Heat storage technologies are used to improve energy efficiency of power plants and recovery of process heat. Storing thermal energy by reversible thermo-chemical reactions offers a promising option for high storage capacities especially at high temperatures. Due to its low material cost the use of the gas-solid reaction Ca(OH)(2) reversible arrow CaO + H2O has been suggested. In Part A of this work the thermal behavior of a reactor with direct heat transfer was experimentally investigated. In this part a two-dimensional model is applied for the specified system. The experimental and simulated results during the exothermic hydration are discussed in order to confirm the validity of the model. The model is validated regarding heat transfer, integral reaction rate and maximum temperatures. In addition, an adaptation of the kinetic equation is proposed in order to take into account rate-limiting effects due to agglomeration in the powder bed. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.