状态方程和对应态计算天然气气液平衡方法的比较

本文以某天然气长输管道中的输送介质为研究对象,分别应用Peng-Robinson,Redlich-Kwong-Soave状态方程模型和Lee-Kesler对应态模型对天然气的气液相平衡进行计算。在使用气相色谱仪测定获得输送介质组成成分数据后,利用Hysys计算模拟得出了不同模型中的天然气气液相平衡。对比模拟结果表明,Lee-Kesler应状态方程相比于其他两类状态方程给出了更保守精准的模拟结果。     

β-苯乙醇与乙醇汽液相平衡数据测定与关联

利用沸点仪测定β-苯乙醇与乙醇的汽液相平衡数据,同时实验测得的β-苯乙醇的饱和蒸汽压与温度,采用Lee-Kesler法估算不同温度下β-苯乙醇的饱和蒸气压,得到β-苯乙醇的Antoine方程,应用Wilson方程进行关联,获得相应的模型参数,为β-苯乙醇的分离提纯工艺提供了基础数据与理论依据。     

Dieterici气体对比态形式的转换温度

运用对比态形式的Dieterici状态方程,分析和导出焦-汤效应的对比转换温度与对比压强关系式,并且通过Matlab软件绘制Dieterici方程在不同温度指数的对比转换曲线,将其与Miller方程的对比转换曲线进行比较分析。     

Lee-Kesler方程的计算机应用研究

本文完成了Lee-Kesler对比状态方程的计算机解法,以此为基础进而完成了Lee-Kesler法进行混合物汽液平衡性质计算的程序系统。对迭代初值、收敛性、迭代精度及其他有关情况做了讨论。从实验数据出发,通过参数优化将Lee-Kesler法从烃类扩展到某些特殊体系(如含氢、氮、氨和水等的体系),初步取得了一些满意可用的结果,为利用数据库扩展各种状态方程的应用范围摸索了一条途径。     

对应态基团贡献法(CSGC)估算有机物蒸汽压

通过引入拟临界性质的概念，将对应态原理与基团贡献方法相结合，提出一种新的物性估算方法－－对应态基团贡献法（Corresponding State Group Contribution,简称CSGC）。将其与Riedel方程相结合，提出新的蒸汽压估算方程（CSGC－RE方程），用于纯物质饱和蒸汽压的估算。经过对包括各类烃、含氧化合物、含氮化合物、含卤素化合物等20类349种物质5254个数据点的回归计算得到的87种基团的贡献参数值，总误差1．35％。为说明该方程的准确性，还给出了Riedel式、Lee-Kesler式以及Riedel-Plank-Miller式计算结果的比较。新模型既有对应态法简单的形式，又具有基团贡献法广泛的预测能力，仅需要物质极易获得的正常沸点数据，便可准确估算物质的蒸汽压，是一种十分有效的有机物物性估算方法。     

甲苯的热力性质计算

甲苯是适合于烟气余热动力回收的耐高温工质。本文采用Lee-Kesler方程进行甲苯的热力状态性质计算,为工程设计提供了实用的图表。     

改进对应态基团贡献法用于纯物质偏心因子估算

将对应态基团贡献法(CSGC)提出的拟临界性质应用于Lee-Kesler方程,提出新的纯物质偏心因子ω估算方程(CSGC-LK方程),对包括烷烃、烯烃、炔烃、卤代烷烃、环烷烃、环烯烃、二烯烃、醇、醚、酮、酸与酸酐、醛、酯、含硫化合物、含氮化合物、含氧多基化合物、芳烃、卤代苯和酚等20类376种物质偏心因子数据采用非线性最小二乘法进行关联,得到CSGC-LK方程的8个常数值和69种基团贡献参数值,ω总平均相对误差为5.47%。为进一步考察CSGC-LK方程的预测精度和适用范围,对7种未参加回归物质的偏心因子进行了预测,ω总平均误差为3.46%,预测精度良好。     

基于Redlieh-Kwong对比态方程的天然气压缩因子计算

对Redlieh-Kwong对比态方程进行了推导,并将AGA8报告中30组压缩因子实测值与混合物天然气压缩因子的计算值进行了对比分析,计算误差小于1. 20%。最后得到了压力、温度对天然气压缩因子的影响规律。     

