Why shouldn't you pour slag into water

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samuel-a

Well-known member
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Oct 7, 2009
Messages
2,190
It is common knowledge in our profession. And i have experienced it once or twice, but never seen it that clearly and in slow motion.
Stay safe.

[youtube]http://www.youtube.com/watch?v=DuxXm7Y87do[/youtube]
 
Holy friggin bat snot!!! :shock: That's an impressive clip. Now, is that just purely a steam explosion, or are there other mechanics at play? It kind of looked like the slag itself exploded.

I bet it was fun cleaning up all that glass, and whatever filled his under shorts. :oops:
 
I grew up in a city with a steel mill on the shore of Lake Erie. They loaded the slag onto tilting train cars, drove them out to an area high above a steep bank over a large water pond, and dumped them into the water. It was always an impressive sight as the red hot slag hit the water and sent up a huge glowing steam cloud that looked like a volcano exploding. The resulting material, known as popcorn slag, was sold as an aggregate used to make concrete.

I haven't thought about that for many years.

Dave
 
Sometimes you want to pour slag into water, like the AgCl slag from the Miller process :p
 
FrugalRefiner said:
I grew up in a city with a steel mill on the shore of Lake Erie. They loaded the slag onto tilting train cars, drove them out to an area high above a steep bank over a large water pond, and dumped them into the water. It was always an impressive sight as the red hot slag hit the water and sent up a huge glowing steam cloud that looked like a volcano exploding. The resulting material, known as popcorn slag, was sold as an aggregate used to make concrete.

I haven't thought about that for many years.

Dave

My hometown had an operating steel mill until my late teens early twenties. They dumped the slag onto the ground and it would light up the sky at night and i always enjoyed watching it. You could follow the glow above the pot haulers as the left the melt shop all the way to the slag plant which was about 2 miles away. Some nights there would be residual water on the ground that had not yet steamed off and when the pot was poured this would cause a massive explosion that would shake the ground for miles as it sent molten slag hundreds of feet into the air. I lived less than a mile away from the slag plant so i had a birds eye view of this almost daily. The slag plant sat atop a small hill, maybe 50 feet above the street i lived on, with mounds of slag blocking my view of the actual pouring. But with every explosion the slag sent into the air looked like a volcano erupting. Fast forward 20 years and i'm there as part of an "EPA superfund cleanup effort". The amount of steel poured onto the ground and covered up gives a bit of insight as to why the mill had to close its doors. Several hundred thousand tons of steel was recover over a 3 year period, and there is more still in the ground because according to the EPA, "it is not worth the effort to recover". I should stop here before i get into the politics of it all. I sure wish that plant were still up and running....
 
UncleBenBen said:
Holy friggin bat snot!!! :shock: That's an impressive clip. Now, is that just purely a steam explosion, or are there other mechanics at play? It kind of looked like the slag itself exploded.

I bet it was fun cleaning up all that glass, and whatever filled his under shorts. :oops:
It's too fast to be a steam explosion, there is no pressurized vessel and to transfer so much heat to the water is impossible. I would say it's most probably the molten salt that is exploding and that it reminds me of Prince Rupert's drop where internal stresses create an explosion when the surface is damaged in one place.
[youtube]http://www.youtube.com/watch?v=xe-f4gokRBs[/youtube]

Göran
 
I don't know if it is true, but in the fire brigade education for leaders they told, that water will decompose to H2 and O2 if only the temperature is high enough and then the gasses will explode by reacting with each other again. The reason I think of that is, that the explosion looks quite as violent as an oxyhydrogen explosion when you watch the video by stopping step for step. I do not believe it is the slag alone that explodes, since it is jacketed in a gas bubble that is open at the top.
 
Very interesting. You can see a hint of a reddish cloud shoot out the top of the explosion from the slag shattering into tiny pieces much like the Prince Rupert's video.

Yet it appeared that the blast started when the water at the surface had just closed over the top of the slag, forming a bubble of super hot vapor.

Whatever mechanisms are involved, it sure is fun to watch!
 
When pouring a melt from a gas crucible furnace, it is common practice to place the mold(s) on a large sheet of 1/4" steel, to prevent any molten slag from coming in contact with the concrete floor. Untreated concrete can soak up a lot of moisture and, when molten slag hits it, an explosion can occur.
 
goldsilverpro said:
When pouring a melt from a gas crucible furnace, it is common practice to place the mold(s) on a large sheet of 1/4" steel, to prevent any molten slag from coming in contact with the concrete floor. Untreated concrete can soak up a lot of moisture and, when molten slag hits it, an explosion can occur.

I use a sandtrap, works great and not risk of splattering as the sand takes the over spill and soaks it up.

Scott
 
solar_plasma said:
I don't know if it is true, but in the fire brigade education for leaders they told, that water will decompose to H2 and O2 if only the temperature is high enough and then the gasses will explode by reacting with each other again. The reason I think of that is, that the explosion looks quite as violent as an oxyhydrogen explosion when you watch the video by stopping step for step. I do not believe it is the slag alone that explodes, since it is jacketed in a gas bubble that is open at the top.
Can't be true, it would be a chemical perpetuum mobile.

Hot water -> turns into oxygen and hydrogen -> burns -> even hotter water -> and so on...

If the temperature is high enough to break up water in gases, then it does so because the chemical equilibrium is pushed towards gases at higher temperatures, and then it wouldn't burn because that would be against the equilibrium.

To keep a steam bubble under the surface, you need to constantly create steam, the source is the heat of the slag so the surface cools down quite fast. That creates a surface that's contracting around a hot center. When the tension increases enough, the surface suddenly ruptures and most of the tension is released by something that looks like an explosion.

Göran
 
Thanks, Göran, you are right - I wouldn't have expected anything else :lol:

https://en.wikipedia.org/wiki/Water_splitting#Thermal_decomposition_of_water

This slag doesn't have 2000-3000°C to even make the decomposition possible. After I read your explanation I doubt this effect would have any considerable influence on fire fighting either, other than that the product gasses (H, H2, O, O2, and OH) will have about double as much volume as H2O vapor alone.
 
Thanks for the link Björn, I had no idea when thermal break down of water occurred. That it did I was sure about as taking it to the extreme point would be a plasma where every atom is ionized.

About the exploding salt / slag, a simple analog would be to think on it as a strong spring and a vice. The center is a spring compressed by a shrinking outer shell represented by the vice. As the surface is cooled much faster than the center it compresses the spring. If you compress a strong spring with a vice and the vice suddenly breaks, all force stored in the spring is released in an instance.

Göran
 
Nice analog! I will use the videos and your analog in future, when I have to teach kinetic and potential energy to the kids 8)
 
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