Investigation of the fertilizer fire aboard the Ostedijk
Jervis, Freddy Xavier
This paper provides an account of a self-sustaining decomposition event of the NPK (Nitrogen, Phosphorous and Potassium) fertilizer freight aboard the ship Ostedijk. The fire developed inside the cargo hold for several days until it was controlled. Analysis of plume images shows a rapidly growing fire and provides an estimate of the evolution of the mass loss rate, ranging from approximately 0.5 kg·s-1 the first day to 12 kg·s-1 on the last day. Small-scale experiments were conducted to gain an insight into this incident. A three step decomposition mechanism is observed leading to a self sustained reaction eaching 250-275 °C. The measured heat of reaction is 6.1 MJ/kg, about one third of the value for flaming wood. Measurements are applied to the Ostedijk events and allow estimation of the maximum fire size to be in the order of 70 MW. Incidents of this nature challenge the traditional concept of fire, since self-sustaining decomposition events are thermal runaways involving exothermic reactions but not based on oxygen chemistry. However, application of fire engineering concepts and experiments allows the study of the processes.