Carbon deposition conditions on metallic iron from CO-CO₂ mixture

Carbon deposition from CO-CO₂ mixture is examined on metallic iron at temperatures ranging from 650 to 950K. The CO-CO₂ mixture was introduced in an alumina tube, in which the high purity electrolytic iron powder was packed, and the ingoing and the outgoing gas compositions were measured by a quadrupole mass spectrometer. The lowering limit of the partial pressure of CO (P_CO/(P_CO+P_CO2)), at which the carbon deposition substantially occurs, is investigated. The condition, under which carbon deposition occurs, is clarified in Fe-C-O system. The improvement of the gas utilization ratio in the reduction of iron oxide and the suppression of dioxins formation in combustion processes by the enhancement of carbon deposition are discussed. From the present thermodynamic calculation, it is concluded that dioxins formation can be suppressed by lowering the P_CO/(P_CO+P_CO2) value under 0.2 to 0.3 according to the enhancement of the carbon deposition at 700 to 750K.