A nanoscale model for characterizing the complex pore structure of biochars

The development of a novel nanoscale model that can accurately describe the reactivity of solids consisting of multiple components and having ordered and random pores is presented. Domains of multiple solid phases are distributed on a computational grid to simulate reactants with different specific reactivities and dispersions. Sub-nanometer slit pores and larger cylindrical pores with given size distributions are also distributed on the grid in regular and random arrangements respectively. The generated solids are then eroded using rules that simulate a gas-solid, non-catalytic reaction occurring in the kinetic control regime. A parametric study is first carried out to demonstrate how key pore structural parameters affect the reactivity patterns. Model predictions are found to be in excellent agreement with experimental thermogravimetric data for the combustion of biochars, both when the slit and random cylindrical pores are fully accessible to the reactant and when diffusional limitations appear in the smaller slit pores. (c) 2013 American Institute of Chemical Engineers AIChE J, 59: 3412-3420, 2013