Vapor Fugacity Research Articles

Nanopore confinement effects on phase behavior and capillary pressure in a Wolfcamp shale reservoir

As unconventional oil production is the main focus in petroleum industry, the phase behavior of fluids in nanopore media draws high attention nowadays. The extremely small pore sizes in shale reservoirs affect the fluid phase equilibrium. In this study, the phase equilibrium of Wolfcamp oil in nanopores is studied by coupling the cubic Peng–Robinson equation of state (PR-EOS) with the Young–Laplace capillary pressure equation, fugacity of vapor–liquid calculation, and shifted critical properties. A mercury injection experiment showed that 93.7% of pore diameters in Wolfcamp cores were less than 10nm. The capillary pressure curve in a real shale reservoir with a multicomponent Wolfcamp oil was generated for the first time. The results show that the bubble point pressure was suppressed by 17.3% when the pore radius (r) is 10nm, and by 63.8% when r is 1.5nm. The interfacial tension (IFT) decreases slowly when r is bigger than 50nm. However, as r becomes smaller, the IFT decreases rapidly, especially when r is less than 10nm. The nanopore confinement narrows the two-phase region, resulting in a lower capillary pressure and elongating the lower gas–oil ratio production period.

Techno-economic study of enhanced absorber–regenerator configurations for improving an industrial Sulfinol-M-based acid gas removal processes

Abstract In this study, the rigorous simulation and design of an industrial Sulfinol-M-based acid gas removal (AGR) process was developed. All simulations were performed using Aspen HYSYS with extended NRTL activity coefficient model for the liquid phase and the Peng–Robinson state equation for the vapor fugacity coefficients. The simulation results from VMGSim and Aspen HYSYS were compared with design data from an integrated gasification combined cycle power plant. Several enhanced absorber–regenerator configurations were presented to improve AGR process efficiency. Sustainability analysis was conducted to assess these process alternatives in terms of energy requirements, costs, and environmental impacts. The results showed that the proposed self-heat recuperation configuration could reduce the energy requirements, total annual costs, carbon footprint by 74.7%, 40.1%, and 48.9%, respectively, compared with the conventional configuration.

An improved model for CO2 solubility in aqueous electrolyte solution containing Na+, K+, Mg2 +, Ca2 +, Cl− and SO42 − under conditions of CO2 capture and sequestration

Based on the Pitzer electrolyte theory for activity coefficient and an accurate equation of state for vapor fugacity, an improved activity-fugacity model is developed to calculate CO2 solubility in aqueous KCl, MgCl2, CaCl2, Na2SO4, K2SO4 and MgSO4 solutions, respectively. The valid range of temperature, pressure and ion strength is up to 450K, 500bar and 5molkg−1. Average absolute deviation of CO2 solubility is about 5% compared to a large number of experimental data available, within or close to experimental uncertainties. By combining the interaction parameters of CO2 and ions developed here with those of CO2 and Na+ and Cl− from an earlier study of Mao et al. (2013), this model can be used to accurately predict CO2 solubility in aqueous mixed-salt solution containing Na+, K+, Mg2+, Ca2+, Cl− and SO2–4under conditions of CO2 capture and sequestration (generally less than 423K and 500bar). Computer code of the application program can be obtained from the corresponding author (maoshide@163.com).

An improved thermodynamic model for Wax precipitation using a UNIQUAC + PC-SAFT approach

Wax precipitation is a serious challenge in the oil industry due to decrease in oil production and transmission efficiency. Wax precipitation modeling plays an important role to forecast the Wax appearance temperature (WAT) and the amount of precipitation. In this work, solid solution theory is used for Wax precipitation modeling. The perturbed hard chain statistical associating fluid theory (PC-SAFT) equation of state (EOS) is implemented in order to calculate the fugacity of vapor and liquid phases and their corresponding compressibility factors. UNIQUAC activity coefficient model is chosen to account for the non-ideality of solid phase. The resultant equilibrium ratios are included in the three phase equilibrium calculations and stability analysis. The proposed model is applied to calculate the amount of precipitates and WAT for six North Sea oil samples to evaluate the prediction accuracy. The crude oil samples contain several cuts and heavy fractions. The PC-SAFT EOS parameters for petroleum plus fractions are estimated using available correlations in literature. In addition, the modeling results are compared with the results of Lira-Galeana et al. [1], Pedersen et al. [2] and Dalirsefat and Feyzi [3] models. The results show improvements and demonstrate the proposed model as a comparable forecasting tool for Wax precipitation modeling in oil transmission and processing facilities.

