Non-spherical DEM Modeling Of Blast Furnace Particles And Numerical Simulation Of The Charging Process

The blast furnace(BF)has complex internal mechanisms and many influencing factors,and is a typical "black box" system.Due to the high operating costs and the difficulty of obtaining information,it is difficult to meet the needs of the current research charging process by experimental method.Therefore,numerical simulation studies represented by the discrete element method(DEM)have become an important tool to study the BF charging process.However,the real BF particles have various shapes,and the spherical model widely used in DEM cannot describe the real shape of BF particles,which limits further insight into the BF charging process.Therefore,it is of paramount importance and great demand to explore a non-spherical DEM model that can describe the charging of real BF particles.In this paper,an experimental model of the bell-less BF charging process is built,and the DEM simulation results of non-spherical particle models such as super-ellipsoid,multi-sphere,and polyhedron are compared with experiments to study the charging process.The main research contents and results are as follows:(1)The reliability of the super-ellipsoid model to describe the charging process of nonspherical particles was investigated.In this paper,the super-ellipsoid is modeled according to the shape characteristics and particle size distribution of real particles.The experiments of the hopper discharge process verified the reasonable accuracy of the super-ellipsoid model over the spherical model in terms of reproducing the burden distribution of experimental particles.The charging physics experiment with an equal scale reproduction of real BF was built,and the quantitative analysis of the experimental measurements and simulation results of the BF charging process demonstrates that the super-ellipsoid model can reproduce the flow behavior of the experimental particles provided a suitable shape index is chosen,and increasing the shape index of the superellipsoid model facilitated predicting the burden distribution of the experimental particles.In addition,microscale information such as coordination number,contact force chain,and porosity distribution of the packing structure is analyzed in this paper.(2)The effect of different types of the multi-sphere model on the non-spherical charging process was investigated.In this paper,real particles were modeled in 3D and the multi-sphere model was used to fit the shape of the real particles.The multi-sphere model that controls the volume to be equal to the experimental particles presents a high agreement with the burden distribution of the experimental particles,while the multi-sphere method that controls the outer contour of the multi-sphere to fit the shape of experimental particles cannot reproduce the burden distribution of the experimental particles.On this basis,the influence of the shape fitting accuracy of the multi-sphere model on the simulation accuracy was investigated,and the parameters of the multi-sphere model used to describe the optimum of the real furnace charging were obtained.In addition,improving the fitting accuracy by increasing the number of subspheres can not improve the simulation accuracy,but decreases the computational efficiency.(3)The prediction accuracy of the polyhedron model with different reduction levels for nonspherical charging processes was evaluated.The results show that increasing the face number of the polyhedron model can improve the accuracy of the simulation,including the characteristics of the burden and porosity,but at the expense of significantly reducing the computational efficiency.The polyhedron DEM is used to simulate the industrial-scale BF charging process to investigate the trajectory and width of the charging flow at the furnace top,the drop point and distribution range of the charging,and the burden distribution for single-ring and multi-ring charging,the interlayer percolation,and the porosity distribution.This study also incorporates the spherical particle model with rolling friction to explore the feasibility of predicting polyhedral particle charging behavior.In summary,DEM models based on various non-spherical particle models(super-ellipsoid,multi-sphere,and polyhedron)have been established in this paper to study the BF charging process.By comparing the results of experiments and simulations,the feasibility of multiple non-spherical models for reproducing the charging behavior of BF particles is evaluated.This paper gives particle model solutions to meet different simulation requirements,aimed at providing theoretical support for process optimization of BF charging.