关键词: DWDC, Process flexibility, Process operability, Black-hole problem, Feed thermal condition

Abstract: Because of the complicated interplay between the prefractionator and main distillation column involved, the black-hole problem might occur and prohibit the assignment of four specifications to dividing-wall distillation columns (DWDCs) (e.g., the three main product compositions plus an impurity ratio in the intermediate product), which lowers terribly process flexibility and operability. In this paper, a feed thermal condition adjustment strategy, achieved by the installation of a pre-heater in feed pipeline, is employed to eliminate the black-hole problem and serve to enhance process flexibility and operability. Through the strong influence to the overall mass and energy balance of the DWDC, the feed thermal condition adjustment can alter the interlinking flows between the thermally coupled prefractionator and main distillation column and work effectively to coordinate their relationship. A DWDC separating a benzene, toluene, and o-xylene mixture is chosen to ascertain the feasibility of the philosophy proposed. The static and dynamic studies demonstrate that the feed thermal condition adjustment is an effective way to refine process design and can completely eliminate the black-hole problem and elevate consequently process flexibility and operability.

Key words: DWDC, Process flexibility, Process operability, Black-hole problem, Feed thermal condition