Numerical Simulation Of Charging Of Blast Furnace With Bell-less Top

Under the background of the implementation of the " carbon peaking and carbon neutrality goals" in China,it raises the higher requirements for high efficiency and low carbon smelting of blast furnace.Charging of the blast furnace is the initial phase of the smelting of it and one of the few operations that can directly tune the smelting state of it,which determines the initial burden distribution in the blast furnace.The burden distribution has an important influence on the gas distribution,chemical reaction,shape of the cohensive zone and thermal state in the blast furnace,and its distribution imformation is also the precondition for realizing low carbon smelting and refined operation of the blast furnace.However,because of the high temperature,high pressure,and harsh environment inside the blast furnace,it is difficult to directly measure the information of the burden distribution.The numerical model is widely used in the research of blast furnace charging process because of its economy,convenience and abundant information of charge movement and distribution.At present,the commonly used numerical models mainly include the charging model based on discrete element method(DEM)and the mathematical model of burden distribution based on classical mechanics.DEM can capture the information of micro particle size,but its calculation load is large and it is difficult to give the calculation results quickly.It is difficult to obtain the distribution information inside the material layer by the mathematical model of burden distribution,but it can give the calculation results quickly.The two types of models have their own characteristics and complement each other.The DEM model is used to study the charging process and obtain the movement law of the burden.Some laws that can be converted into mathematical language are applied to the mathematical model for improving its accuracy.Therefore,based on the assumption,the DEM model and the mathematical model of burden distribution are established to study the burden movement and distribution as follows:Firstly,based on the discrete element method(DEM),a three-dimensional model of 1080 m3 blast furnace with serial hopper was established for analyzing the burden movement and.distribution during the charging process of it.In the DEM model,only sinter and pellet were considered for ore,and the friction coefficients of pellet and sinter were calibrated by the experiment of the repose angle.Spherical particle was used to describe the shape of the pellet,and columnar,triangular and hexahedral particles were used to describe the irregular shape of the sinter,Under the condition of comprehensive consideration of calculation efficiency and accuracy,the particle diameter of the sinter and pellet used in the simulation was twice of the actual particle diameter.The mdial and circumferential distribution of the burden in the receiving hopper and lower hopper were calculated,and the discharging sequence of the burden from two hopper was quantitatively analyzed using the DEM model.The burden structure at different discharging stages of the hopper was clarified.The throat region was equally divided in radial and circumferential direction,and the burden structure in each equally region was obtained.The influence of chute structure and parameters on the burden movement and distribution was discussed in detailed.The discharging sequence of the storage bin has an important influence on the burden distribution in the hopper and furnace,and the influence of discharging sequence of the storage bin on the burden distribution was investigated using the model.According to the characteristics of DEM that could track the movement information of each particle,the cuase of circumferential mass segeration of the blast furnace with parallel hoppers was deeply analyzed.Differences between burden trajectoriy and circumferential mass distribution of charging using the circular chute and that using rectangular chute was clarified.The calculated results showed that the relative motion of the burden trjactory on the chute caused by the curcature force and Coriolis force was the main factor of the segregation.Charging using the rectangular chute could effectively reduce the circumferential mass segregation.Effects of the mass flow rate,Y-tube diameter,and chute length on the segregation were discussed.Moreover,the influence of the discharging sequence of the storage bin on the burden distribution in the hopper and furnace was calculated using the model,which provided a guide for the charging operation of the blast furnace.Secondly,a three-dimensional model of 1080 m3 blast furnce with parallel hoppers was established to investigate the burden movement and distribution during charging of the blast furnace.Some informations of the burden,such as the radial and circumferential distribution of the pellet and sinter in the hopper,discharging sequence of the burden at different radial positions in the hopper,burden movement one the chute and in the empty zone,and the radial and circumferential distribution of the burden in the furnace,was calculated and captured using the threedimensional model.Then,the force and movement of single particle during the charging of blast furnace were analyzed,and the mathematical model of burden distribution was established,which included three sub-models:burden trajectory model,burden profile model,and burden descending model.Filling point of the burden on the burden surface were divided into four types,and the relationship between new burden profile and old burden profile was analyzed in detail.The "singular" shape during updating burden surface was simplified,and the calculation accuracy after simplification was discussed.Based on the classification of the filling point.a general algorithm for calculating burden profile was designed,which could calculate the burden profile under any cases.Simulation system of charging of the blast furnace was developed using Visual Basic programming language.The system could quickly calculate the filling point,burden traj ectory,burden profile,and radial ratio of ore to coke.Finaly,based on the simulation system,the influences of some key operation parameters,such as the height of stock line and batch wight,on the burden distribution was analyzed.Correction scheme of the chute angle was given based on the burden trajectory in the furnace to solve the problem of low stock line and avoid the collision between the burden and the furnace wall.The influence of the mass of central coke on the width of central coke path in the furnace was analyzed using the simulation system.The difference of stacking angle between pellet and sinter was considered in the burden profile,and the influence of charging structure on the burden distribution was analyzed by introducing a charging structure coefficient into the burden profile model.Besides,the design of charging matrix was discussed using the simulation system,and the burden distribution under the current charging matrix was predicted to assist the new blast furnace to determine the charging matrix.