Equilibrium and Kinetic Studies Carbon Dioxide Capturing on Ca-Based Sorbents

The increase of atmospheric carbon dioxide concentrations in recent years is well documented. Its potential link to an earth wide greenhouse-like effect has led recently to tighter regulations on carbon dioxide emissions from various industrial sources. One of the most common emitters is the fossil fuel based energy production industry which generates high temperature streams containing carbon dioxide at the exit of fossil fuel combustion processes.

We consider the removal of carbon dioxide from high temperature water-air mixtures using calcium-based sorbents. It has been experimentally shown in our prior work that CaO/Zr nanostructured sorbents possess a consistently high capacity to capture carbon dioxide over several high temperature carbonation/decarbonation cycles. In this work, we provide theoretical support for these experimental results by carrying out both equilibrium and kinetic studies. First, we carry out equilibrium calculations by solving to global optimality a Gibbs free energy minimization problem for the multiphase system: N2, O2, CO2, H2O, CaO, CaCO3, Ca(OH)2. Then, we formulate a simple semibatch reactor model for a thermogravimetric analysis (TGA) apparatus in which the carbonation process is carried out. The predictions of the resulting ordinary differential equation based kinetic model for the CaO adsorption process are compared to TGA obtained experimental data.