Kinetics And Mechanisms Of Coke And Iron Ore On The Coupling Reaction And Their Evaluating Indexes

Iron ore and coke are the two most important raw materials for blast furnace ironmaking,and their thermal performance directly affects the operation and production efficiency of the blast furnace.Currently,the relationship between the thermal properties of iron ore and coke and the blast furnace smelting process is only measured and guided by the iron ore’s individual reduction index and the coke’s CRI and CSR indexes.However,with the increase in the types of burden materials and the improvement of smelting intensity,the differences between these indexes and the actual state inside the blast furnace have become more apparent.Therefore,this article applies a dynamic analysis method to study the coupled gas-solid reaction mechanism between iron ore and coke inside the blast furnace.Combining the coupled gas-solid reaction experiments of coke and iron ore under different temperature regimes,new indicators for the thermal performance of iron ore and coke are proposed,which can improve the thermal performance information of iron ore and coke inside the blast furnace.The research results are as follows.（1）The reduction kinetics of iron ore was studied using thermogravimetric analysis.The fitting kinetic analysis method with isothermal data and the model-free kinetic analysis method with non-isothermal data were synergistically utilized to further reveal the gas-solid reaction kinetics mechanism between iron ore and carbon monoxide.A novel non-isothermal kinetic analysis method named the“DCCR”（Difference Concentration Change Rate）method was proposed and applied to verify the gas-solid reaction related kinetic parameters under the constant reaction gas concentration program of industrial raw materials.By comparing and analyzing with other methods,it was revealed that the results obtained by the DCCR method showed minor influence from mass and heat transfer,and were more meaningful for industrial reaction processes.（2）Through simulated gas-solid coupled reaction experiments between iron ore and coke in the high-temperature zone of the blast furnace,new thermal performance indicators for evaluating the high-temperature reduction performance of iron ore were proposed.By comparing the new indicators for the direct and indirect reduction thermal performance of iron ore with existing ones,and combining with the Carbon Displacement-Reduction Rate（C-DRR）chart,it was clarified that the high-temperature coupling reduction performance of sintered ore is superior to that of pellet ore.By combining the“Difference Concentration Change Rate”（DCCR）method with the model fitting method,the gas-solid reaction kinetics mechanism and limiting steps of the mineral-coking coupled reaction were elucidated,revealing the essential characteristics of the actual operating state of sintered ore and pellet ore in the high-temperature stage of the blast furnace.（3）Based on the isothermal pre-reduction coupled reaction experiments of the simulated blast furnace softening zone,and by analyzing the data of the coupled reaction between sinter and coke and their respective kinetics,the rate-limiting steps of the gas-solid coupled reaction between sinter and low-reactivity coke was revealed to be the gasification reaction rate of low-reactivity coke.The rate-limiting steps of the gas-solid coupled reaction between sinter and high-reactivity coke were revealed to be the reduction reaction rate of iron ore.（4）By analyzing the coupled reaction mechanism and limiting factors based on kinetic analysis,and in combination with the analysis of coupling factors and microstructure,it was revealed that high CRI（Coke Reactivity Index）and low CSR（Coke Strength after Reaction）coke can be used normally in the blast furnace under the influence of sinter reduction behavior.In addition,new thermal performance indicators for evaluating coke were proposed through simulated isothermal pre-reduction coupled reaction experiments of the blast furnace softening zone,namely the rate of coke dissolution(R_CSL)and coke strength after dissolution(CS_CSL)at different reaction temperatures.