What Caused the Massive Explosion in Tianjin, China?

In summary, the explosion that was seen on television yesterday in China was a large and unexpected explosion caused by the reaction of calcium carbide and water.
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  • #2
Yeah, when I saw the reporting on Sky News Australia yesterday morning I was shocked at the footage capturing the explosions.
 
  • #3
As the guy in one of the videos said "HOLY S***"
 
  • #4
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  • #5
Borg, your link gives a 404
 
  • #6
phinds said:
Borg, your link gives a 404
Looks like the quote didn't pick up the entire link from nsaspook that I quoted. Try it now.
 
  • #7
Yeah got it this time. Pretty cool. MAN that was a big blast for something less than an atomic bomb.
 
  • #8
Some drone video of the Aftermath. Tactical nuke range damage.

 
  • #10
Borg said:
Nice link nsaspook. I had heard that it had been picked up by weather satellites but it took a moment to realize that it was the white dot at the center of the screen. Unbelievable that you can even see an apparent shock wave spreading out from it as well.

If you loop it in reverse it's easier to analyze.
It looks like a sharp directional initial explosion that produces a focused compact blob, then a much larger unconstrained explosion with a massive wave-front that moves into the sea.
 
  • #11
Accidental FAE? Has to happen sooner or later.
 
  • #12
berkeman said:
Looked like a BLEVE...

https://en.wikipedia.org/wiki/Boiling_liquid_expanding_vapor_explosion



o_O

That was my first thought when I originally saw it on the news - way too big for a regular chemical explosion. I feel bad for the firefighters that were killed even though there are reports that their response may have triggered the explosions. Given the sequence of explosions and the reports of water used on unknown chemicals, it wouldn't be surprising. Unfortunately China will cover up the details to the point of it being nothing more than a small fireworks display.
http://www.reuters.com/article/2015/08/14/us-china-blast-idUSKCN0QH2B220150814
 
  • #13
Bystander said:
Accidental FAE?

Borg said:
http://www.reuters.com/article/2015/08/14/us-china-blast-idUSKCN0QH2B220150814

Chemical safety experts said calcium carbide reacts with water to create acetylene, a highly explosive gas.

Well, there's a possible Fuel+Air combination...
 
  • #14
berkeman said:
Well, there's a possible Fuel+Air combination...
Got out my old Emergency Response Guidebook (1990 - really out of date). I had a very old post-it note on the first page that listed Calcium Carbide, Vinyl Cloride and Hydro Floride. I'm guessing that I wanted to know right away about the worst things that I might run into. :olduhh:

The current ERG response guide for Calcium Carbide is Guide 138 Substances - Water-Reactive (Emitting Flammable Gases).
EMERGENCY RESPONSE
FIRE
• DO NOT USE WATER OR FOAM.
Small Fire
• Dry chemical, soda ash, lime or sand.
Large Fire
• DRY sand, dry chemical, soda ash or lime or withdraw from area and let fire burn.
• Move containers from fire area if you can do it without risk.
Fire Involving Metals or Powders (Aluminum, Lithium, Magnesium, etc.)
• Use dry chemical, DRY sand, sodium chloride powder, graphite powder or Met-L-X® powder; in addition,
for Lithium you may use Lith-X® powder or copper powder.
Also, see GUIDE 170.
Fire involving Tanks or Car/Trailer Loads
• Fight fire from maximum distance or use unmanned hose holders or monitor nozzles.
• Do not get water inside containers.
• Cool containers with flooding quantities of water until well after fire is out.
• Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank.
• ALWAYS stay away from tanks engulfed in fire.
Firefighters will run into burning buildings when everyone else is trying to get out. But, for some things, the advice is to run like hell.
 
  • #15
https://en.wikipedia.org/wiki/Calcium_carbide "In China, acetylene derived from calcium carbide remains a raw material for the chemical industry, in particular for the production of polyvinyl chloride. Locally produced acetylene is more economical than using imported oil.[11] Production of calcium carbide in China has been increasing. In 2005 output was 8.94 million tons, with the capacity to produce 17 million tons.[12]"
I got to watch a small acetylene generator go up fifty years ago during a flood --- impressive.
 
  • #16
Apparently calcium carbide and ammonium nitrate were stored in the same building.

The warehouse, designed to house dangerous and toxic chemicals, was storing mainly ammonium nitrate, potassium nitrate and calcium carbide at the time, according to police. Xinhua has said several containers in the warehouse caught fire before the explosions.

http://uk.reuters.com/article/2015/08/14/uk-china-blast-idUKKCN0QJ01H20150814
 
  • #17
Apparently, the site was storing more chemicals than allowed.
http://news.yahoo.com/china-blast-zone-evacuated-over-chemical-contamination-fears-071734470.html
China blast zone evacuated over contamination fear; 104 dead
Two Chinese news outlets, including the state-run The Paper, reported that the warehouse was storing 700 tons of sodium cyanide — 70 times more than it should have been holding at one time — and that authorities were rushing to clean it up.

Sodium cyanide is a toxic chemical that can form a flammable gas upon contact with water.
and
The disaster has raised questions about whether dangerous chemicals were being stored too close to residential compounds, and whether firefighters may have triggered the blasts, possibly because they were unaware the warehouse contained chemicals combustible on contact with water. The massive explosions Wednesday happened about 40 minutes after reports of a fire at the warehouse and after an initial wave of firefighters arrived and, reportedly, doused some of the area with water.
Storing oxidizers like nitrates and fuel like metal carbides (if potentially in contact with water) is a big No-No.

Local officials also have been hard-pressed to explain why authorities permitted hazardous goods warehouses so close to residential complexes and critical infrastructure, clearly in violation of the Chinese rule that hazmat storage should be 1,000 meters (yards) away from homes and public structures.
Somebodies were looking the other way, while somebodies were violating the law (or was it a rule or guideline?).

