In the conventional heat integrated distillation column (HIDiC), the optimal heat exchange cannot be achieved because the heat exchange between the rectifying section and the stripping section is executed through the wall at the physically same elevation. To be released from this constraint, authors have proposed a new process structure in which the heat exchange is executed between several pairs of stages in the rectifying and stripping sections, and such HIDiC is hereafter called the discrete HIDiC (D-HIDiC). Authors have also developed a new graphical design procedure for D-HIDiC, in which a plausible design is interactively derived using the extended Ponchon-Savarit H-xy diagram. The proposed procedure was applied to a design problem of commercially operated column and subsequently D-HIDiC was applied at Maruzen Petrochemical Co. Ltd., Japan. Through the stable operation since August in 2016, it was verified that more than 55% energy conservation to the conventional distillation column could be achieved.
In this research, the design and operating conditions of the commercially operating D-HIDiC are explained. Though the pairing of heat exchange stages cannot be changed in the commercial operation, the column has a function of adjusting the heat exchange rate at each side heat exchanger. By using this function, the heat allocation to side heat exchangers is modified so that the heat allocation is close to the optimal condition. The effect of proper allocation of heat to the side heat exchangers on the energy-saving performance is discussed using the actual operating data. It was demonstrated that appropriate side heat exchanger allocation having similar composition-enthalpy change as the reversible distillation can achieve higher energy conservation.