Basic Design of a Double-Pipe Unit Type Internally Heat Integrated Distillation Column (HIDiC)

A heat integrated distillation column (HIDiC), which is featured by a greater potential of energy savings than its conventional counterparts (Takamatsu et al., 1997; Nakaiwa et al., 1998), has been successfully operated with a supreme energy saving as a pilot plant. The HIDiC pilot plant consists of seven Double Pipe Units. The Double Pipe Unit is a separating and heat transferring unit that the inner pipe functions as a rectifying section, the outer pipe as a stripping section, and the wall of the inner pipe as a heat transfer area. The diameter of the inner pipe is altered in the axis direction corresponding to the vapor and the liquid flow rates since they increase upward in the rectifying section and decreases downward in the stripping section. The diameter of inner pipe must be designed on two view points, the first is vapor load and the other is heat transfer area. The pipe length is related to not only packing height in the rectifying section and the stripping section but also the heat transfer area. It is suggested by our experiments that the diameter of the outer pipe can be up to 500mm and the feed flow rate can be increased by additional Double Pipe Units. For example, above-mentioned HIDiC pilot plant has seven Double Pipe Units.