“…With the beginning of the seventies the big German players in chemical industry started developing own programs for the calculation of distillation/absorption columns (Hoechst AG , Bayer and BASF ). The extension to simulation of entire or parts of chemical processes including recycles was evident and was available in the 1980s . In Wozny et al , beside commercial simulators like ASPEN, Speedup and PROCESS, many of the different inhouse programs of the chemical industry are mentioned (OPTISIM – Linde, CHEMASIM – BASF, VTPLAN – Bayer and HORUS – Henkel), from which the major part is still in use today.…”