Types of dispersion

Introduction

Exploring dispersion events involves studying how substances spread through the atmosphere under varying conditions. Whether it is pollutants from industrial emissions, aerosols from volcanic eruptions, or airborne pathogens, dispersion events are influenced by complex interactions of meteorological factors and the physical properties of the substances involved. Understanding these dynamics is crucial for assessing environmental impacts, designing effective response strategies during emergencies, and safeguarding public health. By investigating dispersion events, researchers aim to enhance predictive models that can inform policy decisions, improve air quality management practices, and mitigate the potential risks associated with airborne substances.

Exploring dispersion events

An event tree illustrating the various types of events that can result from the loss of containment of pressurised liquefied gas is presented in the figure below, where dispersion events are highlighted.

Pool evaporation occurs when a liquid chemical spills and forms a pool, subsequently evaporating into the atmosphere.

Dispersion of substances becomes particularly critical when there is a release of chemicals that are either toxic or flammable but not ignited immediately. In such scenarios, understanding how the chemical cloud will spread is essential for assessing the potential danger. Key points of interest include determining how far the cloud will travel and its concentration at various distances. By accurately predicting the dispersion patterns, we can better protect human health and the environment from the adverse effects of accidental chemical releases. An event tree aids in predicting these potential scenarios. One of the examples is the dispersion of a flammable cloud. If a flammable cloud reaches confinement, its delayed ignition can result in a Flash Fire and Vapour Cloud Explosion (VCE). If unconfined, a Flash fire will occur upon ignition. If the substance is not ignited but possesses toxic properties, such as chlorine or ammonia, its dispersion may endanger the surrounding population. Predicting the dispersion of a toxic cloud, its concentration over distance and time, and the dose received by populations at various distances from the release point is crucial.

Rising smoke plumes occur when substances are released at high temperatures, causing them to rise and disperse over a larger area. These plumes can carry pollutants and toxic chemicals, impacting air quality and health over a broad region.

This information enables emergency response teams to implement appropriate evacuation measures, industrial safety professionals to design effective containment strategies, and environmental agencies to predict and mitigate the impact on surrounding communities and ecosystems.

X-Suite for understanding dispersion

Gexcon's X-Suite, particularly tools like FLACS, EFFECTS and RISKCURVES, provide simulation capabilities to model the behaviour of gas, liquid, and pressurised liquefied gas mixtures under varying conditions. This aids in comprehensive risk assessment and safety planning.

References

Bosch, C. v. (2005). Methods for the calculation of physical effects 'Yellow book' CPR 14E. The Hague: Ministerie van Verkeer en Waterstaat.