Chain length effect of ionic liquid 1-alkyl-3-methylimidazolium chloride on the phase equilibrium of methane hydrate

A high pressure differential scanning calorimeter was used to determine the dissociation temperature of methane hydrate in the presence of ionic liquid 1-alkyl-3-methylimidazolium chloride under a constant pressure ranging from 5 to 35 MPa. A homologous series of 1-alkyl-3-methylimidazolium chloride with different alkyl chain lengths: 1-ethyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride and 1-decyl-3-methylimidazolium chloride, were chosen to examine the chain length effect on the dissociation temperature for methane hydrates. All these ionic liquids have inhibition effect on methane hydrate formation. Moreover, the shorter the alkyl chain length is, the stronger the inhibition effect is. That is, the inhibition effect of these ionic liquids on the methane hydrate formation is in the order of 1-ethyl-3-methylimidazolium chloride>1-hexyl-3-methylimidazolium chloride>1-decyl-3-methylimidazolium chloride. The three-phase vapor–liquid–hydrate equilibrium condition of methane hydrate in the presence of 1-alkyl-3-methylimidazolium chloride was successfully described by a predictive thermodynamic model. The Peng–Robinson–Stryjek–Vera equation of state incorporated with COSMO-SAC activity coefficient model and the first order modified Huron–Vidal mixing rule were applied to evaluate the fugacity of vapor and liquid phase. An explicit pressure dependence of the Langmuir adsorption constant in the modified van der Waals and Platteeuw model was applied to determine the fugacity of hydrate phase. The average absolute relative deviation in predicted dissociation temperature from the predictive thermodynamic model was 0.54%. In addition, these experimental data of dissociation temperatures were further correlated to a general correlation of Østergaard et al. (J. Petroleum Sci. Eng. 48 (2005) 70–80) and the average absolute relative deviation in the correlated dissociation temperature was 0.05%.

Inhibition effect of 1-ethyl-3-methylimidazolium chloride on methane hydrate equilibrium

The dissociation conditions of methane hydrate in the presence of 0.1, 0.2, 0.3 and 0.4 mass fraction of 1-ethyl-3-methylimidazolium chloride (abbreviated by EMIM-Cl hereafter) were experimentally determined. A high pressure micro-differential scanning calorimeter equipped with a motorized pump was applied to measure the dissociation temperature of the (hydrate+liquid water+vapor) three-phase equilibrium under a constant pressure process with a pressure ranging from (5.0 to 35.0)MPa. The addition of EMIM-Cl would inhibit the methane hydrate formation. The most significant inhibition effect was observed at 0.4 mass fraction of EMIM-Cl in aqueous solution to lower the dissociation temperature by 12.82K at 20.00MPa in comparison to that of the (methane+water) system. The Peng–Robinson–Stryjek–Vera equation of state incorporated with COSMO-SAC activity coefficient model and the first order modified Huron–Vidal mixing rule were applied to evaluate the fugacity of vapor and liquid phase. A modified van der Waals and Platteeuw model with an explicit pressure dependence of the Langmuir adsorption constant was applied to determine the fugacity of hydrate phase. The predictive thermodynamic model successfully describes the tendency of phase behavior of methane hydrate in the presence of EMIM-Cl in the range from 0.1 to 0.4 mass fraction with absolute average relative deviation in predicted temperature of 0.70%.

Thermodynamic basis for vapor solubility in ethyl cellulose

The solubility of several gases and vapors in glassy ethyl cellulose (EC) over wide ranges of temperature and pressure is described by means of a thermodynamic model, which specifically accounts for the nonequilibrium volumetric properties of EC. The behaviors of polymer/penetrant mixtures are represented by the well-established nonequilibrium lattice fluid model (NELF) in its latest development, suitable to be used in a pure predictive fashion for the representation of the volume swelling of the polymer matrix, as induced by penetrant sorption. The analysis reveals the ability of the model to describe all the experimental trends, and a sole binary parameter for each polymer/penetrant couple is considered. The NELF model allows the satisfactory prediction of the thermodynamic properties of all polymer/solute systems examined, in the entire range considered for temperature and vapor fugacity.

Vapor–liquid equilibrium of isoamyl alcohol + isoamyl propionate and propionic acid + isoamyl propionate systems at 50.00, 101.33 and 150.00 kPa

In this work, the isobaric vapor–liquid equilibrium (VLE) for the pseudo-binary systems isoamyl alcohol+isoamyl propionate and propionic acid+isoamyl propionate at three different pressures is reported. Measurements were done in a dynamic equilibrium cell (Fischer Labodest VLE 602) at 50.00, 101.33 and 150.00kPa. The experimental data were tested for thermodynamic consistency with point, total area and infinite dilution tests, using the Hayden–O’Connell equation-of-state for the calculation of vapor fugacity coefficients and the Dortmund modified UNIFAC group contribution method for the prediction of excess enthalpies. VLE data were correlated using the NRTL activity model and good agreement with experimental data was observed.

Comparative Study of Cocurrent and Countercurrent Modes of Operation for a Thermal Hydrolyzer in an Industrial Urea Wastewater Treatment Loop

In this work, a comparison of cocurrent and countercurrent modes of operation for an industrial wastewater treatment loop of an industrial urea plant has been carried out. In both modes of operation, a loop with a thermal hydrolyzer is used for urea decomposition, and two desorbers are used for the removal of ammonia and carbon dioxide. In the proposed model, the extended electrolytic UNIQUAC equation is used to describe the nonideality of the liquid phase of the NH3−CO2−H2O−urea system, and the perturbed-hard-sphere (PHS) equation of state is applied to predict the vapor fugacity coefficients. Also, the urea hydrolysis reactors are divided into several continuously stirred tank reactors (CSTRs) and the equilibrium-stage model is applied for modeling of both kinds of reactors and of the desorbers. The simulation results show that countercurrent mode of operation is necessary to achieve new environmental standards and complete treatment. The data predicted using the model were consistent with available plant data, indicating the validity of the model. The impact of different parameters on the performance of the urea wastewater treatment loops has been examined. Overall, this study results in beneficial information about the use of the cocurrent and countercurrent hydrolysis reactors in the urea wastewater treatment process.

