Abstract
In order to examine the effect of the internal heat exchange between the stripping section and the pressurized rectifying section, an experimental setup of twin plate-columns thermally linked together with heat transfer tubes was constructed as a simulator of heat-integrated distillation column (HIDiC), each of which has its own reboiler and overhead condenser. Each column having five stages of dualflow tray with no downcomers called “Lift Trays” was filled with the same composition of benzene-toluene binary mixture but independently operated at different pressures. The one was kept at 0.1 MPa serving as the stripping section while the other was operated at 0.1 or 0.15 MPa simulated as the pressurized rectifying section. Five rectangular heat transfer tubes per stage open on the higher-pressure column were inserted into each space between two neighboring trays in the lower-pressure column so that the internal heat integration could be achieved effectively: the inside surface of each heat transfer tube has additional condensation of the higher-pressure column vapor and the outside surface has additional evaporation of the lower-pressure column liquid. The heat transfer characteristics were observed evaluating the difference in the net heat input between when the twin columns were operated at the same pressure 0.1 MPa and when one of them was pressurized up to 0.15 MPa. The rate of heat transfer between the two columns was also determined directly from the enthalpy balance. It has been found that the experimental overall coefficient of heat transfer between the lower- and higher-pressure columns becomes of the order between 400 and 1,000 W/m2K and that within the operating condition of internal heat integration the average plate efficiency still remains in the range between 40 and 90 %.
