In many chemical processes

large amounts of wastewater containing butanol and isobutanol are produced. Given that n-butanol-isobutanol-water can form triple azeotrope

high-purity butanol cannot be recovered from the wastewater by ordinary distillation. To economically and effectively recover butanol from this kind of wastewater

1

4-butanediol is selected as an extractant to break the formation of the azeotropes

and a doubleeffect extractive distillation process is proposed. The conceptual design of the proposed process is accomplished based on process simulation. With the proposed process

the purity of recovered butanol and water is greater than 99.99 wt%. In comparison with the conventional azeotropic distillation process

economic analysis shows that the operating cost of the proposed process is lower:when the capacity of wastewater treatment is 100 t·h

-1

the total operating cost decreases by 5.385×10

6

USD per year

and the total annual cost of the new process decreases by 5.249×10

6

USD per year. In addition

in the extractive distillation system

variable effects on separation purities and cost are more complex than those

in the ordinary distillation system. The method and steps to optimize the key variables of the extractive distillation system are also discussed in this paper and can provide reference for similar studies.