Phase equilibrium data prediction and process optimizationin butadiene extraction process

In response to the lack of reliable physical parameters in the process simulation of the butadiene extraction,a large amount of phase equilibrium data were collected in the context of the actual process of butadiene production by acetonitrile.The accuracy of five prediction methods,UNIFAC(UNIQUAC Functional-group Activity Coefficients),UNIFAC-LL,UNIFAC-LBY,UNIFAC-DMD and COSMO-RS,applied to the butadiene extraction process was verified using partial phase equilibrium data.The results showed that the UNIFAC-DMD method had the highest accuracy in predicting phase equilibrium data for the missing system.COSMO-RS-predicted multiple systems showed good accuracy,and a large number of missing phase equilibrium data were estimated using the UNIFAC-DMD method and COSMO-RS method.The predicted phase equilibrium data were checked for consistency.The NRTL-RK(non-Random Two Liquid-Redlich-Kwong Equation of State)and UNIQUAC thermodynamic models were used to correlate the phase equilibrium data.Industrial device simulations were used to verify the accuracy of the thermodynamic model applied to the butadiene extraction process.The simulation results showed that the average deviations of the simulated results using the correlated thermodynamic model from the actual values were less than 2%compared to that using the commercial simulation software,Aspen Plus and its database.The average deviation was much smaller than that of the simulations using the Aspen Plus database(>10%),indicating that the obtained phase equilibrium data are highly accurate and reliable.The best phase equilibrium data and thermodynamic model parameters for butadiene extraction are provided.This improves the accuracy and reliability of the design,optimization and control of the process,and provides a basis and guarantee for developing a more environmentally friendly and economical butadiene extraction process.

Intrinsic correlation between the generalized phase equilibrium condition and mechanical behaviors in hydrate-bearing sediments

The phase equilibrium and mechanical behaviors of natural gas hydrate-bearing sediment are essential for gas recovery from hydrate reservoirs.In heating closed systems,the temperature-pressure path of hydrate-bearing sediment deviates from that of pure bulk hydrate,reflecting the porous media effect in phase equilibrium.A generalized phase equilibrium equation was established for hydrate-bearing sediments,which indicates that both capillary and osmotic pressures cause the phase equilibrium curve to shift leftward on the temperature-pressure plane.In contrast to bulk hydrate,hydrate-bearing sediment always contains a certain amount of unhydrated water,which keeps phase equilibrium with the hydrate within the hydrate stability field.With changes in temperature and pressure,a portion of pore hydrate and unhydrated water may transform into each other,affecting the shear strength of hydrate-bearing sediment.A shear strength model is proposed to consider not only hydrate saturation but also the change in temperature and pressure of hydrate-bearing sediment.The model is validated by experimental data with various hydrate saturation,temperature and pressure conditions.The deformation induced by partial dissociation was studied through depressurization tests under constant effective stress.The reduction in gas pressure within the hydrate stability field indeed caused sediment deformation.The dissociation-induced deformation can be reasonably estimated as the difference in volume between hydrate-bearing and hydrate-free sediments from the compression curves.

Studies on Solid-Liquid Phase Transfer Equilibrium of Onium Salts(Ⅱ)

The present paper contains the effects of the ammonium ion, counter ion, solvent and anion being transferred on the solid-liquid phase transfer equilibrium constant of quaternary ammonium salts. The most striking difference between solid-liquid and liquid-liquid phase transfer equilibriums is that the length of alkyl chain shows a large effect on the latter but little on the former This means that the chain length affects only the hydrophobicity, rather than the lipophilicity.Keywords Quaternary ammonium salt, Phase transfer catalysis, Equilibrium constant, Hydrophobicity, Lipophilicity

Alloy gene Gibbs energy partition function and equilibrium holographic network phase diagrams of AuCu_3-type sublattice system

Taking AuCu3-type sublattice system as an example, three discoveries have been presented: First, the third barrier hindering the progress in metal materials science is that researchers have got used to recognizing experimental phenomena of alloy phase transitions during extremely slow variation in temperature by equilibrium thinking mode and then taking erroneous knowledge of experimental phenomena as selected information for establishing Gibbs energy function and so-called equilibrium phase diagram. Second, the equilibrium holographic network phase diagrams of AuCu3-type sublattice system may be used to describe systematic correlativity of the composition?temperature-dependent alloy gene arranging structures and complete thermodynamic properties, and to be a standard for studying experimental subequilibrium order-disorder transition. Third, the equilibrium transition of each alloy is a homogeneous single-phase rather than a heterogeneous two-phase, and there exists a single-phase boundary curve without two-phase region of the ordered and disordered phases; the composition and temperature of the top point on the phase-boundary curve are far away from the ones of the critical point of the AuCu3 compound.

