一种新的蒸气压方程

提出了一种新的2参数蒸气压方程,并用12种饱和蒸气压实验数据比较完整的典型物质对新方程的外推性与W agner方程、项方程和吴方程进行了比较。结果表明:新方程在三相点方向的外推性具有明显的优势,总体平均偏差为1.05%,而W agner方程、项方程和吴方程的总体平均偏差分别为41.4%,5.20%和5.60%;在临界点方向的外推性略差于W agner方程,与项方程和吴方程相当。尝试仅用4个实验数据点拟合各方程,结果表明:新方程在三相点和临界点方向同时外推的精度明显优于其他方程。     

Parameters for the attractive coefficient of the patel-teja-valderrama equation of state

A three-parameter form of the temperature dependence of the attractive term in cubic van der Waals type equations of state (AS; Almeida et al., 1991; Aznar and Silva-Telles, 1992) has been applied to a generalized equation of state known as the Patel-Teja-Valderrama equation (PTV; Valderrama, 1990). The parameters of the AS model in the PTV equation of state were calculated for 457 substances of different polarity, molecular size, and chemical nature. The parameters were calculated using vapor pressure data determined through accurate equations available in the literature (Wagner 1973, Antoine 1888, Frost and Kalkwarf, 1953). The deviations between the equation of state calculations and vapor pressure information are lower than 0.5% for most fluids. The study shows that both the generalized PTV cubic equation and the AS represent good tools for pressure-temperature calculations in engineering applications.     

A generalized vapor pressure equation for hydrocarbons

A reduced vapor pressure relationship of the following form has been developed: The optimum value of n was established to be 8.00 from vapor pressure data for n-heptane. A method was developed for the determination of the constants A, B, C and D from one reliable vapor pressure point. By this procedure vapor pressures were calculated for 33 hydrocarbons, including saturated and unsaturated paraffins, naphthenes, and aromatics, and were compared with corresponding experimental values. For these substances the overall average deviation between calculated and actual vapor pressure was 0.38% (1879 points). This relationship was also applied to seven additional hydrocarbons not included in its development, and for these substances the resulting average deviation was 0.36% (99 points).     

A vapor pressure equation for heavy compounds

A vapor pressure calculation procedure based on a lattice equation is applied to several compounds. Originally, the method was used to predict low vapor pressures of heavy hydrocarbons. In this work, the method is used at low vapor pressure for nonhydrocarbons, and a modified version is employed at high vapor pressure for n-alkanes. As the procedures require the knowledge of one vapor pressure datum only, they work in a predictive mode. Prediction for hydrocarbons is good and for nonhydrocarbons is poor. Prediction of n-alkanes high vapor pressure is good with an overall average relative absolute deviation under 6 percent.     

An extended critical-scaling equation with a nonlinear order parameter and its use for the fits to vapor/liquid equilibria

A method to extend the region of validity of the critical-scaling equations is presented and is tested by fits to the vapor/liquid equilibria (VLE) of ethane, propane, and n-butane.In this method there are two elements. One of them is to find an appropriate order parameter (OP) and the other one is how to fit the equations to equilibrium data. As for the OP, the nonlinear OP Smith and Ferer proposed [7] has been used. For the critical scaling equations, terms different from those they used have been employed. This leads to better results and physically sounder value of exclusion-volume-like fitting parameter b. As for the fitting method, first the critical parameters, T_c and V_c are determined and then linear regressions for the fits to VLE data have been adopted. Otherwise, nonlinear regressions have to be essentially employed.Pre-determination of T_c and V_c and the different terms for critical scaling equations provide relatively significant advantages; (i) it makes fits to VLE binodals linear, (ii) the exclusion-volume-like fitting parameter b is approximately equal to the van der Waals parameter b_vdW, and (iii) the fits are in excellent agreement with the VLE data. In fact, the calculated values trace the VLE data almost exactly.     

A new semiempirical equation of state for fluids—II: Application to pure substances

The semiempirical equation of state proposed in our previous paper is applied to the calculation of thermodynamic properties of pure fluid substances.     

