Effect of pyrolysis temperature on pine sawdust chars and their gasification reactivity mechanism with CO₂

The mechanism on CO₂ gasification reactivity of pine sawdust chars (PS chars) obtained from the different pyrolysis temperatures (873, 973, and 1073 K) is studied on the basis of nonisothermal thermogravimetric method. The order of gasification reactivity is PS char-873 > PS char-973 > PS char-1073. The effect of pyrolysis temperature is depicted by microstructure characterization, and the gasification reactivity is analyzed with nonisothermal kinetic models. The microstructure characterizations of chars are characterized by scanning electron micrograph, Brunauer–Emmett–Teller, Fourier transform infrared, and X-ray diffraction. Results show that the microcrystalline structure of biomass char is the dominant factor for the effect of gasification reactivity with the pyrolysis temperature rising. The kinetic models of Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose are applied to describe the kinetics of gasification process. The average values of activation energy are in close agreement with the two methods. Both of the methods prove that F2 mechanism is applicable to the gasification of PS chars at lower pyrolysis temperature and F1 mechanism at higher pyrolysis temperature. Besides, there is a compensation effect between activation energy and preexponential factor in the CO₂ gasification process.