LAUSR

Abstract A 3D Random Pore Model (3D-RPM) has been derived to predict the growth of porosity for isothermal interface-controlled oxidation (gasification) reactions occurring in graphite with open porosity. Compared to previous 2D-RPMs based on overlapping parallel cylindrical pores, the 3D-RPM assumes pores are overlapping spheres, creating an isotropic pore microstructure. Both models predict a maximum in reaction rate over the course of reaction. It is shown that the pore volume fraction corresponding to the reaction rate maximum is independent of model parameters and is 0.39 and 0.49 for the 2D and 3D model, respectively. Furthermore, changing the pore size input parameter by an order of magnitude changes the reaction rates by an order of magnitude. Importantly, 2D versus 3D pore growth can be distinguished on a linearized plot of pore volume growth data, by whether the slope of the line is two or three, respectively. When compared with experimental oxidation data, the 3D model matched the measured 3D growth order and peak oxidation rates, but over-predicted the initial oxidation rates, presumably in part due to neglecting initially closed pores that become open during oxidation. Future publications will extend the model to include initial closed porosity that opens over time as well as sample size effects.