Approximate estimation of operational variables in fully thermally coupled distillation columns using pseudo-pinch points

An approximate procedure for the estimation of operational variables in fully thermally coupled distillation columns (FTCDCs) using two pseudo-pinch points of the feed and side draw trays is proposed, and its performance is examined with two example processes. The estimates from the proposed procedure show some 20% error compared with the results of rigorous simulation using commercial design software, the HYSYS. In addition, the relation between vapor flow rate and composition at one stage above the feed tray-required in the estimation of operational variables of the FTCDC-is analyzed to give information for the selection of the feed tray composition. A preliminary evaluation of operational variables helps to screen unrealizable design obtained often from iterative trial procedures employing the mathematical programming.