局部组成型的立方转子链状态方程

为进一步改进立方转子链状态方程对混合物汽-液平衡的描述,作者建立了以局部组成概念为基础的新的混合物状态方程,并对42组低压和高压二元汽-液平衡数据(大多为极性体系)进行了关联.结果表明本模型较常规二次混合规则可显著提高关联的精确度并扩大应用范围.当应用于低压强极性体系时,一般可取得优于目前广泛使用的活度系数法所获得的结果.     

含极性抑制剂体系中水合物生成条件的研究

应用两步水合物热力学模型,结合基于局部组成概念的混合规则,将水合物生成条件预测成功地扩展应用于含极性抑制剂体系,计算结果较理想,大量检验结果表明,单流体混合规则不能很好地描述极性体系。同时可以看出,极性体系相对平衡计算的准确性对水合物生成条件预测有很大的影响。     

局部组成型M-H(81)状态方程

为了改进M-H(81)状态方程在含极性和超临界组分体系汽液平衡计算中的应用,作者将局部组成概念和M-H(81)状态方程相结合,导出了局部组成型的M-H(81)状态方程[DDLC M-H(81)];并对45组低压和高压二元汽液平衡数据进行了关联计算.结果表明:对低压极性体系,汽相组成的绝对偏差和常用的活度系数模型相当,而压力的绝对偏差则略好于上述模型.对于高压体系(包括含超临界组分体系),新模型与单流体模型相比,无论是汽相组成还是泡点压,其计算精度都有明显的改进.     

LCVM型混合规则扩展用于多参数状态方程以关联混合物汽液相平衡

基于两参数状态方程提出的LCVM混合规则是将以无穷压力为参考态的HV混合规则与以零压力为参考态的MHV1混合规则线性结合而得的,尽管没有理论基础,但对于计算非极性、极性体系给出了较好的结果.因而研究借鉴获得LCVM混合规则的思路将LCVM混合规则扩展到多参数状态方程中,即将HVOS混合规则与MHV1混合规则进行线性结合,并通过引入两个对比参数λ0,λ∞给出了适合多常数状态方程的新LCVM型混合规则.在新的LCVM型混合规则中,参数δ决定了MHV1和HVOS混合规则的相对贡献,该参数可由模型在高压和低压下拟合二元混合物的泡露点得到,通过拟合得到的值约为0.21;混合规则中的活度系数模型可以利用由低压区关联出的GE模型.采用该新混合规则模型,在较宽的温度与压力范围内,结合Harmens-Knapp(HK)方程对包括非极性体系、极性体系等在内的20种二元混合物进行了相平衡计算.计算的结果与实验数据吻合得很好.该模型与采用VDW混合规则模型的相平衡计算结果比较表明,该模型的关联精度有了很大的提高,可以在较大的温度与压力范围内关联多种体系的汽液相平衡数据.但是在混合规则中,参数b,c是依赖于经验获得,因此还有待于进一步的研究.     

立方型状态方程的混合规则在相平衡计算中的研究

对立方型状态方程中所使用的混合规则及其在相平衡计算中的应用状况做了综述分析。将混合规则按二次型、LC型、DDLC型和UNIWAALS型分别进行了介绍和讨论。总结了各种类型混合规则的优缺点和适用范围,并提出了混合规则今后的发展方向。     

一种新的WS型混合法则

立方形状态方程被广泛应用于相平衡计算中．绝大多数状态方程是结合简单的van der Waals混合法则来进行VLE数据关联的．然而对于应用这些方程关联高度非理想混合物的复杂的相行为,仅用van der waals单维流体混合法则是不够的．甚至在van der Waals混合法则引入另外一个参数都不能够精确地关联含有极性物质的混合物．     

立方型状态方程含过量自由焓模型的新混合规则

提出了在参考压力下将过量自由焓(g~E)模型引入状态方程的修正Huron-Vidal混合规则,由g~E模型确定状态方程中混合物的参数,以SRK方程和Wilson模型为例,取大气压为参考压力,计算了16个体系50组汽液平衡,结果表明本文建议的混合规则可直接使用现有文献报道的常压g~E模型参数由立方型状态方程预测常压汽液平衡,并对直接外推预测高压汽液平衡作了尝试.     

