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

The incident occurred during a temporary shutdown of the distillate hydro-treatement unit. The crude oil distillation units main column overhead product was pumped to a gasoline storage tank via the straight run gasoline rundown line. When restarting the distillate hydro-treatement unit, a valve in the start-up line to the high pressure separator branching off the crude oil distillation unit main column overhead product line was opened before the line to tank was closed.Hydrogen gas at a pressure of 30 bars consequently reached the tank, caused an overpressure and caused substantial damage.

An explosion or fire occurred in a hydro-treatment unit which was processing Fluid Catalytic Cracking feedstock. It was caused by a failure in a pipe downstream from a separator, resulting in the release and ignition of hydrogen and hydrocarbons in the unit area.

An explosion and fire occurred at a reciprocating recycle hydrogen compressor during commissioning of a new Diesel hydrotreatement Unit. It happened during the reactor pre-sulphidisation step, when the recycle gas contained 9000 ppm of H2S (hydrogen sulfide) and the pressure was at 940 psig (65 bar). The failure of retaining bolts on head-end suction valve unloader of recycle cylinder on compressor allowed release of process gas. Investigations revealed that the bolts failed due to material inappropriate to prevent sulfide stress cracking) and inadequate design for the service.

The fire started as a result of an explosion in the process section of a refinery. An open structure of steelwork protected with reinforced concrete housed the usual furnaces, reactors, heat exchangers, storage vessels, overhead pipe racking, pumps and ancillary equipment associated with the refining of crude oils.Also included in the area were three 46m (150 ft.) high stripping and drying columns built on a concrete base approximately 91m x 21m (300 ft.

Localized corrosion of a FCCU (Fluid Catalytic Cracking Unit) feed Hydrotreater recycle hydrogen line by-pass around a hydrogen pre-heat exchanger led to an explosion and fire.The failed part of the line had been identified by inspection as a dead leg. After investigation it was found that the mechanism of corrosion was ammonium chloride under deposit corrosion. The source of chloride has not been traced, but hydrogen from the catalytic reformer was strongly suspected. Inadequate inspection of the dead leg was identified as the cause of this incident.

An explosion at a refinery Hydrotreater plant involving a furnace and hydrogen caused by faulty operation. Source of ignition was furnace.

The fire started 3 hours after being shut down. The unit was shut down and the fire extinguished.The oven contained only gaseous products and mainly hydrogen.