A population balance model of sorbent conversion and attrition in a fluidized bed calcium looping process.

A population balance model on sorbents in a fluidized bed Ca-looping process is presented. The model is based on material balances on the sorbent as it is recirculated between the calciner and the carbonator. The course of carbonation is modelled by assuming well stirred behaviour of the carbonator with a suitable expression for the rate of CO2 uptake. Sorbent regeneration is modelled under the assumption of extremely fast calcination. The occurrence of sorbent attrition/fragmentation phenomena is considered to account for modifications in the particle size distribution during both calcination and carbonation, with purposely derived constitutive models validated against results of a parallel experimental campaign. The influences of relevant process parameters on the degree of particle carbonation, on the CO2 capture efficiency, on the rate of sorbent elutriation and on the thermal power demand associated with regeneration of the sorbent in the calciner are assessed.