Applying Proper Dispersion Models for Industrial Accidental Releases
Even though many industrial facilities have put extra efforts to prevent accidental releases of active and inactive chemicals from processes or storage, accidental releases do happen from time to time due to many reasons. Federal and state regulations require industrial facilities to evaluate and report the impacts of potential accidental releases in terms of distances to toxic endpoint concentrations or radius of exposure at threshold values. When an accidental release occurs in the real world, industrial facilities would also need to evaluate the impact of the release scenario. This kind of industrial accidental releases typically lasts for a limited time period (e.g., from minutes to hours). Many dispersion models (e.g., DEGADIS, SLAB, INPUFF, or ALOHA) are available and designed to perform the dispersion analyses for different accidental releases. However, choosing a proper dispersion model for an industrial accidental release is not a straightforward process. It depends on many factors such as the emission source characteristics (e.g., released chemicals, chemical properties, released source orientation, and release conditions), plume characteristics (e.g., dense gas plume or neutrally buoyant plume) and atmospheric conditions. Analyses will be even more complicated if chemical reactions involve upon release. This paper will compare various dispersion models readily available in the public domain for industrial accidental releases. The fundamental theories and dispersion techniques utilized by each model will be analyzed. Strengths and shortcomings of each model will also be listed. Case studies of industrial accidental release scenarios will be presented to help industrial facilities to identify proper models for different accidental release scenarios.