Semicontinuous processes have been studied in recent years for many purposes, including extractive, azeotropic, and reactive distillations, and reactive liquid-liquid extraction. in this paper, using a continuous process as a base case, heuristics are introduced to create semicontinuous process designs. The methodology for synthesizing a semicontinuous separation process (including the process units, connectivity, control system, integration with chemical reaction(s), and choice of transitional modes) is presented based on experiences involving prior case studies. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.