Prediction Of Light Fraction Composition Based On MTHS Matrix

Simulation and optimization of petroleum process is an effective method of the development of new technologies,innovation of existing units,process optimization and identification of possible bottlenecks.Lumped model using in the simulation and optimization of refining process can not provide detailed molecular composition.With the development of analysis techniques,accurate composition of low boiling point fraction can be measured.But these techniques are very time-consuming and high-cost in general.Therefore,it is necessary to predict molecular composition of feedstock based on average properties like ASTM distillation curve and density.We predict molecular composition of gasoline and naphtha according to commercial indices based on MTHS(molecular type homologous series)matrix.The main works were carried on as follows:(1)Molecular representation of gasoline and naphtha is determined based on molecular composition characteristics.Properties like critical properties,refractive index etc.of each molecular in the matrix are queried from psychical database.(2)Properties like distillation curves,density of gasoline and naphtha samples are calculated by Aspen Plus software.(3)Derived bulk properties are calculated by correlations.Bulk properties are also calculated by molecular composition and mixing rules.Gamma distribution is used to characterize molecular composition of gasoline and naphtha samples.The sum of the square of the percentage error between the observed and calculated properties is taken as the objective function.Parameters of gamma distribution are variables of the optimization model.(4)Optimization model is proposed against optimization algorithm and object function.Molecular composition of three gasoline samples is calculated through proposed model.Experimental results show that the improved model is superior to the original one in the aspect of prediction accuracy.It can be concluded that the proposed model is capable of predicting the molecular composition of gasoline.(5)Effective constraints according to molecular characteristics of naphtha samples are added to the original model.Molecular composition of four naphtha samples is calculated with higher calculation precision.