Assessment of explosion risk for wood dust in a ventilation-dust separation installation, by determining the concentration of total dust in suspension inside of the installation

Most of combustible dusts present both fire and explosion hazard. Explosion may occur at certain concentrations of dust mixed with air and in the presence of an ignition source. The threat posed by this real danger was confirmed by the events that took place in economic units such as: feed factories, wood products, textile industry, steel, etc. Among the parameters of explosiveness of combustible dust, which can cause an explosion, we mention: maximum explosion pressure, lower explosion limit, explosive index, minimum ignition energy, electrical resistivity of dust, minimum ignition temperature of dust layer and cloud, particle size and concentration of dust in suspension. The current paper presents the results of determinations of combustible wood dust concentrations, performed at an important economic unit, manufacturing veneer and wood panels, at a dusting ventilation installation composed of fan, cyclone and textile filter. These determinations were made in the pipe connecting the fan and the bag filter, to assess possible danger of explosion in the pipe, by relating the measured concentration to the lower explosion limit (concentration of wood dust).

Effect of Turbulence On Forced Ignition of Jet-A/Air Mixtures

Consistent ignition of reactive mixtures in turbulent conditions continues to be a challenge, particularly for large, multi-component fuels. Prior work has shown that turbulence can affect ignition parameters such as flame speed, mixture temperature, and minimum ignition energy. However, these works have primarily considered small, single-component fuels. This work studies the effect of turbulence on forced ignition of jet-A/air mixtures with f between 0.3 and 0.7. The ignition probability of these mixtures was measured for bulk velocities between 5 and 7 m/s and turbulence intensities between 3% and 9%. A FLIR SC6700 infrared camera was used to measure the radiation intensity emitted by the flame kernels. Increases in turbulence intensity between 3% and 4% cause the probability of ignition to generally increase. This increase is attributed to the negative flame stretch that develops as a result of the turbulence. This observation is significant because it shows that turbulence can facilitate ignition for jet-A/air mixtures. In contrast, increasing turbulence beyond 5% causes ignition probabilities to decrease. This reduction occurs due to the increased role of heat diffusion and the associated reduction in kernel temperature. The sensitivities of ignition behavior to turbulence intensity and fuel chemistry are reasonably captured using the Peclet number. Further agreement in ignition behavior is achieved by considering Pe/TI2. Ignition probability data for two additional fuels were compared using Pe/TI2. Reasonable agreement within a 95% confidence interval was observed for CH4 mixtures but not for C3H8 mixtures.

Physical-and-chemical calculations of safe mode of propane transportation

The key criteria used to assess fire-and-explosive hazard of any facility are: flash point, self-ignition temperature and minimum ignition energy. This article addresses how fire-and-explosive hazard criteria can be used to forecast emergency situations while transporting great quantities of flammable substance – propane, based upon ambient environment temperature. Calculations that were made have led to a conclusion that fire-and-explosive safety concentration mode for propane handling will be: lower concentration value is equal to 1.27 % or under than that value; upper concentration value is equal to 13.96 % or greater than that value. When selecting safe transportation and storage conditions for self-igniting combustible substances, great attention is given to relationship between environment, mass of substance transported and time-period to spontaneous ignition. For propane, the safe self-ignition temperature is deemed to be less than 360°C. Calculations for theoretical experiment regarding propane transportation were made based upon three critical temperature values: 1) 25 °C+10 °C - initial starting point when ambient temperature is 25 °C (roadway temperature is disregarded because ambient temperature is not high enough); 2) 60 °C+10 °C – point of arrival where ambient temperature is 60 °C; 3) 470 °C – propane self-ignition temperature. This helped us to figure out that propane can be stored and transported safely if the minimal electric ignition source is under 4*10−6 Joule.

