| The blast furnace charging operation is one of the four major systems of blast furnace production,which directly determines the burden surface accumulation shape and indirectly affects the gas flow distribution.Hence,it is of great significance to study the blast furnace charging operation method for blast furnace smelting.Due to the complex motion mechanism of the burden flow and the harsh smelting environment of blast furnace,it is difficult for the existing detection equipment to accurately detect the motion trajectory of the burden flow and the accumulation shape information of the burden surface.In addition,the current blast furnace charging operation is still based on the experience of the operator,which is difficult to ensure that the multi-ring charging operation can obtain the expected burden surface shape.For those reason,the analysis of the factors influencing the motion state of burden flow,the modelling of the burden flow motion trajectory,the modelling of the burden surface accumulation shape,and the setting of charging operation method are studied in this paper,and the active multi-loop charging operation and the recommended multi-loop charging operation are realised.The main research work and innovations of this paper are as follows:(1)The relationship between the charging operation parameters and the burden flow motion state is one of the factors affecting the charging operation.Aiming at the unknown influence mechanism of blast furnace charging operation on burden flow motion state,a numerical model of the blast furnace charging operation is established based on the discrete element method to simulate the burden flow motion behavior under different charging operation parameters.The effect of different charging operation parameters on the velocity and position of the burden flow is ascertained,and the velocity distribution of the burden flow in the chute is explored,which refined the search range of the charging operation parameters setting during the charging operation,and provides a reference for quickly obtaining the optimal charging matrix and realizing the recommended multi-loop charging operation.(2)The existing burden flow motion trajectory model takes the burden flow as a single point,which ignores the influence of burden flow’s position on the burden flow trajectory,and cannot obtain the velocity distribution law and position distribution area of the whole burden flow at the chute end.In view of this,a modeling method of burden flow motion trajectory based on coordinate transformation is proposed.Firstly,a static and dynamic coordinate system that rotates with the chute are established on the blast furnace top to realize the transformation of the burden flow between the two coordinate systems.Secondly,based on the discharge model at the throttle valve,a model for the free fall of the burden flow at the central throat and a collision model between the burden and the chute integrating the normal and tangential recovery coefficients are established to realise the accurate calculation of the initial velocity of the burden flow moving on the chute.Thirdly,the relationship between relative motion,implicated motion and absolute motion based on the classical mechanics is established to reduce the complexity of the force analysis of the burden flow in the chute.Finally,the trajectories of all the burden flow particles leaving from different positions of the throttle valve are aggregated into a burden flow trajectory set,and then the velocity distribution law and position distribution area of the burden flow at the chute end are determined to realize the three-dimensional motion trajectory modeling of the burden flow.(3)Existing burden surface accumulation shape models often rely on a large number of experiments to determine the furthest moving distance of burden flow,which is cumbersome process with low generality.In view of this,a modelling method for the s burden surface accumulation shape based on the motion state of burden flow is proposed.Firstly,the inner and outer trajectories of the burden flow in the blast furnace throat are obtained based on the model of the burden flow motion trajectory,and the initial accumulation point of the burden surface is further determined.Secondly,the motion state of the burden flow at the initial accumulation point is analyzed,and the relationship between the furthest radial distance of the burden and the motion state of the burden flow is established.Thirdly,taking the two straight lines as the basic burden surface accumulation shape and using the principle of volume conservation as a constraint to calculate the burden surface accumulation shape and realize the burden surface accumulation shape modeling of single-ring charging operation.Finally,on the basis of the accumulation shape of the single-ring charging operation,the modeling of the accumulation shape of multi-ring charging operation under a given charging matrix is realized.(4)The active charging operation relies on expert experience to give the charging matrix,but the charging operation is relatively ’rough’ and often results in significant deviations between accumulation shape and expected burden surface shape.In view of this,a recommended multi-ring charging operation method based on the inverse operation of the charging matrix is proposed.Firstly,on the basis of initial burden surface,charging weight and expected burden surface shape,the specific description of expected burden surface shape is obtained according to the principle of volume conservation.Secondly,constrained by the principle of volume conservation,assisted by the mathematical model of the burden flow threedimensional motion trajectory and burden surface accumulation shape,and taking the minimum volume deviation between the burden surface accumulation shape and the expected shape of burden surface as the optimization goal,the optimal charging matrix is solved by inverse operation.Finally,the recommended charging operation is performed based on the obtained optimal charging matrix.In view of the limited inspection means and the difficulty of experimental verification,a scaled geometric model of the blast furnace is established,a charging operating system is developed,and the accuracy of the recommended charging operation method is verified by combining the numerical model of charging operation. |
PDF Full Text Request