Tao-Mason状态方程扩展用于重正烷烃(英文)

In our previous paper we extended the Tao and Mason equation of state (TM EOS) to refrigerant fluids, using the speed of sound data. This is a continuation for evaluating TM EOS in predicting PVT properties of heavy n-alkanes. Liquid density of long-chain n-alkane systems from C 9 to C 20 have been calculated using an analytical equation of state based on the statistical-mechanical perturbation theory. The second virial coefficients of these n-alkanes are scarce and there is no accurate potential energy function for their theoretical calculation. In this work the second virial coefficients are calculated using a corresponding state correlation based on surface tension and liquid density at the freezing point. The deviation of calculated densities of these alkanes is within 0.5% from experimental data. The densities of n-alkanes obtained from the TM EOS are compared with those calculated from Ihm-Song-Mason equation of state and the corresponding-states liquid densities (COSTALD). Our results are in favor of the preference of the TM EOS over other two equations of state.     

一个新α-函数用于Peng-Robinson状态方程:应用于天然气(英文)

Cubic equations of state （EOSs） are simple and easy at calculation. One way of improving the accuracy of a cubic EOS is through the modification of temperature-dependent energy parameter by using alpha-function. The industrial applications of natural gas are very wide and as a result, prediction of thermodynamic properties and phase behavior of natural gas is an important part of design for such processes. In this work we develop a newα-function for the Peng-Robinson （PR） EOS with the parameters optimized especially for natural gas components. The parameters are generalized as a linear function of acentric factor. The results are compared to the predictions from original PR EOS and otherα-functions in literature. It is shown that the newα-function presents a good accu-racy with the average deviation of 1.42%for natural gas components.     

Molecular thermodynamic model for fluids containing associated molecules

With the statistical mechanical theory for square-well-chain fluids as the basic princi-ples,a molecular thermodynamic model including expressions for the Helmholtz function and thecompressibility factor for associated square-well-chain fluids has been developed.Employment ofthe shield-sticky concept enables the corporation of association bonds between in the model.Good agreement with computer-simulation results for dimer-linear quadrimer systems is obtained.Satisfactory correlation for vapor pressures and saturated liquid volumes of pure substances con-taining associated molecules(such as carboxylic acids,alcohols,amines,water,etc.)with four mo-lecular parameters indicates the applicability of the model.     

EQQUATION OF STATE BASED HYDRATE MODEL FOR NATURAL GAS SYSTEMS CONTAINING BRINE AND POLAR INHIBITOR

A new thermodynamic model for gas hydrates was established by combining the modified Patel-Teja equation of state proposed for aqueous electrolyte systems and the simplified Holder -John multi -shell hydrate model. The new hydrate model is capable of predicting the hydrate formation/dissociation conditions of natural gas systems containing pure water/formation water (brine) and polar inhibitor without using activity coefficient model. Extensive test results indicate very encouraging results.     

The Performance of EOS Models in the Prediction of Vapor-Liquid Equilibria in Asymmetric Natural Gas Mixtures

The aim of this work is to apply cubic equations of state (EOS) to vapor-liquid equilibria calculations of gas- heavy hydrocarbon systems, which are asymmetric in molecular size and are usually found in natural gases. Investigation has been done to test the validity of the original PSRK and the cubic simplified perturbed hard-chain (CSPHC) models for global phase diagrams. The calculation results show that both equations overpredict vapor pressure in the near critical region. In the prediction of the solubilities of high molecular weight (MW) hydrocarbons in the natural gas, the PSRK model gives good agreement for the dew point pressure-vapor composition diagrams. Adjustment of the pure component parameters of the CSPHC EOS for heavy components to fit the vapor-liquid equilibrium (VLE) data has been proved to give significant promoting in prediction accuracy. However, further improvement of a van der Waals EOS, such as SRK, PT and DG models for the asymmetric systems by adjusting the three pure component properties, Tc, pc and ω, did not achieve satisfactory results for heavy components.     

