## 3 Results and Discussion
### Effect of Gasification Temperature  
The gasification temperature is a crucial parameter in biomass gasification. In this study, three temperatures ranging between 800 and 900 \({}^{\circ}\)C were investigated, while the steam-to-biomass ratio was fixed at 1.2 for the steam gasification. The effects of gasification temperature on the gas composition (on dry basic and N\({}_{2}\) free) are presented in Figure 4. The simulation results indicate that the content of H\({}_{2}\) increases with elevated temperature, while the CH\({}_{4}\) content decreases considerably. Furthermore, the content of CO rose from 800 to 850 \({}^{\circ}\)C, then dropped down to 21.98% at 900 \({}^{\circ}\)C. It is noteworthy that the CO\({}_{2}\) fraction showed an opposite trend. Moreover, operating temperature also enhanced the gas yield produced and CCE by 1.28 Nm\({}^{3}\)/kg\({}_{\text{biomass}}\) and 51.97% from 800 to 900 \({}^{\circ}\)C, respectively (shown in Figures 5 and 6). A similar trend is observed in the experimental results.  
The effect of operating temperature on the process performance of steam gasification of biomass can be attributed to endothermic and exothermic reactions in biomass gasification [42; 48]. According to [PERSON]'s principle and dynamic equilibrium, the endothermic reactions ((2), (3), and (5)) are strengthened with elevated temperature, increasing the contents of hydrogen and carbon monoxide, while reducing in methane fraction. Additionally, the water-gas shift reaction can be promoted by the high contents of carbon monoxide and steam in the gasifier, resulting in a decline of carbon monoxide in the product gas. These reactions take place simultaneously in the reactor; thus, there is a considerable rise in H\({}_{2}\) content and fluctuations in the values of other components at high temperatures.  
Elevated temperature favors the rate of char gasification reactions and the water-gas shift reaction, which can result in increased dry gas yield and the decreasing unreacted char. Therefore, increasing operating temperature improves biomass conversion and hydrogen production in steam gasification of torrefied biomass.  
Figure 4: Effect of gasification temperature on the gas composition.  
Figure 5: Effect of gasification temperature on the gas yield.  
Data analysis of the effect of gasification temperature is shown in Table 6. The mean errors of H\({}_{2}\) and CH\({}_{4}\) are the lowest and highest values, respectively. These errors are acceptable to predict the performance of the biomass gasification process. The differences between simulation and experimental results in the effect of gasification temperature are due to some simplified calculations and assumptions during the simulation. Biomass produces more tar and heavier hydrocarbons at lower temperatures, and they are decomposed at high temperatures. Tars released during biomass decomposition are assumed to be converted completely into CO and CH\({}_{4}\); therefore, the effect of temperature on tar production and decomposition is generally ignored in this study. Additionally, some reactions, i.e., steam reforming, char combustion, and hydrogen combustion, etc. are not considered in FORTRAN kinetic calculations, resulting in the high content of H\({}_{2}\) and CH\({}_{4}\) and the dry gas yield as well as the low fraction of CO\({}_{2}\) compared to experimental results. The equilibrium assumption replaces methane for all other hydrocarbons in the product gas and a negligible deviation of methane content between simulation and experimental results as observed in Figure 4.