Alloy gene Gibbs energy partition function and equilibrium holographic network phase diagrams of Au_3Cu-type sublattice system

Taking Au3Cu-type sublattice system as an example, three discoveries have been presented. First, the fourth barrier to hinder the progress of metal materials science is that today’s researchers do not understand that the Gibbs energy function of an alloy phase should be derived from Gibbs energy partition function constructed of alloy gene sequence and their Gibbs energy sequence. Second, the six rules for establishing alloy gene Gibbs energy partition function have been discovered, and it has been specially proved that the probabilities of structure units occupied at the Gibbs energy levels in the degeneracy factor for calculating configuration entropy should be degenerated as ones of component atoms occupied at the lattice points. Third, the main characteristics unexpected by today’s researchers are as follows. There exists a single-phase boundary curve without two-phase region coexisting by the ordered and disordered phases. The composition and temperature of the top point on the phase-boundary curve are far away from those of the critical point of the Au3Cu compound; At 0 K, the composition of the lowest point on the composition-dependent Gibbs energy curve is notably deviated from that of the Au3Cu compounds. The theoretical limit composition range of long range ordered Au3Cu-type alloys is determined by the first jumping order degree.

Phase equilibrium of CaSO_4Ca(OH)_2-H_2O system

In order to provide the theoretical guidance for applying the neutralization method to treatment of heavy metals wastewater with high concentration of sulfate, and to better understand the mechanism of calcium sulfate scale formation, the equilibrium solubility data of CaSOa-Ca（OH）2-H2O system at 298.15 K were theoretically calculated via the Pitzer semi-empirical ion-interaction theory, and determined experimentally by the optical method combining with X-ray diffractometry, and the calculated and determined phase diagrams of CaSOa-Ca（OH）2-H2O system were plotted and compared. Physical definition of each area was studied, and the physical law of characteristic point and line was explained in detail. Adjusting the pH value of neutralization-hydrolysis solution depended on the SO4z- concentration in the system. And interaction characteristics between the solubilities of CaSO4（s）and Ca（OH）2（s）were found out.

Purification of Inositol. Studies on the Phase Equilibrium of the System C 6H 12 O 6 NH 4Cl C 2H 5OH H 2O(C 2H 5 OH/H 2O =0.90, by wt ) at 35℃

The solubilities and the refractive indices of the saturated solution in the system C 6H 12 O 6 NH 4Cl C 2H 5OH-H 2O ( C 2H 5OH / H 2O=0.90, by wt ) at 35℃ have been determined. The isotherms and refractive indices of the system at 35℃ consist of 2 branches, corresponding to C 6H 12 O 6( H 2O and NH 4Cl. The composition of eutectic solution is C 6H 12 O 6: 4.40 %, NH 4Cl: 13.86 %, C 2H 5OH: 38.88 %.

Solid-Liquid Equilibrium of Terephthalic Acid in Several Solvents

Terephthalic acid(PTA) is practically one of the main materials of polyester. Its corresponding solid-liquid equilibrium data will provide essential support for industry design and further theoretical studies. In this work,solid-liquid equilibriums of terephthalic acid in four solvents, N,N-dimethylformamide, N,N-dimethylacetamide,dimethylsulphoxide and N-methyl-2-ketopyrrolidene, were determined in the temperature range from 293.15 K to 364.6 K by dynamic method. All these data were regressed by λh model, Wilson model and NRTL model, average absolute relative deviations of which are 1.25%, 15.02% and 7.22% respectively. It indicates that λh model is mostsuitable for description of the solid-liquid equilibrium containing PTA.

Phase Equilibrium of Quaternary System Cd^(2+)//Cl^-,SO_4^(2-),NO_3^--H_2O at 298 K

Solid-liquid equilibrium of quaternary system Cd2＋//Cl–, SO42–, NO3–-H2O at 298 K was studied by means of an isothermal solution saturation method. Experimental results indicate that there are three univariant curves BE, AE and CE, one invariant point E and three crystallization fields in the quaternary system. The quaternary system belongs to a simple type, and there are no double salts or solid solution existing. The crystallization zones of equilibrium solid phases are CdCl2·5/2H2O（AEB field）, 3CdSO4·8H2O（AEC field） and Cd（NO3）2·4H2O（BEC field）, respectively. The composition of the invariant point is CdCl2, Cd（NO3）2, CdSO4 and H2O and the contents of which are 17.02%, 45.50%, 4.52% and 32.96%, respectively. The physico-chemical properties of solution in the quaternary system show regular changes along with the increased cadmium concentration. The results indicate that Cd（NO3）2 possessed the highest solubility among those three salts, which means a strong transfer of Cd ion and a high pollution risk of soil environment. And the solubility of CdSO4 would be restrained as the salts existing together.

