A numerical model coupling transient radiative, convective, and conductive heat transfer, mass transfer, and chemical kinetics of heterogeneous solid-gas reactions has been developed for a semitransparent, nonuniform, and nonisothermal particle undergoing cyclic thermochemical transformations. The calcination-carbonation reaction pair for calcium oxide looping is selected as the model cycle because of its suitability for solar-driven carbon dioxide capture. The analyzed system is a single, porous particle undergoing thermochemical cycling in an idealized, reactor-like environment. The model is used to investigate two cases distinguished by the length of the calcination and carbonation periods. The calcination-carbonation process for a single particle is shown to become periodic after three cycles. (c) 2015 American Institute of Chemical Engineers AIChE J, 61: 2647-2656, 2015