Modelling Full Cycles of Carbonation-Calcination for Calcium Looping Process Simulation

This work is part of a study to develop a multi-scale model of a Ca-looping (CaL) post-combustion process for CO2 capture that relies on the carbonation reaction of CaO (s) and on the calcination of the resulting CaCO3 (s) to generate a stream of highly concentrated CO2 (g). The literature lacks models that combine the modelling of both reactions with a cyclic structure that accounts for sorbent deactivation and allows for a realistic estimation in the case of incomplete reactions or different reaction media. Therefore, in this work two sub-models are combined to form this novel modelling approach for the simulation of complete carbonation-calcination cycles of the CaL process: The overlapping grain model for the carbonation reaction, and a proposed modified version (mRThPSD) of the rate equation theory for the pore size distribution (PSD) of calcined CaCO3 (RThPSD) for the calcination. The cyclic structure accounting for sorbent deactivation present in the proposed model was justified using data from fixed bed reactor experiments which highlights the relationship between loss of superficial area of CaO sorbents and loss of reactivity. The model was implemented in gPROMS ModelBuilder (R) software and was validated with data from fixed bed reactor experiments for different CaL sorbents. One full CaL cycle was simulated successfully for dolomite, with the model estimating both reactions profiles and changes to the calcinated particle PSD with errors below 3%.