Pretreated residual biomasses in fluidized beds for chemical looping Gasification: Experimental devolatilizations and characterization of ashes behavior

The European research project CLARA (G.A. 817841) has studied pretreated residual biomasses for chemical looping gasification. This work investigated devolatilizations of wheat straw pellets (raw, torrefied, and torrefied-washed) at 700 °C, 800 °C, and 900 °C, performed in fluidized beds made of sand or three oxygen carriers (OCs): integral-average values (gas yield, H₂/CO molar ratio, and carbon conversion) were calculated; instantaneous peaks of released syngas were evaluated by regression straight lines. For all biomasses and bed materials, the temperature increase (from 700 to 900 °C) was the dominant parameter, positively affecting all integral-average values. The OCs appeared more active at 900 °C. Biomass pretreatments improved the H₂/CO molar ratio and decreased carbon conversion. SEM analyses showed that the purpose of washing (removal of low-melting elements) may be jeopardized by OCs' composition.