Explosion in an incinerator plant

The explosion occurred in an incinerator for non-industrial wastes, during inspection and repair works. These were due to a large quantity of aluminium which produced a solid lump of ash. The explosion occurred during clean-up operation of this lump piled in a hopper chute at the lower part of the incinerator. In an attempt to favour the cleaning process, large quantities of water were injected, which reacted with the aluminium to form flammable atmosphere consisting mainly of hydrogen. The hydrogen entered then in contact with air when the inspection door was opened, ignited and exploded.

The INITIATING cause was the reaction between hot aluminium and water, which formed hydrogen.
Two ROOT CAUSES or FACTORS:
1) A large quantity of aluminium, was brought in as non-industrial waste, while it should be which has to be managed as industrial waste. Its incineration without knowing this fact resulted in the generation of a hot clinker, which stopped operations.
2) Workers lacked safety knowledge regarding possible reactions in the incinerator. This brought to the decision to use water for clean-up.

incinerator ashes

Inspection and repair works were ongoing.

In 1983, and an identical accident had occurred, and a related report was published in 1994. Although the publication was delayed for legal reasons, it had been made public before this accident occurred.

The sources state different consequences: for one, 1 worker was injured, for the other, 2 were injured, and one died.

(a) It is crucial to be able to learn from previous cases. There was an identical accident in 1983 (although the source does not tell if in the same facility), but apparently the plant management was not aware of it, or did not recognise the return of experience.
(b) Non-industrial wastes such as domestic wastes is a mix of diverse materials, including hazardous ones. T should be possible to execute some sort of control on the materials arriving. The lack of control on the type of waste was at the basis of this incident: a facility for non-industrial waste accepted a large quantity of aluminium, which should have been labelled as industrial waste.

1. As waste including aluminium easily forms a clinker, which causes an ash blockage, it should not be incinerated in large quantities.
2. A camera and a temperature sensor to monitor ash blockage was installed in the chute.
3. Instead of forced cooling, natural cooling was adopted by water for ash removal work.
4. Guidelines for safety work were written.