Sciencemadness Discussion Board - Eutectic nitrate/fuel mixtures

Eutectic nitrate/fuel mixtures

deltaH - 28-9-2015 at 11:58

US 7,588,694 B1 refers (1).

In this patent, there's a table that summarises the various nitrate eutectics.

Excluding lithium and silver nitrate-based ones as 'exotic', the most interesting one is the 21:49:30 Ca-Na-K-NO3 one with a liquidus temperature of 133°C! These are low cost and easily available nitrates.

Now 133°C also happens to be urea's melting point...

So I was wondering if this couldn't be an interesting way to formulate highly insensitive commercial explosives by melting 21:49:30 Ca-Na-K-NO3 together with an amount of urea as fuel.

Now I know urea is a poor fuel, but the way I see it, it's a low-cost solid ammonia with a low carbon content and as such might be beneficial for producing less explosive fumes and so possibly advantageous to mining applications.

Oh forgot to mention the way I envision this being made is to have the molten drops of urea and nitrate eutectic dripped/spun into a non-polar solvent (e.g. hexane/pet. ether?). None of those components would be soluble in an oil and so you would shock freeze the melt into beads. This shock freezing might help make the beads more easy to detonate, though probably still extremely insensitive?

Anyway, just a crazy idea, have fun with it...

References:

(1) https://www.google.co.za/patents/US7588694?dq=eutectic+silve...

[Edited on 29-9-2015 by deltaH]

roXefeller - 28-9-2015 at 12:58

I like the way you think. The lamellae structure of eutectic would be an intimate mixture. But I would think it is possible that the urea could throw off the eutectic point of the mixture, maybe to the point of necessitating changes in nitrate proportions. It would be interesting nonetheless.

deltaH - 28-9-2015 at 13:08

Thanks roX. Urea is a good hydrogen bond donor, so it can form deep eutectic solvents with certain ions, for example with choline chloride, but the nitrate ion isn't a strong hydrogen bond acceptor AFAIK, so I would expect the liquidus temperature of the mixture to not be affected very much by its presence. If anything, it might be slightly lower.

If anyone is wondering how the calcium nitrate is dehydrated and too lazy to read the patent, it's simply used as the tetrahydrate and the melt formed, then the temperature is held hot so that the water is boiled off until it becomes anhydrous and voila! I thought that's pretty neat!

[Edited on 29-9-2015 by deltaH]

deltaH - 3-10-2015 at 06:37

Coming back to the notion of a mining explosive that produces less explosive fumes, urea as a fuel is going to produce CO2 upon combustion.

Now I have a question, if you have calcium/sodium/potassium nitrates in the explosive composition, would these form calcium/sodium/potassium carbonate after detonation (assuming there enough carbon dioxide in the balance)?

Bot0nist - 3-10-2015 at 17:10

Even after intimately mixed as a liquid, would a mixture employing such insensitive nitrate salts and fuel even be able to be initiated and detonable, without a huge booster, and/or massive quantities/critical mass?

I know of ammonium nitrate being used in blasting mixes, as well as chlorates and perchlorates, but can Na, Ca, and K nitrates sustain a detonation front in reasonable quantities and conditions? I do not know of this. Or do you think the eutectic mix of the three will make a dramatic diffrence?

kecskesajt - 3-10-2015 at 21:01

Maybe add some AN so you will have nitroguadine in your mixture so it will be more sensitive.

deltaH - 3-10-2015 at 22:41

Your idea of creating nitroguanidine in situ is a nice one!

I was indeed hoping that a very fine microstructure would make it detonatable. kecskesajt, on sensitisation, there are eutectic formulations with AN, but the one in that table is with LiNO3 and that's useless due to cost.

Coming back to formulating for low fume. Nobody answered my question yet about the fate of CO2 in the presence of alkali metals, so I will assume you make carbonate for now. That said, making calcium carbonate is a nice way to sink CO2 and is a benign product. However, the alkali metals are not, namely sodium and potassium carbonate. In mining applications, having those around is not benign as they are pretty basic.

