(231a) Effect of Ambient Condition and Terrain Structure on the Dispersion of Accidentally Released Toxic Chemicals

In regions with sophisticated large scale chemical industrial cluster, the community has a substantial risk of being exposed to constant air pollution by toxic or criteria air pollutant chemicals. They are also susceptible to severe catastrophic exposure to toxic or hazardous chemicals in the case of any unplanned/accidental chemical releases from process units of a facility. Facility workers are also at high risk of exposure to the released toxic chemicals. Exposure to high concentrations of toxic chemicals can cause serious health hazards and even death. In the situation of an accidental release, emergency response and evacuation plans should be quickly implemented to minimize dire consequences. Furthermore, chronic exposure to higher than permitted concentrations of a hazardous chemical may lead to the slow development of serious health problems such as cancer, lung disease, etc. This kind of unpermitted release should also be addressed and minimized to ensure a safer and sustainable environment. A mathematical simulation can provide comprehensive understanding about the dispersion trend of a chemical depending on its properties, ambient condition, and terrain structure. A proper plan for reduction of pollution along with an efficient emergency response and a rescue action plan can be developed based on the mathematical simulation.

A finite element analysis model of released airborne toxic chemicals from an industrial process unit, such as a chemical storage tank into the surrounding atmosphere has been developed using COMSOL Multiphysics. This is a high-resolution model using very small element size compared to the whole geometry size. The diffusion and convection of the released chemicals through ambient air is the prevailing driving mechanism of transport. The dispersion trend has been estimated by using Fick’s 2^nd law of diffusion integrated with convection by velocity field of air. Velocity fields for different wind speeds have been calculated by using compressible forms of the Navier-Stokes and continuity equations. Transport and thermodynamic properties of air and chemical species are estimated at different temperatures and pressures. Dispersion trends of different pollutant species were calculated in different scenarios including i) different wind speeds, ii) different wind direction, iii) different obstructed terrain, and iv) different humidity. The calculated results were analyzed to study impacts of the above variables on the propagation of chemical species over time.