Binary Interaction Parameter Correlations Research Articles

A thermodynamic model to predict propane solubility in bitumen and heavy oil based on experimental fractionation and characterization

Propane has been suggested as suitable solvent for solvent-aided bitumen recovery methods such as Vapour Extraction (VAPEX), N-Solv (hot solvent injection), and Expanding Solvent-Steam Assisted Gravity Drainage (ES-SAGD). Characterization of bitumen and phase behaviour study of solvent/bitumen systems are the initial steps towards an optimized and successful solvent-aided bitumen recovery process. In this study, Athabasca bitumen is experimentally fractionated to four cuts using modified vacuum distillation and then each cut is characterized. The phase behaviour data including solubility, density, and viscosity of propane/bitumen cuts are measured in wide ranges of temperature and pressure. Using the measured solubility data of propane/bitumen cuts, the PR-EoS is tuned and a binary interaction parameter correlation between propane and bitumen components is developed. The bitumen is then characterized using the boiling point or carbon number distribution obtained by Simulated Distillation test (ASTM D7169). The generalized model is then implemented to calculate the propane solubility in two bitumen samples from different reservoirs (Athabasca and Cold Lake). Our proposed model in this paper, predicted the propane solubility in Athabasca bitumen sample with an average deviation of 1.8 mol.% without using any experimental data of propane/bitumen system or tuning parameter. The proposed model was also evaluated by predicting the propane solubility in Cold Lake bitumen. The propane solubility in Cold Lake bitumen was calculated with an average deviation of 3.0 mol.%, which shows the generality of the proposed model.

Binary interaction parameters of CO2−heavy-n-alkanes systems by using Peng–Robinson equation of state with modified alpha function

A generalized temperature-dependent binary interaction parameter (BIP) correlation has been developed for CO2−heavy-n-alkanes binary systems by using the Peng–Robinson equation of state (PR EOS) with the modified alpha function. The extensive experimentally measured vapour–liquid equilibria (VLE) data of CO2−heavy-n-alkanes systems in the temperature range of 277.59–663.75 K have been collected, including a series of heavy−n-alkanes from n-decane (n-C10H22) to n-tetratetracontane (n-C44H90). The BIP is found to be not only sensitive to temperature, but also decreased with carbon number of n-alkane. A BIP correlation for CO2−heavy-n-alkanes systems is then developed as a function of both the reduced temperature of CO2 and acentric factor of n-alkane. The newly proposed BIP correlation coupled with the modified alpha function in the PR EOS is found to be able to accurately reproduce 546 measured data points included in the database with an overall AARD of 4.7%. As for the 16 data points for CO2−n-C20H42 systems and 15 data points for CO2−n-C16H34 systems which are excluded in the database, a preferable prediction is respectively obtained by this work with AARDs of 6.6% (n-C20H42) and 6.5% (n-C16H34) in comparison of 20.9% (n-C20H42) and 12.6% (n-C16H34) from an existing correlation. Finally, it is shown that the newly developed BIP correlation can be well incorporated in the PR EOS with two original alpha functions.

Determination of Saturation Pressures and Swelling Factors of Solvent(s)–Heavy Oil Systems under Reservoir Conditions

Techniques have been developed to experimentally and theoretically determine saturation pressures and swelling factors of solvent(s)–heavy oil systems under reservoir conditions. Experimentally, PVT tests are performed to measure saturation pressures and swelling factors of a C3H8–heavy oil system and a CH4–C3H8–heavy oil system under reservoir conditions, respectively. Theoretically, the volume-translated Peng–Robinson equation of state (PR-EOS) together with the modified alpha function has been used to model phase behavior of the aforementioned solvent(s)–heavy oil systems. A binary interaction parameter (BIP) correlation has been developed for CH4–heavy oil systems based on the literature data. As for the CH4–C3H8–heavy oil system with a fixed composition, both saturation pressure and swelling factor increase with temperature. The PR-EOS together with the modified alpha function and the newly developed BIP correlation is able to predict the saturation pressures and swelling factors of the CH4–C3H8–heav...

