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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Gas Processing Journal
- نوع مقاله: Journal Article
- کلمات کلیدی: Tetrahydrofuran Hydrate,Differential Scanning Calorimetry,Formation Heat,Phase Change Temperature,Specific Heat Capacity
- چکیده:
- چکیده انگلیسی: In this study, a differential scanning calorimetry (DSC) has been used to characterize tetrahydrofuran (THF) hydrate formation with and without the presence of sodium and chloride salts. The thermal properties including the heat of formation, phase change temperature and specific heat capacity of THF hydrate formation have been determined. When salts are present, THF hydrate is inhibited, so that the phase change temperature shifts to a lower temperature, a broadening of the DSC peak can be seen and the height of the peak and the heat of formation decreases. Because the heat capacity depends on the heat of formation, it reduces when salt is present. The results show that the sodium salt solutions have exhibited the best performance on delaying nucleation of hydrate in order of Na2SO3 > NaF > NaCl, while chloride salt solutions, especially CaCl2, have demonstrated that can reduce the heat of formation to around 65% compared to that of without salt.
- انتشار مقاله: 10-08-1397
- نویسندگان: Parisa Naeiji,Farshad Varaminian
- مشاهده
- جایگاه : پژوهشی
- مجله: Gas Processing Journal
- نوع مقاله: Journal Article
- کلمات کلیدی: Methane,Gas Hydrate,Ethane,Formation Kinetics,Sodium Dodecyl Sulphate
- چکیده:
- چکیده انگلیسی: In this study, the effects of sodium dodecyl sulphate (SDS) on gas hydrate formation kinetics of methane and ethane mixture has been investigated experimentally and also the thermodynamic natural path has been used for modeling of the hydrate formation rate in a constant volume process. Different mole fractions of methane 0.1, 0.2, 0.3, 0.5, 0.68 and 0.8 have been studied. All experiments have been carried out at a constant temperature of 277.15 K, approximately initial pressure of 3.6 MPa and a stirrer speed of 800 rpm, with and without the presence of SDS with concentration of 500 ppm. The results show that SDS increases the hydrate formation rate by means of decreasing the gas liquid surface tension, so that the initial rate of hydrate formation and the model kinetic parameter of Ar/RT are increased about 3 and 1.2 times, respectively. Besides, SDS transforms two-step process of methane-ethane hydrate formation to one-step of that. This surfactant also promotes the hydrate growth in the liquid phase and increases the moles of gas consumed, so that the highest amount of gas consumption for hydrate formation belongs to the mixture with 0.3 mole fraction of methane.
- انتشار مقاله: 23-08-1395
- نویسندگان: Parisa Naeiji,Farshad Varaminian
- مشاهده
- جایگاه : پژوهشی
- مجله: Gas Processing Journal
- نوع مقاله: Journal Article
- کلمات کلیدی: Stability,Methane,Gas Hydrate,Ethane,Structural Changes
- چکیده:
- چکیده انگلیسی: Abstract: Â In this study, the change in the crystalline structure of gas hydrate was predicted for ternary mixture of methane-ethane-water. For this purpose, the tangent plane distance (TPD) minimization method was used. First, the calculations were performed for the binary mixtures of methane-water and ethane-water as the gas and liquid phases. The results show that for a binary mixture of these components in the gas phase, at the temperatures of 274 K and 275 K, for a wide range of pressure, the phase remains stable however, the liquid phase is unstable and it splits into two or more new phases. The method was used for any possible new phases and the stable new phases determined by TPD minimization. By using this method for the ternary mixture at 20 different points (pressure and composition) at the temperature of 277.6 K, the results for stable phases are found to be consistent with the literature further, a structural change from sI to sII is observed at methane mole fraction of 0.74, and another structural change from sII to sI is observed at methane mole fraction of 0.99 at 277.6 K. This method can be used for the stability analysis of more points to predict the boundary of the phase diagram and stable zone for different phases. In this study, the genetic algorithm was used for minimization of TPD function.Â
- انتشار مقاله: 26-03-1395
