The Design And Simulation Of Fully Thermally Coupled Distillation Column

Distillation has been widely used in the process industry with its highest maturityand best reliability. But it always requirs huge energy consumption, and the energysaving problem has received attentions from academia and industry. In the fullythermally coupled distillation column (FTCDC), a pre-fractionator and main tower areconnected by two pairs of gas-liquid streams. By means of this design, thereversibility of the distillation process can be improved, and the energy consumptionand equipment investment can be reduced.In this paper, by adopting a three-column model that is thermodynamicallyequivalent to FTCDC, a shortcut design method based onFenske-Underwood-Gilliand was established. By this method, preliminary decisionson the theoretical tray number, the feed and withdraw tray locations and operatingreflux ratio could be made and the values for the decision variables were then used asinitial values for rigorous simulation. Meanwhile, an optimal decision on thedistribution rate of the intermediate component at the head of the prefractionator βand its value region was made to minimize the vapor flow rate in the column.Rigorous simulation and characteristic analysis of FTCDC for separation of amixture of three components of C5-C7were performed. In the optimization process,the impact on different feed-tray locations was discussed. Then the relation of thevapor and liquid split ratios Rv and Rl with the distribution ratio β was established.And the optimum values of Rv Rl and the corresponding β that gave the lowest energyconsumption were identified. These demonstrated that a suitable pair of Rv Rl shouldbe maintained for an optimal operation of FTCDC.As an innovative energy-saving technology, a fully thermally coupled catalyticdistillation hydrogenation was proposed and investigated preliminarily in this paper.After determining the macro kinetic equation of the catalytic hydrogenation reaction,preliminary decisions on the design parameters like theoretical tray number, feed andside-draw trays locations as well as reflux ratio were made. With the analysis andsimulation, this technology showed its feasibility and advantage for the futureinvestigations.