Fire Parameters of Spruce (Picea abies Karst. (L.)) Dust Layer from Different Wood Technologies Slovak Case Study

The issue of the formation of wood dust particles in the work environment is still an actual topic in terms of its impact on employee health and the risk of fire or explosion in a woodworking operation. This article deals with the characteristics of spruce dust (Picea abies Karst. (L.)), which was taken from several types of wood technology. Experimental samples of spruce dust were taken from four types of sawing technologies, including grinding, briquetting and from the suction device container. The physical parameters of the samples taken were monitored and the particle size analysis was determined. The granulometric composition of the samples is significantly different. The sample of spruce wood dust from sawing has the most numerous fraction (250 µm), while the sample from grinding has the most numerous fraction 63–250 µm (87%).The aim of the paper was to monitor the minimum ignition temperature of the settled spruce dust layer and to look for a significant dependence of the minimum ignition temperature and ignition time on the type of spruce dust sample. A significant dependence was not confirmed. Significant moisture dependence of the samples was confirmed; the highest humidity was observed in the container, the lowest in sawing.

Evaluation of Marblewood Dust’s (Marmaroxylon racemosum) Effect on Ignition Risk

The paper deals with the selected characteristics, such as moisture, average bulk density, and fraction size, of tropical marblewood dust (Marmaroxylon racemosum) that influence its ignition risk. Research was focused on sieve analysis, granulometric analysis, measurement of moisture level in the dust, and determination of the minimum ignition temperatures of airborne tropical dust and dust layers. Samples were prepared using a Makita 9556CR 1400W grinder and K36 sandpaper for the purpose of selecting the percentages of the various fractions (<63, 63, 71, 100, 200, 315, 500 μm). The samples were sized on an automatic vibratory sieve machine Retsch AS 200. More than 65% of the particles were determined to be under 100 μm. The focus was on microfractions of tropical wood dust (particles with a diameter of ≤100 µm) and on the impact assessment of particle size (particle size <100 µm) on the minimum ignition temperatures of airborne tropical dust and dust layers. The minimum ignition temperature of airborne marblewood dust decreased with the particle size to the level of 400 °C (particle size 63 μm).

Combined Effect of Dispersion Pressure and Concentration on Minimum Ignition Temperature of Corn Dust using Response Surface Methodology – Preliminary Investigation

Corn dust is a significantly energetic dust and widely used substance in food processing industries. It not only poses dust hazards like suffocation or lungs related issues to the exposed workers but also is highly combustible under a conducive environment. In this study, the minimum ignition temperature (MIT) of corn dust clouds was evaluated at varying combinations of dispersion pressure and concentration using a Godbert–Greenwald (G–G) furnace. A response surface was generated using design expert as a tool for the application of response surface methodology (RSM). The predicted R2 and adjusted R2 are reasonably in close agreement as the difference is less than 0.2. The predicted surface is found to be in good agreement with the experimental results. However, as this is a preliminary study, the model will be improved in future research.

Variation of ignition sensitivity characteristics of non-stick coal dust explosions

The ignition and explosion of coal dust are significant hazards in coal mines. In this study, the minimum ignition temperature and energy of non-stick coal dust were investigated empirically at different working conditions to identify the key factors that influence the sensitivity and characteristics of coal dust explosions. The results showed that for a given particle size, the minimum ignition temperature of the coal dust layer was inversely related to the thickness of the coal dust layer. Meanwhile, when the layer thickness was kept constant, the minimum ignition temperature of the coal dust layer decreased with smaller coal dust particle sizes. Over the range of particle sizes tested (25–75 μm), the minimum ignition temperature of the coal dust cloud gradually increased when larger particles was used. At the same particle size, the minimum ignition temperature of the coal dust layer was much lower than that of the coal dust cloud. Furthermore, the curves of minimum ignition energy all exhibited a minimum value in response to changes to single independent variables of mass concentration, ignition delay time and powder injection pressure. The interactions of these three independent variables were also examined, and the experimental results were fitted to establish a mathematical model of the minimum ignition energy of coal dust. Empirical verification demonstrated the accuracy and practicability of the model. The results of this research can provide an experimental and theoretical basis for preventing dust explosions in coal mines to enhance the safety of production.

Investigation into the Suppression Effects of Inert Powders on the Minimum Ignition Temperature and the Minimum Ignition Energy of Polyethylene Dust

The risks associated with dust explosions still exist in industries that either process or handle combustible dust. This explosion risk could be prevented or mitigated by applying the principle of inherent safety. One effective principle is to add an inert material to a highly combustible material in order to decrease its ignition sensitivity. This paper deals with an experimental investigation of the influence of inert dust on the minimum ignition temperature and the minimum explosion energy of combustible dust. The experiments detailed here were performed in a Godbert–Greenwald (GG) furnace and a 1.2 L Hartmann tube. The combustible dust (polyethylene—PE; 800 mesh) and four inert powders (NaHCO3, Na2C2O4, KHCO3, and K2C2O4) were used. The suppression effects of the four inert powders on the minimum ignition temperature and the minimum explosion energy of the PE dust have been evaluated and compared with each other. The results show that all of the four different inert dusts have an effective suppression effect on the minimum ignition temperature and the minimum explosion energy of PE dust. However, the comparison of the results indicates that the suppression effect of bicarbonate dusts is better than that of oxalate dust. For the same kind of bicarbonate dusts, the suppression effects of potassium salt dusts are better than those of the sodium salt. The possible mechanisms for the better suppression effects of bicarbonate dusts and potassium salt dusts have been analyzed here.