Ammonium nitrate storage

Ammonium nitrate is made at Fisons Ltd and stored in solution in two heated tanks to prevent ciystalization. One tank holds 3,100 tonnes and the other 6,200 tonnes of 92% aqueous ammonium nitrate solution. Trains laden with oil refinery products from the Mobil and Shell refineries pass the factory on a near embankment. A derailment could spill and ignite hydrocarbons from a rail tank car to explode an ammonium nitrate storage tank. Suggestions were made to mitigate or prevent such a domino effect... 

As described previously, phosphate rock dust, fluorides, acids, ammonia, and radioactive elements are the main health hazards in fertilizer production. Fertilizer products are of low hazard however, ammonium nitrate storage areas must be kept free of organic materials, Coating materials such as crystalline silica are hazardous if inhaled. 

There are also five Chemical Emergency Preparedness and Prevention Advisories listed at http //www.epa.gov/emergencies/publications.htm. These advisories cover such timely topics as Solid Ammonium Nitrate Storage, Handling and Management , as well as advisories on Hydrogen Fluoride, Advisories Ammonia, and others. 

Off-spec ammonium nitrate storage exploded in warehouse, destroying plant. 

It is prepared by the direct nitration of toluene with a mixture of nitric and sulphuric acids. TNT is a very stable, violent and powerful high explosive, but less sensitive to shock and friction than picric acid. It is widely used as a filling for shells, bombs, etc. often mixed with ammonium nitrate and other high explosives. The lower grades of TNT may contain isomers which under hot storage conditions may give rise to exudation. 

Sohd ammonium nitrate occurs in five different crystalline forms (19) (Table 6) detectable by time—temperature cooling curves. Because all phase changes involve either shrinkage or expansion of the crystals, there can be a considerable effect on the physical condition of the sohd material. This is particularly tme of the 32.3°C transition point which is so close to normal storage temperature during hot weather. 

Decomposition and Detonation Hazard. Ammonium nitrate is considered a very stable salt, even though ammonium salts of strong acids generally lose ammonia and become slightly acidic on storage. For ammonium nitrate, endothermic dissociation from lowering pH occurs above 169°C. 

Exothermic Decompositions These decompositions are nearly always irreversible. Sohds with such behavior include oxygen-containing salts and such nitrogen compounds as azides and metal styphnates. When several gaseous products are formed, reversal would require an unlikely complex of reactions. Commercial interest in such materials is more in their storage properties than as a source of desirable products, although ammonium nitrate is an important explosive. A few typical exampes will be cited to indicate the ranges of reaction conditions. They are taken from the review by Brown et al. ( Reactions in the Solid State, in Bamford and Tipper, Comprehensive Chemical Kinetics, vol. 22, Elsevier, 1980). 

Walker, Hazards Analysis of Holston Ammonium Nitrate/Nitric Acid Storage and Transfer System , Rept No AO8204-520-11-005, Here ... 

Further properties which a detonating fuse should have are the ability to initiate blasting explosives (tested with suitable relatively insensitive mixtures usually of TNT and ammonium nitrate) resistance to low temperatures without cracking on flexing and to hot storage without desensitisation and toughness to prevent damage from stones, etc. The fuse must always be waterproof and must often withstand diesel oil, which can separate from ANFO. 

Code for the Storage of Ammonium Nitrate Explosive Materials Code... 

Heat, and sometimes gas, transfer from the core of a bulk material, also influences auto-ignition and explosion. The concept of critical mass is not limited to nuclear explosives (though shape is also important). Some entries in this text, such as sodium chlorate, ammonium nitrate and ammonium perchlorate, have proved extremely destructive dining industrial storage by the tens of tonnes, but are incapable of explosion at the ten gramme scale. Many other entries are for hazards significant only beyond laboratory scale [1]. 

These results define the conditions for the critical size of storage for compounds such as ammonium nitrate as a function of the ambient temperature T0 [7], Similarly, it represents the variation in mass of combustible material that will... 

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