Simultaneous Removal of Urea, Ammonia, and Carbon Dioxide from Industrial Wastewater Using a Thermal Hydrolyzer−Separator Loop

In this work, simultaneous removal of urea, ammonia, and carbon dioxide from industrial wastewater was studied via modeling and simulation of a hydrolyzer−separator loop. The extended electrolytic UNIQUAC equation has been used to describe the nonideality of the liquid phase and the perturbed-hard-sphere (PHS) equation of state has been applied to predict the vapor fugacity coefficients. This work also uses a multistage well-mixed model for the liquid and vapor flows with a nonideal rate-based model for urea thermal hydrolyzer. Our study incorporates the reaction rate of urea hydrolysis and takes into account the effects of solution nonideality and backmixing on the reactor performance. The rates of urea reaction are written in terms of activity of reactants. The model provides temperature and flow rate distributions of different components along the height of the hydrolysis reactor and the desorbers. The simulation results have been found to be in good agreement with the plant data indicating the validity of the model. The impact of different parameters on the performance of the wastewater treatment loop has been examined. The results of this work showed that an increase in the inlet temperature of the wastewater and steam flow rate and also decrease the reflux ratio would improve the urea and ammonia removal efficiency.

Treatment of wastewater polluted with urea by counter-current thermal hydrolysis in an industrial urea plant

In this paper, the removal of urea from industrial wastewater by thermal hydrolysis was studied via modeling and simulation of counter-current urea thermal hydrolysis reactor. The features of our proposed model are (1) the use of Nakamura equation of state to predict the vapor fugacity coefficients and UNIQUAC equation to describe the non-ideality of liquid phase, (2) the use of multi-stage well-mixed model for the liquid and vapor flows with non-ideal rate-based model for urea thermal hydrolyser, (3) the reactions are assumed to take place in the liquid phase. The model incorporates reaction rates of urea hydrolysis and takes into account the effects of solution non-ideality and back mixing on the urea thermal hydrolyser performance. The rates of reaction are written in terms of activity of reactants which are determined using a thermodynamic framework for system of NH 3–CO 2–H 2O–urea mixture. The model provides temperature and concentrations distribution of different components in the liquid and vapor phases along the height of urea thermal hydrolyser. The predicted data of the model were consistent with the plant data indicating validity of the model. Also the effects of key parameters on the performance of urea thermal hydrolyser such as the temperature and flow rate of the steam and wastewater were examined. The results of this work show each parameter that causes an increase in temperature level along the urea thermal hydrolyser improves the urea removal efficiency.

Modeling and simulation of high-pressure urea synthesis loop

In this paper, modeling and simulation of high-pressure urea synthesis loop has been studied. The extended electrolytic UNIQUAC equation has been used to describe the nonideality of liquid phase of NH 3–CO 2–H 2O–urea system under high pressure and high temperature, and the perturbed-hard-sphere (PHS) equation of state has been used to predict the vapor fugacity coefficients. The vapor–liquid equilibrium has been treated simultaneously with chemical reactions due to the complex features of the urea synthesis system. A concrete procedure for simulation of the key units and flowsheet of the high-pressure urea synthesis loop has been developed. The equilibrium-stage model has been applied to modeling and simulation of the urea reactor, CO 2 stripper and other key units in the high-pressure loop for urea synthesis, and the simultaneous-modular approach has been adopted to simulate the flowsheet. The simulation results have been found to be in good agreement with the design data from the industry-scale plant. This work provides an effective tool and significant guidance for design or retrofit of urea synthesis process.

Vapor phase activity coefficients and standard state hypothetical vapor fugacities for hydrocarbons

Vapor phase activity coefficients and standard state hypothetical vapor fugacities for hydrocarbons

Liquid phase activity coefficients and standard state hypothetical liquid fugacities for hydrocarbons

AbstractOne method of predicting vaporization equilibrium ratios for the components of a multicomponent mixture is through the use of standard state liquid fugacities, standard state vapor fugacities, liquid phase activity coefficients, and vapor phase activity coefficients. The relationship among these variables will be shown.It is the purpose of this paper to present a method for evaluating the fugacities of the components of a multicomponent liquid mixture which is in equilibrium with its vapors; to present a method for evaluating the standard state fugacities of hypothetical liquids and to disclose these values for methane and ethane up to a reduced temperature of 1.6 and values for propane up to a reduced temperature of 1.3; to present the coincident derived values of the vaporization equilibrium constants, Z factors, and solubility parameters; and to show correlations of these values.