還元鉄の CO-CO_2 混合ガスによる炭化速度

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The carbidization rate of iron ore was thermo-gravimetrically measured and analyzed with CO-CO_2 gas mixtures from 873K to 1073K, after it was completely reduced with H_2 gas containing sulfur low enough not to form sulfide. The fractional carbidization is defined as the mass gain relative to the mass of carbon required converting whole of iron to cementite, θ-Fe_3C. The reaction was composed of three stages : (1) Carbon was supersaturated in α-iron. (2) The fractional carbidization increased linearly after the nucleation of cementite, until it was saturated. The sulfur, which was adsorbed on the pore surface in iron ore, stabilized cementite and prevented free carbon from deposition. (3) However, at 873K and 1073K, free carbon deposited and mass gain was accelerated at a certain fractional carbidization. This phenomenon is a kind of percarbidization of cementite without formation of percarbide, χ-Fe_5C_2. Carbide was decomposed into free carbon and metal and then iron ore was broken to powder, that is so-called 'metal dusting'. The authors considered that the slope of straight line portion during the growth of carbide is the carbidization rate from 873K to 1023K, which contained no error of mass changes due to reduction and carbon deposition. The carbidization rate was formulated as a function of relative partial pressure of CO and CO_2, P_<CO>, P_<CO_2> [-] and temperature, which is controlled by the following elementary reactions, CO+□=C__-+O(ad) CO+O(ad)=CO_2.
1999-01-01

還元鉄の CO-CO_2 混合ガスによる炭化速度

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