Sciencemadness Discussion Board

Detonation properties of moist AN

dangerous amateur - 19-3-2013 at 04:36

Hi,

when I do experiments with AN I allways make sure my AN is absolutely dry.

However, how do the detonation properties of AN change with added water?

Imagine you are in mining, or a taliban fighter, burying your 50 pound sacks in a road - it must be impossible to keep the stuff allways dry.

It does not seem to be a great problem.

Are there any experiences or performance figures out there for wet AN?

Ral123 - 19-3-2013 at 05:02

Powerful booster and big diameter and confinement will solve it. Al will also.

simply RED - 19-3-2013 at 05:30

You put it in 10 liters plastic water bottles with duct tape on the screw. It keeps dry forever!

dangerous amateur - 19-3-2013 at 08:49
Quote:

You put it in 10 liters plastic water bottles with duct tape on the screw. It keeps dry forever!

I know. But often one cannot ensure this kind of storage.


Is there some kind of information how much the critical diameter and detonation velocity of typical ammonal or annm mixtures varys with water content?

Trotsky - 19-3-2013 at 09:06

Look at Tovex, for instance. Or any of the other water gels.

I have seen a paper on the properties of wet TATP/AN combinations that found it to be an effective, but not particularly powerful explosive.

VladimirLem - 19-3-2013 at 09:07

Threadstarter, im sorry to say that, but you are a retard :P


with some plasticbags i even made unterwater-explosions with ammoniumnitrate-based explosives...SO, wheres the problem?:cool:

>Taliban
>using AN-based explosives to blow up armoured vehicles
my sides :D

...aaaand, there are even AN-based explosives containing water, to make it to some kind of gelantine/liquid explosive - but must be damn hard to ignite:o

Ral123 - 19-3-2013 at 11:57

AP with ammonium nitrate slolution:
http://www.youtube.com/watch?v=HOoU9aeD_BM
AP(control sample)
http://www.youtube.com/watch?v=f-HtfnjKKhE

dangerous amateur - 25-3-2013 at 14:11

I hoped to get some serious answers and no kewl AP shit.

I know about those water gels, but they mostly contain additional sensitizers. Mostly special stuff that amateurs hardly can reproduct.

Basically I want to know how critical diameter and brisance are affected with typical annm or ammonal mixtures, in say 50 or 100g charges.

Or in other words, is it worth the hassle to allways use absolutely dry AN. How much does one sacrifice if it isn't?


Ral123 - 25-3-2013 at 14:39

AP is neither k3lw or shit. People who abuse explosives(may be you) are.

Trotsky - 25-3-2013 at 21:49

No, it's incredibly powerful and very brisant. The fact that it's easy to make doesn't make it 'k3wl-' that may describe those who make it, not the compound itself.

APAN solution may be the safest way to use it.

Ral123 - 25-3-2013 at 23:57

I guess he meant AP is sh*t and some other elite energetics are "how it's done", witch is logic of a k3wl not a scientific interest.

Fantasma4500 - 26-3-2013 at 07:42

Quote: Originally posted by VladimirLem  
Threadstarter, im sorry to say that, but you are a retard :P


with some plasticbags i even made unterwater-explosions with ammoniumnitrate-based explosives...SO, wheres the problem?:cool:

>Taliban
>using AN-based explosives to blow up armoured vehicles
my sides :D

...aaaand, there are even AN-based explosives containing water, to make it to some kind of gelantine/liquid explosive - but must be damn hard to ignite:o


your roadsides? ;) couldnt resist..
anyhow during the vietnam war they used daisy cutters, AN/Al with 5% of water.. im shocked myself that adding water to AN will work by any means...?? since they kept using it i guess it didnt completely fail.. also pretty huge stuff.. not just a few kg at a time

VladimirLem - 26-3-2013 at 09:40

Quote: Originally posted by dangerous amateur  

Basically I want to know how critical diameter and brisance are affected with typical annm or ammonal mixtures, in say 50 or 100g charges.

Or in other words, is it worth the hassle to allways use absolutely dry AN. How much does one sacrifice if it isn't?


im pretty sure that ANNM with up to 8 percent H2O would work well with a strong detonator...at Ammonal, i would go only for really dry AN, its much harder to ignite
dry AN(NM) is able to ignite with only 0.5 gram of HMTD:cool:

critical diameter...pew...really hard to say...but if you dont go for a shaped charge or other stuff like that, it absolutly doesnt matter...

and i don't get where the problem is, its simple as f*ck to get AN dry...just takes some time...;)

Hennig Brand - 26-3-2013 at 16:12

Anfo heat of detonation 3890 kJ/kg.
Water heat of vaporization 2260 kJ/kG at 100 Celcius (will be less at higher temperatures and pressures, but still high)

It is easy to see that even small amounts of water can suck a lot of energy out of the explosion.

I try to dry AN well before use. Compositions using dry AN are much easier to initiate and the power of the explosion can be much higher. The AN I use is in prilled form and is usually quite damp before being "processed".

dangerous amateur - 27-3-2013 at 11:36

@Hennig Brand:
A very interesting point. Thank you for your answer.
Quote:

and i don't get where the problem is, its simple as f*ck to get AN dry...just takes some time...;)


Yes, I agree.
But sometimes you finish your charge and then have to wait some time until the coast is clear or something like that.

Hennig Brand - 28-3-2013 at 12:47

Thanks, but actually I was wrong in a way. Since detonation is an almost instantaneous process the energy does not dissipate or is not lost to the surroundings in the way that I suggested. The energy, that I said was lost (sucked out), is still present in the water vapor. What I should have said and what does happen is that the energy that is used to vaporize the water is not there to raise the temperature and expand the gaseous products of the detonation. Converting water to water vapor is an isothermal process meaning that the temperature does not change, but a huge amount of energy is absorbed in order to force the water to go through the phase change from water to steam.


