Kaibel分壁精馏塔分离芳烃的稳态和动态模拟

Steady-state behavior and control of Kaibel divided-wall column for aromatics separation

Kaibel分壁精馏塔(Kaibel divided-wall column,KDWC)可在一个塔内实现四组分混合物的高纯度分离。本文以分离苯、甲苯、二甲苯和均三甲苯为研究对象,建立了KDWC严格稳态模型,获得了优化的塔体结构。通过研究KDWC分离17组进料组成的基础上,获得了KDWC的稳态分离的初步规律:实现KDWC的高纯度分离,既需要通过分液比控制预分馏段顶部馏出气相中的二甲苯含量,又需要通过分气比控制预分馏底部馏出液相中甲苯含量;两个侧线的组成中,重组分杂质的含量要远多于轻组分杂质的含量;中间组分甲苯在预分馏段仍有返混。随后,在Aspen Dynamic环境下建立了KDWC的组分控制模型,控制结果表明该模型可以应对±10%的流量和进料组成波动,但二甲苯产品纯度会出现少量偏差。

Kaibel divided-wall column（KDWC） permits separation of a four-component mixture into four pure fractions in a divided-wall column. This work studied separation of a four-component mixture of benzene, toluene, o-xylene and tri-methyl-benzene in a KDWC. The optimum economic design of the Kaibel divided-wall column was obtained. Then seventeen cases of various feed compositions were investigated for obtaining the steady state behavior of the KDWC. Xylene should be controlled at the top of the prefractionator, while toluene should be controlled at the bottom of the prefractionator; the content of heavy impurities was much larger than that of the light impurities in the two side streams; the intermediate component, toluene re-mixed in the prefractionator. At last, a control structure with five composition control loops was established. Simulation showed that it could handle ±10% disturbances of flow rate and feed composition, but the purity of xylene sometimes had small deviations.