Thermal integration of homogeneous azeotropic distillation sequences

Existing methods for synthesizing thermally-integrated distillation sequences fail frequently when applied to nonideal and azeotropic systems, because increasing the column pressures often introduces new azeotropes and distillation boundaries into the mixture, which make some separation tasks infeasible. A new thermal integration procedure is presented that combines a bifurcation and residue-curve map analysis with the methods of Andrecovich and Westerberg. The procedure is demonstrated with two commercially important separations: ethanol-water-ethylene glycol and methanol-acetone-water. Energy savings of 65% and 40%, respectively, over the optimized nonintegrated sequences are possible.