On the derivation and application of a new vapor pressure equation

Starting from the Clapeyron equation and making use of the equivalent expression for the reference state for latent heat of vaporization of pure liquids, namely at 0°K., a new vapor pressure equation is derived as follows: _χ(T_r) has been tabulated for T_r values in the range 0.50 < T_r <0.99 after programming on an IBM 1620 computer. The new vapor pressure equation has been tested with a variety of liquids both polar and non-polar, and found to predict vapor pressure data in the orthobaric range with an average error of ± 1.90% and maximum error of ± 3.20%. A significant outcome of this investigation is the identification of Riedel's factor α_o and Pitzer's acentric factor ω These have been shown to be functions of critical properties and reduced boiling point.     

Development of adsorption buffer and pressure swing adsorption (PSA) unit for gasoline vapor recovery

The effect of a double layered adsorber on the recovery of gasoline from gas emitted from a gasoline storage tank was investigated. The adsorber consists of two different adsorbents: silica gel and activated carbon. A pilot system consisting of an adsorptive buffer for the collection of contaminated air sporadically emitted and a PSA system was installed and operated. Gas from a gasoline tank was fed to the adsorption buffer for a period of time, and subsequently the enriched hydrocarbon stream obtained during the regeneration of the adsorptive buffer was treated by the PSA system. Regeneration of the adsorbent was done by flowing clean air under vacuum. Approximately 21–48 liters of gasoline per hour was recovered with the pilot-scale PSA unit filled with 435 kg of adsorbent in total. The gas emitted from the system contains light hydrocarbon less than 100 ppmv.     

A new model for predicting solute solubility in supercritical fluids based on the Wilson equation

In this work, a new model based on the Wilson solution theory was proposed for predicting the solubility of solids in supercritical fluid (SCF) with and without cosolvent(s) of binary and ternary systems via computation of activity coefficients. For binary systems the model contains two adjustable parameters, while for ternary systems there are four adjustable parameters. The calculated results of the proposed model were compared with that of the literature models, and it is shown that the proposed model is a more accurate one.     

CO_2气藏废弃压力的研究

CO2气藏的废弃压力是气藏开采状况的关键参数,它的大小直接影响到气藏采收率的高低,因此如何计算CO2气藏废弃压力显得十分重要。本文通过考虑气藏开采过程中指数式产能方程系数的变化,推导出计算气藏在地层压力不断变化情况下,任意时刻的指数式产能方程,并在井口生产条件一定的情况下,以最小井底流压下的气井最小携液速度为约束条件,确定出了CO2气藏的废弃压力。     

A Discussion of the Kamlet‐Jacobs Formula for the Detonation Pressure

The main features of the Kamlet‐Jacobs formula for the detonation pressure of C H N O explosives are analytically derived from a BKW (Becker‐Kistiakowsky‐Wilson) equation of state of the detonation products. In the derivation, well‐known typical values at the Chapman‐Jouguet state, in particular the nearly constant value of the relative volume of the detonation products, are used.     

A correlation for heat of vaporization of pure compounds

Twenty-seven selected equations were tested on 162 compounds with 1958 calorimetric data for their abilities to reflect the temperature influence on the heat of vaporization of pure compounds. A new equation is recommended (overall percent deviation 0.27% and percent deviation 0.59% above 0.9T _r ).     

PRSV: The stryjek-vera modification of the peng-robinson equation of state. Parameters for other pure compounds of industrial interest

Pure - compound - parameters for the Stryjek-Vera modification of the Peng-Robinson equation of state, PRSV, are reported for sixty-nine additional compounds of industrial interest. Errors in the reproduction of pure compound vapor pressure are normally below 1% at reduced temperatures lower than 0.7 At reduced temperatures higher than 0.7, for a few compounds for which data are scarce, errors are somewhat higher than 1%.     

