Computer aided estimation of fugitive emission rates and occupational air concentration in process design

摘要

European Union directives such as the Integrated Pollution Prevention and Control (IPPC) require inclusion of safety, environmental and health analyses in process design as part of strategies towards achieving sustainable process development. In petrochemical and organic chemical industries, which mostly handle volatile compounds, the most significant contributor to atmospheric releases is fugitive emissions that are mainly contributed by piping fittings and components. Fugitive emissions are not only of economic and environmental concern, but also a major source of background inhalative exposure to workers that may lead to various diseases including cancer. More people die every year from occupational diseases as compared to the number killed in industrial accidents. Therefore the estimation of occupational air concentration due to fugitive emission needs to be done early when developing a new process. Several methods for fugitive emissions estimation have been introduced which mostly involve manual calculations. Computer-based tools for such purpose however, are still lacking. Besides, the current methods mainly focus on the emission rates only but not on the process air concentrations. Computer aided methods for fugitive emissions assessment are highly in need, since now most of the design work is done by using computer aided process engineering (CAPE) tools. Therefore in this paper computer aided methods for quantifying fugitive emission rates and occupational air concentration are presented. Three methods are proposed for early design stages based on data available from simple process flow diagrams (PFDs), detailed PFDs or piping and instrumentation diagrams (P&IDs). The method becomes more comprehensive as it progresses from simple PFDs to P&IDs, since more process data are available later, which include plot plan, coordinates of the emission sources and local wind speed. Users however, can choose which method to use depending on the process information available in hand. The methods are demonstrated in a case study of product distillation system of toluene hydrodealkylation.