Showing papers on "Ammonium perchlorate published in 2000"

Toxicology of Perchlorate

Abstract: Perchlorate (ClO4 −) is an anion commercially available as a salt with many cations. The most common forms of perchlorate include ammonium perchlorate (used as a solid rocket oxidant and ignitable source in munitions and fireworks) and potassium perchlorate (used in road flares and in air bag inflation systems as well as to treat Graves’ Disease [hypothyroidism] since the 1950s). Other forms of perchlorate include ammonium perchlorate, potassium perchlorate, sodium perchlorate, aluminum perchlorate, hydrazinium perchlorate, hydrogen perchlorate, hydroxylammonium perchlorate, lithium perchlorate, magnesium perchlorate, nitronium perchlorate, and perchloric acid. Perchlorate is also formed in laboratory waste as a byproduct of perchloric acid.

Preliminary development of a physiological model for perchlorate in the adult male rat: a framework for further studies.

Abstract: NASA and DoD use ammonium perchlorate (NH4ClO4) salt as an oxidizer in solid rocket propellants. Perchlorate salts are used in several applications such as flares, pyrotechnics, explosives, batteri...

Flame structure and burning rate of ammonium perchlorate/hydroxyl-terminated polybutadiene propellant sandwiches

Abstract: The gas-phase flame structure that forms over a lamina of hydroxyl-terminated polybutadiene (HTPB) binder (50 to 450 μm) sandwiched between layers of ammonium perchlorate (AP) has been investigated through measurements of the surface regression rate of the interface region, ultraviolet emission and transmission imaging of the gas-phase flame zone, and numerical simulations using simplified kinetics. The results show that over the observed pressure range (0.2 to 3.2 MPa), for binder widths from 100 to 450 μm, the regression rate is primarily a function of pressure ( r b ≈p 0.4 ) and is relatively independent of binder width. At binder widths below 100 μm, the regression rate is reduced, presumably due to locally lean conditions created by diffusive mixing. The imaging results suggest the existence of relatively UV-inactive leading-edge flames that form on the AP side of the interfaces adjacent to the surface and probably dominate the regression rate. These leading-edge flames are followed by a relatively UV-active secondary flame region downstream. Both the leading-edge and secondary flames show a tendency to merge into a single flame for thin binder and at lower pressures (low Peclet and Damkohler numbers), and to split into two distinct flames for thick binder ( Pe> 2) and at higher pressures (high Da ). The modeling results show that simplified kinetics representing the AP monopropellant flame and the AP-binder non-premixed flame, in the framework of a species and energy transport analysis, can predict surface heat feedback distributions that correlate reasonably well with observed surface profiles.

Condensed combustion products of aluminized propellants. II. evolution of particles with distance from the burning surface

Abstract: Condensed combustion products of a model propellant on the basis of ammonium perchlorate and aluminum were studied using the sampling technique. The granulometric composition of combustion products and the content of metal aluminum in particles of size from 1.2 µm to maximum were determined within the pressure range of 0.6–7.5 MPa at a distance from the burning surface up to 190 mm. A multimode structure of mass distributions of oxide particles within the size range of 1.2–40 µm was found. An empirical dependence of burnout of metal aluminum from agglomerates on the residence time of particles in the plume of combustion products of the propellant sample was obtained.

Study of Thermal Decomposition Kinetics of Low-temperature Reaction of Ammonium Perchlorate by Isothermal TG

Abstract: The kinetics of the thermal decomposition of ammonium perchlorate at temperatures between 215 and 260°C is studied, in this work, by measuring the sample mass loss as a function of time applying the isothermal thermogravimetric method.

Regulating Perchlorate in Drinking Water

Abstract: Perchlorate (ClO4 −) has emerged in recent years to become a significant new threat to drinking water supplies and the environment. It is an oxidizing anion that originates as contaminant in the environment from the dissolution of ammonium, potassium, magnesium, or sodium salts. Perchlorate is very mobile in aqueous systems and can persist for many decades under typical ground and surface water conditions.

The Thermal Decomposition of Ammonium Perchlorate

Abstract: The thermal decompositions of two kinds of NH 4ClO 4 (AP) with different grain size were investigated by DTA and TC-FTIR coupling. It is proposed that the decomposition of AP crystal obeys the process of “topochemistry ” and it is explained that there are two steps in the decomposition of the coarse grain size. On the basis of the gaseous products identified by real time and rapid scan FTIR and reported results in the literatures, the different mechanisms of the two steps during AP decomposition process are suggested.

