Explosion in the desulphurisation unit of a refinery

A tube in the preheater of the desulphurization reactor leaked, and the released hydrogen ignited and exploded inside the heater enclosure. The damage was confined to the preheater.

[Zalosh and Short, 1978]

Rupture of hydrogen or process gases tubes in pre-heaters /heat-exchangers / fired heaters is a recurrent event up to recent times. This is not surprising, considering the high temperatures and pressures involved. The most common causes are materials degradations due to manufacturing defects and operative stresses. Ruptures tend to happen during operative transients, which may cause over-heating due to reduction of flows. When the releases occur also in presence of naked flames, as in fired heaters, which use conventional fuels burners, ignition and explosion in the confined of the heater box is ensured. Nevertheless, due to sturdy heater constructions, it rarely happens that damage extends to the outside environment.