| Most of simple unitary fatty alcohols will form azeotrope with water under atmospheric pressure,and it is difficult for the ordinary distillation process to meet the separation requirements.The typical industrial binary and ternary alcohol water azeotrope are studied,different energy-saving process are proposed,using chemical process simulation software Aspen Plus.The processes are optimized to meet the lowest total annual cost(TAC)which is set as the objective function.Then,Aspen Dynamics is used to study on dynamic control with different process respectively.In this paper,the energy saving separation of n-propano/-water azeotrope system was firstly studied,and the extractive distillation dividing-wall column(EDWC)and the azeotropic distillation dividing-wall column(ADWC)were designed.The optimization results showed that the TAC of both processes are significantly lower than that of conventional extractive distillation process.Since the above two kinds of rectifying adjacent tower have certain practicability,the dynamic controls of them have been studied.The R/F proportional control structure with fixed vapor distribution ratio and V/L proportional control structure with temperature controller are proposed for EDWC.The Qr/F proportional control structure with fixed liquid distribution ratio and composition-liquid level cascade control structure are proposed for ADWC,which can deal with the 10% feed disturbance and have a good control performance for the above two kinds of dividing-wall column.In order to further explore the separation of multiple alcohol-water azeotrope systems,the energy saving separation of two typical ternary azeotrope systems,ethanol/tert-butanol/water and ethanol/acetonitrile/water,was studied.In view of the presence of two azeotrope in ethanol/tert-butanol/water system at atmospheric pressure,the extractive distillation column with multiple rectifiers(MR-EDC)was designed and optimized based on the design of the conventional three-columnextractive distillation process(CED).The optimization results showed that MR-EDC had better energy saving advantages,and the TAC can reduce by about 16.16%compared with CED.A CC-R control scheme is proposed for the MR-EDC process.For ethanol/acetonitrile/water system with three binary azeotrope and a ternary azeotrope at atmospheric pressure,the extractive-pressure swing distillation process(E-PSD)and pressure swing-extractive distillation process(PS-ED)were designed and optimized.Then the two kinds of processes of the economy were compared,and the results show that the TAC of PS-ED can be saved by about 6.69% compared with E-PSD.Based on the control analysis of PS-ED,the fixed reflux ratio and the component-temperature cascade control scheme are proposed,which can effectively deal with 20% feed disturbance and effectively control the flow.The above research shows that extractive distillation has a better separation effect for the separation of alcohol-water azeotrope.And it can play a significant role in energy saving and consumption reduction by matching with the appropriate energy saving process.The above results have a general adaptability for the extraction distillation separation of alcohol-water system.In the aspect of dynamic control,the composition control scheme with feed forward control has a wide range of adaptability to extractive distillation. |
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