Modeling And Application Of MTBE Reactive Distillation Column

Reactive distillation(RD) is a process combines reaction and distillation, the products can be removed by distillation during reaction, RD favors the promotion of reaction conversion as well as energy/investment reduction, and has become the hotconsidered by academy and engineering. Mechanism modeling is the question of the core.Steady theoretical model in this paper includes product quality restriction, mass balance, phase equilibrium, normalization, energy balance and reaction rate equation, namely MESHRequation set. For the precision of gas and liquid quantity in each theoretical stage and avoiding Lewis-Matheson which involves two loop iterations, equimolar flow assumption is improved by calculating gas and liquid quantity according to evaporation of liquid in each theoretical stage, the iterations can be reduced to once.Then, a new calculation method is applied to RD steady theoretical model. Simplified calculation of gas and liquid quantity in this method make it possible to solve simultaneous equations. Calculation steps are: 1) Set top pressure, reflux ratio, feedings and product requirements and go into first cycle computing. 2) Set initial values of stage temperature and liquid compositions and calculate activity coefficient by Wilson equation. 3) Calculate initial value of phase equilibrium constants. 4) Calculate initial value of gas compositions. 5) Modified values of gas and liquid compositions can be got by ode45 algorithm in MATLAB. 6) Use theory stage compositions to validate if normalizing conditions are met. O utput can be got if met, else start second cycle computing with modified stage temperatures. MATLAB program are applied to classic MTBE case by Jacobs and Krishna[80], the result shows that calculated values by method in this paper matches that in the literature well, which means model and calculation method in the paper are feasible.At last, operation optimization of MTBE reaction distillation column can be done according to model above. Feed temperature, top pressure and reflux ratio are chosen as optimization variables, total operating expense as objective function, the calculation of Jacobs case shows that total operating expense can be saved as 9478900 yuan/a when reflux ratio is 6.5, top pressure is 10.7 atm, Me OH feed temperature is 324 K and C4 feed temperature is 360 K.