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    Thermodynamic Modeling of Hydrogen Hydrate Formation with and without Help Molecules

    , M.Sc. Thesis Sharif University of Technology Ghorbanzadeh, Maryam (Author) ; Taghikhani, Vahid (Supervisor) ; Ghotbi, Siroos (Supervisor)
    In this study equilibrium condition of pure hydrogen hydrates is determined with Lee-Holder model. Two hydrogen molecules and four hydrogen molecules encaged in the small and large cavities respectively. Langmuir constant of hydrogen is calculated with the Exp-6 potential. Lee et al. reported parameter of this model by integrating ab initio calculation with classical statistical thermodynamics. This model reasonably predicts dissociation pressures of hydrogen hydrates.Calculated reference parameters are used in modeling of binary hydrogen hydrates. Lattice distortion model is used for modeling of binary hydrogen hydrates with tetrahydrofuran (THF) as a promoter. Cavity radius and parameters... 

    Natural gas hydrate promotion capabilities of toluene sulfonic acid isomers

    , Article Polish Journal of Chemical Technology ; Vol. 16, Issue. 1 , 2014 , pp. 97-102 ; ISSN: 1899-4741 Jarrahian, A ; Heidaryan, E ; Sharif University of Technology
    The purpose of this study was to investigate the natural gas hydrate promotion capabilities of the hydrotrope Toluene Sulfonic Acid (TSA) isomers as an additive. The capabilities of TSA isomers were measured with different concentrations. The optimum additive concentration for hydrate formation was determined for the given pressure, temperature, mixing condition, and cooling time. The natural gas hydrate promotability of para-TSA was found to be 20% and 35% more than meta-TSA and ortho-TSA respectively at the optimum concentration. Beyond the optimum TSA concentration, the hydrate formation declined as the ice formation reduced the overall gas-to-water volume ratio in the hydrates  

    Evolving a robust modeling tool for prediction of natural gas hydrate formation conditions

    , Article Journal of Unconventional Oil and Gas Resources ; Volume 12 , December , 2015 , Pages 45-55 ; 22133976 (ISSN) Soroush, E ; Mesbah, M ; Shokrollahi, A ; Rozyn, J ; Lee, M ; Kashiwao, T ; Bahadori, A ; Sharif University of Technology
    Elsevier Ltd  2015
    Natural gas is a very important energy source. The production, processing and transportation of natural gas can be affected significantly by gas hydrates. Pipeline blockages due to hydrate formation causes operational problems and a decrease in production performance. This paper presents an improved artificial neural network (ANN) method to predict the hydrate formation temperature (HFT) for a wide range of gas mixtures. A new approach was used to define the variables for formation of a hydrate structure according to each species presented in natural gas mixtures. This approach resulted in a strong network with a precise prediction, especially in the case of sour gases. This study also... 

    A new hydration model in correlating the mean ionic activity coefficient and density of aqueous electrolyte solutions

    , Article Journal of Dispersion Science and Technology ; Volume 31, Issue 5 , 2010 , Pages 641-649 ; 01932691 (ISSN) Pazuki, G. R ; Taghikhani, V ; Vossoughi, M ; Sharif University of Technology
    In this article, a new hydration model has been proposed to study the phase behavior of aqueous electrolyte solutions. The proposed model distinguishes between an anion and cation in the electrolyte solution. The model has three adjustable parameters which can be obtained using the experimental data of the mean ionic activity coefficients for 113 electrolyte solutions. The results of the proposed model were compared with those of obtained from the Pitzer, the E-NRTL and the E-Wilson models. The results showed that the proposed model can accurately correlate the mean ionic activity coefficients of the aqueous electrolyte solutions than the other models. Also, the proposed model was used in... 

    Effect of Nano-Tio2 additions on the densification and properties of magnesite–dolomite ceramic composites

    , Article Iranian Journal of Science and Technology, Transaction A: Science ; Volume 42, Issue 2 , 2018 , Pages 567-575 ; 10286276 (ISSN) Ghasemi Kahrizsangi, S ; Shahraki, A ; Farooghi, M ; Sharif University of Technology
    Springer International Publishing  2018
    Nano-titania, up to 8 wt%, was added to magnesite–dolomite refractory matrix. The phase and microstructure analyses of samples heated up to 1650 °C for 3 h were studied by XRD and SEM/EDS, respectively. The physical properties are reported in terms of bulk density, apparent porosity, and hydration resistance. In addition, the mechanical behavior was studied by a cold crushing strength (CCS), and flexural strength at 1200 °C test. As a result, it was found that the presence of nano-TiO2 in the magnesite–dolomite matrix induced titanates formation (Mg2TiO4 and CaTiO3), which improved the sintering process. Nano-titania influenced the bonding structure through a direct bonding enhancement. In... 

