The sorption reaction CaO-CO2 was examined in a countercurrent gas-solid trickle flow reactor with regularly stacked packing at T=500-600 degrees C, p(CO2)=40-50 kPa, solid-phase fluxes S=0.3-0.5 kg m(-2) s(-1), and CaO particles of 500-710 m in size. Sorption kinetics was evaluated by thermogravimetric (TG) technique. The random pore model was used for the description of the carbonization reaction. Hydrodynamic characteristics of gas-solid trickle flow were estimated at room temperature and ambient pressure. Plug flow model of both gas and solid-phase, with the parameters obtained from TG and hydrodynamics experiments, satisfactorily described the sorption process in countercurrent gas-solid trickle flow reactor. (c) 2015 American Institute of Chemical Engineers AIChE J, 61: 1601-1612, 2015