Effect of torrefaction pretreatment on biomass chemical looping gasification (BCLG) characteristics: Gaseous products distribution and kinetic analysis

The biomass chemical looping gasification (BCLG) of torrefied spruce-pine-fir (SPF) sawdust with Fe₂O₃ was studied using thermogravimetry-mass spectrometry (TG-MS). The effects of torrefaction temperature and OC ratio on the BCLG were investigated. The thermal characteristics of torrefied SPF with Fe₂O₃ and the distribution of gaseous products were discussed. Thermogravimetric kinetics and gas release kinetics were implemented to understand the mechanism. The results showed the volatiles release intensity of the SPF reached the maximum when the torrefaction temperature was 270 °C. The solid–solid reaction performance between OC and biochar reached the highest as the OC fraction was 50 wt%. The thermogravimetric kinetics revealed the activation energy of the BCLG gained the minimum when the OC ratio was 50 wt%. Moreover, the increase of OC ratio and torrefaction temperature could improve the reactivity of biochar. The torrefaction affected the gaseous products distribution of the BCLG, which consequently promoted the H₂/CO ratio of the syngas from 1.06 to 1.30. Meanwhile, the gas release kinetic analysis demonstrated the E(H₂) made the minimum (88.66 kJ·mol⁻¹) when the torrefaction temperature was 270 °C. All these indicate the torrefaction has a positive effect on the BCLG process.