The more I think about this I am not really sure of myself. Water may actually be involved in the explosive chemical reaction depending on the composition. I think I have heard of aluminized explosives that may actually use water as an oxidizer but I am not sure. Water may contribute to the explosive reaction in various ways depending on the composition.

One thing I know for sure, ammonium nitrate explosives tend to be very insensitive and even small amounts of water present can greatly increase this insensitivity.

Edit:

Ok, so I did a few calculations.

From saturated steam tables (properties of water)
@100C
Volume liquid = 0.001044 m^3/kg
Volume vapor = 1.6729 m^3/kg
Heat of vaporization = 2257 kJ/kg

So by adding 2257 kJ to a kg of water at 100C we can increase its volume by 1.6729/0.001044 = 1602 times. Still no increase in temperature, but we sure made a lot of gas.

Every explosive has different proportions of gaseous products. I took air as an example.
Find average heat capacity between room temperature and upper temperature. I used the heat capacity of air at room temperature to determine approximate upper temperature value. Heat capacity of air at room temperature is 1.005 kJ/kg*K.

I hope you are impressed because it took me a while to figure out how to do this again. Using my thermodynamics book and the constants for air I did the integral and determined the average heat capacity value for air between 20C (293K) and 1727C (2000K) which was the upper limit of the method I used. The calculated average heat capacity was 1.16 kJ/kg*K

So, for 1kg of air the new temperature is approximately:
T = 2257kJ / (1.16 kJ/kg*K) = 1946 K (1673C)

Ok, assuming constant pressure and using the ideal gas law which is not exactly accurate but gives us an approximation. (PV = nRT)
V1 / T1 = V2 / T2 since P, n and R are constants.
Volume at room temperature = V1 = 1kg / (1.205kg/m^3)
V1 = 0.8299m^3
T1 = 293K (20C)
T2 = 1946K
Therefore V2 = 5.51 m^3

Volume increase for air = 5.51/0.8299 = 6.64 times vs. 1602 times for water with the input of the same amount of energy.

Water is starting to look pretty good compared to air (or other gases). Maybe some water in an explosive isn’t such a bad thing. High explosives can however produce that volume of gas, or even more, and heap loads of energy to go with it. Water makes a huge volume of gas, but absorbs a lot of energy in the process. I also don't think that water could absorb energy as fast as a high explosive could produce it, even when evenly dispersed throughout the explosive. Heat transfer takes time, even with tiny amounts of water surrounding each explosive particle. This may seem like a small point, but detonations are measured in micro seconds.



[Edited on 29-3-2013 by Hennig Brand]

AJKOER - 3-4-2013 at 13:48



I would consider adding Magnesium powder to the wet NH4NO3, as per Wikipedia (link: http://en.wikipedia.org/wiki/Magnesium ):

"Like its lower periodic table group neighbor calcium, magnesium reacts with water at room temperature, though it reacts much more slowly than calcium. When submerged in water, hydrogen bubbles almost unnoticeably begin to form on the surface of the metal—though if powdered, it reacts much more rapidly. The reaction occurs faster with higher temperatures (see precautions)"

This is why Mg can burn under water. Note, however, this could create a storage issue as the wet explosive could form a pressure condition as H2 is generated.

So, adding Mg to a so called watered down explosive containing Mg powder could, upon ignition, theoretically be able to draw on the oxygen from the water within the explosive itself, and possibly any water vapor in the surrounding atmosphere. Reactions:

Mg + H2O → MgO (s) + H2 (g)
3 Mg + N2 → Mg3N2

Wikipedia notes for dry Magnesium:

"Once ignited, it is difficult to extinguish, being able to burn in nitrogen (forming magnesium nitride), carbon dioxide (forming magnesium oxide and carbon) and water (forming magnesium oxide and hydrogen). This property was used in incendiary weapons used in the firebombing of cities in World War II, the only practical civil defense being to smother a burning flare under dry sand to exclude the atmosphere. "

Also, to a lesser extent, I would guess even ammonia from the reaction of humid air and Magnesium nitride:

Mg3N2 (s) + 6 H2O (l) → 3 Mg(OH)2 (s) + 2 NH3 (g)

So with the formation of Hydrogen, and possibly even some Ammonia in rain or high humidity conditions, there could further be a small thermobaric aspect. That is, the wet Mg explosive would be relying on oxygen from the surrounding air to detonate any formed Hydrogen (and/or Ammonia). This could precipitate an additional blast wave effect, usually of significantly longer duration, than with classical condensed explosives.

And further (yes, it get even more deadly), per Wiki:

"Flame temperatures of magnesium and magnesium alloys can reach 3,100 °C (3,370 K; 5,610 °F)".

So, there is historical basis to add Magnesium being a proven incendiary, its ability to react with water forming Hydrogen (potentially also some Ammonia from Magnesium nitride), which may interestingly even add a thermobaric aspect/punch.

Personally, I would like to witness from a distance, but be able to feel the blast wave and noise level, of three comparative explosions. One with dry Mg/NH4NO3, another with Mg/Wet NH4NO3, and the last Mg/Wet NH4NO3 again, but this time in the rain/high humidity conditions.


[Edited on 3-4-2013 by AJKOER]

Trotsky - 3-4-2013 at 23:48

@Hennig Brand: Water has one of, if not the largest liquid:gas volume changes. There's a reason it worked so spectacularly for steam engines and we didn't switch to methanol engines.

Oh well, it's cheap and available everywhere. That might have been relevant in the choice :)