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Calcium looping is a promising carbon capture technology, circulating CaO-based sorbents between carbonator and calciner units. Natural limestone is a popular choice for the sorbent material due to its abundance and low cost. However, rapid sorbent deactivation is a major challenge to the long-term stable operation of the calcium looping system. Previous studies have mostly focused on the decay of utilization of fully calcined sorbents over multiple cycles of carbonation/calcination. However, lime-based sorbents are rarely fully calcined in practical operations and, hence, the effect of partial calcination on sorbent cyclic performance is of interest.

This work investigates the effect of the extent of limestone calcination on sorbent utilization decay over multiple cycles. Greymont limestone particles (510-700 µm in diameter) were calcined and carbonated for 20 successive cycles in a thermogravimetric analyzer (TGA). The extent of calcination was varied by changing the calcination time, with the calcination time being fixed for each cyclic test. It was observed that partial calcination results in enhanced sorbent utilization over the testing cycles. The experimental results give better understanding of the mechanism of sorbent utilization decay, while also providing more experimental support for prospective calcination kinetics modelling. Future study will verify the observed effects of partial calcination for prolonged numbers of cycles and different calcination operating conditions.