高分子材料在拉—扭负荷下的相互作用曲线

本文引用由 Von Mises 屈服条件、Hooke 法则及 Reuss 方程导出的相互作用曲线方程、广义相互作用曲线方程及应力途径方程,对高分子材料 PEEK、PES、PC、POM、PE 等进行了常温和变温下的理论曲线与实验曲线的对比检验。     

建立气井二项式产能方程的一种新方法

气井产能方程能够直接描述井底流动压力和产量的关系。在建立气井产能方程的传统方法中,需要关井测试气藏的地层压力。本文不需要地层压力,只通过井底流压——产气量数据,利用线性回归方法,即可建立二项式产能方程。通过与常规的作图法和最小二乘法对比表明,本方法可靠。     

Lee-Kesler状态方程在含极性组分物系粘度计算中的应用

将Ｌｅｅ Ｋｅｓｌｅｒ 状态方程用于Ｄｅａｎ Ｓｔｉｅｌ 粘度方程中求解密度值，计算了８ 组含极性组分的液体混合物粘度，得出较准确的计算结果。     

EVALUATION OF THE ORIGINAL AND THE MODIFIED LEE-KESLER EQUATION OF STATE

In this work, the Lee-Kesler equation of state has been used together with the extended corresponding states principle. In order to improve the predictability of the equation in a more narrow acentric factor range, two new reference fluids have been chosen. The parameters in the Lee-Kesler equation have been estimated for the two reference fluids, CFC12 (dichlorodifluoromethane) and HFC134a (1,1,1,2-tetrafluoroethane), with the Error-in-Variables Model. This model allows both dependent and independent variables to be subject to errors.

Calculations have been made for the two reference fluids as well as for other compounds, and the predicted thermodynamic properties have been compared with experimental values. Comparative calculations have also been carried out for some of the previously suggested modifications of the Lee-Kesler correlation.     

A new generalized corresponding-states equation of state for the extension of the Lee-Kesler equation to fluids consisting of polar and larger nonpolar molecules

The Lee-Kesler equation of state for the thermodynamic properties of small nonpolar fluids is extended to all fluids consisting of polar and larger nonpolar molecules, based on the general corresponding-states theory for highly nonspherical fluids. The thermodynamic functions are represented by an analytical equation of state. The results for polar fluids are substantially better than those obtainable from other currently available methods, while the results for nonpolar fluids are equivalent to and mostly better than those obtained by the Lee-Kesler method. The input data required are the critical temperature, the critical volume, the acentric factor and the aspherical factor, which is related to the critical compression factor; the critical volume is therefore required in the present method. The method developed in this work shows good accuracy for 15 representative nonpolar, polar, hydrogen bonding and associating fluids and provides a simple method for industrial applications. Average deviations for the compressibility factor, the heat capacity and the speed of sound for six nonpolar and nine polar fluids from the new equation of state are 0.74%, 2.1% and 2.3%, which are about 8 times smaller than those obtained from the Lee-Kesler equation (about 5.6%, 17% and 29%, respectively).     

A MODIFIED LEE-KESLER EQUATION OF STATE FOR REFRIGERANTS

For calculation of the thermodynamic properties of refrigerants it is proposed that the extended corresponding states principle (ECSP) should be used using two specific reference fluids, CFC12 (CCI₂F₂) and HFC134a (CF₃CH₂F), in order to cover the field of interest for most refrigerants. The specific parameters of these refrigerants have been determined for the Lee-Kesler modification of the Benedict-Webb-Rubin equation of state. In the parameter estimation, it has been taken into accounl that all variables are subject to errors by using the so-called Error-in-Variables-Model (EVM). The parameters have been estimated from experimental pressure-volume-temperature data, vapour pressure and saturated liquid and vapour volume data for CFC12 and HFC134a.

The extended corresponding states principle proposed in this work with CFC12 and HFC134a as reference fluids has been used in calculations of the thermodynamic properties of a number of refrigerants. In comparison with the original Lee-Kesler equation this concept gives improved results in calculations of vapour pressure and liquid volume.     

