## 3 Results and Discussion  
The results of the particle size distributions measured using laser diffraction are presented in Table 2, which shows the size particle below 10% (d10), 50% (d50), and 90% (d90) of the sample. The moisture was calculated as the arithmetic mean of three tests when the standard deviation is lower than 15%, and ten tests when greater. The results of the moisture are shown in the same table. Measuring particle size for biomass can present problems, due to the shapes of the biomass particle not only when presented in coarse size, but also after milling [45]. In this study, coarse samples presented different sizes and shapes. Thus, the results written in the table show the greater size  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{3}{c}{**Granulometric Analysis [\(\mu\)m]**} & \multirow{2}{*}{**Moisture [\%]**} \\ \cline{2-2} \cline{4-5}  & **d10** & **d50** & **d90** & \\ \hline PS-C & - & \(8\times 10^{3}\) & - & 7.7 \\ PS-1 & 241.9 & 637.7 & 1302.7 & 7.9 \\ PS-75 & 9.5 & 48.7 & 138.2 & 6.2 \\ WS-C & - & \(1.2\times 10^{3}\) & - & 7.8 \\ WS-1 & 68.7 & 298.1 & 890.9 & 7.1 \\ WS-75 & 5.0 & 9.9 & 93.8 & 6.6 \\ Cb1-C & - & \(56\times 10^{3}\) & - & 6.0 \\ Cb1–1 & 56.3 & 364.5 & 879.7 & 5.9 \\ Cb1–75 & 3.8 & 24.2 & 73.8 & 6.0 \\ Cb2-C & - & \(54\times 10^{3}\) & - & 4.7 \\ Cb2–1 & 4.5 & 22.8 & 101.6 & 5.0 \\ Cb2–75 & 3.9 & 17.6 & 51.8 & 4.7 \\ DF-C & - & \(18\times 10^{3}\) & - & - \\ DF-1 & 22.8 & 217.3 & 712.7 & 7.0 \\ OP-C & - & \(150\times 10^{3}\) & & - \\ OP-1 & 111.6 & 415.5 & 1052.0 & 7.3 \\ OP-75 & 3.9 & 41.2 & 104.3 & 7.0 \\ \hline \hline \endconsidering length, width, and height. Pine shaving (PS-C) shaped as chips whose mean length was 8 mm. Olive pellets (OP-C) shaped like cylinders with 5 mm diameter and 150 mm length. Both brands of charcoal samples (Cb1-C and Cb2-C) were briquettes 2 mm in width, and 56 and 54 mm in mean length. Dog food (DF-C) presented different shapes as chips and small bricks, so the greater mean length was considered (18 mm). Particle shape also affected the finer particles results. Samples as olive pellets and pine shaving might be filament-shaped after milling, so that they may go through the sieve mesh. However, when applying a more accurate method as laser diffraction, it can be seen that particle size is greater than the sieve mesh size (1 mm or 75 \(\upmu\)m). Milling the other samples produced powder with somehow spherical particles, so this difference between sieve and laser diffraction was not present. Regarding the N4 4.2 United Nations test, a temperature versus time graph is obtained. The test was carried out using three K-type thermocouples: Two outside the sample (to the right and left) and one inside the basket that contains the sample. The thermocouples outside the sample measured oven temperature, while the one inside the basket provided sample temperature. When the sample presented self-heating, the sample thermocouple recorded higher temperatures than the other two. When not, the three thermocouples remained at the oven temperature along with all the test time. Because of that, when plotting results, only the sample thermocouple was represented. For the samples used, the test turned to be negative in most of the cases, meaning that the sample did not need classification according to the UN normative. However, when testing Cb1-75, Cb2-1, and Cb2-75, the result changed; those samples were classified as exempted from classification when only transported in piles smaller than 3 m\({}^{3}\). It means that, for different particle sizes of the same material, two different classifications may be obtained. This is a very important result, since it greatly affects the possible classification of some products and shows how heat transfer mechanisms may vary depending on granulometry in a more intensive way than composition or moisture. Figure 1 shows the charcoals samples thermocouple record in the three different sizes described previously.