAFT model correlates more accurately the experimental dissociation pressure of binary hydrogen hydrate. Additionally, hydrogen storage capacity of binary hydrogen hydrates is calculated.

Essential oil of Valeriana officinialis L. cultivated in Iran was extracted using steam distillation technique and then analyzed by gas chromatography and gas chromatography-mass spectrometry. Optimization of extraction of essential oil was performed using this technique. The extraction yield results for steam flow rates of 4, 7 and 9 L/min for a packed bed of 100 gram of plant were found to be 0.60, 0.52 and 0.47 percent, respectively. For bed heights of 35, 47.5 and 65 cm and a steam flow rate of 4 L/min the extraction yield was found to be 0.60, 0.36 and 0.24 percent. The results of multistage column for a total of 100 g packed bed and 4 L/min steam flow rate were 0.65, 0.65 and 0.6 for three, two and one stage distillation column, respectively. The oil yield was increased from 0.6 for standard roots to 0.7 for crushing roots.