A numerical model of transient thermal transport phenomena in a high-temperature solid-gas reacting system for CO2 capture applications

A numerical model coupling transient radiative, convective, and conductive heat transfer, mass transfer, and chemical kinetics of a heterogeneous solid-gas reacting system has been developed and applied to a model reaction: the decomposition of calcium carbonate into calcium oxide and carbon dioxide. The model reaction is one of two reactions involved in calcium oxide looping, a proposed thermochemical process suitable for use with concentrated solar radiation for the capture of carbon dioxide. The analyzed system is a single, porous particle in an idealized, reactor-like environment that is subjected to concentrated solar irradiation. The finite volume and explicit Euler methods are used to solve volume-averaged governing equations numerically. The model predicts the time-dependent temperature distributions as well as local solid and fluid phase composition. For the baseline simulation, complete decomposition of a 2.5 mm radius particle exposed to 1 MW m−2 solar irradiation is reached in 35 s. The model is further used to investigate physical parameters and operating conditions under which solar-driven calcium oxide looping may be employed for carbon capture. Time to complete conversion decreases under conditions favorable for increased rate of heating, such as optimum particle size and increased incident irradiation.