Synergistic effect of torrefaction and gasification temperatures on hydrogen-rich syngas quality from steam gasification of cornstalk-derived biochar

Steam gasification of cornstalk and torrefied biochar was conducted in a fixed bed chamber to investigate the quantitative and qualitative characteristics of hydrogen-rich syngas. Emphasis was placed on H₂ and CO production, considering the varied temperatures of torrefaction and gasification and their synergetic effects. The study reports the production of syngas and tar, along with calculations of calorific value and carbon conversion rate. Experimental results indicated that the H₂ content, syngas production, and carbon conversion rate from cornstalk gasification improved with increasing reaction temperature. The carbonization level of cornstalk through torrefaction pretreatment was examined. Subsequently, the analysis of syngas composition from torrefied biochar gasification revealed that the maximum H₂ content was identified at the highest torrefaction temperature (290 °C), not the highest gasification temperature (950 °C). Conversely, the maximum production of syngas and carbon conversion rate were obtained at the highest gasification temperature, not the highest torrefaction temperature. Furthermore, the calorific value of syngas decreased with lower CH₄ + C_xH_y content under higher torrefaction and gasification temperatures. In conclusion, achieving a balance between H₂ content and gas production can be facilitated by considering torrefaction pretreatment in the steam gasification process.