基于SRK方程混合规则修正的烃类混合物相平衡计算研究

为改进SRK方程对烃类混合物相平衡计算的准确性,采用修正方程中系数计算的混合规则,在分析众多混合规则的基础上,采用SR混合规则来计算SRK方程中的系数,基于-型相平衡模型,应用Newton-Raphson迭代算法计算求解,并将计算结果与现场实测数据进行对比分析,结果表明,采用SR混合规则后的SRK状态方程对烃类混合物的相平衡预测精度高,验证了方法的有效性,并且通过计算发现该方法不适合混合物中H2S等酸性气体的相平衡数据计算。     

立方扰动硬链方程

本文通过在SPHC方程中引入拟合Carnahan-Starling硬球方程所得的斥力项,建立了立方型扰动硬链状态方程.由拟合正构烷烃的饱和蒸汽压和液相密度所确定的3个纯组分参数与碳原子数呈良好线性关系.对19种纯物质饱和蒸汽压和液相密度数据计算的平均相对误差分别为1.52%和2.97%;对混合物提出了一种新的混合规则,应用于预测含短链和长链烃类及二氧化碳、硫化氢混合物的高压汽液平衡,优于采用SPHC、SRK和PT方程所得的计算结果.     

二元真实气体混合物剩余焓和剩余熵的计算

混合物流体热力学性质的计算是化工热力学中的一类重要计算。但现有教材中没有给出关于混合物剩余焓和剩余熵的计算公式,缺失了流体热力学性质计算的系统性。本文通过纯气体的剩余焓和剩余熵的计算公式,采用Prausnitz混合规则或Kay混合规则,推导出R-K方程、virial方程,以及普遍化关联法计算二元真实气体混合物剩余焓和剩余熵的公式,并用于具体实例的计算。结果表明,在中、低压下,采用所推导出的三种方法计算二元真实气体混合物剩余焓和剩余熵时,能够得到比较相近的结果,这三种方法是正确可靠的;在高压下,R-K方程和普遍化关联法仍可采用,而virial方程则不再适用。每种方法计算过程繁简不一,但步骤简捷明了,利于学生更好地理解混合物热力学性质的计算过程。     

用MH-81′状态方程模拟液氮洗涤塔

本文采用MH-81′状态方程和与密度无关的局部组成型混合法则,从二元汽-液平衡数据得到的二元相互作用参数,预测了部分液氮洗过程中的二元体系的混合焓,结果满意。采用三对角矩阵方法,对两种不同工况的液氮洗涤塔进行了模拟,计算结果与设计值和实测值符合较好。     

PR方程结合改进的WS混合规则预测汽液平衡

对WS型混合规则加以适当改进提出一种新的G^E型混合规则（MWS型）,并将其与PR状态方程相结合应用于多个二元极性体系汽液平衡数据的预测。结果表明,采用PR方程结合MWS型混合规则预测汽液平衡结果一般优于WS型混合规则,能广泛应用于工程实践。     

PRSV — An improved peng-Robinson equation of state with new mixing rules for strongly nonideal mixtures

Two new composition dependent mixing rules for cubic equations of state are proposed. Both mixing rules contain two adjustable binary parameters and reduce to the conventional one parameter mixing rule when the parameters are equal. Vapor-liquid equilibrium data for mixtures of polar (associated or not) compounds with saturated hydrocarbons and for systems water/alcohol have been used to test the new mixing rules applied to the PRSV cubic equation of state. For these highly nonideal systems, correlation of the data with a new mixing rule of the Van Laar type for the PRSV equation gives better results than those obtained using excess Gibbs energy functions like the Wilson equation, NRTL and UNIQUAC.     

Wong-Sandler新型混合规则应用于MKS状态方程

为了将ＭｏｄｉｆｉｅｄＫｕｍａｒ－Ｓｔａｒｌｉｎｇ立方型状态方程用于近临界及多种类流体混合物的计算，采用作者提出的将Ｗｏｎｇ－Ｓａｎｄｌｅｒ型混合规则推广到普遍化立方型状态方程的方法，建立了改进的ＭＫＳ／２模型。经各类体系的计算考核，ＭＫＳ／２模型对于各类体系的近临界相态行为及非对称体系相平衡计算的改进是显著的。     

