PROCESS constructed multiple simulation models for the multi-tower purification of intermediate and final specialty organic chemical products. The intermediate product purification involved two towers: Tower 1 for separating the intermediate product and residues (bottoms) from the excess organic raw material and water (distillate) and Tower 2 for separating the residues (bottoms) from the intermediate product (distillate). The final product purification also involved two towers: Tower 3 for separating final product (bottoms) from all impurities (distillate), and Tower 4 for separating heavy impurities and trace product (bottoms, recycled to Tower 3) from light impurities (distillate). Tower 1 included an overhead decanter to separate water (product) and raw material (reflux) and a side draw for high-purity raw material for recycle, and had to be evaluated considering the water / raw material minimum boiling azeotrope. Multiple runs were required for all towers for the purpose of selecting the best tower for each application from several packed and trayed towers that were available at the plant as well as for selecting and/or designing distillation system ancillary equipment (overhead condensers and receivers, reboilers, and product pumps). Due to the specialty nature of the organic chemicals involved, laboratory vapor-liquid equilibrium data had to be developed by the client and regressed by PROCESS in the simulation software thermodynamics package.