Sciencemadness Discussion Board

Ammmonium nitrate reactor

Theoretic - 26-5-2004 at 11:27

I was just thinking about the thermal decomposition of AN, which provokes a lot of controversy - i.e., about wheter it's safe, how fast it goes at a given temperature, how much harmful byproducts does it produce etc...
But above all controversy, it's exothermic, and pleasingly controllable (well ;)). So I was just thinking if it's possible to make a "reactor" that will self-controllably and self-sustainably decompose AN, in form of a simple vessel that is preheated to start the reaction. It should be self-controlled by the fact that an increase in temperature will prompt a much larger increas in heat escaping as radiation.
Is this technically possible?

Marvin - 27-5-2004 at 12:00

Conduction and radiation are too slow, the system would have a PTC and would be uncontrolable.

Do what everyone else does, mix an alkali nitrate with a stable ammonium salt eg the sulphate (not chloride) in a pyrex flask and heat that with a burner.

Nate235057 - 25-7-2004 at 18:42

I get my AN from ice packs
then I grind it up in my mom's food processor what she doesn't know cant hurt her...

vulture - 26-7-2004 at 06:24

And your point is?

A) You're so tuff because you do stuff your mom doesn't know about?
B) You're trying to look tuff by talking along some useless gibberish?
C) I'm being too generous and you're simply a moron.

[Edited on 26-7-2004 by vulture]

I am a fish - 26-7-2004 at 13:34

Am I right in assuming you want to make N2O? (There are other products, that you may conceivably be aiming for.) If so, have you considered the nitrous acid plus hydroxylamine route? It gives a higher quality product, and is much safer. Both hydroxylamine salts and nitrites are available from photographic suppliers.

What sort of quantities are you planning to use? Something that may be safe for a few grams at a time, could be suicidal for kilos at a time.

Why do you want the reaction to be self sustaining? Yes it will save fuel, but it will also make the process far more dangerous. If the reaction is always dependent on an external heat source, it can be shut down at the flick of a switch. Of course, designing a reactor that always dissipates more heat than can be generated by the reagents, is easier said than done.
Quote:
Originally posted by Nate235057
I get my AN from ice packs
then I grind it up in my mom's food processor what she doesn't know cant hurt her...


From your first four posts to the forum, it is clear that:

1. You are lazy and rude. Didn't it even occur to you to type "Silver Fulminate" into the search engine, before starting a new thread about it?
2. You don't know the first thing about chemistry or pyrotechnics. If you had taken the trouble to learn about oxygen balance, you could have easily answered your own question about blackpowder and aluminium.
3. You are eager to boast, despite having very little to boast about. This thread is about the decomposition of ammonium nitrate, not obtaining it.

vulture - 26-7-2004 at 14:05

If you really want a large, self sustaining reactor the melting salt method might be nice for temperature control.

The reactor body is lined with a salt that melts when the critical temperature is reached, absorbing heat by it's melting enthalpy.

Problems:

- Finding the critical temperature and the corresponding salt/substance
- The required substance might be expensive or exotic.
- The required substance has a low heat capacity or low melting enthalpy.

Simple option is a thermostat which opens a shower to flush the outside of the reactor vessel with water.

BTW, which material would the reactor be made of? Ammonium nitrate is pretty corrosive to metals, certainly when hot.

Centimeter - 19-8-2004 at 22:00

I know that we beekeepers will sometimes add some NH4NO3 to the smoker when dealing with a particularly agresive hive. The bees are easily knocked out by the N2O and they show no signs of being poisoned or anything like that. Although I suspect that this would present quite a large danger in a big device.

Dodoman - 20-8-2004 at 15:25

I may be wrong about this so please correct me if i am. Why controle the tempreture.........? :o just build a reactor that would stand the maximum tempreture for a given amount of AN and controle the amount of AN entring the reactor. This could be done manually (this way it won't be self sustaned) or automatically. Now i' not an egineer so i can't suggest a method, but i think it's achievable. Would be something like a gas peddale in the car but when pressed it decreases the rate at which the AN is entring the reactor.

Dodoman - 20-8-2004 at 15:33

As for the thermal decomposition I found this. Strange i haven't seen this post before.

Theoretic - 7-10-2004 at 05:39

"Chloride ions catalyze another decomposition reaction:

5 NH4NO3 ----> 4 N2 + 2 HNO3 + 9 H2O"

Mmm, easy nitric acid! Although dilute and in relatively low yield, but throw in a pinch of salt and you have it! :P Although I suspect it's more complicated than that.
I'm not after N2O, I'm not actually planning to perform the reaction. I'm just wondering if anyone liked the idea of a ceramic/glass pot of AN sitting there and decomposing on its own, without external heat, filling the room with laughing gas. :D The primary question was if the heat dissipation self-control was possible. If not, then another trick could be used: take a rod of a substance that catalytically decomposes AN, and partially submerge it in the melt, withdrawing and submerging to slow/accelerate the reaction (like a nuclear reactor control rod, only in reverse). I'm guessing that it would have to be an iron or copper containing ceramic.

vulture - 7-10-2004 at 07:56

An iron rod would burn up in N2O atmosphere. Quite spectacularly too.

Theoretic - 8-10-2004 at 12:22

No, not an iron or copper METAL containing ceramic! I meant an inclusion of an oxide while sintering your pottery rod. ;) I think zinc silicate would make a good catalyst too, by precipitating it from Na2SiO3 and ZnCl2 and then melting (something tells me it has a relatively low melting point) or sintering. I would assume it wouldn't dissolve in molten AN due to the general chemical unreactivity of silicates, no?