• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.222-228
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• 2018

Benzene is one of the most widely used basic materials in the petrochemical industry. Generally, benzene exists as a mixture with alcohols rather than as a pure substance. Further, the alcohols-added mixtures usually exhibit an azeotropic composition. In this context, knowledge of the phase equilibrium behavior of the mixture is essential for its separation and purification. In this study, the vapor-liquid equilibrium data were measured in favor of a recirculating VLE apparatus under constant pressure for the 1 - propanol / benzene system. The measured vapor - liquid equilibrium data were also correlated by using the UNIQUAC and WILSON models and the thermodynamic consistency test based on the Gibbs/Duhem equation was followed. The results of the phase equilibrium experiment revealed RMSEs (Root Mean Square Error) and AADs (Average Absolute Deviation) of less than 0.05 for both models, indicating a good agreement between the experimental value and the calculated value. The results of the thermodynamic consistency test also confirmed through the residual term within ${\pm}0.2$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.3
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• pp.213-219
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• 2007

An experimental apparatus was constructed to obtain vapor-liquid equilibrium data for $CO_2/oil$ mixtures using mass analysis method with sample cylinder. Lubricants employed were POE (poly-ol ester) and PAG (poly alkylene glycol). The phase equilibria of $CO_2/oil$ mixtures prevailed in an equilibrium cell were observed through a couple of sight glasses at the opposite ends. Data were obtained over the temperatures $-10^{\circ}C,\;-5^{\circ}C,\;0^{\circ}C,\;5^{\circ}C,\;10^{\circ}C,\;25^{\circ}C,\;40^{\circ}C,\;60^{\circ}C,\;and\;80^{\circ}C$ under pressures up to 14 MPa and then mole fractions were calculated, respectively In general, more solubility of $CO_2$ is observed in POE than in PAG. Miscibility gap is closed for $CO_2/POE$ mixture but not for $CO_2/PAG$.

• Journal of the Korean Institute of Gas
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• v.14 no.2
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• pp.22-26
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• 2010

In this study, experimental vapor pressures and densities of vapor and liquid phases versus temperature were estimated using PC-SAFT equation. The estimated results were compared with those using PR equation of state. For the vapor phase densities, both equations well predicted the literature data. However, PC-SAFT equation showed better prediction capability for liquid phase densities. In the comparison of vapor-liquid equilibrium prediction capability for the binary systems of methane and ethane, PC-SAFT equation was better than the PR equation.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.903-914
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• 2008

This study was undertaken for the production capacity expansion and energy saving through entire process simulation and optimization for the commercial process of manufacturing monoethylene glycol as a staple from ethylene oxide. Aspen $Plus^{TM}$(ver. 2006) was employed in the simulation and optimization work. The multicomponent vapor-liquid equilibria involved in the process were calculated using the NRTL-RK equation. As for the binary interaction parameters required for a total of 91 binary systems, those for 8 systems were self-supplied by the simulator, those for 28 systems were estimated through regression of the VLE data in the literature, and the remainder were estimated with the estimation system built in the simulator. Subsequent to ascertaining the accuracy of the generated parameters through comparison between actual and simulated process data, sensitive variables highly affecting the process were searched and selected using sensitivity analysis tool in the simulator. The optimum operating conditions minimizing the total heat duty of the process were investigated using the optimization tool based on the successive quadratic programming in the simulator.

• Korean Chemical Engineering Research
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• v.43 no.5
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• pp.579-587
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• 2005

Phase separations of Poly(4-vinylphenol)(PVPh)/acetone and PVPh/methyl ethyl ketone solutions were measured using the thermal optical analysis (TOA) method. The phase separations of these system showed the behaviors of LCST-type (lower critical solution temperature). The measured cloud temperatures were lowered with increasing molecular weight of PVPh, and cloud temperatures of PVPh/MEK solutions shifted to higher temperature regions, compared to the PVPh/acetone solutions. Phase equilibria of PVPh/ketone solutions were described with taking account of self-associations of PVPh and cross-associations between PVPh and solvent, by using the PC-SAFT equation of state. PC-SAFT EoS parameters of PVPh and cross-association parameters were determined by simultaneously fitting liquid density data of PVPh and VLE data of the PVPh/acetone system. The estimated parameters of PVPh and cross-association parameters were utilized to calculations of the binodal and spinodal curves, and the calculated binodal curves were in good agreements with the experimental cloud temperatures.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.755-761
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• 2009

