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Purification method 2 – Crystallization using methanol
The following method will show you at least the best known purification method. This is done by boiling Methanol Alchohol and adding the fertillizer Ammonium nitrate until no more of it will dissolve. 20.2 g AN (NH4NO3) per 100 g methanol at 30 degrees C. There are values for other temperatures too, but solubility doesn't seem to vary rapidly.This is then cooled in an ice bath and the white crystalls deposited at the bottom are pure Ammonium Nitrate. Thus the pure Ammonium nitrate can be heated on a lowest temperature on a pan in the oven until very dry. Store it in a tightly closed container.
Another similar method is the following: to purify "dissolve the fertilizer in hot methanol and filter the solution. By mixing the solution with an equal volume of unleaded gasoline, the ammonium nitrate will instantly crystallize."
Cold packs as a source for pure AN
If you are having problems converting fertilizer to a more pure form just try using some other source of ammonium nitrate, like cold packs, or another brand of fertilizer containing ammonium nitrate. The AN from Cold packs is however 10 times as expensive as the fertilizer AN resulting in a limitation regarding the procurement of large quantities.
The shelf life of cold packs (100% AN) is approximately 1-2 years from production date which is usually specified on each package. So, if you need a large quantity, start you’re an acquisition phase aprox 6 months prior to the execution of the mission. Note that the special plastic and vacuum packing is done to ensure this long shelf life so if you take out the AN from the cold packs it might influence the shelf life, regardless of how effectively you manage to contain it. If you are packing it yourself with traditional plastic the shelf life may be dramatically reduced, perhaps down to 4 weeks with poor packing. This will depend on how well you pack it, how much oxygen is available, humidity, temperature during storage etc. Container: heat- OR acid-resistant OR plastic). Instead of storing a 500 kg (which might be poorly packed for long term storage) you should consider breaking the large bag into smaller 50 kg bags. Try to order specialized plastic bags for this purpose.
Mixing AN with fuel
A more common and almost as effective method of mixing is by uniformly soaking prills in opened bags with 8 to 1O percent of their weight of oil. After draining for at least a half hour the prills will have retained about the correct amount of fuel oil.
The fuel will disperse relatively rapidly and uniformly. Inadequate priming imparts a low initial detonation velocity to a blasting agent, and the reaction may die out and cause a misfire. So ensure a large enough booster/blasting cap.
Place the AN into the waterproof container. Sprinkle the diesel fuel onto the AN. Do not “stir” these materials, as that will cause them to pack together. Let stand for 1 hour. Seal the waterproof container.
Note: if powdered AN is being used and it becomes packed, it may be fluffed by ruffing a handful back and forth across a piece of screen or a cheese grater. If AN prills are used (compared to powdered AN) a larger booster charge must be used. Finally, ANFO charges must be at least 5 cm in diameter or they will not detonate properly.
Size of prills matter
However, there is usually little you can do about this fact, with the exception of choosing to powder the AN. In the mining industry, the term ANFO specifically describes a mixture of solid ammonium nitrate prills and No. 2 fuel oil (heating oil.) In this form, it has a bulk density of approximately 840 kg/m3. The density of individual prills is about 1300 kg/m3, while the density of pure crystalline ammonium nitrate is 1700 kg/m3. It is notable that AN prills used for explosive applications are physically different from fertilizer prills; the former contain approximately 20% air. These versions of ANFO which use prills are generally called explosives grade, low density, or industrial grade ammonium nitrate. These voids are necessary to sensitize ANFO: they create so-called "hot spots".
How to pulverize large quantities of ammonium nitrate prills/granules
For small quantities you may simply use a wood roller, the wooden kitchen tool used for rolling dough, on a wood base. However, if you want to pulverize large amounts of AN, 100 kg+, you want to use more advanced methods.
Grinding method 1
Commercial coffee grinders: dedicate one grinder for use on oxidizers. We don't want fires or explosions when we're grinding chemicals. Never grind complete or mixed compositions such as black powder in a coffee grinder. The AN should not react with any material in the grinder as long as you use steel blades.
