The Applicability of Debye-Hückel Model in NaAl(OH)_4-NaOH-H_2O System

1 INTRODUCTION NaAl(OH)4-NaOH-H2O system plays a paramount role in the industry of alumina production, and the calculation of its activity coefficients can not only aid to perfect the theory of alumina production, but also accelerate the research and the development of new technology for reducing the production cost and energy consumption. However, the solution in alumina industry has high concentration with extremely complex structure, and the properties of the solution are easily affe…     

Modeling for mean ion activity coefficient of strong electrolyte system with new boundary conditions and ion-size parameters

A rigorous approach is proposed to model the mean ion activity coefficient for strong electrolyte systems using the Poisson–Boltzmann equation. An effective screening radius similar to the Debye decay length is introduced to define the local composition and new boundary conditions for the central ion. The crystallographic ion size is also considered in the activity coefficient expressions derived and non-electrostatic contributions are neglected. The model is presented for aqueous strong electrolytes and compared with the classical Debye–Hückel (DH) limiting law for dilute solutions. The radial distribution function is compared with the DH and Monte Carlo studies. The mean ion activity coefficients are calculated for 1:1 aqueous solutions containing strong electrolytes composed of alkali halides. The individual ion activity coefficients and mean ion activity coefficients in mixed sol-vents are predicted with the new equations.     

SOLUBILITY OF AMMONIA IN WATER IN MULTICOMPONENT SYSTEM UNDER HIGH PRESSURE

The solubility of NH_3 in water in multicomponent systems under high pressure is of extreme importance to the new integrated ammonia and urea process. This paper proposes a new method for calculating the vaporliquid equilibria for aqueous ammonia solutions under high pressure. Based on the experimental data of the binary system of NH_3-H_2O in the high concentration range, a model has been established for the activity coefficients of NH_3 and H_2O to describe the non-ideality of the liquid phase; and the modified SIRK equation of state for polar compounds has been used to describe the non-ideality of the vapor phase under high pressure. The reliability of this model has been examined in the light of the experimental data of the solubility of NH_3 in H_2O under high pressure in the systems of NH_3-H_2O-N_2, NH_3-H_2O-N_2-H_2-Ar-CH_4 and NH_2-H_2O-N_2-H_2, the last being from Guerreri et al. Both the accuracy of calculation and the concentration range for applicability of this model have been found to surpass those of Guerrerl's model.     

由二元亚系的数据预测混合电解质水溶液的活度系数

The simple equation relating the activity coefficient of each solute in mixed electrolyte solution to its value in binary solutions under isopiestic equilibrium was tested by comparison with the experimental data for the 18 electrolyte solutions consisting of 1：1, 1：2, and 1：3 electrolytes. The isopiestic measurements were made on the quaternary system BaCl2-NH4Br-NaI-H2O and its ternary subsystems NaI-NH4Br-H2O, NaI-BaCl2-H2O, and NH4Br-BaCl2-H2O at 298.15K. The results were used to test the applicability of the Zdanovskii＇s rule to the mixed electrolyte solutions which contain no common ions, and the agreement is excellent. The activity coefficients of the solutes in the above quaternary and ternary systems calculated from the above-mentioned simple equation are in good agreement with the Pitzer＇s equation.     

Progress in the Study on the Phase Equilibria of the CO2·H2O and CO2-HeO-NaCI Systems

To study the feasibility of CO2 geological sequestration,it is needed to understand the complicated mul- tiple-phase equilibrium and the densities of aqueous solution with CO2 and multi-ions under wide geological condi- tions（273.15—473.15K,0—60MPa）,which are also essential for designing separation equipments in chemical or oil-related industries.For this purpose,studies on the relevant phase equilibria and densities are reviewed and analyzed and the method to improve or modify the existing model is suggested in order to obtain more reliable predictions in a wide temperature and pressure range.Besides,three different models（the electrolyte non random two-liquid（ELECNRTL）,the electrolyte NRTL combining with Helgeson model（ENRTL-HG）,Pitzer activity coefficient model combining with Helgeson model（PITZ-HG））are used to calculate the vapor-liquid phase equilib- rium of CO2-H2O and CO2-H2O-NaCl systems.For CO2-H2O system,the calculation results agree with the experimental data very well at low and medium pressure（0—20MPa）,but there are great discrepancies above 20MPa.For the water content at 473.15K,the calculated results agree with the experimental data quite well.For the CO2-H2O-NaCl system,the PITZ-HG model show better results than ELECNRTL and ENRTL-HG models at the NaCl concentration of 0.52mol·L ^-1 .Bur for the NaCl concentration of 3.997mol·L ^-1 ,using the ELECNRTL and ENRTL-HG models gives better results than using the PITZ-HG model.It is shown that available experimental data and the thermodynamic calculations can satisfy the needs of the calculation of the sequestration capacity in the temperature and pressure range for disposal of CO2 in deep saline aquifers.More experimental data and more accurate thermodynamic calculations are needed in high temperature and pressure ranges（above 398.15K and 31.5MPa）.     

