Study On Carburization Behavior Of The Hot Metal In The Coke Bed

The main restrictions on the development of blast furnace ironmaking are its long process,high dependence on coke and inadaptability to low-grade and miscellaneous resources.Furthermore,the raw material preparation processes of the blast furnace ironmaking technology,such as coking,sintering and pelletizing,also result in increasingly severe environmental issues.Therefore,the non-blast furnace(NBF)ironmaking technology which uses non-coking coal as energy source has given rise to strong interests of many researchers in the ironmaking industry.Among all NBF ironmaking technologies,the flash ironmaking technology has become outstanding in recent years.Compared with blast furnace ironmaking,the liquid iron carburization in the flash iromnaking is unpredictable.This i5 because in the flash irommaking,there is no solid coke charge which presses the hot metal and thus causes the carburization reaction between the bottom deadman and hot metal.Given the above consideration,a systematic and in-depth study on the mechanism of carburizing behavior of the molten ironformed in the flash ironmaking is necessary.In this paper,the dissolution process of coke in molten iron was simulated in a high temperature resistance furnace at 1550?,and the dissolution kinetics of coke in molten iron was analyzed.The process of molten iron flowing through the eoke bed was simulated through high temperature experiment,and the carburizing process was also investigated.Moreover,a transient three-dimensional numerical model was established based on ANSYS Fluent to simulate the dropping and carburizing behavior of molten iron in the coke bed.The impacts of coke particle size as well as the packed bed height on carbon migration were studied,and the simulated results were compared with the corresponding experimental ones.The main research findings are listed as follows:(l)The value of kt during natural convection was mainly controlled by the mass transfer happening in the liquid boundary layer covering the solid;(2)The composition of coke ash was a key factor that influenced the rate of carbon dissolution.Evident differences existed between the values in kt of different coke samples under the same experimental conditions,with Coke 1(Silicon content was relatively low)of 7.98×10-6 m/s,Coke 2(Silicon content was moderate)of 5.17×10-6 m/s and Coke 3(Silicon content was relatively high)of 3.77×10-6 m/s;(3)The value of ktincreased with the increasing graphitization degree of coke and decreased with the sulfur content in the iron bath;(4)The initial carbon content of molten iron had a great impact on the final iron carbon content.It is important to control this value in a proper range to obtain the required final carbon content,hence ensuring the subsequent hot metal transportation and reducing the consumption of converter smelting;(5)The metallization rate of iron ore had a great influence on the carburizing of molten iron,with FeO content rising from 0%to 4.76%,the value of k,fell from 7.98×10-6 m/s to 5.48×10-6 m/s.,The carburizing process could not develop obviously until the iron ore was reduced in depth and a certain amount of metallic iron was generated;(6)The simulation results based on ANSYS Fluent were consistent with the results of the high temperature experiments,and the relative error was small.Therefore,the present model could predict the transfer behavior of carbon with an acceptable accuracy.