The ash produced during oil shale combustion is classified as waste, however, one could also view it as a low-cost source of lime for the abatement of SO2 and CO2 emissions as well as for the commercial production of precipitated calcium carbonate (PCC)-type filler material. This study focuses on the dissolution mechanisms of the main water-soluble calcium species in oil shale ash-water systems. Reaction models that describe the dissolution of Ca(OH)(2) and CaSO4 center dot 2H(2)O in water were developed and the kinetic parameters of the proposed system composed of differential equations were estimated by optimizing the model reproduction of experimental data. The dissolution kinetics of Ca(OH)(2) and CaSO4 center dot 2H(2)O were also simulated using the Aspen Plus process modeling platform. (C) 2015 Elsevier B.V. All rights reserved.