## 2 Materials and Methods
### Description of the Operational Procedure  
Before the experimental tests began, several checking and switching tasks were performed. Once the leak check was done, the plant started to be heated. For this, an air stream was circulated, the resistors of the reactor and the air preheater (350 \({}^{\circ}\)C) were activated, and the cooling apparatus (4 \({}^{\circ}\)C), prior to the final filter, was connected. When the reactor temperature was 50 \({}^{\circ}\)C below the standard temperature (750, 800, 850, or 900 \({}^{\circ}\)C),  
Figure 1: Schematic representation of the biomass gasification plant.  
the hose feeder (250 g/h) that had been previously inserted into the feeding pipe was triggered. Once the temperature and gas composition were stable (measured firstly with a portable gas analyzer, MRU-Vario Luxx, MRU Instruments, Inc., Humble, TX, USA), the determination of the composition of the exhaust gas was performed with an Agilent 990 Micro GC (Agilent, Santa Clara, CA, USA). Three measurements were made at intervals of 5 min, and the values were recorded for the subsequent calculation of the mean values. For each temperature, three experiments were carried out, keeping the flow rate constant, and varying the air rate to three levels of equivalence ratio (0.1, 0.3, and 0.5).  
The equivalence ratio (ER) defines the ratio of the mass of the oxidant to the mass of fuel divided by the oxidant stoichiometrically required per unit mass of dry feedstock. It expresses the quantity of air used as a proportion of the stoichiometric air requirements used to gasify a given unit of fuel. In this work, to establish the chosen equivalence ratios of 0.1, 0.3, and 0.5, air flows were varied between 0.13 Nm\({}^{3}\)/h and 0.67 Nm\({}^{3}\)/h for a flow of 0.25 kg/h of olive cake.  
Cold gas gasification efficiency, defined as the ability of the reaction system to harness the energy available in the biomass and convert it into energy available in the gas, was calculated according to the Equation (1) as the ratio of output gas energy to the input feed energy:  
\[\eta_{\text{ICG}}=\frac{\text{V}_{\text{g}}\cdot\text{LHV}_{\text{gas}}}{\text {m}_{\text{fuel}}\cdot\text{LHV}_{\text{fuel}}} \tag{1}\]  
where \(\eta_{\text{ICG}}\) is the cold gas efficiency, \(\text{V}_{\text{g}}\) the volume flow of exit gas (Nm\({}^{3}\)/h), LHV\({}_{\text{gas}}\) the lower heating value of the exit gas (MJ/Nm\({}^{3}\)), LHV\({}_{\text{fuel}}\) the lower heating value of the solid fuel (MJ/kg), and m\({}_{\text{fuel}}\) the mass flow of solid fuel (kg/h).  
The fluidization process was achieved using quartz sand with a mean particle size of 200 \(\upmu\)m. The gas flow was introduced through a perforated plate located at the base of the reactor to ensure uniform distribution and stable fluidization.  
Liquid residues were sampled directly from the gasification system at designated collection points. Specifically, the sampling was conducted from the condensate collection unit, which is positioned downstream of the gasifier where the syngas cools and condenses. This unit is equipped with sampling ports to ensure a representative collection of the liquid phase.  
The solid residues were collected from three key locations within the gasification system: (1) the fluidized bed reactor, (2) the cyclone, and (3) the gas filter unit. The fluidized bed reactor includes an ash collection system at the bottom to collect the ashes generated during the gasification process. After each experiment, a manual ash removal mechanism was executed. Also, the ash was recovered from the cyclone and gas filter unit sited at the end of the installation.