Catalytic gasification of large particle-size biomass with loaded AAEMs under oxygen-steam atmosphere

To evaluate the effect of alkali and alkaline earth metals (AAEMs) species on the catalytic gasification of large particle-size biomass, a vertical fixed-bed reactor is conducted for candlenut wood gasification under the oxygen-stream atmosphere. The biochar samples derived from gasification are characterized by SEM, X-ray CT, BET, and FTIR. Tar and syngas are analyzed via GC–MS and GC respectively. Advanced X-ray CT technology provides beneficial visualization to assist in the interpretation of the catalytic gasification of large particle-size biomass loaded with AAEMs. The results indicate that a progressive augmentation of AAEMs content along the radial direction and end surface for all loaded samples and biochar samples, which could also be visualized from the 3D reconstruction of X-ray CT. Many large pores (40–60 μm) aligned along the grain direction collapse after the gasification and generate numerous micropores in biochar samples. 10–20 μm pores are more prominent in biochar as the biomass samples are loaded with KCl and CaCl2. The biochar from gasification of biomass loaded with CaCl2 has more well-developed pores, a larger specific surface area, and –OH compounds, aldehydes, ketones and carboxylic acids. The addition of AAEMs facilitates the high generation of M1 compounds (contains 1 benzene ring) in the tar and suppresses the enhancement of M4 compounds, long-chain alkanes, and other compounds. The lowest carbon conversion (57.12 %) is acquired from acid-washed sample. H2 concentration augments but CO concentration declines by loading AAEMs. The highest H2 concentration of 62.1 % is detected by the addition of CaCl2. When loaded with KCl, the syngas calorific value reduces by 1.37 %, whereas loaded with NaCl, CaCl2, and MgCl2 show an augmentation of 11.48 %, 10.56 %, and 2.55 %, respectively. A decrement of CnHx concentration in the syngas derived from gasification of biomass samples loaded with KCl and MgCl2 and an increment one loaded with NaCl and CaCl2 are acquired.