Decomposition Of Ammonium Nitrate Research Articles

Influence of Potassium Chloride on the Thermal Decomposition of Ammonium Nitrate

The thermal decomposition of ammonium nitrate (AN), activated carbon (AC), and potassium chloride (KCl) mixtures are investigated. The thermal properties were studied using differential scanning calorimetry (DSC) and the evolved gas was analyzed using thermogravimetry with mass spectroscopy (TG-DTA-MS). The time to maximum rate (TMRad) was then calculated using commercial thermal analysis software. DSC measurements of an AN/KCl mixture in a sealed sample pan showed a sharp exothermic decomposition and lower onset temperature than pure AN, whereas AN/KCl in an open pan exhibited an endothermic reaction. A mixture of AN/AC/KCl exhibited a lower onset temperature than both AN/AC and AN/KCl. TG-DTA-MS results revealed HCl gas was evolved from AN/KCl, which indicated the reaction of KCl with HNO3 dissociated from AN to form HCl, and the subsequent destabilization of AN and AN/AC by HCl. TMRad calculations showed that AN/KCl underwent a run-away reaction within one day under closed adiabatic conditions above 180°C.

Ammonium nitrate thermal decomposition with additives

Runaway reactions present a potentially serious threat to the chemical process industry and the community; such reactions occur time and time again often with devastating consequences. The main objective of this research is to study the root causes associated with ammonium nitrate (AN) explosions during storage. The research focuses on AN fertilizers and studies the effects of different types of fertilizer compatible additives on AN thermal decomposition. Reactive Systems Screening Tool (RSST) has been used for reactivity evaluation and to better understand the mechanisms that result in explosion hazards. The results obtained from this tool have been reported in terms of parameters such as “onset” temperature, rate of temperature and pressure rise and maximum temperature. The runaway behavior of AN has been studied as a solid and solution in water. The effect of additives such as sodium sulfate (Na2SO4) and potassium chloride (KCl) has also been studied. Multiple tests have been conducted to determine the characteristics of AN decomposition accurately. The results show that the presence of sodium sulfate can increase the “onset” temperature of AN decomposition thus acting as AN thermal decomposition inhibitor, while potassium chloride tends to decrease the “onset” temperature thus acting as AN thermal decomposition promoter.

Kinetics of Nano Titanium Dioxide Catalyzed Thermal Decomposition of Ammonium Nitrate and Ammonium Nitrate‐Based Composite Solid Propellant

AbstractThis study deals with the influence of nanosized titanium dioxide (TiO2) catalysts on the decomposition kinetics of ammonium nitrate (AN) and ammonium nitrate‐based composite solid propellant. TiO2 nanocatalyst with an average particle size of 10 nm was synthesized by sol‐gel method using titanium alkoxide as precursor. Formation of nanostructured TiO2 and presence of its anatase and brookite phases was confirmed by powder X‐ray diffraction (PXRD) and selected area diffraction (SAED) studies. Nano TiO2 was further characterized by transmission electron microscopy (TEM), infrared (IR) spectroscopy, and thermogravimetry. The catalytic effect of TiO2 nanocatalysts on the solid state thermal decomposition reaction of AN and nonaluminized HTPB/AN propellant was evaluated. To ascertain the effectiveness of the TiO2 nanocatalyst, the thermal kinetic constants for the catalytic and non‐catalytic decomposition of AN and AN propellant samples were computed by using a nonlinear integral isoconversional method. Catalytic influence was evident from the lowering of activation energy for the catalyzed decomposition reactions. Apparently, the nanocatalysts provide Lewis acid and/or active metal sites, facilitating the removal of AN dissociation products NH3 and HNO3 and thereby enhance the rate of decomposition. The changes in the critical temperature of thermal explosion of AN and AN propellant samples due to the addition of TiO2 nanocatalyst were also computed and the possible reasons for the changes are discussed.

Combined experimental and kinetic modeling approaches of ammonium nitrate thermal decomposition

This experimental and modeling study aimed at better understanding the impact of the operating conditions on the interplay between ammonium nitrate (AN) decomposition pathways and their coupling with gas-phase chemistry. Experimental analysis and kinetic modeling were combined to elucidate the role of operating conditions on ammonium nitrate thermal decomposition. A new condensed-phase semi-detailed kinetic mechanism was developed and validated against original experiments performed in this study and experiments from other groups. This mechanism was coupled to a gas-phase mechanism, making it possible to quantify the contributions of condensed-phase and gas-phase reaction pathways to AN thermal decomposition at different heating rates. The study revealed that T50 (temperature at 50% conversion) increases strongly with the heating rate, favoring highly activated reactions. Even at typical burning surface temperatures (350 °C), gas-phase reactions involving nitramide and nitric acid play a significant role. The thermal deNOx pathway and hydroxylamine decomposition impact significantly NH3 consumption in the monopropellant flame zone.

