Numerical Descriptive Inherent Safety Technique (NuDIST) for inherent safety assessment in petrochemical industry

Abstract

This paper discusses the development of a new approach of inherent safety assessments called the Numerical Descriptive Inherent Safety Technique (NuDIST). Most current methods for assessing inherent safety use an index-based method. Among the disadvantages of such methods are the use of scaling in which hazards are divided into physical or chemical properties with subjective ranges and discontinuity at the sub-range boundaries. This new technique uses numerical assessment methods, can overcome the limitations inherent in the index-based methods and provides insights into the effect of safety parameters, i.e. temperature, pressure, heat of reaction, process inventory, flammability, explosiveness, toxicity and reactivity for the petrochemical industry. The results of the assessment can be used to easily identify the safest route among several alternatives for chemical synthesis or process retrofitting in addition to, highlighting potential sources of hazards. The proposed technique was tested using the methyl methacrylate manufacturing process. This test highlights the superiority of the Numerical Descriptive Inherent Safety Technique (NuDIST) over index-based methods. The results show that among the six routes of the MMA manufacturing process, the tertiary butyl alcohol (TBA) based route has the lowest total score and is considered the safest route, whereas the ethylene via propionaldehyde (C2/PA) based route has the highest score.