Conversion of fuels containing nitrogen to oxides of nitrogen in hydrogen and methane flames

Nitrogen-containing compounds such as hydrogen cyanide, acetonitrile, acrylonitrile, pyridine, benzonitrile, ammonia and methylamine, which are typical of the products likely to be encountered during the decomposition of nitrogen-containing polymers in fires, have been introduced into hydrogen and methane flames burning in oxygen-argon atmospheres. There is a complete conversion of fuel nitrogen in all cases to oxides of nitrogen and molecular nitrogen. The relative conversion to oxides of nitrogen (as NO_x/N₂) increases as the injection rate of nitrogen-containing fuels is decreased. The relative yields of oxides of nitrogen tend to be similar with methane and hydrogen premixed flames and markedly greater than observed with hydrogen diffusion flame. In all cases the yield of oxides of nitrogen-containing products such as hydrogen cyanide can also present a toxic risk during the burning of nitrogen-containing polymers, particularly when high temperature are involved. The combustion of these products in flame zones cannot be assumed to alleviate the additional toxic risk because of their conversion to oxides of nitrogen.     

Lead Free Ammunition without Toxic Propellant Gases

Environmental and health considerations have encouraged the development of ammunition with substitutes for lead and other heavy metals. In general, the emission products from munitions containing nitro‐based propellants are highly complex mixtures of gases, vapors, and solid particles. The major combustion products are H₂O, CO, CO₂, H₂, and N₂. In addition, compounds including hydrogen cyanide (HCN), ammonia (NH₃), methane (CH₄), nitrogen oxides, benzene, acrylonitrile, toluene, furan, aromatic amines, benzopyrene, and various polycyclic aromatic hydrocarbons are detected in minor concentrations. Many of the identified chemical species have severe toxicological properties, and some of the compounds do even have mutagenic effects. Gun smoke emission is a concern because its exposure to humans may be substantial during military and civilian police training, as respiratory protection equipment is not routinely worn. In this work we study the compositions of some of the main decomposition products, experimentally as well as theoretically. The concept of frozen equilibrium at around 1500–2000 K appears to apply for CO, CO₂, and H₂. However, the trace species in the combustion mixtures appear theoretically to be present in negligible concentrations. Our measured results are many orders of magnitude higher than theoretical results in open space. We forecast that future development of gun powder will focus on reducing the amount of toxic trace species.     

龙格氮量计法测定火药中硝化棉含氮量

火药能量的大小与硝化棉含氮量的高低有着直接关系。硝化棉是火药中的主要能量来源之一。由于火药在贮存过程中的不断分解,使硝化棉含氮量逐渐减少,能量下降,机械强度降低和弹道性能变坏,用龙格氮量计法测定库存火药中硝化棉的含氮量具有重要意义。     

Evolution of toxic gases from heated plastics

A brief investigation has been carried out into the nature and quantity of the toxic gases evolved during the thermal decomposition of polyurethane, urea-formaldehyde, nylon and acrylonitrile in air and in nitrogen. The weight fractions of the polymers evolved as hydrogen cyanide are given, together with the lowest temperatures at which hydrogen cyanide, carbon monoxide, ammonia and nitrogen oxides are evolved. Apparent activation energies for the evolution of hydrogen cyanide and carbon monoxide have been determined. A brief discussion of the experimental data is given.     

Interaction of a phosphorus‐based FR,a nanoclay and PA6. Part 2 interaction of the complete PA6 polymer nanocomposites

Polyamide 6 (PA6) is modified with a nanoclay (NC), Cloisite 30B and/or a flame retardant (FR), OP1311. The thermal decomposition of pure PA6 and PA6 nanocomposites is done by thermogravimetric analysis (TGA). The decomposition products from TGA in nitrogen and air are analysed online by Fourier transform infrared (FTIR) spectroscopy in order to examine the time/temperature‐dependent thermal degradation processes and monitor the evolved gases online. The profiles of the evolved gases are compared with ε‐caprolactam spectra, which are the main species in the gas phase. Results show that the addition of the fire retardant decreases the degradation temperature, whereas the incorporation of NC (PA6+NC) contributes to increased residual mass and char formation. The evolved gases from TGA‐FTIR in nitrogen from pure PA6 and (PA6+NC) are hydrocarbons, carbon dioxide, water, ε‐caprolactam and ammonia. The (PA6+FR) and (PA6+NC+FR) evolve the same volatiles with an additional phosphorus‐containing species, namely diethylphosphinic acid. The thermo‐oxidative degradation of all these composites in air yields carbon monoxide with an increased production of carbon dioxide, water and hydrogen cyanide. Another important result is that the hydrogen cyanide does not increase when the phosphinate FR is used. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of temperature,catalyst and charge gas on the mean chemical structures of the products from hydrogenation of Liddell coal