CO2-H2O和CO2-H2O-NaCl 体系的相平衡研究进展

To study the feasibility of CO2 geological sequestration,it is needed to understand the complicated mul- tiple-phase equilibrium and the densities of aqueous solution with CO2 and multi-ions under wide geological condi- tions（273.15—473.15K,0—60MPa）,which are also essential for designing separation equipments in chemical or oil-related industries.For this purpose,studies on the relevant phase equilibria and densities are reviewed and analyzed and the method to improve or modify the existing model is suggested in order to obtain more reliable predictions in a wide temperature and pressure range.Besides,three different models（the electrolyte non random two-liquid（ELECNRTL）,the electrolyte NRTL combining with Helgeson model（ENRTL-HG）,Pitzer activity coefficient model combining with Helgeson model（PITZ-HG））are used to calculate the vapor-liquid phase equilib- rium of CO2-H2O and CO2-H2O-NaCl systems.For CO2-H2O system,the calculation results agree with the experimental data very well at low and medium pressure（0—20MPa）,but there are great discrepancies above 20MPa.For the water content at 473.15K,the calculated results agree with the experimental data quite well.For the CO2-H2O-NaCl system,the PITZ-HG model show better results than ELECNRTL and ENRTL-HG models at the NaCl concentration of 0.52mol·L ^-1 .Bur for the NaCl concentration of 3.997mol·L ^-1 ,using the ELECNRTL and ENRTL-HG models gives better results than using the PITZ-HG model.It is shown that available experimental data and the thermodynamic calculations can satisfy the needs of the calculation of the sequestration capacity in the temperature and pressure range for disposal of CO2 in deep saline aquifers.More experimental data and more accurate thermodynamic calculations are needed in high temperature and pressure ranges（above 398.15K and 31.5MPa）.     

拟稳态模型用于间歇萃取精馏的数值模拟

Batch extractive distillation (BED) is a special method used in the distillation process by adding a solvent into the batch distillation column to alter the relative volatility of the components and improve the separation. A comprehensive design and simulation method is required due to the complexity of BED. In this study, a quasi-steady-state model for BED is proposed, the derivation and solution of the model are presented. This shortcut model can be used to simulate the composition and temperature of the reboiler, the top and other plates of the column in a batch extractive distillation operation. The calculated values are in good agreement with the experi-mental data. The results show that the quasi-steady-state model is a practical method because of some advantages such as high precision and fast calculation.     

CH4-CaSO4和H2S-Fe2O3反应体系的热力学和动力学研究

The destruction of hydrocarbon in deep carbonate diagenetic environment is one of problems on the formation of oil and gas. Organic-inorganic reactions in the process of TSR(Thermochemical Sulfate Reduction) are the main reason to make disappearance of the hydrocarbons. The work in this field has often been the subject of much research work in recent years. In this paper, the thermodynamics of CH4-CaSO4 and H2S-Fe2O3 systems is discussed to investigate the possibility of reactions. It is found that these two reactions can proceed spontaneously.Increasing temperature is favorite for CH4-CaSO4 system but disfavorite for H2S-Fe2O3 system. Thermal simulation experiments were carried out using autoclave at high temperature and high pressure. The properties of the products were characterized by microcoulometry, FT-IR and XRD methods. On the basis of the experimental data, a reaction kinetic model is developed and kinetic parameters are determined.     

Liquid-Liquid Equilibria of Water Butyric Acid Nonanol Ternary System

Liquid-liquid equilibrium (LLE) data for the water butyric acid nonanol system have been determined experimentally at the temperatures of 298.15 K, 308.15 K and 318.15 K. Tie-line compositions were correlated by Othmer-Tobias method. The universal quasichemical functional group activity coefficient (UNIFAC) and modified UNIFAC methods were used to predict the phase equilibrium in the system using the interaction parameters between CHs, CH2, COOH, OH and H2O functional groups. Distribution coefficients and separation factors were evaluated for the immiscibility region.     

