Effect Of High Pellet Ratio On Burden Layer Profile And Gas Flow Distribution In The Lump Zone Of Blast Furnace

Reduction of producing cost and fuel consumption and energy conservation and emissions reduction are essential for the sustainable development of iron and steel enterprises.Compared with the sinter production,the energy consumption of the pellet production process is lower and the environmental pollution emission is less.In addition,the pellet has the characteristics of high grade,uniform size,high strength and good reducibility.Therefore,it is possible to reduce the amount of sinter and improve the gas utilization efficiency with higher pellet charging ratio,and eventually to reduce fuel ratio and achieve the purpose of low-carbon ironmaking.But high pellet charging ratio may give rise to the problems including central aggravation and heel on the furnace wall.Therefore it is necessary to investigate the effect of high pellet ratio of on burden profile and gas flow distribution in the lump zone of blast furnace,and thus providing theoretical basis for the optimization of charging system under high pellet ratio.According to the burden composition and charging system of Baosteel No.2 BF,structure parameters of stock pile under different pellet ratios were measured in the present work,and the burden shape was calculated.Meanwhile by using numerical simulation,the influence of high pellet ratio on gas flow distribution in the lump zone of blast furnace was studied,and the optimization of charging system was recommended on the basic of the calculated results.The following conclusions were made.The voidage and angle of the stock decrease with increment of pellet ratio and thus the burden layers become flat.In the central zone of blast furnace,with the increment of pellet ratio from 20%to 30%and 40%respectively,the O/C ratio(ratio of ore to coke)increases with the reduction of gas flow velocity,and increment of the pressure drop of gas flow.The aggravating trend in the central zone of blast furnace is obvious.While near the wall of blast furnace,the O/C ratio has no obvious change and the velocity of gas flow increases.The development of gas flow near the furnace wall is appreciable.By adjusting the distribution modes of ore and coke,at the central zone of blast furnace,the O/C ratio reduces with increment of gas flow velocity,and reduction of the pressure drop of gas flow.The gas flow at the center of blast furnace is fully developed,and the aggravating trend in the central zone of blast furnace can be controlled.A'Hump' of coke is formed by optimization of coke charging mode which helps in controlling the excessive rolling of pellets towards center.Formation of a flatter ore and coke layer near the wall helps in minimising rolling and the coke pushing effect.The improvement of gas flow distribution is unobvious by deepening the stock line,which is not a recommended as the primary measure under high pellet ratio.