EPSC Learning Sheet

Hydrogen Sulphide Explosion

Published 3 February 2020

Contributor

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What Happened?

The vacuum breaker on a tank for molten sulphur was plugged blocking the air sweep gas flow, resulting in elevated H2S concentration. An ignition source created an explosion.

H2S dissolves from the molten Sulphur

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Aspects:

Vacuum breakers can foul on the inside when products condens or solidify at a lower temperature on the top of the tank

Ventilation systems in sulphur tanks are safety critical and their function must be validated e.g. by a low flow alarm

H2S Lower Explosion Limit drops to about 3.3% at the elevated temperature applied to keep the Sulphur molten

In this case the ignition source might be from a spark related to flowing molten sulphur, that is an accumulator for electrostatic charges (here during a truck loading)

Grounding and bonding of sulphur tanks is critical, as well as follow-up of the EX zone inside the tank

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