Dispersion and thermodynamics of clouds generated from spills of SO3 and oleum.

A new model describing the dispersion behaviour and the processes that occur in a cloud generated from accidental spills of SO3 and oleum has been developed. Such a cloud may initially behave as a dense gas, with several chemical and physical processes occurring in it. There is not usually enough atmospheric moisture in the air passing immediately above the pool for complete and rapid reaction to sulphuric acid mist. Therefore in the early stages, SO3 vapour, H2SO4 vapour and H2SO4 aerosol will be present. At some distance downwind, transition to passive dispersion behaviour will take place and only sulphuric acid aerosol will be present in the cloud. The dense gas model is based on a box type dispersion model. The passive behaviour is described by a Gaussian model that takes into account deposition of the aerosol particles. The model results suggest a number of lines of experimental investigation that are required to provide data for model validation.