Determination of Mutual Solubility between CO2 and Water by Using the Peng–Robinson Equation of State with Modified Alpha Function and Binary Interaction Parameter

Techniques have been developed to determine mutual solubility between CO2 and water by using the Peng–Robinson equation of state (PR EOS) with a modified alpha function and a new binary interaction parameter (BIP) correlation in the presence and absence of hydrocarbons. More specifically, the alpha function for the water compound is modified by improving its prediction for water vapor pressure in the full temperature range of 273.16 to 647.10 K with an overall absolute average relative deviation (AARD) of 0.07%. Also, the polynomial temperature-dependent BIP correlation for the CO2–water pair in the aqueous phase is proposed by matching CO2 solubility in water at temperatures from 273.15 to 448.15 K and pressures up to 100 MPa. It is found that the newly modified alpha function together with the proposed BIP correlation provides more accurate prediction of the CO2 solubility in water with an overall AARD of 6.12%, compared with 8.67% from the previous exponential BIP correlation. As for the nonaqueous phase of the binary CO2–water system, it is found that a constant BIP for the CO2–water pair generally results in a good agreement between the reported and predicted compositions of the CO2-rich phase. Furthermore, the accurate solubility prediction of either CH4 or CO2 in the water-rich phase of the ternary CH4–CO2–water systems has been achieved with an overall AARD of 6.15% at a temperature of 344.15 K and pressures of 10, 20, 50, and 75 MPa, respectively.

Enhanced Swelling Effect and Viscosity Reduction of Solvent(s)/CO2/Heavy-Oil Systems

SummaryIn this paper, techniques have been developed to examine the enhanced swelling effect and viscosity reduction of CO2-saturated heavy oil with the addition of either solvent C3H8 or solvent n-C4H10. Experimentally, pressure/volume/temperature (PVT) tests are conducted to measure the saturation pressure, swelling factor, and viscosity of the C3H8/heavy-oil system, the C3H8/CO2/heavy-oil system, and the n-C4H10/CO2/heavy-oil system, respectively, in the overall temperature range of 280.45 to 391.55 K. It has been found that an increased swelling effect of heavy oil is obtained by adding the gas solvent C3H8 or n-C4H10 into the CO2 stream. An enhanced viscosity reduction of the CO2/heavy-oil system is also achieved in the presence of either C3H8 or n-C4H10. The enhanced swelling effect and viscosity reduction caused by adding either C3H8 or n-C4H10 into the CO2 stream are particularly favorable for achieving a higher heavy-oil recovery compared with pure-CO2 processes. Theoretically, three binary-interaction-parameter (BIP) correlations in the Peng-Robinson (PR) equation of state (EOS) (PR-EOS) method have been proposed for respectively characterizing CO2/heavy-oil binaries, C3H8/heavy-oil binaries, and n-C4H10/heavy-oil binaries by treating each oil sample as a single pseudocomponent with its molecular weight (MW) and specific gravity (SG). The BIP correlations (together with the PR-EOS) can be used to predict the saturation pressures and swelling factors of the C3H8/CO2/heavy-oil system and the n-C4H10/CO2/heavy-oil system with a generally good accuracy.

Determination of Multiphase Boundaries and Swelling Factors of Solvent(s)–CO2–Heavy Oil Systems at High Pressures and Elevated Temperatures

A generalized methodology has been proposed and successfully applied to determine multiphase boundaries as well as swelling factors of solvent(s)–CO2–heavy oil systems at high pressures and elevated temperatures. Experimentally, two- and three-phase boundaries and swelling factors have been respectively measured by conducting PVT tests in the temperature range of 280.45 to 396.15 K. Theoretically, the Peng–Robinson equation of state (PR EOS) combined with the modified alpha function has been applied to describe phase behavior of the solvent(s)–CO2–heavy oil systems. More specifically, an exponential distribution function is used to split a heavy oil sample, whereas the logarithm-type lumping method is employed to group single carbon numbers (SCNs) into multiple carbon numbers (MCNs). The exponents associated with two binary interaction parameter (BIP) correlations are respectively tuned for the alkane solvent-pseudocomponent pair and CO2-pseudocomponent pair to match the measured saturation pressures. It is found that six pseudocomponents combined with the BIP correlation as a function of critical volume is sufficient to predict saturation pressure with an absolute average relative deviation (AARD) of 5.07%. In addition, the PR EOS model associated with the selected parameters is applied to predict three-phase boundaries for a C3H8–CO2–heavy oil mixture and a n-C4H10–CO2–heavy oil mixture yielding an overall AARD of 4.58%. As for swelling factors, the Peneloux et al. method provides the minimum AARD of 2.09% in comparison with 4.00% from the Jhaveri et al. method and 2.41% from the Twu et al. method, respectively.

