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 mu m) aligned along the grain direction collapse after the gasification and generate numerous micropores in biochar samples. 10-20 mu m 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.