借助变阱宽方阱链流体状态方程模拟非电解质体系表面张力和粘度(英文)

The equation of state(EOS)for square-well chain fluid with variable range(SWCF-VR) developed in our previous work based on statistical mechanical theory for chemical association is employed for the correlations of surface tension and viscosity of common fluids and ionic liquids(ILs).A model of surface tension for multi-component mixtures is presented by combining the SWCF-VR EOS and the scaled particle theory and used to produce the surface tension of binary and ternary mixtures.The predicted surface tensions are in excellent agreement with the experimental data with an overall average absolute relative deviation(AAD)of 0.36%.A method for the calculation of dynamic viscosity of common fluids and ILs at high pressure is presented by combining Eyring’s rate theory of viscosity and the SWCF-VR EOS.The calculated viscosities are in good agreement with the experimental data with the overall AAD of 1.44% for 14 fluids in 84 cases.The salient feature is that the molecular parameters used in these models are self-consistent and can be applied to calculate different thermodynamic properties such as pVT,vapor-liquid equilibrium,caloric properties,surface tension,and viscosity.     

Mathematical model of absorption and hybrid heat pump

Recovering waste heat from industrial processes is beneficial in order to reduce the primary energy demands and heat pumps can be used to this purpose.Absorption heat pumps are energy-saving and environment-friendly because use working fluids that do not cause ozone depletion and can reduce the global warming emissions.The hybrid heat pump processes combine the conventional vapor-compression and the absorption heat pump cycles.Studies about the simulations and modeling of hybrid heat pumps are few in literature.In this research a mathematical model for single effect absorption and hybrid heat pump is carried out with ChemCad(R) 6.0.1.LiBr-H2O is used as working fluid while electrolytic NRTL and electrolytes latent heat are used as thermodynamic model due to the better results.Binary parameters of activity coefficients are regressed from experimental vapor pressure data while default constants are used for the solubility expressions.A design of heat pumps is developed and a new modeling of generator is analyzed.The coefficient of performance of absorption heat pump and hybrid heat pump is equal to 0.7 and 0.83 respectively.For absorption heat pump a sensitivity analysis is carried out to evaluate the effect of temperature and pressure generator,the concentration of Li-Br solution on coefficient of performance,cooling capacity and working fluid temperature.For hybrid heat pump,the different coefficients of performance,the primary energy ratio,the generator heat,and the compressor power are analyzed for different values of compressor proportion.Results show that comparing the two systems the hybrid pump allows to save more primary energy,costs and carbon dioxide emissions with respect to absorption heat pump with the increasing of compressor proportion parameter.Future researches should focus on the construction of this heat pumps integrated in chemical processes as a biogas plant or trigeneration systems.     

Thermodynamic modeling and phase diagram prediction of salt lake brine systems Ⅱ. Aqueous Li~+-Na~+-K~+-SO_4~(2-) and its subsystems

It is still a challenging task to accurately and temperature-continuously express the thermodynamic properties and phase equilibrium behaviors of the salt-lake brine with multi-component,multitemperature and high concentration.The essential subsystem of sulfate type brine,aqueous Li~+-Na~+-K~'-SO_4~(2-) and its subsystems across a temperature range from 250 K to 643 K are investigated with the improved comprehensive thermodynamic model.Liquid parameters(Δg_(IJ),Δh_(IJ),and ΔC_(p,IJ)) associated with the contributions of Gibbs energy,enthalpy,and heat capacity to the binary interaction parameters,i.e.the temperature coefficients of eNRTL parameters formulated with a Gibbs Helmholtz expression,are determined via multi-objective optimization method.The solid constants Δ_fG_k°~((298.15)) and Δ_fH_k°~((298.15)) of11 solid species occurred in the quaternary system are rebuilt from multi-temperature solubilities.The modeling results show the accurate representation of(1) solution properties and binary phase diagram at temperature ranges from eutectic points to 643 K;(2) isothermal phase diagrams for Li_2SO_4-Na_2SO_4-H_2O,Li_2SO_4-K_2SO_4-H_2O and Na_2SO_4-K_2SO_4-H_2O ternary systems.The predicted results of complete structure and polythermal phase diagram of ternary systems and the isothermal phase diagrams of quaternary system excellently match with the experimental data.     

ON THE POSSIBILITY OF PREDICTING PHASE EQUILIBRIA FROM MOLECULAR STRUCTURE

The abvent of the ASOG and UNIFAC group-contribution methods for the prediction of activity coefficients approximately 15 years ago was a significant boost to the ability of chemical engineers to model chemical processes. This paper reviews the status and recent progress in the group-contribution approach to predicting liquid-phase activity coefficients.Several different types of liquid mixtures arc considered: non electrolyte mixtures with normal-boiling components; mixtures with dissolved gases; mixtures with polymers; and mixtures including strong electrolytes. It is concluded that in recent years much progress has been made in the development of group-contribution models for the prediction of activity coefficients. It is in addition shown that combining activity coefficient models with equations of state renders the group-contribution approach applicable also to the highpressure region.Due to space limitation, this review emphasizes UNIFAC and related models.     

