Empirical kinetic model of a stone dust looping carbonator for ventilation air methane abatement

A novel stone dust looping (SDL) process for mitigation of ventilation air methane (VAM) was investigated. The SDL process uses limestone as a sorbent to capture CO2 emissions, similar to a conventional calcium looping (CCL) process. However, unlike CCL where lime (CaO) is introduced directly to a flue gas from a thermal power plant with CO2 concentrations as high as 12-15% in an oxygen-deficient environment, the SDL process uses CaO to catalytically oxidize VAM, with concentrations of CH4 up to 0.1-1 vol % in air, and simultaneously capture CO2 produced. In the present study, kinetic parameters were derived from experiments in a single lab-scale fluidized bed reactor. A random pore model (RPM) was used to determine the rate-controlling steps for the SDL process, and kinetic parameters, such as activation energy (EaK) and pre-exponential factor (ks0), were obtained for a SDL process carbonator. Kinetic parameters were then used to derive an empirical model for a continuous SDL process and consisted of residence time distribution functions, sorbent kinetics, and deactivation rate. The empirical model has the ability to simulate and predict various operating and design conditions under which the real SDL process will operate. From the model, the optimum bed inventory, solid circulation rates, and stone dust makeup rates have been calculated to achieve the desired CO2 capture efficiency.