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This looks to be like a BLEVE - Boiling Liquid / Expanding Vapor Explosion, or as we call it "Blast Leveling Everything Very Effectively". They are scary as all get out and incredibly powerful (as you can see here) which is why we evac such large distances. So what causes it? https://twitter.com/tobiaschneider/status/1290670226934243329
First, a little chemistry. As you know, liquids vaporize into gas, and gas tends to expand rapidly. For example, LP Gas expands from 1 gallon liquid to 270 gallons vapor. So full containers are safer than empty ones, because the gas has less room to expand.
Second, gases need a specific mixture of air/gas to ignite. For LP Gas that's around 2-9% of fuel to air. Too much vapor and it's "too rich". Too little and it's "too lean". (I don't know if this was LP Gas, just using it as an example)
Now, in a BLEVE situation, you have a tank filled with liquid product. A fire happens near it and starts heating the tank. But that heat gets absorbed by the liquid, protecting the metal from the tank. Pressure starts to build in the tank, which gets released by safety valves
As the pressure lowers inside the tank, the valve shuts. But then will reopen when pressure builds again. The problem is that you're now losing the liquid as well, and the fire starts to heat up the part of the tank where there is no liquid. This can cause the tank to weaken.
Eventually the pressure causes the weakening metal to fail, releasing a large amount of gas, which then hits the flammability point in the heat source and rapidly expands all of the vapor, incredibly violently.
Here's a training video on them showing how fast and violently it all happens
But to give you a sense, here's a three-shot compilation over the span of 3 seconds or so showing how fast it happens. And that's a tiny tank!
Anyway, when you see fire and then giant explosions - especially at ports - it's likely a BLEVE. And also, if you live near a place with giant tanks and they ask you to evacuate - you should probably listen to them.
Adding to the thread that the government is saying it was a ship filled with fireworks that exploded. https://twitter.com/DavidADaoud/status/1290675984983785472
https://twitter.com/mannyfidel/status/1290674876110569473 is an amazing video of it because you can see an initial explosion, a secondary one, and then the vapor shock wave. Also the total leveling of that building in front of it.
Adding this view to the thread because you can clearly see the fireworks going off and then the amount of destruction from the shockwave. I hope they were able to evacuate people before the explosion https://twitter.com/borzou/status/1290675854767513600
Adding to the thread what kind of expected injuries you get in a blast like this and how they're categorized: https://twitter.com/cory_foy/status/1290683979797016576
Adding to the thread that the fire was next to a warehouse with nitrates. As in the stuff commonly used in homemade explosives https://en.wikipedia.org/wiki/Ammonium_nitrate#Explosives https://twitter.com/sewella/status/1290678063643140097
Adding a tweet from a chief I highly respect about his view on it https://twitter.com/GreggFavre/status/1290687119896317952
Adding this video - you can see the fire load increase through the windows just before the explosion https://twitter.com/HeshmatAlavi/status/1290683991369097216
A raw on-the-ground video of some of the damage from near the blast site https://twitter.com/Lobnene_Blog/status/1290675724416884739
Adding since a lot of people are reading this - it doesn't need to be a BLEVE to cause that kind of explosion. Fireworks + Nitrates (which is what they're reporting now) can cause some very big explosions is an example of one from Texas in 2013
Adding two more things and then calling this thread. First, a informative thread about Overpressure / Blast waves https://twitter.com/GreggFavre/status/1290695098087477248
And then footage from near the port showing some of the aftermath. Prayers for everyone impacted - this is truly devastating and my heart sinks to think about the injuries, deaths and destruction over there and how big of a blow this is to them 
https://twitter.com/habib_b/status/1290691644170342401
https://twitter.com/habib_b/status/1290691644170342401
