# Study of the Applicability of Thermochemical Processes for Solid Recovered Fuel
## 2 Materials and Methods
### Gasification  
#### 2.2.1 Experimental Setup  
The gasification experiments were carried out in the laboratories of the Thermochemical Processes Group (Aragon Institute of Engineering Research, I3A, of the University of Zaragoza). A laboratory-scale fluidised bed reactor was used to gasify SRF from screening waste, at atmospheric pressure. The gasifier, made of AISI 310 refractory steel, was divided into two parts: a bed zone with an inner diameter of 40 mm and a freeboard zone with an inner diameter of 63 mm. Some problems were encountered during feeding because bridging was detected in the silos due to the low density of the material, so it was decided to feed the process with SRF in pellet form. Pellets were fed manually through a double valve feeding system placed at the upper part of the reactor at a constant rate of 1.5 g/min. An electric furnace heated the reactor with three independent heating zones for the bed, freeboard, and cyclone. During the tests, the bed temperature was maintained at 800 \({}^{\circ}\)C, \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter (Dry Basis)** & **Value** \\ \hline C (wt\%) & 52.80 \(\pm\) 0.4 \\ H (wt\%) & 7.43 \(\pm\) 0.09 \\ N (wt\%) & 2.685 \(\pm\) 0.007 \\ S (wt\%) & 0.010 \(\pm\) 0.002 \\ O (wt\%) & 27.4 \(\pm\) 0.5 \\ Ash (wt\%) & 9.4 \(\pm\) 3.4 \\ Volatile solids (wt\%) & 91.0 \(\pm\) 2.8 \\ Cl (wt\%) & 0.3 \(\pm\) 0.2 \\ Hg (mg/MJ) & \(3.8\times 10^{-5}\pm 2.9\times 10^{-5}\) \\ Higher heating value (MJ/kg) & 26.0 \(\pm\) 2.7 \\ Lower heating value (MJ/kg) & 24.3 \(\pm\) 2.6 \\ Bulk density (kg/m\({}^{3}\)) & 58.2 \(\pm\) 2.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characterisation of pelletised solid recovered fuel (SRF) from screening waste. while the cyclone temperature was kept constant at 650 \({}^{\circ}\)C. Calcinated dolomite, sifted at a mesh size of 500 \(\upmu\)m, was utilised as bed material in the reactor. The experiments were carried out over 60 min to ensure the system reached a steady state. The diagram of the gasification plant is shown in Figure 1 [36]. The gasifying agent was atmospheric air (coming from a compressor) or a mixture of air and steam. The feed rate of air was adjusted by a mass flow controller to ensure the ER required for autothermal gasification. When necessary, water was also fed through an HPLC pump; then, it was vaporised (200 \({}^{\circ}\)C) before mixing with the inlet air stream. During the gasification process, gases were retained inside the reactor for 7 to 8 s. After this, the gas stream left the reactor dragging small solid particles, which were collected by a filtration system composed of a cyclone and the hot filter, which were maintained at a constant temperature of 650 \({}^{\circ}\)C and 450 \({}^{\circ}\)C, respectively, thus ensuring only the capture of solid particles. Then, gases and vapours produced during the process were conducted through two condensers (cooled using a water-cooled chiller) and an electrostatic precipitator. A condensed fraction composed of water and organic compounds (tar) was recovered in the condensers. Subsequently, the resulting gas was subjected to an additional filtration step using a cotton filter to remove any particles or aerosols in the gas stream. Once the flue gas had been purified of particulates, it was volumetrically measured and, then, its composition was analysed online using a gas microchromatograph (Agilent 3000-A, Agilent, Santa Clara, CA, USA) to quantify the volumetric fraction of H\({}_{2}\), O\({}_{2}\), CO, CO\({}_{2}\), CH\({}_{4}\), C\({}_{2}\)H\({}_{4}\), C\({}_{2}\)H\({}_{6}\), C\({}_{2}\)H\({}_{2}\), H\({}_{2}\)S, and N\({}_{2}\). The composition of the gas is a consequence of several intricate reactions, among which the most significant ones are presented below:  
Figure 1: Scheme of the experimental gasification setup.