The Fire and Explosion Hazard of Coloured Powders Used during the Holi Festival

During the world-famous Holi festival, people throw and smear each other with a colored powder (Holi color, Holi powder, Gulal powder). Until now, adverse health and environmental effects (skin and eye irritation, air pollution, and respiratory problems) have been described in the available literature. However, the literature lacks data on the flammable and explosive properties of these powders during mass events, despite the fact that burns, fires, and explosions during the Holi festival have taken place many times. The aim of the article is to present the fire and explosion parameters of three currently used Holi dust and cornflour dust types as reference dust. The minimum ignition temperature of the dust layer and dust cloud, the maximum explosion pressure and its maximum rate of growth over time, the lower explosion limit, the limit of oxygen concentration, and the minimum ignition energy were determined. Tests confirmed that the currently available Holi powders should be classified as flammable dusts and low-explosive dusts. The likelihood of a fire or explosion during mass incidents involving a Holi dust-air mixture is high.

Experimental Study on Ignition Characteristics of RP-3 Jet Fuel Using Nanosecond Pulsed Plasma Discharge

A study on forced ignition characteristics of RP-3 jet fuel-air mixture was conducted around a constant volume combustion vessel and a nanosecond pulsed plasma discharge power supply. Experiments were carried out at different initial pressures (pu = 0.2, 0.3, 0.5 atm), equivalence ratios (ϕ = 0.7, 0.8, 1.1), steam concentrations (ZH2O = 0%, 10%, 15%) and oxygen concentrations (ZO2 = 13.5%, 16%, 21%). The relationship between ignition probability and ignition energy is investigated. The experimental results show that the decrease in pressure, equivalence ratio, oxygen concentration and the increase in steam concentration all lead to an increase in minimum ignition energy (MIE). In order to further analyze the experimental data, one existing fitting equation is reformed with the initial conditions taken into account. Multivariate fitting is carried out for different conditions, and the fitting results of ignition probability are in good agreement with the experiments. The MIE results under different experimental conditions are figured out with the new fitting equation. The impact indexes, which stand for the effects of different factors, are also calculated and compared in present work.

Research on Ignition Energy Characteristics and Explosion Propagation Law of Coal Dust Cloud under Different Conditions

To study the ignition energy characteristics and explosion propagation law of coal dust cloud, a kind of coal dust cloud is studied through experiment and numerical simulation under different conditions. The result indicated that ignition delay time and dust spray pressure have obvious effects on the minimum ignition energy of coal dust cloud. CFD theory is used to simulate the explosion flame propagation. It is found that the simulation error of flame propagation distance is acceptable and the simulation result is consistent with the experimental result. When the spray pressure is 0.06 MPa, the flame propagation distance is the farthest, indicating that the turbulence of coal dust cloud is the largest at this condition. As the ignition temperature increases, the flame propagation distance continues to increase, proving that ignition temperature has an obvious effect on the flame propagation process of coal dust cloud explosion.

Experimental and Numerical Study of Ignition and Flame Propagation for Methane–Air Mixtures in Small Vessels

Methane is one of the most common gaseous fuels that also exist in nature as the main part of the natural gas, the flammable part of biogas or as part of the reaction products from biomass pyrolysis. In this respect, the biogas and biomass installations are always subjected to explosion hazards due to methane. Simple methods for evaluating the explosion hazards are of great importance, at least in the preliminary stage. The paper describes such a method based on an elementary analysis of the cubic law of pressure rise during the early stages of flame propagation in a symmetrical cylindrical vessel of small volume (0.17 L). The pressure–time curves for lean, stoichiometric and rich methane–air mixtures were recorded and analyzed. From the early stages of pressure–time history, when the pressure increase is equal to or less than the initial pressure, normal burning velocities were evaluated and discussed. Qualitative experiments were performed in the presence of a radioactive source of 60Co in order to highlight its influence over the explosivity parameters, such as minimum ignition energy, maximum rate of pressure rise, maximum explosion pressure and normal burning velocity. The results are in agreement with the literature data.