液体饱和蒸气压的测定实验的讨论

本文介绍了我们采用传统仪器,在仪器简单且用量少、成本低的情况下,做好液体饱和蒸气压测定实验的一些经验和方法.     

饱和蒸气压安托万公式常数的计算

<正> 为了计算纯物质在各种温度下的饱和蒸气压,许多学者进行了研究,提出了很多公式,安托万公式是最著名的简便公式。该公式不但适用的温度范围广泛,而且对极性分子和非极性分子都可以使用,甚至还可以在临界温度以外计算虚拟值,在工程计算中得到了广泛的应用。在许多化工模拟中,饱和蒸气压的计算都是以安托万公式为准的。在应用该公式时,需要根据不同温度范围内的饱和蒸气压实验数据回归出三个常数,计算过程比较复杂。D. G. Miller提出用最小二乘法结合摆动追逐方法计算出三个常数。这种方法可以在计算机上实现,但使用不便,而且求解速度较慢。唐宏清提出用最优化方法计算安托万公式中的三个常数。     

液体混合物密度的计算

求取液体密度的经典式为: 式中: ρ、ρ_c——饱和液的密度,临界密度[克/毫升] V、V_c——饱和液克分子比容,临界克分子比容[升/克分子] α、β——(1)式的系数 T_r——对比温度(T_r=T/(T_c))     

计算液体密度的方程

<正> 有机化合物的饱和液体密度用修正的Rackett方程表示为温度的函数。 包括烃类、氧、氮、卤素和硫化物在内的大约700种重要有机化合物的饱和液体密度已经给出。这些密度可用Rackett方程的修正     

多元醇和多元酚饱和液体密度的关联

鉴于目前文献上尚无适合于计算多元醇和多元酚饱和液体密度的方法,笔者在修正的Rackett方程和Campbell-Thodos关系式的基础上,根据对多元醇和多元酚饱和液体密度实验数据的分析,回归出了若干常用多元醇和多元酚的修正Rackett方程常数ZRA的数据,利用ZRA参数数据,计算了10种多元醇和多元酚在不同温度下的饱和液体密度,82个数据点总平均相对误差0.562%。     

液化石油气密度、蒸气压计算标准及方法探析

按照GB11174-2011液化石油气产品标准[1],液化石油气"密度"指标可采用SH/T0221和GB/T1 2 5 7 6两种标准检测方法(其中S H/T0 2 2 1标准规定了使用压力密度计仪器测定方法),"蒸气压"采用G B/T1 2 5 7 6标准检测方法,本文依据G B/T1 2 5 7 6同一个标准对液化石油气密度、蒸气压的计算方法进行阐述,同时对液化石油气中不含二甲醚和含有二甲醚[2]两种不同情况下的密度、蒸气压计算的具体事例进行了描述。     

水、乙醇和乙酸乙酯液体饱和蒸气压测定实验比较

当前高校实验研究正朝着绿色环保、经济可行等方向发展,对于物理化学实验中的经典实验--液体饱和蒸气压测定,实验试剂的选择也应符合该发展趋势。有研究报道利用水或乙醇等试剂代替苯等对环境污染较大的有机试剂,但未见对这些试剂进行对比研究。本文选择水、乙醇和乙酸乙酯作为实验试剂,从绿色环保、经济性、可操作性和实验误差等几个方面对三种物质的液体饱和蒸气压测定实验进行比较。结果表明三种物质各有优劣,相对而言水和乙醇具有更多优越性,更适合作液体饱和蒸气压测定实验的试剂。     

液体饱和蒸气压测定实验数据的处理——Visual FoxPro编程

用静态法测定液体在不同温度下的饱和蒸汽压，可以分别用作图法和计算法求得在所测温度范围内的平均摩尔汽化热。编辑Visual FoxPro程序，用计算机处理数据代替手工处理，求摩尔汽化热和相对误差，这样可以准确快速的对实验数据进行处理，得出实验结果，直观的看出实验的可信度，给实验的数据处理带来很大方便。     

CALCULATION OF VAPOR LIQUID EQUILIBRIUM AND EXCESS ENTHALPY WITH THE UNIQUAC EQUATION

The UNIQUAC equation was used for calculation of vapor liquid equilibrium (VLE)as well as excess enthalpy (h^E). Four sets of binary interaction parameters were applied: first, parameters estimated only from VLE data, then parameters from h^E data for both the original UNIQUAC equation and the Anderson modification, and finally parameters estimated from h^E and VLE data simultaneously. Calculations were performed for seven binary systems with polar components, representing different h^E behavior. The cross-prediction of h^E from VLE data works better than the reversed prediction. The model with parameters estimated simultaneously to both kinds of data can be applied successfully to both kinds of calculations, but it is a compromise between the models estimated from one kind of data.     

CALCULATION OF VAPOR LIQUID EQUILIBRIUM AND EXCESS ENTHALPY WITH THE UNIQUAC EQUATION

The UNIQUAC equation was used for calculation of vapor liquid equilibrium (VLE)as well as excess enthalpy (h^E). Four sets of binary interaction parameters were applied: first, parameters estimated only from VLE data, then parameters from h^E data for both the original UNIQUAC equation and the Anderson modification, and finally parameters estimated from h^E and VLE data simultaneously. Calculations were performed for seven binary systems with polar components, representing different h^E behavior. The cross-prediction of h^E from VLE data works better than the reversed prediction. The model with parameters estimated simultaneously to both kinds of data can be applied successfully to both kinds of calculations, but it is a compromise between the models estimated from one kind of data.     

