Simulation On Ore Particles Segregation Behavior By DEM In The Charging Process Of Blast Furnace

The segregation behaviors of ore particles during charging process of blast furnace play an important impact on particle distribution in the throat of blast furnace,which affect the normal distribution and utilization of gas flow in blast furnace,thereby affecting the stability of blast furnace conditions,and it is not beneficial to the recovery of iron,effectively.The traditional research methods based on macroscopic physical model experiments and mathematical modeling method cannot reflect the microscopic flow,segregation,pile up and other details at the particle scale accurately,which lead to large deviation between the results from experiment or calculation and that from practical production.Thus,the researchers can hardly understand the flow,segregation laws of ore particles,and cannot grasp the optimization methods of charging.In recent years,with the continuous improvement of computer technology,the numerical simulation based on discrete element method has become an important research tool in the field.This paper presents discrete element method for investigating the segregation behaviors of mineral particles during belt feeding and hopper charging process in a bell-less top blast furnace charging system with the parallel hoppers.The corresponding research results are as follows:(1)There exists an asymmetric shape deviation of material layers between the two hoppers on the central line of a blast furnace during the mono-disperse iron ore particles charge into the parallel hoppers.The material layer distribution deviation of mono-disperse particle can be regarded as the partial distribution behavior of particles in the two hoppers,which is quantitatively characterized by the degree of partial distribution with the definition of partial distribution coefficient ?.The optimized charging mode by adding inner member and optimizing its parameters reduces the partial distribution behavior during the particles charge into the parallel hoppers effectively when its tube diameter D is 12.5 dp,tube length l is 0.6 m and opening angle ? is 64°.(2)In the radial direction,large particles in the upper and small particles in the lower,as the "up and down segregation" structure appears;in the width direction,the large particles are mainly distributed on both two sides,but small particles are mainly distributed in the middle,as the "two sides segregation" structure when the different size iron ore,coke and other materials in the process of belt feeding.To measure the size segregation quantitatively,thesegregation index SI was proposed and defined.Since sinter,raw ore,pellets overall particle size distribution are set as large,medium and small,on the distribution of different types of minerals,in the radial direction,the distribution structure of minerals segregation predominantly emerged that sinter is distributed in the upper,raw ore is distributed in the middle and pellets is distributed in the lower;in the width direction,the distribution structure of minerals segregation emerged that sinter is distributed on both sides,raw ore and pellets are distributed in the middle.In addition,the effect of belt parameters including the belt vibration amplitude,frequency,transport speed and angle on the size and mineral distributions had also been discussed in the feeding processes of both ore and coke particles.(3)When poly-disperse particles are charged into the hoppers from the feed belt,two asymmetric burden flow trajectories on the central line of the blast furnace are formed due to the special structure of the parallel hoppers,which makes different landing positions of burden in the two hoppers.Therefore,there exists different size distribution and different mineral distribution in the two hoppers,resulting in the fluctuations of burden distribution in the blast furnace under subsequent operation,which eventually leads to the fluctuations of gas distribution and low utilization rate in the blast furnace and affects the stable production of the blast furnace.After optimizing the charging mode with the inner member,the particles are charged into two hoppers with the same size and mineral distribution,and the mass distribution of materials are more symmetrical on the central line of the blast furnace.By effectively weakens the deviations of particle size and mineral distribution in the parallel hoppers,it can enhance the operation stability of discharging by hopper-changed.