Explosion at a hydro-treatment unit of a refinery

In a residual-oil hydrotreatment unit (also called residual oil hydrogenation) plant, a hydrogenation unit caught fire with a huge bang, followed by a fireball in the form of a mushroom cloud. Black smoke began to billow up in the sky and was clearly visible from several kilometres away

Both INITIATING and ROOT CAUSES are unknown. Although it is probable that hydrogen was at least one of the flammable gases contributing to the starting of the fire, without knowing the causes it is not possible to conclude on the role of hydrogen.

hydrogenation unit

DESCRIPTION OF THE PROCESS
The hydrotreatment process is also called residual oil hydrogenation. Residual oil is the residue remaining after the distillation and processing of petroleum. “Oil hydrotreatment” refers to the purification of the oil from harmful impurities such as sulphur, nitrogen, and metals. In presence of a catalyst, the hydrogen reacts with these components, forming hydrogen sulphide, ammonia and metal sulphides. At the same time, some of the larger molecules of the residual oil are cracked and hydrogenated into smaller molecules, which also react to produce metal sulphides.

four persons lightly injured, no impact to air quality and environment.