Devolatilization of Residual Biomasses for Chemical Looping Gasification in Fluidized Beds Made Up of Oxygen-Carriers

The chemical looping gasification of residual biomasses—operated in fluidized beds composed of oxygen-carriers—may allow the production of biofuels from syngas. This biomass-to-fuel chain can contribute to mitigate climate change, avoiding the accumulation of greenhouse gases in our atmosphere. The ongoing European research project Horizon2020 CLARA (G.A. 817841) investigates wheat-straw-pellets (WSP) and raw-pine-forest-residue (RPR) pellets as feedstocks for chemical looping gasification. This work presents experimental results from devolatilizations of WSP and RPR, in bubbling beds made of three different oxygen-carriers or sand (inert reference), at 700, 800, 900 °C. Devolatilization is a key step of gasification, influencing syngas quality and quantity. Tests were performed at laboratory-scale, by a quartz reactor (fluidizing agent: N 2 ). For each pellet, collected data allowed the quantification of released gases (H 2 , CO, CO 2 , CH 4 , hydrocarbons) and mass balances, to obtain gas yield ( η av ), carbon conversion ( χ av C ), H 2 /CO ratio ( λ av ) and syngas composition. A simplified single-first order-reaction model was adopted to kinetically analyze experimental data. WSP performed as RPR; this is a good indication, considering that RPR is similar to commercial pellets. Temperature is the dominating parameter: at 900 °C, the highest quality and quantity of syngas was obtained (WSP: η av = 0.035–0.042 mol gas g biomass −1 , χ av C = 73–83%, λ av = 0.8–1.0); RPR: η av = 0.036–0.041 mol gas g biomass −1 , χ av C = 67–71%, λ av = 0.9–1.0), and oxygen-carries generally performed better than sand. The kinetic analysis suggested that the oxygen-carrier ilmenite ensured the fastest conversion of C and H atoms into gases, at tested conditions.