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Nitration plant residue exothermic runaway

Published on 21/11/23 365 Views

Mononitrotoluene (MNT) was being manufactured under controlled conditions. In the period immediately before the incident, heavy heel materials that had accumulated at the bottom of an intermediate storage tank over many years was being removed to enable re-purposing of the tank. The heel material was charged to the vacuum still where it was distilled satisfactory. However, the residue did not drain from the stillbase vessel and became more viscous and harder as it cooled. The vessel was opened for cleaning for the first time in 30 years. A decision was taken to warm the residue using the stillbase internal steam batteries. A few hours later, while the warmed residue was being manually raked out, a 60 m (197 ft) long jet fire emerged from the open manway. Five people were killed.

Ask yourself and your crew:

  • How can something like this happen here (e.g. on our site)?
  • What safety measures (i.e. procedures, controls/barriers) do we have in place to mitigate the risk?
  • How do we know the risk controls/barriers are working?
  • What improvements or changes should we make to the procedures, controls/barriers or the way we work?

Original content courtesy of IChemE Safety Centre