It reminds me of the detonation of ammonium nitrate on a ship docked near Texas City in 1947.
http://www.texascity-library.org/disaster/first.php
https://en.wikipedia.org/wiki/Texas_City_disaster
 
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  • #18
This photo of a new car lot gives some idea of the blast effect. Every single vehicle identically destroyed with all glass windows blow out(in?), tires burned off, up to ~1/2 mile away.

aftermath-of-the-explosion-in-a-chinese-port-city.jpg


See the similarities between vehicles nearby the Texas City 1947 amonium nitrate explosion (hat tip Astronuc)

1280px-Txcitydisasterparkinglot.jpg
 
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  • #19
mheslep said:
See the similarities between vehicles nearby the Texas City 1947 amonium nitrate explosion
I thought the same thing when I saw the pictures of the cars in Texas City and the lot of cars in Tianjin.

I suspect some heads will roll.
 
  • #20
Astronuc said:
I thought the same thing when I saw the pictures of the cars in Texas City and the lot of cars in Tianjin.

I suspect some heads will roll.

They must have a large head count by now.
http://content.time.com/time/world/article/0,8599,2007319,00.html
From 2010:
A massive explosion in a southern Chinese city is only the latest in a series of industrial accidents that have hit China in recent weeks. While the country's economic boom has always been dogged by environmental and safety hazards, the frequency of disasters this summer has raised new questions about whether the country can maintain its pace of expansion without doing catastrophic harm to its people and the environment. "These accidents are happening all over China, and the scale ... has become larger and larger," says Wen Bo, a senior fellow with the San Francisco–based NGO Pacific Environment. "You see something you have never seen before, and then you see it again on a larger and larger scale."
 
  • #21
I would imagine that it would be impossible to hide this disaster from the Chinese public.

I don't know which is worse - no regulation or regulation that is ignored. The latter would certainly give the uniformed a false sense of security.

There is a lot to be said for regulation for safety and health reasons.
 
  • #22
Astronuc said:
There is a lot to be said for regulation for safety and health reasons.

There is and I really feel for the brave who went into this hell knowing they would not likely return or be badly hurt.

Don't know if this is a valid or WAG calculation but the effects seem to be a lot more than the 'official' 21 T TNT equivalent.
 
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  • #23
I was think that the couple of big explosions might have been on the order of a kiloton. They are certainly much larger than 21 T equivalent of TNT.
 
  • #25
  • #26
nsaspook said:
a lot more than the 'official' 21 T TNT ]
Yes, I suspect that to be proportional to the ground shock wave only where the impulse is milliseconds long. The energy of this explosion however is released over a couple full seconds.
 
  • #27
mheslep said:
Yes, I suspect that to be proportional to the ground shock wave only where the impulse is milliseconds long. The energy of this explosion however is released over a couple full seconds.

I'm pretty sure that's right.
This clip shows one explosion at slow speed fairly close. It looks like the ground wave is tossing objects up before the air wave hits them.
It moves from a intense fire to an initiation burst small shockwave to a massive shockwave then to an heaving explosion that lasts a long time.
http://i.imgur.com/ruY55kK.gifv
 
  • #28
No crater.
 
  • #29
Bystander said:
No crater.
1439640723_10002721+China+Port+Explosion+361260431.JPG

Haven't seen ground zero yet? I think those are cargo containers.
http://www.startribune.com/china-blast-zone-evacuated-over-chemical-contamination-fears/321947021/
 
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  • #30
150815-world-china-aerial-hole-340a_a1f5e28f7b90731e482ee8a79674fedd_nbcnews-ux-600-480.jpg

50-75 meters; 10-12 tons; stet.
 
  • #31
Authorities pulled more bodies from a massive blast site in the Chinese port of Tianjin, pushing the death toll to 112 on Sunday as teams scrambled to clear dangerous chemical contamination.
...
Two state-run Chinese news outlets, The Paper and the Southern Metropolis, reported that the warehouse was storing 700 tons of sodium cyanide - 70 times more than it should have been holding at one time, and that authorities were rushing to clean it up.
http://www.nzherald.co.nz/world/news/article.cfm?c_id=2&objectid=11498139
 
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  • #33
Astronuc said:
I would imagine that it would be impossible to hide this disaster from the Chinese public.

I don't know which is worse - no regulation or regulation that is ignored. The latter would certainly give the uniformed a false sense of security.
There is no, but NO contest; regulation that is ignored is a disaster waiting to happen, and the disaster includes rendering other regulations impotent through contempt.
Almost as bad are regulations that are unpractical or not understood.
 
  • #34
I didn't know about the NH4NO3; I had been badly surprised by alleged estimates of explosions of the order of 21 tonnes of TNT equivalent. That made me sceptical of blebe, gas, & similar explanations, because to assemble enough fuel for that scale of explosion and then to detonate it efficiently is NOT EASY, no matter what the amateurs might think. But Ammonium nitrate might easily be present in hundreds of tonnes quantities, and only a modest efficiency of detonation from the first blast might well have caused the rest.

Now we are hearing about 100 tonne quantities of NaCN as well (though the newscasts ore talking a lot of rot about it). If there really is that much of it there, it just HAS to cause problems; cleaning up that much cannot be a clean matter, and the stuff really is dangerous. 100 tonnes is just about enough to kill every human on Earth, properly administered.

If the figures on the news are to be believed, the death toll so far is minute!
 
  • #35
nsaspook said:
Don't know if this is a valid or WAG calculation but the effects seem to be a lot more than the 'official' 21 T TNT equivalent.
Nice work by Thunderfoot in the video: 300 tons TNT from fireball size, 150 m diameter estimate. He's a working British chemist.
 
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