Risk Assessment Methodology of NOx in the Cryogenic Section of Ethylene Plants

Assessing the safety risks of NOx in a cryogenic section of an ethylene plant is difficult because the hazard is a result of complex chemistry, a function of many site specific parameters, and limited available industry data.  This paper provides a methodology for doing a quantified risk assessment.  The paper discusses key site parameters that influence the risks associated with NOx and how the limited available industry data can be used.  In addition, the paper will present an event tree that can be used as a template for the risk assessment.  The combination of a quantitative overall risk assessment and a quantitative understanding of the factors that influence that risk can help sites to be better positioned to manage the NOx hazard.