Liddell coal (New South Wales, Australia) has been hydrogenated at 400, 425 and 450 °C with excess tetralin as vehicle and nitrogen or hydrogen as charge gas for 4 h at reaction temperature. In some experiments a nickel-molybdenum catalyst was used. The structures of the liquid and solid products were investigated by nuclear magnetic resonance spectroscopy, gel permeation chromatography and combustion analysis. Increasing the hydrogenation temperature from 400 to 450 °C decreases the yield of liquid products but increases conversion. At higher temperatures the liquid products are smaller in molecular size and molecular weight and contain a greater proportion of aromatic carbon and hydrogen; the solid residues also contain a greater proportion of aromatic carbon. The changes in variation of yield and structure with temperature are independent of the presence of catalyst under nitrogen and the nature of the charge gas. However, as the reaction system is capable of absorbing more hydrogen than can be supplied by the tetralin, the products from reactions with hydrogen as charge gas contain more hydrogen, some in hydroaromatic groups. Catalyst has little, if any, role in dissolution of the coal when a nitrogen atmosphere is used. When nitrogen is used as charge gas, reactions of coal-derived liquids with the catalyst do not alter the hydrogen, carbon or molecular size distributions in the products. The results show that the changes in composition of the liquid and solid products with increase in hydrogenation temperature are due to pyrolytic reactions and not to increased hydrogenation of aromatic rings.     

Reactions of fuel-nitrogen compounds under conditions of inert pyrolysis

As part of a study of the chemical mechanisms involved in the conversion of fuel-nitrogen compounds to nitric oxide during combustion, fossil fuels and model nitrogen compounds were pyrolysed in helium in a small quartz flow reactor. Hydrogen cyanide was the major nitrogen-containing product obtained in all cases indicating that hydrogen cyanide is formed during the initial pre-flame stages of combustion and is the principal intermediate in the formation of fuel nitric oxide. At a nominal residence time of one second, 50% decomposition of pyrrole, quinoline, benzonitrile and pyridine occurs at 905, 910, 922 and 954 °C, respectively. The fraction of the nitrogen in pyridine that is converted to hydrogen cyanide increases from 40% at 960 °C to 100% at 1100 °C. Benzonitrile produces similar amounts of hydrogen cyanide (49 and 82%). The hydrogen cyanide yields from coals and residual fuel oils increase from the range of 15–25% at 950 °C to 23–42% at 1100 °C. It is not possible to determine from these single-stage experiments if most of the hydrogen cyanide forms in the primary pyrolysis process or in secondary reactions.     

HCN synthesis from methane and ammonia over platinum

The mechanism of the HCN formation from ammonia and methane over Pt black was investigated using a temporal analysis of products (TAPs) reactor system. At 1173 K the hydrogen cyanide production rate depends on the order of introducing the reactants. HCN is formed rapidly on the methane pulse just after introducing ammonia. However, a slow formation of HCN is observed on the ammonia pulse that follows a methane pulse. Moreover the form of the HCN response resembles closely that of the nitrogen and hydrogen also released during the ammonia pulse. Thus, the rate-determining step for the formation of HCN is the decomposition rate of ammonia. A reaction sequence based on elementary steps is proposed for the HCN synthesis. The formation of HCN after pulsing H₂ points to a pool of surface intermediate species that are hydrogenated to HCN.     

Reactions of coal with discharge-generated (excited) nitrogen species

Reaction between coal and nitrogen in a discharge furnishes hydrogen cyanide and smaller amounts of cyanogen, as well as some carbon monoxide and carbon dioxide; the cumulative yields of hydrogen cyanide and cyanogen depend upon rank. The apparent activation energies for formation of hydrogen cyanide and cyanogen are in the order of 2–4 kcal mol⁻¹ but increase sharply to ≈13–14 kcal mol⁻¹ at ≈200 °C (possibly coincident with incipient thermal decomposition of the coal). The cyanogen/hydrogen cyanide ratio increases with rank, and also depends upon the reaction temperature — falling with increasing temperature up to ≈200 °C, and thereafter rising progressively. Rate measurements and i.r. spectral changes accompanying the reaction suggest that hydrogen cyanide is mainly formed from non-aromatic carbon-hydrogen configurations in the coal, and that cyanogen derives for the most part from aromatic carbon — though some can also be generated from non-aromatic CH in competition with formation of hydrogen cyanide.     

