Rail car with ammonium nitrate didn't cause Texas blast: fire official
snip
West Fertilizer disclosed to a Texas state agency that it had 270 tons of ammonium nitrate on hand at the plant last year. There also had been persistent rumors that a rail car delivered to the plant by Union Pacific full of ammonium nitrate might have caught on fire and caused the blast.
But Kelly Kistner, assistant Texas state fire chief, ruled out the rail car of ammonium nitrate as the cause.
"What I can tell you today is that railcar that there's been questions about, that was full of ammonium nitrate, is not the cause of the fire or cause of the explosion. It is a victim of that explosion," said Kistner.
Union Pacific had confirmed that it delivered a rail car to the plant on April 15, two days before the blast, but declined to detail what was inside.
A spokeswoman for Union Pacific, Raquel Espinoza, said the railroad did not own the rail car or its contents.
"Photographs taken after the incident show the rail car lying on its side, largely intact, with no evidence of it being directly involved in the explosion or fire," she said in a statement emailed to Reuters on Tuesday.
"The car was knocked over by the explosion, resulting in some of its cargo being spilled. There are no visible signs of the cargo being burnt. Most of the cargo appears to have remained inside the rail car," Espinoza said.
The statement by Kistner on Tuesday did not completely eliminate ammonium nitrate as a possible cause of the blast because investigators have not commented on the stocks of ammonium nitrate other than the material in the rail car.
More than 70 state and federal agents are going through the scene "shovel by shovel," looking for the initial heat source, Kistner said.
more
http://www.reuters.com/article/2013/04/23/us-usa-explosion-texas-idUSBRE93M1I820130423
= new reply since forum marked as read
I'm glad this is answered.
I got the impression the state chemist was trying to deflect to Union Pacific. 
They've also got ATF involved at the scene.
it appeared that the main tracks, while damaged, were largely intact. The spur set going into the plant also seemed to still be there. The main tracks were raised, and it looked like that was enough for the blast to move them, the ties, and the bed. The tracks were visibly pushed together nearest to the blast. The rest looked relatively unharmed.
Had the blast centered on the rail-car, there probably would have been even more damage to the apartments and school, assuming it had the same amount of fertilizer as stored in the large tank or warehouse (I don't know which blew up, as both were obliterated.)
I guess it was the building that had been closest to the tracks that exploded and not the largest tank as you can see the crater in the following image. Plus, had it been a rail-car, there would have been a similar crater in the rail-bed, and you can see it's still pretty much intact:
After reading your post I checked Google images and found a close up of the intact rail-car on its side.
X2
Post the picture of the hopper car please or pm me the link. Got some hard headed RWN to show and tell...Thanks
Oh nos!! I can't imagine what a RWNJ would be thinking
Everyone knows that Union Pacific has more liability insurance coverage and deeper pockets than the rural fertilizer company that was illegally storing 270 tons of fertilizer. Now the owner of that company might be liable for millions of dollars from his own pocket.
it give off a Orange cloud. If the heat is not taken away (by flooding with water) it can Detonate as a explosive.
Deflagration (Lat: de + flagrare, "to burn down"
is a term describing subsonic combustion propagating through heat transfer; hot burning material heats the next ...This is how smokeless gunpowder propels a projectile.
Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives,[1] as well as in reactive gases. The velocity of detonations in solid and liquid explosives is much higher than that in gaseous ones, which allows the wave system to be observed with greater detail (higher resolution).
Gaseous detonations normally occur in confined systems but are occasionally observed in large vapor clouds. They are often associated with a gaseous mixture of fuel and oxidant of a composition, somewhat below conventional flammability limits. There is an extraordinary variety of fuels that may be present as gases, as droplet fogs and as dust suspensions. Other materials, such as acetylene, ozone and hydrogen peroxide are detonable in the absence of oxygen, a more complete list is given by both Stull[2] and Bretherick.[3] Oxidants include halogens, ozone, hydrogen peroxide and oxides of nitrogen.
In terms of external damage, it is important to distinguish between detonations and deflagrations where the exothermic wave is subsonic and maximum pressures are at most a quarter[citation needed] of those generated by the former. Processes involved in the transition between deflagration and detonation are covered thoroughly for gasses by Nettleton.[4]
The same smokeless gunpowder can also detonate under certain conditions when confined. Destroying the weapon and sometime the shooter.
I am Just guessing but the dry powder barn caught on fire for some reason and the hot debris fell into the bunker of pure AN at 35% to #38% Fertiler is a mixture or blend of AN, Phosporus, and Potassium (called NPK 10-20-10) or xxx is common. Oil leaking out of a wheel loader or a bob cat loader parked in the same spot every night can cause the fertiler to start self deflagrating and turn to fire then detonate. The AN started to deflagrate and the fire fighters would not be able to remove the heat by flooding due to lack of water and equipement. It burns very hot and produce O2 until it get so hot it detonate like the Texas city ship did.. The Nurse tanks outside with Anhydrous Ammonia may have became part of the explosion as a Fuel air bomb fire explosion. Anhydrous was probably venting off from heat and burned till the AN explosion.. Then the question come up did the anhydrous ammonia heat to 1500F and contribute to the explosion by detonating??
Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives,[1] as well as in reactive gases. The velocity of detonations in solid and liquid explosives is much higher than that in gaseous ones, which allows the wave system to be observed with greater detail (higher resolution).
Gaseous detonations normally occur in confined systems but are occasionally observed in large vapor clouds. They are often associated with a gaseous mixture of fuel and oxidant of a composition, somewhat below conventional flammability limits. There is an extraordinary variety of fuels that may be present as gases, as droplet fogs and as dust suspensions. Other materials, such as acetylene, ozone and hydrogen peroxide are detonable in the absence of oxygen, a more complete list is given by both Stull[2] and Bretherick.[3] Oxidants include halogens, ozone, hydrogen peroxide and oxides of nitrogen.
http://en.wikipedia.org/wiki/Anhydrous_ammonia
