ارائه يك معادله حالت جديد SAFT جهت بررسي رفتار فازي سيالات خالص و مخلوط ها

چكيده انگليسي :

Presentation of a New SAFT Equation of State for Predicting Phase Behavior of Pure Fluids and Mixtures Mohammad Razaghi mo7ammad razaghi@gmail com Date of Submission 16 February 2013 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Mohammad Reza Ehsani ehsanimr@cc iut ac irAbstract Heavy oil has recently become an important resource as conventional oil reservoirs have limitedproduction and oil price has risen More than 6 trillion barrels of oil in place have been attributed to theworld s heaviest hydrocarbons Therefore heavy oil reserves account for more than three times the amountof combined world reserves of conventional oil and gas Heavy oils cover a large range of API gravities from 22 to less than 10 This wide range of values means that heavy oils vary greatly in their physicalproperties Thus extensive research is required before the properties of heavy oil can be properly understood Molecular thermodynamics is an engineering discipline rooted in molecular physics and physical chemistryand aimed at developing practical models that predict the properties of matter The goal of this work is todevelop a molecular thermodynamic model for predicting fluid densities phase equilibria and energyfunctions such as enthalpy Chemical engineers need these properties to develop and design new processesand materials and to make these processes energy efficient and environmentally benign The approach is tohypothesize a mathematical approximatical approximation that captures interactions among real moleculeson the basis of a molecular theory called the statistical associating fluid theory SAFT In thisapproximation each molecule is composed of spherical segments that interact according to a square wellpotential In this study a modified simplified statistical associating fluid theory SSAFT equation of statehas been applied to predict the phase equilibrium behavior of associating and non associating compounds and their binary mixtures The new equation of state has the same number of adjustable parameters as theoriginal SAFT equation In order to study multicomponent systems the equation is first applied to purefluids Three molecular parameters are required to obtain the thermodynamic properties of pure substancesnamely numbers of segments m temperature independent segment molar volume in a closed packedarrangement v and depth of the square well potential u Two additional parameters are required todescribe the associating molecules the association energy and volume The experimental data of liquiddensities and vapor pressure for pure fluids studied in this work were used to obtain the best values for theparameters of the new version of SSAFT The result obtained from the new version of SSAFT for liquiddensities and vapor pressure of pure associating and non associating fluids were compared with thoseobtained from the original SSAFT equation of state The results showed that the new version of SSAFT canalso accurately correlate the experimental data of liquid density and vapor pressure for systems studied Binary mixtures are also investigated and reasonable results are obtained with no additional binaryparameters Finally the new SSAFT equation of state was applied for prediction of phase behavior of heavyoil that showed good accuracy for this issue The results show that the accuracy of the new equation of stateis higher than SSAFT EOS so that the relative error of the new equation of state compared to experimentalvalues in the calculation of the vapor pressure and liquid density of pure substances respectively 30 and 25

رزاقي، محمد

ارائه يك معادله حالت جديد SAFT جهت بررسي رفتار فازي سيالات خالص و مخلوط ها