Study of incompatibility of ammonium nitrate and its mechanism of decomposition by theoretical approach

The dramatic accident involving ammonium nitrate (AN) that took place at Toulouse in September 2001 has once again focused attention to the complex hazards pertaining to this chemical. Despite the significant efforts made to increase AN safety over the whole supply chain, we are still facing insufficient knowledge of the actual mechanisms of ammonium nitrate decomposition that may take place in abnormal situations. The paper proposes a theoretical study of chemical incompatibilities of ammonium nitrate with the aim to better understand the driving mechanism(s) through which the explosive reaction takes place with the neat or contaminated substance, to identify what molecules can realistically be generated from this process and to estimate the energy involved. The results, coupled with experimental data, should allow a better understanding of ammonium nitrate hazard profile.

The effect of Cu-loading on different reactions involved in NH3-SCR over Cu-BEA catalysts

In this study, we investigate the effect of varying copper loading in Cu-BEA on different reactions involved in the SCR mechanism. The catalysts were characterized by BET, ICP-AES, and UV–Vis. Enlarged ammonia storage was observed when increasing the copper loading mainly owing to loosely bonded NH3, but for over-exchanged samples, a new high-temperature shoulder was also observed. The N2O production significantly grew with increasing copper loading. In addition, the reaction rates of NO oxidation and NH3 oxidation per Cu site were higher on the high-loaded copper samples compared to those with lower loading. However, the opposite results were found for NH3 SCR, but differences were small for this reaction. Ammonium nitrate formation and decomposition were examined during a variety of temperature-programmed desorption (TPD) experiments, and three regions related to the presence of acid sites and low- versus high-loaded copper sites were observed. When dosing NO2 before NH3, ammonium nitrate species were formed but in lower amounts than if NH3 and NO2 were dosed simultaneously.

Влияние хлоридов феррума(ІІІ) и купрума(ІІ) на термическое разложение енергонасыщенных систем на основе аммиачной селитры

Влияние хлоридов феррума(ІІІ) и купрума(ІІ) на термическое разложение енергонасыщенных систем на основе аммиачной селитры

Simultaneous ammonium nitrate decomposition and NOx emission reduction in a novel configuration of membrane reactor: A simulation study

In thermal decomposition process, ammonium nitrate decomposition takes place in fluidized bed reactor (FR) and nitrogen oxide (NOx), as an undesirable product is produced in high temperatures. In this study, two novel configurations named membrane fluidized bed reactor (MFR) and free air membrane fluidized bed reactor (AMFR) is proposed to reduce NOx emission. Models predictions are validated by experimental data presented by Bhowmick et al. The results show 16% and 7% decrease in NOx concentration in AMFR and MFR respectively, compared with FR. Reduction of NOx emission and enhancement of ammonium nitrate conversion, demonstrate superiority of AMFR to previous configurations.

An Environmentally Friendly Configuration for Ammonium Nitrate Decomposition

Because of environmental concerns about nitrate and NOx emissions, the present study proposes a novel configuration in order to enhance thermal decomposition of ammonium nitrate (AN) in an environmentally friendly manner. Conventional thermal decomposition of AN takes place in a fluidized-bed reactor (FR) at high temperature, causing high AN conversions as well as considerable amount of NOx formation. The novel configuration considered in this work consists of two cascading fixed-bed and fluidized-bed dual reactors (CFFDRs). Thermal decomposition of AN occurs in the first reactor or the fluidized bed one and NOx is produced as a result. The following fixed bed reactor is a place for the selective catalytic reduction of NO with NH3. Operating conditions for the proposed CFFDR are optimized to achieve a minimum amount of AN as well as NOx via differential evolution (DE) method. Results illustrate that the AN conversion in this novel configuration reaches 98%, which is 42% in the conventional FR. Furthermore, ∼30 ppm NOx exits the conventional FR while in the proposed dual configuration 6 ppm NOx is produced. Therefore, in this novel concept, not only is AN decomposition enhanced, but NOx emission also is reduced.

