Non-Electrolyte Solid-Liquid Phase Equilibrium Calculation And System Development

The phase equilibriums include vapor-liquid,liquid-liquid,vapor-liquid-liquid,and solid-liquid equilibrium.The solid-liquid equilibrium for non-electrolyte systems is mostly used in the oil refining and chemical industries.The predictive model of solid-liquid equilibrium for non-electrolytes systems were investigated,and the models were modified and evaluated in this paper.A calculation system was developed for the prediction of the solid-liquid equilibrium of non-electrolytes with Microsoft Visual Studio 2010 software which based on the object-oriented programming technology.The six non-electrolyte solid-liquid equilibrium models were proposed on the base of regular solution theory(Won,Pedersen and Chen Wuhua)and local composition theory(P-UNIQUAC,P-UNIQUAC(Chen)and P-UNIQUAC(Ghanaei)).The predictive ability of six models for the prediction of solid-phase fraction and solid-phase composition were evaluated with experimental data of four different systems.The results showed that the average absolute deviations of the six methods for the calculation of solid phase fraction ranged from 3.09 to 11.11%.In addition,it was found that the correction terms of enthalpy difference between solid and liquid phase in the prediction model affected the predictive accuracy of the solid-liquid equilibrium.Therefore,the Won,P-UNIQUAC and P-UNIQUAC(Ghanaei)models for the prediction of non-electrolyte solid-liquid equilibrium were improved.According to the above evaluations,the non-electrolyte solid-liquid equilibrium models were modified by adding Pedersen,Ghanaei,and DIPPR correction terms of enthalpy difference between solid and liquid phase in the model.The improved effect of modified models were also evaluated with experimental data.The results indicated that the average absolute deviations of modified Won model with three different modification motheds,in that order,for the prediction of solid phase fraction were5.82%,5.79% and 5.28%.The deviations were all lower than that of the original Won model(8.08%).The average absolute deviations of the modified P-UNIQUAC model were 7.67%,7.29% and 5.86%,in sequence.All of the three deviations were lower than that of the original P-UNIQUAC model(8.54%).And the deviations of the P-UNIQUAC(Ghanaei)model were 5.51%,5.77% and 3.36%,respectively.The deviations were lower than that of the original P-UNIQUAC(Ghanaei)model(6.43%).The comparion results indicated that the added DIPPR correction term of solid-liquid phase enthalpy difference in the Won,P-UNIQUAC and P-UNIQUAC(Ghanaei)models improved the predictive accuracy of the solid phase fraction.A system for calculation of the solid-liquid equilibrium of non-electrolytes was developed with the Microsoft Visual Studio 2010 software.Based on the researched models of solid-liquid equilibrium,the programs of calculation methods of 15solid-liquid equilibrium models for non-electrolytes were explored.The programs were tested with Won and the modified Won models that added the Pedersen correction term of enthalpy difference between solid and liquid phase for the prediction of the solid-liquid equilibrium process.By testing,the system was accurate and stable for the calculation of solid fractions and solid compositions of non-electrolytes.With the wide application of computer simulation technology,it has great significance and practical value for the study on the solid-liquid equilibrium model of non-electrolytes and for the exploration of computer programs of solid-liquid equilibrium in the simulation,design,and application of petrochemical industrial processes.