Process for producing a cement clinker at low temperature

The invention provides a process for producing a cement clinker comprising: (i) mixing one or more starting materials providing each at least one or more of CaO, SiO 2 , Al 2 O 3 , and Fe 2 O 3 ; and, optionally, SO 3 , to form a raw meal comprising CaO, SiO 2 , Al 2 O 3 , and Fe 2 O 3 ; and, optionally, SO 3 , wherein the molar ratios among the aforementioned oxides is given by Formula I: (CaO) 1 (SiO 2 ) a (Al 2 O 3 ) b (Fe 2 O 3 ) c (SO 3 ) d , wherein: "a" is comprised from 0.05 to 1, "b" is comprised from 0.1 to 0.6, "c" is comprised from 0.001 to 0.25, and "d" is comprised from 0 to 0.3; (ii) heating the raw meal by irradiating with microwaves during 15 min to 3 h to reach a sintering temperature comprised from 300 to 950 °C; (iii) maintaining the microvawe sintering temperature of step (ii) during 1 min to 3 h by further irradiating with microwaves; and (iv) cooling the clinker obtained in step (iii).