Experimental study of ignition of magnesium powder by electrostatic discharge (original) (raw)
Related papers
International Journal of Heat and Mass Transfer, 2006
A methodology for investigating and quantifying the thermal processes leading to ignition of rapidly heated metal powders was developed. The simple experiment involves observing ignition of a powder coated on the surface of an electrically heated filament and is well suited for a variety of powdered fuels. In an experimental case study, the ignition temperature of spherical Mg powder was detected optically at different heating rates. To interpret the results, a heat transfer model was developed for a multilayer powder coating on the heated cylindrical filament. The thermal contact resistance between particles was determined from the measured bulk thermal diffusivity of the powder considering the experimental particle size distribution. An Arrhenius type expression was used to describe the exothermic chemical processes leading to ignition with the pre-exponent as an adjustable parameter. For Mg, a pre-exponent value identified by matching the calculations with the experimental data was found to be 10 10 kg/m 2 s. The match between the experimental and predicted temperatures and times of ignition was good for different heating rates, which validated the proposed heat transfer model and indicated that the developed methodology is practically useful.
Determination of Ignition Sensitivity of Selected Heat Powders
Ignition sensitivity is one of the factors defining the characteristics of high calorific mixture with low emission of gaseous product. It was found that Zr-BaCrO4 mixture is sensitive to ignition by electric spark energy of 0.82 J, whereas activation of Fe-KClO4 mixture depends on the iron powder employed and the composition of its surface oxide layers. Energy required for the activation of high calorific mixture in form of powder designated as FeK, FeR or FeE is equal to 0.08, 0.59 and 1.1 J, while in the form of pellet 6.92, 10.2 and 14.1 J. Activation of Fe-KClO4 mixture with a strip of heat paper as well as with the electric spark has revealed that the mixture containing iron powder obtained by atomization method (FeA) is not active.
An electrostatic suspension method for testing spark breakdown, ignition, and quenching of powders
Journal of Electrostatics, 1996
An innovative electrostatic suspension method, referred to as EPS (electrostatic particulate suspension), is used for testing the spark breakdown, ignition, and quenching characteristics of small volume powder suspensions. A highly uniform steady-state suspension is generated between high voltage dc parallel plate electrodes that can be ignited with a spark discharge from a high-speed, moving electrode or by pulse discharge from a Ruby or YAG laser. The design methodology and characteristic suspension times are reviewed. Bulk powder resistivities < 109 f~ m are recommended for generating a suspension. With cohesive powders such as fine coal it may be necessary to augment the EPS method with acoustic vibration. To demonstrate the utility of the EPS method, representative data for coal, aluminum, and copper powders are presented. Specific results are discussed in the following studies: (I1 Spark breakdown of a (inert) copper powder in air, (1I) Minimum i qnition enerqy ~MIE) q[ aluminum-oxygen-nitrogen/carbon dioxide mixtures at near-quenching conditions, (III) Wall quenching of coal-air and aluminum-air mixtures, and (IV) Inert particle quenching u irh copper particle propane-air mixtures.
Journal of Hazardous Materials, 2006
All explosives, under all conditions must be considered vulnerable to generation, accumulation and discharge of static charge. The low energy static hazards of the order as low as 2-3 mJ need to be guarded against in case of highly sensitive compounds namely primary explosives. The hazard is normally associated with manufacturing and filling operations due to discharge of static charge accumulated on a person supplying energy up to 20 mJ. To reduce the risk associated with static initiation hazard in the processing and handling of the explosives, the electrostatic sensitivity tests can provide an important input regarding electrostatic hazards. This paper presents electrostatic sensitivity data in terms of zero ignition probability data (E SE0) of some of the initiatory explosives such as nickel/cobalt hydrazinium nitrate, silver azide, lead azide and mercury salt of 5-nitro tetrazole. Similar data has also been presented for samples coated with polyvinyl pyrrolidone to study its effect on electrostatic sensitivity. The electrostatic spark sensitivity of some conventional and novel made to explain the increased spark sensitivity behavior on the basis of the possible primary explosives has been studied. The electrostatic spark sensitivity of primary explosives decreased in the order of AgN 3 = NHN > PbN 6 > MNT > CoHN > BNCP. A possible correlation of spark energy with approximation and assumption has been drawn with thermal, detonation and mechanical properties. The polyvinyl pyrrolidone coated samples followed the same order but interestingly with increased spark sensitivity. An attempt has been reasoning of dielectric nature of the materials or exothermic effects of decomposition products of PVP. The present work also reports the electrostatic spark sensitivity of cap compositions.