水-丁酸-壬醇三相系统的液液平衡

Liquid-liquid equilibrium (LLE) data for the water butyric acid nonanol system have been determined experimentally at the temperatures of 298.15 K, 308.15 K and 318.15 K. Tie-line compositions were correlated by Othmer-Tobias method. The universal quasichemical functional group activity coefficient (UNIFAC) and modified UNIFAC methods were used to predict the phase equilibrium in the system using the interaction parameters between CH3, CH2, COOH, OH and H2O functional groups. Distribution coefficients and separation factors were evaluated for the immiscibility region.     

气体添加剂对热脱硝过程影响的实验和建模研究

An experimental study of thermal DeNOx process with different additives was performed in an electricity- heated tubular flow reactor, showing that CO is less effective to lower the optimum temperature than H2 and CH4. The maximum NO reduction is lowered with H2 added, while it is hardly affected by CO or CH4. The temperature window is widened appreciably with CH4 added, while it is narrowed slightly by H2 or CO. The disadvantage of CH4 is that it causes CO emission due to its incomplete oxidation, and the maximum conversion of CH4 to CO is more than 50%. In general, the calculation using a detailed chemical kinetic model predicts most of the process features reasonably well. The analysis on reaction mechanism shows that the effects of these additives on NO reduction are achieved principally by promoting the production of &;#8226;OH radical.     

含盐聚电解质溶液的分子热力学模型

A molecular thermodynamic model of polyelectrolyte developed previously was extended to polyelectrolyte solutions with added salts.Thermodynamic properties,such as activity coefficients of polyelectrolytes or added salts and osmotic coefficients of solvent, of a number of aqueous mixtures of polyelectrolytes and salts are analyzed with the proposed model.Successful correlation is obtained in the range of moderate or higher polyion concentration.For the same sample,thermodynamic properties of polyelectrolytes with and without simple electrolytes can be predicted mutually using parameters from regression data.     

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.     

Correlation of the mean activity coefficient of aqueous electrolyte solutions using an equation of state

Accurate calculation of thermodynamic properties of electrolyte solution is essential in the design and optimization of many processes in chemical industries.A new electrolyte equation of state is developed for aqueous electrolyte solutions.The Carnahan–Starling repulsive model and an attractive term based on square-well potential are adopted to represent the short range interaction of ionic and molecular species in the new electrolyte EOS.The long range interaction of ionic species is expressed by a simplified version of Mean Spherical Approximation theory(MSA).The new equation of state also contains a Born term for charging free energy of ions.Three adjustable parameters of new e EOS per each electrolyte solution are size parameter,square-well potential depth and square-well potential interaction range.The new e EOS is applied for correlation of mean activity coefficient and prediction of osmotic coefficient of various strong aqueous electrolyte solutions at 25 °C and 0.1 MPa.In addition,the extension of the new e EOS for correlation of mean activity coefficient and solution density of a few aqueous electrolytes at temperature range of 0 to 100 °C is carried out.     

描述CO2的柔性模型

A fully flexible potential model for carbon dioxide has been developed to predict the vapor-liquid coexistence properties using the NVT-Gibbs ensemble Monte Carlo technique (GEMC). The average absolute deviation between our simulation and the literature experimental data for saturated liquid and vapor densities is 0.3% and 2.0%, respectively. Compared with the experimental data, our calculated results of critical properties (7.39 MPa, 304.04 K, and 0.4679 gcm－3) are acceptable and are better than those from the rescaling the potential parameters of elementary physical model (EPM2). The agreement of our simulated densities of supercritical carbon dioxide with the experimental data is acceptable in a wide range of pressure and temperature. The radial distribution function es-timated at the supercritical conditions suggests that the carbon dioxide is a nonlinear molecule with the C O bond length of 0.117 nm and the O C O bond angle of 176.4°, which are consistent with Car-Parrinello molecular- dynamics (CPMD), whereas the EPM2 model shows large deviation at supercritical state. The predicted self-diffusion coefficients are in agreement with the experiments.     

模糊自适应遗传算法及其在化工中的应用

Considering that the performance of a genetic algorithm (GA) is affected by many factors and their rela-tionships are complex and hard to be described,a novel fuzzy-based adaptive genetic algorithm (FAGA) combined a new artificial immune system with fuzzy system theory is proposed due to the fact fuzzy theory can describe high complex problems.In FAGA,immune theory is used to improve the performance of selection operation.And,crossover probability and mutation probability are adjusted dynamically by fuzzy inferences,which are developed according to the heuristic fuzzy relationship between algorithm performances and control parameters.The experi-ments show that FAGA can efficiently overcome shortcomings of GA,i.e.,premature and slow,and obtain better results than two typical fuzzy GAs.Finally,FAGA was used for the parameters estimation of reaction kinetics model and the satisfactory result was obtained.