A direct reduction system for a direct reduction of iron oxides comprising a gas circulation circuit comprising: - a reactor having a reduction area adapted for being loaded with said iron oxides; - a first external source of make-up gaseous hydrogen-containing gas with a gaseous hydrogen gas content equal to at least 80% in volume; - a second external source of make-up gaseous hydrocarbon-containing gas, preferably with a gaseous hydrocarbon content equal to at least 25% in volume; - a recovery and treatment line, placed downstream of the reactor, for recovering and treating the exhaust gas exiting the reactor; - a treatment and feeding line, placed upstream of the reactor, for treating a process gas, obtained by mixing the make-up gaseous hydrogen-containing gas coming from the first external source and/or the make-up gaseous hydrocarbon-containing gas coming from the second external source with the exhaust gas treated in the recovery and treatment line, and for feeding the reduction area of the reactor with said process gas; wherein the recovery and treatment line communicates downstream with said treatment and feeding line; wherein the recovery and treatment line comprises at least one first heat-exchange device where heat is transferred from the exhaust gas to a heat-transfer fluid; wherein the treatment and feeding line comprises at least one second heat-exchange device; wherein a duct, able to carry the heat-transfer fluid, connects the at least one first heat-exchange device to the at least one second heat-exchange device whereby the heat of the heat-transfer fluid can be transferred to said process gas by means of said at least one second heat-exchange device; wherein the recovery and treatment line also comprises at least one carbon dioxide removal device for removing carbon dioxide from the exhaust gas; wherein the duct has a branch connecting said duct to the at least one carbon dioxide removal device whereby the heat of the heat-transfer fluid can be completely or partially transferred to said at least one carbon dioxide removal device; and wherein said first external source and said second external source are connected to said treatment and feeding line or to said recovery and treatment line. - a reactor having a reduction area adapted for being loaded with said iron oxides; - a first external source of make-up gaseous hydrogen-containing gas with a gaseous hydrogen gas content equal to at least 80% in volume; - a second external source of make-up gaseous hydrocarbon-containing gas, preferably with a gaseous hydrocarbon content equal to at least 25% in volume; - a recovery and treatment line, placed downstream of the reactor, for recovering and treating the exhaust gas exiting the reactor; - a treatment and feeding line, placed upstream of the reactor, for treating a process gas, obtained by mixing the make-up gaseous hydrogen-containing gas coming from the first external source and/or the make-up gaseous hydrocarbon-containing gas coming from the second external source with the exhaust gas treated in the recovery and treatment line, and for feeding the reduction area of the reactor with said process gas; wherein the recovery and treatment line communicates downstream with said treatment and feeding line; wherein the recovery and treatment line comprises at least one first heat-exchange device where heat is transferred from the exhaust gas to a heat-transfer fluid; wherein the treatment and feeding line comprises at least one second heat-exchange device; wherein a duct, able to carry the heat-transfer fluid, connects the at least one first heat-exchange device to the at least one second heat-exchange device whereby the heat of the heat-transfer fluid can be transferred to said process gas by means of said at least one second heat-exchange device; wherein the recovery and treatment line also comprises at least one carbon dioxide removal device for removing carbon dioxide from the exhaust gas; wherein the duct has a branch connecting said duct to the at least one carbon dioxide removal device whereby the heat of the heat-transfer fluid can be completely or partially transferred to said at least one carbon dioxide removal device; and wherein said first external source and said second external source are connected to said treatment and feeding line or to said recovery and treatment line.