Sensitivity to ignition by electrostatic discharge of explosive dust / air
MATEC Web of Conferences
In industrial sectors that use, process, transport or store, substances such as combustible dusts could exist some workplaces with explosion hazard due to the possibility of dust/air explosive formation and ignition, both inside the installations and in the surrounding atmosphere. Methods and means of protection aim to prevent the development of explosive atmospheres, followed by preventing the occurrence of ignition sources and then limiting the effects of explosions. To assess the risk of ignition of the explosive atmosphere, there must be known first of all, the explosive atmosphere’s sensitivity to ignition by electrostatic discharge, respectively, the minimum ignition energy of the explosive mixture, afterwards being required an analysis on the possibilities of formation and discharge of electrostatic charge. For the most common combustible dusts, the minimum ignition energy is given, but for new types of flammable substances this parameter defining the sensitivity to ignition ...
Experimental study of spark-discharge initiation of detonation
Journal of Engineering Physics and Thermophysics, 2013
The mechanisms of action on a high-current spark discharge that make it possible to reduce the total expenditure of electric energy on initiating detonation have been proposed. The action is based on the control of a discharge current with the aid of an external circuit and on the addition of easily ionizable admixtures to a fuel-oxygen mixture. Results of experimental investigations into the spark-discharge initiation of detonation with the action on the discharge process have been presented; the results were obtained in mixtures of hydrogen with oxygen and of commercial propane-butane with oxygen at atmospheric pressure.
A theoretical study of the ignition of a reactive medium by means of an electrical discharge
Combustion and Flame, 1985
A mathematical model is presented to simulate the evolution with time of a short segment of a spark channel in a methane-air mixture. The model assumes an axisymmetric cylindrical flame propagation and conducting column with moving boundaries in which local thermodynamic equilibrium exists at every point. The phenomena associated with the breakdown phase are considered as initial conditions. These are based on the experimental observations of other investigators. The radial profile of the time-dependent electrical energy input during the arc phase is determined by the computed plasma conductivity. The model employs a realistic equation of state, experimental transport coefficients at high temperatures, measured data for the mean emission coefficient for heat radiation, and a detailed chemical kinetics of a CH4-air system. The evolution with time of the conductivity channel and the associated flow, temperature, and concentration fields are calculated by numerical integration of the relevant conservation equations in the one-dimensional Lagrangian coordinates.
Synthesizing aluminum particles towards controlling electrostatic discharge ignition sensitivity
Journal of Electrostatics, 2014
Aluminum particles were synthesized with shell thicknesses ranging from 2.7 to 8.3 nm and a constant diameter of 95 nm. These fuel particles were combined with molybdenum trioxide particles and the electrostatic discharge (ESD) sensitivity of the mixture was measured. Results show ignition delay increased as the alumina shell thickness increased. These results correlated with electrical resistivity measurements of the mixture which increased with alumina concentration. A model was developed using COMSOL for ignition of a single Al particle. The ignition delay in the model was consistent with the experimental results suggesting that the primary ESD ignition mechanism is joule heating.
368350 Oxidation of Mg Powders: Implications for Ignition and Aging
Magnesium is widely used in pyrotechnic formulations; it is also a component of reactive alloys, e.g., Al-Mg and B-Mg, which are potential fuels for explosives and propellants. Despite its widespread applications, kinetics of oxidation of Mg powders are not well quantified. As was recently shown for Al, such kinetics are of fundamental importance for the models aimed to describe thermally induced ignition of metal powders. In addition, for Mg the issue of aging is important because its oxide, MgO, layer lacks protective properties typical of Al2O3. In this work, mechanisms of the magnesium oxidation by both oxygen and steam were studied by thermo-gravimetric measurements for micron-sized spherical powders. Two magnesium powders with different but overlapping particle size distributions were used. The experimental results were interpreted taking into account the measured particle size distributions, and considering different assumptions for the location of the reaction interface. Whe...