This can be attributed to two reasons:
(1) the critical carbon content value (Ccritical) needed to prevent the high
temperature defluidization is too high, e.g., after pre-reduction process,
the carbon content of a pre-reduced iron ore needs to exceed 13–
14 wt.% to totally avoid defluidization; (2) carbon accumulation during
the subsequent high temperature reduction process, e.g., the carbon
content of DRI further increased from 13.3 wt.% to 22.3 wt.% after reduc-
tion at 800 °C for 100 min as reported by D. Neuschütz