(176e) A Model of Transient Thermal Transport Phenomena Applied to the Carbonation and Calcination of a Sorbent Particle for Calcium Oxide Looping CO2 Capture

A numerical model coupling transient radiative, convective, and conductive heat transfer and mass transfer to chemical kinetics of heterogeneous solid−gas reactions has been developed for a semi-transparent, non-uniform, and non-isothermal particle undergoing cyclic thermochemical transformations. The thermochemical calcination−carbonation reaction pair for calcium oxide looping is selected as the model cycle because of its suitability for use with concentrated solar radiation for the capture of carbon dioxide:

Non-solar, exothermic step: CaO + CO₂ → CaCO₃

Solar, endothermic step: CaCO₃ → CaO + CO₂

The analyzed system is a single, porous particle in an idealized, reactor-like environment. Mass and energy conservation equations for the system are solved numerically for the solid and gas phases using the finite volume method and the explicit Euler time integration scheme. Time-periodic boundary conditions for high-flux solar irradiation and the external gas species concentrations are applied. The model predicts the time-dependent temperature distribution, extents of the calcination and carbonation reactions, and consequently the overall amount of carbon dioxde captured by the single particle over a cycle as a function of physical parameters and reactor operating conditions. Results support the potential of calcium based sorbents and calcium oxide looping for carbon dioxide capture and provide input to the design of a solar reactor for the implementation of calcium oxide looping for carbon dioxide capture.