Estimation of solubility of solids in supercritical carbon dioxide

Peng-Robinson equation of state(PR EOS)was chosen for modeling the thermodynamic be-havior of supercritical(SC)-CO_2/Solid systems.The necessary critical constants and acentric factorof the solute were obtained by the Sigmund and Trebble(1992)method based on the molecular weightand boiling temperature,and the vapor pressure of the solute was calculated by its meltingtemperature and heat of fusion.This approach compared very favorably with the conventional corres-ponding state theory,but without using critical constants and vapor pressure of solutes.Four mixingrules were tested for the calculation of solid solubility in SC-CO_2.van der Waals(vdW)mixing rulewith one parameter was considered to be most suitable for the estimation of solubility.A simplecorrelation was developed for the SC-CO_2/solid binary interaction coefficient k_(ij) with the meltingtemperature of pure solutes.The solubilities of solids in SC-CO_2 were estimated for eleven binarysystems at various temperatures,the total absolute average     

A modification of Wong-Sandler mixing rule for the prediction of vapor-liquid equilibria in binary asymmetric systems

Systems consisting of light components and heavy hydrocarbons are highly asymmetric and industrially important. Design and control of facilities for separation and purification of such mixtures require vapor-liquid equilibrium data. Coupling of the cubic equation of state (EOS) with excess Gibbs energy models (EOS/G ^ex models) failed to represent the vapor-liquid equilibria (VLE) of such systems accurately. The main purpose of this work is to present a modification of Wong-Sandler mixing rule with using the composition dependent binary interaction parameter. Vaporliquid equilibria for 30 binary systems are calculated using the SRK equation of state with proposed model and Wong-Sandler mixing rule. Calculated pressures and mole fractions of vapor phase are compared with experimental data. The average absolute percentage deviation indicates that error involved in the application of modified Wong-Sandler model is less than Wong-Sandler model in most cases.     

On the linear approximation of mixture internal energies of departure

Direct Monte Carlo simulation of internal energies of departure for binary mixtures of geological interest are gathered and compared to those calculated using a linear mixing rule. Simulation results for gas–oil, oil–oil, and oil–water mixtures show that the linear mixing rule used in the Gibbs–Helmholtz Constrained (GHC) equation of state framework gives accurate approximations of binary mixture internal energies of departure. A flowchart for computing internal energies of departure using Monte Carlo simulation is included along with a sensitivity analysis for the GHC mixture energy parameter with respect to uncertainty in internal energies of departure.     

A GE/Equation of State Mixing Rule for Vapor-Liquid Equilibria

A new excess Gibbs free energy/equation of state type mixing 0rule was derived byremoving the infinite pressure boundary condition imposed by Wong and Sandler.The mixing rulewas extensively tested in terms of a comprehensive data base,consisting of 52 simple nonpolar-nonpolar,carbon dioxide containing,hydrocarbon-hydrocarbon,CFC,polar-polar,nonpolar-polarbinary and multicomponent systems.Focused on the complete predictive capability,a comparisonbetween the Wong-Sandler and the mixing rule proposed was conducted.The results indicate that thenew mixing rule is in general superior to the Wong-Sandler's,and the binary interaction parameteras required by the latter is removed,which reduces computing effort and is reliable in predictions ofvapor-liquid equilibria from low pressures to high pressures.     

非对称烃类体系高压汽液平衡的预测

本文基于London色散力理论和Pitzer对比态原理等统计力学基础提出了一个RKS方程改进的混合规则,进而导出一个非对称烃类体系通用二元相互作用参数的表达式:使用该RKS方程改进的混合规则,较满意地预测了21个非对称烃类的高压汽液平衡,从而显著地提高了原RKS方程假定K_(ij)=0时的预测精度。     

AN EMPIRICAL VIRIAL-LIKE CUBIC EQUATION OF STATE FOR PHASE EQUILIBRIUM CALCULATIONS

An empirical cubic equation of state(EOS) was obtained by truncating the virial expansion in reciprocal of molar volume after the third term. The constants of the EOS was generalized in terms of critical temperature, critical pressure and Pitzer's acentric factor.

In pure component applications the EOS exhibited a performance comparable to Peng-Robinson (1976) EOS in the reduced temperature range of 0.5 to 1. The present EOS tends to predict better saturation liquid volumes at reduced temperatures below 0.8, and better estimations for second virial coefficient at high reduced temperatures.

The EOS was successfully employed for vapor liquid equilibrium calculations for some mixtures of normal or slightly polar fluids with traditional one binary parameter mixing rule at moderately high pressures. At low reduced temperatures, where conventional one adjustable parameter applications of the cubic equations compare unfavorably with dual methods based on excess Gibbs energy functions for the liquid phase, a new two constant mixing rule introduced by Stryjek and Vera (1986) was employed for the present equation of state.