    Prediction of hydrate formation for the systems containing single and mixed electrolyte solutions

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 26, Issue 1 , 2007 , Pages 35-45 ; 10219986 (ISSN) Shabani, M. M ; Rashtchian, D ; Ghotbi, C ; Taghikhani, V ; Khayat, G ; Sharif University of Technology
    Iranian Journal of Chemistry and Chemical Engineering  2007
    In this work the effect of electrolytes on hydrate formation was investigated. To do so, a new model was used in predicting the hydrate formation conditions in presence of both single and mixed electrolyte solutions. The new model is based on the van der Waals - Platteeuw hydrate equation of state. In order to evaluate the values for the activity of water in electrolyte solutions the simplified version of the Ghotbi-Vera Mean Spherical Approximation (SGV-MSA) model was used. According to the SGV-MSA model the ions in the solutions are considered as charged hard spheres with different sizes. The values of the parameters for the SGV-MSA model are independent of temperature and depend only on... 

    Effect of hydrazine hydrate on the luminescence properties of MPA capped CdTe nanocrystals in hot injection method

    , Article Journal of Luminescence ; Vol. 156, issue , 2014 , p. 235-239 Mobedi, N ; Marandi, M ; Zare Bidaki, H ; Sharif University of Technology
    In this research MPA capped CdTe nanocrystals with sizes around 2.7-3.5 nm were grown in aqueous solution. The process was performed through the reaction of NaHTe with MPA and CdCl2 solution in high temperature. The synthesis was carried out in two different states of standard and modified forms. In the modified synthesis, the hydrazine hydrate material was added to the MPA plus CdCl2 solution before injection. The evolution of the nanocrystals size and PL quantum yield was monitored during the heating time for the growth. The results demonstrated that for the standard synthesis the growth rate was slow. The CdTe nanocrystals with high PL quantum yields were achieved in more than 10 h of... 

    Near wellbore thermal effects in a tight gas reservoir: Impact of different reservoir and fluid parameters

    , Article Journal of Unconventional Oil and Gas Resources ; Volume 16 , 2016 , Pages 1-13 ; 22133976 (ISSN) Shad, S ; Holmgrün, C ; Calogirou, A ; Sharif University of Technology
    Elsevier Ltd  2016
    Temperature changes in and around the wellbore could lead to significant well performance and flow assurance issues. Despite its importance, near wellbore temperature change due to gas production and its importance on well performance is not well understood. Reduction of temperature in the near well bore section, could potentially lead to hydrate formation and as a result reduction of well performance. This work is aimed at evaluating the thermal behaviour in the near wellbore region of a low to tight permeability gas reservoir (ranging between 0.02 and 10 mD) during its natural depletion. The study is conducted by using a thermal-compositional simulator. The process required to simulate... 

    Kinetic modeling of gas hydrates formation in presence of additives using Artificial Neural Networks

    , M.Sc. Thesis Sharif University of Technology Mehruz Monfared, Saeed (Author) ; Taghikhani, Vahid (Supervisor) ; Ghotbi, Cyrus (Supervisor)
    Many researchers were interested in gas hydrates because of their especial properties. These researches divided in two fields, thermodynamic and kinetic. The studies on first field began since many years ago, and they provided suitable results. But the investigation of hydrate formation kinetic started for 30 years ago, approximately, and according to its features such as high complexity of crystallization process and severe dependency on system, yet the comprehensive and pervasive model was not presented. At this project, after the presentation and survey of diverse models, in order to kinetic modeling of available data, among different kinetic models a reaction model selected. Then primary... 

    The impact of ZrSiO4 nanoparticles addition on the microstructure and properties of dolomite based refractories

    , Article Ceramics International ; Volume 43, Issue 16 , 2017 , Pages 13932-13937 ; 02728842 (ISSN) Ghasemi Kahrizsangi, S ; Karamian, E ; Gheisari Dehsheikh, H ; Sharif University of Technology
    Dolomite base refractories have advantages such as high refractoriness, potential to produce pure steel molten, high alkaline corrosion resistance, and economical for consumers. However, application of these refractories has been limited due to their high potential to hydration with atmosphere humidity. In this research work, the impact of ZrSiO4 nanoparticles addition on the physical, thermo-mechanical, mechanical, and microstructure of the dolomite base refractories is investigated. Also, XRD and SEM/EDX analyses were used for determining generated ceramic phases and microstructure evaluation, respectively. Up to 3 wt% ZrSiO4 nanoparticles were added to the compositions. Compositions fired... 