To a first approximation, phase behavior of a system becomes increasingly skew in proportion to the boiling point difference of system-forming constituents. Therefore, phase behavior data of a system of a large boiling point difference are to be experimentally measured for thorough understanding of the thermodynamic characteristics of such system. In this work, isobaric vapor-liquid equilibrium of a mixture consisting of toluene and cresol, which shows a large boiling point difference of nearly $100^{\circ}C$ and is consequently expected to be considerably nonideal, was measured by using a recirculating equilibrium cell at various subatmospheric pressures ranging from 10 kPa to 60 kPa. The measured VLE data were correlated with NRTL and UNIQUAC models in a satisfactory manner and the accompanying thermodynamic consistency test represented soundness of the measurements. In addition, the excess molar volume of the mixture was also measured with a vibrating densitometer and correlated with a Redlich-Kister polynomial. A negative excess volume prevailed over the whole concentration range, which indicates a favorable attraction between toluene and cresol isomers and results in an extensive miscibility.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.450-456
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• 2015

In the present study, modelling and optimization of ethanol-benzene separation process were performed using pressure-swing distillation. Order to obtain a reliable results, vapour-liquid equilibrium (VLE) experiments of ethanol-benzene binary system were performed. The parameters of thermodynamic equation were determined using experimental data and the regression. The pressure-swing distillation process optimization was performed to obtain high purity ethanol and high purity benzene into a low-high pressure columns configuration and a high-low pressure columns configuration. The heat duty values of the reboiler from simulation were compared, and the process was optimized to minimize the heat duty.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.893-900
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• 1997

In this study, vapor-liquid equilibria of a binary system, which consists of glycerol and water, are measured using a vaporrecirculating modified Othmer still at various subatmospheric pressures. The constituent components of the binary system considered in this study exhibit a large difference in the boiling temperatures. Since it is generally observed that the properties of a mixture greatly differ from those of the pure components, the phase equilibrium characteristics of a mixture can not be predicted from the properties of the pure components. Furthermore, an abrupt increase in the boiling temperature occurs as the concentration of the higher boiling component exceeds a certain value. Therefore, it is essential to acquire realistic phase equilibrium data of the mixture for industrial applications. Using the UNIQUAC model, the experimental vapor-liquid equilibrium data are correlated with good accuracy. The thermodynamic consistency test is also performed to ensure soundness of the data.

• Korean Chemical Engineering Research
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• v.43 no.3
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• pp.387-392
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• 2005

Recently, dimethyl carbonate (DMC) is considered as an alternative of MTBE (methyl tert-butyl ether), additive for non-leaded gasoline with their fast biodegradation rate and low toxicity. DMC is usually synthesized so far by oxidative carbonylation of methanol, and recently developed synthetic process is also started with methanol. Since the phase equilibria of the system, consisted of DMC and methanol or other reaction products on different temperature and pressure is necessary for the optimum separation process design and operation. However the reported phase equilibria and physical properties for DMC mixtures in the Dortmund Data Bank (DDB; thermodynamic property data bank) are quite rare. Besides, infinitely dilute properties are not found. In this work, isothermal vapor-liquid equilibria at 333.15 K for methanol+DMC binary system and mixing properties, excess molar volume and viscosity deviation at 298.15 K are directly measured and correlated. Additionally, infinitely dilute activity coefficient of methanol in the DMC solvent at three different temperatures are measured and compared with predicted values using modified UNIFAC (Dortmund).

• Fire Science and Engineering
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• v.16 no.3
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• pp.26-31
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• 2002

Bromotrifluoromethane(halon-1301) and bromochlorodifluoromethane(halon-1211) have been widely used as a clean fire extinguishing agents due to their outstanding properties. However, production and use of halon are currently being phased out under an international agreements Montreal Protocol because of global environmental concerns and HFCs have been considered as promising alter-natives for the replacement of halon since their ozone depletion potentials are low. The vapor-liquid equilibrium data are required as important basic information in evaluating the solubility of clean fire extinguishing agents and determining their optimal compositions. In this work, we chose HFCs such as HFC-22 HFC-125, and HFC-l34a for gaseous fire extinguishing agents and nitrogen as a pressurization gas for a proper jet velocity of these agents. Phase equilibria for binary mixtures of nitrogen/HFC-22, nitrogen/HFC-125, and nitrogen/HFC-l34a were measured in the temperature range from 283.15K to 303.15K. For equilibrium measurement, we used a circulation type apparatus in which both vapor and liquid phases were continuously recirculated. The experimental data were relatively well correlated with the Peng-Robinson equation of state with Wong-Sandier mixing rules.