There was a download of Dynsim 4.2.3 on the developer's website when we last checked. We cannot confirm if there is a free download of this software available. We recommend checking the downloaded files with any free antivirus. This program is an intellectual property of SimSci-Esscor. The following versions: 4.2 and 4.0 are the most frequently downloaded ones by the program users. Dynsim lies within Education Tools, more precisely Science Tools.
From the developer:
DYNSIM is a comprehensive, dynamic process simulation program that enables users to meet and beat the dynamic challenges of designing and operating a modern process plant safely and profitably.
You may want to check out more software, such as GenScn, Illusionae or Foucault, which might be similar to Dynsim.