This invention relates to a system for CO2 capture from a combustion flue gas using a CaO/CaCO3 chemical loop, wherein the CO2 is captured from large scale combustion systems using CaO as regenerable CO2 sorbent, where CaO particles are carbonated in contact with a flue gas at around 650° C. to later release pure CO2 when supplied with sufficient heat for CaCO3 calcination at around 900° C., wherein the system of this invention is characterized by a first direct heat exchange from a high temperature flue gas to a recirculation stream of calcined solids from the calciner and/or a second direct heat exchange from a flue gas to the carbonated solids arriving to the calciner, thereby reducing the heat requirements for calcination.