Feb 19, , 2017 Oberhausen, Germany.
In a shocking incident at a plant owned by Hamm Chemie, Germany, employees apparently mistakenly unloaded Hydrochloric Acid (HCl) from a tanker into a 600 m3 tank that contained Oleum (97% concentrated Sulfuric Acid or H2SO4). This led to a massive reaction and the resultant vapor cloud caused about 150 people in the town of Oberhausen to be hospitalized. Among the injured are 40 chemical plant staff, while the remaining 110 are people working at an industrial facility nearby, according to Spiegel reports.
What could have gone wrong? Likely cause is human error, but this possibility is normally always analyzed in a HAZOP Study. Not sure if it was done here. Normally, there should be several safeguards in place such as color coded hoses/pipes, checklist before unloading, verification by either a colleague or supervisor and so on. Apparently either these systems were not in place or not adequately protected against failure or were not followed. The authorities seem tight lipped and not much is being revealed as to exactly how this happened.
So what can happen when you pump (apparently dilute) HCl into concentrated H2SO4? Well the Sulfuric Acid will likely react violently with the water in the HCl and form some kind of vapor that is composed of H2SO4 fumes, as well as some complex compound. This will definitely be irritating to the upper respiratory tract and could cause some damage to it, if inhaled by humans and/or animals.
Here is drone footage from RT that is posted on Youtube.