Multi Component Component System Batch Distillation Simulation Study

Along with advance in technology and humanity living standard unceasing enhancement,the number of fine chemical and special chemical which are demanded is larger. Also the simulation study of batch distillation which is main process and the separation method of fine chemical product is more important.This dissertation carries out the multicomponent system batch distillation simulation study. The work of research mainly includes the establishment of multi-component batch distillation mathematical model as well as value computational method of the mathematical model, and the experiment validation of simulation study .The main research content is as follows:(1) Establishment of mathematical model. This dissertation establishs a modified mathematical model of multicomponent batch distillation about which the mole holdup of liquid in the plate is constant. The model also considers the situation that heating quantity of tower kettle is changing continuously. The model of constant liquid holdup mole is suitable for the system in which the number of various components molecular weight, liquid density and latent heat of vaporization are close.Computational complexity of the traditional constant mole of liquid holdup model is big, the computing time is long, and the simulation study all aims at the situation that heating quantity of tower kettle is invariable. This dissertation establishes the batch distillation mathematical model which is suitable for the situation that heating quantity of tower kettle is changing continuously. While the separation system is the homolog, the supposition of the constant molar flow rate of liquid and gas phase in the tower is used, no need to carry on heat balance and reduce computational complexity.(2) Research of numerical implementation of mathematical model. The batch distillation is the dynamic process, mathematical model used to describe this process is differential algebra system of equations. Differential equation in the mathematical model belongs to the rigid differential equation.The rigid differential equation cannot use the general solution method used to the common differential equation, need to use the special method. This dissertation uses one-step explicit method of the"Treanor".The"Treanor"one-step explicit method computation mentality is simple, the computation complexity is small. when the stiffness ratio is not very big it has the advantages that computation process is stable, the accuracy of result is good. The order of magnitude of stiffness ratio of the batch distillation mathematical model established in the dissertation is approximately 102, compared to the order of magnitude of strong stiffness ratio 106 ,it is very small belonged to the situation of the weak stiffness , therefore"Treanor"one-step explicit method is used in the dissertation.(3) Experimental study of multi-component batch distillation. The experimental study work has been completed in rectifier unit which has eight plates. The findings indicates that the mole fraction of tower top and bottom which is computed using the modified mathematical model of constant liquid mole holdup is close to that of experimental study, the most relative deviation of the result between simulation research and the experimental result is 34.90%, the average deviation is 15.45%. It shows that the modified mathematical model proposed in this dissertation is quite close to the actual batch distillation operation, available for batch distillation operation analog computation under same condition.