Study On Modeling AndOptimal Control OfReactive Distillation Process

Reactive distillation process (RDP), combining reaction and distillation process, is an old idea that has received renewed attention in recent years. This thesis focuses on the study of modeling, control and optimization techniques of RDP. Main contributions and achievements are as follows:A general non-equilibrium rigorous model for RDP is developed in this thesis. Based on the pseudo-homogenous assumption, two main factors reaction and separation are de-coupled, and an RDP model with the same format as that for a traditional distillation process is established. To solve the model with a large number of algebraic equations, modified M-K equations with tri-diagonal matrix form are developed based on the improved Separation Efficiency Functions (SEFS), which greatly increases the iteration efficiency. This thesis also develops a general reactive distillation dynamic model. Through splitting of the differential variables based on SEFS, large-scaled differential algebraic equations can be solved with the improved Gear's algorithm which makes the dynamic model suitable for the on-line application. A simulation platform for the control loop design and evaluation of RDP by introducing control system equations into the dynamic model is also developed.A lactic acid purification pilot-scale RDP is investigated. Steady state characteristics and open-loop responses of the column are analyzed through simulation. Hydraulic model calculations are also implemented. Based on the analysis results, different control systems are designed and explored and two alternative control schemes are compared. The simulation shows that the direct mass balance control strategy can meet the demand for product purity and conversion effectively and outperform the indirect mass balance control strategy.MTBE (methyl tert-butyl ether) production RDP is also explored. The time scale multiplicity has been observed through dynamic simulation. Different quality control alternatives are designed and compared. Since simply controlling the product quality can not meet the demand for conversion, this thesis develops an inferential control strategy incorporating soft sensor model. The unified control method combining the conversion and purity control loops is able to effectively handle MTBE purity and isobutene conversion control demand.This thesis has also developed a general reactive distillation optimization model. Through MTBE RDP operational optimization calculation, the total annual profit can be increased by 1.62%. Through the integrated optimization analysis of the lactic acid purification RDP, the optimal design scheme is obtained and total annual profit can be increased by 8.23% through optimal analysis. The results show that traditional process optimization methods and ideas can be modified and introduced into RDP. An on-line RDP optimization system is also developed in this thesis.