So one idea is to formulate in such a way as to sink ALL CO2 as calcium carbonate, then you will too much oxygen in the balance, so one can then formulate with aluminium powder to sink the remaining excess oxygen and increase the power of the explosive.

Now that you are making aluminium oxide and have alkali around, you can sink the alkali metals as feldspars, these are benign soil constituent minerals. The only problem is that you would need silica there as well to make a feldspar. I don't think adding just sand would work, you probably need to add the silica in a more active form, such as a water glass. You ideally need it to dissolve into the melt so that it's available.

So far, the composition is looking like a mix of:

urea
AN (with conditions such to make NG in the melt)
NaNO3
KNO3
CaNO3
Al
Na(x)SiO3

Would be nice to have the silicon present as powdered silicon, but that would be too expensive I would imagine.

Perhaps another low cost HE could be added as a sensitizer, although it would need to be added to that melt and be safe to do so, though it would make a low cost explosive much more costly, I would imagine.

[Edited on 4-10-2015 by deltaH]

Fulmen - 4-10-2015 at 00:34

This thread has a lot of info on eutectics, including nitrates:
http://www.sciencemadness.org/talk/viewthread.php?tid=63002

deltaH - 4-10-2015 at 03:42

Thanks Fulmen, exactly what I was looking for, some additional NH4NO3 recipes!

This one looks really good: Ca/NH4 29/71 111°C

There's also a sodium version and a potassium version, but it might not be necessary. As nitrates go, calcium nitrate is the cheapest nitrate commercially available AFAIK.

**********
Ok, working with that Ca/NH4 eutectic, I calculated a basic oxygen balanced formulation on a mass basis of anhydrous ingredients of:

Calcium nitrate: 21%
Ammonium nitrate: 52%
Urea: 26%

This would make a lot more CO2 than what the calcium nitrate could sink though, but it might be a nice place to start to see if such prills are even detonatable.

[Edited on 4-10-2015 by deltaH]

PHILOU Zrealone - 15-10-2015 at 10:05

Quote: Originally posted by deltaH

Oh forgot to mention the way I envision this being made is to have the molten drops of urea and nitrate eutectic dripped/spun into a non-polar solvent (e.g. hexane/pet. ether?). None of those components would be soluble in an oil and so you would shock freeze the melt into beads. This shock freezing might help make the beads more easy to detonate, though probably still extremely insensitive?

Just an info for you urea may have a good affinity for short linear alcanic chains.

I have read in one of my old books that it may be used to complexate pentane, hexane and heptane and selectively separate those form other alcanes in a mix.

This fact was never tested by me, but the info is so weird to my understanding that it is engraved into my memory

BTW nice idea.
To boost thing up...adding hydrazine nitrate to the mix

[Edited on 15-10-2015 by PHILOU Zrealone]

PHILOU Zrealone - 16-10-2015 at 10:07

Quote: Originally posted by aga

No. I don't understand this at all, and will not test it out.

Needs someone with some EM experience.

Any takers ?

Aga,
I don't get it.
To what reply is it linked?
To mine?

deltaH - 16-10-2015 at 10:34

Quote: Originally posted by PHILOU Zrealone

Quote: Originally posted by deltaH

BTW nice idea.
To boost thing up...adding hydrazine nitrate to the mix

[Edited on 15-10-2015 by PHILOU Zrealone]

I would have never guessed! Wow

aga - 16-10-2015 at 11:33

Quote: Originally posted by PHILOU Zrealone

Aga,
I don't get it.
To what reply is it linked?
To mine?

It appears that the post i was replying to has been deleted.

I deleted mine as it is now non-sensical.

Please delete yours that quotes mine, then i'll delete this one and the thread will be returned to sanity.

[Edited on 16-10-2015 by aga]

PHILOU Zrealone - 17-10-2015 at 11:10

Quote: Originally posted by aga

Quote: Originally posted by PHILOU Zrealone

Aga,
I don't get it.
To what reply is it linked?
To mine?

Sorry, working in night shift and came too late here to be able to delete mine

aga - 17-10-2015 at 13:15

Heigh ho. We tried at least to restore sanity.