An Overview of Combustion Mechanisms and Flame Structures for Advanced Solid Propellants

Abstract: Ammonium perchlorate (AP) and cyclotretamethylenetetranitramine (HMX) are two solid ingredients often used in modern solid propellants. Although these two ingredients have very similar burning rates as monopropellants, they lead to significantly different characteristics when combined with binders to form propellants. Part of the purpose of this paper is to relate the observed combustion characteristics to the postulated flame structures and mechanisms for AP and HMX propellants that apparently lead to these similarities and differences. For AP composite, the primary diffusion flame is more energetic than the monopropellant flame, leading to an increase in burning rate over the monopropellant rate. In contrast the HMX primary diffusion flame is less energetic than the HMX monopropellant flame and ultimately leads to a propellant rate significantly less than the monopropellant rate in composite propellants. During the past decade the search for more energetic propellants and more environmentally acceptable propellants is leading to the development of propellants based on ingredients other than AP and HMX. The objective of this paper is to utilize the more familiar combustion characteristics of AP and HMX containing propellants to project the combustion characteristics of propellants made up of more advanced ingredients. The principal conclusion reached is that most advanced ingredients appear to burn by combustion mechanisms similar to HMX containing propellants rather than AP propellants.

Experimental and modeling studies of two-dimensional ammonium perchlorate diffusion flames

Abstract: We investigated two-dimensional axisymmetric diffusion flames in which the surface decomposition products of ammonium perchlorate (AP) combustion provided the coflow for a methane fuel stream. The two-dimensional problem was solved using the fully elliptic formulation of the governing equations. By utilizing recent developments in hydrocarbon, chlorine, NO x , and AP kinetics, we formulated a detailed transport, finite rate chemistry system for the temperature, velocities, vorticity, and species mass fractions of the combined flame system. We compared the results of this model with a series of experimental measurements in which the temperature was measured with OH rotational population distribution, and the transient species OH, CN, and NH were measured with planar laser-induced fluorescence and emission spectroscopy. The kinetic mechanism, previously validated in one-dimensional experiments, was found to give good results in the two-dimensional model when compared with the experiments. The two-dimensional model can be used to understand the effects of solid propellant heterogeneity on combustion zone microstructure and the location and structure of heat release zones that control the propellant ballistic properties. It is a first step in developing computer codes that can a priori predict propellant ballistic behavior via modeling, thereby partially supplanting expensive physical formulation and testing.

Computational and experimental study of ammonium perchlorate/ethylene counterflow diffusion flames

Abstract: We investigated the modeling of counterflow diffusion flames in which the products of ammonium perchlorate (AP) combustion were counterflowed against an ethylene fuel stream The two-dimensional problem can be reduced to a one-dimensional boundary value problem along stagnation point stream-line through the introduction of a similarity transformation By utilizing recent developments in hydrocarbon, chlorine, NO x and AP kinetics, we formulated a detailed transport, finite-rate chemistry system for the temperature, velocity, and species mass fractions of the combined flame system A detailed soot model is included which can predict soot volume fractions as a function of the strain rate and the fuel mole fraction We compare the results of this model with a series of experimental measurements in which the temperature was measured with radiatin-corrected thermocouples and OH rotational population distribution: several important species were measured with planar laser-induced fluorescence, UV-visible absorption, and Raman spectroscopies: and the soot volume fraction was measured with laser-induced incandescence and visible absorption spectroscopy

Treatment of Groundwater Containing Perchlorate Using Biological Fluidized Bed Reactors with GAC or Sand Media

Abstract: Ammonium perchlorate has been used by NASA and the U.S. military as a component of solid rocket fuels. The formulation has a limited shelf life and replenishment is done by high pressure water flushing of old fuel followed by replacement with fresh supply as part of regularly scheduled maintenance activities. Past practice allowed the spent flush water to be discharged to the ground. As such, large volumes of ammonium perchlorate have been disposed in Nevada, California, Utah and likely other states since the 1950s.1 Ammonium perchlorate is very soluble in water (i.e., 20 g dL−1 at 25 °C) and dissociates completely to ammonium and perchlorate ions. The perchlorate ion is mobile in aqueous systems and can persist for decades under typical groundwater and surface water conditions due to its lack of reactivity with other compounds.1

