# Microwave Pyrolysis of Biomass: The Influence of Surface Area and Structure of a Layer
## 3 Experimental Setup and Procedures
### Experimental Technique for Measuring the Composition of Gases  
The experimental procedure included the following stages:  
A fuel sample was formed, which was weighed on an OHAUS Adventurer AX 324 analytical balance with an accuracy of 10\({}^{-5}\) g.  
The mass of the fuel sample in each experiment varied from 10 to 20 g, based on the goals of the experiment. Before the experiments, the sawdust was dried for 5 days under normal conditions, then soaked in a container with 200 mL of water. For the experiments with varying particle dispersion, the sawdust was preliminarily ground using a Pulverisette 14 rotary mill and sieved to separate the 140, 250 and 2000 \(\upmu\)m fractions. The fuel sample was placed in a ceramic heat-resistant crucible, which was used as a substrate. The wall thickness of the crucible was 0.5 cm, the height of the crucible was 9 cm and the diameter was 9.5 cm. Depending on the variable parameter (surface area, layer structure), the distribution of the fuel sample on the crucible bottom changed (Figure 1a). In other experiments, the fuel was located along the edge of the crucible from the side of the magnetron. The crucible was placed in a microwave oven, after which its door was hermetically closed (Figure 1b). Oxygen was present in the microwave chamber initially before the start of the magnetron operation because the sample was loaded into the reactor through the door. Air \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Component** & **Measurement Range** & **Accuracy** & **Response Time** \\ \hline O\({}_{2}\) & 0–25\% & \(\pm\)0.2 vol\% (absolute) & \(\leq\)15 s \\ H\({}_{2}\) & 0–5\% & \(\pm\)0.2 vol\% (absolute) & \(\leq\)35 s \\ CO\({}_{2}\) & 0–30\% & \(\pm\)2\% (basic percentage error) & \(\leq\)25 s \\ CH\({}_{4}\) & 0–30\% & \(\pm\)5\% (of the indication) & \(\leq\)25 s \\ CO & 0–40000 ppm & \(\pm\)5\% (of the indication) & \(\leq\)35 s \\ NO & 0–1000 ppm & \(\pm\)5\% (of the indication) & \(\leq\)35 s \\ NO\({}_{2}\) & 0–500 ppm & \(\pm\)7\% (of the indication) & \(\leq\)45 s \\ SO\({}_{2}\) & 0–1000 ppm & \(\pm\)5\% (of the indication) & \(\leq\)45 s \\ H\({}_{2}\)S & 0–500 ppm & \(\pm\)5\% (of the indication) & \(\leq\)45 s \\ HCl & 0–2000 ppm & \(\pm\)5\% (of the indication) & \(\leq\)45 s \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Specifications of the gas analyzer. entered the reactor through the same door due to natural convection. Forced air flow was not created. An inert atmosphere was not created in the reactor in the present study to match the most widely used air-type reactors. Then, the microwave heating was turned on. After the concentrations of CO began to decrease, the heating was turned off. The release of pyrolysis gas took place when heat was no longer supplied from an external source. During the experiment, the probe sampled gaseous products. Then they fell into the moisture separator, where the liquid was separated. The purified gases were then sent to the sensors. Real-time parameters were displayed on the PC monitor. During the experiment, atmospheric air did not enter the oven. The duration of each experiment varied from 30 to 60 min. After the experiment, the solid residue was weighed. Before starting the next measurement, the reactor and all gas channels were purged with compressed air. Within one series, from 2 to 3 experiments were carried out under identical conditions. Next, data processing was carried out. Experimental results were averaged and random gross errors were eliminated. The results of experimental measurements were subjected to primary processing in order to eliminate random gross errors. A gross error is a result (time-averaged value of the gas concentration) that differs significantly from the expected one. Since the results of these experiments obeyed a normal distribution, it is advisable to use the 3-sigma rule to eliminate gross errors. However, this rule is reliable for a large number of measurements (over 20). Therefore, we relied on a modified approach ([PERSON]'s criterion).