Calcium looping technology is considered to be one of the most feasible techniques for CO2 capture. A low-cost and easy method was proposed to improve the cyclic CO2 capture capacity of the limestone by discontinuously adding hydrogen chloride (HC1) in the carbonation step in some cycles rather than in the each cycle at the calcium looping conditions. The effects of the discontinuous addition of HCI under the various conditions on the CO2 capture performance of the limestone at the calcium looping conditions were investigated in a dual fixed-bed reactor. The results show that HCI addition during the initial several cycles leads to the formation of CaCIOH and the moderate CaCIOH in the carbonation product is favorable to CO2 capture by the limestone. HCI addition only in the initial 3 cycles changes the effect of carbonation temperature on CO2 capture by the limestone. The optimum carbonation temperature for the limestone with the addition of HCI is 700 degrees C in the range of 650-750 degrees C. Higher CO2 volume fraction in the carbonation leads to lower CO2 capture capacity of the limestone with the addition of HCI only in the initial 3 cycles. The discontinuous addition of HC1 during the various cycles significantly enhances the CO2 capture capacity Of the limestone. HC1 addition in the carbonation stage during only the initial cycles improves the pore structure of the calcined limestone and retards the fusion of CaO grains, which contributes to high CO2 capture capacity of the sorbent in the multiple cycles. (C) 2017 Elsevier B.V. All rights reserved.