In the master's thesis, we analyzed two commercially available samples of ground and instant coffee. We characterized the samples; we performed a thermal analysis and measured the particle size distribution and determined their minimum ignition energy (MIE). We also determined the maximum explosion pressure (pmax) and the maximum rate of pressure rise (dp/dt)max for the sample of instant coffee.
Particle size measurements showed that the particle size of the ground coffee sample ranged from 26 µm to 498 µm, and the instant coffee sample ranged from 189 µm to 2000 µm. The moisture content of the ground coffee sample is 4,83% moisture content, while the instant coffee sample contains 0,86% moisture content. Based on the obtained results, we found that the instant coffee sample is more explosively sensitive than the ground coffee sample. This can be attributed to the very low moisture content and the composition of the powder itself, as it contains whey powder, sugar and milk powder in addition to coffee. The range in which instant coffee ignites is between 300 and 600 mJ. The value of the maximum explosion pressure was 7,8 bar. According to the calculated value of the dust deflagration index (Kst), we classify instant coffee in the first class of dust explosion.
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