Method of comprehensive assessment of efficiency of decrease of fire and explosion risk of coal suspended particles

Methods and results of experimental study of explosive and wetting characteristics of coal dust are presented. Modified evaluation method of explosive characteristics of coal dust allows estimating critical concentrations of suspended dust at variation of temperature of ionizing ignition source corresponding to beginning of flame propagation by means of approximation method. Method of measuring the contact angle of particles of coal powder is based on visualization of the drop placed on the pressed coal

Investigation of Igniting Ability of Heterogeneous Systems by Means of Electric Spark

The article presents a physical model for determining the boundary conditions of ignition of a heterogeneous system, taking into account the heating of the liquid phase and its evaporation. The temperature distribution in a heterogeneous system is described by the obtained analytical expression. An algorithm describing the evaporation rate of the liquid phase is also defined. An expression describing the induction period can be used to determine the critical duration of the discharge, the reduction of which will lead to the ignition of the vapor-gas phase

The Dependence between the Ignition Value of Air Suspension and the Size of the Reaction Chamber

The influence of the geometric factor of the reaction chamber on the limit value of the air suspension ignition is studied. It is found that in determining the lower concentration limit of the flame propagation (LCLFP), it is most promising to use an installation with a cylindrical reaction chamber whose height is equal to the diameter. The dependence of the determination of the LCLFP value on the geometric factor of the reaction chamber is proposed, tested on metal powders and organic dust-forming materials. The expression allowing to carry out the comparative analysis of scientific results received on other technical devices with the results received on the installations executed according to the requirements of normative and technical documentation is received that significantly reduces the volume of experimental works

Definition of Time Induction of Self-Ignition of the Substance on the Prognostic Extrapolation Depending on the Basis of Indicators Fire and Explosion Hazard

In this article the research directed on development of a technique of definition of time of induction of the self-ignition of substances and materials which is an indicator of the beginning of development of an emergency is conducted. The experiment consisting in supervision over process of self-ignition of coal and oil deposits was the basis for research. On the basis of experimental data the curve expressing analytic - expected dependence of size of temperature of ignition on induction time was constructed. Proceeding from graphical representation of process, functional dependence of time of induction on a temperature indicator was received: y=16920•x{0.537}. By means of known indicators of such substances as bitumen oil oxidized (the combustible solid substance received by oxidation of residual product of oil refining) and tar oil (the combustible solid substance which is residual product of oil refining) and the received algorithm, verification of reliability of the received dependence and a technique of definition of time of induction of spontaneous ignition of deposits of oil in general was carried out. The practical importance of the conducted research is that having data on time of induction of process of self-ignition, by means of preventive measures becomes possible to avoid and prevent accidents in oil and oil processing branches, at the same time loss of property and loss of human life

Carrying out thermodynamic calculations and definition of the main reactions of decomposition of vapours of ethyl alcohol

Thermodynamic opportunities of course of chemical reactions of decomposition of the vapors of ethyl alcohol necessary at development of devices where these reactions will take place are considered. The entalpiyny method of calculation of constants of balance of probable chemical reactions is given in the Excel editor. Independent reactions of process of oxidation are defined. By result of thermodynamic calculation of each reaction schedules of dependence of a constant of balance on environment temperature from which follows are constructed that one reactions proceed until the end of aside formation of the final products, and others are improbable or impossible. The analysis of the received results shows that reactions of oxidation will successfully proceed in the established directions, and for an intensification of process of decomposition it is necessary to provide a supply of some energy which quantity will be sufficient for oxidation of vapors of ethyl alcohol. Results of calculations showed good convergence with programs of thermodynamic calculations like "Aster-4" and "TERRA"

Characterization of copper nanopowders after natural aging

Copper nanopowders after storage under natural conditions can oxidize and change their properties. In this work, the phase composition, morphology and thermal properties of copper nanopowders after natural aging of 10 years were studied. The copper nanopowders were produced by the method of electrical explosion of wires in different gaseous ambient: argon and carbon dioxide. The nanopowders were characterized by X-ray diffraction, thermal analysis, scanning electron microscopy, Fourier transform infrared spectroscopy. The content of copper oxides phases was found to be increased in comparison with freshly synthesized powders. This transformation results in the change of the thermal characteristics of the nanopowders. The effect of the synthesis conditions on the composition and thermal characteristics was shown

The dependence between the ignition value of air suspension and the size of the reaction chamber

The influence of the geometric factor of the reaction chamber on the limit value of the air suspension ignition is studied. It is found that in determining the lower concentration limit of the flame propagation (LCLFP), it is most promising to use an installation with a cylindrical reaction chamber whose height is equal to the diameter. The dependence of the determination of the LCLFP value on the geometric factor of the reaction chamber is proposed, tested on metal powders and organic dust-forming materials. The expression allowing to carry out the comparative analysis of scientific results received on other technical devices with the results received on the installations executed according to the requirements of normative and technical documentation is received that significantly reduces the volume of experimental works

Influence of long-term storage on fire hazard properties of metal nanopowders

The production and application of nanomaterials is rapidly expanding. Therefore the problem of their properties change during long-term storage becomes essential. The properties of metal nanopowders after long-term storage under ambient conditions were studied and the results are presented in this work. The aluminum, iron, zinc, and copper nanopowders produced by the method of electrical explosion of wires were investigated in this work. The investigation was carried out by X-ray and thermal analysis. The estimation of the flame propagation velocity in the bulk layer of nanopowders was carried out. The characteristics of the nanopowders of nanometals studied are given in terms of their fire hazard. The results can be used for diagnostic of fire hazard of nanomaterials and protection of the enterprises against fire and explosion

Development of installation for study of electrostatic fields

The safe installation for studying the model electrostatic fields in the model areas of the cyclone is developed. It is found that the induction neutralizer reduces the concentration of ethyl alcohol (ethanol) in the examined object. The distance between the charged region in the cyclone and the neutralizer is the correction value of the height of the corona needles that is characterized by the magnitude of the ignition energy of the medium in the cyclone. The research results can be used in the development of cyclone apparatus for explosive industries, as well as measures to reduce technological emissions into the environment

Method of comprehensive assessment of efficiency of decrease of fire and explosion risk of coal suspended particles

Methods and results of experimental study of explosive and wetting characteristics of coal dust are presented. Modified evaluation method of explosive characteristics of coal dust allows estimating critical concentrations of suspended dust at variation of temperature of ionizing ignition source corresponding to beginning of flame propagation by means of approximation method. Method of measuring the contact angle of particles of coal powder is based on visualization of the drop placed on the pressed coal