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View Full Version : AN and Propane?


blythenator
August 6th, 2007, 12:24 AM
Hello all, yesterday I was reading a forum that contained the following text.


"My uncle used an interesting method to detonate ammonium nitrate for making farm ponds. He would fill a 10lb propane tank with unmodified prills, tap in a spark plug (sealing with superglue), and overpressurize the tank with 2/1 air/propane until just before the relief valve popped. He then let the tank sit 24 hours to mix.

The tank's propane was ignited with an ordinary ignition coil wired to the sparkplug as per usual. Detonation was achieved from the heat of combustion in the air gaps between the prills."

Does this sound like it may work? I know you have to detonate with super sonic primer/booster to start the reaction, but what about the cargo containers that detonated due to fire?

Has anyone ever done this before? I would love to give it a try but I have to drive atleast 1-2 hours to be safe.

Jacks Complete
August 6th, 2007, 07:16 PM
I think an aggressive, explosive mix of something like acetylene, combined with the containment of the tank should do it. As long as the mix is contained and mixed enough to detonate, ANFO should go.

The mix you describe would be fine for the gas to air mix (perhaps a bit lean) but is going to be very very lean for the AN prills.

209
August 6th, 2007, 10:11 PM
I personally have cut open a propane tank to use for an aluminum melting foundry. I basically tore off the valve with a pipe wrench nearly a big as me and then filled the tank with water then let it sit for several days. I then sparked up my torch and cut the top of that would later serve as a lid.

If he did indeed fill the tank full of AN with risidual amounts of propane left, I would think that to be very dangerous, being that there is still enough propane to detonate the AN. The are far better and safer methods of detonating AN.

Rbick
August 9th, 2007, 12:23 PM
It sounds like it would work, although with that much AN it might be a little over oxidized, but if it works, it works. The proper Propane to AN ratio would be 5% Propane to 95% AN for full oxidation. The Propane doesn't exactly detonate the AN, the AN would donate its free Oxygen to the Propane, which has the chemical formula C3H8.

The decomposition of AN is

NH4NO3 ---> 2H2O + N2 + 1/2O2

That 1/2O2 is what is donated to the unoxidized component. With the introduction of oxygen and heat, propane decomposes to 3CO2 and 4H2O. This is the reaction you see when you light a camp stove. The heat from the lighter causes the Oxygen in the air to oxidize the Propane, starting an exothermic reaction. If there is a strong oxidizer, such as AN, the propane will oxidize much faster, resulting in a detonation.

Under STP, propane is obviously a gas. My guess is that when the guy pumped the propane back into the tank containing the AN, it was under enough pressure to become a liquid. As a result, you would have a mixture similar to ANFO. Even if the propane was still in gas form, it would be oxidized non-the-less by the AN in the tank. So there isn't really anything special about this explosion other than the ignition. I'm not sure how that works... Propane is explosive when mixed with air in the precentages of 2.37–9.5%. Maybe the spark plug ignites the propane/air mix, which then detonates the AN/Propane mix?

Charles Owlen Picket
August 9th, 2007, 12:42 PM
Propane is explosive when mixed with air in the precentages of 2.37–9.5%. Maybe the spark plug ignites the propane/air mix, which then detonates the AN/Propane mix?

I think you hit the nail on the head. Your point makes sense. However, ambient temperature would have a most basic influence. Realistically, it could also be that the propane exploded and the prills simply flew. If you didn't examine the explosion yourself, you may never really know.

Remember in the OP you stated that the prills were not prepared as an explosive (clay or whatever may still be on their surface) making absorption possibly difficult. There are variables that could only be accounted for if you, yourself observed the phenomenon.