This master's thesis explores the dangers of dust explosions in processes involving combustible powders. These powders are usually very small and have a large specific surface area, which enables them to react rapidly with the oxidant when an ignition source is present. The most explosive dust substances include sugar, flour, coal, wood dust, various polymer materials, rubber, various metal powders, etc.
The thesis closely examines experimental methods for determining key parameters which influence dust explosions: minimum ignition energy, minimum explosible concentration, maximum explosion pressure and maximum pressure rise rate. Furthermore, it introduces a classification of dust explosions and a description of polymer materials such as high-density polyethylene (HDPE), polypropylene (PP) and polyethylene terephthalate (PET), which are most commonly used in industrial plants.
Several other methods are included in the experimental part: determination of flammability, sieve analysis, determination of bulk and compaction density, analysis of particle size, thermal analysis and determination of specific surface area. These methods encompass all the key areas of dust particle characterization.
The results of the comparison between the “as it is” sample and the “<100 μm” fraction show significant differences in explosion parameters. The minimum ignition energy of the “as it is” sample was measured to be less than 3 mJ, and the minimum explosible concentration was 60 g/m3, whereas the MIE of the “<100 μm” sample was in the range between 3 and 10 mJ, and the MEC was 30 g/m3. Pmax is 7.9 bar for the “<100 μm” sample and 7.4 bar for the “as it is” sample. There is a slightly larger difference in (dp/dt)max as this only amounts to 469 bar/s for the “<100 μm” sample and 624 bar/s for the “as it is” sample. The data indicates that it is easier to achieve conditions for ignition and a consequent dust explosion with smaller particles.
These results highlight the importance of particle size control when dealing with dusty materials in industrial plants. While larger particles pose a lower risk, smaller particles pose a greater risk of dust explosions and thus require stricter safety measures. The obtained results thus contribute to a better understanding of the influence particle size has on explosion parameters and help with designing appropriate safety protocols for handling explosive dust particles.
The most important measures to ensure safety in industrial plants include regular employee training and awareness raising, regular cleaning and maintenance of work spaces and equipment, the use of antistatic clothing and explosion-proof equipment, and the grounding of work equipment. While individual safety measures increase safety to some extent, the best results are achieved with the simultaneous use of a number of different measures which, working as a whole, ensure maximum explosion safety.
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