利用PR状态方程计算临界终点

In the design of chemical processes, such as catalytic cracking of bitumen and heavy oil, the knowledge of phase behavior at the critical endpoint is essential. Based on the PR equation of state, the algorithm developed by Heidemann and Khalil for calculating critical properties was used to compute critical points. An algorithm for determining the equilibrium phase of the critical point using the tangent plane criterion was developed, and was used to calculate the critical endpoints of different mixtures, including non-polar, polar and associating systems. The critical endpoint, representing the type of the phase behavior, was employed to fit the interaction parameter of mixtures in critical state at high pressure. Lines of critical endpoints for ternary mixtures were also determined with the algorithm.     

立方型状态方程结合Eyring理论在液体混合物黏度计算中的应用

Cubic equations of state (EOS) have been combined with the absolute rate theory of Eyring to calculate viscosities of liquid mixtures. A modified Huron Vidal gE-mixing rule is employed in the calculation and in comparison with the van Laar and the Redlich-Kister-type mixing rule. The EOS method gives an accurate correlation of liquid viscosities with an overall average deviation less than 1% for 67 binary systems including aqueous solutions. It is also successful in extrapolating viscosity data over a certain temperature range using parameters obtained from the isotherm at a given temperature and in predicting viscosities of ternary solutions from binary parameters for either polar or associated systems.     

EQUATIONS OF STATE FOR HARD-SPHERE CHAIN FLUIDS AND SQUARE-WELL CHAIN FLUIDS

Based on the statistical theory for chemical association,equations of state for hard-spherechain fluids(HSCFs)and square-well chain fluids(SWCFs)can be derived through the n-particlecavity correlation function(CCF)of the corresponding reference system,where n is the chain lengthor the number of segments of a chain molecule.The reference system is a fluid composed of only cor-responding monomers.In this work,the n-particle CCF is approximated by a product of effectivetwo-particle CCFs which accounts for correlations in nearest-neighbour and next-to-nearest-neighboursegment pairs.The CCFs for SWCFs may be expressed by a product of the corresponding functionfor HSCFs and a perturbation term originated from the square-well attractive potential.All these ef-fective two-particle CCFs and perturbation terms are density dependent.The dependence is determinedmainly by using computer-simulation results.The obtained equations can excellently describecompressibility factors and second Virial coefficients for HSCFs     

303.15 K下氯化钙和氯化铵盐的溶解对甲醇+苯混合物焓的影响(英文)

The effect of two dissolved inorganic salts, cadmium chloride CdCl2 and ammonium chloride NH4Cl, on the excess enthalpy of mixing (HE) of the binary system methanol + benzene measured at 303.15 K using an isothermal displacement calorimeter with vapor space is investigated in the present work. Compared to the salt-free system, a decreasing trend in the endothermicity of HE values is significant with the addition of CdCl2 salt but the decrease in the HE values is insignificantly smaller with the addition of NH4Cl salt. The experimental values of the enthalpy of mixing are fitted into a Redlich-Kister equation and the deviations in the val-ues and the parameters are reported. The importance of the solute-solvent interactions and the solvent-solvent interactions are dem-onstrated from the increasing excess enthalpy of mixing values in the positive direction with the increase of salt concentration.     

10千瓦级分布式天然气-质子交换膜燃料电池示范电站(英文)

A 10 kW-scale natural gas fueled proton exchange membrane fuel cell (PEMFC) distributed power plant is presented in this paper, which is designed for cogeneration of power and heat. With homemade catalysts for CO removal in a two-stage methanation process and integrated reactor in the fuel processing system, the reformed fuel with CO molar fraction less than 105 is obtained for the fuel cell stack. Based on Matlab/Simulink/Stateflow and xPC Target platform, a rapid control prototype (RCP) is developed for real-time condition management, signal tracking and parameter tuning, data storing, and man-machine interaction. In a typical running with 4.3 kW stack power, the hydrogen production efficiency, gross power generation efficiency and heat recovery efficiency approach to 76%, 41% and 50%, respectively. The peak stack power reaches 7.3 kW. Though there is still considerable distance to long-term operation at 10 kW-scale net power generation, it is a milestone for the PEMFC-based stationary application in China.     

Equation of state representation of aqueous mixtures using an association model

A previously proposed association equation of state (AEOS) (Anderko, 1991) for aqueous mixtures is modified to extend its applicability to a wider range of temperatures and pressures. In the AEOS, the compressibility factor is subdivided into two parts; physical and chemical. The physical part, in this work, is represented by the Peng-Robinson (PR) (1976a) EOS for nonpolar compounds. Other cubic EOS can be used for this purpose with little effect on results. The chemical part is expressed by an empirical association model. The improved association model enables the AEOS to reproduce accurately the total compressibility of pure liquid water along the saturation line. Incorporation of the new association model in the PR-EOS allows the combined model to calculate accurately the phase behavior of water/hydrocarbons and water/nonhydrocarbons in VLE, LLE, and VLLE regions.     

