Preparing KNO3

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jetra2

jetra2

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Alright, this might be a bit past the guidelines, apologies in advance. Mods, please move/delete/discuss, etc.

I have some 99% KNO3 (Potassium Nitrate) in large, granular form. It is used to promote bacteria growth in tree stumps by increasing the amount of nitrogen available to them, thus, facilitating removal. I would like to grind it to a finer powder form for making small smokers and such. Does anyone have any solutions to this problem? I've tried using a pill crusher, but that doesn't get it fine enough and I can only do a gram or two at a time. Are there any mechanical ways that this can be done faster?

Thanks,
Jason
 
coffee grinder... just be sure to only use it for oxidizers (or only KNO3 to be safe)...

I have two, wouldnt want to grind KNO3 and sorbitol in the same grinder...

Really only need it because sorbitol naturally clumps up, and its hard to break it up and get a good mix... But my stuff is plenty fine as is...
 
I have heard of many people doing it with KNO3, and considering the amount you can fit in it I dont see much risk... Just gets risky when you start grinding fuels and oxidizers in the same grinder, traces of the other can be enough to cause problems...

But in order for the oxidizer to cause problems, there would need to be a decent spark...
 
Originally posted by wildbluerocket
Do you think it's safe to put an oxidizer in a coffee grinder?
Click to expand...

Works great, just grind 30 seconds per tablespoon full, and you will have nice powder.

Johnnie
 
Using Jimmy Yawns recrystallized candy technique, you'll never want to grind again.

https://www.jamesyawn.com/

I've used his electric skillet candy to good effect. One of the many plusses with this technique is you can easily pH balance the KNO3 in solution with a little vinegar.
 
Originally posted by wildbluerocket
Do you think it's safe to put an oxidizer in a coffee grinder?
Click to expand...
Johnnie's spot on.

There is no problem grinding oxidizers in a cheap coffee grinder. I do it in 60-80 gram batches. If you start with powder, you have very fine particles in a minute or so. Grind for 10-15 seconds, stop for a second or two and repeat until it's fine enough for you. It rarely takes more than 2 minutes. Wear gloves and a dust mask.

You can also grind plastic pellets and other crystalline materials in a coffee grinder. Since these are fuels, use a different grinder.

Always throughly clean out the grinder completely after you are finished with each type of material. If you think it's clean, it probably isn't. Run it empty for 15 seconds and wipe it out with a damp cloth. Dry it throughly and run it again. You will probably still have some powder comming off. Repeat until you don't get any dust for 3 times in a row.

Never, never, never grind an oxidizer and a fuel together. Bad things are likely to happen... Very Quickly!

Bob
 
Rock tumbler anyone?

Use steel ball bearings with no fuels mixed with the KNO3. You can get a tumbler from Harbor Freight at about $30. Good for other uses that shant be named as well.
 
A ball mill works very well from what I understand and there are some very nice plans on the web. Easy to build, spark proof and easy to clean out. I will be using marbles or ball bearings in mine.
 
These Braun Coffee mils come in white or black and cost between $15-$20 at most stores. They make very fine powders quickly.

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This is a rock tumbler, AKA a ball mill, from Harborfreight. It is typically used to polish rather large items. It takes a really long time to make powders, and do not make them as fine as a coffee mill. It is not considered non-sparking if you use steel balls.

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Wildbluerocket

I am a chemist as well.

To make it crystal clear, I was strictly refering to alkali or alkaline earth metal salt oxidizers such as potassium nitrate only.

Potassium Nitrate is an oxidizer only. It does not burn, and will not burn. It is not flamable and it is not an explosive. It is safe to grind and is essentially only a dust inhalation hazard provided you don't eat it.

On the other hand, ammonium nitrate, ammonium perchlorate, and other ammonium salts that contain oxygen are not only oxidizers, but are also monopropellants as they contain both a fuel component (hydrogen) and an oxidizer (oxygen) in the same molecule. Grinding ammonium salts containing oxygen is hazardous, and AP ground to a particle size below 15 microns is a Class 1.1 high explosive. If you get it too hot, or if you have a spark, it can either burn or explode low or high order. (If it explodes, you won't really care if it's high order or low order, in fact you won't have any more cares at all.)

