I saw there were some questions regarding why powdered AN either does not work, or performs poorly in ANFO mixtures. Having EXTENSIVE experience in the past with all types of AN mixtures I can tell you all this: Prilled AN is used for ANFO because the sensitivity of ANFO is so low. What is accomplished by using prilled AN is a MUCH better absorbtion, better fuel/oxidizer contact, and less dense mixture when adding fuel oil (diesel #2 I believe). Basically if you are to look at some AN prills under a microscope (assuming they were properly prepared) you will see very small pores in the surface of the prill. These pores are connected to an intricate crystaline structure beneath the surface of the prill. When adding fuel oil, the oil is able to seep into the pores and fill the internal structure of the prill with and oil film basically. This means you get VERY VERY intimate contact of fuel oil and AN which increases the sensitivity. Also, as far as ANFO mixtures (and other AN mixtures....ask if you want to know what ones) are concerned, lower density equals increased sensitivity. The way this works is that when the FO fills the prills up and coats them there is intimate contact, which upon being subjected to a high velocity shockwave (usually from PETN/RDX 50:50 the way I like it) the small cavities inside the prill (which also contain some air) get ultra compressed and hence superheated instantly, which facilitates the reaction. Additionally, the air spaces between individual prills undergo the same superheating which furthers the reaction. Using powdered AN for ANFO, the mixture will lack these small pores and cavities (and therefore is also of higher density) and there will be less chance of enough superheated cavities existing to keep the activation energy high enough for the whole explosive to detonate. Also with powdered AN, there is very little space between each crystal of AN. What this means is that for ANFO mixtures, lower density equals higher sensitivity and hence greater ease of detonation. Hope that is helpful to you guys. Peace
Al

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