Phase Behaviour of C3H8/n-C4H10/Heavy-Oil Systems at High Pressures and Elevated Temperatures

Summary Phase behaviour of C3H8/n-C4H10/heavy-oil systems at high pressures and elevated temperatures has been experimentally and theoretically investigated. Experimentally, a versatile pressure/volume/temperature (PVT) system is used to determine the liquid/vapour phase boundary (i.e., saturation-pressure lines) and swelling factors of C3H8/n-C4H10/heavy-oil systems with varying compositions at high pressures up to 5030.0 kPa and elevated temperatures up to 396.15 K. During the experiments, heavy oil is added continuously into the solvent and the injection process can be terminated within a short period. No noticeable asphaltene precipitation has been observed throughout the measurements for the four mixtures. The viscosities of the corresponding solvent(s)-saturated heavy-oil systems are measured by using a customized capillary viscometer at 298.85 K. Theoretically, the volume-translated Peng-Robinson equation of state (PR EOS) (Peng and Robinson 1976) with a modified alpha function is used to model the experimental phase behaviour of C3H8/n-C4H10/heavy-oil systems. Two binary-interaction-parameter (BIP) correlations, respectively developed for the C3H8/heavy-oil system and n-C4H10/heavy-oil system, are incorporated into the volume-translated PR EOS model. The two BIP correlations together with the volume-translated PR EOS are found to be capable of predicting the saturation pressures and swelling factors of the C3H8/n-C4H10/heavy-oil systems with a good accuracy, although the prediction accuracy is reduced at temperatures close to the critical temperature of a pure solvent. In addition, comparison of five commonly used mixing rules indicates that the Lobe's mixing rule (Lobe 1973) is more appropriate to predict the viscosity of heavy oil diluted by C3H8 and/or n-C4H10.

Determination of Three-Phase Boundaries of Solvent(s)–CO2–Heavy Oil Systems under Reservoir Conditions

The liquid–liquid–vapor (L1L2V) phase boundaries of solvent(s)–CO2–heavy oil systems under reservoir conditions are experimentally and theoretically determined. Experimentally, the L1L2V phase boundaries of one CO2–heavy oil mixture, one C3H8–CO2–heavy oil mixture, and one n-C4H10–CO2–heavy oil mixture in the pressure–temperature (P–T) diagram are determined using a versatile pressure–volume–temperature (PVT) setup. The addition of an alkane solvent to the CO2–heavy oil system tends to expand the pressure and temperature span of the L1L2V phase boundary, while the L1L2V phase boundary of the solvent(s)–CO2–heavy oil system shows its tendency to move toward the high-temperature and low-pressure region of the P–T diagram. Theoretically, the previously developed binary interaction parameter (BIP) correlations for CO2–heavy oil binary, C3H8–heavy oil binary, and n-C4H10–heavy oil binary are incorporated into the Peng–Robinson equation of state (PR EOS) to determine the three-phase boundaries of the above-mentioned systems. The PR EOS with a modified α function and the BIP correlations is found to provide a generally good prediction of the experimentally measured L1L2V phase boundaries of the solvent(s)–CO2–heavy oil systems under reservoir conditions.

Correlation to predict solubility of hydrogen and carbon monoxide in heavy paraffins

The Fischer–Tropsch (FT) reactor and hydrocracker, which are important elements of a synthetic liquid fuel process, are multi-phase reactors having gas–solid–liquid reactions involving H2 and/or CO. To predict the reactor performance, it is therefore important for simulation models used in the techno-economic or feasibility studies of such processes to accurately capture the solubility of H2 and CO in the reactant–product mixture. This poses challenges in terms of the asymmetric nature of the mixture and accurate characterization of the components involved. Using solubility experimental data and validated component characterization equations from literature, correlations to determine the Peng–Robinson binary interaction parameters and hence, predict the solubility of H2 and CO are presented. These binary interaction parameter correlations are expressed as a function of the solvent carbon number and temperature.

Vapor-Liquid Equilibrium of Ethylene + Mesitylene System and Process Simulation for Ethylene Recovery

The amount of ethylene in refinery off-gas is high with a mass fraction of 20%, but the refinery off-gas is usually used as fuel gas in most refineries. The separation and recovery of ethylene is of remarkable significance for saving energy and reducing carbon dioxide emission. The aim of this paper is to use a novel absorbent mesitylene for the ethylene absorption process and assess its application feasibility through the ethylene + mesitylene vapor-liquid equilibrium data measurement and its binary interaction parameter correlation, as well as the simulation for ethylene separation process.

Comparison of two algorithms for least squares parameter estimation

The Fischer–Tropsch (FT) reactor and hydrocracker, which are important elements of a synthetic liquid fuel process, are multi-phase reactors having gas–solid–liquid reactions involving H2 and/or CO. To predict the reactor performance, it is therefore important for simulation models used in the techno-economic or feasibility studies of such processes to accurately capture the solubility of H2 and CO in the reactant–product mixture. This poses challenges in terms of the asymmetric nature of the mixture and accurate characterization of the components involved. Using solubility experimental data and validated component characterization equations from literature, correlations to determine the Peng–Robinson binary interaction parameters and hence, predict the solubility of H2 and CO are presented. These binary interaction parameter correlations are expressed as a function of the solvent carbon number and temperature.