Review on Thermal Decomposition of Ammonium Nitrate

In this review data from the literature on thermal decomposition of ammonium nitrate (AN) and the effect of additives to their thermal decomposition are summarized. The effect of additives like oxides, cations, inorganic acids, organic compounds, phase-stablized CuO, etc., is discussed. The effect of an additive mainly occurs at the exothermic peak of pure AN in a temperature range of 200°C to 140°C.

The ammonium nitrate and its mechanism of decomposition in the gas phase: a theoretical study and a DFT benchmark

The decomposition mechanism of ammonium nitrate in the gas phase was investigated and fully characterized by means of CBS-QB3 calculations. Five reaction channels were identified, leading to the formation of products (N2, H2O, O2, OH, HNO, NO3) found in the experimental works. The identified mechanism well underlines the origin of the chemical hazard of ammonium nitrate which is related to the exothermicity of the lowest decomposition channels. Furthermore, the high barrier to overcome in the rate determining step well explained the fact that the reaction is not usually spontaneous and requires a significant external stimulus for its onset. An accurate DFT benchmark study was then conducted to determine the most suitable exchange-correlation functional to accurately describe the reaction profile both in terms of structures and thermochemistry. This evaluation supports the use of the M06-2X functional as the best option for the study of ammonium nitrate decomposition and related reactions. Indeed, this level of theory provided the lowest deviations with respect to CBS-QB3 reference values, outperforming functionals especially developed for reaction kinetics.

Kinetics and mechanism of hydrothermally prepared copper oxide nanorod catalyzed decomposition of ammonium nitrate

One of the key aspects in the development of materials science is the synthesis of particles with specific size and morphology for catalytic applications. Nowadays, nanostructured materials with specific morphology are gaining great importance in the field of catalysis. Thin, one-dimensional, monodispersed CuO nanorods with a significantly higher aspect ratio of 5, were successfully prepared by the hydrothermal method with subsequent ultrasonication. The formation of pure monoclinic CuO nanorods was confirmed by powder XRD and SAED. The CuO nanorod growth mechanism is investigated by using TEM and further characterized by FTIR, UV–visible spectroscopy and thermogravimetry. The catalytic decomposition of ammonium nitrate, an environmental friendly rocket propellant oxidizer, over the synthesized CuO nanorods was investigated. The thermal kinetic constants for the catalytic and noncatalytic decomposition of ammonium nitrate samples were computed by using model free (differential and non-linear integral) and model fitting approaches. The catalytic influence was evident even with 1% catalyst concentration. The model fitting method suggested contracting cylinder mechanism as the effective mechanism for all the investigated samples. Apparently, the CuO nanorods provide Lewis acid and/or active metal sites, facilitating the removal of ammonium nitrate decomposition inhibition species such as NH3 and thereby enhance the rate of decomposition.

Treatment of off-gas evolved from thermal decomposition of sludge waste

Korea Atomic Energy Research Institute (KAERI) started a decommissioning program of a uranium conversion plant. The treatment of the sludge waste, which was generated during the operation of the plant, is one of the most important tasks in the decommissioning program of the plant. The major compounds of sludge waste are nitrate salts and uranium. The sludge waste is denitrated by thermal decomposition. The treatment of off-gas evolved from the thermal decomposition of nitrate salts in the sludge waste is investigated. The nitrate salts in the sludge were decomposed in two steps: the first decomposition is due to the ammonium nitrate, and the second is due to the sodium and calcium nitrate and calcium carbonate. The components of off-gas from the decomposition of ammonium nitrate at low temperature are NH3, N2O, NO2, and NO. In addition, the components from the decomposition of sodium and calcium nitrate at high temperature are NO2 and NO. Off-gas from the thermal decomposition is treated by the catalytic oxidation of ammonia and selective catalytic reduction (SCR). Ammonia is converted into nitrogen oxides through the oxidation catalyst and all nitrogen oxides are removed by SCR treatment besides nitrous oxide, which is greenhouse gas. An additional process is needed to remove nitrous oxide, and the feeding rate of ammonia in SCR should be controlled properly for evolved nitrogen oxides.

