Modelling and control of the dispersion of hazardous heavy gases

Dispersion of several common 'heavy' gases (ethylene, propylene, ammonia, a nd chlorine) has been modelled on the basis of modifications in plume path theory. The model takes into account, among other things, the variations in temperature, density, and specific heat during the movement of the heavy g as plume. The effects of wind speed, density of the gas, and venting speed on the plume dispersion have been simulated. Based on the simulations a set of empirical equations has been developed. The equations have been validat ed by theoretical as well as experimental studies. Studies have also been carried out to simulate the effect of venting speed (manipulated by injecting hot air with the released gas) on the plume dispe rsion. The study reveals that the effect of venting speed on dispersion is very pronounced and can be used to reduce the risk posed by the accidental luxurious release of toxic/flammable gases. For example an increase of 20% in venting speed of chlorine (54.1 m/s) can reduce the distance up to which toxic concentration would occur by about 1100 meters. (C) 1999 Elsevier Sc ience Ltd. All rights reserved.