Calculating the dynamic viscosity of paraffins using the Lee-Kesler equation

A model for calculating the viscosity of individual paraffins that constitute the major part of the products of the Fischer-Tropsch synthesis is developed on the basis of the fluctuation hypothesis of the formation of vacancies in the liquid phase. All of the thermodynamic parameters of a substance and the energy barrier of the formation of vacancies are calculated using the Lee-Kesler equation of state. The results of the calculations of the viscosity of heavy paraffins are compared with the experimental data from published works.     

A FOUR-PARAMETER EXTENSION OF MODIFIED LEE-KESLER EQUATION OF STATE

A modified Lee-Kesler equation of state has been proposed to improve the accuracy for the subcooled and saturated liquid regions of normal fluids. It is further extended to polar fluids by the addition of a fourth parameter X. The extended equation has been found to be reliable over a wide vapor and liquid regions for polar fluids and it is easy for computer use. Fourteen kinds of normal fluids and twelve kinds of polar fluids have been tested. The total average absolute deviations for the normal fluids and polar fluids are 0.79% and 1.68% over the range of T_r = 0.3 to 4 and P_r - 0.01 to 10.     

A FOUR-PARAMETER EXTENSION OF MODIFIED LEE-KESLER EQUATION OF STATE

A modified Lee-Kesler equation of state has been proposed to improve the accuracy for the subcooled and saturated liquid regions of normal fluids. It is further extended to polar fluids by the addition of a fourth parameter X. The extended equation has been found to be reliable over a wide vapor and liquid regions for polar fluids and it is easy for computer use. Fourteen kinds of normal fluids and twelve kinds of polar fluids have been tested. The total average absolute deviations for the normal fluids and polar fluids are 0.79% and 1.68% over the range of T_r = 0.3 to 4 and P_r - 0.01 to 10.     

含氢混合气体的压缩因子

在高压低温下,含氢混合气体已极大地偏离理想气体,因而必须要求正确地确定这种混合气体的P-V-T关系。本文对混合气体假临界常数的Kay方法进行修正,用此计算对比参数,就可把LK方程延伸使用于含氢混合气体。文中分别用修正Kay方法和GCP方法所得的假临界常数和LK方程对H_2-CH_4-N_2、N_2-H_2、H_2-N_2-CO_2-CO-CH_4等系统的压缩因子进行了计算,并和文献中的实验值作了比较。结果表明,用本文修正Kay方法所得计算值与实验值有更好程度的吻合。     

Modeling the thermal and physical properties of liquid and gas mixtures of Fischer–Tropsch synthesis products

The method of pseudocritical thermodynamic parameters and the Lee-Kesler equation of state are used for calculating the thermal and physical properties of a solution and a mixture of gaseous paraffins that are major constituents of Fischer-Tropsch synthesis products. The dynamic viscosities of a solution and a vapor are modeled using an original procedure proposed by the authors. A surface tension is calculated by the parachor method. The composition of liquid and gaseous products is found using a stable iteration scheme proposed by the authors. The model is tested by a comparison with experimental data from the literature for model mixtures of hydrocarbons. The results of calculating the composition and thermophysical properties of a mixture of paraffins that model the composition of synthesis products at different values of the chain propagation parameter, temperatures, and pressures are presented.     

Thermodynamics of wax formation in the fischer-tropsch synthesis products

A new method is suggested for calculating the thermodynamic equilibrium in a multicomponent multiphase system without chemical reactions. This method is based on ideas of statistical physics and non-equilibrium thermodynamics and includes numerical minimization of the Gibbs energy of the complex system. Component concentrations and the physically realizable roots of the equation of state are calculated as the steady state solutions of the set of ordinary differential equations that is implied by the procedure of seeking the probability maximum for the realization of the equilibrium distribution. The approach developed here is used to calculate the equilibrium distribution of the concentrations of vaporous, liquid, and solid substances in the Fischer-Tropsch synthesis products. A thermodynamic model of the formation of solid paraffins from the synthesis products is presented. The calculation of the properties of pure substances and liquid and gaseous products is based on the Lee-Kesler equation of state. The wax formation thermodynamics is considered in the regular solid solution approximation (Hildebrand-Scott model) and in the solid solution approximation taking into account the nonideality of the system (NRTL model). The calculated mass fractions of vaporous, liquid, and solid synthesis products are presented as a function of temperature for different values of the chain propagation constant.