Interaction of carbonaceous materials with gunpowder gases

Conclusions We have investigated the completeness of the interaction of various carbonaceous materials with gunpowder gases in the ballistite gunpowder combustion wave. We have shown that the limit in the carbonaceous material content, above which a change occurs in the interaction of the CM with the gunpowder combustion products, depends on the material's specific surface and is independent of the oxidizer-excess coefficient of the gunpowder.For the highly dispersed (200–250 m²/g) materials (carbon fiber and KGO-250 carbon black) this limit is about 50% of the thermodynamic value, which equals 10% for the gunpowder N (=0.55) and 17% for gunpowder A (=0.72), while for the carbon black PM-15, which has a lower specific surface (15 m²/g) it is about 30%.The incomplete combustion is explained by the presence of kinetic impediments in the interaction of the carbon with carbon dioxide and water.Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 25, No. 4, pp. 25–32, July–August, 1989.     

Utilization of New Non‐toxic Substances as Stabilizers for Nitrocellulose‐Based Propellants

Propellants consisting of nitrocellulose (NC) and/or other nitrate esters are inherently chemically unstable and undergo decomposition even under standard storage conditions. Decomposition of such compounds can be inhibited or nearly stopped when stabilizers are used. However, conventional stabilizers form nitrosamines that have toxic and carcinogenic effects. As a result, these conventional stabilizers should be replaced as soon as possible. A series of NC‐based propellants doped with different novel manufactured stabilizers were investigated using microcalorimetry, conventional stability tests, and sensitivity tests. The results were compared with propellants containing the conventional stabilizer Akardite II. The chemical structure of these new stabilizers and their decomposition products do not enable the formation of toxic N‐nitrosamines.     

Research progress of microbial decomposition of nitroglycerine and nitrocellulose

硝酸酯类物质（如硝化甘油和硝化棉等）是有机羟基基团与硝酸缩合的产物,在军事工业上有非常广泛的用途。由于它们并非天然存在的物质,且有爆炸等潜在危害,故不能直接排放到环境中。作为地球生物化学循环中分解者的微生物对硝酸酯类物质的生物降解起着很大的作用,本文将对硝化甘油和硝化棉的生物降解研究进展进行综述。     

Reactions of coal with nitrogen/ hydrogen mixtures in a discharge

In-discharge reaction of coal with nitrogen/hydrogen mixtures rather than nitrogen alone raises rates of hydrogen cyanide generation by a factor of 10–50, and makes hydrogen cyanide account for ≈70–90% of the total product-gas volume. From these results and parallel tests with a pure carbon, it is concluded that enhanced formation of hydrogen cyanide is controlled by transient hydrogenation of aromatic carbon and consequent creation of additional (non-aromatic) reaction centres which can be abstracted by N^*.     

Decomposition products of PVC for studies of fires

Approximately seventy-five organic materials have been detected by gas chromatography in the thermal decomposition products of PVC and are shown by mass spectrometry and retention studies to consist mainly of aromatic and aliphatic hydrocarbons. Weight-loss experiments and time-resolved chromatography indicate that these products are formed mainly during dehydrochlorination. The products are modified by the presence of oxygen but no oxygenated organic species have been detected. Experiments to specifically monitor the production of phosgene from the decomposition of both a rigid PVC sheet and a PVC polymer in air are recorded. Phosgene has not been detected and direct seeding techniques have been used to investigate the detection limits of this material. PVC is known to release the toxic gases, carbon monoxide and hydrogen chloride, when involved in fires. It is shown that the minor products, including phosgene, make little or no contribution to the overall toxicity of the decomposition products.     

Composition of gaseous combustion products of polymers

The gaseous products generated by the flaming combustion of ten kinds of synthetic polymers and a kind of wood (cedar) under the same conditions (sample weight, 0.1 g; temperature, 700°C air flow rates, 50 and 100 l./hr) were quantitatively analyzed by infrared spectrophotometry, gas chromatography, and colorimetric tube method. The main hydrocarbons generated were methane, ethylene, and acetylene. The amount of acetylene generated by the flaming combustion of polymers was much larger than the amount of acetylene formed by pyrolysis at 700°C in nitrogen. Acetylene increased in quantity with increasing air. For nitrogen compounds, hydrogen cyanide was generated from every polymer containing nitrogen used, but ammonia was detected only for nylon 66 and polyacrylamide. Nitrogen monoxide and nitrogen dioxide were detected only in small amounts. Nitrous oxide was detected in the gaseous products generated by the nonflaming combustion of urea resin and melamin resin. It was also found that about 70% of the nitrogen in N-66 and PAA was converted into nitrogen gas (N₂) by combustion under the conditions described above.     