Influences on Phytoremediation of Perchlorate-Contaminated Water

Abstract: Ammonium perchlorate is an oxygen-adding component in propellants for rockets, missiles and fireworks. To ensure that rockets and missiles operate effectively and safely, old propellant mixes must be continuously replaced in rockets and missiles with fresh supplies. High-pressure washout of solid propellant generates large volumes of perchlorate contaminated wastewater. Perchloric acid and perchlorate salts are also used extensively in many commercial and industrial processes, such as wet digestions, organic syntheses, and electropolishing of metals; animal feed additives, explosives, pyrotechnics, and herbicides. As a result, perchlorate manufacturers and users have disposed of large amounts of this chemical, since the 1950s. In addition, perchlorate has been found as a contaminant in certain fertilizers and bulk water treatment chemicals.1–2

2D model for unsteady burning heterogeneous AP/binder solid propellants

Abstract: The burning of a periodic sandwich of the solid oxidizer, ammonium perchlorate (A) and solid fuel, HTPB is modeled by considering two-dimensional energy balances in both the solid and gas phases, two-dimensional gas species concentration, considering a reduced chemistry model for three global reactions and eight chemical species. Full heat coupling between the solid and gas phase allows the prediction of the AP, binder, and average regression rates. Flame structure including the AP decomposition flame and the diffusion flames with the binder are predicted to occur within regions ranging from 10 jjm to 200 um. Solutions are presented for various AP/binder ratios, at solid rocket pressures, ranging from 40-100 atm. Parametric studies identify the sensitivity of the burning rates to the chemical kinetics constants and the pyrolysis relations, as well as the solid-phase heat exchange coefficient, as.

Long-Term Release of Perchlorate as a Potential Source of Groundwater Contamination

Abstract: Recently, perchlorate has been found at appreciable levels in the drinking water supplies of California and other southwestern states.1 Water suppliers have detected concentrations at part per billion levels, but some have found concentrations as high as 280 μg L−1. Perchlorate has also been detected in Lake Mead and the Colorado River at ppb levels. The source of the perchlorate ion is the salt, ammonium perchlorate, which is used predominately as an oxidizer in solid rocket fuel and fireworks. Perchlorate has been released to the environment from manufacturing facilities and solid rocket booster testing and maintenance sites. Perchlorate has also been reported in certain fertilizers at concentrations up to 0.84 % w/w.2

Nanostructured energetic materials derived from sol-gel chemistry

Abstract: Initiation and detonation properties are dramatically affected by an energetic material's microstructural properties. Sol-gel chemistry allows intimacy of mixing to be controlled and dramatically improved over existing methodologies. One material goal is to create very high power energetic materials which also have high energy densities. Using sol-gel chemistry we have made a nanostructured composite energetic material. Here a solid skeleton of fuel, based on resorcinol-formaldehyde, has nanocrystalline ammonium perchlorate, the oxidizer, trapped within its pores. At optimum stoichiometry it has approximately the energy density of HMX. Transmission electron microscopy indicated no ammonium perchlorate crystallites larger than 20 nm while near-edge soft x-ray absorption microscopy showed that nitrogen was uniformly distributed, at least on the scale of less than 80 nm. Small-angle neutron scattering studies were conducted on the material. Those results were consistent with historical ones for this class of nanostructured materials. The average skeletal primary particle size was on the order of 2.7 nm, while the nanocomposite showed the growth of small 1 nm size crystals of ammonium perchlorate with some clustering to form particles greater than 10 nm.

Three-dimensional flames supported by heterogeneous propellants

Abstract: We examine a surface which mimics that of a heterogeneous propellant and through which passes distributed fluxes of oxidizer and fuel. The three-dimensional flames supported by these fluxes we calculated using a simple model. An elementary propellant packing model defines a variety of flux distributions according to the level of the slice through the propellant which defines the surface, and the effect of the different distributions on the combustion field and on the heat flux to the surface is discussed. An important geometric effect is identified. The more likely that arbitrary surface area fractions contain both ammonium perchlorate (AI) and binder fluxes, the greater will be the total heat flux to the surface from the AP/binder flames. The likelihood, and therefore the heat flux, is maximized for fuel-rich slices. This work is part of an ongoing study whose goal is a sophisticated numerical model of three-dimensional heterogeneous propellant burning.

