Heat and Mass Transfer of Internally Heat Integrated Distillation Column (HIDiC)

Abstract

Distillation is the most frequently-used separation process in the chemical industry. Distillation columns account for about 40 % of the total energy consumption in chemical plants, so energy savings in distillation processes are highly desirable. Internally heat integrated distillation columns (HIDiC) are one of the most promising alternatives to conventional distillation columns. Our present design of HIDiC has a similar structure to a heat exchanger (Fig. 1). In the HIDiC, the distillation column is divided into two parts, rectifying and stripping sections. The pressure in the rectifying section is raised by compressing the vapor flow from the top of the stripping section. Physical contact between all or part of the rectifying section with the stripping section then allows internal heat exchange. If the temperature of the rectifying section is appropriately higher than that of the stripping section, the residual heat in the rectifying section can be used as a heat source for the stripping section, resulting in lower requirement for reboiler heat. At the same time, the vapor and the liquid flow rates in the rectifying section are decreased towards the top due to the condensation caused by the internal heat exchange, resulting in reduction of the external reflux ratio. The idea of the HIDiC was first proposed by Haselden for energy savings in cryogenic air separation1). Later the idea was reintroduced by Mah et al.2), and the outline of the present design of the HIDiC was established. In Japan, the fundamentals and practical application of the HIDiC have been studied by Takamatsu et al.3) since the 1980’s. Their great efforts have lead to construction of prototypes and pilot plants of the HIDiC. In particular, the HIDiC pilot plant in Maruzen Petrochemical Co., Ltd. has succeeded in 189 Journal of the Japan Petroleum Institute, 58, (4), 189-196 (2015)