# Evaluation of Marblewood Dust's (_Marmaroxylon racemosum_ Effect on Ignition Risk
## 3 Results and Discussion  
Marblewood (_Marnuroxylon racemosum_) is ranked among the hardwoods. Everything about working with it revolves around its incredible hardness and density [40]. The density is measured based on the mixed particles' size before sieve analysis. Different types of dry woods, dried to a constant weight (105 \({}^{\circ}\)C), have practically the same elementary chemical composition and the same density of wood substance [9]. Disintegration of wood into dust does not change the elemental chemical composition but changes the ratio of surface size to volume of disintegrated particles (example Figure 3) and changes the density (Table 1). Density and humidity are standard values to be considered when evaluating the examined dust samples. The marblewood dust experiments were performed in agreement with other experiments. Dust is a crushed (dispersed) solid and can be dispersed in air to form a dust-air mixture. The particle size in dust dispersion is determined by sieve analysis (particle size distribution), which determines the percentage of particles of a certain size (Table 2). Dust dispersion has a significant effect on its ignition risk. More-dispersed dust has a considerably large surface area, increased chemical activity, and a lower minimum ignition temperature [42; 43], as seen in Table 2.  
Marblewood has the highest tested minimum ignition temperature (Table 2) as compared with other tropical wood dusts [35]. It was found that more than 65% of particles were sized below 100 \(\upmu\)m. This fact determines the possibility of the formation of airborne dust mixtures. The airborne mixtures of wood dust pose a risk of reaching explosive concentrations. The experimental results show a minimum initiation temperature for the airborne dust mixture of 400 \({}^{\circ}\)C. As the particle size increases, the ignition temperature value increases, for 500 \(\upmu\)m it is 420 \({}^{\circ}\)C. The minimum ignition temperature for airborne dust is the lowest furnace temperature at which ignition occurred in this process, reduced by 20 \({}^{\circ}\)C for furnace temperatures above 300 \({}^{\circ}\)C [36]. This condition for the ignition of marblewood particles was met. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Dust**} & \multicolumn{3}{c}{**Parameters**} & \multicolumn{1}{c}{**Sources**} \\ \cline{2-5}  & **Density of Raw** & **Average Bulk** & **Dust Moisture** & \\  & **Wood (kg\(\cdot\)m\({}^{-3}\))** & **Density (kg\(\cdot\)m\({}^{-3}\))** & **(\%)** & \\ \hline oak & 672.86 & 238.01 & 6.00 & \\ beech & 686.84 & 189.00 & 6.10 & [41] \\ spruce & 446.35 & 77.77 & 7.80 & \\ \hline marblewood & 1000.8 & 187.9 & 7.34 & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of density and moisture of selected wood dusts with experimental sample. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Fraction Size, MW**} & \multirow{2}{*}{**Particle (\%)**} & **Minimal Ignition** & **Minimal Ignition** \\  & & **Temperature (\({}^{\circ}\)C),** & **Temperature (\({}^{\circ}\)C), 5 mm** \\  & & **Airborne Dust** & **Dust Layer** \\ \hline
500 & 1.26 \(\pm\) 0.244 & 420 & \\ \hline
315 & 5.33 \(\pm\) 0.591 & 420 & \\ \hline
200 & 27.31 \(\pm\) 0.462 & 420 & Temperature \\ \hline
100 & 39.61 \(\pm\) 0.367 & 410 & of ignition source \\  & & & (\({}^{\circ}\)C) \textless{}300 \({}^{\circ}\)C, \\ \hline
71 & 15.22 \(\pm\) 0.111 & 400 & Experimental time 120 s \\ \hline
63 & 5.5 \(\pm\) 0.383 & 400 & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Experimental result analysis of marblewood dust. For dust layers, depth is the most important factor affecting the ignition temperature, particle size is not important, and density affected the ignition temperatures only for thin layers [13]. The MIT of a dust layer is the lowest temperature of a surface at which a dust layer resting on the surface can self-ignite. This is usually given for a 5 mm deep layer [44]. [PERSON] (2013) [45] researched a variety of wood dust layer samples.