I’ve just started learning *Aspen recently, and I encountered a problem example; I hope experts can guide me on how to approach it.
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During the production process, high-concentration organic wastewater containing isopropyl ether, isopropanol, and water is generated; in the wastewater from one factory, isopropyl ether accounts for 7 wt%, isopropanol for 13 wt%, and water for 80 wt%. Design a reasonable distillation separation process to recover isopropyl ether and isopropanol from this wastewater. Design conditions: (1) A certain factory has an annual production capacity of 100,000 tons of isopropanol, resulting in a wastewater flow rate of 1 ton per hour under normal temperature and pressure conditions. (2) The existing thermal utility is steam at 0.5 MPa (gauge pressure). (3) The cold utility is circulating water (30°C). Requirements: (1) Continuous operation. (2) The content of isopropyl alcohol in water is less than 20 ppm, and the content of isopropyl ether is less than 100 ppm. (3) In addition, it is required that the isopropyl ether concentration be ≥98 wt% and the isopropanol concentration be ≥99 wt%. (4) Operating costs should be as low as possible.
Boiling point of isopropyl ether (°C): 68.5. Boiling point of isopropanol (atm, °C, 101.3 kPa): 82.45. Their boiling points are lower than that of water; it is therefore crucial to remove isopropyl ether and isopropanol from water first. Check the information to see if they form azeotropes with water. After dehydration, the two are separated by distillation.
The key point is that the Aspen simulation showed that the alcohol content in the bottom of the tower would not meet the requirements, so it’s not feasible. I also tried using Aspen to have the ether come out from the top of the tower and water and alcohol come out from the bottom, but that didn’t meet the requirements either. These three substances can form an azeotrope, so it’s not clear what the order of separation should be.