Ammonium nitrate, decomposition

Ammonium nitrate prepared from ammonia obtained by the dry distillation of coal should not be used as component of any explosive material because of the ammonium thiocyanate and pyridine present in it (the latter as nitrate). When the ammonia liquor from dry distillation of coal was the sole source af ammonia and ammonium nitrate, decomposition of mixtures containing ammonium nitrate with TNT (amatols), was brought about at the melting point TNT reacted with ammonium thiocyanate or with pyridine nitrate and evolved gaseous products. Minute traces of these impurities were sufficient to cause abundant gas evolution to develop during the fusion, pouring, and cooling of amatol. 

Despite its brilliant results, it seems unlikely that the Solutia process can become a major source of phenol. Nitrous oxide availability is quite limited and its production on-purpose (by the conventional ammonium nitrate decomposition, which enables nitrous oxide of high purity to be produced for medical anesthetic applications, or even by selective oxidation of ammonia) would result too expensive. Therefore, the only reasonable scenario to exploit the Solutia process is its implementation close to adipic acid plants, where nitrous oxide is co-produced by the nitric oxidation of cyclohexanol-cyclohexanone mixtures and where it could be used to produce phenol instead of being disposed of However, the stoichiometry of the process is such that a relatively small phenol plant would require a world-scale adipic acid plant for its nitrous oxide supply. In fact, a pilot plant has been operated using this technology, but its commercialization has been postponed. 

Mirvakili, A., Samimi, F., and Jahanmiri, A. (2014) Simultaneous ammonium nitrate decomposition and NO emission reduction in a novel configuration of membrane reactor a simulation study. 

As Table 2.4 shows, the ammonium nitrate (AN) loaded explosives exhibit differences in observed and calculated performance (assuming either complete reaction or no reaction of the ammonium nitrate with the rest of the detonation products) sufficient to classify them as nonideal. The difference between observed and calculated detonation velocities increases with increased ammonium nitrate concentration, assuming complete ammonium nitrate decomposition. 

The shock position in the water and the experimental position of the explosive-water interface moved faster than the calculation without any additional decomposition behind the detonation front as shown in Figure 2.17. The explosive-water interface moved faster near the detonation front and remained a constant amount ahead of the calculated position. This indicates that additional ammonium nitrate decomposition must be taking place near the detonation front. 

The main drawback of the thermochemistry currently used to enhance oil recovery is a lack of control over downhole reaction. Since ammonium nitrate decomposition by the reaction NH NOj—> +2H2O + 0, 50 +... 

The most efficient method for reservoir heating and oil production via thermochemical gas lift effect should involve initial heating of a part of the reservoir by ammonium nitrate decomposition followed by injection of air into the reservoir [22]. The method proposed in Ref [22] has been abandoned for 40 years precisely because of a lack of control over the process, which may well result in burning up as much as 90% of the oil in place. For this reason, the heating should be conducted while keeping in situ oxidation of hydrocarbons under control in orderto prevent the formation of a combustion front. 

It was shown in Refs. [3, 6, 7] that the reservoir stimulated by BM reaction must be partially saturated with gas produced by ammonium nitrate decomposition. The ensuing decrease in viscosity enables the reservoir fluid to flow toward the wellbore under a pressure gradient and up the wellbore to the surface under a gas-lift effect. An estimated 18.5 GJ of heat and at least 20 tonnes of gas were produced by Eq. (1) in wells 1242 and 3003 in the Usinsk oil field. The pumping power due to the gas-lift effect created during two hours after the injection of chemicals into well no. 3003 reached a maximum of 11.2 kW. 

Consider the following example of treatment using the heat and gas produced by ammonium nitrate decomposition. Suppose that the reservoir... 

Table 17. Thermochemical Data for the Decomposition of Ammonium Nitrate...

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. 

Manufacture. Historically, ammonium nitrate was manufactured by a double decomposition method using sodium nitrate and either ammonium sulfate or ammonium chloride. Modem commercial processes, however, rely almost exclusively on the neutralization of nitric acid (qv), produced from ammonia through catalyzed oxidation, with ammonia. Manufacturers commonly use onsite ammonia although some ammonium nitrate is made from purchased ammonia. SoHd product used as fertilizer has been the predominant form produced. However, sale of ammonium nitrate as a component in urea—ammonium nitrate Hquid fertilizer has grown to where about half the ammonium nitrate produced is actually marketed as a solution. 

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. 

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). 

