Abstract Ammonium Nitrate Research Articles

Selected magnesium compounds as possible inhibitors of ammonium nitrate decomposition

Abstract Ammonium nitrate (AN) is considered to be a very hazardous and difficult to handle component of mineral fertilizers. Differential thermal analysis coupled with thermogravimetry and mass spectrometry was used to determine the possible inhibiting effect of selected magnesium compounds on thermal decomposition of AN. Each additive was mixed with AN to create samples with AN:magnesium compound mass ratios of 4:1, 9:1 and 49:1. Most of analyzed compounds enhanced thermal stability of ammonium nitrate, increasing the temperature of the beginning of exothermic decomposition and decreasing the amount of generated heat. Magnesium chloride hexahydrate was determined to accelerate the decomposition of AN while magnesium sulphate, sulphate heptahydrate, nitrate hexahydrate together with magnesite and dolomite minerals were defined as inhibiting agents.

Effect of potassium chloride on thermal stability of ammonium nitrate under acidic conditions

Ammonium nitrate (AN) can decompose and further detonate under some conditions, e.g., in the presence of impurities which act as promoters. Its reactive hazards have been widely studied for several years. However, many large accidents involving AN still happened frequently in the recent years. It is found that, for accidents in storage or transportation, the thermal runaway is a major factor. The main objective of the research is to examine the effect of potassium chloride (KCl) on the thermal stability of AN under acidic conditions. The thermal stability of samples was investigated by differential scanning calorimetry (DSC), accelerating rate calorimetry (ARC), the Cook-off test and the Dewar test. The results indicate that KCl can significantly reduce the thermal stability of AN under acidic conditions. The catalytic effect of KCl on the decomposition of AN is limited without acidic conditions. The scale effect also is important factor to influence the thermal stability of AN.

The effect of cellulose derivatives on the phase transition and thermal behavior of ammonium nitrate

Ammonium nitrate (AN) is a cheap oxidizer, which is widely used in chemical industries, fertilizers, industrial explosives, military explosives and propellants. It shows low reactivity, high hygroscopicity and polymorphic phase transitions in ambience condition where these behaviors can limit its application as an oxidizer in solid propellants. Since AN provides low decomposition temperature, maximum gas per unit weigh and non-toxic products, it is usually used as an oxidizer in gas generators. In this work, the effect of cellulose derivatives on the phase transition and thermal behavior of AN has been investigated in order to extend its uses in smokeless and environmentally safe solid gas generators. Thermal behaviors of AN/cellulose derivative matrixes, AN/KNO3 and AN/KF have been studied by the simultaneous application of thermogravimetry (TG) and differential scanning calorimetry. Moreover, a suitable computer code has been used to study the theoretical exhaust gases and mass of solid residues. The results suggest that cellulose acetate can be introduced as a good candidate for removing inappropriate phase transitions of AN.

Ammonium nitrate explosion hazards

Ammonium nitrate (AN) primarily is used as a fertilizer but it is also very important compound in the production of industrial explosives. The application of ammonium nitrate in the production of industrial explosives was related with the early era of Nobel dynamite and widely increased with the appearance of blasting agents such as ANFO and Slurry, in the middle of the last Century. Throughout the world millions of tons of ammonium nitrate are produced annually and handled without incident. Although ammonium nitrate generally is used safely, accidental explosions involving AN have high impact resulting in loss of lives and destruction of property. The paper presents the basic properties of ammonium nitrate as well as hazards in handling of ammonium nitrate in order to prevent accidents. Several accidents with explosions of ammonium nitrate resulted in catastrophic consequences are listed in the paper as examples of non-compliance with prescribed procedures.

Thermal Decomposition Behaviors and Burning Characteristics of AN/Nitramine-Based Composite Propellant

Ammonium nitrate (AN) has attracted much attention due to its clean burning nature as an oxidizer. However, an AN-based composite propellant has the disadvantages of low burning rate and poor ignitability. In this study, we added nitramine of cyclotrimethylene trinitramine (RDX) or cyclotetramethylene tetranitramine (HMX) as a high-energy material to AN propellants to overcome these disadvantages. The thermal decomposition and burning rate characteristics of the prepared propellants were examined as the ratio of AN and nitramine was varied. In the thermal decomposition process, AN/RDX propellants showed unique mass loss peaks in the lower temperature range that were not observed for AN or RDX propellants alone. AN and RDX decomposed continuously as an almost single oxidizer in the AN/RDX propellant. In contrast, AN/HMX propellants exhibited thermal decomposition characteristics similar to those of AN and HMX, which decomposed almost separately in the thermal decomposition of the AN/HMX propellant. The ignitability was improved and the burning rate increased by the addition of nitramine for both AN/RDX and AN/HMX propellants. The increased burning rates of AN/RDX propellants were greater than those of AN/HMX. The difference in the thermal decomposition and burning characteristics was caused by the interaction between AN and RDX.

Effect of Copper Oxide, Titanium Dioxide, and Lithium Fluoride on the Thermal Behavior and Decomposition Kinetics of Ammonium Nitrate

Ammonium nitrate (AN) is crystallized along with copper oxide, titanium dioxide, and lithium fluoride. Thermal kinetic constants for the decomposition reaction of the samples were calculated by model-free (Friedman's differential and Vyzovkins nonlinear integral) and model-fitting (Coats-Redfern) methods. To determine the decomposition mechanisms, 12 solid-state mechanisms were tested using the Coats-Redfern method. The results of the Coats-Redfern method show that the decomposition mechanism for all samples is the contracting cylinder mechanism. The phase behavior of the obtained samples was evaluated by differential scanning calorimetry (DSC), and structural properties were determined by X-ray powder diffraction (XRPD). The results indicate that copper oxide modifies the phase transition behavior and can catalyze AN decomposition, whereas LiF inhibits AN decomposition, and TiO2 shows no influence on the rate of decomposition. Possible explanations for these results are discussed. Supplementary materials are available for this article. Go to the publisher's online edition of the Journal of Energetic Materials to view the free supplemental file.

Growth of ammonium nitrate phase I and II dendrites

Ammonium nitrate (AN) phase I and phase II crystallize as dendrites from a melt containing respectively 0–4.5 and 4.5–12 wt% water. In-situ microscopic measurements show that the, for dendrites, characteristic ratio S / ϱ (where S = side branch spacing near the tip and ϱ = dendrite tip radius) varies between 2.3 and 5.1 for both AN(I) and AN(II). This agrees reasonably well with the theoretically derived value of 2.8 reported in the literature. The water concentration has a strong influence on the relation between the side branch spacing near the tip, S, and the tip growth rate, v, of the dendrites. The findings satisfy at least qualitatively the theoretically expected relationship between S and v.