Effect of torrefaction on the evolution of carbon and nitrogen during chemical looping gasification of rapeseed cake

• Torrefaction is an effective pretreatment for rapeseed cake upgrading. • The nitrogen functionalities significantly decrease with torrefaction. • Torrefaction enhances the CLG behavior of rapeseed cake. • Torrefaction combined with CLG marginally reduces NH 3 and HCN. Chemical looping gasification (CLG) is a novel approach to efficiently convert rapeseed cake (RC) to tunable syngas and NH 3 . However, the low energy density of RC seriously hinders its utilization. Meanwhile, torrefaction is an effective pretreatment for biomass upgrading. Hence, the combination of torrefaction with CLG is proposed as an alternative technology to efficiently utilize RC. In this work, the effect of torrefaction temperature on the evolution behaviors of carbon and nitrogen in CLG of RC with Ca 2 Fe 2 O 5 OC was systematically investigated using TG-FTIR. Results show that torrefaction can effectively improve the physiochemical properties of RC. The torrefied RC possesses higher energy density and HHV, and lower atomic H/C and O/C ratios. Additionally, higher torrefaction temperature can facilitate the thermal degradations of N-IN and labile N-P, with the productions of NH 3 and HCN. During CLG, the rise of OC/Fuel mass ratio can increase the yields of the major gases (CO 2 , CO, CH 4 , NH 3 and HCN), owing to both the oxidative effect of the lattice oxygen (O*) and the catalytic effects of Fe 3+ and Ca 2+ in OC. Moreover, torrefaction pretreatment can improve the CLG behavior of RC and the optimal torrefaction temperature is 250 o C, attributing to the improvement of fuel stability after torrefaction. Besides, torrefaction can marginally reduce the yields of the major nitrogen species (NH 3 and HCN). This is ascribed to both the more stable structure of heterocyclic-N and the insufficiency of H radical in the torrefied RC compared to the raw. These findings provide a feasible guidance for the effective insight in nitrogen evolution during CLG coupled with torrefaction, and thereafter for the efficient utilization of biomass.