Ammonium nitrate decomposes into nitrous oxide and water. In the solid phase, decomposition begins at about I50°C (302°F) but becomes extensive only above the melting point (I70°C) (338°F). The reaction is first-order, with activation energy about 40 kcal/g mol (72,000 Btii/lb mol). Traces of moisture and Cr lower the decomposition temperature thoroughly dried material has been kept at 300°C (572°F). All oxides of nitrogen, as well as oxygen and nitrogen, have been detected in decompositions of nitrates. 

The decomposition of ammonium nitrate, an explosive, evolves 37.0 kj/mol. Use the reaction given in Problem 45 to calculate the mass of ammonium nitrate (in kilograms) required to produce the same amount of energy as that produced when one milligram of U-235 undergoes fission. 

Dinitrogen oxide, N20, gas was generated from the thermal decomposition of ammonium nitrate and collected over water. The wet gas occupied 126 mL at 21°C when the atmospheric pressure was 755 Torr. What volume would the same amount of dry dinitrogen oxide have occupied if collected at 755 Torr and 21°C The vapor pressure of water is... 

In the previous examples, the calculated enthalpies of decomposition are taken. The enthalpies of formation of the decomposition substances come from the corresponding chapters in Part Two. The published values of enthalpies of formation are favoured and use of the values estimated is only made when there is no experimental data. A few inorganic compounds have been added which are noted for their instability eg ammonium dichromate and ammonium nitrate. 

The action of sodium on ammonium nitrate results in a violent explosion. It is assumed to be caused by the decomposition of a hyponitrite formed as follows ... 

Nickei powder gives rise to dangerous reactions, which has led to accidents with potassium perchlorate (ignition), with chlorine at 600°C (ignition) and with ammonium nitrate at about 200°C (detonation). It catalyses the explosive decomposition of hydrogen peroxide. 

In the other method, particularly popular in Germany, the ammonium nitrate is replaced by an equimolar mixture of ammonium chloride and potassium or sodium nitrate. The reaction between the salts, which gives potassium or sodium chloride and ammonium nitrate or its decomposition products, is relatively slow and does not occur to a marked extent when the explosive is fired in an unconfined condition. This method of working is particularly effective in reducing the power of an explosive in the unconfined condition. Used alone it has not proved popular in Britain, because of the low power which tends to be developed under practical firing conditions. Moreover, the finely divided sodium chloride smoke which is produced by the explosive tends to be unpleasant for the miners. 

According to an O.S. amendment sheet, the procedure as described [1] is dangerous because the reaction mixture (dicyanodiamide and ammonium nitrate) is similar in composition to commercial blasting explosives. This probably also applies to similar earlier preparations [2]. An earlier procedure which involved heating ammonium thiocyanate, lead nitrate and ammonia demolished a 50 bar autoclave [3], TGA and DTA studies show that air is not involved in the thermal decomposition [4], Explosive properties of the nitrate are detailed [5], An improved process involves catalytic conversion at 90-200°C of a molten mixture of urea and ammonium nitrate to give 92% conversion (on urea) of guanidinium nitrate, recovered by crystallisation. Hazards of alternative processes are listed [6],... 

Decomposition of a 70% nitric acid-ammonium nitrate slurry explosive led to overflow, contact with wood and a fire. This spread to detonators, which initiated detonation of the slurry. 

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. 

A violent explosion in an ammonium nitrate store with sawdust-covered floors (to absorb spillage and prevent sparks) was attributed to local decomposition of the moist nitrate-containing sawdust, leading to temperature rise and spontaneous ignition. The observation of red-brown fumes just before the explosion supports this hypothesis. 

Alone, or Metals, or Metal compounds Mellor, 1940, Vol. 8, 327 1967, Vol. 8, Suppl. 2.2, 84, 96 It is an explosive of positive oxygen balance, less stable than ammonium nitrate, and has been studied in detail. Stable on slow heating to 300°C, it decomposes explosively on rapid heating or under confinement. Presence of zinc, copper, most other metals and their acetylides, nitrides, oxides or sulfides cause flaming decomposition above the m.p. (70°C). Commercial cobalt (cubes) causes an explosion also. 

A mixture of 0.5% of potassium permanganate with an ammonium nitrate explosive caused an explosion 7 h later. This was owing to formation and exothermic decomposition of ammonium permanganate, leading to ignition. 

Heating a mixture of an ammonium salt with a nitrite salt causes a violent explosion on melting [1], owing to formation and decomposition of ammonium nitrite. Salts of other nitrogenous bases behave similarly. Mixtures of ammonium chloride and sodium nitrite are used as commercial explosives [2], Accidental contact of traces of ammonium nitrate with sodium nitrite residues caused wooden decking on a truck to ignite [3],... 

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