Numerical study on the gasification and shape evolution of single rod-shaped biomass char particle in a hot CO₂/O₂/H₂O atmosphere

In the industrial systems for CO2 gasification of biomass, a large amount of feedstock is presented as rod-shaped particles at different scales. The evolution of such particles during gasification remains unclear. This work investigated the overall gasification characteristics of single rod-shaped biomass char particle in a hot CO2/O2/ H2O atmosphere and the intrinsic link between shape evolution and gasification characteristics. The overall gasification characteristics of the particle are discussed, including the influence of various inlet parameters and geometric parameters. The reaction intensity on the particle surface shows significant non-uniformity, which increases with the particle Reynolds number and oxygen concentration but decreases with increasing inlet temperature. The more the particle shape resembles a rod (aspect ratio ranging from 3:2 to 3:1), the more pronounced the non-uniformity of the surface temperature becomes (increasing by over five times). The intrinsic link between particle reaction properties and shape evolution was discussed using the dynamic mesh method. The shrinkage rate at the end of the particle is 1.73 times faster than that at the middle part. The non-uniformity of the surface temperature decreases by 6 % within 5 s, indicating that as the reaction proceeds, the reaction intensity on the particle surface tends to become more uniform.