Phase Equilibrium Calculations in Mixtures Containing Caprolactam with a UNIFAC Model

An extended liquid-liquid equilibrium(LLE) UNIFAC model is proposed to describe phase equilibria of mixtures containing caprolactam.In this model,caprolactam is introduced as a new group.New group interaction parameters are calibrated from 156 sets of liquid-liquid equilibrium data.The present model gives satisfactory correlation and prediction in liquid-liquid equilibrium,including quaternary systems containing the mixed solvent of an alcohol and an alkane.The model can be applied to predict caprolactam solubility in water and benzene accurately.Freezing point and vapor-liquid equilibrium of binary systems containing caprolactam are also predicted with the extended LLE UNIFAC model.Satisfactory prediction results are obtained.

Calculation of the Phase Equilibrium of CO2–Hydrocarbon Binary Mixtures by PR-BM EOS and PR EOS

The phase equilibrium data of CO2 hydrocarbon binary mixtures are important for the design and operation of CO 2 ood- ing, coal liquefaction, and supercritical extraction processes. Numerous pieces of binary phase equilibrium data have been obtained. Thus, models for the accurate calculation of binary and multicomponent mixtures must be developed on the basis of existing data. In this work, 3578 vapor liquid phase equilibrium data points for 10 CO 2 hydrocarbon binary mixtures, including CO2 butane, CO 2 pentane, CO 2 isopentane, C O 2 hexane, CO 2 benzene, CO 2 heptane, CO 2 octane, C O 2 non- ane, CO 2 decane, and C O 2 undecane, were collected. The PR and PR-BM equations of state (EOS) in combination with relevant mixing rules were used to calculate the phase equilibrium data of the CO 2 hydrocarbon binary mixtures. The binary interaction parameter k ij in the PR EOS was temperature independent, whereas parameters in the PR-BM EOS were functions of temperature. Thus, the phase equilibrium data and other thermodynamic properties of the binary and multicomponent mixtures at di erent temperatures and pressures can be calculated by using the parameters obtained in this work. The PR-BM EOS performed better than the PR EOS, and the average absolute deviations over the temperature range of 255.98 408.15 K calculated by the PR EOS and PR-BM EOS were less than 5.74% and 3.36%, respectively. The results calculated by the two EOS were compared with those calculated by other models, such as PPR78, PR + LCVM + UNIFAC, KIE + PR EOS + HV, and PSRK. The phase equilibrium data of CO 2 butane decane, CO 2 hexane decane, and C O 2 octane decane ternary mixtures were calculated by the two EOS. The average overall deviations for the CO 2 mole fractions calculated by the two EOS were less than 7.66%.

Study on Phase Equilibrium Properties for CO_(2)^+ Cosolvent Binary Systems

In this study, the constant volume, visual method is used to measure the critical point of CO2+toluene, CO2+cyclohexane, CO2+n-butyraldehyde, CO2+i-butyraldehyde, CO2+methanol and CO2+alcohol binary systems. The relationship between critical point and the concentration of the entrainer for different substances has been discussed, and the comparison of the phase behavior of single component system and that of binary systems have been carried out.

Phase Equilibrium of Isobutanol in Supercritical CO2

Vapor-liquid phase equilibrium data including composition,densities,molar volume and equilibrium constant of isobutanol in supercritical carbon dioxide from 313.2K to 353.2K were measured in a variable-volume visual cell.The properties of critical point were obtained by extrapolation.The results showed that critical temperature,critical pressure and critical compressibility factor of CO2-isobutanol system decreased with the increase of critical CO2 content.The phase equilibrium model was established by Peng-Robinson equation of state and van der Waals-2 mixing regulation,and model parameters were determined by optimization calculation of nonlinear least square method.The correlation between calculated values and the experimental data showed good agreement.

Discussion on the Non-Equilibrium Phase of the Gliding Arc Plasma Driven by the Transverse Magnetic Field

a gliding arc driven by the transverse magnetic field was ignited between the electrodes with a complicated shape at atmospheric pressure and a non-equilibrium plasma was gencrated. Under our experimental conditions, a phenomenon was clearly observed where the arc power decreased with the increase in arc voltage. As the arc voltage was higher than 3.375 kV, the are power acquired from the power supply decreased, and the arc plasma began to switch to a non-equilibrium phase. The existence of the non-equilibrium arc plasma was very short, about 10 ms in one gliding arc discharge cycle.

Phase Equilibrium and Phase Diagram of the Ternary System（MgCl2 + MgB2O4 + H2O） at 288 and 298 K

1 Introduction The brines with high concentrations of magnesium and boron resources are widely distributed in the Qaidam Basin of the Qinghai-Tibet plateau,China(Zheng&Tang,1988).Although some works on the ternary system

PHASE EQUILIBRIUM FOR THE TERNARY SYSTEM VINYL CHLORIDE-CHLORINATED POLYETHYLENE-POLY(VINYL CHLORIDE)

Swelling capacity of vinyl chloride (VC) in chlorinated polyethylene (CPE) with 25—40 wt% Cl at temperature 30—57℃ was studied and their relationships were correlated with Langmuir and Freundlich adsorption equations. A ternary phase diagram for VC-CPE-PVC was also established. In-situ polymerization conditions of CPE-g-VC were proposed and CPE content control was analyzed for the manufacturing process of CPE-g-VC graft product based on results of phase equilibrium study.