- نویسندگان: Farshad Varaminian,Hadi Behjati Rad
- مشاهده
- جایگاه : پژوهشی
- مجله: Gas Processing Journal
- نوع مقاله: Journal Article
- کلمات کلیدی: Gas Hydrate,Kinetics of Formation,Ethane Hydrate,SDS Aqueous Solution,Chemical Affinity
- چکیده:
- چکیده انگلیسی: Â Abstract: In this work, the kinetics of ethane hydrate formation has been studied experimentally and a kinetic model based on chemical affinity has been described for predicting the hydrate growth process in the stirred batch reactor at a constant volume. The experiments were done with both pure water and aqueous solution of sodium dodecyl sulfate (SDS). The effect of SDS on formation kinetics has been investigated in concentrations: 300, 500 and 1000 PPM at different temperatures: 273.15 , 274.15 , 275 .15 and 276 .15 K. Experimental results showed the use of SDS decreases surface tension between the liquid and gas, then the ethane hydrate formation rate is increased, especially in SDS concentration of 500 PPM. The parameters of the model, Ar/RT and tK, were optimized for each experiment. The parameter Ar/RT was obtained a constant value for ethane gas. Acceptable agreement between the experimental and predicted data was generally found, and this model can sufficiently predict the formation pressure. Â Keywords: Gas Hydrate, Kinetics of Formation, Ethane Hydrate, SDS Aqueous Solution, Chemical Affinity
- انتشار مقاله: 26-03-1395
- نویسندگان: Maryam Karamoddin,Farshad Varaminian,Maryam Daraee
- مشاهده
- جایگاه : پژوهشی
- مجله: Gas Processing Journal
- نوع مقاله: Journal Article
- کلمات کلیدی: Gas Hydrate,SH,sI,Formation Kinetics
- چکیده:
- چکیده انگلیسی: This paper investigates the kinetics of structure H (sH) formation kinetics above and below the structure I (sI) formation equilibrium curve at temperatures of between 2°C and 6°C. Methane was used as a help gas and methylcyclohexane (MCH) was used as sH former. It was concluded that in the points above the sI formation equilibrium curve, at the first, the sI forms, and then converts to sH because of the low solubility of MCH in water. In the points under the sI equilibrium curve, at the first sH forms after a long induction time. The study also show the effect of the addition of hydroxymethylcellulose (in three concentrations of 0.05, 0.1 and 0.15 Wt%) on sH hydrate formation kinetics. With this additive, it was observed that the rate of sH formation increases.
- انتشار مقاله: 26-03-1395
- نویسندگان: Mohsen Vafaii Sefti,Behnaz Parvizi,Farshad Varaminian
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Particle Science & Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Surfactant,Nanocomposite,morphology,Conductive polymer,chemical structure
- چکیده:
- چکیده انگلیسی: Polyaniline (PANI) nanocomposite has been successfully prepared in aqueous
media by the chemical polymerization of aniline with ammonium peroxydisulphate
as an initiator in the presence of a steric stabilizer such as sodium dodecylbenzenesulfonate
(DBSNa), Poly(vinyl pyrrolidone) (PVP), poly(vinyl alcohol)
(PVA), poly(ethylene glycol) (PEG) and hydroxypropylcellulose (HPC). The
chemical structure, morphology, thermal stability and thermal degradation of the
synthesized PANI nanocomposite were studied by different techniques such as
fourier transform infrared spectroscopy (FTIR), scanning electron microscope
(SEM), X-ray diffraction (XRD) and four-probe. The results revealed that surfactant
dispersed uniformly in polyanilin matrix and made a nanocomposite with
average crystallite size about 74 nm.- انتشار مقاله: 19-12-1393
- نویسندگان: Mohsen Mehdipourghazi,Millad Hallajighomi,Farshad Varaminian
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Chemistry and Chemical Engineering
- نوع مقاله: Journal Article
- کلمات کلیدی: Methane,Gas Hydrate,Affinity,Decomposition kinetics
- چکیده:
- چکیده انگلیسی: In this work, experimental kinetics data of methane hydrate decomposition at temperatures ranging from 272.15 to 276.15 K and at pressures ranging from 10 to 30 bars were modeled by using chemical affinity. This model proposed a macroscopic model which is independent of any intermediate mechanism like heat or mass transfer. The results show there is good agreement with experimental data. Also the two parameters of model were calculated and correlation coefficient of model is higher than 0.9.
