| A novel operation mode of constant total reflux batch distillation withmulti-vessel is proposed according to the advantages of total reflux such as highseparation efficiency and simple control method in this article. The main characters ofthe new operation mode are as follows:(1) Without no reflux flow period, the columnis always working under total reflux and so it makes full use of its separationcapability;(2) The middle vessels are distributed evenly along the column. Once thetop concentration reaches the specification value, the liquid holdup in vessels aremoved upwards without the equilibrium of total reflux;(3) After each vessel’sexchange operation, the last vessel is separated from the distillation system. There isno vessel connected to the distillation column when the operation is terminated. Theintensive study on the new operation mode is maked theoretically and experimentallyin this article.The disadvantages of the original total reflux operation in control methods andmathematical models are discussed, and the new operation mode shows greatadvantages through theoretical analysis and comparison with the formers. Themathematical model related to the constant total reflux batch distillation is setup. Thesimulation of the influence factors on the new operation mode is carried out. And then,the comparison between the novel operation mode and the regular constant refluxratio mode is carried out by simulation. The results show that the new operation modehas great advantages in time saving, which is over50%, and product yield, the newmode shows significant potential for separation with high efficiency.The experiments to separate binary systems of methanol-ethanol, isopropanol-n-propanol and ethanol-n-propanol are carried out on a laboratory scale column usingthe constant total reflux and constant reflux ratio operation modes, respectively. Thesimulations under the same conditions as experiments are also conducted withsuitable thermodynamic model. The comparison results show the experimental valuesare consistent with the calculation results, the time saving persent of new operationmode is from18.35%to32.70%according to the experimental data, which indicatethat the constant total reflux batch distillation has great advantages in comparison with the constant reflux ratio mode and the mathematical model is accurate andreliable.For the design of the constant total reflux batch distillation process, the method tocalculate the maximum product amount of light component on the top of the columnis proposed in the article. The accurate of the method is verified by comparisonbetween simulation and calculation results in an example. According to the maximumproduct amount of the light component, the amount of the liquid holdup in the vesselscan be obtained for the new operation mode. The operation methods for constant totalreflux batch distillation are also considered, which shows the operation feasibility, thelongitudinal control and integrated control methods are analyzed in the article. |
