RCM and DRD

The dominance of distiHation-based methods for the separation of Hquid mixtures makes a number of points about RCM and DRD significant. Residue curves trace the Hquid-phase composition of a simple single-stage batch stiHpot as a function of time. Residue curves also approximate the Hquid composition profiles in continuous staged or packed distillation columns operating at infinite reflux and reboil ratios, and are also indicative of many aspects of the behavior of continuous columns operating at practical reflux ratios (12). 

Although batch distillation is covered in a subsequent separate section, it is appropriate to consider the application of RCM and DRD to batch distulation at this time. With a conventional batch-rectification column, a charge of starting material is heated and fractionated, with a vapor product removed continuously. The composition of the vapor prodiic t changes continuously and at times drastically as the lighter component(s) are exhausted from the stiU. Between points of drastic change in the vapor composition, a cut is often made. Successive cuts can be removed until the still is nearly diy. The sequence, number, and limiting composition of each cut is dependent on the form of... 

D/B = distillate-to-bottoms ratio, RCM = residue curve map, DRD = distillation region diagram, and MSA = mass separating agent. 

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