垂直上升绝热管内汽液两相流截面含汽率的确定

本文提出在蒸发过程中汽、液两相流的流动机构为泡状流和弹状流。根据汽泡、汽弹在静止液中的上升速度,求得了上升流体中汽泡和汽弹的上升速度。得出泡状流和弹状流截面含汽率的计算式。用γ射线法对蒸发过程中汽、液两相流截面含汽率进行测试,并确定了式中的待定系数。     

CALCULATION OF VAPOR-LIQUID EQUILIBRIA AND SATURATED LIQUID VOLUMES FOR WATER-AMMONIA MIXTURES

The approach of using T, at ΔZ= Z^s _vZ^{s L} = 0.5 for a balanced representation of saturated volumes (V^{s L} and V^{s Vs L}( of pure components has been extended from non-polar fluids to water and ammonia. For the mixtures of these two compounds, the average absolute percentage deviation in the calculated V ^{s L} values is less than 2% without affecting the representation of vapor-liquid equilibrium values.     

HYDRODYNAMICS OF BUBBLE COLUMNS WITH TWO IMMISCIBLE LIQUID PHASES

An experimental study of hydrodynamic parameters of bubble columns with the presence of two immiscible liquid phases, water and kerosene, was performed. The solid used consisted of glass beads with a narrow size distribution. The analysis was based on the determination of global gas holdups and phases distribution along the length of the column in the semibatch mode of operation. The results show thai the presence of two immiscible liquid phases significantly reduces the gas holdup in the bubble column as compared to the results obtained with pure aqueous and organic liquid phases. The distribution of solid phase in a slurry bubble column is drastically affected by the presence of immiscible liquid phases, and exhibits a qualitatively different behavior when compared lo systems with one liquid phase. The addition of small amounts of aqueous phase to a slurry bubble column in which the liquid phase is kerosene results in the sedimentation of the solid. As the amount of aqueous phase added is increased, the solid fluidizes yielding almost flat concentration profiles.     

SIMULATION OF THERMALLY-COUPLED DISTILLATION PROCESSES WITH TWO LIQUID PHASES

This paper modifies a mathematical model for distillation with two liquid phases so as to suit for thermally coupleddistillation with two liquid phases and advances an algorithm based upon the modified Naphtali-Sandholm method.Thestructures of Jacobi matrix and its submatrices of all types are given.The multiple phase flash method combined with acomparison of free energies for determination of the liquid phase split in stage is used.Seperation of butanol-water-propanol ternary system is employed to justify the method mentioned above.Satisfactory results are obtained.     

CIRCULATION OF GAS AND LIQUID PHASES IN EXTERNAL-LOOP AIRLIFT REACTORS

The effects of the horizontal connection length (0.3 ≤ L_c ≤ 0.6 mrpar;, the cross-sectional area ratio of downcomer-lo-riser (0.28≤A_d/A_r≤0.53rpar;, and the superficial gas velocity on the circulation gas flow rate were studied. The circulation liquid velocity, the downcomer gas holdup, and the bubble size in the downcomer were also investigated. In order to measure the circulation gas flow rate, a gas-liquid separator was installed at the bottom connection between riser and downcomer. Both of the circulation gas flow rale and the circulation liquid velocity strongly depended on the superficial gas velocity as well as the cross-sectional area ratio of downcomer-to-riser and the horizontal connection length. An useful correlation for the circulation gas flow rate was obtained in terms of the superficial gas velocity, the cross-sectional area ratio of downcomer-to-riser and the horizontal connection length.     

液固搅拌槽中固、液相停留时间分布

本文以海沙和自来水为介质研究了在标准搅拌槽内影响固液两相停留时间分布的主要因素,以便比较两相之间的差异,并利用双区模型描述出口流体中固体和液体的停留时间分布。对所建立模型中的参数进行估值后,建立了模型参数与搅拌雷诺数、固体颗粒浓度及搅拌槽几何参数之间的关联式。     

计算液体及其混合物的C_p-C_v的方法

建立了一个能够计算各种温度下液体恒压热容与恒容热容之差的关系式C_p-C_v=RTV~2a/(V~2-AV+B)A和B是两个相关的特性常数,它们的值可由基团贡献法和分子的拓外指数确定.计算结果与实验值相一致.倘若应用A和B的简单混合规则,上述关系式亦适用于液体混合物.     

PERFORMANCE OF FIVE EQUATIONS OF STATE FOR THE PREDICTION OF VLE AND DENSITIES OF NATURAL GAS MIXTURES IN THE DENSE PHASE REGION

This paper examines the degree of uncertainty of five Equations of State (EOS) for the prediction of densities in the dense phase region which is beyond the ranges of pressure and temperature originally specified for these equations. Predicted densities were compared with measured values for different hydrocarbon mixtures including a rich mixture. The results show that the GERG equation of state, originally specified for the range of P -8 C, outperforms all other equations in the region up to P=30 MPa and T > -8 C. In this range, its mean deviation from measured values of densities was found to be less than -0.015% and standard deviation ( ) also less than 0.015%. The AGA-8 equation, which identified several regions of pressures and temperatures with different uncertainties, also performed quite well with a mean deviation of -0.2% and less than 0.4% in the region up to P=30 MPa. The other equations showed relatively high deviation: ~2.7% for BWRS,-5.1% for PR and 2.5% for RKS. Unlike GERG and AGA-8, however, these three equations can also be used to predict the vapour-liquid-equilibrium (VLE). VLE predictions were compared with measured values for eight binary mixtures of methane (C1) and ethane (C2). It is recommended to use PR for VLE prediction, as quite good agreement between measured data and prediction by PR was demonstrated.