Furthermore, grinding an oxidizer that is also a monopropellant to this level of fineness can not only be dangerous, but is illegal unless you have an explosives permit. The bottom line here is don't do it without the proper training, equipment and permits.

Enough said on the subject.

Bob
 
Methods are pretty cool, I personally prefer the melt and cast method but there are benifits to his method...

His recrystallized fuels work best with surcrose though, which isnt allowed at TRI. You can use dextrose with his method but its not as common.

I use sorbitol.
 
I too vote for the coffee grinder. I have done it personally and had no problems.
 
This is a cool thread, fianlly some meaty discussion. Thank goodness the mods are sleeping.

By spark free I was planning on making one using a plastic drum and marbles as my medium. I see what you mean though.

Can Potassium Perchlorate be ground safely?
 
Originally posted by Catocene
Rock tumbler anyone?

Use steel ball bearings with no fuels mixed with the KNO3. You can get a tumbler from Harbor Freight at about $30. Good for other uses that shant be named as well.
Click to expand...

Are you sure you want to use STEEL ball bearings? Wouldn't you want to use something less likely to spark?
 
Steel is fine whenn milling one chemical at a time. For KNO3 or just about any hard oxidizer you'll want hard media. Antimony hardened lead media works, but you'll get alot ofcontamiatio in your product.

Any spark would be fine as KNO3 DOES NOT BURN. Try it if you want, geta wee sampleand take a blow tourch to it. It'll melt. Leave itlong enough and it'll decompose but a spark just won't cause this.

A ball mill will give a finer product than a coffee mill just so you guys know. It takes longer but you'll end up with a much finer prooduct.
 
Originally posted by jraice
Methods are pretty cool, I personally prefer the melt and cast method but there are benifits to his method...

His recrystallized fuels work best with surcrose though, which isnt allowed at TRI. You can use dextrose with his method but its not as common.

I use sorbitol.
Click to expand...

[Dumb Question Alert On] What's TRI? And why is sucrose not allowed there? [Dumb Question Alert Off]
 
Originally posted by uncle_vanya
[Dumb Question Alert On] What's TRI? And why is sucrose not allowed there? [Dumb Question Alert Off]
Click to expand...

I believe he meant to say TRA...and yes, Sucrose is not allowed because of the elevated temps that it takes to cast it...

Johnnie
 
Well, I used the coffee grinder. That got it to a very fine powder. I then made up one of my infamous smokers and I can definitely say that the grinder made the mixture burn a lot cleaner, a lot less popping and sizzling than when I was using the granulated stuff.

Jason
 
James Yawn told me they arent and I remember it... Not that they are unsafe but they just havent been run by TRA (sorry, not TRI) or something technical... From what I have heard safety wise its not much more dangerous when recyrstallized, some may argue for melt/cast sorbitol is safest though because it has the lowest melting temp.
 
Ball mills work great! I ground up some saw chips from a chainsaw and came out with stuff finer than flour. I put them in the ball mill for a month and had a great end result.

Edward
 
Originally posted by edwardw
Ball mills work great! I ground up some saw chips from a chainsaw and came out with stuff finer than flour. I put them in the ball mill for a month and had a great end result.

Edward
Click to expand...

A MONTH !!! I want to build motors this weekend. If wanted them a month from now I'd start them a month from now. LOL
 
I have a friend who polishes rocks and he can leave them in there for 6 months.... :)

Edward
 
But those are rocks. You can keep them on display for years. If you make a rocket motor it will burn in seconds.
 
Originally posted by rdm59
Are you sure you want to use STEEL ball bearings? Wouldn't you want to use something less likely to spark?
Click to expand...

Yeah, I was thinking the same thing. Lead sounds safe to me.:)
 

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