A computer model of flamelet distribution on the burning surface of a composite solid propellant

Abstract: The paper attempts to obtain an approximate distribution of oxidizer/fuel (O/F) flamelets on the burning surface of a composite solid propellant, mainly of the ammonium perchlorate (AP)-hydrocarbon (HC) binder variety commonly used in rocket propulsion applications today. A computer model is developed to simulate the random packing of oxidizer particles of different size distributions in the propellant. The focus of the present work is on the distinction between pockets of fine AP particles amidst the binder that may bum in a premixed O/F flame and the sufficiently large AP particles that bum with the surrounding vapor flow in an attached diffusion flame. A transition occurs between premixed burning and attached diffusion flamelet-burning over each oxidizer particle as the ambient pressure is varied. A simple criterion evolved earlier to delineate the two regimes of burning in the particle size-pressure domain has been employed to determine the flamelet type that prevails over each exposed particle of the...

Ignition and combustion of ammonium perchlorate in a hydrogen atmosphere

Abstract: In the view to using ammonium perchlorate (AP) as an oxidizer in a hydrogen-breathing combustion engine in the Jupiter atmosphere, a fundamental study was performed experimentally on the ignition and combustion of a lump of AP in a hydrogen atmosphere. AP was found to ignite just after decomposition. The burning AP had a decomposition flame adjacent to the AP surface, and a flame of light-violet and orange color attributed to OH, ClO, and H2O emissions developed in the gas phase surrounding the decomposition flame. During combustion, the burning rate followed the same d2 law as that for liquid fuel droplets. The measured emission intensity distributions of OH, ClO and H2O showed that OH had a peak concentration away from the AP surface, and ClO was generated near the surface. The flame location was much closer to the AP surface in comparison with those of various hydrocarbon fuels in air, which was explained in terms of the large mass ratio of the stoichiometric oxidizer to fuel. To elucidate the combustion process of AP in an H2 atmosphere, the flame structure in the gas phase was calculated assuming that the oxidizing gases produced by an AP decomposition flame react with hydrogen and using a detailed gas-phase kinetic mechanism. The calculation results were compared with the measured emission intensity distributions.

Surface layer dynamics in the pyrolysis of ammonium perchlorate-hydrocarbon binder propellants

Abstract: Mixtures of ammonium perchlorate particles and polybutadiene binder appear to exhibit preferential accumulation of one or the other component on the pyrolyzing surface over a range of rocket-operating pressures. At low pressures, the surface layer is enriched with the oxidizer, and at high pressures, it is enriched with the binder. The degree of accumulation of the oxidizer is found to be higher for smaller particle size. These experimental data can be explained by the difference in activation energies for pyrolysis of the oxidizer and the binder. The particle size effect is explained by consideration of nearly identical surface temperatures for the oxidizer and binder in mixtures with fine particles, but different temperatures for those with coarse particles. The results obtained are important to the explanation of the mechanism of plateau burning rate exhibited by certain composite propellants.

Burning Behavior of Composite Propellants with Fast-Burning Inclusions.

Abstract: The combustion characteristics of ammonium perchlorate-based composite propellants containing granulated fastburning energetic materials (FBEM) of different particle sizes have been studied in a constant-pressure bomb and combustion mechanism has been proposed. The use of FBEM of large particle size has been shown to allow not only a considerable increase in the burning rate, but also modification of the burning rate-pressure dependence.

Perchlorate Analysis with the AS16 Separation Column

Abstract: Perchlorate is a powerful oxidant used in solid-rocket propellant mixtures, fireworks, and munitions. The presence of trace level perchlorate in drinking water poses a potential health risk, resulting from perchlorate’s ability to interfere with the thyroid gland’s uptake of iodide to produce thyroid hormones. The current EPA’s recommended acceptable level for perchlorate in drinking water is 18 parts per billion (ppb). Since perchlorate is better known for it’s commercial and industrial applications, past occurrence studies have focused on water wells near regions where munitions, aerospace components, and fireworks were manufactured, developed and tested. Perchlorate has been reported in drinking water sources in the states of California, Utah, Nevada, West Virginia, and Texas.1–6 However, recent reports have suggested that naturally occurring perchlorate is also present in fertilizers, nitrate deposits from northern Chile, and minerals from arid environments. These new findings have sparked intense efforts in the study of natural perchlorate occurrence in non-aqueous matrices, and in the development of new methodologies to support these studies.

