Study On The Extractive Distillation Of Acetic Acid Wastewater

The pharmaceutical industry is closely related to human life and health.As a bulk active pharmaceutical ingredients,vitamin E is often produced with a large amount of acetic acid waste water,which leads to the waste of acetic acid resources and causes serious environmental problems.In this paper,the present treatment methods of acetic acid aqueous solution are compared and studied,among which extractive distillation method has the advantages of larger productivity,lower energy consumption and repeatable use of extraction agent,so it is adopted in this paper.Firstly,based on the characteristics of acetic acid aqueous solution and the previous literature simulation experience,NRTL-HOC was selected as the physical method in Aspen Plus,and quinoline was selected as the extractant according to literature for the extractive distillation of acetic acid aqueous solution.The ordinary distillation and extractive distillation simulation process were established in the Aspen Plus software,the effect of key parameters such as the total number of stages,the feeding stage,the amount of extractant,and the reflux ratio on the separtion performance was studied and the optimal process parameters were determined.The results showed that,on the premise of completing the same separation index(acetic acid?98.0%),the extractive distillation saved 54.79%of energy consumption compared with the ordinary distillation for the separation of 48.0%acetic acid aqueous solution.Secondly,The experimental equipment was established,and the batch distillation method was used to separate acetic acid aqueous solution.The results showed that the ordinary distillation could not meet the separation requirements,while the extractive distillation could accomplish the task.The purity of acetic acid product was above 98.0%and the recovery of acetic acid was about 98.0%.It was also found that the acetic acid content in quinoline should be below 5.0%for the recycling of quinoline.Finally,the industrial extractive distillation practice of acetic acid aqueous solution was carried out.The industrial unit was designed,and the process package was developed.The results showed that the extractive distillation unit could treat 12,000 t/a of acetic acid aqueous solution stably,and produced 3,600-6,000 t/a of acetic acid,the benefits of 2,595,900 yuan could be obtained annually.The industrial practice showed that good economic and social benefits could be achieved for the treatment of acetic acid aqueous solution by extractive distillation with quinoline as extractant.