- انتشار مقاله: 03-03-1387
- نویسندگان: Farshad Varaminian,Zohreh Abbasi Nia
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Chemistry and Chemical Engineering
- نوع مقاله: Journal Article
- کلمات کلیدی: Minimization,Equation of state,Gas Hydrate,Gibbs free energy,Flash calculation
- چکیده:
- چکیده انگلیسی: The Michelsen stability and multiphase flash calculation by direct minimization of Gibbs free energy of the system at constant temperature and pressure, was used for systems containing gas hydrates. The solid hydrate phase was treated as a solid solution. The fugacities of all components of the hydrate phase were calculated as a function of compositions by the rearranged model of van der Waals and Platteeuw. Using this rearranged model enables the use of multiphase flash algorithm for systems containing gas hydrates. Based on this calculation for hydrate phases, we can determine amounts of hydrate formed and structure stability based on a minimum Gibbs free energy criterion.
- انتشار مقاله: 22-03-1384
- نویسندگان: Amir Abbas Izadpanah,Mohsen Vafaie Sefti,Farshad Varaminian
- مشاهده
- جایگاه : پژوهشی
- مجله: Gas Processing Journal
- نوع مقاله: Journal Article
- کلمات کلیدی: Tetrahydrofuran Hydrate,Differential Scanning Calorimetry,Formation Heat,Phase Change Temperature,Specific Heat Capacity
- چکیده:
- چکیده انگلیسی: In this study, a differential scanning calorimetry (DSC) has been used to characterize tetrahydrofuran (THF) hydrate formation with and without the presence of sodium and chloride salts. The thermal properties including the heat of formation, phase change temperature and specific heat capacity of THF hydrate formation have been determined. When salts are present, THF hydrate is inhibited, so that the phase change temperature shifts to a lower temperature, a broadening of the DSC peak can be seen and the height of the peak and the heat of formation decreases. Because the heat capacity depends on the heat of formation, it reduces when salt is present. The results show that the sodium salt solutions have exhibited the best performance on delaying nucleation of hydrate in order of Na2SO3 > NaF > NaCl, while chloride salt solutions, especially CaCl2, have demonstrated that can reduce the heat of formation to around 65% compared to that of without salt.
- انتشار مقاله: 10-08-1397
- نویسندگان: Parisa Naeiji,Farshad Varaminian
- مشاهده
- جایگاه : پژوهشی
- مجله: Gas Processing Journal
- نوع مقاله: Journal Article
- کلمات کلیدی: Stability,Methane,Gas Hydrate,Ethane,Structural Changes
- چکیده:
- چکیده انگلیسی: Abstract: Â In this study, the change in the crystalline structure of gas hydrate was predicted for ternary mixture of methane-ethane-water. For this purpose, the tangent plane distance (TPD) minimization method was used. First, the calculations were performed for the binary mixtures of methane-water and ethane-water as the gas and liquid phases. The results show that for a binary mixture of these components in the gas phase, at the temperatures of 274 K and 275 K, for a wide range of pressure, the phase remains stable however, the liquid phase is unstable and it splits into two or more new phases. The method was used for any possible new phases and the stable new phases determined by TPD minimization. By using this method for the ternary mixture at 20 different points (pressure and composition) at the temperature of 277.6 K, the results for stable phases are found to be consistent with the literature further, a structural change from sI to sII is observed at methane mole fraction of 0.74, and another structural change from sII to sI is observed at methane mole fraction of 0.99 at 277.6 K. This method can be used for the stability analysis of more points to predict the boundary of the phase diagram and stable zone for different phases. In this study, the genetic algorithm was used for minimization of TPD function.Â
- انتشار مقاله: 26-03-1395
- نویسندگان: Farshad Varaminian,Hadi Behjati Rad
- مشاهده