Evolution of pore structure and fractal characteristics of rice husk char particles during gasification

The changes in pore structure and fractal characteristics of rice husk char particles during gasification were studied by N2 physisorption method and scanning electronic microscopy (SEM). The results showed that the adsorption isotherms of rice husk gasified chars were all type II isotherms with hysteresis loops, indicating that the chars consisted of continuous and complete system of pores. As the gasification conversion rate increased, the BET surface area and micropore area first increased to reach the maxima of 210.45 and 147.14 m2/g at the conversion of 48.6% and then decreased. Pore volume showed a similar tendency to BET surface area. The average pore diameter decreased significantly and then increased slowly with increase of gasification conversion rate and reached the minimum of 2.94 nm at the conversion rate of 35.4%. The fractal Frenkel-Halsey-Hill (FHH) model was capable of predicting the pore surface fractal characteristics of the gasified char particles. The evolution of pore surface fractal dimension (Ds) was opposite to that of average pore diameter (dave). There was a good linear relationship between Ds and dave. The results can provide valuable information for the numerical simulation and the optimization of operating parameters of the actual biomass gasification process.