One-step synthesis of high purity ZnO micro/nanostructures from pure Zn and pre-alloyed brass powders by vapor phase transport

In this research, vapor phase transport (VPT) was introduced as a facile, inexpensive method to produce ZnO micro/nanostructures from various Zn sources such as pure Zn and alpha brass pre-alloyed powders (Cu–20Zn and Cu–28Zn) at different processing temperatures of 930 °C–1050 °C. Simultaneous thermal analysis (STA) was carried out to investigate Zn evaporation and ZnO micro/nanostructure formation. STA results showed an exothermic peck at 711 °C and 728 °C for Cu–20Zn and Cu–28Zn, respectively, due to oxidation of the evaporated Zn element and formation of ZnO micro/nanostructures. X-ray diffraction results showed that high purity ZnO micro/nanostructures were successfully synthesized via VPT process and the crystallite size was increased from ~60 nm to ~100 nm with increasing processing temperature. Field emission scanning electron microscopy observations showed morphology (e.g. rods, column, tetrapods, and combs) and size of the synthesized micro/nanostructures were dependent on the Zn sources and processing temperature, in which average diameter of the synthesized ZnO structures was increased with increasing the processing temperature. The smallest (98 nm) and largest (603 nm) average diameters of synthesized ZnO micro/nanostructures were attained from the pure Zn and Cu–28Zn brass powders at 930 °C and 1050 °C, respectively.     

高熔体强度聚丙烯水发泡性能及影响因素

以水蒸气作为物理发泡剂,对高熔体强度聚丙烯(HMS-PP)进行挤出发泡。在实验中,通过改变水蒸气压力以及卸压速率研究泡孔的结构和分布,分析压力、卸压速率对发泡体结构和性能的影响。实验结果表明:当水蒸气压力为1.5 MPa,卸压速率为77.8 MPa/s时,可以获得发泡均匀、泡孔密度大、表观密度小的PP发泡制品。得到的泡孔平均直径为0.48 mm,发泡倍率约为12。     

Prediction of thermodynamic properties of polymeric liquids using a new equation of state

In this paper, we have used a simple equation of state (EoS) to predict the density for polymeric liquid mixtures at different temperatures, pressures, and compositions. The excess molar volumes of these mixtures have been also calculated using this equation of state. Also, we have computed isothermal compressibility. A wide comparison with experimental data has been made for each thermodynamic property. The values of statistical parameters between experimental and calculated properties show the ability of this equation of state in reproducing and predicting different thermodynamic properties for studied polymeric mixtures.     

Effects of pressure drop in a PSA process

The effects of pressure drop on the dynamics of fixed-beds were theoretically studied. The system used was an H₂/CO mixture (70 vol% H₂, 30 vol% CO) in zeolite 5A. The pressure drop at the pressurization step affected the breakthrough time at an adsorption step in the PSA process. As a result, the combined effects of pressure drop during adsorption and pressurization steps led to earlier breakthrough compared to the case without a pressure drop. The effect of pressure drop at the adsorption step under the non-isothermal condition was slightly larger than that under the adiabatic condition. In the case of pressurization and blowdown steps with large pressure drop, the flow pattern near the open end during a short period of time had to be explained by the Ergun equation instead of Darcy’s law. However, there was only a slight difference in the results of a multi-bed PSA process depending on whether or not the pressure drops at the pressurization/depressurization steps as well as at the adsorption step were considered.     

Application of physical vapor deposition process to modify activated carbon fibers for ozone reduction

This study utilized the activated carbon fiber (ACF) modified with metal catalyst via physical vapor deposition (PVD) process (ACF/PVD) to diminish ozone. Furthermore, the ozone removal efficiency of ACF/PVD was compared with that of original ACF and ACF modified with metal catalyst via impregnation process (ACF/impregnation). In addition to the kinds of coated metal and the inlet ozone concentrations, the effects of the coating thickness and the reaction temperature on ACF/PVD for ozone removal were also examined. The results indicate that the ozone removal efficiency of ACF/PVD is better than that of original ACF and ACF/impregnation. The ozone removal efficiency of different metal-coated ACF/PVD in the superior order is gold (Au), and manganese (Mn). The increase of Au-coated thickness (3 nm to 80 nm) on ACF/PVD will enhance the ozone removal. However, when the Mn-coated thickness on ACF/PVD is larger than 15 nm, the ozone removal efficiency displays a declining trend. Furthermore, a higher reaction temperature will result in a better ozone removal of ACF/PVD and the original ACF.