Sciencemadness Discussion Board

Wetting ammonium nitrate

chornedsnorkack - 28-12-2012 at 09:08

Ammonium nitrate has the advantage that unlike saltpetre and all other metal nitrates, it burns without solid residue.

However, its disadvantage shared with all other nitrates save saltpetre is that since it is very soluble, it is hygroscopic.

Ammonium nitrate can explode alone (like Oppau), but its yield is increased by suitable reducer. Ammonium nitrate/fuel oil explosives are popular.

But fuel oil is, well, oil. Wouldn´t fuel oil drain out of ammonium nitrate/fuel oil explosives?

How about a solid reducer? Something which does NOT flow out of the explosive on storage and handling temperatures of 30 and below?

Yet perhaps preferrably not a powder mixed with nitrate (coal, brimstone) - the nitrate would still be free to absorb water.

How much heat can ammonia nitrate take without decomposing and without igniting moderately stable organic substances? Say, under 60 or 70 degrees, mixing ammonia nitrate with a stoichiometric quantity of substances like molten paraffin, beeswax, mutton or beef fat... is it safe?

And how well will molten paraffin or lard wet dry ammonium nitrate powder? Will a stoichiometric amount of molten wax form a complete coating, which after congealing will protect the ammonia nitrate from contact with water in air, or indeed bulk water in contact with the mixture?

hissingnoise - 28-12-2012 at 09:21

AN prills absorb 6-8% fuel oil which is more-or-less the correct fuel/oxidiser ratio.
AN melts @ ~170°C and decomposes when heated further ─ explosively, sometimes . . .

jock88 - 28-12-2012 at 18:13


I believe there are two grades of AN made in the world. One grade for agriculture and another grade for explosives (used by the ton in mining).
The stuff for mining will absorbe fuel oil and keep it absorbed for a sensible period of time.
The agricultural grade is more dense and less absorbing. This is what is wanted as the more useless it is for explosives the better. It can still be made to work.
European countries (and lots of others too I'm sure) mix calcium carbonate with the AN to further stop the stuff being used for explosives. It can still be got to detonate (the AN + CC + Oil) if you use lots of large boosters. The boosters at this stage consist of pipes approx. 2 inches in diameter and a few feet long filled with high explosives (rdx type stuff) ,placed into the mix. The more the better I presume.
The perferred 'oil' in certain places is caster sugar. Don't know why caster sugar is better that oil. Perhaps there is less of a smell. Perhaps the suger workes better with the AN + CC 'non explosive' agricultural grade stuff.

http://www.sciencemadness.org/talk/viewthread.php?tid=22884#...

See ref. 10 for use of sugar.

[Edited on 29-12-2012 by jock88]

AndersHoveland - 4-1-2013 at 10:19

Quote: Originally posted by chornedsnorkack  

How about a solid reducer? Something which does NOT flow out of the explosive on storage?

Wax works good, first heated to a liquid for mixing, then allowed to cool and harden. A member of E+W forums used floor wax, and the resulting mix was called "ANWAX". Wax may not be flammable like fuel oil, but in a detonation this difference does not matter. In fact, ANWAX may be slightly more powerful because wax has a higher density than fuel oil. Other advantages are that the AN does not settle at the bottom during storage, and the wax protects the hygroscopic AN from moisture in the air.

Some commercially popular blasting compositions use AN, ethylene glycol, and gelatinizing agents. This has the advantage that everything is kept well mixed, and it can be stored.

[Edited on 4-1-2013 by AndersHoveland]

badabooom - 9-1-2013 at 00:55

Quote: Originally posted by jock88  

I believe there are two grades of AN made in the world. One grade for agriculture and another grade for explosives (used by the ton in mining).
The stuff for mining will absorbe fuel oil and keep it absorbed for a sensible period of time.
The agricultural grade is more dense and less absorbing. This is what is wanted as the more useless it is for explosives the better. It can still be made to work.


You have a point there, but let me elaborate a little more.

Blasting grade AN is manufactured with micro voids inside the prill. This serves two purposes, 1, it make absorption of fuel oil more efficient due to the porous nature of the prill. 2, it acts in such a way to sensitize the mixture by allowing voids to be created inside the mixture (little bubbles of air) which assist in adiabetic compression. Again there are two froms of blasting grade AN as well, high density AN prills and low density AN prills.

Fertiliser grade AN has solid prills and this due to the mechanism by which it is made. AN gets molten and then sprayed into a cooling tower where the prills form and solidify at during free fall.

Now as for the fuel, it all comes down to energy density. The higher the energy density of the fuel the better it is in the ANFO mixture. Diesel is commonly used as it has a good balance between energy density and cost. It also does not separate out of the mixture. I seen people use ANFO that is more than 15 years old and still the fuel has not separated from the mixture.

Common fuels can be anything that can combust basically, but to list a few; Diesel, motor oil, any sugar, vegi oil, charcoal, aluminium, magnesium, powdered plastics, saw dust, flour, etc. You get the picture. In order to have it work properly you might want to calculate the stichiometric values and oxygen balance fist.

As for safety, well I have seen so many failed attempts at initaiting pure AN, moulten AN and ANFO that I can conclusively say that you are safe from accidental detonation from AN during the melting and mixing process.

I hope this helped.

SM2 - 9-1-2013 at 08:54

It would be academic to dissolve the NH4NO3 in water, as lime is barely soluble. In regards to detonation, I know of no studies of accidental detonations, except for huge quantities. But the dynamics here are quite different. Start with small batches, and my bet is you should be fine. When you are ready to detonate, you really need to whack it w/ a high velocity cap