强化Petlyuk分壁精馏塔分离四元混合醇的动态控制

Dynamic Control of Extended Petlyuk Divided-Wall Columns for Alcohols Separation

强化Petlyuk分壁精馏塔(PDWC)可在一个塔内实现四元混合物的高纯度分离。以分离甲醇(Methanol)、乙醇(Ethanol)、正丙醇(1-Propanol)和正丁醇(1-Butanol)为对象,在优化的PDWC的严格稳态精馏模型的基础上,采用2种不同的浓度控制结构对PDWC的动态控制效果进行了研究。结果表明,2种控制结构均能对进料组分±20%的波动进行有效的控制。采用塔釜热负荷控制上、下侧线中杂质和塔釜杂质的总和的方法,可使乙醇产品纯度更接近设定值,再沸器负荷略有增加。通过最小蒸汽量V-min图分析控制过程中产品纯度偏差的原因,即当进料组成发生变化导致V-min增加时,乙醇产品纯度会略低于设定值;相反,当进料组成发生变化导致V-min减小时,乙醇产品纯度会略高于设定值。这一现象表明,进料组成波动所导致V-min变化与乙醇产品纯度的变化呈负相关性。

The extended Petlyuk divided-wall column（PDWC）could be used to separate fourcomponent mixture into four high purity products in a single divided-wall column.The separation of a mixture of methanol,ethanol,1-propanol and 1-butanol（MEPB）in a PDWC was investigated.The optimum economic design of the PDWC was obtained at first.Then,two different control structures were built and tested in face of±20% flow rate and composition disturbances.Control results showed that both of them had good control performances.The control structure with the reboiler duty to control the sum value of impurities in the two sidestreams and the bottom product had a better control result.The deviations of the ethanol purity became small,but the reboiler duty increased slightly.The minimum vapor V-min diagrams were also used to analyze the deviation reasons of dynamic control when the feed composition changed.It is found that the final ethanol purity was slightly lower than the specified value as the V-min value increased,while the ethanol purity was a little higher than the set value as the V-min value dropped,which indicated that the change of V-min in face of fluctuation of feed composition was of a negative correlation with the change of the ethanol purity.