Numerical simulation analysis of direct reduction of gas-based shaft furnace
Aiming at the difficulty that the operation degree of the reduction reaction cannot be directly observed dur-ing the direct reduction process of the gas-based shaft furnace,based on the three-interface unreacted nuclear model,a direct reduction model of the gas-based shaft furnace is established under the condition of ignoring the internal tem-perature of the model pellet and assuming that the thermal effect of the pellet reduction reaction completely occurs in the solid phase,and the valence state transformation of iron oxide is numerically simulated and verified.The results show that since the established gas-solid model contains three interfaces,the reaction radius of each interface eventu-ally tends to zero with the stepwise reduction of iron oxides,and the reduction reaction rate increases first and then decreases with the increase of shaft furnace depth.When the pellets descend to a depth of 3 m in the shaft furnace,a FeO reaction interface with a radius of 15 mm appears,where the pellet reduction rate is about 28％.As the pel-lets continue to descend about 2 m in the shaft furnace to a depth of 5 m,the radius of the interface of Fe3O4 decrea-ses to 0,at which point the iron oxide completely transforms into the floatite form,and the pellet reduction rate is a-bout 34％.By changing different process parameters for simulation,it can be found that the metallization rate and reduction rate of the reducing pellet increase with the increase of gas temperature.When the gas temperature increa-ses at 50 ℃ and the reducing gas flow rate increases at a gradient of 5 040 m3/h,the corresponding pellet metalliza-tion rate increases by about 8％and 4％,respectively.In contrast,the metallization rate of the pellets is much more affected by the cutting speed than the gas temperature and reducing gas flow,which is manifested as follows:when the cutting speed increases by 0.02 t/h,the metallization rate decreases by about 0.07％.When the pellet size de-creases,the metallization rate will show an increasing trend,and the pellet size decreases by 1 mm,and the pellet metallization rate increases by 2.23％.
gas based shaft furnacegas based methoddirect reducednumerical simulationreduction ratemetal-lization rate
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