Thermal Denitration of Ammonium Nitrate Solution in a Fluidized-Bed Reactor

Ammonium diuranate (ADU) filtrate, which contains mainly ammonium nitrate (80–100 g/L), is generated during hydrometallurgical processing of uranium. This filtrate stream poses a disposal problem because of its high nitrate content and residual radioactivity. Fluidized-bed thermal denitration is considered as a suitable chemical-free disposal option for the aqueous waste nitrate stream. Hence, investigations to explore the decomposition of ammonium nitrate in a fluidized bed have been carried out. To enable theoretical analysis and performance evaluation of the process, a mathematical model was developed. The model is based on two-phase theory of a bubbling fluidized bed. Model calculations were used to predict the axial concentration profile of ammonium nitrate in the emulsion and bubble phases and the axial temperature profiles of gas bubbles, emulsion gas, and emulsion particles. The mechanism of decomposition of ammonium nitrate in a fluidized bed was explored, and the conversion of ammonium nitrate w...

Impacts of climate change on ground level gas-phase pollutants and aerosols in the Iberian Peninsula for the late XXI century

Climate change alone influences future air pollution levels through modifications of gas-phase chemistry, transport, removal, and natural emissions. Hence, the goal of this study is to determine at what extent concentrations of air pollutants respond to changes over the Iberian Peninsula under a climate change scenario. The methodology includes the use of the regional modeling system MM5 (regional climate model version)-CHIMERE for two nested domains covering Europe and the Iberian Peninsula. Two time slices driven by ECHO-G global circulation model covering from 1991 to 2010 and 2071 to 2100 under the SRES A2 scenario have been compared. Climate change influences the concentrations of both gas-phase pollutants and aerosols through changes in temperature, precipitation, mixing height, transport, humidity, and oxidant levels. The trends of variation of ozone (changes up to 5 ppb, +10% increase during summertime) and aerosols over southwestern Europe are influenced by the higher mean temperature modeled for the future climate (up to +5.4 K), since it favors the formation of secondary gas-phase products. It also enhances sulphates (+2 μg m−3) and secondary organic aerosols (SOA) (+2.5 μg m−3 under SRES A2 scenario) and contributes to the decomposition of ammonium nitrate, remaining in the gas phase. Further, the 17% percent decrease of precipitation modeled for 2071–2100 has a strong effect in the frequency of the washout and therefore in the levels of natural aerosols: the concentrations of aerosols decrease with increasing precipitation as wet deposition provides the main aerosol sink.

Thermal decomposition of ammonium nitrate with three-component additives

Thermal decomposition of ammonium nitrate with three-component additives

Kinetics and mechanism of thermal decomposition of ammonium nitrate and sulfate mixtures

Fundamental kinetic aspects of the decomposition of mixtures and double salts of ammonium nitrate and ammonium sulfate were studied. The effect of water and sulfuric acid additives on the thermal decomposition rate of ammonium nitrate and sulfate mixtures was examined. The constant of proton exchange between nitric acid and the sulfate anion in molten ammonium nitrate was estimated.

Anatase–brookite mixed phase nano TiO 2 catalyzed homolytic decomposition of ammonium nitrate

Compared to the conventional ammonium perchlorate based solid rocket propellants, burning of ammonium nitrate (AN) based propellants produce environmentally innocuous combustion gases. Application of AN as propellant oxidizer is restricted due to low reactivity and low energetics besides its near room temperature polymorphic phase transition. In the present study, anatase–brookite mixed phase TiO 2 nanoparticles (∼10 nm) are synthesized and used as catalyst to enhance the reactivity of the environmental friendly propellant oxidizer ammonium nitrate. The activation energy required for the decomposition reactions, computed by differential and non-linear integral isoconversional methods are used to establish the catalytic activity. Presumably, the removal of NH 3 and H 2O, known inhibitors of ammonium nitrate decomposition reaction, due to the surface reactions on active surface of TiO 2 changes the decomposition pathway and thereby the reactivity.

Humphry Davy

Humphry Davy

Abiotic Mechanism for the Formation of Atmospheric Nitrous Oxide from Ammonium Nitrate

Nitrous oxide (N2O) is an important greenhouse gas and a primary cause of stratospheric ozone destruction. Despite its importance, there remain missing sources in the N2O budget. Here we report the formation of atmospheric nitrous oxide from the decomposition of ammonium nitrate via an abiotic mechanism that is favorable in the presence of light, relative humidity and a surface. This source of N2O is not currently accounted for in the global N2O budget. Annual production of N2O from atmospheric aerosols and surface fertilizer application over the continental United States from this abiotic pathway is estimated from results of an annual chemical transport simulation with the Community Multiscale Air Quality model (CMAQ). This pathway is projected to produce 9.3(+0.7/-5.3) Gg N2O annually over North America. N2O production by this mechanism is expected globally from both megacities and agricultural areas and may become more important under future projected changes in anthropogenic emissions.