Nitrogen-containing products from the thermal decomposition of flexible polyurethane foams

The thermal decomposition of a polyester and a polyether flexible foam in a nitrogen atmosphere has been studied by gas chromatography, mass spec-trometry and elemental ultramicroanalysis. It is shown that the decomposition behaviours of the two foams are similar. At low temperatures (200 to 300 °C) there is a rapid and complete loss of the tolylene diisocyanate unit of each foam as a volatile yellow smoke leaving a polyol residue. The smoke has been isolated as a yellow solid (common to both foams) which contains virtually all of the nitrogen of the original foams and, under the conditions of test, is stable at temperatures up to 750 °C. Nitrogen-containing products of low molecular weight (mainly hydrogen cyanide, acetonitrile, acrylonitrile, pyridine and benzonitrile) observed during the high temperature decomposition (over 800 °C) of the foams are shown to be derived from the yellow smokes. At 1000 °C, approximately 70% of the available nitrogen has been recovered as hydrogen cyanide.     

Interferences in the determination of nitrogen dioxide in a chemiluminescent analyser

A commercial chemiluminescent nitrogen oxides analyzer performed well in its nitric oxide mode when applied to the combustion products of polyurethane materials, but when test gases were passed through a thermal converter prior to measurement of nitrogen dioxide, serious, interferences was encountered from hydrogen cyanide and other nitrogen compounds.     

Thermogravimetric and qualitative analysis of thermal decomposition characteristics of polyurethane foams based on polyols with carbamide or oxamide and borate groups

The thermal stability and the kinds of products of thermal decomposition of polyurethane foams modified with urea or oxamide and borate groups were studied. Incorporation of urea or oxamide groups and borate groups enhances the thermal stability of polyurethane foams compared to polyurethane foams based on typical polyols. Thermal stability of foams modified with oxamide groups is somewhat higher that of foams modified with urea groups. In turn, simultaneous incorporation of borate groups results in an increase in thermal stability of the foams modified with urea. The temperature of thermal decomposition of the foams with oxamide and borate groups does not change or undergoes a slight decrease. The thermal degradation products of investigated foams are similar and they are usually water, ammonia, carbon dioxide and/or nitrous oxide. Additionally, hydrogen cyanide can be released during thermal decomposition of polyurethane foams modified with urea groups. The presence of borate groups prevents the formation of hydrogen cyanide. The opposite situation is observed in the case of the foams modified with oxamide and borate groups. Thus, from the point of view of a fire hazard, the use of the foams modified with urea and borate groups is safer. © 2017 Society of Chemical Industry     

Solution combustion synthesis of metal nanopowders: Nickel—Reaction pathways

Nanopowders of pure nickel were directly synthesized for the first time by conventional solution combustion synthesis (SCS) method. In this article, a specific reaction pathway is suggested to describe the metallic phase formation during SCS. It is proposed that the exothermic reaction between NH₃ and HNO₃ species formed during the decomposition of glycine and nickel nitrate acts as the source of energy required to achieve the self‐sustained reaction regime. A thermodynamic analysis of the combustion synthesis reaction indicates that increasing glycine concentration leads to establishing a hydrogen rich reducing environment in the combustion wave that in turn results in the formation of pure metals and metal alloys. TGA of reaction systems and XRD analysis of products in the quenched combustion wave show that the formation of oxide phases occurs in the reaction front, followed by gradual reduction of oxide to pure metallic phases in the postcombustion zone. A methodology for SCS of pure metals and metal alloys nanoparticles can be inferred from the results presented. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Reaction of coal with nitrogen in a microwave discharge

In a microwave discharge in nitrogen, high-volatile bituminous coal produces gaseous products, namely hydrogen cyanide, acetylene, small amounts of cyanogen and lowmolecular-weight hydrocarbon gases, and nitrogen-containing compounds, in addition to the usual hydrogen and carbon oxides. The reaction of coal in the nitrogen discharge occurs in two stages: interaction of active nitrogen with the coal molecule to cause rapid volatilization of gaseous products, and slow gasification of residual char by active nitrogen. Various factors influencing product type, yield, and distribution are examined. Under conditions where the gaseous products can be quickly quenched or removed, as by trapping at a very low temperature, more than 42% of carbon in the coal can be converted mainly to hydrogen cyanide and acetylene, which together constitute about 90% of the total products.