    Charge asymmetry effect in ion transport through angstrom-scale channels

    , Article Journal of Physical Chemistry C ; Volume 123, Issue 2 , 2019 , Pages 1462-1469 ; 19327447 (ISSN) Yu, Y ; Fan, J ; Esfandiar, A ; Zhu, Y ; Wu, H ; Wang, F ; Sharif University of Technology
    American Chemical Society  2019
    Structural and dynamic properties of ions confined in nanoslits are crucial to understand the fundamental mechanism underlying a wide range of chemical and biological phenomena. K + and Cl - show similar ion mobilities in a bulk aqueous solution, whereas they exhibit a remarkable difference when transporting through an angstrom-scale channel. Our molecular dynamics simulations uncover that such discrepancy originates from the subtle differences in their hydration structures and preferable locations across the channel. Opposite charge causes different water dipolar orientations around ions, mediating the distance and tribological interactions between hydrated ions and channel's walls.... 

    , M.Sc. Thesis Sharif University of Technology (Author) ; Taghikhani, Vahid (Supervisor) ; Bozorg Mehri, Ramin (Supervisor) ; Ghotbi, Siroos (Supervisor)
    Gas hydrate is a nonstoichiometric structure that has been produced from water and gas in appropriate thermal and pressure conditions. There has been a long time that scientists work on predicting hydrate production condition. Predicting the hydrate behavior for pure substances is easier than mixtures; because there are some behaviors of mixtures that we do not know their reasons yet. In this thesis, there has been tried to give a model to describe hydrate reactions to temperature and pressure changes besides predicting the hydrate type and the cage occupancy. Since the hydrate behavior is nonstoichiometric, it is useful to know the cage occupancy to predict the amount of hydrate... 

    Modeling of Gas Hydrate Formation in Presence of Inhibitors Using the Fuzzy Logic

    , M.Sc. Thesis Sharif University of Technology Falahati, Mojtaba (Author) ; Taghikhani, Vahid (Supervisor) ; Ghotbi, Cyrus (Supervisor)
    Nowadays oil and gas industry has taken the pulse of world energy. Different countries of the world are trying more and more to explore and produce this black gold. To do so these countries has gained many experiences and even gone to seas and oceans to find oil and gas. In the process, they has faced with a new phenomenon called gas hydrate. The phenomenon which was unknown and destructive at first after excessive research, today is even called as the future energy source of the world. But what we discussed in this study is hydrate as a problem in oil and gas industry. Gas hydrates are formed in favorable temperature and pressure condition (low temperature and high pressure) in the... 

    Investigation Effect of Nano- sized Additives on Microstructure and properties of MgO-CaO Refracrories

    , M.Sc. Thesis Sharif University of Technology Ghasemi Kahrizsangi, Salman (Author) ; Nemati, Ali (Supervisor)
    Magnesia–Doloma refractories are considered as a mixed product of alkali products i.e. sintered (fused) magnesia and doloma in which 50-80 wt% magnesia is contained. These refractories enjoy some advantages such as high slag resistance corrosion, high-temperature performance, potential for production of pure molten iron and low cost due to abundance of magnesia and doloma resources in access. However, there exist some problems with these refractories that render them unsuitable for some applications. Among these cases, poor resistance of hydration can be cited that may constrain the amount of this refractory in various industrial applications. In the present work, the addition effect of... 

    Formation and Economic Study on Hydrate Technology with NGH Pellets

    , Article Journal of Dispersion Science and Technology ; Volume 34, Issue 2 , 2013 , Pages 259-267 ; 01932691 (ISSN) Tamsilian, Y ; Ebrahimi, A. N ; Ramazani S. A., A ; Sharif University of Technology
    This study presents economic and formation investigations on hydration effects by looking at natural gas hydrate (NGH) storage and transportation processes and formation conditions. The investigation includes experiments with methane. The obtained results show that the methane formation time increased linearly as the subcooling temperature decreased. Furthermore, the economic result indicates that the energy consumption parameter is appropriate for examining resource consumption for a system that, in turn, results in optimal capital investment through the storage and transportation process of NGH. The results also show that energy consumption increases logarithmically as the hydrate... 

