Lecture 9 Flashcards
What were early examples of explosive accidents related to?
- ## A lot of accidents involved the confinement / storage of propellant
Delft Thunderclap in 1654 in the Netherlands
- Over 100 people died including painter Carel Fabritius and nearly all his work
- Approximately 30 tonnes of black powder stored in barrels in a cellar
- Thought to be ignited by a lamp during a watchman’s inspection
- The lamp had an open flame which ignited a small amount of gunpowder
6/12/1917 Halifax
- In Canada the SS-Mont-Blanc collided with the SS Imo at ~1 mph.
- It was carrying picric acid, TNT, guncotton and benzene
- The collision ignited the benzene and 20 mins later it exploded.
- Detonation was equivalent to around 3 kT of TNT
- The force of the collision accidentally ignited some of the benzene which just burns and they couldn’t stop it burn.
- The heat generated from the fire possibly caused the detonation of the explosive
- TNT is not a sensitive secondary explosive but the presence of guncotton (primary explosive) explains how the TNT could have detonated.
S5 Richard Montgomery
- Ran aground off the Kent Coast in 1944
- Still loaded with equivalent to 1.4 kT of TNT
- They didn’t want to tamper with explosives so they left them.
As TNT is a secondary explosive, they thought it wasn’t a big deal. - However, there is concern about redox reaction occurring with copper to form copper azide which is much more sensitive.
Example of a tertiary explosive involved in an explosive accident.
- In 1921 a plant in Oppau, Germany was producing a mixture of ammonium sulfate ((NH4)2SO4) and ammonium nitrate (NH4NO3)
- To break up and remove the hygroscopic plaster-like substance pickaxes and dynamite were used!
- This was considered ‘safe’ as the mixture was only expected to explode at >2:1 NH4NO3:(NH4)2SO4 and the mixture was wet.
- Researchers were working on drying the mixture so it became more sensitive and was detonated
What type of explosive is ammonium nitrate?
It is a tertiary explosive except when it’s in the presence of fuel
What does hygroscopic mean?
This is when a material absorbs water very readily from surroundings which is really hard and difficult to mine
Beirut Explosion August 2020
- Initial reports were of a huge explosion from the port area (17:55)
- Initial fire in a warehouse 🡪 firefighters reported “something wrong” and a “crazy sound”
- The first explosion was relatively small and occurred at 18:07 equivalent to around 2 tons of TNT
- Second explosion 30 seconds later was huge and equivalent to 0.5-1 kT of TNT
What caused the Beirut explosions?
- The first fire was likely ignited by a welding door in the warehouse.
- This ignited some of the stored fireworks containing black powder or flash powder.
- The fireworks were contained in a small area so it is theorised this is why they detonated rather than deflagrated.
- The main detonation consisted of 2.7 kilotons of ANFO
What is fuel oil?
- Fuel oil is a diverse mixture of different hydrocarbons so it is difficult to calculate ANFO oxygen balance
- It mostly consists of CH2 units
Give the equation for a theoretical fuel of any C length using ANFO
- 3NH4NO3 + “CH2” → 7H2O + CO2 + 3N2
- This gives an oxygen balance of 0
Assuming that we’re fully oxidising, what would be the ideal mass of ANFO to form CO2?
- Determine the balanced equation
- Calculate the total idealised MW of the reactants (Don’t worry about the fuel oil C chain length, only account for 1 but account for all ANFO)
- Calculate the % weight of ANFO (MW of ANFO / MW of total idealised)
- Calculate % weight of fuel oil (MW of fuel oil / idealised MW)
- This provides an approximate ideal composition by mass for ANFO
What is the true oxygen balance of ANFO?
- The true oxygen balance of ANFO is slightly negative as fuel oil is really a mixture composed primarily of CnH2n+2
What does a red-coloured plume indicate?
- the formation of NO2 gases
How was the blast wave speed estimated in the Beirut explosion?
Audio and video data collected from social media coverage
