# Microwave Pyrolysis of Biomass: The Influence of Surface Area and Structure of a Layer
## 4 Results and Discussion
### Influence of Biomass Particle Size  
This section presents the results on the effect of biomass particle fineness on the yield of pyrolysis gas. We used sawdust with an average particle size of 140, 250 and 2000 \(\upmu\)m, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Experiment**} & \multirow{2}{*}{**Gas**} & **Average** & **Average** & **Average** & **Total Amount of** \\  & & **Concentrations** & **Concentrations** & **Concentrations** & **Pyrolysis Gas** \\  & & **(\%)** & **(ppm)** & **(mg/m\({}^{3}\))** & **(mg/m\({}^{3}\))** \\ \hline \multirow{8}{*}{Artificial channels} & CO & 14.63 & 146,300 & 170,352 & 168,818,832 \\  & CO\({}_{2}\) & 7.22 & 72,200 & 132,092 & 117,958,156 \\  & CH\({}_{4}\) & 6.02 & 60,200 & 40,141 & 40,462,128 \\ \cline{1-1}  & H\({}_{2}\) & 1.33 & 13,300 & 1114 & 1,122,912 \\ \cline{1-1}  & H\({}_{2}\)S & 0.007092 & 70.92 & 100 & 98,700 \\ \cline{1-1}  & SO\({}_{2}\) & 0.00293 & 29.3 & 78 & 34,554 \\ \cline{1-1}  & NO & 0.00012 & 0.12 & 0.15 & 4.8 \\ \hline \multirow{8}{*}{Artificial pores} & CO & 16.47 & 164,700 & 191,777 & 197,146,756 \\ \cline{1-1}  & CO\({}_{2}\) & 8.03 & 80,300 & 146,911 & 131,191,523 \\ \cline{1-1}  & CH\({}_{4}\) & 6.45 & 64,500 & 430,008 & 144,948 \\ \cline{1-1}  & H\({}_{2}\) & 1.21 & 12,100 & 1013 & 1,041,364 \\ \cline{1-1}  & H\({}_{2}\)S & 0.010178 & 101.78 & 144 & 148,032 \\ \cline{1-1}  & SO\({}_{2}\) & 0.003681 & 36.81 & 98.03 & 44,394 \\ \cline{1-1}  & NO & 0.000424 & 4.24 & 5.29 & 2507.46 \\ \hline \multirow{8}{*}{Uniform layer} & CO & 15.5 & 155,000 & 180,482.36 & 465,102,114 \\ \cline{1-1}  & CO\({}_{2}\) & 7.01 & 70,100 & 128,250.58 & 138,382,375 \\ \cline{1-1}  & CH\({}_{4}\) & 2.88 & 28,800 & 19,203.78 & 45,319,080 \\ \cline{1-1}  & H\({}_{2}\) & 0.88 & 8800 & 737.36 & 22,739,200 \\ \cline{1-1}  & H\({}_{2}\)S & 0.003759 & 37.59 & 53.26 & 50,104,47 \\ \cline{1-1}  & SO\({}_{2}\) & 0.00165 & 16.5 & 43.94 & 18,298.5 \\ \cline{1-1}  & NO & 0.00123 & 12.3 & 15.34 & 31,783.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The yield of the main gases. which were pre-impregnated with moisture. The sample weight was 15 g. Figure 16 shows emission trends obtained during the pyrolysis of biomass with different particle sizes. It has been established (Figure 16) that the H\({}_{2}\) release starts from the first seconds of heating during the pyrolysis of particles with a size of 2000 \(\upmu\)m. In this case, the longest time for the release of pyrolysis gas was observed. The shortest gas emission time was recorded during the pyrolysis of particles with an average size of 140 \(\upmu\)m. During the pyrolysis of particles of this size, one peak in the concentrations of CO and CO\({}_{2}\) (62.5% and 19%, respectively), as well as two peaks in the concentrations of CH\({}_{4}\), were observed (Figure 16a). Figure 17 shows the average and maximum concentrations of the gas mixture components. Experiments have shown that pyrolysis of smaller particles (140 \(\upmu\)m and 250 \(\upmu\)m) gives higher concentrations of CH\({}_{4}\) and H\({}_{2}\) (Figure 17). The yield of CO during the pyrolysis of sawdust with a particle size of 140 \(\upmu\)m increased by 12% and 65% compared to particles with a size of 250 \(\upmu\)m and 2000 \(\upmu\)m, respectively (Figure 17a). A similar comparison was made for other gases: the CO\({}_{2}\) yield increased by 1.5% and 15%, the CH\({}_{4}\) yield increased by 30% and 60%, and the H\({}_{2}\) yield increased by 1.5% and 43%. During the pyrolysis of biomass with a particle size of 140 \(\upmu\)m, the maximum yield of CH\({}_{4}\) and H\({}_{2}\) increased by 3 and 1.5 times, respectively, compared with the particles of 2000 \(\upmu\)m (Figure 17b). Table 7 shows the gas flow rates obtained during the experiments. Figure 16: Trends of the concentrations of gas mixture components when varying the biomass particle size: 140 \(\upmu\)m (**a**); 250 \(\upmu\)m (**b**); 2000 \(\upmu\)m (**c**); a comparison of component concentrations (**d**).