Methodology for comparison of chemical process routes based on environment, health and safety aspects at early stages of chemical process plant design

Abstract

The chemical process route selection is one of the important decisions that needs to be taken during initial stages of plant design and development. Although conventionally the economic factor has been considered in this selection process, presently the environmental, health and safety (EHS) issues have also become main concerns as hazards related to EHS can be largely reduced by avoiding them during initial stages of plant development. Therefore, in order to select a route, the assessment of alternate chemical process routes based on EHS aspects and their comparison need to be carried out. For this assessment, comparison and selection methodologies are needed. Most of the methodologies available for chemical process routes assessment and selection, consider mainly environmental or health or safety hazards individually or in combination of two of them. Although few methodologies are available that consider all three EHS aspects, those that consider EHS hazards posed by both types of releases namely daily plant operational and accidental are lacking. In this work fuzzy based inherent environmental, health and safety hazard index called EHS-Fuzzy Index is developed to compare chemical process routes based on integrated EHS hazards due to daily operational activities of the plant as well as accidental releases. The EHS-Fuzzy Index includes information of thirteen EHS related parameters which is available during routes selection stage. The lower the EHS-Fuzzy Index the more environmental friendly, occupational healthy and safer the chemical route. Further, this methodology can be used to compare and rank alternative chemical routes based on environmental hazard or health hazard and safety impact separately as well. The EHS-Fuzzy Index was applied in a case of six routes to manufacture methyl methacrylate (MMA). The Tertiary Butyl Alcohol (TBA) chemical route to manufacture MMA showed the least EHS-Fuzzy Index value. By applying the MMA case study in the radial polygon diagram method, the results obtained using the EHS-Fuzzy Index methodology were verified.