Conflicts and decisions in the search for inherently safer process options

Identification of inherently safer process options is a multi-dimensional problem. Nearly all chemical processes involve a number of processing steps. Associated with each processing step there is usually a number of hazards or hazard types, for example, high pressure, high temperature, acute toxicity, chronic toxicity, fire, explosion. A process which is inherently safer with respect to one of these hazards may be more hazardous with respect to another hazard. Several examples will be discussed, including selection of refrigerants, batch vs. continuous reaction, and solvent selection for a batch exothermic reaction. These examples illustrate the importance of a thorough understanding of all of the potential hazards in the process. Finally, some tools for evaluating process options and selecting among a group of processes with conflicting inherent safety characteristics are discussed.