Ammonium nitrate safety

Safety Considerations. Ammonium nitrate can be considered a safe material if treated and handled properly. Potential hazards include those associated with fire, decomposition accompanied by generation of toxic fumes, and explosion. 

Nitrous gases originating from the combustion units in nitric acid plants carry small amounts of unreacted ammonia, NH3. The ammonia may react with the nitrous gas to form microscopic particles of ammonium nitrate that adhere to solid surfaces. Within a short time, there is a growing layer of ammonium nitrate salt covering the internal surface of the nitrous gas compressor (Figure 4-27). This layer can obstruct the flow passages because it tends to increase the power consumption, provoke excessive vibrations, and even present a safety hazard since ammonium nitrate explosions can occur. 

In the context of safety of the process of neutralisation of nitric acid with ammonia, the effects of temperature (160-230°C), pressure (2.3-9.8 bar), and concentrations of ammonium nitrate (86-94%) and of nitric acid (0-4%) upon decomposition rate were studied. 

An account of a serious warehouse explosion (15 dead, 141 injured). The two principal detonations were mostly due to ammonium nitrate, of which some hundred tonnes had been present, but the initiating fire was first observed in ammonium persulfate. This had been promiscuously stored alongside potassium permanganate, matches, potassium nitrate and sodium sulphide (or possibly sulphite), inter alia. None of these would improve the safety of ammonium persulfate. It was shown that the persulphate gives an immediate exothermic reaction with the sulphide. This was ascribed as the ultimate initiation. It was concluded that oxidants and... 

Large quantities of explosives are used every year. In the United States, for example, the annual consumption exceeds over 2 million tonnes. Most are used for commercial purposes and are ammonium nitrate-based formulations. There are less than a dozen chemical explosives that are manufactured in bulk quantities, and most of these were discovered in the 50-year period between 1850 and 1900. New explosives have been synthesized but optimization of the formulations takes decades and is very expensive. Consequently, any new material has to offer very significant advantages, either in terms of unique performance for military applications or in terms of cost and safety for commercial applications. 

An unusual feature of the KA-process is that the reaction is conducted at 60-80 °C. Solutions of nitric acid in acetic anhydride are known to be prone to dangerous fume off at temperatures above ambient. However, a saturated solution of ammonium nitrate in fuming nitric acid can be added to warmed acetic anhydride without such danger. In fact, these reactions are commonly conducted at 60-80 °C as a matter of safety by preventing a build-up of unreacted starting material. The hexamine used in these reactions is in the form of the dinitrate salt, which is formed as a crystalline salt on addition of a saturated aqueous solution of hexamine to concentrated nitric acid below 15 °C. The use of hexamine dinitrate in this process reduces the amount of nitric acid needed for the nitrolysis. 

TATP can have a wide variety of appearances that are effected by the way the product is washed and allowed to crystallize. In addition, its appearance will be altered by any additives placed in the material. TATP has been mixed with ammonium nitrate, glue, TNT, mineral oil, and numerous other materials by terrorist groups in an attempt to increase either its power or its handling safety. Figure 3.7 shows photos taken by the author of TATP in two different countries. 

Ammonium nitrate (AN) was considered early as an environment-friendly alternative to AP but its multiple crystal phase-transitions at low temperatures and its poor performance precluded its use. The nitramine-based propellants are also likely to emerge as potential eco-friendly propellants as the combustion products are non-toxic and non-smoky, although the present day nitramine propellants do not match the high performance and high burn rates of AP-based composite propellants [62, 63]. At the same time, high pressure exponent and unstable combustion prevent their application in large rockets due to safety considerations [20]. The inclusion of Al powder and other additives increases the burn rate and also eliminates the combustion instability. 

It was also found that mixtures containing a large amount of ammonium nitrate (ammonium nitrate explosives) ensure much greater safety than dynamites or chlorate and perchlorate explosives. 

The two sets of photographs illustrated were taken by Cybulski. Both refer to safety explosives used in Poland, viz., ammonium nitrate type Metanit B (Fig. 131) and nitroglycerine (dynamite) type, Barbaryt AGI (Fig. 132). 

This led to the manufacture of Anzen-Bakuyaku ammonium nitrate safety explosives on the lines of European compositions, but later modified to suit the damp climate of Japan (Yamamoto [85]). The production of the following new explosives began in 1913 ... 

Safety exsplosive are known in the U.S.A. under the name of Permissible Explosives or simply permissibles. As in European countries their chief ingredient is ammonium nitrate. Permissibles may or may not contain nitroglycerine. 

ANFO can be mixed directly in the shot-hole by first pouring the ammonium nitrate into the shot-hole followed by the fuel oil. The main advantage of mixing on site is that no safety procedures are required for the transportation of fuel oil and ammonium nitrate, since fuel oil and ammonium nitrate are not classed as explosives. It is only when they are mixed together that the composition becomes an explosive substance. 

Cook off Test is briefly discussed is this volume, under Ammonium Nitrate, A354, Note a Ref Spencer Chemical Co, "Safety Data, Feb 4, i960... 

Impact-Friction Pendulum Test is briefly described, p A354, Note d), under Ammonium Nitrate Ref Spencer Chemical Co, "Safety Data, Kansas City, Mo(l960)... 

Wax Gap Test is one of the Detonation by Influence testa(qv) and is similar to the Booster Sensitivity test(qv). The Wax Gap Test is described briefly under Ammonium Nitrate, p A354, Note c and in mote detail in Spencer Chemical Company, "Safety Data, Kansas City,Mo(I960)... 

The sensitiveness of fused ammonium nitrate is distinctly higher, and approximates to that of TNT. Ammonium nitrate does not take fire from the hot flame produced by a safety fuse. 

Also according to Van Dolah ammonium nitrate-oil mixtures offer a certain dust explosion hazard and any electric equipment (switches controls, motors, lights) located in the plant should conform to the safety requirements or should be installed outside the plant. In order not to increase the dust explosion hazard no liquid hydrocarbon fuel with higher volatility than No. 2 Diesel fuel (minimum flash point of 145°F, ASTM closed-cup procedure) should be used as an admixture to ammonium nitrate. More volatile fuels, such as gasoline, kerosine or No. 1 Diesel fuel cannot be recommended according to Van Dolah, as they would seriously increase the hazard of a vapour explosion. 

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