Data-driven optimization study of the multi-relaxation-time lattice Boltzmann method for solid-liquid phase change

Sharp phase interfaces and accurate temperature distributions are important criteria in the simulation of solid-liquid phase changes.The multi-relaxation-time lattice Boltzmann method(MRT-LBM)shows great numerical performance during simulation;however,the value method of the relaxation parameters needs to be specified.Therefore,in this study,a random forest(RF)model is used to discriminate the importance of different relaxation parameters to the convergence,and a support vector machine(SVM)is used to explore the decision boundary of the convergent samples in each dimensional model.The results show that the convergence of the samples is consistent with the sign of the decision number,and two types of the numerical deviations appear,i.e.,the phase mushy zone and the non-physical heat transfer.The relaxation parameters chosen on the decision boundary can further suppress the numerical bias and improve numerical accuracy.

Phase equilibrium studies of titanomagnetite and ilmenite smelting slags

The phase equilibrium information of slag plays an important role in pyrometallurgical processes to obtain optimum fluxing conditions and operating temperatures.The smelting reduction of titanomagnetite and ilmenite ores in an iron blast furnace(BF)can form Ti(C,N)particles,causing the increased viscosities of slag and hot metal.HIsmelt has been developed in recent years for ironmaking and does not need coke and sinter.The formation of Ti(C,N)in the HIsmelt process is avoided because the oxygen partial pressure in the process is higher than that in the BF.The smelting of TiO_(2)-containing ores in the HIsmelt process results in Al_(2)O_(3)-MgO-SiO_(2)-CaO-TiO_(2)slag.Phase equilibrium in this slag system has been investigated using equilibration,quenching,and electron probe microanalysis techniques.The experimental results were presented in two pseudo-binary sections,which represent the process of HIsmelt for the treatment of 100%titanomagnetite ore and mixed titanomagnetite+ilmenite ore(mass ratio of 2:1),respectively.The primary phases observed in the composition range investigated include pseudo-brookite M_(3)O_(5)(MgO·2TiO_(2)-Al_(2)O_(3)·TiO_(2)),spinel(MgO·Al_(2)O_(3)),perovskite CaTiO_(3),and rutile TiO_(2).The results show that the liquidus temperatures decrease in the TiO_(2)and M_(3)O_(5) primary phase fields and increase in the spinel and CaTiO_(3)primary phase fields with the increase in CaO concentration.The calculation of solid-phase fractions from the experimental data has been demonstrated.The effect of basicity on the liquidus temperatures of the slag has been discussed.The smelting of titanomagnetite plus ilmenite ores has significant advantages to obtain low-sulfur hot metal and high-TiO_(2)slag.Experimentally determined liquidus temperatures were compared with the FactSage predictions to evaluate the existing thermodynamic databases.

NON-CUBIC EQUATION OF STATE FOR PHASE EQUILIBRIUM CALCULATIONS

A new non-cubic equation of state is proposed for calculation of the thermodynamic properties ofnonpolar and polar fluids and their mixtures,including,saturated vapor pressure,saturated liquid volume,saturated vapor volume,heats of vaporization and vapor-liquid equilibria.The new equation is derived from thegeneralized van der Waals partition function in which the repulsive terms are expressed with the Carnahan andStarling equation for hard spheres,and the attractive terms are made up of the dispersive energy and theChemical association energy. The rules of dependence of parameters α and σ and on temperature are considered broadly so that the newequation yields good agreement with experimental saturated properties of 20 nonpolar and 27 polar fluids in therange of reduced temperatures of 0.5 to 1.0 The new equation with parameters group-contributed generally givessatisfactory predictions on saturated properties. Correlations of vapor-liquid equilibrium data for alcohol-containing systems by using van

PHASE EQUILIBRIUM OF COMPLEX MIXTURES WITH EQUATIONS OF STATE: AN UPDATE5

Here we review a new class of mixing rules (hat have extended range of mixtures and conditions that can now be described by equation of state models. One characteristic of these mixing rules is that they simultaneously satisfy the boundary conditions of producing a second virial coefficient that is quadratic in mole fraction, and a free energy of mixing like that of an activity coefficient model at high density, though the mixing rule is itself independent of density. We show that using this mixing rule, various asymmetric, highly nonideal mixtures can be accurately described. One serendipitous result is that the parameters in this mixing rule model are almost independent of temperature, which allows accurate extrapolations of phase behavior to be made over large ranges of temperature and pressure.