Gas generator composition for pretensioner

Abstract: PROBLEM TO BE SOLVED: To provide a gas generator composition for pretensioner excellent in ignitability at the initial stage of combustion without generating non- combustibles and also substantially carbon monoxide and hydrogen chloride, and having good moldability. SOLUTION: This gas generator composition for pretensioner includes, as essential components, (A) ammonium perchlorate, (B) a chlorine remover for removing a chlorine-containing derivative generated from ammonium perchlorate, (C) nitrocellulose having 11.7-13.4% nitrogen content and (D) a stabilizer for improving the composition stability with the lapse of time. COPYRIGHT: (C)2002,JPO

Effect of the duration of the front edge of the voltage pulse on the electric breakdown of ammonium perchlorate

Abstract: The results of a study of the effect of the front edge duration of a voltage pulse (τ) on the electric breakdown of ammonium perchlorate single crystals are submitted. Experiments have shown that at τ 1.5 µs. It is shown that the electric breakdown of ammonium perchlorate results from an impact generation of electrons. The impact generation rate of electrons versus electric field and the diameter of the through channel being formed during electric breakdown in ammonium perchlorate are estimated.

Method for biologically cleaning water containing ammonium perchlorate

Abstract: PROBLEM TO BE SOLVED: To remove both perchlorate ion and ammonium ion and to convert ammonium ion to nitrogen molecule with a simple and economical method. SOLUTION: An ammonium perchlorate aq. solution is brought into contact with activated sludge containing nitrification microorganisms in the presence of at least a source of an inorganic carbon and nutrients for the metabolism of the microorganisms in a 1st aerobic reactor and next, a liquid flowing out from the 1st reactor is brought into contact with the activated sludge containing the denitrification microorganisms and perchlorate ion reducing microorganisms in the presence of at least a source of an organic carbon and the nutrients for the metabolism of the microorganisms.

Effect of Preparation Conditions of Titanium Oxide on Dinitrogen Fixation to Ammonium Salt

Abstract: Dinitrogen fixation to solid needles of ammonium perchlorate was found to occur upon white light irradiation to composite systems of poly(3-methylthiophene) and titanium oxides (native, thermally-grown, and sputtered oxides) under ambient conditions of temperature and pressure.

Preparation of Composite Nanometer sized Particle(II)

Abstract: Copper oxide is a kind of catalyst that accelerates the decomposition of ammonium perchlorate. The conglobation easily occurred when ultra fine ammonium perchlorate and copper oxide were mixed in the past, and so it hadn't optimum effect on the decomposition of ammonium perchlorate. First we apply the method of spray pyrolysis to the preparation of nanometer copper oxide and then use energetic ball milling method to make nano sized copper oxide embeded in the crystalloid surface of ammonium perchlorate to form compound particle. We have preferably settled the problem. Nano sized copper oxide is uniformly scattered in compound particles. Because nano sized copper oxide is possessed of large specific area in the nature of high chemical activity, it greatly enhences catalysis effect on ammonium perchlorate and results in more derastic thermolytic dissociation.

Combustion Mechanisms of Heterogeneous Solid Propellants

Abstract: : The bulk of the research on this contract was concerned with the mechanisms that cause plateau burning of ammonium perchlorate/hydrocarbon (AP/HC) propellants. The long range goal is to identify the steps in the combustion process that dominate overall burning, and in particular to understand which of these steps in the combustion process lead to plateau burning. Burning alone, matrixes (mixture of binder, fine AP, and catalysts) almost always burn slower than the bimodal propellant at all pressures. The improved burning with a catalyst is probably due to both increased surface layer heat release and to catalytic break down of the large fuel vapor molecules which cause the flame to stand closer to the surface. Deflagration rate of the large AP particles is always lower than the propellant rate, and contributes little to overall rate, except in close proximity to the matrix where a hot stoichiometric diffusion flame occurs and (apparently) supports the marginal matrix burning, accounting for the higher propellant rate. Observations of local intermittency of burning seem to contribute to the low burning rate associated with plateaus and spontaneous quenches.

The Role of Boron in Thermal Decomposition of Ammonium Perchlorate

Abstract: Simultaneous thermal analysis (STA) method has been applied to study decomposition reactions of AP under a flowing nitrogen atmosphere and static air. Results obtained indicate that a phase transformation occurs prior to the decomposition reaction. Decomposition takes place exothermally in two stages, first stage of decomposition could be suppressed by the controlled heating programme. Addition of a small amount of born lowered the temperature of the exotherm and increased the overall enthalpy of reactions.