    Phase equilibrium modeling of semi-clathrate hydrates of the CO2+H2/CH4/N2+TBAB aqueous solution system

    , Article Petroleum Science and Technology ; Volume 35, Issue 15 , 2017 , Pages 1588-1594 ; 10916466 (ISSN) Mesbah, M ; Soroush, E ; Roham, M ; Shahsavari, S ; Sharif University of Technology
    Taylor and Francis Inc  2017
    In this study, the semi-clathrate hydrate dissociation pressure for the CO2+N2, CO2+H2, CO2+CH4, and pure CO2 systems in the presence of different concentrations of TBAB aqueous solutions is predicted using a strong machine learning technique of multi-layer perceptron neural network (MLP-NN). The developed model, with an overall correlation coefficient (R2) of 0.9961 and mean square error (MSE) of 5.96E−02, presented an excellent accuracy in prognosticating experimental data. A complete statistical evaluation performed to promise the strength and generality of the multi-layer perceptron artificial neural network (MLP-ANN). In addition, the applicability of the proposed network and quality of... 

    Hydration strongly affects the molecular and electronic structure of membrane phospholipids

    , Article Journal of Chemical Physics ; Volume 136, Issue 11 , 2012 ; 00219606 (ISSN) Mashaghi, A ; Partovi Azar, P ; Jadidi, T ; Nafari, N ; Maass, P ; Tabar, M. R. R ; Bonn, M ; Bakker, H. J ; Sharif University of Technology
    We investigate the structure and electronic properties of phosphatidylcholine (PC) under different degrees of hydration at the single-molecule and monolayer type level by linear scaling ab initio calculations. Upon hydration, the phospholipid undergoes drastic long-range conformational rearrangements which lead to a sickle-like ground-state shape. The structural unit of the tilted gel-phase PC appears to be a water-bridged PC dimer. We find that hydration dramatically alters the surface potential, dipole and quadrupole moments of the lipids and consequently guides the interactions of the lipids with other molecules and the communication between cells  

    Nanofluid-assisted gas to hydrate (GTH) energy conversion for promoting CO 2 recovery and sequestration processes in the petroleum industry

    , Article Petroleum Science and Technology ; Volume 34, Issue 1 , 2016 , Pages 37-43 ; 10916466 (ISSN) Zarenezhad, B ; Montazeri, V ; Sharif University of Technology
    Taylor and Francis Inc  2016
    In this work the enhancement of gas to hydrate conversion employing the nanographene oxide (NGO)-based nanofluid regarding CO2 capture and sequestration recovery is investigated. A new series of experiments are carried out at different pressures, temperatures, agitation intensities and NGO promoter concentrations by using a newly developed fully automated GTH (gas to hydrate) energy converter. According to the presented results at the 3 MPa and 275.15 K and in the presence of 30 ppm NGO, it is possible to reach a CO2 gas to hydrate conversion of 95% at a low impeller speed in less than 2.5 h, which is quite interesting from an energy consumption standpoint. The presented approach can have... 

    The influence of silica nanoparticles addition on the physical, mechanical, thermo-mechanical as well as microstructure of Mag-Dol refractory composites

    , Article Ceramics International ; Volume 43, Issue 18 , 2017 , Pages 16780-16786 ; 02728842 (ISSN) Gheisari Dehsheikh, H ; Ghasemi Kahrizsangi, S ; Sharif University of Technology
    The high hydration potential of CaO and MgO phases restricted the application of Mag-Dol refractory composites. In this study, the impact of nano-silica (SiO2) addition on the physical, mechanical, thermo-mechanical as well as microstructure of Mag-Dol refractory composites is investigated. Mag-Dol compositions were prepared by using calcined dolomite and magnesite particles (micron, 0–1, 1–3, 3–5, and 5–8 mm), liquid resin, and 0, 0.5, 1, 1.5, 2, and 2.5 wt% nano SiO2 as additives. Specimens were heated up to 1650 °C for the 3 h soaking period. Fired specimens were characterized by physical (apparent porosity, bulk density, and hydration resistance), mechanical (cold crushing strength), and... 

    Molecular Simulation of Methane Hydrate Formation Investigation of [Emim][BF4] Ionic Liquid effects on Growth and Dissociation of Methane Hydrate Crystal Using Molecular Dynamics Simulation

    , M.Sc. Thesis Sharif University of Technology Abareshi, Bagher (Author) ; Ghotbi , Cyrus (Supervisor) ; Taghikhani, Vahid (Supervisor) ; Jalili, Amir Hossein (Supervisor)
    Formation of gas hydrates is a challenge in the oil and gas industry. Gas hydrate formation can be prevented by several methods. One of these methods is to utilize of inhibitor components. The gas hydrate inhibitors can affect hydrate formation from two aspects, i.e., thermodynamic or kinetic. In this work, thermodynamic and kinetic effects of [Emim][BF4] ionic liquid on growth and dissociation of methane hydrate crystal were investigated using molecular dynamics simulation. Molecular dynamics simulation is powerful tool to investigate the thermophysical, structural, and dynamic properties of methane hydrate and the formation, dissociation, and inhibition mechanisms at the molecular scale....