I have found two kinds of coffee grinders: blade-grinders and burr-mills. Don't get a burr-mill; they don't work as well as blade-grinders (at least not for coffee beans, perhaps for AN prills). The blade-grinders have a stainless steel blender type blade that spins at high speeds in the bottom of the material cup, pulverizing the material in the process. When evaluating whether to use a smaller, less expensive, blade-type coffee grinders; know that they really don't last too long if you mill chemicals for a minute or two at a time. To use them, mill your chemicals in pulses of a few seconds at a time. Shaking them while pulse-grinding can give you even faster results. There are different types of coffee grinders. You may want to choose an espresso variant as it will produce a finer powder. However, expect this factor to result in a doubled grinding time.
Be careful of heat buildup. Avoid aluminium blades, use steel blades (it’s usually steel as default). Avoid sparks. Quickly put in airtight container as powdered AN absorb water from air.
Grinding speed; depends on grinder. I did find an example from a commercial espresso grinder:
57 g in 20 seconds which equals 171 g per minute, 10,26 kg per hour. With this speed it would take 97,5 hours to grind 1000 kg of AN prills/granules. However, if you use a grinder constantly then expect it to only last a few hours. So you will probably need up to 10 grinders for 1000 kg prills. Expect the total amount of hours to exceed 200 hours as you don’t want the grinder to overheat. I heard that Baader, the Marxist scumbag from Red Army Fraction bought tens of grinders as they regularly broke down. He even bought a really expensive one but that one broke down as well. They ended up using wood rollers resulting in limited amounts of end product.
Prices range from 30 Euro up to 800 Euro.
Grinding method 2
I have not confirmed this method but it looks good in theory. An electric garbage disposal unit/food waste disposer/sink grinder, aprox 370 W, 2600 RPM, cost: 200 Euro. No knives or blades. Instead, it is a rotating mechanism which presses the material out through small holes in the outer walls.
Grinding method 3 (recommended)
I have never seen this method mentioned in relation to AN prill grinding. However, theoretically, it sounds like a wonderful idea.
A barley crusher/malt grinder is used for grinding barley in micro-brewery operations (enthusiasts brewing their own beer etc). It is a mini grinding mill, a unit operation designed to break a solid material into smaller pieces.
There are two main suppliers of relatively inexpensive barley crushers; Barleycrusher.com and Crankandstein.net
Of the two I would recommend the Barleycrusher with the following specs:
· Roller assembly: 1,25” diameter x 5 “ length
· Models: 7 lb (3,2 kg) or 15 lb (6,8 kg), go with the 15 lb
· BC adjustment range: 0,015 to 0,070 thousands of an inch. Default set at 0,039. This is the way to fine tune your rollers, to adjust them so that you get finer powder etc.
· Rollers have: 12 TPI knurl
· Comes with a solid base with locators to center the Barley Crusher on a 5 gallon plastic pail. (Pail not included)
· The standard hopper holds 3,2 kg and the optional large hopper holds 6,8 kg. Using a 3/8 drillmotor at 500 RPM gives you a crush rate of 2,7 kg per minute
· The Barley Crusher is shipped fully assembled. There are no adapters needed to use a 3/8 drill motor.
· Cost: 15 lb variant, costs 115 USD with an additional 60 USD shipping
· A hand crank is included but it is advisable that you use a drill (you just fasten the drill bit where the hand crank used to be)
· You will also want a high quality drill with adjustable speed (cheap version drills may be just as good as long as they have an adjustable speed). You want to use a relatively low speed (150-200 RPM). However, you should test and confirm this as higher speeds may be viable. You should not select a battery drill as each battery will only have enough power for 10-12 kg of corn (prills) according to one forum source. Buy a second hand, high quality drill on your local online marketplace or ebay. Just keep in mind that the US voltage (110-120 V) is different from the European (220-230 V).
· Example drill: http://www.dewalt.no/powertools/productdetails/catno/D21520/
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