Study On The Kinetics Of Slab Oxidation Process Under Oxygen-enriched Combustion Atmosphere

As an efficient and energy-saving combustion technology,oxygen-enriched combustion technology is used more and more widely.When the billet is heated by oxygen-enriched combustion,the atmosphere and temperature in the furnace are different from normal flue gas,wich also affects the formation of iron oxide scale on the billet surface.The formation of iron oxide scale on the billet surface not only wastes energy,but also affects the quality.of the product.Therefore,in this paper,the formation and kinetic curve of iron oxide scale of billet under different atmosphere and temperature were studied by means of constant temperature kinetic experiment and surface morphology and composition characterization.the conclusions are as follows:(1)In the process of billet oxidation,the higher the billet surface temperature is,the faster the billet oxidation rate is,and the effect of the temperature in the high temperature section on the billet oxidation is stronger than that in the low temperature section.When the billet is oxidized at high temperature,the higher the oxygenenriched concentration of the combustion-supporting air is,the faster the oxidation rate is,but the effect of oxygen-rich concentration on the billet oxidation is weakened under the high oxygen-rich concentration.(2)When the oxidation temperature of the billet is higher or the oxidizing atmosphere is stronger,the thicker the oxide layer formed on the surface of the oxide layer is,and the change trend of the oxide film thickness is consistent with the oxidation weight gain,which can represent the oxidation trend of the billet.The oxide layer with oxidation temperature above 1000℃ has a two-layer structure.The outer surface of the oxide layer is composed of Fe3O4 and Fe2O3,and the composition of the inner surface is FeO.(3)When the heating temperature is 800℃,the surface of the oxide layer is enriched with oxygen elements,the inward diffusion of oxygen elements is suppressed,and Fe2O3 on the outer surface of the slab grows in the form of columnar crystal particles.At high temperature,the size particles gradually increase,and in a local area,they grow into a knitted structure and transform into Fe3O4.After increasing the oxygen-rich concentration,the knitted structure turns into the honeycomb structure.(4)The PBR value of the oxide film formed by iron oxide is less than 1.During the oxidation process,it is easy to cause the oxide film to not completely cover the surface or the oxide film to be broken,resulting in weak protection of the oxide film.Within the temperature range selected by the experiment and the oxygen-enriched concentration of the combustion air,the isothermal kinetic curve of the billet oxidation conforms to the law of mixed parabolic curve.(5)The parameter values K1 and K2 of the mixed parabolic equation represent the ion diffusion speed in the oxide film and the interface reaction speed between the slab and the gas contact surface.When the heating temperature is increased,the value of K1 increases several times,and the ion diffusion speed in the oxide film increases.When the heating temperature is lower than 1200℃,the range of K1 has a small variation range.When the temperature is increased to 1200℃,the value of K2 increases significantly,and the slab oxidation rate becomes much faster.When the oxygen-rich concentration is increased,the value of K2 increases greatly,and the value of K1 does not change much.