Formaldehyde production plant modification: Risk based decision making

In case of plant modification, one of the guiding parameters for decision making should be the risk minimisation. Traditional and recognised risk assessment methodologies (i.e. HazOp, Fault Tree, Event Tree) are static and strongly affected by the experience of the analysis team. But in case of plant modification, the team knowledge can be not sufficient. Thus, it became particularly important to have a system able to model, in an integrated way, both the probability of occurrence of possible unwanted events, and the behaviour of the process when an unwanted event occurs; this will allow the decision to be taken on a complete set of information and definitely on risk. The dynamic decision analyses are based on the results of a joint logical-probabilistic model and phenomenological model. In this paper, in particular, the Integrated Dynamic Decision Analysis is applied to a formaldehyde production plant, where a decision has to be taken about modifying the whole cooling system of the process from a melted salts based system, with a higher environmental impact potential, to a water based system.