(193e) HCl Tank Explosion

Explosion in HCL tank is very rare. When searched the internet not a single case of HCL tank explosion was found. However, we have experienced it. The explosion was so powerful that the tank having capacity 250 KL, 60% filled with 33% HCL took off from the ground went up to 20-25 feet high in air and landed around 50 meters away. In this process the contents sprayed all over nearby area. Though the tank was surrounded by other plants and equipment fortunately it landed on no-mans land! This averted loss of life and property, otherwise would have caused by cascading effect.

The hazard of fire and explosion was recognised before due to small fires in tank and nitrogen blanketing was provided to take care of it. On the day of explosion plant was running in normal condition and there was transfer of HCL, to tank was going on. However, the operator noticed abnormal pressure rise in the tank in question and informed in control room. The rise in pressure was attributed to instrument fault and ignored it. And within few minutes of it there was a big explosion.

The HCL is being produced by two methods, from burning hydrogen and chlorine gas in chlorine reactor and the other one is from directly using HCL gas from VCM plant. This paper discusses in detail the acts of commission and omission by plant personnel and incident's causes. Though the exact reason of explosion could not be ascertained, all plausible reasons and appropriate recommendations were given to avoid recurrence.