Prediction of the phase behavior of gas condensates using Patel-Teja equation of state and gamma distribution function

The three-parameter Petal-Teja equation of state coupled with a characterization proceduref0r C_(7 )-fraction based on gamma distribution function was employed to predict the phase behaviorof eight gas condensates.The lumping of the subdivided single carbon number(SCN)hydrocarbons inthe plus-fraction and the choice of empirical correlations for calculating the critical properties andacentric factor of SCN hydrocarbons were discussed.     

Extension to mixtures of two robust hard‐sphere equations of state satisfying the ordered close‐packed limit

Two new hard‐sphere EOS are proposed and tested using the same attractive potential terms used by the SAFT EOS. Generalized expressions for the pair RDF at contact value, the compressibility factor, and the excess chemical potentials have been derived. Extension to mixtures is tested using three mixing rules for multicomponent hard‐sphere fluids. The proposed EOS combined with the Santos et al. and the Barrio‐Solana mixing rules reproduced the compressibility factors and the excess chemical potentials more accurately than the Boublik‐Mansoori‐Camahan‐Starling‐Leland (BMCSL) EOS. However the pair RDF at contact value had larger deviations than those obtained with the BMCSL EOS. The combination of the proposed equations and the Barrio‐Solana mixing rule gave an accurate reproduction of the compressibility factor for binary hard‐sphere fluids with high diameter ratio even in the low concentration regions of the larger spheres.     

A three-parameter cubic equation of state for fluids and fluid mixtures

A new cubic equation of state with three parameters is developed. The substance-dependent critical compressibility factor, ζ, and the temperature-dependent parameter, α, were correlated in terms of the acentric factor and reduced temperature. The P-V-T relationships, vapor pressures, volumes, and enthalpy departures of pure substances, and the compressibility factors, enthalpy departures, and vapor-liquid equilibria of mixtures were calculated with the proposed equation. Comparison of the calculated results with experimental data shows that the proposed equation is accurate enough to be applied for design purposes.     

Extension of Tao-Mason Equation of State to Heavy n-Alkanes

In our previous paper we extended the Tao and Mason equation of state (TM EOS) to refrigerant fluids, using the speed of sound data. This is a continuation for evaluating TM EOS in predicting PVT prope...     

状态方程外推法测算碳酸二甲酯的密度

提出了利用液体状态方程测定不同温度、压强下碳酸二甲酯密度的外推法.首先实验测量出3种不同温度(283.15,313.15,343.15 K)下碳酸二甲酯的各10组压强和密度数据,然后运用Goharshadi等提出的密度方程对这些数据进行线性拟合,最后利用拟合出的方程参数外推计算了其他多种温度(278.15-353.15...     

A new model for the surface tension of binary and ternary liquid mixtures based on Peng- Robinson equation of state

Based on the surface chemical potential and Peng-Robinson equation of state,a newmodel is proposed to predict and correlate the surface tensions of binary and ternary liquid mix-tures.Using this method,the surface tensions of 73 binary and 8 ternary systems are calculatedwith average relative deviations 1.35% and 3.52% respectively.The proposed model is simple, re-liable and accurate.     

Phase equilibria calculations for ill-defined mixtures using the prsv equation of state

A method for the calculation of vapor-liquid equilibria (VLE) for multicomponent systems using continuous thermodynamics is presented. The Extended Spline Fit Technique (ESFT) is used to represent the molar distribution curve of petroleum fluids. A continuous version of the Peng-Robinson-Stryjek-Vera (PRSV) equation of state (EOS) with Generalized Single Carbon Number Properties (GSCNP) is utilized. For continuously distributed components, following the suggestion of Hendriks (1987), the number of equations solved is reduced through integration over the range of the distributing variable using Legendre-Gauss quadrature. Integrated equations are solved using accelerated successive substitution. Flash, dew and bubble point calculations for an imaginary and a real system yield satisfactory results.